Abstract:The concept of ‘future foods’ has a far-reaching connotation and broad extension. It covers all aspects of the theories and technologies involved in food production, harvesting, storage, processing, packaging, distribution and consumption. At the same time, ‘future foods’ is inseparable with agriculture system, ecological resources, earth environment, animal welfare, and human spiritual civilization. This study summarized the currently challenges facing humanity needed to be continuously dealing with in the future, including inadequate food supply, serious food loss and waste, and nutrition and health crisis. A prospective analysis was carried out on the hot research areas in future foods. Novel food production systems including plant factory, cell factory, chemical synthesis based on soilless cultivation, single cell culture, biochemical catalysis will be powerful complements to traditional food production systems. Accompanied with the mining and utilization of new food resources, a sustainable food supply will be achieved. Minimization of food loss will be accomplished by perfecting the food logistics and supply chain systems, establishing the rational processing of targeted raw materials, developing the green food processing technology and intelligent packaging. Engineering technologies including extrusion-shearing, 3D printing and nano-assembling, and intelligent catering technologies, combined with big data and perception interacting personalized design, will enable future foods to meet the consumer precise demand. Through the introduction of new theories, new resources, and new technologies, this study hopes to provide some fundamental scientific references for the healthy and sustainable development of the future food industry.

Abstract:Milk not only provides nutrients for the growth and development of infants and the daily needs of people, but also contains abundant of biological active components. The casein glycomacropeptide, α-lactalbumin, lactoferrin, osteopontin and fat globule membrane in milk not only provide nutrition, they also have biological functional properties such as antioxidation, intestinal health improvement, bone homeostasis improment, immune regulation, mineral absorption promotion, and antibacterial function. Results of animal experiment and clinical trials demonstrated that lactoferrin, osteopontin, α-lactalbumin, and fat globule membrane protein exerted beneficial effects on nutrient absorption, immunity, intestinal health and neurodevelopment in infants. Besides, casein glycomacropeptide, α-lactalbumin and their enzymatic hydrolysates had anti-inflammatory and insulin resistance improvement properties. Milk-derived bioactive components and their derivatives have been extensively researched, explored and applied in the formula food with the development of food science and separation techniques. Addition of milk-derived bioactive components as ingredients to infant formula narrowed the gap between infant formula and breast milk to some extent. Addition of bioactive components to functional foods also contributed to improve life quality and promote healthy ageing of special population such as middle-aged and elderly people and patients with chronic diseases. In this article, the structure and biological functions of five common milk-derived bioactive components were systematically reviewed, which might provide reference for the development of functional milk ingredients and application in formula food.

Abstract:Breast milk (human milk) is natural food to feed human newborns. It is not only the source of energy and nutrients for infant, but also a kind of comprehensive extension protection provided by the mother for babies. As a result of natural evolution, breast milk has diverse and complex components, including nutrients that support infant metabolism, and bioactive substances that help infant development. The content, composition of subcomponents, and chemical and biological status of these components in breast milk can perfectly match the infant's characteristics of anatomy, physiology, biochemistry, and meet the requirements of energy and nutrition, immune function, microecological development, and other needs, which is a biological necessary system for survival and healthy growth of infants. The composition of breast milk is also a foundation of the health superiority of breastfeeding. Due to the natural compatibility between the breast milk composition and the needs of the infant, breastfeeding shows a protective effect on the healthy growth and development of the infant in early life and reduces the risk of chronic diseases in adulthood. Breastfeeding can ensure to improve a healthier physical growth of the breast-fed infants, promote brain growth and cognitive development, balance the development of immune system, improve resistance, reduce the risk of infectious diseases, and provide a significant protective effect on allergic diseases. In terms of long-term health benefits, breastfeeding reduces the risk of obesity in childhood and adulthood, and significantly reduces the risk of metabolic syndrome (hypertension, dyslipidemia and insulin resistance) in adulthood. Further research on the composition of breast milk is not only helpful to understand the nutritional needs of infants, but also is an indispensable scientific support for the development of infant formula food.

Abstract:To investigate the effects of vegetable oils with different fatty acid compositions on the flavor and sensory properties of the plant-based meat, five types of plant-based meat supplemented with rapeseed oil, soybean oil, peanut oil, sunflower oil or palm oil which were commonly used in meat processing and contained different fatty acid compositions, were analyzed by headspace-solid-phase-microextraction combined with gas chromatography-olfactometry-mass spectrometry. Meanwhile, their sensory characteristics were measured by sensory evaluation and texture analysis. The results showed that there were significant differences of volatile components, sensory attributes, and texture properties among the five groups of plant-based meat. A total of 79 volatile components were identified in these groups, and 30 odor active compounds were identified by smelling, mainly including pyrazines, furans, aldehydes, sulfur-containing compounds. 2,3,5-trimethylpyrazine, 2-pentylfuran, 3-methylthiopropanal, etc had maximal odor intensity. The types and contents of volatile compounds in sample C added with peanut oil and sample A added rapeseed oil were higher than those in the other groups. The flavor of sample C was predominantly oily and its hardness was lowest than that in the other groups, which made its unsuitable for the production of plant-based meat. The sample A mainly had the meat flavor, and its hardness and elasticity were greater. The results showed that rapeseed oil containing more erucic acid and oleic acid was more suitable for the production of plant-based meat, which was more helpful than the other oils in enhancing its flavor and sensory characteristics.

Abstract:The study on the rheological behavior of soybean protein isolate under different conditions is helpful to understand the formation process of fibrous structure of textured plant protein produced by extrusion. Taking soybean protein isolate as experimental material, the changes of apparent consistency of soybean protein isolate under the two modes of continuous stirring for 50min, and intermittent stirring (stirring for 10min-pause for 30min-stirring for 10min) in a biaxial kneading and mixing instrument at 80℃, moisture content of 50%, 65% and 80%, respectively. The micro rheological properties of soybean protein isolate were characterized by diffusing wave spectroscopy.The results showed that with the increase of moisture content from 50% to 80%, the longer the time required for soybean protein isolate to reach the peak apparent consistency, the greater the peak consistency. The consistency curves of 50% and 65% moisture content first increased and then decreased to a stable trend, and the consistency curve of 80% moisture content increased in stages. The decrease range of apparent consistency of 10min after reaching the peak value showed that the protein system formed by higher moisture content (65%) and continuous stirring had a smaller decrease range, which was more stable than the system formed by 50% moisture content and intermittent stirring. The diffusion wave spectroscopy test showed that when the moisture content was low (50%), the protein tended to form a structure with large grid(55nm),poor continuity and low storage modulus. When the water content is increased to 65%-80%, or the water content was high (65%) combined with continuous stirring, the grid was small(5-11nm) and the storage modulus was high. It was concluded that the moisture content had a great influence on the cross-linking behavior of protein in kneading, and reducing the moisture weakened the ability of protein to form network structure. Increasing water content could promote protein aggregation and reduce the grid size. Continuous mechanical stirring could also form protein continuous structures with small grids.

Abstract:Glycinin (11S) is a kind of high-quality plant proteins, while soyasaponin (Ssa) is one of natural amphiphilic small molecules. Both of them can be used as interface stabilizers to prepare oil-in-water emulsions, but the stability of these emulsions is poor under partial environmental factors. In this study, a mixture of 11S and Ssa was used as a stabilizer to prepare a composite emulsion, and the influence of typical environmental factors (pH, temperature, freeze-thaw) on the stability of 11S-Ssa composite emulsion was investigated. Multiple light scattering technology was employed to determine the overall stability of emulsions under different conditions of heat (90℃ and 120℃) and acidification (pH 2.0,3.0 and 4.5) treatments. The particle size distribution, particle size and flocculation rate of the composite emulsion after heat, acidification and freeze-thaw treatment were characterized. The results showed that acidification treatment significantly affected the stability of these emulsions. After heat treatment, the stability of the emulsions was reduced, but the stability of the composite emulsion with Ssa mass fraction of 0.05%-0.50% was still better than the emulsion stabilized by 11S alone. The stability of the emulsion was poor at pH 4.5, and a more serious stratification phenomenon appeared. After further lowering the pH to 2.0, the stability of the emulsion was improved, and the TSI value of emulsion in each group was reduced to 8.5 within 24h. In addition, adding a certain mass fraction of Ssa 0.05%-0.50% reduced the flocculation rate of freeze-thaw composite emulsion. This study showed that adding some soyasaponin could improve the stability of 11S emulsion under heat and acidified treatment, but did not significantly improve the emulsion instability after freeze-thaw treatment.

Abstract:To delay the quality decay of germ rice, the effects of γ-rays pretreatment on protein structure, emulsifying properties and edible quality of germ rice after storage were studied. The fresh germ rice was treated with γ-rays irradiation at absorbed doses of 1kGy, 2kGy and 3kGy, stored at temperature 37℃ and relative humidity 60% for 3 months, and fresh germ rice and non-irradiated germ rice were used as the control groups to investigate the processing applicability of γ-rays pretreatment to the preservation of germ rice. The results showed that after the storage, protein components of germ rice exhibited a tendency of aggregation, the cooking and texture characteristics of the germ rice were significantly decreased. As the dose of γ-rays pretreatment increased, the turbidity, β1 folding, disordered structure and disulfide bond content of germ rice protein firstly decreased and then increased, the hydrophobicity decreased and there was no obvious aggregation of skeleton structure at 2kGy. The emulsifying activity and stability property firstly increased and then decreased. Sensory evaluation and texture determination showed that the edible quality of germ rice firstly increased and then decreased. The proper dose of γ-rays irradiation pretreatment can improve the edible quality of germ rice by adjusting the protein structure and emulsifying property during the storage. The study aimed to provide a new way for the application of radiation technology in the preservation of germ rice products.

Abstract:In order to reduce the use of essential oil as a preservative, the combinations of essential oil components were chosen and their synergistic inhibition on the quorum sensing of Erwinia carotovora was studied. Based on the minimum inhibitory concentration (MIC) and fractional inhibitory concentration (FIC) of Erwinia carotovora, four combinations of essential oil components exhibiting synergistic antibacterial effect with hexanal were selected. Subsequently, Chromobacterium violaceum 026 (CV026) and Erwinia carotovora were adopted to screen the essential oil combinations with synergistic inhibitory effect on quorum sensing was presented. Furthermore, Q value was used to verify that only the combination of hexanal and geraniol showed a better synergistic quorum sensing inhibitory effect. Similarly, the effective concentration of this combination was about 1/8 to 1/16 of that in either hexanal or geraniol. Meanwhile, this combination showed a reasonably high inhibitory effect on the quorum sensing-related indicators of CV026 and Erwinia carotovora. Among them, the inhibition rates of violacein production, swimming, swarming, extracellular polysaccharide production, and biofilm formation were 52.91%, 58.19%, 51.49%, 65.03%, and 69.84%, respectively. The combination of hexanal and geraniol showed an obvious destructive effect on biofilm formation of Erwinia carotovora observed by scanning electron microscope and confocal laser scanning microscope. The results showed that this combination which had synergistic inhibitory effect on the quorum sensing of spoilage bacteria could effectively inhibit the spoilage characteristics of spoilage bacteria while reducing the actual use of essential oil components.

Abstract:Preserved egg is a traditional Chinese food, and its hydrolysates possess anti-oxidant, anti-inflammatory and anti-cancer effects, which has promising medical prospects. However, the anti-cancer efficacy and mechanism of preserved egg are still unclear. This study investigated the influence of preserved egg simulated gastrointestinal digests (PESD) on cell proliferation and cell cycle of human hepatocellular carcinoma HepG2 cells. After in vitro digestion treatment of preserved eggs by simulated gastrointestinal tract, a cell experiment was conducted. The CCK-8 method was employed to determine the effect of PESD on cell proliferation. Propidium iodide (PI) staining was used to detect the effect of PESD on HepG2 cells cycle by flow cytometry, and the expression of cell cycle regulatory proteins was determined by western blot. The results showed that the HepG2 cells proliferation was inhibited by PESD in a dose-dependent manner, and the IC₅₀ was 4.17mg/mL. The PESD significantly increased the proportion of cells in S phase (P<0.05), and blocked the cell cycle in S phase. The protein expression levels of cyclin A, cyclin E, ATM, chk2 and CDC25A increased (P<0.05), while the protein expression of CDK2 decreased (P<0.05) after 24h treatment with 4mg/mL PESD. Therefore, it was concluded that PESD could significantly inhibit the proliferation of HepG2 cells in a dose-dependent manner. It could up-regulate the expression of cyclin A and cyclin E protein and down-regulate CDK2 protein expression through the ATM-chk2-CDC25A signaling pathway to block the HepG2 cells cycle in S phase, affect the HepG2 cells cycle progress, and inhibit the proliferation of cancer cells. The results of the study might provide a theoretical basis for the elucidation of the anti-cancer mechanism of preserved eggs.

Abstract:The biogenic amines of traditional fermented Sufu are a potential safety risk for the health of consumers. In order to develop low-salt Sufu that meets the requirements of public health and reduce the content of biogenic amines in Sufu, the study explored the effects of soup accessories on the activity of monoamine oxidase and biogenic amine accumulation during Sufu fermentation. The Sufu soups with different salt concentration, alcohol concentration and pH value were prepared, and the changes of monoamine oxidase activity and biogenic amine contents in Sufu were analyzed. The results showed that the monoamine oxidase activity decreased in the first 30d and raised in the fermentation period of 40-80d when the mass fraction of salt in the soup was 3%-7%, the volume fraction of alcohol was 15%-25%, and the pH value was 4.5-5.5. The total amount of biogenic amine and the accumulation of histamine and tryptamine basically increased and then gradually decreased after 45d. After 20-45d of fermentation, the total accumulation of biogenic amines showed a peak value, which basically maintained below 6.5mg/g, and then gradually decreased. At the end of 80d fermentation, the accumulation of biogenic amine in each experimental groups were 2.0-4.8mg/g, and the contents of histamine and tryptophan were 0.6-1.8mg/g. However, the accumulation of biogenic amines was higher in the group with 3% salt. The results of the study indicated that the activity of monoamine oxidase and the accumulation of biogenic amines were significantly negatively correlated in the Sufu fermentation process, and the total biogenic amines and their composition were affected by salt, alcohol and pH value. Among them, histamine and tryptamine were the main biogenic amines, and the tyramine content was very low. In the development of low-salt Sufu, it might be necessary to consider salt reduction combined with comprehensive measures such as high alcohol concentration and low pH value to improve its food safety and flavor quality.

Abstract:During thermal processing of starch and lipid, a large amount of starch-lipid binary complexes would be produced, which could significantly affect the quality, shelf life, and physicochemical properties of starch-based products. Jackfruit, a new type of tropical characteristic starch resource with high extraction rate and small particle size, was selected as a raw material to carry out the research. Therefore, the physicochemical properties including complexation index, pasting properties, particle size distribution, particle morphology and short-range order of jackfruit seed starch-lauric acid complexes were investigated. The cassava starch and corn starch, possessing same A-type crystalline with jackfruit seed starch, were selected as experimental reference. The results showed that jackfruit seed starch had the highest amylose content, lowest particle size distribution with highest particle size uniformity and short-range order value in comparison with cassava starch and corn starch. Besides, it showed the smallest, most regular uniform and smoothest particles, and the lower peak viscosity and relative crystallinity. Compared with complexes of cassava starch-lauric acid and corn starch-lauric acid, the complexes of jackfruit seed starch-lauric acid exhibited the highest complexation index, and higher final viscosity and relative crystallinity, more regular and smooth particle morphology with the lower peak viscosity and short-range order. In summary, shear resistance and thermal stability of jackfruit seed starch were strengthened by addition of lauric acid. The particle shape was changed from the original regular hemispherical particles to irregular lumps. And the size of the particles was increased. The recrystallization of starch was delayed, resulting in a significant decrease in relative crystallinity and short-range order. This study might provide a theoretical basis for comprehensive application of starch-basis food.

Abstract:In order to improve the quality of Pu-erh tea through inoculation fermentation, Bacillus licheniformis L1 isolated and identified from Pu-erh tea was inoculated in sterilized or unsterilized sun-dried green tea leaves to develop pure culture fermentation and enhanced fermentation (EF) of Pu-erh tea. The results showed that the mass fraction of tea polyphenols and the mass ratio of five catechins [(+)-catechin(C), (-)-epicatechin-3-gallate(ECG), (-)-epigallocatechin-3-gallate(EGCG), (-)-catechin gallate(CG) and (-)-gallocatechin gallate(GCG)] in tea leaves decreased significantly compared with control group (P<0.05), while the mass fraction of theabrownins increased significantly (P<0.05) after pure culture fermentation. Compared with normal fermentation (NF), the mass fraction of theabrownins [(6.75±0.13)%], thearubigins [(1.04±0.09)%] and soluble sugar [(5.76±0.10)%] in EF were significantly higher (P<0.05), whereas the mass ratio of six catechins were significantly lower (P<0.05), such as CG [(0.39±0.03)mg/g], (-)-epicatechin [(0.86±0.05)mg/g], GCG [(0.20±0.03)mg/g], C [(2.28±0.14)mg/g], (-)-epigallocatechin [(1.69±0.11)mg/g], EGCG [(0.33±0.02)mg/g]. In sensory evaluation for tea infusion, the scores of sweetness (3.33±0.78) and thickness (6.11±0.71) of EF were higher, while the scores of bitterness (1.33±0.50), astringency (0.67±0.50) and acidity (0.33±0.44) were lower. Colorimeter detection showed that the value of a* (25.70±0.68) and b* (77.06±1.07) of tea infusion in EF were higher and the value of L* (71.58±0.83) was lower. Amplicon sequencing of bacterial 16S rRNA and fungal ITS sequences found that B. licheniformis L1 was not always the dominant bacteria in the whole EF process (only 0.2%~0.3% in the middle and late stage of fermentation), the microbial communities in EF were different from those in NF. The relative abundances of Brevibacterium, Blastobotrys adeninivorans and Rogersella griseliniae in EF were significantly higher (P<0.05), and the relative abundances of seven microorganisms (Achromobacter, Burkholderia, Citrobacter, Erwinia, Escherichia, Klebsiella and Rhizomucor pusillus) in EF were significantly lower (P<0.05). Therefore, characteristic components were changed and sensory quality of Pu-erh tea were improved by the synergistic effect of B. licheniformis L1 with other microorganisms in enhanced fermentation.

Abstract:In order to explore the effect of grapevine leafroll disease (GLD) on the aroma quality of wine, the Cabernet gernischt which was dominantly infected with GLD from the eastern foothill of Helan mountain in Ningxia was studied. The uninfected Cabernet gernischt was used as the control group to analyze the differences in sensory characteristics and volatile components of wine. The results showed that the infected Cabernet gernischt wine emanated traditional Chinese medicine smells, such as licorice, ageratum, and dried tangerine peel smell. While the uninfected Cabernet gernischt wine showed green odors, always considered as one of the typical aroma characteristics of this kind of wine. According to volatile components analysis, the content of higher alcohols and esters with fruity and floral flavors, and C₆ alcohols with green odors in the infected Cabernet gernischt wine were significant decreased, compared with the uninfected sample. The former also registered significantly higher contents of isoamyl laurate, ethyl palmitate, n-decyl alcohol, and 2,3-pentanedione with fatty smells. The results of gas chromatography-olfactometry-mass spectrometry indicated that geranyl isovalerate, which has the characteristics of herbal aroma, was present in the infected Cabernet gernischt wine. Aroma reconstitution and aroma omission experiments confirmed that geranyl isovalerate could affect the aroma properties of traditional Chinese medicine in infected Cabernet gernischt wine. In this study, the wine aroma profiles of Cabernet gernischt infected with GLD were identified, and the underlying chemical basis was also explored, which aimed to provide a theoretical guidance to wine production and practice.

Abstract:Due to the rapid decline of jujube quality after harvest, it is very important to explore suitable processing methods to extend the preservation period of jujube. Therefore, this study explored the influence of dry conditions on the drying characteristics of jujube in air jet impingement drying, so as to improve the quality of dry jujube, shorten the drying time, obtain dry activation energy, and optimize the drying model. Self-made air jet impingement drying equipment was used to study the influence of wind speed (8.5m/s, 10.0m/s, 12.0m/s), wind temperature {60℃, 65℃, 70℃, [70℃(5h)+65℃(8h)+55℃]} on jujube moisture ratio, drying rate, effective moisture diffusion coefficient and activation energy. Eight drying models (Lewis, Page, Modified Page, Wang & Singh, Henderson & Pabis, Approximation of diffusion, Logarithmic, Simplified Fick's diffusion) were fitted and screened by DPS data statistical software. Consistent with the drying characteristics of most food materials, the air jet impingement drying process of jujube is mainly falling-rate drying. Temperature had a great influence on the changes of parameters in the whole drying process. The diffusion of water and the decline of moisture ratio were faster with the temperature increasing and the drying rate was also the higher. The highest effective diffusion coefficient was 1.22133×10-9m²/s, the minimum activation energy required was 10.39kJ/mol. Eight models were used for fitting. It was founded that the parameter coefficient (R²) value of Logarithmic model was 0.999801, the root mean square error (RMSE) value was 0.002913, the Chi-square(χ²) value was 9.332000×10-6, and this model was the optimal model. Both temperature and wind speed had effects on drying curve, drying rate curve, effective moisture diffusion coefficient and activation energy. The better drying effect was obtained at the temperature of 70℃ (5h)+65℃(8h)+55℃ and the wind speed of 12.0m/s.

Abstract:The effect of waterless keep-alive at low temperature on the muscle texture and liver biochemical characteristics of Patinopecten yessoensis were investigated. The survival rate was determined under different keep-alive conditions, and then the texture properties, lactate dehydrogenase (LDH) activity and glycogen (Glc) content of muscle, and the superoxide dismutase (SOD), catalase (CAT), glutamate-oxaloacetate transaminase (GOT), glutamic-pyruvic transaminase (GPT) and lysozyme (LZM) activity of liver before waterless keep-alive, during keep-alive (24h, 48h, 72h and 96h) and after rehydration (4h and 8h) were analyzed. The results showed that the optimal waterless keep-alive conditions for Patinopecten yessoensis were temporary rearing for 15min, moisturizing, oxygenating and keeping alive at 0℃. Under these conditions, the survival rate reached 85% when Patinopecten yessoensis was kept-alive for 96h without water. The hardness, elasticity and chewiness decreased, while the cohesiveness of Patinopecten yessoensis muscle increased. The LDH activity significantly increased (P<0.05), and Glc content significantly decreased (P<0.05) during waterless keep-alive. All the indexes were recovered partially after rehydration. With the extension of keeping alive time, the activities of SOD, CAT, GOT, GPT and LZM in Patinopecten yessoensis liver significantly increased (P<0.05), and then decreased rapidly after rehydration. Therefore, the survival rate of Patinopecten yessoensis could be improved by keeping alive without water at low temperature. Although the muscle and liver of Patinopecten yessoensis were damaged in the process of keeping alive, there was no irreversible damage. The quality of fresh Patinopecten yessoensis could still be maintained to a certain extent after rehydration.

Abstract:In order to investigate the effect of adding lactic acid bacteria (LAB) in the diet on lipid metabolism and meat quality of Sunit sheep, twelve Sunit sheep aged 3 months with good body condition [body weight (18.70±2.69)kg] were selected, and then randomly divided into two groups with six sheep each. The control group was fed a basic diet, and the LAB group was supplemented with compound LAB at 1.5×10⁹CFU/g based on the diet of the control group. The feeding period lasted for 90d. Meat quality, blood lipid indexes, fatty acid composition and the expression of lipid metabolism genes were measured after slaughter. The results showed that compared with the control group, the addition of LAB significantly increased the content of intramuscular fat and the value of pH in 24h (P<0.05), while significantly reduced L* and cooking loss (P<0.05) of longissimus dorsi muscle. The analysis of serum lipid metabolism showed that the dietary supplementation with the LAB decreased the low-density lipoprotein cholesterol and triglyceride of Sunit sheep (P<0.05). The contents of γ-linolenic acid, eicosatrienoic acid, arachidonic acid, eicosapentaenoic acid and eicosatetraenoic acid in the LAB group were significantly higher than the control group (P<0.05). Dietary supplementation of LAB could affect lipid-related indexes and fatty acid composition of Sunit sheep. Furthermore, the addition of LAB to the diet significantly inhibited the expression of AMP-activated protein kinase α2 gene in the longissimus dorsi muscle of Sunit sheep (P<0.05), and promoted the expression of acetyl-coa carboxylase, peroxisome proliferator-activated receptor γ and sterol regulatory element binding protein-1C (P<0.05). Therefore, dietary supplementation of LAB could regulate lipid metabolism in Sunit sheep through inhibiting AMP-activated protein kinase α2-acetyl-coa carboxylase signaling pathway.

Abstract:In order to explore the effects of different thawing methods on the oxidation of mutton lipid and protein, semimembranosus and longissimus dorsi muscle of Kazakh sheep were taken as the research objects to determine the oxidation indicators. Moreover, the protein degradation in different parts was observed by SDS-PAGE. The results showed that after refrigerated thawing, the peroxidation values of semimembranosus and longissimus dorsi muscle were 3.33mmol·kg-1 and 4.58mmol·kg-1, and the mass ratios of malondialdehyde were 0.16mg·100g-1 and 0.24mg·100g-1. The carbonyl molality were 3.59nmol·mg-1 and 4.62nmol·mg-1, and the sulfhydryl molality were 41.26nmol·mg-1 and 38.73nmol·mg-1. The mass of the hydrophobic bond were 64.72μg and 75.25μg. After static thawing, the peroxide values of the two muscles were 4.91mmol·kg-1 and 5.79mmol·kg-1, and the sulfhydryl molality were 38.40nmol·mg-1 and 33.40nmol·mg-1 . Total protein solubility were 184.50mg·g-1 and 171.90mg·g-1, and sarcoplasmic protein solubility were 69.07mg·g-1 and 60.77mg·g-1. The myogenic protein solubility were 115.43mg·g-1 and 111.13mg·g-1. After air thawing, the peroxide value of the two muscles were 7.00mmol·kg-1 and 7.71mmol·kg-1, and the mass ratio of malondialdehyde were 0.33mg·100g-1 and 0.44mg·100g-1. The carbonyl molality were 13.19nmol·mg-1 and 14.06nmol·mg-1. The sulfhydryl molality were 17.46nmol·mg-1 and 12.56nmol·mg-1, and the hydrophobic bond mass were 75.20μg and 82.47μg. The oxidation degrees of thawing methods in ascending order were refrigerated thawing, static thawing, ultrasonic thawing, microwave thawing and air thawing(P＜0.05). According to the results of SDS-PAGE, the protein of mutton had different degrees of degradation after freezing and thawing. Ultrasonic thawing had a greater impact on the degradation of longissimus dorsi protein. This study showed that the refrigerated thawing and static thawing induced to lower oxidation degrees and better quality of mutton, which were more suitable for thawing frozen mutton.

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.