Table of Content

25 February 2020, Volume 41 Issue 4
Food Chemistry
Preparation and Antioxidant Properties of Inclusion Complex of Myricetin with Glucose-β-cyclodextrin
WANG Yibo, FU Xiaofang, YUAN Li, ZHANG Ting, XIN Tingting
2020, 41(4):  1-6.  doi:10.7506/spkx1002-6630-20190104-054
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An inclusion complex of myricetin with glucose-β-cyclodextrin (G-β-CD) was prepared by freeze-drying method and the host-guest interaction was analyzed by the phase solubility method. In addition, the inclusion complex was characterized by infrared spectroscopy (IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetry (TG). The antioxidant activities of myricetin and the inclusion complex were determined by reducing power and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assays. The results showed that the inclusion complex had strong antioxidant capacity, which was increased by 89.13% in reducing power and by 109.12% in DPPH radical scavenging capacity as compared to myricetin at 6 and 10 mmol/L, respectivley. These results showed that myricetin/G-β-CD inclusion complex with inclusion ratio of 1:1 was successfully prepared by freeze-drying method; the inclusion complex had strong antioxidant capacity and water-solubility, and thus could be used as a new food additive.
Effects of Whey Protein Peptides on Oxidation Inhibition and Quality Improvement of Chopped Pork during Repeated Freezing-Thawing
PENG Xinyan, LIU Yuan, HE Hongjun, ZHANG Min, SHAO Lingjian, ZENG Yulong, WANG Xiaoyu
2020, 41(4):  7-14.  doi:10.7506/spkx1002-6630-20190717-230
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The effects of whey protein hydrolysates (WPH) on the oxidation stability and quality of chopped pork during repeated freezing-thawing were examined. Different levels (5%, 10% and 15%) of WPH were added to the pork systems. Changes in thawing loss, total volatile base nitrogen (TVB-N) value, thiobarbituric acid reactive substances (TBARS) value, gel texture, protein carbonyl content, modulus loss and Raman spectrum were evaluated during nine freezing-thawing cycles. The results showed that before freeze-thawing, as far as all tested indexes were concerned there was no signi?cant difference between the treatment and control groups (P > 0.05). Thawing loss was increased from 2.67%?2.93% to 7.00%?12.4% after freeze-thawing cycles. Addition of 15% WPH significantly inhibited the increase in thawing loss and enhanced water-holding capacity (P < 0.05). After 7?9 cycles of freezing-thawing, 15% WPH could significantly inhibit the increase of TVB-N value, TBARS value and protein carbonyl content when compared with the blank control and native whey protein (NWP) groups. Texture profile analysis (TPA) indicated that hardness, springiness, chewiness and cohesiveness were significantly decreased with increasing cycles of freezing-thawing. Chewiness was increased significantly from 9.63 to 17 g with 15% WPH treatment after the 9th cycle, and springiness reached 0.69 after the 5th cycle, exceeding the 0.02% BHA group. The hardness and cohesiveness of both WPH and 0.02% BHA groups were significantly higher than those of the blank group. The TPA parameters could be improved by adding WPH, especially at higher levels. The rheological tests showed that modulus loss (G’’) values were declined with the addition of WPH (P < 0.05). Raman spectroscopic analysis revealed that the addition of WPH inhibited the transformation of α-helices into β-sheets effectively and protected the secondary structures of the protein. In summary, WPH could act as an antioxidant to inhibit oxidation and preserve the quality of chopped pork during repeated freezing-thawing.
Oil-Water Interfacial Properties of Sarcoplasmic Proteins in Meat from Different Animal Species
DU Feifei, WU Changling, FANG Aihu, ZHANG Li, LI Zhen, YANG Zongyun, ZHOU Nan, LI Pengpeng, LI Dianzhao, WANG Peng
2020, 41(4):  15-22.  doi:10.7506/spkx1002-6630-20181022-229
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In order to explain the relationship between the structural properties (such as hydrophobicity and molecular flexibility), dynamic conformational changes during interfacial adsorption and system energy of sarcoplasmic proteins, and more broadly, to understand their functions, sarcoplasmic proteins were extracted from pork, fish and chicken meat and evaluated for amino acid composition, some important physicochemical properties, conformation, emulsifying properties and oil-water interfacial properties. The results showed that chicken sarcoplasmic protein had higher contents of phenylalanine and tyrosine as well as significantly higher particle size and surface hydrophobicity than pork and fish sarcoplasmic proteins (P < 0.05). There was no significant difference in the rate of conformational change within the same time period between pork and chicken sarcoplasmic proteins (P > 0.05), but the rate of conformational change was significantly slower in fish sarcoplasmic protein (P < 0.05). Compared with pork and chicken sarcoplasmic proteins, the interfacial diffusion rate of fish sarcoplasmic protein was significantly higher (P < 0.05) but no significant difference was seen between chicken and pork sarcoplasmic protein (P > 0.05). The emulsifying activity of fish sarcoplasmic protein was significantly lower than that of pork and chicken sarcoplasmic protein (P < 0.05), but the emulsifying activity of pork sarcoplasmic protein was only slightly lower than that of chicken sarcoplasmic protein (P > 0.05). The emulsifying stability of fish sarcoplasmic protein was the lowest among the three sarcoplasmic proteins (P < 0.05). Principal component analysis showed that pork and chicken meat sarcoplasmic proteins had similar properties, which were significantly different from those of fish muscle sarcoplasmic protein. The emulsifying activity and emulsion stability of sarcoplasmic proteins were strongly correlated with the surface hydrophobicity, zeta potential and conformational change rate, and the diffusion rate was strongly correlated with the solubility.
Effects of Macronutrients and pH on Matrix Quality of Emulsion-Type Foods for Special Medical Purposes
LIU Yuan, YE Shengying, WEI Zhencheng, ZHANG Yan, DENG Yuanyuan, TANG Xiaojun, ZHANG Mingwei, LIU Guang
2020, 41(4):  23-31.  doi:10.7506/spkx1002-6630-20181026-315
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The effects of different edible oils, proteins and maltodextrins with different dextrose equivalents (DE) on the appearance and stability of an emulsion which can be used in foods for special medical purposes were investigated by measuring the color, turbidity, rheological properties and centrifugal sedimentation rate of the emulsion. The effect of pH on the properties of the emulsion with optimized levels of three macronutrients was further explored. The results showed that all five oils had little effect on the chromaticity of emulsions. The turbidity and solar reflectance index (SRI) (A800 nm/A400 nm) of soybean oil emulsion were higher than those of the other oil emulsions, but soybean oil emulsion showed lower centrifugal precipitation rate and higher viscosity value, indicating that it was the best choice for the preparation of an emulsion. Whey protein-stabilized emulsion had better color but significantly poorer turbidity, viscosity and centrifugal precipitation rate than sodium caseinate-stabilized emulsion. Among the sodium caseinates tested, CN-EM7-stabilized emulsion showed minimum turbidity and centrifugal sedimentation rate and maximum emulsion viscosity. Additionally, maltodextrins with different DE values exhibited different effects on the quality of emulsions, and maltodextrin DE15-containing emulsion displayed the best appearance acceptance and stability. Furthermore, pH showed a significant effect on the quality of the emulsion. pH in the range of 6.50–7.00 was suitable for the preparation of the emulsion in the present research. The emulsion prepared at pH 7.00 had the highest viscosity and the minimum centrifugal precipitation rate. The most suitable types of three macronutrients and the optimum processing pH were obtained for emulsion preparation, which will provide a theoretical guidance for the industrial development of emulsion-type foods for special medical purposes (FSMP).
Synergistic Effect of Low Ester Pectin Combined with NaCl on Gel Properties of Liquid Whole Egg
WANG Yinan, CHENG Yuan, CHI Yujie
2020, 41(4):  32-40.  doi:10.7506/spkx1002-6630-20181031-368
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In this study, we examined the effects of combined addition of low ester pectin (LEP) and NaCl on improving the gel properties of liquid whole egg. NaCl was added at 0.10% and 0.15% (m/m) and LEP at 0.10%, 0.20%, and 0.30% (m/m). Changes in the gel properties and microstructure of liquid whole egg were investigated, and the underlying mechanism was analyzed on the basis of the changes in physicochemical properties. The results showed that the combined addition of NaCl at 0.10% and LEP had the best synergistic effect on improving gel properties of liquid whole egg. The addition of NaCl and LEP increased negative charges in the system, promoted the formation of soluble protein aggregates, and significantly increased the absolute value of zeta potential, average particle size D4,3 and soluble protein content (P < 0.05). During the gel formation process, the complexation of LEP with egg proteins could enhance the density of the three-dimensional network structure and complexation regions were formed, both of which were helpful to retain free water. The results of rheological and gel properties showed that the elastic modulus (G’), gel strength, water-holding capacity and immobilized water content rose with the increase of LEP content. The best gel properties of liquid whole egg were observed with the addition of 0.10% NaCl and 0.20% LEP, which showed a 2.01-fold increase in hardness, an increase of 30.64% and 16.48% in elasticity and water-holding capacity, respectively, and a 2.50-fold increase in the content of immobilized water, and a lot of tiny pores were found on the gel surface. Therefore, the combined addition of NaCl and LEP can improve gel texture of liquid whole egg, which provides the theoretical basis for expanding the application of liquid whole egg in the food processing field.
Effect of NaOH Pretreatment on Depolymerization and in Vitro Antioxidant Activity of Chardonnay Grape Seed Procyanidins
ZHANG Jie, WANG Wenya, YUAN Qipeng
2020, 41(4):  41-51.  doi:10.7506/spkx1002-6630-20190310-116
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In order to produce in large scale oligomeric procyanidins (OPC) (with polymerization degree (DP) less than 5) that can be absorbed by the body, we studied the effects of NaOH pretreatment on the depolymerization of grape seed procyanidins (PC) and the antioxidant activity in vitro of OPC. The effects of different pretreatment temperatures (40, 60, and 80 ℃), times (15, 30, and 60 min) and NaOH concentrations (0, 1, 2, 4, 6, 8, 10, 15, 20, and 25 mol/L) on the mean degree of polymerization (mDP) of PC, and the composition and content as well as antioxidant activity in vitro of OPC. The results showed that the optimum conditions for generating OPC were as follows: NaOH concentration 10 mol/L and pretreatment at 60 ℃ for 15 min. Compared with the control (pretreated with 0 mol/L NaOH at 60 ℃ for 15 min), the optimized NaOH pretreatment reduced the mDP of PC from 5.39 ± 0.12 to 1.30 ± 0.014, increased the total area of OPC by 8.28 times and OPC content by 6.42 times, and enhanced in vitro scavenging capacity against 1,1-diphenyl-2-picrylhydrazyl hydrate (DPPH) and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radicals and ferric reducing antioxidant power (FRAP) by 4.22, 5.13 and 3.84 times, respectively. In summary, this study provides a novel way of producing OPC, which could facilitate the high value-added utilization of grape seeds.
Effect of Modified Soybean Phospholipids on Structural and Physicochemical Properties of Soybean Flour
WANG Xibo, LIANG Yaru, YANG Shuo, GUO Zengwang, JIANG Lianzhou, FAN Zhijun, WANG Zhongjiang, TENG Fei, LI Yang,
2020, 41(4):  52-58.  doi:10.7506/spkx1002-6630-20181228-333
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In this paper, the effect of addition of modified soybean phospholipids on structural properties (particle size and specific surface area, scanning electron microscopic (SEM) structure, particle size distribution, and optical microscopic changes), physicochemical properties (dispersibility, wettability, precipitation coefficient, bulk density, dry matter solubility index (DSI), emulsifying activity, and emulsifying stability) and sensory properties of soybean flour prepared from soybean hydrolysate from aqueous enzymatic extraction of soybean oil was examined. The results showed that the average particle size of soybean flour with 0.6% modified soybean phospholipids was small, and the specific surface area was large; small particles were observed in the microstructure with some of them being shrunken. Its solution exhibited a uniform particle size and droplet dispersion and was stable, which indicated that the addition of modified soybean phospholipids could significantly affect the structural properties of soybean flour. The addition of 0.6% modified soybean phospholipids decreased wetting time by 24.5 s, dispersion time 30 s, precipitation coefficient by 0.008 and bulk density by 0.16 g/mL and increased DSI by 12.87% when compared with the blank control, thus significantly improving the physicochemical properties of soybean flour. The findings of this study provide a basis for the development and utilization of soybean flour from soybean hydrolysate from aqueous enzymatic extraction of soybean oil and for the production and application of modified soybean phospholipids in the soybean processing industry.
Preparation, Structure and in Vitro Digestibility of Zinc-Chelating Mung Bean peptide
FU Tianxin, ZHANG Shu, SHENG Yanan, FENG Yuchao, WANG Changyuan
2020, 41(4):  59-66.  doi:10.7506/spkx1002-6630-20190710-137
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In order to produce zinc supplements that can be easily digested and absorbed by the human body and to increase the added value of mung beans, zinc-chelating mung bean peptide was prepared in this experiment. Based on chelation efficiency, one-factor-at-a-time method and response surface methodology were jointly used to optimize the chelation process. Infrared spectroscopy, ultraviolet spectroscopy, scanning electron microscopy and X-ray diffraction analysis were used to compare the changes in the peptide before and after chelation; and the bioavailability of zinc ions in the peptide-zinc chelate was determined by in vitro simulated gastrointestinal digestion. The results showed that the optimal preparation conditions that provided maximum chelation efficiency of 52.19 mg/g were as follows: mass ratio of peptide to zinc 6.20:1, reaction temperature 50 ℃, reaction time 83 min, and pH 6.3. Spectroscopic analysis showed that the amino, carboxyl and amide groups of the peptide were involved in the reaction. Moreover, scanning electron microscopy and X-ray showed that the peptide and the chelate differed greatly in surface microstructure and crystallinity. In addition, in vitro simulated gastrointestinal digestion studies showed that the dialysis rate and solubility of zinc ions in the zinc-peptide chelate were significantly higher than those of inorganic zinc salts. To conclude, the new type of chelate has a great application potential due to the high bioavailability of zinc ions.
Effect of Industrial Modifications on Soybean Protein Structure and the Texture and Microstructure of Soybean Protein-Myofibrillar Protein Hybrid Gels
JIA Zixuan, RAN Anqi, LIU Jishan, LI Yang, WANG Zhongjiang, JIANG Lianzhou
2020, 41(4):  67-73.  doi:10.7506/spkx1002-6630-20190306-076
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In this study, four industrial modification methods including heat treatment, alkali treatment, glycosylation and oxidation were applied to modify soybean protein isolate (SPI) to investigate their effects on the structure of SPI. The texture and microstructure of the hybrid gels of the modified soybean protein and myofibrillar protein (MP) were further investigated. The results showed that the four industrial modifications did not have a significant effect on the subunit composition of SPI, but they reduced the contents of α-helix and random coil structures and increased the contents of β-sheet and β-turn. Industrial oxidation significantly reduced the disulfide bond content of SPI, while the other treatments significantly increased the disulfide bond content and reduced the free sulfhydryl group content of SPI (P < 0.05); all four treatments changed the disulfide bond configuration of SPI. Tyrosine residues of SPI modified by each method tended to be exposed outside, and tryptophan residues were buried inside after oxidation but were exposed outside after the other modifications. The texture characteristics of SPI-MP hybrid gel showed that the hardness, elasticity, adhesion, and chewiness of the hybrid gels with heat, alkali and glycosylation modification were significantly better than those of the control SPI (P < 0.05). All texture characteristics except cohesiveness of the hybrid gel with oxidized SPI were poorer than those of the control SPI. Under scanning electron microscopy, it was seen that the oxidized SPI-MP hybrid gel was rough and porous, while the hybrid gels with the other industrial modifications were more dense and uniform.
Effect of Pea Protein on Quality Properties and Microstructure of Heat-Induced Gel of Chicken Batter
JI Hongfang, LI Shasha, ZHANG Lingwen, WANG Xuefei, KANG Zhuangli, CHEN Fusheng, MA Hanjun
2020, 41(4):  74-79.  doi:10.7506/spkx1002-6630-20181229-359
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In order to improve the gel properties of chicken batter, we investigated the effect of pea protein on the gel color, cooking yield, water-holding capacity, texture, dynamic rheology, microstructure, and water distribution and migration. Results indicated that with increasing the amount of pea protein addition, both L* and a* value decreased, while b* value rose. The cooking yield increased continuously except for no difference between those at addition levels of 8% and 12% (P > 0.05). The addition of pea protein significantly enhanced the relative proportion of immobilized water and reduced the T21 relaxation time (P < 0.05); it increased water-holding capacity, resulted in a continuous increase in hardness and chewiness as well as an initial increase followed by a decrease in springiness and resilience. Initial and final values of storage modulus (G’) increased with the addition of pea protein (P < 0.05). The optimum addition level of pea protein that provided maximum water-holding capacity (96.63%), springiness (0.892) and resilience (0.288) was determined to be 8%. At this addition level, the gel quality was achieved as indicated by the homogenous, compact and ordered gel network structure formed.
Effect of Chlorogenic Acid on Qualities of Grass Carp Processed by Different Cooking Methods
LI Junke, SUN Xuemei, LIU Quanwen, TAN Xiaomian
2020, 41(4):  80-85.  doi:10.7506/spkx1002-6630-20190715-196
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In the present experiment, we investigated the effects of cooking method and chlorogenic acid on the quality of grass carp. Four cooking methods were evaluated namely, roasting, pan-frying, deep-fat frying and grilling. Chlorogenic acid was added at levels of 0.015%, 0.030% and 0.045%. Changes in the texture, color, cooking loss, heterocyclic amine formation of fish patties were determined. The results showed that addition of chlorogenic acid significantly increased hardness and elasticity (P < 0.05), but had no significant effect on chewiness (P > 0.05), and reduced cooking loss. It resulted in a decrease in L* and a* value and an increase in b* (P < 0.05). Deep-fat frying could improve the quality of grass carp meat most obviously among these cooking methods. Compared to the control group, the incorporation of chlorogenic acid significantly decreased the content of heterocyclic amines (HCAs) (P < 0.05). The inhibitory rate was higher than 50% with the addition of 0.015% chlorogenic acid and it increased up to 94.85% at an addition level of 0.045%. These results suggested chlorogenic acid addition could evidently inhibit the formation of HCAs in grass carp meat during high-temperature cooking, improve the color and texture, and decrease cooking loss, which provides a theoretical basis for improving the quality of processed foods.
Influence of Modified Potato Starch on Gelation Properties of Myofibrillar Protein
ZHOU Fengchao, LIN Guorong, WANG Xiumei, ZHANG Lifen, LIN Dahe, LIN Shoukai, CHEN Weijiao
2020, 41(4):  86-95.  doi:10.7506/spkx1002-6630-20190115-172
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The properties of composite gels of myofibrillar protein (MP) with native potato starch (NPS), oxidized potato starch (OPS) with 0.2% and 2% oxidant, heat moisture treated potato starch (HMTPS), and heat pressure treated potato starch (HPTPS), designated as NPS-MP, 0.2% OPS-MP, 2.0% OPS-MP, HMTPS-MP and HPTPS-MP, respectively were investigated. The results of rheological properties and low field nuclear magnetic resonance (LF-NMR) demonstrated that 0.2% OPS-MP had the highest storage modulus (G’) and the most stable water distribution, followed by NPS-MP, HMTPS-MP, 2.0% OPS-MP, and HPTPS-MP. The maximum values of gel strength and water holding capacity were recorded for 0.2% OPS-MP (P < 0.05), while the gel strength and water holding capacity of 2.0% OPS-MP and HPTPS-MP were determined to be relatively lower. The main intermolecular forces within the composite gels were hydrogen bonds and hydrophobic interactions, while disulfide bonds played a minor role. These intermolecular interactions were significantly enhanced with increasing starch content, and hydrogen bonds in 0.2% OPS-MP were significantly higher than in NPS-MP (P < 0.05). Microstructure observation showed that 0.2% OPS-MP were more compact and smooth and had a more uniform gel network structure as compared tothe other composite gels.
Metatranscriptomic Analysis of the Microbial Community in Soybean Paste, a Traditional Chinese Fermented Condiment
AN Feiyu, WU Junrui, YOU Shengbo, XIE Mengxi, CHEN Xu, ZHAO Yue, BAO Haiyan, WU Rina
2020, 41(4):  96-101.  doi:10.7506/spkx1002-6630-20181210-126
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In the present study, we used metatranscriptomics to comparatively analyze the structure and function of the living bacterial community in naturally fermented soybean paste in the early and late stages of fermentation. We established that the purity and yield of extracted RNA could be increased by discarding the supernatant after centrifugation at 8 000 r/min for 5 min at 4 ℃ in the sample pretreatment procedure. High-throughput sequencing results showed that bacteria played a leading role in the fermentation of soybean paste, with the dominant genera being Tetragenococcus and Lactobacillus. Fungi were abundant only in the early stage of fermentation, and their abundance was low at the end of fermentation. The function of the bacterial community was mainly concentrated on the metabolism of carbohydrates and amino acids, and most of them were enriched at the end of fermentation. The results at the species and functional levels were consistent with each other. In summary, this study provides a new method and technical support for selecting excellent strains for the fermentation of soybean paste and for identifying the microorganisms that really play a role in the fermentation process.
Comparative Evaluation of DNA Extraction Methods for Detection of Transgenic Soybean Protein and Analysis of lectin Gene Degradation during Soybean Protein Extraction
DU Yan, CHEN Fusheng, CHEN Chen, LIU Ying
2020, 41(4):  102-111.  doi:10.7506/spkx1002-6630-20190702-020
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In this paper, six methods of DNA extraction, namely Macherey-Nagel Nucleo Spin Kit (Nucleo kit), Wizard Genomic DNA Purification Kit (Wizard kit), Dneasy Plant Mini Kit (Dneasy kit), Ezup column plant genomic DNA extraction kit (Ezup kit), Dzup genomic DNA extraction kit (Dzup kit) and sodium dodecyl sulfate (SDS) method, were comparatively applied to extract DNA from soybean protein extracts and soybean seeds. The DNA concentration, purity and integrity were determined by ultraviolet spectrophotometry, agarose gel electrophoresis and real-time fluorescent PCR, and the reaction sensitivity was evaluated. We aimed to find the optimum method to extract DNA from soybean protein isolate (SPI), soybean protein concentrate (SPC) and soybean seeds so as to improve the sensitivity and accuracy of transgenic soybean detection. Results showed that the purity and integrity of DNA extracted with Nucleo kit and Dneasy kit were high enough for real-time PCR detection. The purity of DNA obtained by Dneasy kit was the highest, being beneficial for improving the repeatability, stability and accuracy of subsequent PCR reaction, so that Dneasy kit was applicable to SPI, SPC and soybean seeds. The extraction efficiencies of Ezup kit and SDS method were moderate. SDS method costed the least but took the longest time. Despite the high yield, the DNA obtained with Dzup kit was fragmentary and contained lots of impurities, which could limit the applicability of Dzup kit for DNA extraction for transgenic soybean detection. Furthermore, the lectin gene was inferred to be degraded during SPI and SPC preparation with Dneasy kit.
Bacterial Diversity of Xiangyang Pickled Kohlrabi during Fermentation
WU Jinju, LI Yu’ang, WANG Zihang, ZHENG Tingting, YU Bo, YU Haizhong
2020, 41(4):  112-117.  doi:10.7506/spkx1002-6630-20190111-138
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Illumina-MiSeq high-throughput sequencing technology was used to study the dynamic changes of bacterial diversity and community structure during the industrial fermentation of Xiangyang pickled kohlrabi. The results showed that a total of 482 species in 293 genera in 133 families in 67 orders in 32 classes in 19 phyla with 658 operational taxonomic units (OTUs) were detected in 24 samples of pickle juice. During the whole fermentation process, at the phylum level, both Proteobacteria and Firmicutes were dominant, and their relative abundances were 26.14%–78.12% and 8.33%–70.12%, respectively. At the genus level, the dominant bacteria were Halanaerobium, Vibrio, Halomonas, Lactobacillus and Chromohalobacter. Through cluster analysis and principal component analysis, it was found that the 24 samples could be divided into two clusters according to the characteristics of bacterial community structure; and the fermentation process could be divided into early and late stages. This study revealed the dynamic succession of bacterial community structure during the fermentation process of Xiangyang kohlrabi, which may provide a research basis for the improvement of kohlrabi production in the future.
Sequence Analysis of an Endogenous Plasmid in Lactobacillus plantarum and Construction of a Shuttle Expression Vector Using It
FANG Laishan, LAI Qiang, ZHONG Zemin, HUANG Yumao
2020, 41(4):  118-124.  doi:10.7506/spkx1002-6630-20181130-361
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Objective: In order to construct an expression vector for Lactobacillus plantarum, a plasmid carried by the strain was subjected to sequence determination and functional analysis, and an expression system was constructed by using the plasmid system. Through this study, we aim to make a positive contribution to the preparation of oral lactic acid bacterial vaccines. Methods: The plasmid (pLP3) was extracted from L. plantarum LP3, sequenced and subjected to functional analysis. An Escherichia coli/Lactobacillus shuttle vector was constructed based on the replicon of pLP3, the chloramphenicol resistance gene from pSCPSP as a selection marker and the replicon of pUC19. Furthermore, an expression vector D-pLP3-PslpA was developed from the shuttle vector incorporated with the promoter PslpA of S-layer protein from Lactobacillus acidophilus and the gene green fluorescent protein (eGFP) as a reporter gene in L. plantarum. Results: pLP3 was a cryptic plasmid in L. plantarum LP3, isolated from traditional fermented sauerkraut. The size of pLP3 was 2 017 bp and its GC content was 37.48%. Based on the backbone of pLP3, we successfully constructed the shuttle vector D-pLP3 and electroporated it into several strains of lactic acid bacteria. The transformation efficiencies ranged from 0.3 × 102 to 1.0 × 103 CFU/μg DNA. eGFP was expressed successfully in L. plantarum. Conclusion: The expression vector D-pLP3-PslpA possesses the potential to be used as a molecular tool for heterologous gene cloning and expression in Lactobacillus.
Dynamic Succession of Bacterial Community Structure during the Fermentation Process of Zhejiang Rosy Vinegar Analyzed by High Throughput Sequencing
FANG Guanyu, HUANG Bingwen, JIANG Yujian
2020, 41(4):  125-133.  doi:10.7506/spkx1002-6630-20190119-234
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In this study, Illumina MiSeq high-throughput sequencing was used to sequence the V4 region of the bacterial 16S rRNA gene in Zhejiang rosy vinegar at different fermentation times. Analysis of the bacterial community showed that Proteobacteria and Firmicutes were the predominant bacterial phyla during the fermentation process of Zhejiang rosy vinegar. Their relative abundances were always above 98%. The relative abundance of Proteobacteria continued to increase while that of Firmicutes continued to decrease. Acetobacter and Lactobacillus were the main bacterial genera and the relative abundance of Acetobacter showed a continuous increasing trend while that of Lactobacillus showed a declining trend. The relative abundances of Enterococcus, Pseudomonas and Bacillus were low but detectable during the whole fermentation process. There was a significant difference in the bacterial community composition between the early and late stages of fermentation. Four strains of L. paracasei, one strain of L. sakei, one strain of L. rhamnosus and one strain of L. casei were isolated and identified during the fermentation process. By comparing the bacterial community composition of Zhejiang rosy vinegar with that of other vinegars during the fermentation process, we found that the highly abundant bacteria were Acetobacter and Lactobacillus for all vinegars whereas the composition of lowly abundant bacteria was quite different.
Analysis of Microbial Community Diversity of Crab Paste by High-Throughput Sequencing
LI Cheng, KONG Xiaoxue, YU Jubo, ZOU Xiaoqian, LUO Haibo
2020, 41(4):  134-139.  doi:10.7506/spkx1002-6630-20180920-233
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In order to explore the microbial community structure of crab paste stored at different temperatures, the microbial diversity before and after 3 days of storage at –20 or 4 ℃ were investigated by using Illumina MiSeq high-throughput sequencing technique. The results showed that a total of 18 and 26 genera of microorganisms from crab paste samples stored at -20 ℃ for 3 days, as well as 16 and 19 genera from those stored at 4 ℃ for 3 days were obtained through amplification of the 16S rRNA V1-V3 and V3-V4 regions, respectively. The main genera with relative abundance over 1% were Carnobacterium, Jeotgalibaca, Brochothrix, Staphylococcus, Psychrobacter and Vibrio. The dominant genera at –20 ℃ were Carnobacterium (V1-V3, 68.81%; V3-V4, 69.29%) and Vibrio (V1-V3, 16.75%; V3-V4, 14.39%). The dominant genera at 4 ℃ were Carnobacterium (V1-V3, 73.37%; V3-V4, 70.35%), Jeotgalibaca (V1-V3, 11.82%; V3-V4, 12.35%) and Staphylococcus (V1-V3, 5.45%; V3-V4, 5.01%). Meanwhile, the relative abundances of Jeotgalibaca and Staphylococcus at 4 ℃ were markedly higher than those at –20 ℃. These results indicated that the microbial diversity, dominant genera and their abundances in crab paste varied significantly with storage temperature (P < 0.05). This study provides a theoretical basis for the prevention and control of foodborne diseases caused by pickled raw crab paste.
Component Analysis
Analysis of Volatile Compounds in “XihuLongjing” Tea by Stir Bar Sorptive Extraction Combine with Gas Chromatography-Mass Spectrometry
WANG Mengqi, ZHU Yin, ZHANG Yue, SHI Jiang, LIN Zhi, Lü Haipeng
2020, 41(4):  140-148.  doi:10.7506/spkx1002-6630-20190325-322
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In this study, stir bar sorptive extraction (SBSE) combined with gas chromatography-mass spectrometry (GC-MS) was used to analyze the volatile compounds of “XihuLongjing” tea. SBSE parameters including stir bar type, extraction temperature, extraction time, tea-to-water ratio, agitation rate and ionic strength were optimized by one-factor-at-a-time and orthogonal array design methods in order to establish the SBSE-GC-MS method. The overall accuracy of the experiment was satisfactory (recoveries of 115.11% and 108.99% at high and low spiked concentration levels, respectively) and the relative standard deviation (RSD) for repeatability was 8.23% (n = 5). The results showed that the volatile aroma compounds could be extracted and adsorbed to the greatest extent under the following conditions: using polydimethyl siloxane (PDMS) twister as an extraction medium, tea-to-water ratio 60:1 (mg/mL), NaCl concentration 5%, hot water temperature 80 ℃, extraction time 90 min, and agitation rate 1 250 r/min. When representative “XihuLongjing” tea samples were analyzed by the SBSE-GC-MS method, a total of 173 volatile compounds were identified, including 3 enols, 11 alkenes, 37 alkanes, 15 aldehydes, 4 olefine aldehydes, 2 ethers, 17 alcohols, 22 esters, 5 lactones, 9 allyl esters, 5 ketones, 16 ketones, 3 organic acids, 3 sulphur compounds, and 3 nitrogen heterocyclic compounds, 3 oxygen heterocyclic compounds, and 15 aromatic hydrocarbons. Eventually, we concluded that the volatile aroma compounds in “XihuLongjing” tea could be extracted well by SBSE.
Comparison of Lipid Compositions of Several Dairy Products
WENG Chen, DENG Zeyuan, LI Jing
2020, 41(4):  149-156.  doi:10.7506/spkx1002-6630-20190403-046
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In this study, we extracted lipids from seven commercially available dairy products by dichloromethane-methanol method, separated triglycerides and phospholipids from the extract by solid phase extraction (SPE) on an aminopropyl-silica gel column, and hydrolyzed triglycerides by pancreatic lipase to obtain Sn-2 monoglyceride. Then, we analyzed the fatty acid content and position distribution of triglycerides and phospholipids by gas chromatography (GC), and determined the cholesterol content by liquid chromatography (LC). Furthermore, we comparatively analyzed the lipid profile characteristics of the dairy products. Results showed that family nutrition milk powder and milk powder for middle aged and elderly people were similar to each other in fatty acid composition and content. Palmitic acid was mainly combined at the Sn-1,3 position of triglyceride in 6- to 12-month-old infant formula, but mainly combined at the Sn-2 position in family nutrition milk powder and milk powder for middle aged and elderly people. Fermentation of milk led to an increase in the content of conjugated linoleic acid and trans fatty acids and a decrease in the content of short-chain fatty acids. Cholesterol content was positively correlated with fat content in pure milk, yogurt and cheese. The contents of polyunsaturated fatty acids and conjugated linoleic acid in goat milk were higher than those in cow milk.
Effects of Shading Treatment on Occumulation of Anthocyanin in Grape Fruit of ‘Cabernet Sauvignon’ at Harvest
ZHANG Zhenzhen, LI Qian, DONG Rong, QIAO Dan, YAN Xue, ZHANG Ke
2020, 41(4):  157-163.  doi:10.7506/spkx1002-6630-20190310-115
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In this paper, Cabernet Sauvignon grapevines during two growth stages: from the beginning of veraison to full maturation (I), and from full veraison to full maturation (II) were shaded with 50% and 20% shading nets. Normal growth conditions were considered as the control. Changes in the composition and contents of anthocyanins in grape skins at maturity were determined by high performance liquid chromatography-mass spectrometry (HPLC-MS). The experimental results showed that a total of 15 anthocyanins were detected in the 20% shading net group during stage I, while 14 anthocyanins were detected in each of the other four treatments. Pe-coumaroylglucoside (cis or trans) was not detected. The total amount of anthocyanins in the shading treatments was higher than that in the control, but methylated anthocyanins were still the main anthocyanins, and the 50% shading net significantly increased the content of methylated anthocyanins during stage II. With the shading treatments, the composition of anthocyanins was changed: the 20% shading net significantly improved the content of coumarin-modified anthocyanins during stage I and increased the content of acetylated anthocyanins during both stages. The four shading treatments significantly reduced the content of Dp-coumaroylglucoside in both cis and trans. During stage I, the ratio of 3’-methyl anthocyanin acetylated glucoside to total anthocyanins was increased; during stage II, the proportions of cyanidin-O-glucoside and peonidin-O-glucoside were significantly lower than in the control group.
Aroma Release from Stewed Pork with Brown Sauce during Oral Processing
LIU Dengyong, CAO Zhenxia
2020, 41(4):  164-171.  doi:10.7506/spkx1002-6630-20190228-234
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This paper explores the release pattern of aroma from stewed pork with brown sauce at different oral processing stages. A panel of four subjects was selected and trained to freely chew the samples. Breath gas samples were collected using Tedlar? bags at different oral processing stages for qualitative and quantitative analysis of volatile organic compounds by solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS). The correlation between the total amount of aroma release and chewing parameters was analyzed, and the pre- and post-swallow distribution of aroma release were compared with each other. Results showed that the aroma release curves (from both a panel and individual perspective) always dynamically changed during oral processing, with an inter-individual difference being observed. Correlation analysis showed that there was a significantly positive correlation between chewing time (r = 0.910, P < 0.01) and the number of chewing cycles (r = 0.851, P < 0.01) and the amount of aroma release. Moreover, the ratio of aroma release was larger at the pre-swallow stage than at the post-swallow stage. The release of three major volatiles with different hydrophobicity (lgP values) were analyzed at the pre-swallow and post-swallow stages, and it turned out that the higher the hydrophobicity of volatiles, the higher the release of aroma at the post-swallow stage. The use of Tedlar? bags combined with SPME-GC-MS provided a novel method for qualitative and quantitative analysis of breath gas from foods during oral processing. This study provides a methodological foundation for the study of the release kinetics of food aromas.
Changes in Aroma Ester Compounds Contents and Related Enzyme Activities during Drying of Strawberry
ZHANG Lihui, WANG Chao, LIAO Li, AN Kejing, HU Jianzhong, QIAO Yu
2020, 41(4):  172-177.  doi:10.7506/spkx1002-6630-20190318-226
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The changes in aroma ester compounds contents and in strawberry slices during drying were analyzed by headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). Enzymatic activities related to ester compounds were also studied. The results showed that esters such as ethyl caproate, octyl acetate, ethyl octyl caprylate and ethyl decanoate, were formed during the process of strawberry drying. Principal component analysis (PCA) showed that the synthetic score of ester aroma compounds in strawberry slices dried for 15 hours was the highest. Correlation analysis showed that ethanol dehydrogenase was positively correlated with the contents of ethyl esters of some acids, octyl acetate, (S)-3-hydroxybutyrate methyl ester and other aroma ester compounds. There was a significantly positive correlation between alkyl transferase activity and the contents of some acetate esters, methyl caproate and ethyl octanate. Lipoxygenase was positively correlated with the contents of octyl acetate, hexyl acetate, methyl caproate, ethyl butyrate, ethyl decanoate and butyl octylide.
Comparison of Volatile Components from Flos Lonicerae Extracted by Headspace Solid Phase Microextraction and Steam Distillation
ZHANG Pengyun, GUAN Wei, LI Rong, LONG Chunxia, LU Junwen, LIN Shumian, ZHANG Feng
2020, 41(4):  178-184.  doi:10.7506/spkx1002-6630-20181029-343
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The conditions for extracting volatile components from Flos Lonicerae by headspace solid-phase microextraction (HS-SPME) were optimized by one-factor-at-a-time and orthogonal array design methods. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOF MS) were used to detect the extracts obtained by HS-SPME and steam distillation (SD). The results showed that the optimum conditions of HS-SPME were as follows: extraction temperature 60 ℃, equilibrium time 25 min, extraction time 60 min, and desorption time 5 min. Under these conditions, 59 components were identified, accounting for 97.17% of the total amount, and the main components extracted by HS-SPME were terpenes, alcohols and aldehydes; a total of 68 components were identified from the SD extract, accounting for 91.69% of the total amount, with alcohols, aldehydes and ketones being dominant. Accordingly, the types and contents of volatile oil components extracted by the two methods were quite different. This study provides a scientific basis for quality identification, development and utilization of Flos Lonicerae.
Effect of Bagging on Aroma Volatiles and Related Gene Expression in ‘Ruixue’ Apple Fruit
FENG Shuaishuai, YAN Chengtai, ZHANG Tianhao, ZHANG Li, JI Miaomiao, WANG Fan, GAO Hua
2020, 41(4):  185-192.  doi:10.7506/spkx1002-6630-20190320-253
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The aroma components of bagged and non-bagged ‘Ruixue’ apples picked on day 165, 180, 195 and 210 after full bloom were analyzed by head-space solid-phase micro extraction gas chromatography-mass spectrometry (HS-SPME-GC-MS), and their ethylene contents were determined by gas chromatography (GC). Besides, the expression levels of the genes associated with the synthesis of aroma and ethylene were analyzed by qRT-PCR assay. A total of 68 aroma components were detected in the apples, among which, 46 were found to be present in bagged apples and 62 in non-bagged apples. The aldehyde content in the bagged fruit was significantly higher than that in the un-bagged fruit, while the contents of ester and olefins were significantly lower than those in the un-bagged fruit. The level of ethylene receptor gene expression was significantly down-regulated in the bagged fruit, and the content of ethylene was lower than that in the un-bagged fruit. The expression levels of the genes encoding lipoxygenase (LOX) and alcohol dehydrogenase (ADH) were significantly down-regulated in the bagged fruit. Our results implied that the reduction of ethylene synthesis in the bagged fruit resulted in the down-regulated expression of MdLOX and MdADH genes, affecting the synthesis of aroma components and consequently the flavor quality of apple fruit.
Analysis of Carotenoids as Aroma Precursors in Different Varieties of Tea Leaves by High Performance Liquid Chromatography with Photodiode Array Detection
CHEN Li, KUN Jirui, WANG Jing, TONG Huarong
2020, 41(4):  193-198.  doi:10.7506/spkx1002-6630-20190318-227
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In this experiment, the kinds and amounts of carotenoids in 37 different varieties of tea leaves were analyzed and compared by using high performance liquid chromatography with photodiode array detection (HPLC-PDA). A total of 15 carotenoid components were detected. Total amounts in all varieties were 524.6–1 236.7 μg/g, averaging at (863.7 ± 13.5) μg/g; the oolong tea varieties contained the highest amount of carotenoids whereas the lowest amount was observed in the green tea varieties. For all the varieties, lutein was the most abundant carotenoid, followed by quercetin, neoxanthin, β-carotene and zeaxanthin. Principal component analysis showed that the 37 varieties could be divided into three categories: oolong tea, black tea and other varieties. Among them, the oolong tea varieties contained the highest amount of total carotenoids while the black tea varieties contained higher amounts of epoxidized zeaxanthin and zeaxanthin than did any other varieties. The results showed that the contents of carotenoids in tea leaves for different tea varieties were significantly different while tea leaves for the same tea variety had the same carotenoid profile.
Effect of Cold Macerationon the Flavor of Dry White Wine Made from ‘Guankou’ Grapes
ZHU Yanxia, YANG Jiahui, WANG Shasha, SU Yingyue, CHANG Yuan, YANG Zhigang, YUAN Chunlong
2020, 41(4):  199-206.  doi:10.7506/spkx1002-6630-20190312-150
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This study aimed to examine the effect of pre-fermentative cold maceration (PCM) on the flavor of dry white wine made from ‘Gangkou’ grapes and to investigate the relationship between its bitterness and chemical indicators. The physicochemical properties as well as phenolics, aroma and other flavor compositions of wines with different PCM times (12, 24, and 48 h) were analyzed in comparison with wine produced by the traditional process. Bitterness quantification and sensory evaluation were also carried out. The results showed that PCM could increase the contents of phenolics, aroma components, higher alcohols and esters, but excessive duration of PCM significantly reduced the contents of these substances. PCM resulted in increased contents of fatty acids and reduced terpene contents. PCM decreased the total amount of aroma substances and the?effect?was?more?pronounced?with increasing PCM time. The correlation analysis showed that the substances that had a great influence on bitterness were flavonoids, catechins, quercetin, caffeic acid, syringic acid, coumaric acid, ferulic acid, histidine and arginine. Sensory analysis found that PCM improved the taste quality of dry white wine, and the overall quality of wine sample with 24 h PCM was the highest.
Comparative Lipidomic Analysis of Human, Bovine and Caprine Milk
ZHANG Hongda, WANG Lina, ZHANG Yu, LI Xiaodong, LENG Youbin, GONG Yanni, JIANG Shilong
2020, 41(4):  207-213.  doi:10.7506/spkx1002-6630-20181218-203
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In this study, the total lipid components of human, bovine and caprine milk were quantitatively analyzed based on ultra-high performance liquid chromatography-quadrupole-time of flight-mass spectrum. A total of 17 phosphatidylcholines (PC), 11 ceramides (Cer), 15 sphingomyelins (SM), 3 hexosylceramides (HexCer), 32 diglycerides (DG) and 25 triglycerides (TG) were detected in all samples. There were 36 lipid components that significantly differed between human and bovine milk, and 14 lipid components were found to significantly differ between human and caprine milk (P < 0.05). The results showed that the polar lipid content of human milk (1 462.99 μg/mL) was significantly lower than that of caprine milk but higher than that of bovine milk (P < 0.05). In human and bovine milk, the contents of various polar lipids were ranked as: SM > Cer > PC > HexCer, while in the decreasing order for caprine milk was Cer > SM > HexCer > PC. SM was the main class of polar lipids that showed a significant difference between human and bovine milk. The contents of SM (d14:0/20:0) and SM (d15:0/24:1) (15.90 and 16.55 μg/mL, respectively) were significantly higher in human milk than in bovine milk (P < 0.05), while there was no significant difference between caprine milk and human milk except for PC (26:0/0:0). The content of neutral lipids in human milk (47 749.40 μg/mL) was significantly higher than that in bovine and caprine milk (P < 0.05). The main neutral lipids that significantly differed between human milk and bovine and caprine milk were triglycerides. In particular, the contents of TG (14:0/16:0/18:0) and TG (16:0/17:0/18:0) in human milk were significantly lower than those in bovine and caprine milk (P < 0.05), and there were significant differences in the content of TG (17:2/18:0/20:5) among the three milks (P < 0.05). This study provides a theoretical basis for the study of lipids in infant formulas, and indicates that the identified differential lipid molecules can be used as a lipid marker for identification of bovine and caprine milk.
Comparison of Simultaneous Distillation and Extraction and Headspace-Solid Phase Microextraction for Analysis of Aroma Components of Huoshan Large-Leaf Yellow Tea by Gas Chromatography-Mass Spectrometry
ZHU Xiaofeng, LIU Zhengquan, WAN Xiaochun, TAO Meng, XIAO Zhipeng, CHENG Shuhua
2020, 41(4):  214-221.  doi:10.7506/spkx1002-6630-20190110-136
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Comparative analysis of the aroma components of Huoshan large-leaf yellow tea was performed by simultaneous distillation and extraction (SDE) and headspace-solid phase microextraction (HS-SPME) combined with gas chromatography-mass spectrometry (GC-MS). The results showed that the composition and contents of volatile compounds detected by the two methods were significantly different. A total of 74 compounds were obtained by SDE while 76 compounds by HS-SPME. In total, 44 components were detected by both methods. Furfural, 5-methyIfurfural, 3-ethyl-2,5-dimethylpyrazine and methyl salicylate were important substances that contributed to the unique aroma of large-leaf yellow tea and their relative contents were all over 2% obtained by both methods. Furthermore, 30 (styrene, benzeneacetaldehyde, cis-linaloloxide (furanoid), and linolenicacid) and 32 (benzaldehyde, tetradecane and geranylacetone) aroma components were exclusively detected by SDE and HS-SPME, respectively.
Processing Technology
Preparation of Angiotensin Converting Enzyme Inhibitory Peptides from Corn Gluten Meal by Ultra-high Pressure-Assisted Alcalase Hydrolysis
LIU Ziyi, GU Fengying, WANG Bolun, ZHANG Fan, LIU Hao, WANG Feng
2020, 41(4):  222-228.  doi:10.7506/spkx1002-6630-20190123-304
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An ultra-high pressure (UHP)-assisted alcalase hydrolysis process was established to prepare angiotensin converting enzyme (ACE) inhibitory peptides for corn gluten meal (CGM) in order to simultaneously increase the ACE inhibitory activity of CGM hydrolysate and the hydrolysis efficiency. A comparative analysis of the effect of UHP-assisted enzymatic hydrolysis, enzymatic hydrolysis after UHP pretreatment and enzymatic hydrolysis under atmospheric pressure was made on the inhibition rate of ACE. In the UHP-assisted enzymatic hydrolysis method, the operating parameters substrate concentration, time, pressure, pH and temperature were evaluated for their effects on the inhibition rate of ACE. These preparation conditions were optimized by response surface methodology (RSM). The ACE inhibition rate of the hydrolysate obtained by UHP-assisted hydrolysis (for 15 min) was increased by 55% compared with that obtained under atmospheric pressure, and 30% higher than that obtained with UHP pretreatment. pH was found to be the main factor affecting the ACE inhibition rate, followed by pressure, substrate concentration and time. The effect of temperature was not obvious. The results indicated that the ACE inhibition rate was up to 74.30% under the optimized conditions: substrate concentration 4.78%, high pressure holding time 14 min, pressure 372 MPa, and pH 8.4. UHP-assisted alcalase hydrolysis could not only increase the ACE inhibition rate but also shorten the hydrolysis time to within 15 min, which would provide a basis for the green and efficient preparation of corn protein-derived functional peptides.
Optimization of CO2-Low Temperature High Pressure Permeation Drying Process of Kiwifruit
SONG Yifan, CHEN Haifeng, YUAN Yuejin
2020, 41(4):  229-234.  doi:10.7506/spkx1002-6630-20190120-236
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In order to optimize the explosion puffing drying process of kiwifruit by CO2-low temperature high pressure permeation, the one-factor-at-a-time and quadratic regression orthogonal rotary combination design methods were jointly adopted to study the influence of puffing pressure difference, puffing temperature and pumping time on the degree of expansion, hardness and brittleness of kiwifruit chips. The response surface methodology was further used to optimize the ranges of the three process parameters and the advantages of using CO2 as a puffing medium were evaluated by comparison with N2. The results showed that all the examined factors had significant effects on the puffing degree, hardness and brittleness of the product (P < 0.05), with a significant interaction between each other; the optimal process parameters were determined as follows: puffing pressure difference 1.03–1.1 MPa, puffing temperature 80–82.46 ℃, and pumping time 90–91.61 min. Compared with hot-air dried kiwifruit chips, kiwi chips prepared by CO2-low temperature high pressure permeation drying had a looser structure, better taste, and higher VC retention rate.
Microwave-Assisted Preparation and Calcium Bioavailability Evaluation of Fishbone Flour of Tuna (Thunnus albacares)
YANG Lihong, WANG Honghai, ZHOU Xiaomin, MA Yongjun, WANG Jie, SHEN Qing
2020, 41(4):  235-242.  doi:10.7506/spkx1002-6630-20190311-139
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In this experiment, the microwave-assisted preparation of calcium powder from a byproduct of tuna processing, fishbone was optimized by Box-Behnken design combined with response surface methodology (RSM). The optimum parameters were determined as follows: sample amount 120 g, microwave power 800 W, and irradiation time 90 min. After removal of impurities by means of enzymatic hydrolysis, the calcium and phosphorus contents of the as-prepared fishbone calcium powder reached 192.3 and 149.8 mg/g, respectively. Scanning electron microscopic (SEM) characterization and laser particle size analysis revealed that the fishbone flour exhibited a loose structure with micropores and cracks appearing on the surface, and the average particle size was 16.627 μm, which was close to the RSM predicted value. The bioavailability evaluation in mice showed that the calcium absorption rate and calcium retention rate of the fishbone flour were respectively 59.62% and 58.31%, which were both significantly higher than those of common fishbone flour and calcium carbonate and low-calcium control (P < 0.05). Compared with other calcium preparations, the fishbone meal prepared in this study possessed higher absorption efficiency in vivo and was more conducive to promoting bone growth in mice.
Safety Detection
Qualitative and Quantitative Detection of Water-Injected Pork Using Low-Field Nuclear Magnetic Resonance Combined with Chemometrics
GAI Shengmei, ZHANG Zhonghui, YOU Jiawei, ZOU Yufeng, LIU Dengyong
2020, 41(4):  243-247.  doi:10.7506/spkx1002-6630-20181014-118
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In the present paper, the qualitative and quantitative detection of water molecules in water-injected pork were implemented by using low-field nuclear magnetic resonance (NMR) combined with chemometrics. Longissimus dorsi muscles were adulterated with 0%, 5%, 10%, 15%, 20% and 25% of deionized water by intramuscular injection. The peak area proportion of immobilized water (P21) in water-injected pork showed a significantly decreasing trend (P < 0.05), while the relaxation time (T22) and peak area proportion (P22) of free water increased significantly (P < 0.05). Subsequently, a single-variable linear regression (LR) was developed to quantitatively detect the moisture content in pork with rp (correlation coefficient of prediction set) = 0.31, and RMSEp (root mean square error of prediction set) = 4.02%). The optimized rp and RMSEp were 0.45 and 1.79%, respectively. On this basis, a multiple linear regression (MLR) model and a partial least squares regression (PLSR) model were used to quantitatively predict the moisture content in pork. It turned out that the MLR model had better prediction performance (rp = 0.90, RMSEp = 0.57%) than the PLSR model. To sum up, low field nuclear magnetic resonance combined with chemometrics can be an effective method for qualitative and quantitative detection of water molecules in water-injected pork.
Homogeneous Liquid-Liquid Microextraction Based on the Solidification of Sedimentary Ionic Liquid Coupled with High Performance Liquid Chromatography for the Determination of Phenylurea Residues in Vegetables Samples
XU Weili, FU Zhuang, WANG Xu, ZHAO Yue, WANG Chenzhao, MA Jiajun, WANG Zhibing
2020, 41(4):  248-255.  doi:10.7506/spkx1002-6630-20181004-013
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In this study, an analytical method using homogeneous liquid-liquid microextraction based on the solidification of sedimentary ionic liquid coupled with high performance liquid chromatography (HPLC) was developed and applied to the simultaneous determination of five phenylurea pesticide residues in vegetables. The hydrophilic ionic liquid noctyltributylphosphonium bromide ([P4448]Br) was used as the microextraction solvent. The extraction was carried out with the aid of ultrasound, after centrifugation and cooling. The analytes were enriched into the ionic liquid phase and deposited at the bottom of the centrifuge tube. The ionic liquid phase was diluted and used for chromatographic analysis. The combined use of one-factor-at-a-time method and Box-Behnken design response surface methodology was proposed to optimize the important extraction conditions. The experimental results showed that the regression models for the target analytes were all significant (P > 0.05). Good linearity with correlation coefficients greater than 0.998 1 was obtained under the optimum conditions. The limits of detection (LODs) and limits of quantification (LOQs) were in the range of 2.19–5.35 and 7.30–17.82 μg/kg, respectively. The recoveries for spiked samples were between 82.84% and 117.49% with relative standard deviations (RSDs) lower than 9.93%. The present method has the advantages of less solvent consumption, environmental protection and simple operation and thus can be used for the extraction and detection of phenylurea pesticide residues in vegetables.
Optimization of Modeling Conditions for Near Infrared Measurement of Protein Content in Milk by Orthogonal Array Design
PENG Dan, LIU Yali, LI Linqing, BI Yanlan
2020, 41(4):  256-261.  doi:10.7506/spkx1002-6630-20190313-160
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In order to improve the accuracy and stability of protein content measurement using near-infrared (NIR) spectroscopy, the spectral data of milk samples with different protein contents were analyzed using the two-dimensional correlation spectroscopy to identify the characteristic wavelengths region of protein. Then, the effects of wavelength bands, preprocessing algorithms and modeling methods on the prediction accuracy of the model were studied by single factor experiments. On this basis, the modeling conditions were optimized by orthogonal array design to avoid interactions. The results showed that all three factors had a great impact on the performance of the prediction model in the descending order of modeling methods, wavelength bands and preprocessing methods. Among the preprocessing algorithms tested, standard normal variable (SNV) algorithm and multiplicative scatter correction (MSC) algorithm could effectively eliminate the interference of scattering. The linear models such as principal component regression (PCR) and partial least squares (PLS) were significantly better than non-linear support vector machine regression (SVR). Finally, the optimized modeling conditions were determined as follows: detection wavelength range from 1 800 to 2 300 nm, MSC preprocessing, and PCR modeling. Under these conditions, the correlation coefficient (R2) and root mean square error of prediction (RMSEP) of the prediction model were 0.993 and 0.106, respectively. This research provides a feasible technical way to develop a new device for the rapid detection of protein content in milk in the future.
Simultaneous Determination of 3-Monochloropropane-1,2-Diol Esters and Glycidyl Esters in Infant Formula Powder by Isotope Internal Standard-Gas Chromatography-Mass Spectrometry
WANG Ya,, GAO Hongbo, SUI Haixia, QIU Kai, ZHONG Qiding, Lü Xiaoling
2020, 41(4):  262-267.  doi:10.7506/spkx1002-6630-20190326-335
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The aim of this study was the development of a method for the simultaneous determination of 3-monochloropropane-1,2-diol esters (3-MCPDEs) and glycidyl esters (GEs) in infant formula milk powder. Commercial infant formulas available on the Chinese market (n = 30) were analyzed for 3-MCPDEs and GEs by gas chromatography-mass spectrometry (GC-MS). Under the optimized conditions, 3-MCPDEs and GEs showed good linearity in the concentration range of 0.050?0.80 mg/L with correlation coefficient (R2) larger than 0.998. The mean recoveries from spiked samples were in the range of 81.4%?86.2% and 94.5%?101.1% with relative standard deviations (RSDs) ranging from 4.42% to 4.84% and from 4.46% to 6.12% for 3-MCPDEs and GEs, respectively. The limit of detection (LOD) of the proposed method was 30 μg/kg for both 3-MCPDEs and GEs. This method showed the advantages of high sensitivity, and accuracy, and could be suitable for the simultaneous detection of 3-MCPDEs and GEs in infant formula milk powder. In the 30 infant formula samples, levels of 3-MCPDEs and GEs ranged from 50.0 to 207.8 μg/kg and from 50.0 to 480.0 μg/kg with an average of 98.0 and 208.1 μg/kg, respectively.
Development and Comparison of Real-Time Polymerase Chain Reaction and Real-Time Recombinase Polymerase Amplification Assays for Detection of Clostridium perfringens in Food
LIU Libing, LI Ruiwen, CHEN Zhimin, WANG Jinfeng, SUN Xiaoxia, YUAN Wanzhe, WANG Jianchang
2020, 41(4):  268-272.  doi:10.7506/spkx1002-6630-20181026-307
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To develop a rapid detection method for Clostridium perfringens using real-time polymerase chain reaction (PCR) or real-time recombinase polymerase amplification (RPA), we designed specific primers and probe based on the conserved sequence of the plc gene of C. perfringens. The results of specificity analysis showed that the two established methods specifically detected C. perfringens but not other bacteria. The sensitivity of both methods was 1.3 pg/μL and the limit of detection for C. perfringens in artificially contaminated chicken and milk samples was 1.0 × 102 CFU/mL. The positive samples could be detected in 3–13 min by real-time RPA, and at least 24–46 min by real-time PCR (Ct = 17.45–33.65). Real-time RPA was better than real-time PCR with respect to analysis time, easiness of operation and portability. In conclusion, thanks to their high specificity and sensitivity and easy operation, real-time RPA and real-time PCR provided an effective technical approach for the rapid detection of C. perfringens.
Determination of Nine Macrolide Antibiotics in Pork Samples by Ultra-high Performance Liquid Chromatography Quadrupole/Orbitrap High Resolution Mass Spectrometry
MA Junmei, SUN Lei, CAO Meirong, LIU Zhuo, LI Qiang, FAN Sufang
2020, 41(4):  273-279.  doi:10.7506/spkx1002-6630-20181026-306
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A rapid method was presented for the determination of 9 macrolide antibiotics in pork samples by ultra-high performance liquid chromatography-quadrupole/orbitrap high resolution mass spectrometry. The samples were extracted with acetonitrile and the extract was defatted with n-hexane and then separated with a Waters Acquity BEH C18 column (2.1 mm × 100 mm, 1.7 μm) by gradient elution using a binary solvent system composed of methanol and 0.1% formic acid in water. The analytes were detected by quadrupole-orbitrap high resolution mass spectrometry in the full-scan and data-dependent scan (ddMS2) mode. The results showed that the deviation between the theoretical and measured accurate mass-to-charge ratio was lower than 1.0 × 10-6, and good linear relationships were observed in the concentration range of 0.5–100 ng/mL for the 9 antibiotics with correlation coefficients higher than 0.998. The limits of detection were in the range of 0.05–0.2 μg/kg and the limits of quantification were in the range of 0.1–0.4 μg/kg. The recoveries of the method ranged from 69.4% to 107.6% at spiked concentration levels of 0.1–4.0 μg/kg, with relative standard deviations (RSDs) lower than 10%. This method proved to be simple, rapid, and accurate, and therefore it was suitable for rapid screening for and quantitative analysis of 9 macrolides antibiotics in pork samples.
Determination of Lysinoalanine in Milk Products by Q-Orbitrap High Resolution Mass Spectrometry and Variation in Its Content with Temperature
NIE Xuemei, WANG Han, XU Xiuli, ZHANG Feng, CHEN Da
2020, 41(4):  280-286.  doi:10.7506/spkx1002-6630-20190328-350
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A rapid method for the determination of lysinoalanine in milk products by ultra-high performance liquid chromatography-quadrupole/electrostatic field orbitrap high resolution mass spectrometry (UPLC-Q-Exactive Orbitrap HRMS) was developed. Samples were hydrolyzed with hydrochloric acid to remove impurities such as proteins and then separated on an Ascentis C8 column (100 mm × 4.6 mm, 3 μm) by gradient elution using a binary solvent system composed of acetonitrile and 0.1% formic acid in water. The analytes were detected by quadrupole-orbitrap high resolution mass spectrometry in full-MS and data dependent scan (ddMS2) mode. The results showed that the deviation between the theoretical and measured accurate mass to charge ratio of lysinoalanine was lower than 1.0 × 10-6, and a good linear relationship was observed in the concentration range of 1–200 μg/L with a correlation coefficient higher than 0.999. The limit of detection (LOD) was 0.01 mg/kg and the limit of quantitation (LOQ) was 0.025 mg/kg. Recoveries of the method were in the range of 78.7%–117.1% at spiked concentration levels of 0.025, 0.1, and 0.25 mg/kg, and the relative standard deviation (RSD) for precision was 3.64%. The method had high accurate, repeatability and sensitivity, and consequently was suitable for the qualitative and quantitative screening of lysinoalanine in milk products. Furthermore, the pattern of variation in lysinoalanine content of liquid milk processed using small-scale simulated processing equipment at different temperatures was studied.
Determination of Rhodamine B in Ketchup, Tomato Sauce and Chili Powder by Micellar Electrokinetic Capillary Chromatography with Laser-Induced Fluorescence Detection
DING Xiaojing,, LIU Wenye,, WANG Ping
2020, 41(4):  287-292.  doi:10.7506/spkx1002-6630-20190101-006
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A new and simple method was developed for the accurate determination of rhodamine B in ketchup, tomato sauce and chili powder samples by micellar electrokinetic capillary chromatography (MEKC) with laser-induced fluorescence (LIF) detection. The separation was performed on an uncoated fused silica capillary 75 μm × 30 cm total length (effective length: 20 cm) with a separation buffer solution consisting of 30 mmol/L sodium tetraborate, 20 mmol/L sodium dodecyl sulfonate (SDS), 20 mmol/L sodium deoxycholate (SD) and 0.2 g/L polyethyleneglycol 35000. A solution containing 10 mmol/L SDS was used for sample extraction. The analysis could be completed within 10 min. A voltage of 8 kV was used for separation. The injection time and pressure were 5 s and 3.448 kPa, respectively. The excitation and emission wavelengths were 488 nm and 520 nm, respectively. The corrected peak area and the concentration of rhodamine B displayed a good linear relationship with a correlation coefficient (r) of 0.999 9 in the ranges of 0.02–1.28 mg/L. The limit of detection (LOD; RSN = 3) and limit of quantitation (LOQ; RSN = 10) were 5 and 15 μg/L, respectively. The intra-day and inter-day precisions of the method were both no less than 2%. The average recoveries of rhodamine B at three spiked concentrations (0.04, 0.16 and 0.64 mg/L) were in the ranges of 100.9%–105.8%. When the MEKC method was used to determine the contents of rhodamine B in 3 ketchup, 3 tomato sauce and 22 chili powder samples, the results were all lower than those measured by ultra-high performance liquid chromatography-fluorescence detection (UPLC-FLR). The possible reasons for the difference were analyzed and discussed.
Development of a Surface Plasmon Resonance Immunosensor for Detecting Olaquindox
XIE Chunhua, LIU Shuang, WANG Minsi, WANG Xialin, WANG Shen, ZHANG Zhijun, SONG Yang
2020, 41(4):  293-299.  doi:10.7506/spkx1002-6630-20180927-295
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A sensitive and stable competitive surface plasmon resonance (SPR) immunosensor was established and used to detect olaquindox (OLA) in feed and aquaculture water samples. Its sensitivity and limit of detection (LOD) were 4.7 and 0.5 μg/L, respectively. The best regeneration efficiency was obtained with 2.5 mmol/L NaOH solution, the chip could be reused 60 times and the detection time was only 10 min. The results of cross-reaction between OLA and structural analogs showed a high sensitivity and specificity. Additionally, good recoveries (84.7%–99.3%) and coefficients of variation (1.2%–10.1%) were obtained for spiked fish, shrimp feed and aquaculture water samples. When the method was applied to test actual samples of feed and culture water, two positive samples were detected. OLA contents in fish culture water and chicken feed were 5.0 and 6.1 μg/L, respectively. The method can efficiently detect OLA in large-volume feed and water samples, and has the advantages of short detection time, low detection limit, high accuracy and sensitivity, and convenient operation.
High-Throughput Detection of Three Types of Contaminants in Edible Oils by Gas Chromatography-Tandem Mass Spectrometry
MENG Weiyi, GU Jin, JIANG Rui, ZHANG Qing, ZHAO Wentao, MA Yanhong, ZHAO Yixin, LI Yingying, GUO Wenping
2020, 41(4):  300-306.  doi:10.7506/spkx1002-6630-20181019-212
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In this paper, a gas chromatography-tandem mass spectrometry (GC-MS) method was established for the determination of 18 phthalates, 16 polycyclic aromatic hydrocarbons and 7 polychlorinated biphenyls in edible oils. The sample was ultrasonically extracted with acetonitrile saturated by n-hexane, and the extract was cleaned up by solid phase extraction (SPE), separated on a DB-5 capillary column, ionized by electron impact and quantitated in the selective reaction monitor (SRM) mode. Good linearity was observed for all the analytes in the concentration ranges tested (0.04–2 mg/kg for phthalate acid esters, 1–40 mg/kg for diisodecyl phthalate (DINP), and 0.01–0.4 mg/kg for polycyclic aromatic hydrocarbons and polychlorinated biphenyls), with correlation coefficients more than 0.99. The limits of detection (LODs) were 8 μg/kg for DINP and 0.08–2 μg/kg for the other compounds. The recoveries ranged from 62.7% to 128.3%, with relative standard deviations (RSDs) of 1.1% to 13.6% (n = 6). The method was sensitive, accurate, simple, rapid and thus suitable for the detection of phthalate acid esters, polycyclic aromatic hydrocarbons and polychlorinated biphenyls in edible oils.
Determination and Contamination Pattern of Deoxynivalenol and Derivatives in Cereals and Their Products
GONG Lei, HAN Zhi, CHENG Hui, LIU Jie, PENG Qingzhi
2020, 41(4):  307-312.  doi:10.7506/spkx1002-6630-20181018-196
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High performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) has been adopted to set up a method for detecting deoxynivalenol (DON), deoxynivalenol-3-glucoside (D3G), 3-acetyldeoxynivalenol (3ADON) and 15-acetyldeoxynivalenol (15ADON) in cereals and their products, such as wheat flour, noodles, rice and corn grit. Samples were extracted with acetonitrile and the extract was degreased with n-hexane and cleaned up on a solid-phase extraction (SPE) column prior to being detected by HPLC-MS/MS. The quantitation was performed using an external standard method. The method was optimized and validated to meet the requirements for the detection of grains and their products. Furthermore, we analyzed the pattern of contamination of the four mycotoxins in 96 samples of cereals and their products. The results showed that 15ADON was not detected in any sample and 3ADON was detected in only one sample. Both DON and D3G were found in many samples. The detection rate of DON was higher than that of D3G, and it was the highest in noodles. In addition, we found a positive correlation between the contents of D3G and DON. The D3G/DON ratio was generally around 30%. The major mycotoxin in all types of samples was DON, of which noodles were the most contaminated.
Screening and Confirmation of Multiple Antibiotic Residues in Aquatic Products by Triple Quadrupole-Linear Ion Trap Mass Spectrometry
MENG Yong, WANG Jing, ZHU Xiaohua, GENG Xuebing, YANG Zong, SHEN Meifang
2020, 41(4):  313-318.  doi:10.7506/spkx1002-6630-20190313-167
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A rapid method for the screening and confirmation of 38 antibiotic residues in aquatic products was developed by high performance liquid chromatography-triple quadrupole-linear ion trap mass spectrometry (HPLC-Q-Trap-MS). The sample was extracted with acidified acetonitrile with EDTA-2Na, and then the extract was concentrated and degreased with n-hexane. Finally, the analytes were detected by HPLC-Q-Trap-MS in the multiple-reaction monitoring with information-dependent acquisition of enhanced product ion (sMRM-IDA-EPI) mode, followed by establishment of a multiple antibiotic database. The 38 antibiotics were confirmed by their retention times and ion pairs through database searching using the EPI library, and quantified by the internal standard method. All the antibiotics showed good linearity with correlation coefficients above 0.99. The limits of quantification (LOQs) for the antibiotics were in the range of 1.0–5.0 μg/kg. The average recoveries ranged from 63.5% to 117.3% with relative standard deviations of 2.6%–14.8% at spiked concentration levels of 1.0–50.0 μg/kg. The method is sensitive and accurate and can be successfully applied to the screening of antibiotic residues in aquatic products.
Determination of 10 Preservative Residues in Fruits by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
CAO Xueqin, YANG Fei, CHEN Guotong, MAO Qiongling, LI Fang, YANG Zhong
2020, 41(4):  319-324.  doi:10.7506/spkx1002-6630-20190410-137
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An analytical method for the simultaneous determination of the residues of 10 preservatives, including peimisine, carbendazim, thiophanate-methyl, thiabendazole, iprodione, imazalil, benomyl, procymidone, chlorothalonil and pyrimethanil, in fruits was developed by using ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were extracted by the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. The UPLC-MS/MS method was performed with an ACQUITY UPLC BEH C18 column using gradient elution with a mobile phase of acetonitrile and 0.1% formic acid in water. The target compounds were detected by multiple reaction monitoring (MRM) with an electrospray ionization source in the positive ion mode, and quantified by an external standard method using a matrix-match standard solution. The calibration curves showed good linearity with correlation coefficients greater than 0.992. The recoveries of the 10 preservatives at three spiked levels ranged from 75.0% to 112%, with relative standard deviations (RSDs) of less than 9.5% (n = 6). The limits of detection (LODs, RSN ≥ 3) were 0.02–1.50 μg/kg and the limits of quantity (LOQs, RSN ≥ 10) were 0.1–4.1 μg/kg for all the analytes. The established method is simple, sensitive, accurate and reliable, and can be applied for the simultaneous determination of multiple preservative residues in fruits.