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Chemometric Identification of Volatile Components in Essential Oils Extracted from Sweet Orange Peels by Different Methods

LIU Feifei, CHEN Jin, CHEN Jianle, LIU Donghong, YE Xingqian, CHENG Huan

FOOD SCIENCE 2024, 45 (7): 155-163. DOI: 10.7506/spkx1002-6630-20230808-047

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Quantitative descriptive sensory analysis (QDSA), gas chromatography-ion mobility spectrometry (GC-IMS) and Heracles NEO electronic nose (E-nose) combined with chemometrics were used for differential analysis of volatile compounds in essential oils (EOs) extracted from sweet orange peels (blood and navel) using cold pressing (CP), microwave-assisted hydrodistillation (MAHD) or spinning cone column (SCC). The results indicated that significant variations in flavor composition were found among the three EOs. The CP oil had the highest sensory preference with stronger fruity, sweet, and floral aromas. The MAHD oil had stronger fatty, green, and woody aromas, and the SCC oil had a lower aroma intensity. A total of 64 volatile components were identified by GC-IMS, terpenes, alcohols and aldehydes being the major ones, followed by acids, esters and other compounds. The fingerprint indicated that the contents of terpenes in the CP and MAHD oils were significantly higher than that in the SCC oil, whereas the contents of alcohols and aldehydes in the MAHD and SCC oils were significantly higher than those in the CP oil. Based on relative odor activity value (ROAV), β-myrcene and linalool were identified as the major contributors to the flavor of sweet orange EO. Moreover, using GC-IMS combined with partial least square discriminant analysis (PLS-DA) and variable importance in the projection (VIP), 13 differential volatile compounds were identified as aroma markers to distinguish among the 6 oils. Additionally, E-nose combined with principal component analysis (PCA) and discriminant factor analysis (DFA) also successfully distinguished among the 6 EOs according to their volatile compounds.

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Hyperspectral Imaging for the Detection of Vitamin C Content in Potatoes Based on Fisher Discriminant Analysis Separable Information Fusion

GUO Linge, YIN Yong, YU Huichun, YUAN Yunxia

FOOD SCIENCE 2024, 45 (7): 164-171. DOI: 10.7506/spkx1002-6630-20230808-034

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In order to improve the accuracy and reliability of the prediction results of the vitamin C (VC) content in potatoes by hyperspectral imaging, a method for constructing input variables for predictive models based on Fisher discriminant analysis (FDA) separable data fusion was proposed. First, hyperspectral information of 200 potato samples was collected by hyperspectral imaging technology, and by comparing the modeling results obtained with the spectral data before and after preprocessing by 6 spectral preprocessing methods, multiplicative scatter correction (MSC) was determined as the optimal preprocessing method. Second, competitive adaptive reweighted sampling (CARS), successive projections algorithm (SPA) and CARS-SPA algorithm were used to extract the feature wavelengths, and 34 effective feature wavelengths were finally determined through comparative analysis. Third, the effective feature wavelengths were fused by FDA to achieve data separability, and the fused new variables were screened for their capacity to discriminate the differences among samples in order to determine the input variables for predictive models. Finally, predictive models using partial least squares (PLS) and back propagation neural network (BPNN) were established based on the variables selected before and after FDA fusion, and the results from these models were compared and analyzed. It was shown that the correlation coefficient of the BPNN model increased from 0.972 6 to 0.999 0, and the root mean square error (RMSE) reduced from 0.772 3 to 0.172 7 when the 34 effective feature wavelengths extracted by CARS were used for FDA fusion and the first three fused variables were used as the input variables, which not only greatly reduced data dimensionality, but also improved the accuracy of the detection results. Therefore, constructing input variables for the detection model based on FDA separable data fusion could improve the accuracy of the detection of potato VC content.

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Analysis of Differences in Flavor Characteristics among Different Grades of Stir-Fried Pixian Broad Bean Paste by SPME-GC-MS and GC-IMS

ZHANG Hao, GU Siyuan, DENG Jing, ZHOU Jianqin, TANG Yingming, YI Yuwen

FOOD SCIENCE 2024, 45 (7): 172-181. DOI: 10.7506/spkx1002-6630-20230811-077

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In order to identify the differences in flavor among different grades of stir-fried Pixian broad bean paste, solid-phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS), GC-ion mobility spectrometry (GC-IMS), principal component analysis (PCA), orthogonal partial least squares discriminant analysis (OPLS-DA) and odor activity value (OAV) were applied to determine the key flavor compounds. The results showed that SPME-GC-MS identified 88 volatile organic compounds (VOCs), including 15 aldehydes, 11 alcohols, 17 esters, 13 ketones, 5 acids, 5 olefins, 6 alkanes, 7 heterocycles, 2 phenols, 7 ethers and other compounds. Among them, 34 were common to all samples. A total of 57 compounds were identified by GC-IMS, and 16 key flavor compounds with variable importance in the projection (VIP) values > 1 were identified by OPLS-DA. According to their OAV values, ethyl butyrate contributed to the apple-like aroma of super grade Pixian broad bean paste, and isovaleraldehyde contributed to its malty aroma; ethyl isovalerate contributed to the fruity aroma of first grade Pixian broad bean paste, and 3-methylthiopropionaldehyde was responsible for its roasted potato-like and soy sauce-like aroma; ethyl isbutyric acid contributed to the fruity aroma of second grade Pixian broad bean paste, and isovaleraldehyde and isobutyraldehyde were responsible for its malty aroma. Finally, it was determined that the overall aroma characteristics of stir-fried Pixian broad bean paste were fruity, wine-like, malty, sour, herbaceous, cocoa-like, almond-like and soy sauce-like. These results can serve as references for determining the aroma characteristics of stir-fried Pixian bean paste in the future, and provide a basis for the early design of sensory descriptors for quantitative descriptive analysis.

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Effect of Exogenous Application of Methyl Jasmonate on Volatile Flavor Components and Contents of Tomato Fruits

MA Haiyun, ZHANG Zhonglin, HUO Jing

FOOD SCIENCE 2024, 45 (7): 182-190. DOI: 10.7506/spkx1002-6630-20230801-005

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Volatiles are an important aspect of the flavor quality of tomato fruits. However, whether volatiles in tomato fruits respond to the regulation of exogenous methyl jasmonate (MeJA) remains unclear. In this study, four concentrations of MeJA (1, 10, 100 and 200 μmol/L) were sprayed on ‘Chaoyan 298’ tomatoes before harvest, and an equal volume of ultrapure water was used as the control. Ripe fruits were harvested and analyzed for the composition and content of volatile compounds by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Meanwhile, the optimal concentration of MeJA for improving the flavor quality of tomatoes was determined by multivariate statistical analysis. The results showed that a total of 71 volatile components were detected in the 5 groups, including 23 aldehydes, 17 alcohols, 8 ketones, 7 esters, 6 hydrocarbons and 10 other substances. Compared with the control group, exogenous application of MeJA increased the number and total amount of volatile compounds in tomato fruits, which increased first and then decreased with the increase in MeJA concentration, reaching the maximum value at 100 μmol/L MeJA concentration. Altogether 33 components were common to all groups, with the most abundant one being (Z)-3-hexen-1-ol. A total of 13 characteristic aroma components were identified in all tomato fruits, which mainly contributed to green, fruity and flowery notes. Overall, our results provide theoretical support that exogenous MeJA can improve that flavor quality of tomato fruits, which are conducive to further exploring the regulation mechanism of volatile compound biosynthesis in tomato fruits.

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Sensory Evaluation and Metabolomic Analysis of Lycium Leave Tea

LU Li, ZHOU Chengzhe, XU Kai, ZHANG Mengcong, WEN Shengjing, DUAN Linyuan, TIAN Caiyun, SHI Biying, ZHANG Bo, GUO Yuqiong

FOOD SCIENCE 2024, 45 (7): 191-201. DOI: 10.7506/spkx1002-6630-20230808-052

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The sensory quality and metabolite profiles of the fresh and dried buds and leaves of Lycium from 26 cultivars (lines) were analyzed by sensory evaluation and metabolomics combined with multivariate statistical analysis. The results of sensory evaluation showed that the dried buds and leaves of Lycium had a mellow, fresh and sweet taste, and by liquid chromatography-mass spectrometry (LC-MS), 879 metabolites were identified in Lycium buds and leaves, including amino acids and their derivatives, flavonoids, phenolic acids, saccharides, nucleotides and their derivatives, lignans and coumarins, alkaloids, terpenoids, organic acids, and lipids. Using partial least square discriminant analysis (PLS-DA) model and one-way analysis of variance (ANOVA), 211 differential metabolites were selected, which were mainly enriched in the linoleic acid metabolism, flavonoid biosynthesis, flavonoids and flavanols biosynthesis, phenylpropanol biosynthesis, and galactose metabolism pathways. In addition, it was found that amino acids and their derivatives, flavonoids, sugars, and lipids were important components to discriminate the metabolites of different cultivars (lines). Partial least squares regression (PLSR) analysis showed that 26 metabolites including epicatechin, isoquercitrin, and rutin collectively affected the taste of Lycium tea such as mellow, thick, fresh, sweet and bitter. The results of sensory evaluation and PLSR analysis showed that seven cultivars (lines) of Lycium including ‘Ningqicai No. 1’, ‘Ningqi No. 9’, Z90, Z68, Q3, Q6-13, and Z48 had better sensory quality and rich flavor substances.

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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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