Table of Content

25 August 2021, Volume 42 Issue 16
Food Chemistry
Effect of Low-sodium Salt Mixture on Physicochemical Properties and Flavor of Fermented Sausages
WANG Ningning, FENG Meiqin, SUN Jian
2021, 42(16):  1-7.  doi:10.7506/spkx1002-6630-20210409-116
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The effect of partial replacement of sodium chloride by a low-sodium salt combination on the quality of fermented sausages was investigated by measuring physicochemical indexes, sensory evaluation, taste characteristics from electronic tongue, and the contents of free amino acids and volatile compounds. Two groups were designed, control group (100% sodium chloride), and experimental group (sodium chloride 58%, potassium chloride 30%, calcium chloride 7% and glycine 5%). The results showed that after 21 days of fermentation, the pH and moisture content of sausages decreased significantly, while the sodium content increased significantly. The pH and moisture content of the experimental group were significantly lower and higher than those of the control group, respectively. The low-sodium salt substitute improved the color and texture characteristics of the product without significantly changing the sensory quality. Electronic tongue analysis showed that the umami, richness and bitterness of the low-sodium salt group were significantly higher than those of the control group. In addition, the low-sodium salt substitute promoted the release of free amino acids while having no negative impact on the production of volatile compounds. Therefore, the experimental group reduced the NaCl content by 42% while maintaining good sensory and flavor quality.
Effect of Replacement of Pork Fat with Pre-Emulsified Oil on the Quality of Emulsified Sausage
CHEN Chen, WANG Jiajia, WANG Lijian, ZHUANG Xinbo, CHEN Yinji
2021, 42(16):  8-13.  doi:10.7506/spkx1002-6630-20200805-077
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The effects of replacement of pork back fat with pre-emulsified fish or corn oil at different levels (25%, 50%, 75% and 100%) on the chemical composition, cooking loss, color, texture, rheology and sensory properties of emulsified sausages were studied. The results showed that the fat content decreased significantly (P < 0.05), and the cooking loss also dropped gradually with increasing level of pre-emulsified oil. Hardness values in the replacement groups were significantly different from each other and higher than that in the control group (P < 0.05). Hardness rose and then declined with increasing level of pre-emulsified oil, reaching a maximum at 50% replacement level. However, there was no significant difference in springiness (P > 0.05). Chewiness exhibited a consistent trend with hardness (P < 0.05). Dynamic storage module (G’) was increased by replacing pork fat with pre-emulsified oils, reaching a maximum at 50% replacement level. The sausage incorporated with 50% pre-emulsified oils scored the highest in appearance, flavor and overall acceptability. Therefore, replacing pork fat at 50% with pre-emulsified oil can effectively reduce the fat content, and significantly improve the texture characteristics and consumer acceptability of emulsified sausages.
Effect of Protease Treatment on Sensory Quality and Free Amino Acids of Skim Milk
CHENG Jiao, SUN Jing, LIANG Xiaona, QIAN Guanlin, YUE Xiqing, ZHENG Yan
2021, 42(16):  14-22.  doi:10.7506/spkx1002-6630-20200714-190
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The effects of enzymatic hydrolysis on the sensory quality and free amino acid composition of fresh skim milk were analyzed by a spectrophotometer, an electronic tongue and an amino acid automatic analyzer. The results showed that the degree of hydrolysis of defatted milk was 24.61%. Protease treatment led to changes in its sensory properties, and L* values of all three hydrolysates were significantly decreased (P < 0.05), and a* values (negative value) were significantly increased (P < 0.05) when compared with the untreated control. The effect of flavourzyme treatment on the color of skim milk was greater than that of alkaline protease treatment and protamex treatment. Large differences in taste profile were observed among the different hydrolysates. After enzymatic treatment, the sweet taste of skim milk was decreased significantly. With increasing digestion time, the bitter taste was enhanced accompanied by a decrease in the sweet taste. The taste profile of the alkaline protease hydrolysate was dominated by astringency and astringent aftertaste, the taste profile of the flavourzyme hydrolysate was dominated by saltiness, bitterness and bitter aftertaste, and the taste profile of the protamex hydrolysate was dominated by sourness as well as low and bitter taste. The electronic tongue was able to distinguish the difference in taste among the hydrolysates. The contents of free amino acids and essential amino acids in defatted milk were increased after enzymatic hydrolysis, making bitter amino acids become the dominant taste-active amino acids. In conclusion, enzymatic hydrolysis could change the color, taste and free amino acid composition of skim milk, and the effect of flavourzyme was greater than that of alkaline protease and protamex.
Effect of Curdlan on Processing and Eating Quality of Rice Noodles
LI Caiming, CHEN Di, LU Ruiqi, GU Zhengbiao, BAN Xiaofeng, HONG Yan, CHENG Li, LI Zhaofeng
2021, 42(16):  23-28.  doi:10.7506/spkx1002-6630-20200814-185
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The purpose of this study was to explore the effect of curdlan on the processing and eating quality of rice noodles. Three curdlan products (CG-E, CG-01, and CG-02) were added at level of 0%–1.0% into rice flour, and the changes in the gelatinization, texture and cooking characteristics of rice noodles were analyzed. After the optimal type and amount of curdlan were determined, X-ray diffraction and scanning electron microscopy were used to study the effect of curdlan on the aging process and gel structure in rice noodles. The results showed that adding 0.2% curdlan enhanced the water absorption and swelling of rice noodles during processing and cooking, thereby reducing the hardness, elasticity and chewiness and increasing the gap in the gel structure. However, addition of 0.4%–0.6% curdlan could significantly improve the texture and cooking quality of rice noodles without affecting the short-term aging; furthermore, it could slow down the long-term aging and make the gel network more compact. This study may provide a reference for the application of curdlan in rice noodles and even other rice products.
Effects of Different Antioxidants on the Quality of and Heterocyclic Amine Formation in Deep-fat Fried Meat Products
LI Mingyang, CHEN Shenghuizi, NIU Xiyue, XU Qian, REN Xiaopu, PENG Zengqi
2021, 42(16):  29-38.  doi:10.7506/spkx1002-6630-20200714-189
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The effects of eight antioxidants which are permitted to be added to deep-fat fried meat products according to the Chinese national standard GB 2760—2014 on the quality of and heterocyclic amines (HAs) formation in deep-fat fried meat patties from three animal species were systematically analyzed. The results showed that different antioxidants had different effects on meat quality. Addition of antioxidant of bamboo leaves (AOB), phytic acid (PA), carnosic acid (CA), rosmarinci acid (RA) or tea polyphenol (TP) maintained a higher level of moisture content during the deep-fat frying process, and also decreased the cooking loss and improved the tenderness and texture characteristics. Different antioxidants showed different inhibitory activities on the formation of various HAs. In deep-fat fried chicken patties, PS exhibited the highest inhibition rate (48%) on 2-amino-1-methyl-6-phenylimidazo[4,5-b]-pyridine (PhIP), while CA had the highest inhibition on 2-amino-3,8-dimethyl-imidazo[4,5-f]-quinoxaline (8-MeIQx) with an inhibition rate of 56%. The formation of total HAs in deep-fat fried chicken patties was significantly decreased by PA, CA and PS (P < 0.05). In deep-fat fried beef patties, CA had the strongest inhibition on PhIP, and, together with BL, exhibited better inhibition on 8-MeIQx than the other six antioxidants (P < 0.05). CA, BL and PS significantly inhibited the formation of total HAs (P < 0.05). In deep-fat fried pork patties, BL showed the strongest inhibitory effect on PhIP (with an inhibition rate of 64%) and all eight antioxidants significantly reduced the formation of 8-MeIQx and 2-amino-3,4,8-trimethyl-imidazo[4,5-f]-quinoxaline (4,8-DiMeIQx) (P < 0.05). BL had the highest inhibition against total HAs in deep-fat fried pork patties with an inhibition rate of 49%. Generally, BL, CA, PA, TP, RA and PS showed relative better inhibitory effects on the formation of HAs in deep-fat fried meat products.
Speciation Analysis of Phytosterols in Camellia Seed Oil and Their Dynamic Changes during Refining and Storage
JIA Wencong, FANG Enhua, WU Yifeng, XU Dunming, WANG Xiaoqin
2021, 42(16):  39-45.  doi:10.7506/spkx1002-6630-20200709-131
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Gas chromatography-mass spectrometry (GC-MS) was used for the speciation analysis of phytosterols in camellia seed oils from the 11 major producing regions in China, and the dynamic change of phytosterols during the refining and storage of camellia seed oils was investigated. The results showed that a total of nine sterols were detected at concentrations of 3 072.87–5 713.48 mg/kg in the oil samples, existing in bound and free forms, with the bound ones being dominant, accounting for 97.4%–99.4% of the total amount. The major sterols included lanosterol, β-amirin and β-sitosterol. After refining, the content of free sterols decreased by 94.1%, and the content of bound sterols decreased by 25.1%; the deacidification process affected both forms of sterols most. After storage, the contents of bound and free sterols decreased by 12.0% and 40.9%, respectively, suggesting that bound sterols showed stronger oxidation stability. Through principal component analysis (PCA), it was found that bound lanosterol and free β-sitosterol were the major characteristic components of camellia seed oil and were the most stable.
Effect of Replacement of Pork Back Fat by Konjac Glucomannan-Curdran Gum Composite Gel on the Quality Characteristics of Emulsified Sausages
YU Yimin, XIA Qiang, YANG Linlin, LIN Boyu, LU Yinyin, CAO Jinxuan, CAI Zhendong, PAN Daodong
2021, 42(16):  46-53.  doi:10.7506/spkx1002-6630-20210304-046
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The effects of replacement of pork back fat at levels of 0% (group G1), 33% (group G2), 66% (group G3) and 100% (group G4) with konjac glucomannan-curdran gum (KGM-CUD) composite gels on the quality characteristics of emulsified pork sausages were explored by measuring cooking loss, color difference, water-holding capacity, texture characteristics and lipid oxidation as well as sensory evaluation. The results showed that 0.3% KGM-CUD composite gel with a KGM:CUD ratio of 8:2 (m/m) exhibited the best emulsification effect. Compared with group G1, the cooking loss of groups G2 and G3 was significantly reduced (P < 0.05), while there was no significant difference in water-holding capacity (P > 0.05); the redness value of group G2 was significantly increased (P < 0.05); the redness and hardness values of group G3 were significantly increased (P < 0.05). With increasing replacement ratio, the antioxidant capacity of emulsified sausage was gradually increased. There was no significant difference in the microstructure of groups G2 and G3 when compared with group G1, while there were obvious spaces in the microstructure of group G4, showing slightly decreased overall acceptability. These results showed that when 0.3% KGM-CUD composite gel (KGM:CUD = 8:2) was used to replace 66% fat in emulsified sausages, the nutritional value and product quality of emulsified sausages could be improved, and the storage period could be significantly extended simultaneously.
Effects of Heating Temperature on Physicochemical Properties, Fatty Acids and Volatile Flavor Compounds of Fat from Horses Raised in Xinjiang
FU Chenggang, LIU Wenyu, CHEN Youzhi, LI Yumei, LI Huankang, ZHOU Jing, ZHANG Kongque, WEI Changqing
2021, 42(16):  54-60.  doi:10.7506/spkx1002-6630-20200628-363
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This study analyzed the changes in the physicochemical indexes, fatty acids and volatile compounds of the leaf fat of horses raised in Xinjiang after heating treatment at different temperatures of 100, 120, 140, 160, 180 and 200 ℃. The peroxide value (POV), p-anisidine value (p-AV), acid value (AV) and chromaticity values were measured, and the fatty acid composition and volatile compounds were determined using gas chromatography (GC) and headspace gas chromatography mass spectrometry (HS/GC-MS), respectively, sensory evaluation was performed and relative odor activity (ROAV) values were calculated. Results showed that the AV of horse fat heated at 160 ℃ was 1.62 mg/g, and it sharply increased when the heating temperature exceeded 160 ℃ while the p-AV remained stable. With increasing heating temperature, the POV increased signi?cantly and then decreased, reaching a maximum value of 0.124 g/100 g at 160 ℃. The percentage of polyunsaturated fatty acids in horse fat decreased from 20.87% to 14.54% with increasing temperature, 13.59%–20.06% of which was linoleic acid. In addition, 49, 50, 45, 47, 56 and 51 volatile substances were identified after heating at 100, 120, 140, 160, 180 and 200 ℃, respectively, with the major ones being aldehydes, alcohols, ketones, furans, acids and esters. Totally 11 key flavor compounds were eventually determined by principal component analysis (PCA) combined with ROAV values. Sensory evaluation showed that horse fat heated at different temperatures had significant differences in characteristic flavor properties such as fatty aroma and delicate fragrance (P < 0.05). The results from this study can provide a theoretical basis for the quality control and flavor improvement of horse fat.
Safety Evaluation and Probiotic Properties of Lactobacillus gasseri Isolated from Intestinal Tract of Infants
ZHOU Qinyu, XU Xilin, ZHAO Shan, HUANG Yanyan, KUANG Jiahua, HU Jinshuang, LIU Dongmei
2021, 42(16):  61-68.  doi:10.7506/spkx1002-6630-20200706-080
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The in vivo and in vitro safety and probiotic properties of Lactobacillus gasseri LGZ 1029, isolated from the intestinal tract of a 1-month-old baby in Guangzhou and identified by molecular biology methods were evaluated. The results showed that L. gasseri LGZ 1029 did not produce hemolytic toxin, and was sensitive to many kinds of antibiotics. It had no acute oral toxicity to mice and had good gastrointestinal tolerance and self-aggregation capacity. Its hydrophobicity (79.75%) was stronger than that (43.01%) of the commercial standard strain L. rhamnosus ATCC 7469. The diameter of inhibition zone of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 12598 when exposed to L. gasseri LGZ1029 was 17.31–20.70 and 21.71–31.08 mm, respectively, and the inhibitory effect was stronger than L. rhamnosus ATCC 7469. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of 1 × 107 CFU/mL L. gasseri LGZ 1029 was determined as 87.07%. These results may provide a theoretical basis for the application of L. gasseri LGZ 1029 in dietary supplements and dairy products manufacturing and its application as a bioprotective agent.
Isolation of 2-Phenylethanol-Synthesizing Bacteria and Synthetic Pathway Analysis
RONG Shaofeng, WU Jin, GUAN Shimin, CAI Baoguo, ZHANG Shuo, LI Qianqian
2021, 42(16):  69-75.  doi:10.7506/spkx1002-6630-20200515-174
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A bacterial strain was isolated from soil samples collected from the Gulf Forest Park in Shanghai. Biochemical identification and 16S rDNA sequence analysis indicated that the strain belonged to the genus Enterobacter and was designated as Enterobacter sp. MF024. Whole-genome sequence analysis showed that this strain had all key enzyme encoding genes involved in the Ehrlich pathway and de novo synthesis pathway for 2-phenylethanol. Then, biotransformation experiments were carried out using glucose as the carbon source and L-phenylalanine as the substrate. The key intermediates in the synthetic pathways such as phenylacetaldehyde and phenylpyruvate were further used as the substrates for validation experiments. Enterobacter sp. MF024 possesses both 2-phenylethanol synthesis pathways according to the results from gas chromatography-mass spectrometry and infrared spectrometry. The 2-phenylethanol yield was 0.56 g/L in the de novo synthesis pathway and 1.15 g/L in the Ehrlich pathway. This strain has great potential in the production of 2-phenylethanol by using glucose as the carbon source.
Interactive Effects of Addition of Bamboo Leaf Extract and Knockout of Transcriptional Factor DAL80 on Arginine Metabolism in Saccharomyces cerevisiae
LIU Xiaojie, LOU Hanghang, CHEN Qihe
2021, 42(16):  76-82.  doi:10.7506/spkx1002-6630-20210201-022
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In this study, the effects of addition of bamboo leaf extract (BLE) and knockout of the transcriptional factor DAL80 gene on the regulation of arginine (Arg) metabolism were investigated. It was found that both DAL80 knockout and BLE addition affected arginine metabolism, but by different mechanisms. DAL80 knockout could improve the transcriptional level of urea metabolism-related genes (DUR1,2, DUR3 and DAL82), accelerating the consumption of ethyl carbamate precursors by Saccharomyces cerevisiae to inhibit the formation of ethyl carbamate. BLE reduced the utilization of Arg by S. cerevisiae and consequently the synthesis of urea, finally reducing the formation of ethyl carbamate. When working simultaneously, BLE could weaken the inhibitory effect of DAL80 knockout, but the effect of DAL80 knockout on nitrogen metabolism in S. cerevisiae was still dominant.
Effects of Fermentation with Five Different Lactic Acid Bacteria on Physicochemical Properties and SensoryEvaluation of Kuqa Small White Apricot Juice
BAI Lin, Ruxianguli·MAIMAITIYIMING, WANG Xuguang, XU Bingjie, Abuduwufuer·RUOZI, Aihemaitijiang·AIHAITI
2021, 42(16):  83-88.  doi:10.7506/spkx1002-6630-20200628-362
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Five lactic acid bacteria including Pediococcus pentosaceus, Lactobacillus reuteri, L. rhamnosus, L. plantarum and L. acidophilus were individually used for the fermentation of Kuqa small white apricot juice. By comparing microbial and physicochemical characteristics (bacterial cell density, pH, total soluble solid (TSS) content and superoxide dismutase (SOD) activity) of the fermented juice samples during the fermentation process, and their sensory evaluation after completion of the fermentation, one or more suitable strains were selected for fermenting Kuqa small white apricot. The results showed that at the end of fermentation, the SOD activity of P. pentosaceus fermented apricot juice was 252.63 U/g, the number of viable bacterial cells was 8.07 (lg(CFU/mL)), the TSS content dropped to 17.1 °Brix, and the geometrical mean (GM) value of overall sensory evaluation score was the highest, 97%. The SOD activity of the apricot juice fermented by L. plantarum was 275.87 U/g, and the GM value of overall sensory evaluation score was 88%. L. acidophilus showed the fastest fermentation rate, with a final viable cell density of up to 9.95 (lg(CFU/mL)), and the TSS content in the apricot juice fermented by it dropped to 16.6 °Brix, while the GM value of overall sensory evaluation of the fermented juice was only 79%. In summary, P. pentosaceus was the most suitable strain for fermenting Kuqa small white apricot juice, followed by L. plantarum and L. acidophilus.
Component Analysis
Analysis of Characteristic Aroma Components of Different Grades of Yellow Tea
JIANG Ronggang, HUANG Yan, JIN Youlan, HUANG Fangfang, LIU Zhonghua, HUANG Jian’an, LI Qin
2021, 42(16):  89-98.  doi:10.7506/spkx1002-6630-20200709-137
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In this study, solid phase microextraction followed by gas chromatography-mass spectrometry (SPME-GC-MS), aroma activity value (OAV), sensory evaluation and chemometrics were used in combination for analysis of characteristic aroma components in different grades of yellow tea samples. The results showed that the characteristic aroma attributes of bud-type, bud-leaf-type, and multi-leaf-type yellow tea were described by sensory evaluation as ‘refreshing’, ‘refreshing and sweet’, and ‘crispy rice crust-like’, respectively; totally 100 volatile components were detected in the three degrades of yellow tea, with hydrocarbons being dominant in bud-type yellow tea, alcohols being dominant in bud-leaf-type yellow tea, and pyrrole and its derivatives being dominant in multi-leaf-type yellow tea. Based on OAV value and orthogonal partial least squares-discriminant analysis (OPLS-DA), 35 characteristic aroma components were identified in the three grades of yellow tea. Phenylacetaldehyde with a refreshing aroma was the major characteristic aroma component of bud-type yellow tea, ethyl hexanoate, benzyl alcohol, geraniol, phenethyl alcohol, citral, neral and myrcene with flowery, fruity and sweet aromas were the major characteristic aroma components of bud-leaf yellow tea, and 2-pyrrole formaldehyde, 3-ethyl-2,5-dimethylpyrazine, 2-ethyl-5-methylpyrazine and 2,3-diethyl-5-methylpyrazine with a roasted aroma were the major characteristic aroma ingredients of multi-leaf yellow tea.
Characterization of the Volatile Aroma Compounds of Qingke Baijiu Stored for Different Periods
QIN Dan, HE Fei, FENG Shengbao, LI Hehe, ZHANG Ning
2021, 42(16):  99-107.  doi:10.7506/spkx1002-6630-20200310-162
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The major volatile aroma compounds of Qingke Baijiu stored for different durations were characterized by direct injection (DI) or liquid-liquid microextraction (LLME) coupled with gas chromatography-mass spectrometry (GC-MS). Our experiment confirmed that addition of anhydrous sodium sulfate to the Baijiu sample before being injected into the GC-MS system did not cause losses of volatile aroma components. The contents of total esters and total alcohols as well as of ethyl acetate and ethyl lactate decreased gradually while the content of total acids increased gradually with the increase in storage duration. The content of acetic acid decreased most after one month, and then it increased gradually with the increase in storage duration. The content of acetic acid reached its maximum after 11 months. The contents of ethyl pentanoate and 4-ethylphenol reached their maximum after two months. The contents of benzaldehyde, acetoin, and furfural reached their maximum after nine months. The results of this study are expected to provide scientific data and theoretical support for the aging of Qingke Baijiu.
Effects of Different Processing Methods on the Flavor of Dairy Fan Evaluated Using GC-MS, GC-O and Electronic Nose
CHEN Chen, LIU Zheng, HUANG Ke, YU Haiyan, TIAN Huaixiang
2021, 42(16):  108-117.  doi:10.7506/spkx1002-6630-20200719-254
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In order to enrich the deep-processing theory of dairy fan and provide technical support and a theoretical guideline for the industrial production of dairy fan, gas chromatography-mass spectrometry (GC-MS), gas chromatography-olfactometry (GC-O) and fast gas chromatography-based electronic nose (fast?GC E-nose) were used to explore the effects of three processing methods including microwaving, frying and baking on the flavor of dairy fan in the present study. The correlation between sensory attributes and characteristic aroma compounds was also analyzed by partial least squares discriminant analysis (PLS-DA). The results showed that compared with the raw sample, microwave treatment led to a significant enhancement in the sour taste. Frying and baking caused a decrease in the overall aroma intensity but resulted in the formation of rich caramel-like and nutty aromas. All samples could be clearly distinguished by the electronic nose. A total of 67 volatile compounds were detected by HS-SPME-GC-MS in the four samples. In addition, 15, 16, 20, and 21 characteristic aroma compounds were identified through GC-O analysis and odor activity value (OAV) calculation. The contents of acidic compounds increased after microwave treatment. Although the flavor compounds reduced obviously after frying and baking, Maillard and caramelization reaction products occurred. PLS-DA analysis showed the correlations between seven sensory attributes and 19 characteristic aroma compounds. 2-Methylbutanal, 3-methylbutanal, 2-methylpyrazine and furfural played an important role in the formation of the caramel-like aroma of fried or baked dairy fan.
Analysis of Key Aroma Compounds in Kiwifruits
ZHAO Yu, ZHAN Ping, WANG Peng, TIAN Honglei
2021, 42(16):  118-124.  doi:10.7506/spkx1002-6630-20200831-406
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A total of 56 volatile compounds were identified in four varieties of kiwifruits by static headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). A total of 20, 17, 18 and 16 major aroma compounds in Actinidia deliciosa cv. Cuixiang (CX), A. deliciosa cv. Xuxiang (XX), A. deliciosa cv. Qinmei (QM) and A. chinensis cv. Huayou (HY) were determined by gas chromatography-olfactometry (GC-O), respectively. Among them, 16, 15, 14 and 13 key aroma compounds with aroma activity values (OAVs) greater than 1 were found in these varieties, respectively. These compounds were quantified by the standard curve method, and aroma reconstitution experiments were carried out. The results showed that the aroma profile of the reconstitution model was similar to that of kiwifruit samples, confirming the accuracy of determining the key aroma compounds. Finally, the key aroma compounds in each variety were successfully identified. Ethyl butyrate, ethyl caproate, unsaturated aldehydes with six carbon atoms, decenal, (E)-2-nonenal, (E,Z)-2,6-nondienal, hexanol, 1-octen-3-ol and 1-penten-3-one were common to all varieties.
Effect of Epicatechin on the Nutrient Content and Volatile Flavor Compounds of Beef Soup during Stewing
LI Yunlong, ZHAO Yueliang, FAN Daming, WANG Mingfu
2021, 42(16):  125-132.  doi:10.7506/spkx1002-6630-20200305-070
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The effect of epicatechin on the nutrient content and volatile flavor compounds of beef soup during stewing was investigated by routine chemical analysis, electronic nose and gas chromatography-mass spectrometry (GC-MS). It was found that epicatechin decreased the contents of total sugar and methionine, increased the contents of solids and unsaturated fatty acids in beef soup. The electronic nose results showed that epicatechin distinctively affected the odor profile of beef soup. A total of 21 volatile compounds were identified in beef soup samples with and without the addition of epicatechin. Compared with the control group, epicatechin increased the content of 2,4-di-tert-butylphenol, but decreased the content of hexanal, nonanal, dibutyl phthalate and hexadecane as well as the total contents of aldehyde and ester. The results from this study provide a theoretical basis for the application of epicatechin or epicatechin-rich spices in meat soup products.
Difference in the Composition of Baijiu Made from Single and Multiple Grains during Fermentation
YAN Han, FAN Wenlai, XU Yan
2021, 42(16):  133-137.  doi:10.7506/spkx1002-6630-20200311-181
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In order to explore the difference in the composition of multiple-flavor Chinese liquors produced from sorghum alone and in combination with rice, wheat, glutinous rice and corn, the volatile components in fermented grains were quantified by head space-solid phase microextraction (HS-SPME) or liquid-liquid microextraction (LLME) combined with gas chromatography-mass spectrometry (GC-MS). The results showed that 86 volatile compounds were detected in both fermented grains. The single fermented grain produced higher amounts of phenols and acids. The mixed fermented grain produced higher amounts of alcohols and nitrogen-contain compounds. By comparing the key differential compounds between both fermented grains, the single fermented grain produced higher levels of phenylacetaldehyde, and the multiple fermented grain produced higher levels of hexyl acetate, ethyl myristate, benzenemethanol, 6-methyl-2-ethylpyrazine and 2,3,5-trimethylpyrazine. The total concentration of pyrazines in the mixed fermented grain was significantly higher than that in the single fermented grain (P < 0.05). This could be a typical feature of the multiple fermented grain.
Comparative Analysis of the Contribution of Different Umami Substances to the Umami Taste of Dry-cured Spanish Mackerel (Scomberomorus niphonius)
HUANG Yuran, WANG Wei, ZHAO Wenhong, YANG Juan, LIU Qiaoyu, BAI Weidong
2021, 42(16):  138-144.  doi:10.7506/spkx1002-6630-20200903-033
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In this study, eight commercially available dry-cured Spanish mackerel were compared for difference in the composition and contents of umami substances. Besides, taste activity values (TAV) and monosodium glutamate (MSG) equivalents were calculated and analyzed to determine the substances that contribute the most to the umami taste of dry-cured Spanish mackerel. The results showed that the dry-cured Spanish mackerel had a prominent salty, umami and kokumi taste, and its umami taste was mainly imparted by glutamic acid, umami peptides, lactic acid and other umami or umami-enhancing substances. The TAV value of glutamic acid was greater than 1 (except for samples 3, 5, and 7), showing its outstanding contribution to the umami taste of dry-cured Spanish mackerel. The sensory analysis of the ultrafiltration components and study of the peptide molecular mass distribution showed that small peptides with a molecular mass of less than 1 000 Da had an important contribution to the umami taste of the product. In addition, long-term air-drying could promote the production of lactic acid and umami peptides, but with the loss of water, the bitterness and salty taste were enhanced; the auxiliary ingredients sucrose and liquor could inhibit the production of lactic acid, while sucrose could promote the production of glutamic acid to a certain extent. It is worth emphasizing that the nucleotides in the eight samples were degraded into bitter substances such as inosine (HxR) and hypoxanthine (Hx), and long-term air-drying may promote the accumulation of HxR and Hx.
Analysis of the Phenolic Profiles of Five Blending Grape Varieties
LU Haocheng, WEI Wei, CHENG Chifang, CHEN Wu, LI Shude, WANG Xiaojun, LIU Zongzhao, WANG Jun
2021, 42(16):  145-154.  doi:10.7506/spkx1002-6630-20200606-091
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This study aimed to explore the physicochemical properties and phenolic composition of the ripe berries of five color blending grape varieties, ‘Yan 73’, ‘Yan 74’, ‘Kolor’, ‘Tintorera’, and ‘Dornfelder’, and wines made from each variety by small-scale fermentation. The results showed that ‘Kolor’ and ‘Yan 73’ berries had higher contents of total anthocyanins than the other varieties, both exceeding 4 000 mg/kg fresh sample. ‘Tintorera’ and ‘Yan 73’ grapes had lower flavonol contents, which were 43.99 and 59.6 mg/kg fresh sample, respectively. The berry skin of ‘Dornfelder’ had the lowest flavanol content. Among the five varieties, the wine made from ‘Yan 73’ had the highest concentration of anthocyanins (1 827.87 mg/L), while the wine made from ‘Tintorera’ had the lowest concentrations of flavonols (19.87 mg/L), flavanols (35.34 mg/L), and phenolic acids (43.77 mg/L). Principal component analysis performed on anthocyanin contents in berries could distinguish most varieties. Furthermore, a model that was able to distinguish the berry skin and pulp of each variety well was established using orthogonal partial least squares-discriminant analysis (OPLS-DA). Most of the differentitial substances selected were F3’5’H hydroxyl substituted anthocyanins. A Pearson correlation coefficient model was constructed for the phenolic substances common to berries and wine, which showed that 70.37% of these substances had a strong correlation. The results from this study lay a foundation for dry red wine blending for the purpose of improving the color.
Comparative Study on Three Quantitative Analysis Methods for the Color Liupao Tea Infusion
MA Wanjun, MA Shicheng, SHI Jiang, LONG Zhirong, DONG Peng, ZHANG Yue, LIN Zhi, LÜ Haipeng
2021, 42(16):  155-161.  doi:10.7506/spkx1002-6630-20200315-237
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This study compared the difference in color parameters measured by different methods for tea infusion in order to explore a quantitative method that can reflect the color of tea infusion more objectively and truly. In total 36 Liupao tea samples were selected for preparation of tea infusions, and three different methods were used to extract color parameters from the tea infusions. The color parameters were simulated and verified for comparative analysis. The quantitative results of method 1 based on Adobe Color CC and method 2 based on Matlab for color parameters were generally consistent with each other, but significantly different from those of method 3 (direct measurement with a bench-top colorimeter). Correlation analysis of color parameters revealed that the difference was mainly attributed to the yellowness value. The results of artificial neural network (ANN) modeling showed that the prediction accuracies of the three methods for color parameters were 86.1%, 83.7% and 63.8%, respectively. The color parameter extraction method of image acquisition based on computer vision combined with Adobe Color CC could more truly reflect the actual color of Liupao tea, suggesting that this method provides a relatively objective and accurate detection method for the quantitative analysis of tea infusion color.
Determination of Monosaccharides, Disaccharide and Uronic Acids in Laminaria japonica by High Performance Anion Exchange Chromatography with Pulsed Amperometric Detection
YIN Dafang, SUN Xiaojie, GUO Yingying, LI Na, TIAN Yu, WANG Lianzhu
2021, 42(16):  162-168.  doi:10.7506/spkx1002-6630-20200706-068
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A high performance anion exchange chromatography with pulsed amperometric detection method was developed for qualitatively and quantitatively analyzed 11 sugars in Laminaria japonica hydrolysate, including fucose, glucose, galactosamine, glucosamine, galactose, mannose, fructose, ribose, lactose, galacturonic acid and glucuronic acid. The separation was carried out on a CarboPac PA10 anion-exchange column (250 mm × 4 mm) through gradient elution using a mobile phase consisting of water, 200 mmol/L NaOH and 500 mmol/L CH3COONa at a flow rate of 1 mL/min. The column temperature was set at 25 ℃. The correlation coefficients (R2) of the calibration curves for all analytes were higher than 0.998 6, and the detection limits (RSN = 3) were in range of 1.27–47.49 mg/kg. The precision expressed as relative standard deviations (RSDs) were smaller than 1.78% and the average spiked recoveries ranged from 89.35% to 115.67%. Therefore, the developed method is simple to operate, and highly linear, sensitive, precise and reproducible.
Separation and Identification of Metabolites and Metabolic Mechanism in Two Cultivars of Mung Bean
ZHANG Liyuan, YU Yingbo, ZHAO Ziying, YU Runzhong, LI Zhijiang, ZHANG Dongjie
2021, 42(16):  169-175.  doi:10.7506/spkx1002-6630-20200303-044
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Based on metabonomics, the metabolites in two mung bean cultivars (Daming and Jiulihu) were isolated and identified by gas chromatography-mass spectrometry (GC-MS). The polar metabolits were extracted with aqueous methanol solution and then derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) before being analyzed by GC-MS. The results showed that a total 67 metabolites were identified in the mung bean cultivars, 30 of which were found to be common to be both, but at different levels. Ten differential metabolites were identified in Daming mung beans compared with Jiulihu mung beans, and 20 differential metabolites in Jiulihu mung beans compared with Daming mung beans. The metabolic pathways of sugar, fatty acid, amino acid and TCA in Jiulihu mung beans were more active than in Daming mung beans. The dominant metabolites (> 7%) in Daming mung beans were L-norvaline and inositol. The dominant metabolites in Jiulihu mung beans was L-norvaline. We speculated that the difference in the metabolite composition between the two cultivars may be related to the difference in genes, metabolic pathways and other factors.
Analysis of Volatile Components in Three Varieties of Kumquat by Headspace Solid Phase Microextraction-Gas Chromatography-Mass Spectrometry
HU Ziyan, LIU Wei, HE Shuang, HU Xiaoqin, ZHANG Juhua, SHAN Yang
2021, 42(16):  176-184.  doi:10.7506/spkx1002-6630-20200821-290
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In this study, the aroma components of kumquats were analyze by headspace solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) combined with multivariate statistics. The optimal SPME conditions were determined as follows: DVB/CAR/PDMS fiber as extraction fiber, extraction temperature 40 ℃, extraction time 70 min, sample mass 3.0 g, and desorption time 5 min. A total of 76 volatile organic compounds (VOCs) belonging to six classes (terpenes, alcohols, aldehydes, esters, ketones and alkanes) were identified in three varieties of kumquat (Yangshuo Cuipi, Liuyang Jindan and Rongan Huapi), among which terpenes were the most abundant. In addition, 62, 58 and 48 aroma-active compounds were detected in Liuyang, Yangshuo and Rongan kumquats, respectively. Alloaromadendrene, 4-carene, α-selinene, (-)-aristolene, trans-(+)-isolimonene, carveol and (+)-dihydrocarvone were the unique aroma compounds in Liuyang Jindan kumquats. 2-Carene, trans-calamene, dodecanal and undecane were the unique aroma compounds of Yangshuo Cuipi kumquats. The unique aroma compounds of Rongan Huapi kumquats were limonene oxide, eremophilene, β-guaiene, β-terpinene, β-ocimene and dihydrocarvone. According to odor activity values (OAVs), myrcene, (d)-limonene, linalool, decanal and perillaldehyde may be important aroma components of kumquats. Principal component analysis (PCA) and cluster analysis (CA) were effective to distinguish the kumquat varieties based on the VOCs data. These results can provide a theoretical basis for the studies of kumquat flavor, quality and geographical origin identification.
Comparison of Volatile Components and Characterization of Key Aroma Components of Walnut Oil Produced by Different Processes
LI Huankang, YANG Jiawei, LIU Wenyu, WEI Changqing
2021, 42(16):  185-192.  doi:10.7506/spkx1002-6630-20200901-006
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Walnut oils were prepared by three different processes: organic solvent extraction, cold pressing and hot pressing with different roasting treatments, and their volatile compositions were determined by headspace-gas chromatography-mass spectrometry (HS-GC-MS). The difference in their key aroma components was clarified by principal component analysis (PCA) and clustering heat map analysis based on relative odor activity value (ROAV). The results showed that there were significant differences (P < 0.05) in the volatile composition of the walnut oils prepared by different processes. A total of 92 volatile substances were identified in 11 walnut oil samples, mainly including aldehydes, hydrocarbons, alcohols and oxygenated heterocycles, with trans-2-heptenal (21.00%–28.61%), n-hexanal (15.09%–20.72%) and cis-2-octene (9.77%–16.28%) being dominant in the pressed oil, while n-hexanal (35.79%), trans-2-heptenaldehyde (13.46%) and valeraldehyde (11.79%) being dominant in the extracted oil. Through PCA based on ROAVs, nonanal (fatty, citrus-like and grassy flavor), trans-2-nonanal (cucumber-like, fatty and grassy flavor), trans,trans-2,4-decadienal (deep-fat fried, waxy, and fatty flavor) and 1-octen-3-ol (mushroom-like flavor) were identified as the key aroma components in walnut oil. The clustering heat map indicated a significant color difference among the walnut oil samples prepared by different processes, indicating that it was feasible to distinguish walnut oils prepared by different processes based on volatile substances.
Analysis of Volatile Components in Essential Oil of Fingered Citrons Citrus medica L. var. sarcodactylis Swingle Harvested in Guangdong Province at Different Times by GC-MS and GC-IMS
TANG Niang, LIU Jingyi, CHEN Xiao’ai, YANG Yujie, CHEN Shuxi, ZHANG Ziming, ZHOU Aimei
2021, 42(16):  193-202.  doi:10.7506/spkx1002-6630-20200618-244
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In this study, the essential oil content and composition of fingered citrons harvested in Guangdong province in different months of the same year were analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-ion mobility spectrometry (GC-IMS). The results showed that the essential oil content of fingered citrons peaked in September. GC-MS and GC-IMS identified 54 and 61 volatile components in the essential oil of finger citrons harvested at five different times, respectively, with terpenes being the dominant ones, followed by alcohols, aldehydes and esters. GC-MS indicated that alcohols, aldehydes, esters, alkanes and phenols mainly existed in the samples harvested in August and September at low levels. GC-IMS demonstrated that aldehydes, esters and acid compounds were mainly found in the samples harvested in June, July and August. Two chemometric methods, heat map clustering and principal component analysis, were used to distinguish the essential oils from fingered citrons harvested at five different times. The results of GC-MS and GC-IMS showed differences from each other. Most of the volatile components detected by GC-MS were larger molecules (C9–C21) at high levels, while most of the volatile components detected by GC-IMS were smaller molecules (C2–C10) at low levels. The combined application of both technologies expanded the scope of detectable volatile components in the essential oil from fingered citrons and could provide a scientific basis for the quality identification of the essential oil and the selection of optimal harvest time for fingered citrons.
Comprehensive Evaluation of 14 Edible Mushroom Varieties from the Chinese Market Based on Amino Acid Contents
WANG Liyan, JING Ruiyong, GUO Yongxia, WANG Xinmiao, ZHAO Xingjian, SONG Weimin, YANG Jiani, WEI Jiaqi
2021, 42(16):  203-208.  doi:10.7506/spkx1002-6630-20200302-025
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To study the difference in amino acid contents of different edible mushroom varieties, the contents of 17 amino acids in 14 edible mushroom varieties from the Chinese Market were determined by an automatic amino acid analyzer and the data obtained were analyzed by principal component analysis (PCA). Further, comprehensive evaluation of these mushroom varieties was conducted by using the subordinate function method, and they were classified by clustering analysis. The results showed that four principal components were extracted, cumulatively explaining 86.909% of the total variance. Met, Lys, Val, Pro, His, Thr, Lys, Ile and Cys were selected as comprehensive evaluation indexes by comprehensive analysis. The decreasing order of the quality of the tested mushroom varieties as evaluated by the subordinate function method were as follows: Copyinds comatus (Muii. Fr) Gray > Agaricus bisporus > Pleurotus eryngii > Agrocybe cylindracea > Volvariella volvacea (Bull.:Fr.) Sing. > Lentinus edodes (Berk.) Sing > Hypsizygus marmoreus (Peck) H.E. Bigelow > Stropharia rugoso-annulata Farlow apud Murrill > Flammulina velutipes > P. citrinopileatus > Russula pseudodelica Lang > P. tuber-regium (Fr.) Sing = Oudemansiella radicata > P. ostreatus. Clustering analysis showed that the mushroom varieties were clustered into three groups. Group I included C. comatus (Muii. Fr) Gray, A. bisporus, P. eryngii and Agrocybe cylindraceachashugu. Group II included V. volvacea (Bull.:Fr.) Sing., L. edodes (Berk.) Sing, H. marmoreus (Peck) H.E. Bigelow, S. rugoso-annulata Farlow apud Murrill, F. velutipes, P. citrinopileatus, R. pseudodelica Lang, P. tuber-regium (Fr.) Sing, and O. radicata. Group III included P. ostreatus. The highest, intermediate and lowest comprehensive scores were observed for groups I, and II and III, respectively.
Aroma Networking of Cherries Based on Gas Chromatography-Mass Spectrometric Data and Sensory Evaluation
QIU Shuang, TANG Fei, LIU Chang, XIE Meilin, WEI Yangji, LI Jingming
2021, 42(16):  209-217.  doi:10.7506/spkx1002-6630-20200709-129
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In order to evaluate the potential of instrumental analysis to replace sensory analysis for food aroma evaluation by combining instrumental and sensory analysis results, the aroma characteristics of nine cherry cultivars were analyzed by gas chromatography-mass spectrometry (GC-MS) and sensory evaluation. The Pearson correlation coefficients between the GC-MS and sensory data were calculated to build an aroma network. According to the Pearson correlation coefficient between the sensory evaluation and GC-MS results, partial least square regression (PLSR) was used to verify the reliability of the established aroma network. The results of Pearson correlation analysis and the aroma network diagram showed that the sensory attributes of cherry aroma were significantly related to a variety of aroma substances identified by GC-MS analysis. Similarly, PLSR analysis showed that the citrus-like, lemon-like, almond-like, rosy and wine-like cherry aroma attributes could be well explained by the results of GC-MS analysis. It was proved that the aroma network was feasible to combine the sensory evaluation results of aroma with the results of GC-MS. It is considered that GC-MS analysis, an objective and easy-to-standardize aroma evaluation method, has the potential to replace sensory analysis in the study of fruit aroma.
Safety Detection
Magnetic Separation Combined with Laser Induced Fluorescence for Detection of CP4-EPSPS Gene
PANG Yuehong, WANG Yiying, SUN Mengmeng, SHEN Xiaofang, ZHANG Yi
2021, 42(16):  218-223.  doi:10.7506/spkx1002-6630-20200526-310
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A laser-induced fluorescence (LIF) combined with magnetic separation sensing method was established for the online detection of the CP4-5-enol acetate-3-phosphate synthase gene (CP4-EPSPS). Amino magnetic nanoparticles (MNPs) were used as the vector to modify cDNA, construct gene capture probes, and design 5-carboxyfluorescein (FAM)-labeled signal gene probes (sDNA). In the presence of the CP4-EPSPS gene probe (tDNA), cDNA and sDNA combined with tDNA to form a double-stranded structure through complementary base pairing. The construction could be enriched and separated by a magnetic field when passing through the capillary, and then its fluorescence signal could be detected online by a laser-induced fluorescence detector. At optimized concentrations of MNPs, cDNA and bovine serum protein, the concentration of the CP4-EPSPS gene in the range of 1.0 × 10-11–2.0 × 10-7 mol/L had a good linear relationship with the fluorescence peak area, and the limit of detection (LOD) was 4.0 × 10-12 mol/L (RSN = 3). This method could be successfully applied to the detection of polymerase chain reaction (PCR) amplification products of genetically modified soybeans.
Rapid Detection of Cronobacter sakazakii in Powdered Infant Formula by Immunomagnetic Separation Coupled with Visual Nanogold Hybridization Probe
JIANG Yujun, YANG Tao, MAN Chaoxin, ZHOU Wenqi, WANG Rui, CHEN Sihan, YANG Xinyan, FU Shiqian, GAO Pingping, REN Yuwei, ZHANG Wei
2021, 42(16):  224-232.  doi:10.7506/spkx1002-6630-20200529-355
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A rapid and sensitive assay for detecting Cronobacter sakazakii in powdered infant formula (PIF) was developed by utilizing immunomagnetic separation (IMS) combined with visual gold nanoparticle (GNP) hybridization probe. C. sakazakii was captured via antibody-functionalized magnetic particles (MPs) and the polymerase chain reaction amplicon of the target bacteria was analyzed by GNP instead of traditionally used electrophoresis. Immunomagnetic particles (IMPs) were obtained by mixing together 100 μL of MPs, 120 μL of carbodiimide hydrochloride (EDC) and 80 μL of monoclonal antibody against C. sakazakii with 0.02% (V/V) added Tween-20. Specificity test showed positive results only for C. sakazakii. C. sakazakii could be detected at 102 CFU/mL and 103 CFU/g in pure culture and artificially contaminated PIF without pre-enrichment, respectively. After 3 h of pre-enrichment, this assay was able to detect as low as 4.5 × 101 CFU/g of C. sakazakii in PIF. The results of the visual assay were consistent with those of electrophoresis and ultraviolet scanning spectroscopy. Therefore, the IMS-GNP probe assay proved to be an alternative to gel electrophoresis for the rapid detection of C. sakazakii in PIF samples.
Whole Genome Sequencing and Analysis of Pseudomonas fragi NMC25 from Chilled Chicken
WANG Guangyu, QIU Weifen, XU Xinglian, ZHOU Guanghong
2021, 42(16):  233-238.  doi:10.7506/spkx1002-6630-20200526-305
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In the present study, the whole genome sequencing of Pseudomonas fragi NMC25, a strain isolated from spoiled chilled chicken, was carried out using the PacBio RS II platform. The sequencing data were subsequently assembled, predicted, and annotated. Meanwhile, a preliminary comparative genomic analysis was conducted with the published genomes of P. aeruginosa PAO1, P. putida KT2440, P. fluorescens F113, and two other P. fragi isolates (P121 and NRRLB-727). The results showed that the genome size of P. fragi NMC25 was 5.152 13 Mb with GC content of 59.21%, and the genome contained one chromosome and three plasmids. A large number of spoilage-related genes were annotated in the genome by comparison with the COG, GO, KEGG, and CAZy databases. A low level of genome synteny between P. fragi NMC25 and three other Pseudomonas spp. was found in the comparative genomic analysis. Moreover, the synteny between NMC25 and P121 was less than 70%, indicating that the genomes of P. fragi isolated from different sources were quite different from each other. The genetic data demonstrated that P. fragi NMC25 had strong spoilage potential. These findings are helpful for in-depth understanding the metabolic characteristics of P. fragi and provide theoretical support for elucidating the mechanism of chilled chicken spoilage caused by P. fragi.
Detection of Listeria monocytogenes in Foods by Visual Saltatory Rolling Circle Amplification
YUAN Ning, ZHANG Yunzhe, ZHANG Haijuan, YU Ze, LU Xin, ZHANG Wei
2021, 42(16):  239-245.  doi:10.7506/spkx1002-6630-20200130-290
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In this study, a novel method for the detection of Listeria monocysteia was established using visual saltatory rolling circle amplification (SRCA). According to the hlyA gene sequence of L. monocytogenes, primers were designed. The specificity, sensitivity and detection limit for artificial contaminated samples were determined. In addition, the sensitivity, specificity and accuracy of SRCA were evaluated by applying it to detect 70 actual food samples. Results showed that the developed method gave positive results for all L. monocytogenes strains and negative results for non L. monocytogenes strains, indicating good specificity of the assay. The sensitivity of the SRCA method was 8.9 × 100 fg/μL, and the detection limit was 2.8 × 100 CFU/g, which were 1 000-fold better than those of polymerase chain reaction (PCR). Compared with the national standard method GB 4789.30-2016, the relative sensitivity, specificity and accuracy of SRCA were 100.00%, 97.01% and 97.14%, respectively. In summary, this method has the advantages of easy operation, simple equipment, strong specificity, high sensitivity, low detection limit and low cost, and can be widely used in grass-root inspection and testing institutions and small- and medium-sized food companies.
Comparison of Six Methods for Extraction of Genomic DNA from Edible Spices
ZHOU Mengyue, XING Ranran, WANG Nan, GE Yiqiang, CHEN Ying
2021, 42(16):  246-253.  doi:10.7506/spkx1002-6630-20200116-203
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In this study, we compared six different DNA extraction methods, including TIANGEN plant genomic DNA kit, TIANGEN DNAsecure plant kit, QIAGEN DNeasy plant kit, Nucleospin? Food kit, modified cetyltrimethylammonium bromide (CTAB) method, and sodium dodecyl sulfate (SDS)-CTAB method by examining their effectiveness for extracting DNA from 19 edible spices from plant roots, stems, leaves, buds, fruits, and seeds. The results showed that the DNAs obtained by the QIAGEN DNeasy plant kit and the TIANGEN plant genomic DNA kit were most successfully amplified by polymerase chain reaction (PCR). However, the QIAGEN DNeasy plant kit yielded a low DNA concentration, being unfavorable for subsequent studies. Therefore, we recommended that the TIANGEN plant genomic DNA kit should be preferably used for the extraction of genomic DNA from edible spices and DNA from commercial spice powder. The results showed that the concentration, purity and PCR amplification efficiency of DNA extracted from all commercial spice powders met the experimental requirements. Moreover, the sample amount and lysis time should be increased for DNA extraction from bark and hard edible spices using the TIANGEN plant genomic DNA kit.
Comparative Analysis of Pork Freshness and Spoilage Based on Hyperspectral Reflection Characteristics
ZHUANG Qibin, ZHENG Xiaochun, YANG Deyong, PENG Yankun
2021, 42(16):  254-260.  doi:10.7506/spkx1002-6630-20200310-156
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The quality change of pork during storage was evaluated by measuring the changes in total volatile basic nitrogen (TVB-N) content and total viable count (TVC). The results showed that TVB-N content of pork refrigerated for up to 15 days at 4 ℃ exhibited a J-shaped curve, while TVC exhibited an S-shaped curve. On day 15, TVB-N content reached the maximum limit for freshness stipulated in the national standard (15 mg/100 g), while TVC reached 7.92 (lg(CFU/g)), far higher than the maximum limit stipulated in the national standard, 6 (lg(CFU/g)). While TVC reached 6 (lg(CFU/g)) on day 5.5, TVB-N content was only 10.65 mg/100 g. Pork meat judged to be spoiled meat based on TVC was found to be still fresh according to TVB-N content. Furthermore, visible short-wave near-infrared hyperspectral reflection technology was used to collect hyperspectral data for pork samples, and partial least squares regression (PLSR) models for the prediction of TVB-N content and TVC were established using different spectral pretreatments. The results showed that the model established using multiplicative scatter correction (MSC) preprocessing displayed the best prediction performance for TVB-N content, while the model established using first derivative preprocessing exhibited the best prediction performance for TVC. The correlation coefficients of prediction set (Rp) were 0.957 2 and 0.968 2, the standard errors of prediction (SEP) were 2.802 5 mg/100 g and 0.332 7 (lg(CFU/g)), the relative percent deviation (RPD) was 3.093 7 and 3.434 1, the correlation coefficients of external validation set were 0.928 3 and 0.930 5, and the standard errors were 3.556 2 mg/100 g and 0.515 7 (lg(CFU/g)) for the TVB-N and TVC prediction models, respectively. In conclusion, this study can provide a theoretical basis for better application of hyperspectral technology in pork quality detection.
Analysis of Cortisone and Cortisol in Beef and Milk
YANG Yi, YIN Jie, YANG Yunjia, ZHANG Jing
2021, 42(16):  261-266.  doi:10.7506/spkx1002-6630-20210209-147
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Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to analyze the occurrence of cortisone and cortisol in beef and milk marketed in some regions of China. Homogenized samples were digested in acetic acid-sodium acetate buffer, and extracted with methanol. Then, the extract was purified on graphitized carbon black (GCB) and amino (NH2) solid phase extraction (SPE) catrideges. The eluate was pooled and blown to dryness by N2, and the residue was redissoved in methanol-water mixture before being analyzed by LC-MS/MS. Data analysis was carried out using SPSS version 21.0. A total of 346 beef and milk samples from nine provinces and municipalities in China were analyzed by LC-MS/MS. Cortisone and cortisol were detected in both beef and milk with detection rates ranging from 86.1% to 100.0% at concentration levels of 0.02–74.88 μg/kg. The mean (median) contents of cortisone and hydrocortisone in beef were 1.69 (1.14) and 12.16 (8.14) μg/kg, respectively, and the mean (median) contents of cortisone and hydrocortisone in milk were 0.23 (0.23) and 0.72 (0.72) μg/kg, respectively. The contents of hydrocortisone and cortisone in beef and milk were significantly positively correlated with each other.
Rapid Detection of Nitrite in Meat Products by in-Situ Synthesized Cu-Based Metal Organic Frameworks Coupled with Differential Pulse Voltammetry
XU Yiwei, ZHU Dan, SHI Jiyong, ZHANG Wen, WANG Xin, LIU Chao, LI Wenting, ZOU Xiaobo
2021, 42(16):  267-272.  doi:10.7506/spkx1002-6630-20200717-228
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In order to develop a method for rapid determination of nitrite in meat products, Cu-based metal organic frameworks (Cu-MOFs) were synthesized electrochemically, which were found to be uniformly distributed on the surface of a glassy carbon electrode (GCE). The scanning electron microscopic (SEM) images exhibited that Cu-MOF particles were octahedral. NO2- lost an electron to become oxidized. According to the current signal produced by electron transfer, NO2- could be quantitatively detected. The modified Cu-MOFs could catalyze the oxidation of NO2-, thereby contributing to increased response signal from the working electrode and improving the sensitivity of NO2- detection. NO2- concentration was measured by differential pulse voltammetry using Cu-MOFs/GCE. The peak current increased linearly with the NO2- concentration in the range of 10–1 200 μmol/L. The limit of detection was 1.57 μmol/L. Besides, the prepared electrochemical sensor exhibited good selectivity and stability. The results of the sensor for the nitrite content in meat products were in good agreement with those obtained by the naphthyl ethylenediamine dihydrochloride spectrophotometric method, indicating that the electrode has great potential in the analysis of nitrite in food samples.
Isolation and Identification of Fungal Contaminants and Analysis of Mycotoxin Content in Fresh Corn during Grain Development
ZHANG Nana, CHEN Lirong, ZHANG Shoumei, GUO Yuqiu, LIU Kaichang, GONG Kuijie
2021, 42(16):  273-280.  doi:10.7506/spkx1002-6630-20200313-206
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In order to investigate fungal contamination and the accumulation of fungal toxins in fresh corn during seed development, three cultivars, ‘Tianzi 23’, ‘Jingkenuo 2000’ and ‘Heinuo 6’ were selected. Fungi were isolated and identified at 0, 12, 23, 35 and 55 days after pollination, and the contents of aflatoxin B1, deoxynivalenol and zearalenone in corn samples were determined. A total of 1606 fungal strains were isolated from the three cultivars of fresh corn, belonging to 20 species and 13 genera. During corn kernel development, the major fungal contaminants were Penicillium, Aspergillus, Fusarium, Mucor and Talaromyces, followed by Alternaria, Rhizopus, Sarocladium and Choanephora as well as lesser quantities of Phoma, Nigrospora, Lichtheimia and Cladosporium. The contents of aflatoxin B1, deoxynivalenol and zearalenone were the lowest at 23 days after pollination, suggesting the best suitability for consumption. The number of fungal contaminants was not correlated with the accumulation of toxins. ‘Heinuo 6’ had the lowest mycotoxin content, followed by ‘Tianzi 23’ and ‘Jingkenuo 2000’. Mycotoxin contents in the three cultivars were far lower than the residue limit.
Determination of Eight Biogenic Amines in Huangjiu (Rice Wine) by Ultra-high Performance Liquid Chromatography-Tandem Mass Spectrometry
WANG Keli, YE Tai, XU Fei, CAO Hui, YUAN Min, YU Jinsong, YIN Fengqin, WU Xiuxiu
2021, 42(16):  281-285.  doi:10.7506/spkx1002-6630-20200716-223
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An ultra-high performance liquid chromatography-tandem mass spectrometry method for the determination of eight biogenic amines in Huangjiu (rice wine), including histamine, tyramine, putrescine, tryptamine, β-phenylethylamine, cadaverine, spermine and spermidine, was established. Complete separation of the derivatives of eight biogenic amines was achieved on a C18 chromatographic column (100.0 mm × 2.1 mm, 1.7 μm) by gradient elution with acetonitrile-0.1% formic acid in water as the mobile phase. Mass spectral data were obtained in the multi-reaction monitoring mode by electrospray positive ion scanning. The internal standard method was employed for quantification. The results showed that the eight biogenic amines were separated completely within 19 min?and good linearity was obtained for histamine in the range of 2–1 000 ng/mL and for other amines in the range of 1–1 000 ng/mL (r2 > 0.995 1). The limit of detection (LOD) and the limit of quantification (LOQ) of the method were in the range of 0.25–0.5 and 1–2 ng/mL, respectively. The intraday and interday precision of the proposed method was in the range of 0.61%–5.68% and 0.82%–5.00%, respectively. Satisfactory recoveries for spiked rice wine samples were obtained in the range of 83.56%–117.45% with relative standard deviation (RSD) lower than 6.69%.
Establishment of a Rapid Detection System for Cronobacter spp.
WANG Dandan, LI Li, YANG Yange, LIU Mingchang, WANG Hongyue, WU Shuqing, YUAN Fei, WU Yajun
2021, 42(16):  286-292.  doi:10.7506/spkx1002-6630-20200210-079
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In this article, two typical model strains of Cronobacter spp. (Cronobacter malonaticus and Enterobacter sakazakii) were used to establish a rapid detection system integrating one-step DNA extraction and rapid real-time polymerase chain reaction (real-time PCR) for Cronobacter spp.. The amplification time of the optimized fast real-time PCR was only 27 min 18 s compared to 82 min for the common procedure. in the one-step DNA extraction procedure, DNA could be directly obtained after thermal cyclic reaction for only 12 min. Compared with the traditional boiling method, the rapid detection method showed consistent sensitivity to pure culture and artificially contaminated samples cultured for 6 h. The sensitivity of the new method to artificially contaminated samples cultured for 7 and 8 h was one order of magnitude lower than that of the conditional method. The method presented in this study is fast, simple, and highly sensitive, and has a good application prospect in the rapid on-site detection of foodborne pathogens at ports.
Analysis of Metabolic Markers in Chilled Chicken Based on Liquid Chromatography-Quadruple Time-of-Flight Mass Spectrometry
WANG Kewen, XU Lei, XU Zhenzhen, WANG Xue, YANG Shuming
2021, 42(16):  293-303.  doi:10.7506/spkx1002-6630-20200827-377
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Liquid chromatography-quadruple time-of-flight mass spectrometry (LC-QTOF-MS) combined with orthogonal partial least square (OPLS) was used for metabolite analysis in chilled chicken (stored for 1, 3, 5, 7 and 10 days) and fresh chicken. Twenty-nine differential compounds including amino acids, peptides, fatty acids and nucleotides were obtained in the experiment. With increasing storage period, the contents of phenylalanine, tryptophan, palmitic acid and eicosatetraenoic acid were significantly increased, while the contents of L-carnosine, L-anserine and 5’-IMP were significantly decreased. Moreover, chilled chicken stored for less than 5 days had more similarity with fresh chicken in metabolite composition. This study indicates that it is feasible to discriminate chilled from fresh chicken using metabolomics based on LC-QTOF-MS combined with OPLS model, which provides a novel idea for exploring metabolites in chilled chicken, and provides data support for the quality control and evaluation of chilled chicken.
Stable Isotope Fingerprinting of Salmon from Different Geographical Origins and Geographical Origin Traceability Analysis
WU Hao, ZHOU Xiuwen, CHEN Haiquan, JIN Baohui, YAN Zhi, ZHAO Xu, XIE Liqi, ZHAO Yan, LIN Guanghui
2021, 42(16):  304-311.  doi:10.7506/spkx1002-6630-20200723-321
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A total of 16 salmon samples from the major salmon exporters (Faroe Islands, Norway, Chile, Canada, and Australia) to China collected at Shenzhen Port, together with two rainbow trout samples produced in China, were analyzed for carbon, nitrogen, hydrogen, oxygen, sulfur stable isotope ratios in the muscle, skin, scales, and bones. The difference in isotopic distribution among tissues and geographical origins was compared. The discriminant analysis (DA) was employed for differentiating salmon from different geographical origins. There were significant differences in the isotopes of carbon, nitrogen, sulfur and hydrogen and oxygen among salmon from different geographical origins. Obvious isotopic fractionation effect was observed among different tissues. The scale and skin isotope ratios were more effective geographical origin indicators than the muscle and bone isotope ratios. The DA results showed that stable isotopes could be used to completely discriminate among the five geographical origins of salmon and also to distinguish Chinese rainbow trout from imported salmon. The geographical origins of six salmon samples randomly purchased from the market were successfully traced by the stable isotope technique. The method developed in this study can be used to trace the geographical origin of salmon products, which will provide technical support for ensuring food safety and consumer health.
Multiple Real-time Polymerase Chain Reaction for Identification of Animal-derived Ingredients in Milk Products from Minor Dairy Species
YANG Yange, LI Li, WANG Dandan, LI Weixi, WANG Hongyue, LIU Mingchang, WU Yajun
2021, 42(16):  312-321.  doi:10.7506/spkx1002-6630-20200407-080
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The aim of this study was to establish a multiple real-time polymerase chain reaction (real-time PCR) method for the rapid identification of animal-derived ingredients in milk products from minor dairy species. A multiple real-time PCR system was developed for eight dairy animal-derived ingredients, which allowed for the simultaneous detection of four target genes. The absolute sensitivity was 0.1–5 pg/μL and the limit of detection (LOD) was 0.1%. Besides, an efficient DNA extraction method for dairy products was established, and DNA extraction from 96 samples could be completed within 12 min after sample lysis, greatly shortening the sample pretreatment time. By using this method, we surveyed commercially available dairy products from minor dairy species, revealing that 36.36% of the samples were inaccurately labelled.
Influence of Geographical Origin, Variety and Crop Year on Mineral Element Contents of Rice and Geographical Origin Discrimination Based on Mineral Elements
QIAN Lili, QIU Yanchao, LI Dianwei, FU Lixue, ZHANG Dongjie, ZUO Feng
2021, 42(16):  322-327.  doi:10.7506/spkx1002-6630-20200730-396
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The effects of variety, crop year, geographical origin and their interaction on rice mineral element contents were investigated to select the characteristic mineral elements for geographical origin discrimination by statistical analysis. A total of 90 field test samples were obtained from nine varieties planted in Chahayang, Wuchang and Jiansanjiang in three consecutive years from 2016 to 2018, and 52 mineral elements in the samples were determined by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that Mg, Ca, Cr, Mn, Zn, As, Rb, Sr, Ag, Cd, Ba, La, Sm, Dy, Ho, Er, Pb and U were greatly affected by geographical origins. Na, Mg, Al, Ca, Pb, U and V were significantly affected by crop years. Na, Cr, Co, Ni, Tl, U, Mg, Al, La and Ho were greatly affected by varieties. Principal component analysis (PCA) and discriminant analysis (DA) were carried out on 18 mineral elements found to be directly related to geographical origins. The cumulative contribution rate of the first six principal components was 80.333%. The accuracy of the developed discriminant model in distinguishing three producing areas was 100% and the cross validation accuracy was also 100% corroborating that the model can allow correct discrimination of samples.
Rapid Detection of Polar Components of Used Frying Oils by Raman Spectroscopy
LI Ruiwen, SUN Xiaorong, LIU Cuiling, GUO Zehan, TIAN Mi
2021, 42(16):  328-332.  doi:10.7506/spkx1002-6630-20200729-372
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In order to detect the content of polar components in used frying oils quickly and non-destructively, we acquired Raman spectra of used frying oil samples collected at different frying times. To create a predictive model for determining the content of polar components in used frying oils with high stability, small errors and high precision, the influence of different spectral preprocessing methods on the performance of predictive models was evaluated, and partial least squares regression analysis regression (PLSR) modelling was carried out to select the optimal spectral preprocessing method. The experimental results showed that the optimal PLSR model was obtained using standard normal transformation with root mean square error of prediction (RMSEP) of 1.18 and correlation coefficient of 0.940 4. Subsequently, the spectral data preprocessed by the standard normal transformation were used to establish a neural network model by error back propagation (BP) and radial basis function training (RBF), separately. The BP neural network model had the best prediction performance with RMSEP of 0.032 6 and correlation coefficient 0.972. The above findings demonstrate that this method can be used for the rapid analysis of polar components of used frying oils.
Dynamic Matrix Solid Phase Dispersion-Ionic Liquid-Based Aqueous Two-Phase Microextraction Combined with High Performance Liquid Chromatography for the Determination of Triazine Herbicides in Cereals
XU Weili, ZHU Qing, WANG Xiujuan, LI Jilong, FENG Ji, BI Jinlong, WANG Zhibing
2021, 42(16):  333-341.  doi:10.7506/spkx1002-6630-20200711-152
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An efficient, green and fast dynamic matrix solid phase dispersion coupled with ionic liquid-based aqueous two-phase microextraction system was developed and applied to the determination of five triazine herbicides in cereals, including simetone, atraton, terbuthylazine, dipropetryn and terbumeton by high performance liquid chromatography (HPLC). In this method, after pretreatment by matrix solid phase dispersion, the ionic liquid-based aqueous two-phase microextraction system was used for the enrichment of the target analytes. The Plackett-Burman design was used to identify factors that could significantly affect the average recovery of the analytes, which were subsequently optimized using the Box-Behnken design. The results demonstrated that under optimized experimental conditions, the calibration curves for the target analytes displayed good linearity (r ≥ 0.996 9) in the concentration range of 5.00–100.00 μg/kg. The limits of detection for the analytes were 0.62–0.76 μg/kg and the limits of quantification were 2.06–2.53 μg/kg. The spiked recoveries were in the range of 82.92%–106.98%. The developed method has the advantages of simple operation, short extraction time, low consumption of organic reagents and environmental friendliness and can be used for the analysis and detection of triazine herbicides in cereals.