Table of Content

25 July 2020, Volume 41 Issue 14
Food Chemistry
Heat-Induced Formation of Soy Protein Nanoparticles at Acidic pH for Encapsulation of Curcumin
YUAN Dan, ZHAO Mouming, ZHANG Sirui, HUANG Yi, ZHOU Feibai
2020, 41(14):  1-8.  doi:10.7506/spkx1002-6630-20190526-314
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In the present study, soy protein isolate (SPI) was subjected to static heat treatment (95 ℃ for 30 min) under specific pH conditions (pH 7.0 and 5.9) to form nanoparticles through self-assembly, designated as HSPI and HSPI (pH 5.9), respectively. The influence of homogenization and sonication was comparatively investigated on the encapsulation of curcumin as a hydrophobic active ingredient into protein nanoparticles. Results from fluorescence spectroscopy showed that hydrophobic interactions between SPI, HSPI and HSPI (pH 5.9) and curcumin caused fluorescence quenching of the protein and improved the water dispersibility of curcumin. Herein, heat treatment increased the protein surface hydrophobicity and particularly promoted the formation of particles with uniformed size distribution (PDI < 0.2) at pH 5.9, noticeably enhancing the protein-curcumin interactions. Homogenization and sonication promoted the encapsulation of curcumin into SPI, HSPI and HSPI (pH 5.9) upon driven by hydrophobic forces, and the effect of the latter was more pronounced. Moreover, when compared with SPI and HSPI, the core-shell structure of HSPI (pH 5.9) facilitated its co-assembly with curcumin during sonication, forming stable nanoparticles with uniformed size distribution, which significantly improved the water solubility and storage stability of curcumin.
Physicochemical Properties of Pectin Modified by Cross-Linking with Ferulic Acid under the Catalysis of Horseradish Peroxidase
LIU Yanzhao, LI Xiang, LIU Gongji, LI Jie, YAN Shoulei
2020, 41(14):  9-14.  doi:10.7506/spkx1002-6630-20190729-399
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In this study, in order to improve its functional properties and more broadly to enlarge its application scope, pectin from white radish was prepared by suction filtration followed by rotary evaporation and modified with ferulic acid as a cross-linker under the catalysis of horseradish peroxidase. The native and modified pectin were characterized by colorimeter, rheometer, scanning electron microscope and Fourier transform infrared spectroscopy. The results showed that after ferulic acid treatment, the pectin turned yellow, and its antioxidant potential significantly increased. In addition, ferulic acid treatment changed the surface microstructure, and cross-linked the dispersed pectin molecules together. The results of Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopy indicated that ferulic acid and pectin combined together to form a new substance.
Mechanism Underlying Protein Changes during Processing and Gelation of Sea Bass Surimi
LIU Fangfang, LIN Wanling, LI Laihao, WU Yanyan, YANG Shaoling, HUANG Hui, YANG Xianqing, LIN Zhi
2020, 41(14):  15-22.  doi:10.7506/spkx1002-6630-20190620-232
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The physicochemical changes such as pH, moisture content, and chemical interaction among proteins, trichloroacetic acid solution (TCA)-soluble peptide, protein solubility, protein secondary structures and ultra- structure were measured to study the mechanism underlying protein changes during the processing and gelation of surimi from sea bass. The results showed that during the processing of surimi, pH was adjusted to approximately 7 by rising, and was reduced by chopping and heating at low temperature. Heating at 40 and 90 ℃ had no significant effect on the moisture content of surimi. Rinsing effectively inhibited protein degradation, and reduced TCA-soluble peptide by 83%. Chopping had no significant effect on TCA-soluble peptide content, protein solubility or sulfhydryl group content (P > 0.05). Heating at 40 ℃increased TCA-soluble peptide content by 68% due to the action of cathepsin. Ion bonds and hydrogen bonds continued to decrease during the whole process, and decreased significantly upon heating (P < 0.05). Hydrophobic interaction and disulfide bonds showed an upward trend, reaching the highest value upon heating at 90 ℃. Upon heating at 40 ℃, the maximum level of non-disulfide covalent bond was reached. The content of β-fold structure decreased by 13% after rinsing, the content of β-turn structure increased by 39%, while the contents of random coil and α-helix did not significant changed (P > 0.05). Chopping did not significantly affect the contents of β-fold, β-turn, random coil or α-helix. Upon heating at 40 ℃, the α-helix content decreased and the β-fold content increased by 8%. Upon heating at 90 ℃, the β-turn content increased by 36% (P < 0.05), the random coil content did not significantly changed. Correlation analysis showed that the chemical bonds between protein molecules were significantly correlated with the contents of α-helix and β-turn, but not with the contents of β-sheet and random coil. This study provides useful information for further study of the mechanism underlying the formation of surimi gel.
Effects of Protein Concentration on Emulsion Properties before Whipping and Whipping Properties of Butter-Based Whipping Cream
DAI Keke, CHEN Bifen, HUANG Lihua, CAI Yongjian, ZHAO Xiujie, DENG Xinlun, ZHAO Mouming, ZHAO Qiangzhong
2020, 41(14):  23-29.  doi:10.7506/spkx1002-6630-20190619-218
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In this study, whipping cream was prepared with butter as the oil phase. The effect of protein concentration (1.0%–3.0%) on emulsion and whipping properties of butter-based whipping cream was investigated. Results showed that as protein concentration increased from 1.0% to 2.5%, the interfacial protein concentration of the emulsion rose significantly, the partial coalescence and size of fat globules decreased, particle size distribution became narrower and apparent viscosity increased in the emulsion before whipping, having a positive effect on emulsion stability. However, when the protein concentration increased from 2.5% to 3.0%, the partial coalescence of fat globules increased and fat globule size became larger, resulting in a negative effect on emulsion stability. During the whipping period of 200 s, the partial coalescence of fat globules increased continuously, average particle size first decreased and then increased, whereas overrun increased firstly and thereafter decreased. As the protein concentration increased from 1.0% to 1.5%, the partial coalescence of fat globules, average particle size, and overrun increased rapidly during whipping, resulting in overwhipping and poor foam stability. As the protein concentration increased from 2.0% to 2.5%, the partial coalescence of fat globules, average particle size, and overrun increased slowly, resulting in good foam stability. When the amount of protein further increased to 3.0%, although foam stability remained good, the partial coalescence of fat globules was only 26.45% after whipping for 200 s. Therefore, protein concentration of butter-based whipped cream was preferably in the range of 2.0%–2.5%.
Effect of Egg White Powder on the Characteristics of Proso Millet-Wheat Flour Dough and Steamed Bread
MA Weiwei, LI Wenzhao, WEI Jing, TIAN Miaomiao, CHEN Huan, RUAN Meijuan
2020, 41(14):  30-35.  doi:10.7506/spkx1002-6630-20190619-224
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In order to explore the effect of egg white powder on the characteristics of proso millet-wheat flour dough and the quality of steamed bread, doughs added with different proportions of egg white powder were observed by scanning electron microscopy and investigated by dynamic rheological analysis and infrared spectroscopy. The specific volume and texture of the resulting steamed breads were determined, and they were assessed by an electronic nose and sensory evaluation. The results showed that the addition of egg white powder enhanced the ability of gluten to wrap starch. As the amount of egg white powder increased, the elastic modulus of the dough increased firstly and then decreased after reaching a maximum value at an addition level of 3%, while the viscous modulus gradually decreased. The α-helix content of the dough showed an upward trend, while the opposite was true for the β-sheet content. In general, the considerable increase in the α-helix content observed suggested that the dough was relatively stable. As the amount of egg white powder increased, the specific volume of proso millet-wheat flour steamed bread increased firstly and then decreased after reaching a maximum at an addition level of 3%. The hardness and chewiness of steamed bread increased. Moreover, the contents of the flavor substance alcohols, aldehydes and ketones in steamed bread changed with the addition of different proportions of egg white powder. Upon addition of 3% egg white powder, the sensory evaluation score was within the acceptable range.
Effects of Plasma-Activated Water Curing on Oxidation and Structure of Pork Myofibrillar Protein
SUN Kekui, JIN Shenglang, PAN Yayan, WANG Yan
2020, 41(14):  36-41.  doi:10.7506/spkx1002-6630-20191029-319
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The aim of this study was to study the effects of plasma-activated water (PAW) brine on the oxidation and structure of pork myofibrillar protein. PAW was prepared by using plasma jet to treat distilled water for 0, 40, 60, and 80 s under the conditions of output voltage 20 kV, and current 0.025 mA, and then PAW and distilled water (as a control) were separately added with 8% NaCl, 3% sugar and 0.5% sodium pyrophosphate. Meat samples were marinated in the control and PAW brines with a 2:1 (m/m) ratio of meat to brine at 10 ℃ for 12 h. Afterwards, the oxidation, surface hydrophobicity and secondary structure of pork myofibrillar proteins were studied by analysis of total sulfhydryl and carbonyl contents, free amino acid contents, Fourier transform infrared (FTIR) spectra and protein surface hydrophobicity index (S0-ANS). The results showed that PAW curing could significantly increase the extent of protein oxidation (P < 0.05); the carbonyl content in the 40, 60 and 80 s treatments increased by 0.67, 1.42 and 1.57 nmol/g, respectively, compared with the control, while the total sulfhydryl content decreased by 14.51%, 19.35% and 30.65%, respectively. PAW loosened the compact protein structure; the proportion of α-helix in 40, 60 and 80 s treatments decreased by 10.73%, 20.71% and 33.32%, respectively, the proportion of β-sheet increased by 7.78%, 11.87% and 16.41%, respectively, the proportion of random coil increased 6.50%, 17.38% and 26.23%, while the proportion of β-turn did not change significantly in comparison with the control group. The contents of glutamic acid, phenylalanine, alanine, glycine, tyrosine and arginine significantly increased in the 60 and 80 s treatments. S0-ANS significantly decreased in the 40 s treatment but increased by 12.72% and 36.36% in the 60 and 80 s treatments, respectively. In conclusion, PAW brine could induce the oxidation of myofibrillar proteins and alter the secondary structure.
Stability of Reconstituted Oil Emulsion as Affected by Interaction between Oleosin Protein and Phosphatidyl Choline
SUN Yufan, XIE Fengying, ZHONG Mingming, QI Baokun, LI Yang
2020, 41(14):  42-49.  doi:10.7506/spkx1002-6630-20190527-324
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In order to study the effects of mixing ratio and interaction between oleosin protein (OL) and phosphatidyl choline (PC) on the stability of reconstituted oil emulsion, we determined the emulsification properties, fluorescence spectra, dynamic laser scattering patterns, turbidity, contact angle and storage stability of different samples. We observed the droplet size distribution and microstructure changes in emulsions by optical microscopy. The results showed that the particle size distribution of the emulsion was uniform, and the best emulsification properties were obtained (EAI = 33.11 m2/g, ESI = 74.22 min) with a ratio of OL/PC of 1.5. At the same time, the emulsion exhibited the best surface tension and storage stability. The fluorescence spectral analysis showed that OL was most closely combined with PC. But with the increase of OL concentration, competitive adsorption of OL with PC occurred at the oil-water interface, and as a result, the emulsifying ability and emulsion stability were both reduced, and irregular spherical droplets were observed by optical microscopy. The results showed that the optimum ratio of OL to PC was 1.5 for preparing reconstituted oil emulsion, which could promote the interaction between OL and PC and enhance the stability of the emulsion.
Combined Effects of TGase and Ca2+ on Gel Properties of Unwashed Clarias gariepinus Surimi
BAO Jiatong, NING Yunxia, YANG Qiyue, LIANG Liya, LI Ling, WANG Yang, MA Lizhen
2020, 41(14):  50-57.  doi:10.7506/spkx1002-6630-20190727-368
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In order to develop a new fish species for producing surimi products, surimi from Clarias gariepinus was obtained by chopping the fish meat with added cryoprotectant after cooling it in an ice bath instead of the traditional process involving rinsing and dehydration. The effects of transglutaminase (TGase) combined with different concentrations of CaCl2 on the gel properties of unwashed surimi were examined by measuring texture characteristics, gel strength, water-holding capacity, protein covalent crosslinking, microstructure and dynamic rheology characteristics. The results showed that adding TGase could effectively enhance the gel properties of surimi. When the concentration of TGase was 0.4%, the gel properties of surimi were significantly changed with increasing Ca2+ concentration from 20 to 80 mmol/kg. Ca2+ at low concentration of 20 mmol/kg could activate TGase when they coexisted, enhancing gel strength (3 261.97 g·mm), elasticity (0.92), cohesiveness (0.81), resilience (0.47) and water retention (76.32%). In addition, it shortened the relaxation time T22, increased the elastic modulus G’, and made the microstructure more compact with less cavities. However, high Ca2+ concentration (40–80 mmol/kg) decreased the gel strength and elasticity, increased hardness and T22, and decreased water-holding capacity and the degree of protein covalent crosslinking. Therefore, adding 0.4% TGase and 20 mmol/kg CaCl2 could effectively improve the gel properties of surimi.
Composition and in Vitro Antioxidant Properties of Soy Lipophilic Protein
ZENG Jianhua, LIU Linlin, YANG Yang, ZHANG Na, ZHU Xiuqing, SHI Yanguo, ZHENG Huanyu, WANG Xinyue
2020, 41(14):  58-65.  doi:10.7506/spkx1002-6630-20190627-364
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The purpose of this study was to investigate the antioxidant properties of soy lipophilic protein (SLP) and to analyze its amino acid and fatty acid profiles by amino acid automatic analyzer and gas chromatography (GC). The results showed that compared with soy protein isolate (SPI), 11S and 7S globulin, SLP was richer in branched-chained amino acids (16.44 g/100 g). A total of 27 fat acids were identified, mainly including palmitic acid, heptadecanoic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, and arachidic acid, with unsaturated fatty acids accounting for 66.55% of the total fatty acids. The in vitro antioxidant assay results showed that SLP had strong scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, 2,2’-azinobis-(3-ethylbenzothiazoline-6-sulphonate (ABTS) cation radicals, and ferric reducing-antioxidant power (FRAP), owing to the high content of Cys, Tyr and disulfide bonds, abundant phospholipids with good amphipathic property and a large hydrophobic core. The results provide theoretical support for the development and utilization of SLP as a functional protein in the fields of antioxidant and muscle building.
Effect of Temperature and pH on the Structure, Viscosity and Thermal Stability of Type II Collagen from Chicken Cartilage
XU Rong, ZHENG Lin, ZHAO Mouming
2020, 41(14):  66-71.  doi:10.7506/spkx1002-6630-20190624-294
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In order to investigate the effect of pH and temperature on the stability of chicken cartilage type II collagen, we used circular dichroism spectroscopy and an HAAKE rotational rheometer to analyze the triple helix structure and viscosity of collagen. In addition, we also explored the thermal stability by examining changes in the two parameters. The experimental results showed that the triple helix structure remained intact at pH values between 2.0 and 4.0, partially untwisted (28%–57%) in the range of pH 5.0–9.0, and the degree of unwinding was small (about 7%) at pH 10.0. The viscosity firstly increased and then decreased with increasing pH from 2.0 to 5.0, and it remained unchanged between pH 5.0 and 9.0 but increased once again with further increasing pH to 10.0. At pH 2.0–4.0, the denaturation temperature was between 37 and 39 ℃, suggesting poor thermal stability. At pH 5.0–7.0, the denaturation temperature was between 40 and 43 ℃, indicating good thermal stability. The viscosity and triple helix structure were negatively correlated with temperature (P < 0.05). With increasing pH from 3.0 to 9.0, the intermolecular electrostatic force and the viscosity decreased, and the degree of unwinding of the triple helix increased (P < 0.01). Therefore, in order to maintain the intact triple helix and good processing properties of type II collagen, it is necessary to strictly control the pH and temperature during processing.
Effect of Ultrasound on Microbial Growth and Metabolisms of Various Components including Phenolics during Fermentation of Apple and Strawberry Juice by Lactobacillus plantarum
WANG Hongmei, JIANG Sirui, TAO Yang, HAN Yongbin
2020, 41(14):  72-81.  doi:10.7506/spkx1002-6630-20190701-017
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The effect of ultrasound on microbial growth and the metabolisms of various components including phenolics during the fermentation of apple and strawberry juices by Lactobacillus plantarum was studied in this work. Samples were sonicated periodically for 2 min (5?s?on/5 s?off) at 58.3 and 93.6 W/L, separately during the fermentation process. Changes in microbial count and the contents of sugar, organic acid and phenolics were monitored. It was found that the count of stationary-phase L. plantarum in sonicated juices were significantly higher than that in juices without sonication. Sonication at 93.6 W/L increased microbial counts in apple and strawberry juices by 0.15 and 0.39 (lg(CFU/mL)) at 32 and 40 h of fermentation relative to the unsonicated control, respectively. Ultrasound promoted the catabolism and utilization of sugars by L. plantarum. The content of chlorogenic acid in sonicated apple juices was always lower than that in un-sonicated juices throughout the whole fermentation period. The content of chlorogenic acid in sonicated apple juice at 93.6 W/L was 10.44% lower than that in apple juice without sonication at 40 h of fermentation. The content of caffeic acid, produced from the hydrolysis of chlorogenic acid, in sonicated apple juices at 58.3 and 93.6 W/L were 60.56% and 99.53% higher than that in the control sample at 8 h of fermentation, respectively. Moreover, the sonicated apple juices contained higher amounts of citric acid at 8 h of fermentation. Sonication enhanced slightly the free radical scavenging capacity of both apple and strawberry juices in the late and early stages of fermentation, respectively. Overall, ultrasound treatment under appropriate conditions could promote the microbial growth and the catabolism of sugars, enhance the hydrolysis of chlorogenic acid in apple juice and the synthesis of citric acid in the early stage of fermentation, and improve the antioxidant capacity of both apple and strawberry juices.
Establishment of Qualitative and Quantitative Method for Intestinal Lactobacillus plantarum at the Strain Level
JIANG Shuaiming, MA Chenchen, YOU Zhengkai, ZHANG Jiachao
2020, 41(14):  82-87.  doi:10.7506/spkx1002-6630-20190625-311
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In this study, we aimed to establish a qualitative and quantitative method for the potential probiotic strain of Lactobacillus plantarum HNU082 using traditional selective isolation and culture method and genomic technology. For the purpose of qualitative analysis, the specific DNA fragment of the strain was selected by comparative genomics based on its whole genome sequence. Primers were designed targeting this DNA fragment and validated by using it to co-amplify L. plantarum HNU082 with other strains of L. plantarum. Subsequently, based on the annotation of antibiotic resistance genes from the whole genome of strain HNU082, the corresponding antibiotics were selected for verification, which made it easier to isolate L. plantarum HNU082 from the intestinal contents of the host. The qualitative analysis of the strain was accomplished by bacterial isolation using a selective medium and verification of the specific primers. Besides, using the specific primers of the strain, the quantitative analysis of the copy number of the strain was performed by quantitative real-time PCR. Finally, we validated the feasibility and accuracy of this method through a rat experiment. The qualitative and quantitative method will provide important methodological support for the in vivo study of priobiotic Lactobacillus.
Metabolic Differences in Post-Fermentation Stage of High Black Glutinous Rice Wine Based on GC-TOF-MS Metabolomics
JIANG Li, SU Wei, MU Yingchun, WANG Honglin, ZHAO Chi
2020, 41(14):  88-94.  doi:10.7506/spkx1002-6630-20190725-333
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This study aimed to analyze the differences and changes of metabolites during the fermentation process of high black glutinous rice. Gas chromatography-time of flight mass spectrometry was used to track and monitor the wine samples after 6 months of fermentation, and the data were analyzed in multivariate statistics. The results showed that the principal component model showed significant differences in metabolites after fermentation for 1, 4, 5, 6 months (P < 0.05). Based on orthogonal partial least squares discriminant analysis, a total of 40 metabolites were identified as differential metabolites (VIP > 1, P < 0.05), including 11 sugars and sugar derivatives, 13 organic acids, 7 amino acids, 5 ketones, and 4 other metabolites. Pathway analysis of differentially metabolites showed that the metabolic pathways that were significantly affected (impact value > 1 and P < 0.05) were glycerolipid metabolism, cysteine and methionine metabolism, starch and sucrose metabolism, arginine and proline metabolism, alanine, aspartate and glutamate metabolism, TCA cycle, valine, leucine and isoleucine biosynthesis, and glycerophospholipid metabolism.
Effects of Salt Stress on the Survival and Virulence Genes Expression of Escherichia coli O157:H7
YU Lanlin, JI Saisai, YU Jinlong, FU Wenjing, ZHANG Lin, LI Jiaolong, GAO Feng, JIANG Yun
2020, 41(14):  95-101.  doi:10.7506/spkx1002-6630-20190613-149
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To investigate the effects of salt stress at different levels on the survival and virulence gene expression of Escherichia coli O157:H7, as well as the correlation between them, three virulent strains (CICC21530, 95 and 109) collected in our lab were cultured separately in trypticase soy broth medium with different concentrations of NaCl (0, 6, 12 and 18 g/100 mL) for differnent time periods. Afterwards, each strain was enumarated, and the expression levels of virulence genes were detected by real-time polymerase chain reaction. Results showed that salt stress significantly decreased the survival of the three strains (P < 0.05), but the effect varied among these strains. Higher concentration of NaCl was associated with stronger inhibitory effects on strain CICC21530, while the survival of strains 95 and 109 were fluctuated. In addition, the expression levels of virulence genes in E. coli O157:H7 were related to strains and NaCl addition. At higher NaCl concentration, the expression levels of virulence genes in all strains increased significantly (P < 0.05) accompanied by a significant decrease in the survival rate. The highest expression levels of virulence genes were observed in strains CICC21530 and 95 at 18 g/100 mL NaCl concentration, and in strain 109 at 12 g/100 mL. These results suggested that the survival of E. coli O157:H7 strains were not completely consistent with the expression of virulence genes under salt stress, and the survival decreased while the expression levels of virulence genes increased. It is indicated that the survival of strains and the expression level of virulence genes should be simultaneously considered in the risk assessment of salty foods, which is beneficial for the scientific and comprehensive risk assessment of E. coli O157:H7.
Improvement of the Flavor of Sichuan Pickle by Co-fermentation with Weissella cibaria and Lactobacillus plantarum
ZHANG Nandi, ZHU Lin, XU Qin, XIANG Wenliang
2020, 41(14):  102-108.  doi:10.7506/spkx1002-6630-20190626-332
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This study evaluated the effect of co-fermentation with Weissella cibaria and Lactobacillus plantarum on the flavor of Sichuan pickle. During the fermentation process, lactic acid bacterial count, pH value, and lactic acid, acetic acid, malic acid and citric acid contents were analyzed. At the end of fermentation, the types and contents of volatile components in Sichuan pickle were determinate by head-space solid phase micro-extraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). Also, sensory evaluation was carried out. The results suggested that co-fermentation could enhance the quantities of lactic acid bacteria, lactic acid and acetic acid in the early stage of fermentation (0–4 d), and also improve the flavor and quality of Sichuan pickle at the end of fermentation. On the 1st day, lactic acid bacterial count reached 8.52 (lg(CFU/mL)) in the pickle brine containing both strains, which increased by 0.85 (lg (CFU/mL)) compared with L. plantanum alone. On the 3rd day, the content of lactic acid reached 10.9 g/L, which was higher than that produced by L. plantanum alone (5.5 g/L). At the end of fermentation, the flavor of pickle fermented by the mixed culture was superior to that of pickle fermented by L. plantarum alone. A total of 27 volatile flavor compounds were produced by co-fermentation, seven more than those produced by L. plantarum alone, and the total amount of volatile compounds produced by co-fermentation was 6.096 mg/L, significantly higher than that obtained with L. plantarum alone (only 3.188 mg/L). Therefore, W. cibaria has a good potential to be applied to improve the flavor of Sichuan pickle in combination with L. plantarum.
Using High-throughput Sequencing to Study the Development of Fungal Community in Stored Wheat
YUE Xiaoyu, ZHANG Hua, CHEN Weifeng, XU Wentao, GUO Mingzhang
2020, 41(14):  109-115.  doi:10.7506/spkx1002-6630-20190526-309
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In this paper, high-throughput sequencing technology was used to study the development of the fungal community in stored wheat and the factors influencing it, aiming to provide useful information for optimizing the storage conditions of wheat. The results showed that Alternaria, Aspergillus, and Cladosporium were the most abundant fungal contaminants in stored wheat. Aspergillus was the genus with the highest diversity at the species level, including 11 species. Storage period of wheat had a great influence on the fungal community. The fungal communities in wheat stored for one, two and three years had their own characteristic fungi. The location of wheat in the warehouse had little relationship with the fungal community, while the depth of the warehouse affected the fungal community, and the abundance of Sordariomycetes decreased with the increase in storage depth. The fungal communities of stored wheat in different provinces were quite different. This study can provide basic data for the establishment of a model for describing the development of the fungal community in stored wheat, and also provide feasible schemes for fungal control in stored wheat in the future.
Browning and Antioxidant Activity of Apple-Pear Jiaosu during Fermentation
FAN Hao’an, SHA Ruyi, FANG Sheng, XUE Shulong, CHEN Yu, HUANG Jun, CUI Yanli, MAO Jianwei
2020, 41(14):  116-123.  doi:10.7506/spkx1002-6630-20190515-151
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In order to study browning control and the pattern of change in antioxidant activity during the fermentation of apple-pear Jiaosu, we analyzed chroma, chromatic aberration, browning degree, polyphenol oxidase (PPO) activity, pH, total titratable acidity, ascorbic acid content, citric acid content, total phenolic content, total flavonoid content and antioxidant capacity. The results showed that chromatic aberration, browning degree and PPO activity initially increased and then decreased during fermentation, declining to 2.53, 0.706, 10.74 U/mL on the 140th day, while the change in L* value exhibited the opposite trend, and enzymatic browning was significantly inhibited during the late fermentation stage. pH declined gradually and then leveled off, while total titratable acidity showed the opposite trend, and ascorbic acid and citric acid contents increased first and then decreased. Total phenolic content continued to increase until reaching a maximum value of 0.426 mg/mL on the 140th day, and total flavonoid content increased overall except for a slight decline on the 50th day. Correlation analysis was used to investigate physicochemical parameters affecting browning control, including pH, total titratable acidity, and the contents of ascorbic acid, citric acid, total phenolics, and total flavonoids, which were all significantly correlated with browning degree and PPO activity (P < 0.05). During fermentation, the antioxidant activity including scavenging capacities against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical cation, hydroxyl radicaland hydrogen peroxide and reducing power increased gradually. Fermentation could inhibit enzymatic browning and improve the antioxidant activity of apple-pear Jiaosu.
Mutational Analysis of Kex2 Sites and Characterization of Tannase from Aspergillus fumigatus
LU Haiqiang, CHEN Wei, HUANG Lei, GU Xinxi, TIAN Hongtao
2020, 41(14):  124-130.  doi:10.7506/spkx1002-6630-20190611-111
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In this work, we investigated the effect of the Kex2 cleavage sites (K315-R316) on the enzymatic properties of tannase (AfTanA) from Aspergillus fumigates. We constructed a single amino acid mutant (AfTanR316A) and a double amino acid deletion mutant (AfTanΔKR). The two mutants were significantly enhanced for?resistance?to Kex2 proteases. Compared with the wild-type tannase (AfTanA), the mutants exhibited lower catalytic temperature and stronger stability. The optimum reaction temperatures of the mutants and the wild-type tannase were 20 and 40 ℃, respectively. After being treated for 1 h at pH 12.0, AfTanΔKR, AfTanR316A and AfTanA remained 85%, 60% and 0% of their original activity, respectively. After being treated for 1 h at 50 ℃, AfTanΔKR, AfTanR316A and AfTanA remained 40%, 21% and 2% of their original activity, respectively. The improved stability against pH and temperature were beneficial to the application of tannase at low temperatures and its production and storage. The Km and Vmax values of AfTanR316A were determined as 1.149 mmol/L and 10.427 mmol/(L·min). The Km and Vmax values of AfTanΔKR were determined as 1.46 mmol/L and 35.84 mmol/(L·min), respectively. In addition, compared with natural persimmon juice, juices treated separately with AfTanA and the mutants showed a 50% increase in the total phenolic concentration.?In?conclusion, the Kex2 protease cleavage sites (K315-R316) of AfTanA have a significant effect on the stability and catalytic efficiency, and AfTanΔKR could potentially be used in the food industry in the future.
Sequential Mutagenesis Treatment with Atmospheric and Room Temperature Plasma and Diethyl Sulfate for Enhanced Microbial Production of ε-Poly-L-lysine
XI Zhiwen, HUANG Linna, ZHAI Yichang, HUI Fengli
2020, 41(14):  131-137.  doi:10.7506/spkx1002-6630-20190517-191
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To enhance the production of ε-poly-L-lysine (ε-PL) by Streptomyces albluus, we mutagenized this strain by sequential treatment with atmospheric and room temperature plasma and diethyl sulfate (ARTP-DES). The optimized treatment conditions were determined as follows: ARTP power 110 W, exposure distance 2 mm, mutagenesis time 30, 60, and 105 s, DES concentration 0.6% (V/V), and reaction time 20 min. A rapid screening method was established by streptomycin resistance combined with methylene blue transparent circles. ε-PL content was determined by enzyme-linked immunosorbent assay (ELISA) with a 48-well microplate. The results showed that the positive mutation rate for streptomycin resistance was up to 40.8%. Furthermore, one strain designated AD-9 with good genetic stability was selected. It produced 2.1 g/L ε-PL in shake-flask fermentation, which was 2.1 times as high as that produced by the parent strain. Studies of the physiological characteristics indicated that the mutant strain AD-9 showed changes in nutritional requirements, pellet morphology and nutrient consumption during fermentation. This study indicates that continuous ARTP-DES mutagenesis is an efficient breeding method for increased production of ε-PL.
Optimization of Cleaning-in-place Regime for Removal of Bacillus cereus Biofilm
HUANG Ziyu, LIN Yingying, SONG Sijia, REN Fazheng, GUO Huiyuan,
2020, 41(14):  138-145.  doi:10.7506/spkx1002-6630-20190719-247
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In this study, using an orthogonal array design, the optimum cleaning-in-place (CIP) regime for thoroughly removing the biofilm of Bacillus cereus A1, which has excellent biofilm-forming ability and high alkali and acid tolerance, on stainless steel sheets was determined as sequential washing with 17.5 g/L NaOH solution at 85 ℃ for 20 min, water, 15 g/L HNO3 at 85 ℃ for 20 min, and water once again. To reduce their use, acid and alkali cleaning agents were used in combination with peracetic acid, and the optimized CIP protocol was determined as sequential washing with 15.0 g/L NaOH solution at 85 ℃ for 10 min, water, 10.0 g/L HNO3 at 85 ℃ for 10 min, 3 g/L peracetic acid at 25 ℃ for 10 min, and neutralizer. This CIP protocol could not only thoroughly remove Bacillus cereu, but also reduce the concentration of acid and alkali cleaning agents and the cleaning time, providing a more efficient and eco-friendly method to clean food processing equipment.
Biological Properties and Application of a Lytic Vibrio parahaemolyticus Phage
JIANG Yanhua, WANG Lianzhu, LI Fengling, QU Meng, GUO Yingying, ZHAI Yuxiu, YAO Lin
2020, 41(14):  146-152.  doi:10.7506/spkx1002-6630-20190514-147
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The biological properties of a lytic phage VpJYP2 that infects Vibrio parahaemolyticus were determined, and its bactericidal effect against V. parahaemolyticus in raw salmon fillets was analyzed as well. The results showed that the plaques of VpJYP2 were clear and about 1?2 mm in diameter with halos around them. VpJYP2 had an icosahedral head of about 64 nm in diameter and a tail of about 70 nm in length, with a tail sheath of 20 nm in width. VpJYP2 was identified to belong to the family Myoviridae. VpJYP2 had a genome of 25 363 bp containing 45 open reading frames (ORF), 13 of which were predicted to encode certain functional proteins. VpJYP2 was stable at 40?50 ℃ and under pH 4?11. Its optimal multiplicity of infection was 0.01. One-step growth experiments showed that its latent time and burst time were 5 and 55 min, respectively, and burst size was 45. VpJYP2 significantly reduced V. parahaemolyticus in raw salmon fillets. These results indicate that VpJYP2 can serve as a promising biocontrol agent against V. parahaemolyticus.
Proteolytic Characteristics of Protease from Bacillus methanolicus and Bioactivity of Casein Hydrolysates Obtained with It
YANG Zhijie, ZHENG Zhe, CAI Miao, ZHAO Xiao, LUO Tianqi, LI Runkun, CHEN Chao, CAO Yongqiang, YANG Zhennai
2020, 41(14):  153-160.  doi:10.7506/spkx1002-6630-20190629-398
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In this study, we firstly determined the optimal hydrolysis temperature and pH of the protease from Bacillus methanolicus LB-1 (protease LB-1), and then explored the proteolytic characteristics by continuously monitoring the changes in hydrolysis pH and oxidation-reduction potential (ORP) as well as using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and mass spectrometry. Bioactivities of casein hydrolysates obtained with the protease including scavenging effects on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical, inhibition effects on α-amylase and α-glucosidase, and metal ion-chelating activity were determined. The results showed that the optimal hydrolysis temperature and pH of protease LB-1 were 52 ℃ and 6.0–7.0, respectively. Casein was more effectively hydrolyzed than whey protein by the protease, and the hydrolysis extent of individual caseins followed the decreasing order: κ-casein > α-casein > β-casein. The hydrolysis sites of κ-casein were mainly Lys21-Ile22 and Lys112-Asn113. The highest scavenging rates of DPPH and ABTS cation radicals by the casein hydrolysate were 75.4% and 48.45%, the highest inhibition rates of α-amylase and α-glucosidase were 80.89% and 93.12%, and the highest chelating rates of calcium and zinc ions were 63.13% and 35.31%, respectively, indicating that the casein hydrolysate had potent antioxidant capacity, hypoglycemic effect and metal ion-chelating ability. Therefore, the protease isolated from B. methanolicus LB-1 could be potentially used in functional cheese processing and the development of bioactive peptides of dairy origin.
Fermentation of Indica Rice Flour Slurry by Three Pure Strains of Lactobacillus and Characterization of Amylases Produced by Them
LIANG Yan, CHEN Zhong, LIU Bingjie
2020, 41(14):  161-168.  doi:10.7506/spkx1002-6630-20190515-168
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In this paper, pure culture fermentation of indica rice flour slurry with three strains of Lactobacillus with the ability to degrade starch, L. acidophilus 14 (La), L. casei M (Lc) and L. plantarum 115 (Lp), was studied. It was found that all the strains had the ability to produce acid in fermented indica rice flour slurry, and the acid-producing ability at 12 h was in the decreasing order La > Lp > Lc. At the same time points, viable bacterial counts also followed this trend. The fastest increase in viable cell number and the strongest acid-producing capacity were observed for La from 4 h to 8 h, and for both Lc and Lp from 6 h to 10 h. The activities of amylases produced by the three strains (named La-a, Lc-a and Lp-a), followed the decreasing order: La-a > Lp-a > Lc-a. The maximum activity of La-a was 79.78 U/mL at 6 h, while the maximum activity of Lc-a and Lp-a was 51.89 and 68.77 U/mL at 8 h of fermentation, respectively. The three amylases were all neutral enzymes. The optimum temperatures of La-a, Lc-a and Lp-a were 55, 45 and 50 ℃, respectively, and the optimum pH values were 6, 7 and 6, respectively. The three amylases could not tolerate temperatures above 70 ℃, but Lp-a was relatively heat tolerant. Their pH stability was La-a > Lp-a > Lc-a. After fermentation, the total starch content in indica rice flour slurry decreased significantly, while the proportion of amylose in the total starch increased, indicating that a certain amount of isoamylase was produced during fermentation.
Regulation of Quorum Sensing on Biofilm Formation and Swimming Motility in Hafnia alvei
ZHU Yaolei, HOU Hongman, ZHANG Gongliang, HAO Hongshun
2020, 41(14):  169-174.  doi:10.7506/spkx1002-6630-20190624-288
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The aim of this study was to evaluate the regulation of quorum sensing on biofilm formation and swimming motility of Hafnia alvei H4 isolated from spoiled instant sea cucumber. Both the luxR and luxI genes were knocked out to construct the mutant strain ΔluxRI. Crystal violet staining method was used to measure the biofilm formation of H. alvei H4, and the structure of the biofilm was observed by scanning electron microscopy (SEM). In addition, the spread plate assay was used to detect swimming motility. The relative expression levels of biofilm- and motility-related genes (flgA, flgE, fliA, flhD and flhC) were measured by real-time PCR method. Results showed that growth of H. alvei H4 was not affected by depletion of the luxRI genes. However, AHLs production was found deficient in the ΔluxRI strain. In addition, biofilm formation of ΔluxRI was significantly inhibited (P < 0.05), and fewer cells were observed compared with the wild-type strain by SEM on the medium, and fewer reticular structures were formed by exopolysaccharides (EPS) from ΔluxRI. Furthermore, swimming motility of ΔluxRI was found to be obviously decreased. The relative expression levels of the flgA, flgE, fliA, flhD and flhC genes were significantly (P < 0.05) reduced. Therefore, a conclusion can be drawn that biofilm formation and swimming motility of H. alvei H4 is regulated by quorum sensing.
Bacterial Diversity Structure during the First Round of Pile and Pit Fermentation of Moutai-flavor Baijiu
HU Xiaoxia, HUANG Yongguang, TU Huabin, HU Feng, CHENG Pingyan, YOU Xiaolong
2020, 41(14):  175-182.  doi:10.7506/spkx1002-6630-20190618-195
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In order to further analyze the complex microbial system during the traditional solid-state fermentation process of Moutai-flavor Baijiu, we investigated the bacterial community structure in fermented grains from the first round of pile and pit fermentation by high-throughput sequencing technology. The results showed that the diversity and richness of bacteria during pile fermentation were higher than those during pit fermentation. After the start of pit fermentation, the diversity and richness of bacteria showed a sharp decline. At the phylum and genus levels, the species of total bacteria, major bacteria and dominant bacteria during pile fermentation were more than those during pit fermentation, and after the start of pit fermentation, rapid microbial community succession occurred from the complex structure containing multiple bacteria to a homogenous one dominated by Lactobacillus. There were 13 dominant genera during pile fermentation, including Lactobacillus, Escherichia-Shigella and Bacillus. The dominant genus during pit fermentation was Lactobacillus. There were significant positive correlations among the top 25 most abundant genera during pile and pit fermentation. The inhibitory effect of Lactobacillus on other bacteria was stronger during pile fermentation than during pit fermentation. The results of this study lay a scientific foundation for understanding the mechanism of the traditional solid-state fermentation of Baijiu and promoting industrial development.
Screening and Fermentation Characteristics of Acetic Acid Bacteria for Production of Jackfruit (Artocarpus heterophyllus Lam.) Vinegar
HE Yuning, HUANG He, ZHONG Saiyi, LIU Hai, QIN Xiaoming
2020, 41(14):  183-189.  doi:10.7506/spkx1002-6630-20190604-034
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In order to obtain a suitable acetic acid bacterial strain for the fermentation of jackfruit vinegar with improved acetic acid content and quality, acetic acid bacteria were isolated and purified from naturally fermented jackfruit vinegar, and identified by molecular biology based on 16S rRNA gene sequence and their fermentation characteristics were studied. The results showed that 5 strains of acetic acid bacteria were identified, including Aa723 and Aa941 (Acetobacter pasteurianus), Aa847 (A. fabarum), Aa747 (A. tropicalis), and Aa844 (A. aceti). Among these strains, Aa941 showed the best fermentation performance. After 96 hours of fermentation, the maximum acid yield of 38.70 g/L was obtained under the conditions of fermentation temperature 31 ℃ and ethanol concentration 4%, as well as the maximum alcohol-acid transform ratio of 74.85% under the conditions of fermentation temperature 30 ℃ and ethanol concentration 6%. Under the conditions of ethanol concentration 8% and fermentation temperature 30 ℃, the acid yield and alcohol-acid transform ratio were 25.11 g/L and 74.10% respectively. Aa941 could grow well under the conditions of fermentation temperature 37 ℃ and ethanol concentration 4%, and the acid yield and alcohol-acid transform ratio were 19.79 g/L and 65.10%, respectively, showing that the ethanol and temperature tolerance of Aa941 are superior to those of the commercial strain As1.41. It was found that strain Aa941 could ferment jackfruit wine into fruit vinegar with the characteristic aroma of jackfruit. Thus, it can be used as a starter culture for jackfruit vinegar fermentation.
Label-free Differential Proteomics Analysis of Hemp Seeds at Different Germination Stages
DONG Yan, ZHANG Zhenghai, WANG Ning, SUN Yufeng, WEI Lianhui, SONG Shumin, JI Yanru, YANG Qingli, SHI Jie, TIAN Yuan
2020, 41(14):  190-194.  doi:10.7506/spkx1002-6630-20190619-217
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In order to investigate the differential protein expression profile of hemp seeds at different germination periods, we analyzed the protein components of hemp seeds at 0, 12, 24, 36, and 48 h of germination by label-free quantitative proteomics and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Bioinformatics analysis was also conducted to explore the distribution, function and mechanism of action of the differential proteins during the germination process. The results suggested that compared with ungerminated seeds, a total of 86, 106, 135 and 158 differential proteins >1.5 folds, P < 0.05) were identified at four time points of germination. Gene ontology (GO) enrichment analysis showed that the differential proteins participated in important biological processes such as metabolic process, cellular process and single organism process. KEGG pathway analysis indicated that these proteins were involved in the biosynthesis of amino acids, carbon metabolism, 2-oxocarboxylic acid metabolism and glycolysis/gluconeogenesis.
Diversity and Function of Culturable Bacteria in Daqu and Brewing Environment of Moutai-flavor Baijiu in Maotai Town
REN Airong, HUANG Yongguang, TU Huabin
2020, 41(14):  195-202.  doi:10.7506/spkx1002-6630-20190517-203
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In this study, the culturable bacterial communities of Daqu and brewing environment samples of Moutai-flavor Baijiu in Maotai town were studied through traditional microbial isolation and screening and molecular identification. A total of 1 370 isolates belonging to 5 phyla, 28 genera and 59 species of bacteria were obtained, including Bacillus solani, B. gottheilii, B. paralicheniformis, Brevibacillus agri, Pseudomonas xanthomarina, Lelliottia nimipressuralis, Aureimonas sp., Sphingobacterium daejeonense, Oceanobacillus indicireducens, Cronobacter sakazakii, Mixta gaviniae, Paraburkholderia fungorum, Viridibacillus arvi and Atlantibacter hermannii, which have been rarely detected during Moutai-flavor Baijiu brewing. Analysis of the distribution frequency and dominance of bacteria showed that Bacillus, Lysinibacillus, Staphylococcus and Micrococcus were the core culturable bacteria in Daqu, while Bacillus, Staphylococcus, Micrococcus and Alcaligenes were the core culturable bacteria in the brewing environment, and Bacillus, Staphylococcus and Micrococcus were the culturable core bacteria common to Daqu and environmental samples. The diversity and structure of bacterial flora differed between Daqu and environmental samples for each round of fermentation, while the structure and succession of the main functional bacterial flora remained basically consistent. The dominant bacteria in Daqu and environmental samples could function to metabolize abundant enzyme systems and to strongly adsorb and degrade metal ions. The data of this study provide a basis for research on microorganisms involved in the brewing of Moutai-flavor Baijiu in Maotai town and other areas.
Diversity and Functional Enzymes of Endophytic Bacteria in Kuqa Apricot
LIU Xiaojing, CHU Min, ZHU Jing, GU Meiying, TANG Qiyong, SUN Jian, ZHU Xuan, ZHANG Zhidong
2020, 41(14):  203-209.  doi:10.7506/spkx1002-6630-20190529-359
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This study aimed to analyze the diversity of endophytic bacteria in postharvest Kuqa apricot for the purpose of discovering potential microbial resources and their functions. The composition of the endophytic bacterial community was analyzed by high-throughput sequencing. Meanwhile, endophytic bacteria were isolated using the traditional culture method, and identified by 16S rRNA gene sequence analysis. The enzyme activities of the isolates were tested. High-throughput sequencing results showed that 406 operational taxonomic units (OTUs) affiliated to 94 genera of 9 phyla were observed. Bacteroidetes, Bacillus, Paenibacillus and unclassified bacteria were the most abundant species. A total of 99 isolates were obtained, which were classified into 28 genera in the phyla of Actinobacteria, Proteobacteria, Firmicutes and Bacteroidetes. In addition, seven genera not detected by high-throughput sequencing and 5 potential novel species were discovered. At the same time, several isolates were found to be capable of producing protease, lipase, cellulase, amylase and pectase, which could provide abundant materials for further mining and development of potential microbial resource and enzymes from Kuqa apricot. The results provide a new idea for studying microbial deterioration of Kuqa apricot.
Selecting Antagonistic Yeast for Controlling Postharvest Disease of Peaches and Producing Solid Preparation
ZHANG Xiaoyun, YAN Xueli, WU Feng, GU Xiangyu, ZHAO Lina, ZHANG Shitao, ZHANG Hongyin
2020, 41(14):  210-216.  doi:10.7506/spkx1002-6630-20190530-379
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An antagonistic yeast for controlling Rhizopus rot of postharvest peaches was selected by in vivo tests. Then its biocontrol efficacy against natural decay of peaches and its effects on the quality of peaches were investigated. The conditions for producing a solid preparation of this antagonistic yeast by spray drying method were optimized by single-factor experiments and after being stored for 90 d, the obtained preparation was used to control Rhizopus rot of peaches. The results showed that the decay incidence of 72 h-stored peaches caused by Rhizopus rot was decreased by Pichia membranaefaciens (26.23%) compared with that of the control (95.70%). The antagonistic yeast also evidently reduced the natural decay incidence without adverse effect on the quality of peaches. The optimized conditions for producing the solid preparation were as follows: gum Arabic-to-trehalose ratio 1:1 (m/m); protectant concentration 100 g/L, atomizer pressure 200 kPa, inlet air temperature 100 ℃, and feeding speed 15 mL/min. The survival rates of this yeast strain in the obtained solid preparation were 66.97% and 82.91%, respectively after being stored at 25 and 4 ℃ for 90 d. The biocontrol efficacy of the solid preparation stored for 90 d at 4 ℃ was very obvious, although the decay incidence (37.04%) was significantly higher than that obtained with the freshly prepared yeast suspension (31.48%).
Component Analysis
Analysis of the Aromatic Components of Potato Flour Incorporated Instant Congee Processed by Explosion Puffing by Combined Use of SPME-GC-MS and PCA
BAI Jie, JIANG Huabin, TAO Guoqin, ZHANG Xiaofei, LI Yumei, PENG Yijiao
2020, 41(14):  217-224.  doi:10.7506/spkx1002-6630-20200109-109
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In this study, the aromatic components in potato flour incorporated instant congee processed with and without explosion puffing were investigated by solid phase microextraction (SPME) followed by gas chromatography-mass spectrometry (GC-MS) combined with principal component analysis (PCA). The results showed that the congee without explosion puffing treatment contained 50 aromatic components, 8 of which were the characteristic ones including hexanal, nonanal, 2-nonenal, phenylacetaldehyde, methylthiopropanal, 3-octen-2-one, furanone and 2,4-di-tert-butylphenol and most of which were hydrocarbons. The major aromatic compounds of the congee with explosion puffing treatment were heterocyclic compounds (especially pyrazines) and aldehydes, which gave the congee a roasted nut-like, burnt and unique potato-like flavor. According to PCA, the cumulative contribution rate of the three principal components to the total variance reached 90.758%, which reflected the changing trend of aromatic components in potato flour incorporated congee. PCA results showed that congees without and without explosion puffing treatment under different conditions of temperature and time (110 ℃/30 s, 130 ℃/30 s, 150 ℃/30 s, 170 ℃/30 s, 130 ℃/40 s, 130 ℃/50 s, and 130 ℃/60) were divided into four categories: 1) without explosion puffing, 2) 110 ℃/30 s, 130 ℃/30 s, 130 ℃/40 s, 130 ℃/50 s and 130 ℃/60 s, 3) 150 ℃/30 s , and 4) 170 ℃/30 s. Explosion puffing treatment had a certain effect on the overall flavor of potato incorporated congee, especially puffing temperature. At too high puffing temperature, a burnt flavor appeared as well as a darker color. Therefore, the optimal conditions for air puffing of potato incorporated congee were 150 ℃ for 30 s.
Analysis on Differences in Flavonoids and Aroma Compounds of Different Wine Grape Varieties
HU Li, PENG Wenting, LU Haocheng, WANG Jun
2020, 41(14):  225-233.  doi:10.7506/spkx1002-6630-20190625-310
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In this paper, the differences in the contents and compositions of anthocyanins, flavonols, flavanol-3-ols and aroma compounds in the Vitis vinifera cultivars ‘Cabernet Sauvignon’ (clones 338 and 685) and ‘Ruby Cabernet’, the Vitis amurensis cultivars ‘Shuangyou’, ‘Shuanghong’ and ‘Shuangfeng’, and the interspecific hybrid of the two cultivars ‘Beibinghong’ were analyzed by high performance liquid chromatography-mass spectrometry (HPLC-MS) and gas chromatography-mass spectrometry (GC-MS). The results showed that the total anthocyanin content of V. amurensis was much higher than that of V. vinifera, and it was dominated by bis-glucosidic anthocyanins but did not contain acylated anthocyanins. V. vinifera contained only monoglucosidic anthocyanins, while the hybrid cultivar contained both monoglucosidic anthocyanins and bis-glucosidic anthocyanins, as well as two acylated bis-glucosidic anthocyanins. V. vinifera contained the highest content of quercetins, while V. amurensis contained the highest content of myricetins. The mean degree of polymerization of flavanol-3-ols in the skin was higher than that in the seeds of V. vinifera, whereas the opposite was true for V. amurensis. The content of C6/C9 volatile aroma compounds in V. amurensis was significantly higher than that in V. vinifera. The differences in the contents and compositions of flavonoids and aroma compounds of different wine grape varieties (clones) can provide evidence for distinguishing among them.
Analysis of Characteristic Flavor Compounds in Single-Grain Chinese Baijiu Brewed from Different Raw Materials
JIANG Wei, WEI Jie, LI Baosheng, DONG Jianhui, WANG Xiaojun, SU Zhihua, HAN Xinglin, HUANGFU Jie, LUAN Chunguang, HAO Jianqin, WANG Deliang
2020, 41(14):  234-238.  doi:10.7506/spkx1002-6630-20190701-006
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The aroma-active compounds in five single-grain Chinese Baijiu brewed from different raw materials were detected by gas chromatography-olfactometry-mass spectrometry (GC-O-MS). A total of 22, 23, 20, 18 and 21 aroma-active substances were found in sorghum, wheat, non-glutinous rice, glutinous rice and corn Baijiu, respectively, mainly including esters, aldehydes and alcohols. The main aroma compounds identified were ethyl acetate, ethyl 2-methylbutyrate, 2-n-pentylfuran, ethyl caproate and ethyl octanoate. Nine dominant aroma compounds (with smell intensity equaling or exceeding 4) were detected in sorghum Baijiu, 7 in wheat, non- glutinous rice Baijiu, and corn Baijiu and 5 in glutinous rice Baijiu. The volatile components and aroma-active compounds identified in wheat Baijiu were more than those in the other Chinese Baijiu, and the compounds with high aroma intensity in sorghum Baijiu were more than those in the other Chinese Baijiu, and while those in glutinous rice Baijiu were the fewest. Sensory evaluation indicated that sorghum Baijiu scored highest in ester aroma and overall aroma balance. Wheat Baijiu was characterized mainly by ester aroma, corn Baijiu by corn-like and mellow aroma, and non-glutinous rice and glutinous rice Baijiu by refreshing mouthfeel.
Influence of Berry Shriveling on Grape and Wine Composition of ‘Cabernet Sauvignon’ in Southwest Shanxi Province of China
LI Junnan, NING Pengfei, REN Ruihua, YANG Jun, ZHANG Zhenwen
2020, 41(14):  239-246.  doi:10.7506/spkx1002-6630-20190802-044
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To investigate the effect of wine grape shriveling on its own quality and that of the resulting wine, we detected the key chemical components of normal and shriveled ‘Cabernet Sauvignon’ grapes and their mixture as well as in the wine produced from each sample. The results demonstrated that berry shriveling significantly increased sugar and acid contents, but decreased the levels of anthocyanins in both the grapes and the resulting wines. Berry shriveling also decreased monomeric phenol contents in the grapes but increased the types and contents of monomeric phenols in the wines. Compared to the wine produced from normal grapes, the wine produced from shriveled grapes contained significantly higher levels of ethyl acetate, acetic acid, 1-hexanol, benzyl alcohol and (E)-3-hexen-1-ol, which give the wine a stronger balsam-like, fresh fruit-like and preserved fruit-like flavor. Notably, the wine produced from the mixed sample contained significantly higher levels of 2,3-butanedione, benzaldehyde, ethyl octanoate, (Z)-2-hexen-1-ol and 1-dodecanol, emitting a strong creamy and flowery aroma.
Analysis of Eight Elements in Cod by Laser Induced Breakdown Spectroscopy
LIN Yuqing, TIAN Ye, CHEN Qian, LI Ying, LIN Hong
2020, 41(14):  247-254.  doi:10.7506/spkx1002-6630-20190821-222
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In this study, laser induced breakdown spectroscopy (LIBS) combined with univariate calibration, internal calibration and partial least square (PLS) was used for simultaneous quantitative analysis of P, Fe, Al, Mn, K, Mg, Ca and Na in cod samples. A series of cod standard samples with different concentrations of these elements were prepared, and reference values for each element concentration were determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES). The cod samples were compressed into tablets and their LIBS spectra were collected. The characteristic spectral lines were selected for each element, and the three quantitative methods of univariate calibration, internal calibration and PLS were compared. The results showed that PLS was superior to traditional univariate calibration and internal calibration, and had higher prediction accuracy and precision. The relative error (RE) of the predicted concentration ranged from 0.96% to 13.27%, and the relative standard deviation (RSD) ranged from 2.02% to 7.55%. This work showed that LIBS had great potential in the rapid and non-directional detection of various elements in cod and even other aquatic products, and could lay a foundation for the development of a portable LIBS device for multi-element analysis of aquatic products in the future.
Analysis of Volatile Flavor Components in Shuita-Branded Vinegar by Headspace Solid Phase Microextraction and Gas Chromatography-Mass Spectrometry
YANG Fuxiu, ZHOU Kaowen
2020, 41(14):  255-261.  doi:10.7506/spkx1002-6630-20190727-361
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The volatile flavor components of Shuita-branded vinegar were analyzed by headspace solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS). The effects of salt addition, extraction temperature, extraction time and desorption time on the total peak area and the number of effective compounds were investigated. The optimum extraction conditions were determined as follows: after being added with 2.5 g of NaCl, 7 mL of vinegar sample was extracted for 80 minutes at 80 ℃ with a CAR/DVB/PDMS extraction fiber. The optimum desorption time was 5 min. Under the optimum experimental conditions, the compounds were recognized by their deconvoluted total ion current chromatograms, qualitatively determined by Kovats index according to NIST14 mass spectral library and quantified with 2-octanol as an internal standard. A total of 75 compounds were separated and identified, including 16 esters, 15 aldehydes, 12 acids, 10 heterocyclic compounds, 6 alcohols, 10 ketones, 3 phenols and 3 ethers. Among them, 21 compounds with OAV ≥1 were identified as the main aroma-active components.
Effect of Aging Conditions on Volatile Flavor Compounds of Zhejiang Rosy Vinegar Evaluated by Multivariate Statistical Analysis
MU Xiaojing, FANG Guanyu, JIANG Yujian
2020, 41(14):  262-270.  doi:10.7506/spkx1002-6630-20190620-246
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In this study, solid phase microextraction coupled to gar chromatography-mass spectrometry was used to determine the volatile components in Zhejiang rosy vinegar under different aging conditions. Then the obtained data were analyzed by multivariate statistical analysis including principal component analysis (PCA) and orthogonal partial least squares-discriminant analysis (OPLS-DA). The results showed that: 1) The total contents of alcohols, acids and esters in rosy vinegar aged for 5 months at high temperature (35–40 ℃) and for 2.5 years at normal temperature were significantly lower than in those aged for 5 months at low temperature (0–5 ℃) and normal temperature (20–25 ℃) , whereas the total contents of ketones and aldehydes were relatively high in all samples. The content of furfural as a product of Maillard reaction increased significantly. 2) PCA and OPLS-DA could effectively distinguish Zhejiang rosy vinegar aged under different conditions. The rosy vinegar aged for 5 months at high temperature and the one aged at normal temperature for 2.5 years were classified into one group, and those aged at low and normal temperature for 5 months into another group, indicating that the aging period can be shortened at high temperature. 3) According to the results of OPLS-DA S-plot and OPLS-DA loading factors plot, the important aroma components of rosy vinegars under different aging conditions and the characteristic aroma components under each aging condition were obtained.
Effects of Stir-frying Time and Method on Volatile Flavor Compounds in Highland Barley
ZHANG Yao, ZHANG Wengang, DANG Bin, YANG Xijuan, CHEN Danshuo, HAO Jing
2020, 41(14):  271-277.  doi:10.7506/spkx1002-6630-20190724-323
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The effects of roasting time and methods on the volatile composition of highland barley (cv. Dulihuang) were studied by gas chromatography-mass spectrometry (GC-MS) combined with aroma analysis. The results showed that with the increase of stir-frying time, the types and contents of volatile substances increased, and the main flavor substances were heterocyclic compounds. The highest content of volatile substances of 46.09% was obtained at 8 minutes of stir-frying time. The traditional process of stir-frying followed by grinding produced more types of heterocyclic compounds as well as more prominent characteristic roasted aroma as compared with the opposite sequence. A total of 21 peaks were found to be common to all samples irrespective of stir-frying time or methods, among which pyrazines were the most representative aroma components in stir-fried highland barley. With the increase of stir-frying time, the fruity, herbal, flowery, and faint fatty aroma of raw highland barley changed to typical roasted highland barley-like aroma dominated by cocoa-like, roasted, nut-like and faint fruity aroma. According to the results of hierarchical cluster analysis (HCA) and principal component analysis (PCA), the similarity between 8 and 11 min stir-fried samples was high, indicating that their aroma composition and content were comparatively consistent, but the content of heterocyclic compounds was the highest at 8 min of stir-frying, so that 8 min could be considered as the most suitable stir-frying time for highland barley. This study can provide a theoretical basis for the development of roasted highland barley foods.
Effect of Different Roasting Temperatures and Initial Moisture Contents on the Volatile Flavor Components of Sunflower Butters
LI Cuicui, HOU Lixia, WANG Xuede, LIU Hongwei
2020, 41(14):  278-285.  doi:10.7506/spkx1002-6630-20190731-432
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The volatile compounds of sunflower butters produced with different initial moisture contents at different roasting temperatures were identified by headspace solid-phase micro-extraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Principal component analysis (PCA) was?performed?to determine the key flavor components of sunflower butters based on relative odor activity values (ROAV). The?results?showed?that the relative contents of heterocycles such as 2,5-dimethylpyrazine in sunflower butter prepared from roasted sunflower seeds were significantly increased in comparison with that prepared from unroasted sunflower seeds whereas the relative contents of aldehydes were significantly decreased. Sunflower butter made from sunflower seeds roasted at 170 ℃ had a richer flavor. The highest relative content of pyrazines was found in sunflower butter with initial water content of 5.40%. Increased initial moisture content reduced the relative content of pyrazines but increased the relative content of aldehydes causing a negative impact on the flavor of sunflower butters. PCA indicated that n-hexanol and acetic acid were the characteristic flavor substances of sunflower butter prepared from unroasted seeds. Aldehydes such as n-hexanal, octanal and (E,E)-2,4-decadienal were the characteristic flavor substances of sunflower butter made from sunflower seeds roasted at 140 ℃, having an oxidized lipid-like flavor. Pyrazines such as 2,3,5-trimethylpyrazine, 3-ethyl-2,5-dimethylpyrazine, and 2,3-diethyl-5-methylpyrazine were the characteristic flavor substances of sunflower butters made from sunflower seeds roasted at 170 and 200 ℃, having a noticeable roasted flavor.
Processing Technology
Extraction of Polysaccharides from Dendrobium officinale and Their Inhibition Effect on Hydroxyl Radical-Induced Apoptosis of SH-SY5Y Cells
ZHANG Yadan, ZHAO Mengqian, YANG Yujiao, XU Youzhi, WANG Zijun, WANG Yanjun, XU Diya, ZHANG Lin, ZHOU Binbin
2020, 41(14):  286-293.  doi:10.7506/spkx1002-6630-20190802-033
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The ultrasonic-assisted enzymatic extraction of polysaccharides from Dendrobium officinale was optimized using one-factor-at-a-time and orthogonal array design methods. Solid-to-liquid ratio, ultrasonication time, and enzyme concentration were considered as independent variables. High performance liquid chromatography (HPLC) was used for analyzing the monosaccharide composition of D. officinale polysaccharides. Coumarin-3-carboxylic acid (CCA) fluorescence method was employed for determining the antioxidant activity of D. officinale polysaccharides. Methyl thiazolyl tetrazolium (MTT) and flow cytometry were employed for investigating the inhibition effect of the polysaccharides on hydroxyl radical-induced apoptosis of SH-SY5Y cells. The results showed that the optimum extraction conditions were as follows: solid-to-solvent ratio 1:100 (g/mL), ultrasonication time 2 h, and enzyme (a 1:1 mixture of cellulase and pectinase, m/m) concentration 50%, and the yield of polysaccharides was 25.69% under these conditions. The monosaccharide composition analysis showed that D. officinale polysaccharides were mainly composed of mannose and glucose. D. officinale polysaccharides at concentrations ranging from 20 to 80 μg/mL could effectively scavenge hydroxyl radicals produced from hydrogen peroxide with Cu2+ as a catalyst and consequently decreased hydroxyl radical-induced apoptosis of SH-SY5Y cells (the apoptotic rate decreased from 56.97% to 17.97%) in a concentration-dependent manner.
Safety Detection
Preparation and Application of Dendritic Surface-Enhanced Raman Scattering Substrates in the Detection of Trace Malachite Green
ZHAO Jingchen, HUANG Dandan, ZHU Shuhua
2020, 41(14):  294-299.  doi:10.7506/spkx1002-6630-20190326-342
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Dendritic gold nanoparticles (Au NPs) were synthesized by reducing chloroauric acid (HAuCl4) with ascorbic acid in an aqueous solution of N-methyl-N-dodecylpiperidinium bromide (C12PDB). Transmission electron microscopic (TEM) images showed that the dendritic Au NPs, with good symmetry and multilevel branches, had a diameter of 3.5–4 μm. When surface-enhanced Raman substrates (SERS) were used to detect rhodamine 6G (R6G), these Au NPs showed excellent enhancement effect with an enhancement factor of about 105. These SERS substrates showed high sensitivity with a minimum detectable concentration of R6G as low as 3 × 10-9 mol/L. The SERS substrates based on these dendritic Au NPs also showed good signal repeatability with relative standard deviation (RSD) lower than 10% (n = 10). The dendritic Au NPs substrates afforded limits of detection (LOD) around 1 × 10-8 mol/L for aqueous malachite green (MG) solutions. These Au NPs were successfully applied to rapidly detect MG in Carassius auratus samples. The recoveries of MG were 81.6%–102.1% in the spiked samples.
Fluorescence “Turn-on” Biosensor for the Rapid Detection of Deoxynivalenol in Grains Based on Randomly Arrayed G-Quadruplex
HAN Yitao, SUN Lijun, ZHANG Yan, SONG Xiaojie, GAO Xue, WANG Li, XIE Gang
2020, 41(14):  300-306.  doi:10.7506/spkx1002-6630-20190320-262
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In this study, a fluorescent “turn-on” biosensor for rapid and sensitive detection of deoxynivalenol (DON) in grains was developed based on randomly arrayed G-rich DNA sequence and endonuclease digestion. This template-independent G-quadruplex (G4) could form a stable fluorescent complex with G4-specific dye, enhancing the fluorescence intensity. Under the optimal conditions, DON was sensitively detected in a wide linear range from 0.1 to 60 ng/mL with a limit of detection (LOD) of 10 pg/mL. The proposed method showed good selectivity, repeatability and stability. It was successfully applied to the determination of DON in wheat and corn samples, and recoveries from 94% to 112% were obtained with relative standard deviation (RSD) of 3.4%–4.9%. This strategy possessed many advantages, including simplicity, rapidity, no need for label, low cost and high sensitivity, and therefore could be useful for the detection of DON in grains.
Determination of 90 Nafils in Health Foods by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
MA Junmei, WANG Jing, SUN Wenyi, JIANG Jie, LI Qiang, FAN Sufang
2020, 41(14):  307-313.  doi:10.7506/spkx1002-6630-20190725-328
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An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed to determine 90 nafils in health foods. The samples were extracted with methanol, and the extracts were then separated on a Waters Acquity UPLC BEH C18 (2.1 mm × 100 mm, 2.5 μm) using a gradient mobile phase composed of acetonitrile and 0.1% formic acid in water. Multiple reaction monitoring was used to acquire mass spectrometric data. An external standard method was adopted for quantification. The results showed that good linearity was obtained in the concentration range of 0.2–50 ng/mL for the 90 nafils with correlation coefficients higher than 0.995. The limits of detection (LODs) were in the range of 2.5–25.0 μg/kg, and the limits of quantitation (LOQs) were in the range of 5.0–50.0 μg/kg. The recoveries were in the range of 78.0%–109.9% at spiked concentration levels between 5.0 and 500 μg/kg with relative standard deviations (RSDs) lower than 10%. The developed method was successfully used for accurate and quantitative measurement of the 90 nafils in health foods.
Real-Time Detection of Lipidomic Characteristics of Air-Fried Hairtail by iKnife Rapid Evaporative Ionization Mass Spectrometry
ZHANG Mengna, SONG Gongshuai, WANG Haixing, RAO Wei, WANG Honghai, SHEN Qing
2020, 41(14):  314-320.  doi:10.7506/spkx1002-6630-20190731-428
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This study aimed to introduce iKnife rapid evaporative ionization mass spectrometry (REIMS) for high-throughput, fast and real-time detection of lipids in marine foods. The output power of iKnife was optimized and the effects of different air frying temperatures on the composition of fatty acids and phospholipids in hairtail were investigated. The results showed that the optimal electrosurgical output power that provided maximum signal-to-noise ratio for the representative lipid ions was 20 W. The lipid composition of hairtail air-fried at different temperatures was directly detected by REIMS in real time without any pretreatment. The most abundant fatty acid was docosahexaenoic acid (DHA) and the most abundant molecular forms of phospholipid were phosphatidyl ethanolamines (PE) and phosphatidyl cholines (PC). In general, the degree of saturation of lipids increased as the air frying temperature increased, and the content of DHA decreased from 38.91% to 30.74%. The cumulative contribution rate of the first and second principal components to total variance obtained by principal component analysis was 78.6%, which could clearly distinguish among different haitail samples. The representative ions were selected to verify the iKnife-REIMS method. The results showed that the method was precise and repeatable, and allowed valid and reliable determination of lipid composition.
Migration of Copper from Nano-Copper/Low Density Polyethylene Composite Films to Milk Products
LU Shan, HU Changying, ZHANG Qinjun, ZHONG Huaining, HU Xiaohong
2020, 41(14):  321-326.  doi:10.7506/spkx1002-6630-20190401-010
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Microwave digestion followed by inductively coupled plasma mass spectrometry (ICP-MS) was used to detect the migration of copper from a laboratory-made nano-copper/low density polyethylene (LDPE) composite film to milk products versus the corresponding food simulants. In addition, the influence of ultraviolet (UV) radiation on the migration of copper from the composite film to milk products was evaluated as well as the influence of cooking on the migration of copper from the composite film to pure milk. The results showed that the limits of detection (LOD) and limits of quantitation (LOQ) of copper migration were 8.42 and 28.06 mg/kg, respectively. The recovery and precision expressed as relative standard deviation (RSD) of the ICP-MS method were 97.46%–107.30% and 1.98%–6.06%, respectively. The migration amount of nano-copper to yogurt was higher than that to pure milk. The migration of nano-copper from the nano-composite film with 1% copper to yogurt was significantly higher than that to pure milk under the same conditions. Moreover, the migration amount to 50% ethanol significantly decreased by 39.19–48.94 mg/kg compared with that to pure milk. The migration amounts to 3% and 4% acetic acid significantly increased by 1 598.66–1 760.92 and 1 868.97–2 159.58 mg/kg compared with that to yogurt, respectively. The migration of nano-copper to milk products did not change after UV treatment. Under cooking conditions, the migration amount was far below the regulatory limit. The existing limit does not apply to the migration amount of nano-copper to pure milk and yogurt.