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    • Flavor is the core code for the dialogue between food and consumers, and also an important research direction that integrates scientificity and humanism in the field of food science. This virtual special issue focuses on the multi-dimensional research of food flavor, bringing together the latest achievements of top teams at home and abroad. It covers key areas such as the identification and characterization of flavor substances, the formation and change mechanisms of flavor during processing, sensory evaluation and consumer preference analysis, and the development of novel flavor regulation technologies.

    1  Liquid-Liquid Extraction Technology for Aroma and Flavor Compounds in Traditional Fermented Beverages and Seasonings
    FAN Wenlai
    2023, 41(3):19-27. DOI: 10.12301/spxb202300257
    [Abstract](1788) [HTML](1468) [PDF 6.11 M](1234)
    Abstract:
    The aroma and flavor of traditional fermented beverages and seasonings is an important aspect of determining their quality. The use of modern flavor chemistry theory and methods to study their aroma and flavor has been recognized by the industry. One of the most important operations in the series of studies on aroma and flavor compounds is the isolation or extraction of flavor compounds, which involves the isolation of flavor interfering substances or matrices. If the target flavor compounds could not be extracted at the sampling, the correct results could not be obtained. Most isolation and extraction techniques can be used for this process, but some researchers have found that liquid-liquid extraction technology could be the best method for extracting and isolating the aroma and flavor of traditional fermented beverages and seasonings. Before liquid-liquid extraction, the pre-treatment methods of solid, liquid, semi-liquid, and bioactive raw materials are different. The principle for selecting the extraction solvent is that the characteristic aroma and flavor compounds, all flavor compounds, and target flavor compounds of the original sample must be extracted. The selection of liquid-liquid extraction methods should consider the volatility, boiling point, polarity, stability, concentration, distribution in the sample, and other characteristics of the flavor compounds to be tested. The ideal liquid-liquid extraction result is the simultaneous extraction of polar and non-polar compounds, without causing thermal degradation and redox of flavor compounds, without changing pH value, and without significant loss of high volatile compounds. Due to the presence of compounds, such as proteins, sugars, and fats in the matrix, emulsification often occurs during liquid-liquid extraction. Demulsification could be achieved through methods such as salt addition, ultrasound, freeze-centrifugation, solvent assisted flavor evaporation (SAFE), glass wool filtration, phase filtration, addition of solvents with different polarity, and addition of precipitant. Due to the complex composition of aroma and flavor compounds in the extraction solution, direct GC-MS or GC-O analysis could result in overlapping peaks of compound coeluting and interference of aromas. The extraction solution could be fractioned into acidic, alkaline, and neutral fractions, and further analysis could be carried out by combining chromatographic separation techniques such as silica gel column or normal phase column. The systematic reviews of the liquid-liquid extraction technology of traditional fermented beverages and seasonings flavors could inspire the research ideas of flavor researchers.
    2  Study on Supervision and Safety Assessment System of Food Flavorings in EU and USA
    FENG Tao ,  LIU Qian ,  YE Ran ,  CHEN Yi
    2022, 40(5):28-35. DOI: 10.12301/spxb202200844
    [Abstract](1882) [HTML](2200) [PDF 5.91 M](1431)
    Abstract:
    Flavorings play a pivotal role in food industry as an important kind of food additives. However, improper use of food flavorings can cause food safety risks. There are thousands of flavorings allowed using in food in the world at present. Therefore, it is necessary to formulate regulations and standards for supervision and safety assessment. Relatively perfect supervision and safety assessment systems for food flavorings has formed in EU and USA over the years, which played a vital role in international supervision and safety evaluation of flavorings. The regulatory agencies on food flavorings in EU and USA were reviewed. Regulations of food flavorings in USA were mainly conducted by the Food and Drug Administration (FDA). The safety assessment of flavorings was handed over to the Food Flavor and Extract Manufacturers Association (FEMA), which was mainly responsible for security of the food flavorings through the FEMA GRAS program. The supervision of food flavorings in EU was mainly performed by the Council of Europe (COE) and the European Food Safety Authority (EFSA). Wherein, EFSA was the authoritative organization that formulated food safety regulations and mainly published the list of EU-licensed food flavorings. In addition, safety assessment methods including exposure estimation and toxicological assessment were reviewed. The PCI×10 method was most acceptable for exposure estimation in USA, while the MSDI method was considered to be the most suitable method for intake estimation of general flavorings by EFSA. In terms of toxicological assessment, the threshold of toxicological concern (TTC) method was currently utilized for genotoxic risk assessment both in EU and USA. The safety evaluation systems of flavorings in EU and USA were highly similar, which could also provide guidance and reference for the improvement of the supervision and safety assessment system for food flavorings in China.
    3  Status, Challenges and Countermeasures of Supervision on Food Flavorings in China
    MU Min ,  LIU Hua ,  LIANG Yanhui ,  LI Meng
    2022, 40(5):36-42. DOI: 10.12301/spxb202100708
    [Abstract](1784) [HTML](2570) [PDF 5.63 M](1327)
    Abstract:
    In recent years, fragrance and flavor industry in China kept overall growth, but the development speed was slowed down. Compared with developed countries and regions, the gap had a tendency to widen. In 2020, the main business income of fragrance and flavor industry in China exceeded 40 billion yuan, of which the production and sales of food flavorings amounted to more than one-third of the total fragrance and flavor industry. At the end of 2020, there were nearly 1000 food flavorings manufacturers in China. This study had the outstanding characteristics of large number and wide distribution, uneven distribution and relative concentration, and relatively small scale and uneven development level. In order to ensure the safety of food flavorings in China, food and food additive related laws and regulations and the standard system of food safety national standards constituted the supervision system on food flavorings. This study was aimed at the difficulty of obtaining the production license for the sub-packaging of food flavorings, the production licenses issued to each product, prohibition of re-inspection of synthetic food flavor substances, the less food flavor substances permitted to use, slower approval of new varieties, and preposition of national food safety standards. This study proposed to implement scientific and effective supervision based on the characteristics of industries and products, further simplify the approval procedures for new varieties and establish safety assessments system, allow the adoption and implementation of other standards beside the national food safety standards, strengthen the popularization of science and establish a positive image of the industry and other suggestions and countermeasures. This paper was expected to provide a useful reference for the faster development of China's food flavoring industry and to meet the needs of domestic and foreign markets.
    4  Flavor Difference Analysis of Thermal Processing Meat Flavoring Prepared with Different Varieties of Mushroom Materials
    LIU Zixuan ,  GAO Ya ,  WANG Wenqian ,  ZHANG Huiying ,  CHEN Haitao ,  HUANG Dian ,  ZENG Yan
    2022, 40(1):30-43. DOI: 10.12301/spxb202100940
    [Abstract](2786) [HTML](1853) [PDF 11.85 M](1824)
    Abstract:
    To investigate the effects of different varieties of mushroom on the flavor of mushroom-derived meaty Maillard reaction products (MRPs), four MRPs were prepared using Lentinus edodes, Pleurotus eryngii, Pleurotus ostreatus and Agaricus bisporus as raw materials. The free amino acids in four kinds of mushroom hydrolysates were analyzed by high performance liquid chromatography. Descriptive sensory analysis, gas chromatography-ion mobility spectroscopy (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) were exployed to analyze the volatile components in four MRPs. The results showed that the amino acid content of different mushroom hydrolystes had significant variations. Sensory analysis data indicated that significant differences existed between MRPs, among which MRP prepared with Lentinus edodes hydrolysate showed strong meaty aroma. From the four MRP samples, GC-IMS detected 59 kinds of volatile components and GC-MS detected 68 kinds of volatile components. Volatile analysis indicated that significant differences were existed between MRPs. Principal component analysis could preliminary distinguish different MRP samples. In the orthogonal partial least squares discriminant analysis, samples were well separated according to their volatile characteristics. In addition, 10 kinds of volatile components mainly including aldehydes, alcohols, acids and sulfur-containing compounds were each screened by GC-IMS and GC-MS based on variable importance in projection score over 1, which were closely related to the composition of precursors in different mushroom varieties. This study aims to provide a basis for product improvement of mushroom-derived meaty flavorings.
    5  Aroma Change and Its Relationship with Key Enzymatic Reactions in Drying Process of Stropharia rugosoannulata
    LI Jialin ,  YANG Yan ,  LI Wen ,  CHEN Wanchao ,  LIU Xiaofeng
    2023, 41(1):30-42. DOI: 10.12301/spxb202200616
    [Abstract](1976) [HTML](1424) [PDF 13.64 M](1226)
    Abstract:
    Headspace solid phase microextraction-gas chromatography-mass spectrometry technology was used to separate and identify the volatile flavor compounds in the fruiting bodies of Stropharia rugosoannulata at different drying periods, and the changes of volatile flavor compounds in the drying process under the condition of hot air drying at 55℃ constant temperature was explored. A total of 245 volatile flavor compounds were identified in the whole drying process, including 34 aldehydes, 29 esters, 40 alcohols, 37 ketones, 7 acids, 24 alkanes, 26 olefins and 48 other compounds. Aldehydes, ketones and alcohols accounted for a relatively large proportion, and the sum of the three contents accounted for 65.49%-89.30% of the total content, which were the main volatile substances in Stropharia rugosoannulata. A total of 45 key odor compounds were screened out through the thermal analysis of odor activity value combined with partial least squares discriminant analysis. Among them, 1-octene-3-ketone was always the compound with the largest contribution to the odor during the drying process, and there were 20 different compounds before and after the drying process. The comprehensive analysis showed that the aroma change law of Stropharia rugosoannulata during the drying process was as follows:with the drying process, the odors of soil and grass gradually weakened, and the flavors of coke and malt presented in the late drying process, but the mushroom flavor and soil odor were still the key flavor characteristics of Stropharia rugosoannulata during the whole process.Determination of key enzyme activities in the main metabolic pathways of aldehydes, ketones and alcohols, indicated that the enzyme would be activated by heat, and the enzyme activity showed a significant downward trend as a whole during the drying process. There was almost no activity at the end of the drying process. The correlation analysis between the metabolic enzyme activity and the corresponding compound content showed that lipoxygenase had a strong positive correlation with aldehydes and ketones, alcohol dehydrogenase had a strong negative correlation with alcohols. It was consistent with the dynamic change trend of aldehydes, ketones and alcohols during the drying process.
    6  Comparison of Nutritional Components and Flavor Characteristics of Fresh and Hot-Air Dried Tremella fuciformis
    SUN Hailan ,  XI Jiapei ,  ZHANG Junmiao ,  CHEN Xiao ,  HU Qiuhui ,  ZHAO Liyan
    2023, 41(1):43-55. DOI: 10.12301/spxb202200519
    [Abstract](2121) [HTML](2080) [PDF 11.80 M](1074)
    Abstract:
    In order to study the changes of nutrition and flavor characteristics of fresh Tremella fuciformis before and after hot air drying, the basic nutrients, bioactive components, amino acids and mineral elements in fresh and dried T. fuciformis were comparatively measured. The flavor characteristics of fresh and dried T. fuciformis samples were analyzed by gas chromatography-ion mobility spectroscopy (GC-IMS) and gas chromatography-mass spectrometer (GC-MS). The results showed that the contents of crude protein, crude fat, total amino acids, crude polysaccharides, total polyphenols and total triterpenes in fresh T. fuciformis were significantly reduced after hot air drying (P<0.05). The amino acid content and composition of T. fuciformis changed after air drying, and the amino acid nutritional value of fresh T. fuciformis was closer to the WHO/FAO recommended model of protein. In addition, the contents of some mineral elements such as calcium, iron, copper and zinc in T. fuciformis were reduced after drying. A total of 30 volatile flavor compounds both in fresh and dried T. fuciformis were identified by GC-IMS, and 41 volatile flavor compounds were identified by GC-MS. The composition and content of volatile compounds in fresh and dried T. fuciformis were significantly different. Compared with dried T. fuciformis, fresh T. fuciformis was not only rich in 1-octen-3-ol with typical mushroom flavor, but also rich in α-pinene, ethyl propionate methyl butyrate and other esters with fruity flavor. It could be concluded that T. fuciformis was rich in nutrition and unique in flavor. The research results could provide a certain preliminary theoretical basis for the sales and deep processing of fresh T. fuciformis.
    7  Effect of Steam Infusion and Steam Injection Ultra-High Temperature Treatment on Active Proteins and Flavor Compounds in Milk
    MENG Fanyu ,  HAN Zhaosheng ,  ZHANG Zheting ,  DING Hao ,  LU Xiaoli ,  LU Chun ,  MA Ligang ,  KANG Zhiyuan ,  WANG Bei ,  ，LI Yan
    2023, 41(2):70-80. DOI: 10.12301/spxb202300050
    [Abstract](2549) [HTML](1621) [PDF 8.53 M](1194)
    Abstract:
    Ultra-high temperature treatment (UHT) is a common sterilization method for milk that can be classified as direct and indirect UHT. Direct UHT was not widely applied in the dairy industry due to the high cost. Recently, with higher requirements of nutrients and flavor of milk from consumers, direct UHT was re-concerned due to its high heating rate, short heating time, and low loss of flavor and nutrients. This study compared the effects of two direct UHT methods, steam infusion and steam injection on physio-chemical properties, native whey proteins content, and volatile compounds content of milk. The results showed that UHT milk treated by steam infusion had lower mean particle size, instability index, and viscosity, whereas higher levels of desaturated whey proteins, compared to that in UHT milk treated by steam injection. 59 volatile compounds in total were detected in UHT milk through two extraction methods as solid-phase microextraction arrow and solvent-assisted flavor evaporation combined with gas chromatography-mass spectrometry, of which 50 volatile compounds were detected in steam-injection-treated UHT milk and 52 volatile compounds were detected in steam-infusion-treated UHT milk. Steam-infusion-treated UHT milk had a lower proportion of ketones, aldehydes, and fatty acids, while a higher proportion of esters and alcohols compared to that in UHT milk treated with steam injection. Principal component analysis results showed that steam-injection-treated UHT milk and steam-infusion-treated UHT milk could be distinguished by volatile compounds, indicating that different direct UHT methods could influence the flavor of UHT milk. It was recommended that dairy companies select steam injection if they intend to produce UHT milk with a heavier milky flavor, while select steam infusion if they plan to produce UHT milk with less cooking flavor, less off-flavor, and higher physical stability during storage. The result of this study aimed to provide supporting data and theory reference for the dairy industry to choose proper sterilization methods and produce UHT milk with a longer shelf-life, higher levels of nutrients, and better flavor.
    8  Analysis of Ripening Characteristics and Flavor of Blue Style-Yak Milk Cheese
    YANG Wanling ,  SHEN Xingwang ,  CUI Fengyi ,  WANG Guangqiang ,  SONG Xin ,  YANG Yijin ,  XIONG Zhiqiang ,  ZHANG Hui ,  AI Lianzhong ,  XIA Yongjun
    2023, 41(6):52-64. DOI: 10.12301/spxb202300008
    [Abstract](1815) [HTML](1342) [PDF 12.08 M](1089)
    Abstract:
    Yak milk has nutritional properties of high protein and high fat content, and has good functional activities, such as anti-fatigue. However, due to the low production of yak milk and the scattered production area, there was limited research on the development of cheese products and other deep processing aspects. Penicillium roqueforti (P.roqueforti) was used as a secondary starter to develop blue style-yak milk cheese, and its ripening characteristics and flavor characteristics were analyzed. Results showed that P. roqueforti could grow rapidly in yak milk cheese, promoted the degradation of proteins, and formed a large number of peptides, amino acids, etc. The content of free amino acids, especially unami amino acids, was significantly increased at the end of yak milk cheese maturity (P＜0.05). SPME-GC/MS analysis showed that a total of 53 flavor components were detected in yak milk cheese. OPLS-DA analysis revealed that compared with the early stage of ripening, the composition of flavor components in yak milk cheese at the end of ripening was significantly different, and the total content was significantly increased (P＜0.05). The volatile aliphatic esters in yak milk cheese were mainly methyl esters, and the content was relatively stable in end stage (25d, 46d) of ripening. The content of volatile fatty acid was highest in the middle stage of ripening, but significantly decreased at the end of ripening (P＜0.05). The concentration of volatile aliphatic ketones, especially methyl ketones, increased significantly in the end ripening stages (P＜0.05). 2-Nonanone, 2-heptane, methyl octanoate, 2-pentanone, ethyl caprate, methyl caprate, caproic acid, 2-octanone, butyric acid and other volatile compounds were quantitatively dominant flavor components of blue style-yak milk cheese. The study showed that P. roqueforti could promote the ripening of yak milk cheese, which could significantly affect the nutrition and flavor characteristics of yak milk cheese. The research aimed to lay a theoretical foundation for the deep processing of characteristic dairy products such as yak milk in China, and provide reference for promoting the development of China's characteristic dairy deep processing industry.
    9  Analysis and Safety Assessment of Concerned Flavor Ingredients in Commercial Modified Milk
    SHI Lili ,  LI Ting ,  LI Haoze ,  CAO Xueli
    2022, 40(6):153-162. DOI: 10.12301/spxb202100756
    [Abstract](2302) [HTML](1510) [PDF 7.24 M](984)
    Abstract:
    Flavor can provide, supplement and stabilize the flavor in modified milk. Due to the characteristic of “self-limiting” and low dosage, less attention has been paid to its potential safety risk. The contents of 19 concerned flavor ingredients in 100 commercial modified milk samples from 25 brands were analyzed through SPME-GC-MS/MS in MRM mode which was evaluated methodologically. Benzaldehyde (100%), 2,3-butanedione (96%), linalool (88%) and hexyl alcohol (86%) were detected at higher rate. Vanillin (18886.03μg/kg), ethyl maltol (6271.15μg/kg), maltol (2522.64μg/kg) and benzyl alcohol (1937.60μg/kg) were detected at high average levels with the detection rates at 47%, 71%, 40% and 30%, respectively. The contents of flavor ingredients in different samples were greatly varied, even if in the samples with same taste from different brands. The exposure level and safety risk of the 19 concerned flavor ingredients were assessed accordingly based on the survey results of the daily intake of modified milk in different populations. Both the exposure analysis of the whole population and different populations showed that the per capita daily intake (PCI) of ethyl maltol and vanillin exceeded the threshold of toxicological concern (TTC) in some cases, which varied among different populations, but the overall risk was low. There was no safety risk for the rest of concerned flavor ingredients under the current intake of modified milk.
    10  Flavor Characterizations of Maillard Reaction Products of Enzymatical Hydrolysates of Soybean and Chicken with Different Molecular Weights
    TANG Long ,  SONG Huanlu ,  WANG Lijin
    2023, 41(3):148-162. DOI: 10.12301/spxb202200174
    [Abstract](2102) [HTML](1466) [PDF 11.84 M](1311)
    Abstract:
    In order to study the flavor characteristics of peptides with different molecular weights via Maillard reaction, the protein hydrolysates were obtained by enzymatic hydrolysis using soy protein and chicken as raw materials. Then the enzymatic hydrolysates were separated by ultrafiltration to obtain peptides with different molecular weights, less than 1000Da, 1000~5000Da and greater than 5000Da. In addition, the complex amino acids were obtained by complete acid hydrolysis of enzymatical hydrolysates of soybean and chicken. A certain amount of xylose was added in peptides and amino acids to build a Maillard reaction model. The sensory properties of Maillard reaction products were evaluated. Then the volatile and nonvolatile compounds were analyzed by gas chromatography-mass spectrometry and high-performance liquid chromatography. The results showed that in the Maillard product of enzymatical hydrolysates of two different protein sources, a total of 69 kinds of volatile compounds were identified, among which the contents of pyrazine, furanthiol and other meat flavor compounds were the highest. Statistical analysis showed that there were significant differences in volatile compounds of peptides with different molecular weights and free amino acids. The formation of pyrazine compounds was promoted by peptides less than 1000Da during the Maillard reaction, such as pyrazine, 5-methyl-2-ethylpyrazine, 2,5-methyl-3-ethylpyrazine, trimethylpyrazine, 2-acetylpyrrole, etc. Compared with peptides, free amino acids favored the formation of sulfur-containing compounds such as furanthiols and thiophenes. Only 29 volatile compounds had relative odorant activity values (rOAV) greater than 1. Partial least squares regression (PLSR) was used to investigate correlations between key odor compounds and sensory evaluations. Peptides less than 1000Da were found to be closely related to the basic meaty and kokumi, while peptides greater than 5000Da were closely related to bitter and burnt flavor. After Maillard reaction, the amount of peptides greater than 5000Da was significantly reduced. Degradation of peptides of 1000-5000Da could replenish the consumed free amino acids. The peptides less than 1000Da were prone to cross-link and polymerization and thus increased the content. The products had a significantly enhanced effect on the flavor, and could contribute well to the basic meaty, umami and kokumi. It was hoped that this study could provide theoretical support and guidance for the application of proteolysates to produce Maillard reaction products.
    11  Effect of Thermal Pretreatment on Taste Components of Chicken Breast Meat and Chicken Bone Paste
    HAO Zhilin ,  LIANG Li ,  LIU He ,  ZHANG Yuyu
    2022, 40(4):107-115. DOI: 10.12301/spxb202100314
    [Abstract](1744) [HTML](1717) [PDF 6.27 M](1529)
    Abstract:
    In order to explore the effects of thermal pretreatment temperature before enzymolysis on the taste components of chicken breast meat and chicken bone paste, sensory evaluation of chicken breast meat and chicken bone paste samples after different temperature treatments was carried out. The contents of free amino acids and nucleotides were determined and the equivalent umami concentration (EUC) value of each sample was calculated. Chicken breast meat and chicken bone paste samples with thermal pretreatment at 60℃ for 30min, followed by enzymolysis and milling exhibited the better sensory evaluation results and taste characteristics. Compared with the control groups without thermal pretreatment, thermal pretreatment can improve the overall taste of chicken breast meat and chicken bone paste samples. With the increase of thermal pretreatment temperature, the contents of free amino acids in the chicken breast meat and chicken bone paste samples decreased, among which the total amount of bitter amino acids declined the most (leucine content decreased the most), followed by sweet amino acids and umami amino acids. With thermal pretreatment at 60℃ and then enzymolysis, the content of 5′-CMP, 5′-GMP and 5′-IMP in chicken breast meat sample were higher than that in the control group without thermal pretreatment, and the chicken bone paste sample had a higher contents of 5′-IMP and 5′-AMP. In addition, the umami amino acid content and the EUC value of chicken bone paste sample (0.96g MSG/100g) were higher than that of chicken breast meat sample (0.52g MSG/100g). In conclusion, this study laid a data foundation for the effect of thermal pretreatment before enzymolysis on the taste components of chicken breast meat and chicken bone paste, which might be helpful to provide a theoretical basis for the optimization of enzymatic hydrolysis process in the industrial production of chicken flavored condiments.
    12  Effects of Ozone-Ice Slurry Treatment on Flavor of Pseudosciaena crocea Based on SPME-GC-MS and Electronic Nose Analysis
    LIU Jianhua ,  ZHU Rongrong ,  ZENG Qianhua ,  TANG Wei ,  DING Yuting
    2023, 41(1):154-162. DOI: 10.12301/spxb202200614
    [Abstract](2080) [HTML](1374) [PDF 8.27 M](1066)
    Abstract:
    To investigate the effects of different ozone concentrations (0,1,3,5mg/L) in ozone-ice slurry (O-IS) treatment on the flavor of Pseudosciaena crocea during the storage life of excellent grade, the change pattern of volatile flavor substances was analyzed and discussed using solid-phase microextraction-gas chromatography mass spectrometry (SPME-GC-MS) combined with electronic nose technique, and the fresh fish cubes and fish cubes preserved with traditional flake ice method were used as controls. The results showed that a total of 35 volatile components, mainly aldehydes, hydrocarbons and alcohols, were detected in the Pseudosciaena crocea samples by SPME-GC-MS. Among them, the quantitative analysis of hexanal, heptanal, 1-octen-3-ol and etc., which were the volatile substances that made the fish fishy, proved that 1mg/L O-IS treatment could degrade the content of fishy smell substances in Pseudosciaena crocea while reducing the oxidation effect of ozone on the fish flesh. Electronic nose analysis found that the response to fishy odor substances in the O-IS treatment groups were significantly lower than that in the control group. Moreover, after 1mg/L O-IS treatment, the fishy substances were not detected by the electronic nose. This study showed that within the shelf life of excellent grade of Pseudosciaena crocea, the 1.00mg/L O-IS treatment could significantly reduce the fishy substance content of Pseudosciaena crocea.
    13  Odor Compounds Analysis of Fresh and Heated Watermelon Juice Based on Mono Trap-GC-O-MS
    YANG Fan ,  XU Ying ,  DAI Yixin ,  BI Shuang ,  LIU Ye
    2023, 41(1):143-153. DOI: 10.12301/spxb202100820
    [Abstract](1292) [HTML](1212) [PDF 8.91 M](1034)
    Abstract:
    Mono Trap has the characteristics of large extraction amount and simple operation. It has the advantages in the extraction of odor compounds in watermelon juice. Mono Trap and thermal desorption combined with gas chromatography-olfactory-mass spectrometry were used to extract and analyze the odor compounds of watermelon juice before and after thermal treatment. The three adsorbent materials, RGC18, RSC18 and RGPS, were used and identified 50 and 71 odor compounds from fresh and heated watermelon juice, respectively. The comparison results of the extraction effects of these three adsorbent materials showed that RGC18 had the best extraction effect on the odor compounds of watermelon juice. 41 and 53 odor compounds were extracted by RGC18 from fresh and heated watermelon juice, respectively. After the thermal treatment, the odor compounds of watermelon juice have changed greatly. The odor activity value of compounds exhibited bitter almond, soapy, and sharp acidic flavors, such as 2-methylbutanal, furfural, octanal, decanal, (E)-2-heptenal, acetic acid and formic acid increased, while hexanal, β-cyclic citral and (E,E)-2,4-nonadienal with green and lemon odor cannot be smelled. The changes of these compounds were the important reasons for the off-flavor of watermelon juice after thermal treatment.
    14  Analysis of Key Flavor Compounds in Peeled Walnut Kernel Based on GC-O-MS and Sensory Evaluation
    JIA Yimin ,  YUAN Binhong ,  YU Pei ,  WAN Chuyun ,  XU Wei ,  ZHOU Qi
    2023, 41(4):126-134. DOI: 10.12301/spxb202200618
    [Abstract](2067) [HTML](1599) [PDF 6.82 M](1181)
    Abstract:
    Peeled walnut kernels are popular among consumers for their easy consumption, wide application scenarios and excellent flavor, of which flavor is an important index for evaluating walnut quality. To study the key flavor substances of peeled walnut kernels, three varieties of walnut raw materials (Qing Xiang, Wen 185 and Da Pao) were selected for peeling and low temperature roasting, and sensory evaluation analysis was carried out by nine-point scale method, and volatile flavor compound of peeled walnut kernels were analyzed by gas chromatography-olfactometry-mass spectrometry. The results indicated that the peeled walnut kernels showed an overall sensory taste of fatty, sweet and creamy flavor with low bitterness. A total of 25 volatile flavor compounds, including 6 aldehydes, 2 ketones, 9 alcohols, 2 esters, 4 hydrocarbons, 1 furan and 1 ether, were detected in three varieties of peeled walnut kernels by headspace solid phase microextraction. The nine key flavor components, including hexanal, octanal, nonanal, furfural, benzaldehyde, 1-hexanol, 1-pentanol, 2,3-butanediol and 2-heptanol, were further clarified using solvent-assisted flavor evaporation combined with olfactometry to give the walnuts a raw green, fatty, burnt and sweet flavor. Correlation analysis was performed between the nine key flavor components and sensory attributes, and it was found that nonanal, hexanal, 2-heptanol, 2,3-butanediol and 1-pentanol were the key substances causing sensory differences in walnuts of different varieties. The results of this paper provided important support for the improvement of the flavor quality of walnut kernels and the creation of peeled walnut kernel snacks.
    15  Detection of Volatile Flavor Compounds and Harmful Factors in Four Kinds of Convenience Food
    ZHANG Chenping ,  WANG Yutong ,  XIE Jianchun ,  CHENG Jie ,  XIAO Qunfei ,  WANG Yaxin
    2022, 40(2):172-182. DOI: 10.12301/spxb202100214
    [Abstract](1894) [HTML](1705) [PDF 7.33 M](2173)
    Abstract:
    In order to explore the correlation between flavor compounds and harmful factors, the contents of volatile flavor compounds and harmful factors including acrylamide, polycyclic aromatic hydrocarbons, and trans fatty acids were determined in 16 samples from four kinds of convenience food, namely fried potato chips, fried instant noodles, fried dough twists and salted roast peanuts kernel. 78 volatile flavor compounds were identified by solid-phase microextraction/gas chromatography-mass spectrometry through search of the NIST 2015 library and comparison with the documented retention indices, including nitrogen-containing heterocycles, oxygen-containing heterocycles, aldehydes, carboxylic acids, ketones, esters, and alkanes, etc. The results showed that trans-fatty acids were not detected in all samples. In fried potato chips and fried instant noodles, acrylamide and seven polycyclic aromatic hydrocarbons (PAHs), i.e. acenaphthene, anthracene, chrysene, fluoranthene, fluorene, phenanthrene and pyrene were found. In comparison, there were more pyrazines and acrylamide in fried potato chips, more carboxylic acids and PAHs in fried instant noodles, more fatty aldehydes and oxygen-containing heterocycles in fried dough twists and salted roast peanuts kernel. Partial least squares regression analysis showed that the content of acrylamide was positively and significantly (P<0.05) correlated with the volatile flavor compounds of pyrazine, 2-methylpyrazine, etc, which could be generated via the Maillard reaction. The above seven PAHs were significantly(P＜0.05) and positively correlated with aldehydes and acids, that could be formed via lipid degradation during the frying or roasting of the food. The results revealed that it was important to take into account the formation of good flavor and also harmful factors when selecting appropriate food processing technologies.
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