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Multivariate Analysis and Discrimination of Quality Factors of Xiangcha Tea

MA Junhui, TONG Chen, FENG Haiqiang, LI Qian, WANG Yu, LUO Liewan, WANG Xiaochang, LIN Jie

FOOD SCIENCE 2024, 45 (6): 130-135. DOI: 10.7506/spkx1002-6630-20230108-054

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In this study, 50 samples of Zhejiang Xiangcha tea, a representative of bulk green tea, from four varieties grown in three regions in Zhejiang province were collected and investigated. Correlation analysis among physicochemical indexes, catechin components, sensory factors and local wholesale prices was performed. The characteristic quality factors were selected and geographical origin and varietal discrimination were conducted by linear discriminant analysis (LDA) and random forest regression (RF-R). Moreover, this study attempted to establish a reference wholesale price prediction model. The results showed that the contents of free amino acids and caffeine were significantly correlated with several sensory factors, which were the key physicochemical factors for the formation of the flavor quality of Xiangcha tea. The contents of free amino acids and catechins and the ratio of phenol to ammonia were the origin-related factors. There were highly significant varietal differences in the overall sensory score, appearance, and sensory score for taste of Xiangcha tea, and significant differences in the aroma and the sensory score of brewed tea leaves. LDA demonstrated clear clustering of tea samples from each county and the feasibility of discriminating tea samples from different counties but not from different varieties. The reference wholesale price prediction mode developed by RF-R had good fitness (R2 = 0.867, mean absolute error = 7.907). The relative importance of factors for price fitting was ranked as follows: appearance > overall sensory score > aroma > infusion color > sensory score of brewed tea leaves > taste > amino acids > water extract > phenol to ammonia ratio > caffeine > tea polyphenols. The results of this study will guide the quality factor analysis, geographical origin traceability, varietal discrimination and trade reference pricing of tea.

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Physicochemical Properties and Flavor Components of Four Foxtail Millet Bran Fractions

WANG Yunting, ZHANG Aixia, ZHAO Wei, LIU Jingke

FOOD SCIENCE 2024, 45 (6): 136-143. DOI: 10.7506/spkx1002-6630-20230705-037

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Millet bran with different degrees of milling was used as raw materials, the differences in nutritional composition, physicochemical properties, and volatile components of different foxtail millet bran fractions were explored by measuring nutritional composition, water distribution, hydration characteristics, chromaticity, gelatinization characteristics, and volatile components. The results showed there were significant differences in content of fat, protein, ash, starch, and water among the four types of foxtail millet bran (S1–S4). S3 millet bran contained 10.96% protein and 26.05% fat, with the highest nutritional value. Meanwhile, S3 millet bran had excellent characteristics such as strong fluidity, strong foaming ability (5.54%), and high stability (82.86%), but high content of water and oil were not conducive to the storage of S3 millet bran. Correlation analysis shows that starch and protein directly affected the processing properties of millet bran (hydration characteristics, foaming properties, etc.). In addition, 72, 47, 70, and 51 volatile substances were detected in the four types of millet bran (S1–S4), respectively. There were 10 different volatile substances in 4 types of millet bran. Six compounds including methyl hexanoate, hexanal, and methyl palmitic acid had the highest content in S1 millet bran, and the other 4 compounds including dodecane and n-hexanol had the highest content in S2 millet bran. The odor activity value (OAV) of nonanal in four types of millet bran was 702, 444, 110, and 51, respectively, which could be used to effectively distinguish these foxtail millet bran fractions. This study is conducive to the precision separation process and selective use, which can maximize the utilization of resources.

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Effect of Membrane Separation on Chemical Composition and Antioxidant Activity of Water Extracts from Different Kinds of Tea from Fujian

LIN Qingxia, WANG Lili, SONG Zhenshuo, CAI Shuxian, LIU Zhonghua, CHEN Lin

FOOD SCIENCE 2024, 45 (6): 144-152. DOI: 10.7506/spkx1002-6630-20230412-107

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This study was done in order to investigate the changes of the major biochemical components and in vitro antioxidant activity of the water extracts from different kinds of tea during the process of their multistage membrane separation, ultrafiltration membranes with molecular masses cut-off (MMCO) of 20, 10, and 3.5 kDa, respectively were successively used to separate the water extracts from the major kinds of tea in Fujian including green tea, white tea, oolong tea from south Fujian, oolong tea from north Fujian, and black tea into fractions with different molecular masses. The fractions were spray dried and investigated for their ultraviolet (UV) spectra, biochemical compositions and in vitro antioxidant activity. The results showed that the UV absorption spectra of all samples were similar, exhibiting two obvious peaks at 210 and 274 nm. Absorbance at 274 nm exhibited a significant positive correlation with the contents of free amino acids (FAAs), caffeine (CAF), gallic acid (GA) and epicatechin gallate (ECG), and a significantly negative correlation with the contents of epigallocatechin (EGC) and epicatechin (EC). The distribution of biochemical components and the changes in antioxidant activity in vitro were affected by membrane separation, among which, the 20 kDa MMCO membrane had the most pronounced impact. The retentate from black tea after 20 kDa MMCO membrane ultrafiltration had the highest antioxidant activity in vitro, while the antioxidant activity of the permeate was lower than that of the permeate from the other kinds of tea. The biochemical components and antioxidant activity in vitro varied significantly among different types of tea samples, and the changes in biochemical components and antioxidant activity during the membrane separation process were not completely consistent. The water extract from black tea showed the greatest changes after 20 kDa MMCO membrane ultrafiltration. These results could provide a scientific basis for the membrane separation of aqueous extracts from different types of tea.

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Glycerin Extraction Combined with High Performance Liquid Chromatography-Tandem Mass Spectrometry for Determining the Contents of Seven Types of Chemical Components in Tea and Its By-Products

GUAN Mengdi, ZHENG Yaru, YANG Zhulin, LI Huimin, LOU Huaqiao, YANG Yubing, LI Jiamei, YI Lunzhao, LI Siyu, HU Yongdan, REN Dabing

FOOD SCIENCE 2024, 45 (6): 153-163. DOI: 10.7506/spkx1002-6630-20230616-135

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In this study, glycerin was used instead of traditional solvents such as methanol in combination with ultrasonic treatment for the high-efficiency extraction of multiple chemical components from tea. Furthermore, a quantitative analytical method for 130 chemical components belonging to seven classes in tea and its by-products was developed using ultra-high performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-QQQ-MS/MS). The results showed that the extraction efficiency of glycerol was comparable to that of methanol and ethanol, and significantly better than that of water. The developed method had high sensitivity (limit of detection of 0.000 1-4.332 1 mg/kg) and accuracy (recoveries of 80.10%–121.12%). Appling this method to real samples, the content of each component varied greatly among different types of tea and by-products. Compared with tea samples, tea residue, a tea by-product, contained higher contents of caffeine, catechin and theanine, indicating the potential value of this by-product.

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Simultaneous Direct Determination of Various Trace Aroma and Flavor Substances and Derivatives in Baijiu by UPLC-HRMS

YANG Junlin, YIN Yanyan, YIN Yanshun, YANG Shaojuan, TIAN Dongwei, XIE Dan, YOU Xiaolong, WU Cheng, HU Jianfeng, ZHANG Deqin

FOOD SCIENCE 2024, 45 (6): 164-174. DOI: 10.7506/spkx1002-6630-20230512-105

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A rapid and accurate qualitative and quantitative method based on ultra-high performance liquid chromatography-high-resolution mass spectrometry (UPLC-HRMS) was established for the determination of various trace aroma and flavor substances and their derivatives in baijiu. Samples were centrifuged at high speed, filtered and separated on a Hypersil Gold C18 (150 mm × 2.1 mm, 1.9 μm) column before analysis. The results showed that the pretreatment process allowed multi-component analysis of baijiu without extraction using ethanol or other organic solvents within 16 minutes. The calibration curves established using a mixed standard solution of 17 amino acids, 4 bioamines and 11 non-volatile organic acids exhibited good linearity (R2 > 0.990), and the detection limits and quantitation limits were relatively low for all analytes, which meet the requirements of the compositional analysis of baijiu. The average recoveries for all analytes were 71.92%–117.45%, with relative standard deviations (RSDs) of 0.46%–5.48%. The developed method had good recovery, precision, and stability for all analytes. Therefore, this method has the advantages of simple operation, high sensitivity, and good repeatability, and is of reference significance for the analysis of the types and contents of other non-volatile flavor substances in baijiu.

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Proteomic Analysis of the Effect of Proteasome on Quality Changes in Qinchuan Beef during Postmortem Storage

HU Lijun, WANG Jinxia, LI Rong, ZHANG Qian, CHEN Xueyan, LI Yalei, LUO Ruiming

FOOD SCIENCE 2024, 45 (5): 86-93. DOI: 10.7506/spkx1002-6630-20230412-118

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In this study, the Longissimus dorsi muscle of Qinchuan beef stored at 4 ℃ after slaughter was determined for its quality indicators, energy level and proteasome activity. Meanwhile, differentially expressed proteins (DEPs) associated with proteasomes were identified. Bioinformatics methods were used to analyze the response mechanism of proteasomes to the quality and energy metabolism of postmortem beef. The results showed that pH decreased and then increased with increasing storage time, b* and myofibrillar fragmentation index (MFI) increased, L*, a*, centrifugal loss, cooking loss and shear force increased first and then decreased, the contents of the basic energy substances ATP, ADP and AMP decreased, and the relative activity of the 20S proteasome decreased significantly (P < 0.05). The correlation analysis showed that the activity of the 20S proteasome was significantly negatively correlated with b* (P < 0.05), positively correlated with ADP content (P < 0.05), positively correlated with AMP content (P < 0.01), and negatively correlated with MFI (P < 0.01), indicating a close relationship between proteasome activity and energy metabolism as well as beef quality. Using 4D label-free quantitative (LFQ) proteomics, eight differentially expressed proteasome subunits and 27 DEPs were identified. Gene Ontology (GO) annotation analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that these proteasome subunits and related DEPs had molecular functions such as endopeptidase activity, actin binding, microfilament motor activity, and were involved in biological processes such as ubiquitin-dependent proteolytic metabolism, skeletal muscle contraction, muscle contraction, and glycolysis, thus causing changes in the quality of Qinchuan beef. During the early postmortem period, the proteasomes regulated the biological pathways by consuming energy substances to catabolize proteins, and during the later period, when the energy substances were depleted, the proteasomes catabolized proteins in postmortem beef through the energy provided by glycolysis and non-ATP-dependent proteasome subunits, which eventually affected the quality of Qinchuan beef.

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Application of Conductivity Combined with Various Other Instrumental Analyses in the Detection of the Freshness and Yolk-to-White Ratio of Liquid Egg

DOU Wenhao, WANG Hailing, HUANG Zilong, YANG Fuming, CHI Yuan, CHI Yujie

FOOD SCIENCE 2024, 45 (5): 94-101. DOI: 10.7506/spkx1002-6630-20230831-238

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This study established a rapid and efficient technique to detect the freshness and yolk-to-white ratio of liquid egg based on conductivity combined with salinity, total dissolved solids (TDS), pH, and color parameters. The results showed that during the storage period of 0-45 days at 4 ℃, the conductivity, salinity, and TDS of egg yolk and egg white gradually increased. The color difference index and egg yolk pH of both decreased significantly, while the pH of egg white gradually increased. It was found that the accuracy of conductivity in detecting the freshness of egg yolk and egg white was 91% and 89%, respectively, while that of conductivity combined with other indices was 94%. Based on this, the criteria to classify liquid egg into four grades of AA, A, B and C were established for the first time. AA liquid eggs were selected to detect yolk-to-white ratio using conductivity as the major index combined with salinity, TDS and pH. The experimental results proved that the conductivity, salinity, TDS and pH were all highly significantly and linearly correlated with the proportion of egg yolk in liquid egg; therefore, the proportion of egg yolk in unknown liquid egg samples could be detected based on the regression equations. The ExpAssoc model showed an average relative error of 8.87%, indicating high reliability. The results of this study provide a theoretical basis for the detection of the freshness and yolk-to-white ratio of blended liquid egg, and provide a reference for industrial producers of liquid egg.

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Metabolic Profiling of Non-volatile Compounds during Xinyang Maojian Tea Processing Using Untargeted Metabolomics

KONG Yashuai, CHEN Lingzhi, CHENG En, ZHU Yao, WANG Jingjing, WANG Xiao, WANG Zihao, CHEN Yi, YIN Peng, GUO Guiyi

FOOD SCIENCE 2024, 45 (5): 102-110. DOI: 10.7506/spkx1002-6630-20230824-188

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In order to understand the dynamic changes of non-volatile metabolites in Xinyang Maojian tea during processing, Xinyang Maojian tea samples from Xinyang tea population (Camellia sinensis cv. Quntizhong) taken during processing were systematically analyzed by non-targeted metabolomics. A total of 1 000 non-volatile metabolites were identified, and multivariate statistical analysis showed that non-volatile metabolites changed significantly during the processing stages after fixation. Meanwhile, a total of 53 differential compounds were screened out, including amino acids, catechins, flavonoid glycosides, lipids, purine nucleosides and organic acids that were identified as the key components contributing to the flavor and quality of Xinyang Maojian tea. In particular, the relative contents of some acylated flavonoid glycosides, lysophosphatidyls and purine nucleosides were significantly elevated during the processing stages after fixation. Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathway enrichment analysis showed that the differential compounds were significantly enriched in the pathways of purine metabolism, glycerophospholipid metabolism, phenylalanine metabolism, aminoacyl-tRNA biosynthesis, phenylalanine, tyrosine, and tryptophan biosynthesis, and glycine, serine and threonine metabolism (P < 0.05). This study provides a basis for understanding the formation mechanism of the flavor and quality of Xinyang Maojian tea.

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Analysis of Key Aroma Components of Four Kinds of Single Malt Whisky

ZHANG Yi, LI Xiaoyan, NIU Limin, LI Hui, SHEN Bo, CHEN Wenbo, SHANGGUAN Jingyu

FOOD SCIENCE 2024, 45 (5): 111-117. DOI: 10.7506/spkx1002-6630-20230829-220

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Aroma compounds in Scottish Macallan single malt and Japanese Yamazaki single malt whisky of two ages each were analyzed by headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME/GC-MS). The results showed that esters, acids, and alcohols were the most abundant volatile compounds in all whisky samples, accounting for over 90% of the total. Odor activity value (OAV) was calculated for 58 of the 243 volatile compounds identified. Phenylethyl acetate, acacia alcohol, and trans-nerolid alcohol in Scotch Macallan whisky had higher OAVs, contributing to obvious floral aroma, while Japanese Yamazaki whisky had an obvious fruity aroma, due to higher OAVs of ethyl isovalerate, ethyl 2-methylbutyrate, and 1-decanol. Two-dimensional hierarchical clustering analysis suggested that the typical aroma compounds in Yamazaki whisky were 2-methylbutyrate ethyl ester, butyrate ethyl ester, and isovalerate ethyl ester, while those in Macallan whisky were acacia alcohol, trans-nerolid alcohol, and damastone. Additionally, principal component analysis (PCA) confirmed that each whisky had unique aroma characteristics. This study suggests that flavor characteristics are an important index for the evaluation of different whisky samples.

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Quality Analysis of ‘Akizuki’ Pear Fruit (Pyrus pyrifolia) from Different Geographical Origins by Gas Chromatography-Ion Mobility Spectrometry

HE Wanlin, SHI Lu, LIN Menghua, LI Yahui, LIANG Ying, ZHANG Zhiyong

FOOD SCIENCE 2024, 45 (5): 118-125. DOI: 10.7506/spkx1002-6630-20230828-196

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In order to explore the quality characteristics of ‘Akizuki’ pear fruit (Pyrus pyrifolia) from different regions, the quality indexes of pear fruit from six geographical origins were determined, and gas chromatography-ion mobility spectrometry (GC-IMS) was used to determine their volatile aromatic compounds. The results showed that the titratable acid content of pear fruit from Ningling, Henan province was significantly higher than that of pear fruit from the other regions. There were significant differences in the contents of soluble solids, total flavonoids, and total phenols among some regions (P < 0.05). Totally 76 volatile aroma components were identified in the pericarp and pulp of pear fruit from the six different regions, including 23 esters, 20 aldehydes, 11 alcohols, 4 ketones, 1 olefin, 3 acids, and 14 other compounds. There were 24 more volatile aroma components in the pericarp than in the pulp. The unique volatile aroma components including isobutyl acetate, methyl butyrate, and isovaleraldehyde were detected in pear fruit from Weixian, Hebei province when compared with the other regions. Similarity analysis from fingerprints showed clear distinction among pear fruit from different regions. This study has provided information about the quality and aroma characteristics of ‘Akizuki’ pear fruit from different regions, and demonstrated that GC-IMS has potential application prospects for geographical origin differentiation and traceability of ‘Akizuki’ pear fruit.

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Analysis of Key Aroma Compounds in Fermented Goji Berry Wine

LIU Yaran, LI Junlong, GU Peishan, LI Ruotong, ZHU Baoqing, ZHANG Bolin

FOOD SCIENCE 2024, 45 (5): 126-136. DOI: 10.7506/spkx1002-6630-20230602-016

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The volatile aroma compounds of wine fermented from goji berries were evaluated by liquid-liquid extraction-solvent-assisted evaporation-gas chromatography-mass spectrometry-olfactometry (LLE-SAFE-GC-MS-O) combined with GC-quadrupole-MS (GC-qMS) and GC-Orbitrap-MS. The key aroma compounds were identified by aroma reconstitution and quantitative descriptive sensory analysis. The results showed that ethyl esters (ethyl cinnamate, ethyl acetate, ethyl 2-methylpropanoate, ethyl 2-methylbutanoate, ethyl 3-methylbutanoate, ethyl hexanoate, ethyl lactate, ethyl octanoate, and ethyl decanoate), other esters (isoamyl acetate and isoamyl lactate), C13-norisoprenoids (β-damascenone and β-ionone), volatile phenols (4-ethylguaiacol, eugenol, 2,4-di-t-butylphenol), alcohols (1-octen-3-ol, benzyl alcohol, phenylethyl alcohol and isopentyl alcohol) and other compounds (naphthalene, methionol, octanoic acid and 2-acetylpyrrole) contributed the major aroma attributes of goji berry wine. This finding will help to enrich and improve the theoretical basis of the aroma of goji berry wine and lay the foundation for aroma enhancement and quality improvement of goji berry wine.

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Dynamic Headspace Combined with Gas Chromatography-Olfactometry-Mass Spectrometry for Analysis of Volatile Components in Baked Green Tea from Different Cultivars

LI Weixuan, XIE Dongchao, SHAO Chenyang, ZHANG Yue, LÜ Haipeng, LIN Zhi, DU Qizhen, ZHU Yin

FOOD SCIENCE 2024, 45 (5): 137-148. DOI: 10.7506/spkx1002-6630-20230624-177

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In this study, a dynamic headspace (DHS) combined with thermal desorption/gas chromatography-mass spectrometry (TD/GC-MS) method was established to analyze the volatile composition of baked green tea. Extraction parameters including tea amount, trapping temperature, incubation temperature, total purge volume, purge rate, and drying rate were optimized. Furthermore, the key odorants of baked green tea made from different tea cultivars were identified by gas chromatography-olfactometry-mass spectrometry (GC-O-MS). The results indicated that the optimal extraction conditions were as follows: tea amount of 200 mg, trapping temperature of 70 ℃, incubation temperature of 70 ℃, total purge volume of 350 mL, purge rate of 10 mL/min, and drying rate of 10 mL/min. A total of 74 volatile components were identified in green tea made from three representative varieties. Multivariate statistical analysis showed that the aroma compounds of the three green teas varied greatly, and 18 key differential volatile aroma components were identified. The contents of isopropylidesneacetone and linalool in LongJing 43 (LJ 43) baked green tea were the highest among these three teas. Fuding Dabaicha (FDDB) baked green tea contained the highest levels of 6-methyl-5-heptene-2-one, octanal, cyclohexanone, acetophenone, copaene and epicubenol. A total of 28 odorants were identified by GC-O-MS analysis. The odorants were mainly responsible for odor attributes such as green, refreshing, floral, fruity, herbal, woody and sweet aromas. The total aroma intensity of floral and fruity attributes was the highest, followed by the green and refreshing attributes. Taken collectively, linalool, calamenene, δ-cadinene, 6-methyl-5-heptene-2-one and octanal were the key differential odorants among the three green teas. Linalool contributed significantly to LJ 43 baked green tea, and the other four odorants contributed significantly to the formation of the aroma quality of FDDB baked green tea.

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Effect of Composting Treatment of Grape Branches on Wine Quality

TU Qian, DING Weikang, HUANG Yanping, LI Yuanyuan, LIU Shiqiu, MIN Xuwu, ZHENG Changhua, YUAN Chunlong

FOOD SCIENCE 2024, 45 (5): 149-157. DOI: 10.7506/spkx1002-6630-20230829-216

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In order to study the effect of applying different proportions of compost made from grape branches in the vineyard on the quality of wine, 8-year-old ‘Pinot Noir’ grapevine was selected for this study, and compost made from 100% crushed grape branches (GB), compost made from 70% crushed grape branches + 30% sheep manure (GM1), compost made from 50% crushed grape branches + 50% sheep manure (GM2), compost made from 30% crushed grape branches + 70% sheep manure (GM3), and 100% sheep manure (SM) were applied to the vineyard , and the no compost addition treatment (CK) was used as a control. One year after fertilization, grape berries were taken to brew wine, and the basic physicochemical indexes of grapes and wine, the phenolic substances, color, and aroma substances and sensory evaluation of wine were determined. The results showed that the composting treatment significantly increased the contents of alcohol, total phenols, total anthocyanins, total flavan-3-ols, and total flavonoids in Pinot Noir wine, with the GM3 treatment showing the greatest increase in the levels of alcohol and titratable acids, by 16.5% and 24.03%, respectively. In terms of color, the composting treatments increased the color saturation of ‘Pinot Noir’ wine. Orthogonal partial least squares-discriminant analysis (OPLS-DA) of aroma substances showed that the major differential aroma substances in ‘Pinot Noir’ wine among different composting treatments were isoamyl alcohol, followed by ethyl acetate, 1-propanol, and phenylethanol, and that composting treatments with the addition of grape branches increased the levels of ethyl acetate, isoamyl acetate, ethyl caproate, and ethyl caproate in ‘Pinot Noir’ wine. In terms of sensory quality, the intensity of astringency, bitterness, and sweetness of ‘Pinot Noir’ wine was enhanced by the composting treatments, and the wine was improved in terms of taste and balance. This study provides a theoretical basis for the comprehensive utilization of grape branch waste and the improvement of wine quality.

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Effect of Osmotic Concentration through Polydimethylsiloxane Membrane on Aroma of Freeze-Dried Rose Hydrolat

LIU Xiaoyu, LI Xuesong, SHAN Yanqin, ZHANG Boya, LI Jingming

FOOD SCIENCE 2024, 45 (5): 158-165. DOI: 10.7506/spkx1002-6630-20230512-114

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In order to explore the effect of polydimethylsiloxane (PDMS) membrane pervaporation technology on the concentration of freeze-dried rose hydrolat (Rosa damascene), headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS) were used to analyze the volatile aroma components of freeze-dried rose hydrolat, and its sensory properties and applicability were evaluated by sensory analysis. The results showed that 54 aroma components were detected in rose hydrolat, and its characteristic aroma components including phenylethyl alcohol, citronellol and geraniol accounted for more than 90% of the total, indicating great utilization value. After two osmotic concentration cycles, the rose aroma became more intense and typical, and the content of benzene ring compounds significantly increased, characterized by total odor activity value (OAV) of rose aroma substances increased by 20.47%. The sensory flavor profile analysis also showed similar results: the proportion of floral aroma intensity (M value) increased from 37% to 51%, which was consistent with the result of partial least squares regression (PLSR) validation analysis. Additionally, it was found that the aroma intensity of freeze-dried rose hydrolat obtained after secondary osmosis was similar to that of rose essence sold in the market, and still higher than that of rose soda water sold in the market after 100-fold dilution, demonstrating its potential as a flavor enhancer in daily chemicals and beverages.

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Comparative Analysis of Sensory Evaluation Methods for Qingzhuan Tea

LIU Panpan, FENG Lin, ZHENG Lin, XUE Jinjin, WANG Shengpeng, WANG Xueping, YE Fei, TENG Jing, GUI Anhui, HAN Yanna, CHEN Junhai, ZHU Peng, GAO Shiwei, ZHENG Pengcheng

FOOD SCIENCE 2024, 45 (4): 144-153. DOI: 10.7506/spkx1002-6630-20221121-237

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To propose a sensory evaluation method suitable for Qingzhuan tea, a representative Qingzhuan tea produced in Hubei was soak or spray boiled in order to analyze the effects of different boiling conditions on the sensory quality and the leaching rate of major chemical components of Qingzhuan tea. The sensory quality and chemical components of the tea infusions were compared with those of tea infusion obtained by the brewing method specified in the Chinese national standard. The results showed that the sensory quality of the boiled tea infusion was significantly better than that of the brewed tea infusion; the leaching rates of major quality components such as water extract, tea polyphenols, amino acids, soluble sugars and tea pigments were much higher in the former than in the latter. From the perspectives of sensory quality and the leaching rate of major quality components, tea infusion prepared by boiling for 2 min with a tea/water ratio of 1:80 and then standing for 2–4 min tasted moderate and had good internal quality. Further correlation analysis showed high correlation coefficients between the leaching rates of soluble sugars, theabrownine and water extract and taste quality. The results of this study provide a reference for the objective evaluation of the sensory quality of Qingzhuan tea and other types of compressed tea.

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Analysis of Differential Muscle Metabolites in Bactrian Camels Slaughtered at Different Ages by Non-Targeted Metabolomics Based on Ultra-high Performance Liquid Chromatography-Mass Spectrometry

SI Rendalai, TUYATSETSEG Jambal, BANZRAGCH Maizul, MING Liang, HE Jing, JI Rimutu

FOOD SCIENCE 2024, 45 (4): 154-163. DOI: 10.7506/spkx1002-6630-20230507-054

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In this study, non-targeted metabolomics based on ultra-high performance liquid chromatography Q-Exactive-mass spectrometry (UPLC-Q-Exactive-MS) was used to explore the differences in the metabolite profiles of muscles from Bactrian camels slaughtered at different ages. The results showed that a total of 710 differentially expressed metabolites (DEMs) were identified in the longissimus dorsi muscle of camels from three age groups: I (3–4 years old), II (6–7 years old), and III (9–10 years old). In total, 78 DEMs were found in groups I vs II, of which 47 were upregulated in group I and 31 were upregulated in group II. Totally, 49 DEMs were identified in groups II vs III, of which 18 were upregulated in group II and 31 were upregulated in group III. In addition, 65 DEMs were identified in groups I vs III, of which 29 were upregulated in group I and 36 were upregulated in group III. The results of Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that the DEMs were mainly enriched in pathways such as protein and amino acid metabolism, fatty acid metabolism, and vitamin and mineral metabolism, indicating that the digestion and metabolism of various nutrients in camels were different at different growth stages. The contents of polyunsaturated fatty acids (PUFA) (especially n-6 PUFA and n-3 PUFA) and the PUFA/unsaturated fatty acid (UFA) ratio were significantly higher in group I than III, which was mainly related to the significant upregulation of arachidonic acid, linoleic acid and 13-L-hydroperooleic acid concentrations in relevant metabolic pathways. Meanwhile, DEMs such as L-leucine, L-valine, and L-glutamine could serve as potential markers for evaluating the quality change of camel meat at different slaughter ages.

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Analysis of Flavor and Nutritional Quality of Fresh Sea Buckthorn Juice and Pulp

REN Jingnan, JIA Xiao, ZHANG Zhifeng, WU Kangning, FAN Gang, LI Mingzhe, MA Youli, MA Xueli, SHAO Yalong, LIU Chunhai, WAN Xu, CHEN Yang, ZHAO Shiliang

FOOD SCIENCE 2024, 45 (4): 164-170. DOI: 10.7506/spkx1002-6630-20230426-256

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Identification of odor compounds in fresh sea buckthorn juice (FSBJ) and pulp (SBP) was performed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). A total of 39 and 36 odor compounds were identified in FSBJ and SBP, respectively. Further findings revealed that ethyl hexanoate, ethyl 2-methylbutyrate, ethyl 3-methylbutyrate, and 3-methylbutyl 3-methylbutanoate had high flavor dilution (FD) factors and were identified as the key odor compounds in FSBJ. In addition, the contents of ester compounds contributing to the fruity odor were significantly reduced in SBP after pasteurization. Sensory evaluation and electronic tongue analysis revealed that the sweetness and overall taste of SBP were superior to those of FSBJ. The contents of vitamin C and total flavonoids were significantly lower in SBP than in FSBJ, indicating that pasteurization reduces the nutritional quality of FSBJ. The results of the study can provide theoretical references for the flavor and nutritional quality optimization of sea buckthorn products.

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Metabolomic Analysis of the Chemical Composition of ‘Tieguanyin’ and ‘Shuixian’ Tea

ZHOU Chuang, ZHAO Yanni, ZHOU Mengxue, PENG Jiakun, CHEN Dan, WANG Zhe, LIN Zhi, CHEN Xuefeng, DAI Weidong

FOOD SCIENCE 2024, 45 (4): 171-182. DOI: 10.7506/spkx1002-6630-20230511-099

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In order to investigate the effect of cultivar and processing technique on the chemical composition of tea, this study analyzed green tea, fresh-scent oolong tea, strong-scent oolong tea and black tea made from the fresh leaves of the ‘Tieguanyin’ and ‘Shuixian’ cultivars from the same graphical origin using metabolomics based on ultra-high performance liquid chromatography-time-of-flight mass spectrometry (UPLC-TOF-MS). The results showed that the chemical compositions of tea samples made from different tea cultivars differed considerably. The contents of most lipids, alkaloids and methylated catechins were higher and the contents of theanine, most catechins, flavone (flavonol) glycosides, phenolic acids and N-ethyl-2-pyrrolidinone-substituted flavan-3-ols were lower in ‘Tieguanyin’ tea than in ‘Shuixian’ tea. Processing techniques also significantly impacted the chemical composition of tea. A total of 127 differential compounds were selected, among which the contents of most catechins, dimeric catechins, alkaloids and some amino acid compounds were significantly higher in green tea than in other kinds of tea. The contents of some amino acids and flavone (flavonol) glycosides (quercetin-3-galactoside, and kaempferol-3-glucosylrutanoside) were higher in fresh-scent oolong tea. The contents of N-ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSF), some flavone (flavonol) glycosides (quercetin-3-glucoside, and kaempferol-3-6”-acetylgalactoside), and lipid compounds in strong-scent oolong tea were higher, while black tea was richer in theaflavins and several flavone (flavonol) glycosides.

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Effects of Different Production Processes on the Quality and Flavor of Soybean Oil as Evaluated by Electronic Nose, HS-SPME-GC-MS and HS-GC-IMS

WU Siyu, XIE Xuan, LIU Yuwen, SUN Shukun, CHEN Hao

FOOD SCIENCE 2024, 45 (4): 183-196. DOI: 10.7506/spkx1002-6630-20230510-090

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In order to explore the effects of different production processes (cold pressing, leaching, and their combination) on the quality and flavor of soybean oil of third grade, the physicochemical properties and fatty acid composition of the three soybean oils were determined, and their volatile compounds were identified and analyzed by electronic nose, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), and headspace-gas chromatography-ion mobility spectroscopy (HS-GC-IMS). Differential analysis of the volatile compound data among the soybean oils was performed by clustering heatmap analysis, principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). The results showed that cold-pressed soybean oil had the lowest moisture content; the peroxide value of leached soybean oil was significantly higher and its color was the darkest. Fragrant soybean oil had the highest linoleic acid content and a higher nutritional value; and among the detected volatile components, alcohols, aldehydes and pyrazine compounds mainly contributed to the formation of soybean oil flavor, and the reasons for the formation of some flavor compounds were clarified. Finally, 45 volatile compounds with high contributions were selected by OPLS-DA, and a reliable model was constructed for identifying fragrant soybean oil. In addition, a correlation was found between the quality and flavor of soybean oil.

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Characteristics of Oligosaccharide Composition in Chinese Human Milk

MI Lijuan, YAN Jingyu, GUO Shanshan, JIA Ni, PANG Jinzhu

FOOD SCIENCE 2024, 45 (4): 197-206. DOI: 10.7506/spkx1002-6630-20230428-279

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To analyze the impact of different regions, lactation times, and blood group genotypes on the oligosaccharide composition of healthy lactating mothers’ breast milk from representative regions of China, and to explore the compositional characteristics of oligosaccharides in Chinese human milk, in this longitudinal cohort study, the concentrations of 23 oligosaccharides in breast milk samples from 109 healthy mothers at three lactation stages in six cities in east, west, north and south China were analyzed by ultra-high performance liquid chromatography triple quadrupole tandem mass spectrometry (UPLC-MS-MS). Besides, the attribution of breast milk to blood group genotypes was investigated. The results showed that concentrations of total oligosaccharides and total fucosylated neutral oligosaccharides were significantly higher in samples from Kunming, Jinan and Shenzhen than those from Beijing, Baotou and Xining, and the concentrations of 3-fucosyllactose (3-FL), lactodifucotetraose (LDFT) and lacto-N-neodifucohexaose II (LNnDFH-II) were significantly lower in samples from Baotou than those from Shenzhen, Jinan and Beijing, respectively. The concentrations of eight neutral oligosaccharides and four acidic oligosaccharides showed a significant decreasing trend with lactation time, whereas 3-FL concentration increased significantly, and the concentrations of LDFT and LNnDFH-II also increased but not significantly. The concentrations of two monofucosylhexasaccharides were the highest in 1-month-old mature milk, and then remained unchanged or decreased slightly as lactation progressed. Based on oligosaccharide types, it was inferred that the major blood group genotype of lactating mothers was Se+Le+ for all the six cities. In this genotype, the concentrations of lacto-N-difucohexaose-II (LNDFH-II), LNDFH-I & LNnDFH-I, 6’-sialyllactose (6’-SL) and sialyllacto-tetrasaccharide c (LSTc) were higher and the concentrations of 18 other oligosaccharides were lower than in other genotypes. This study provides scientific theoretical guidance for precise estimation of the intake of breast milk oligosaccharides by infants and young children at the early life stage.

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