Abstract:As one of the main food components, starch plays a very important role in human diet. Steaming, boiling and extrusion are three aqueous phase and high temperature treatments commonly used in the processing of starch-based food, significantly affecting the granule morphology, molecular structure, crystal type, gelatinization, retrogradation and digestion of starch. In this work, the effects of aqueous phase and high temperature treatments (steaming, boiling and extrusion) on the structure and properties of starch were reviewed in order to provide theoretical basis for the quality improvement of starchy food.

Abstract:Rapid and sensitive detection of various hazard factors in food is the key to ensure food safety and improve human health. Immunochromatographic test strip(ICTS) has become the most popular technique for rapid screening and on-site detection of food safety, exhibiting the advantages of low cost, simple operation, short assay time and no need of complex equipment and professional technicians. Particularly, the emergence of multiplex ICTS greatly improves the detection flux and shortens the overall analysis time, providing an effective technical support for simultaneous detection of various hazard factors in food. In this paper, five common signal output modes (colorimetry, fluorescence, and surface enhanced Raman scattering, chemiluminescence and magnetic signal) were introduced, the latest research progress on simultaneous detection of food hazard factors by integrating the above-mentioned signal outputs with multiplex ICTS platform was reviewed. The article aims to provide a certain theoretical guidance for the design and construction of multiplex ICTS technology and its application in food safety analysis.

Abstract:Carbon nanoparticles, namely carbon dots, are widely used in many fields, such as chemical sensing, biological sensing, biological imaging, drug delivery and food safety since they possess various advantages including tunable fluorescent emission characteristics, low cost and low toxicity. Recently, foodborne carbon nanoparticles have been found in bread, biscuit, instant coffee, commercial beverage, milk and a variety of thermal-processed meat products. They could be directly used as fluorescent probes and imaging reagents. This article reviewed the origin of foodborne carbon nanoparticles, their properties and applications, providing theoretical background and development direction for further and intensive study of carbon nanoparticles in food.

Abstract:In this study, α-glucanase derived from Chaetomium globosum was synthesized and optimized according to the codon preference of <>Pichia pastoris, and then successfully heterologous expressed in Pichia pastoris GS115. Through the high-copy screening and single-factor optimization of shaike flask fermentation, the enzyme activity of recombinant α-glucanase was increased from 2.692 U/mL to 47.915 U/mL. The crude enzyme was purified to electrophoretic purity by two-step chromatography through Hitrap Q HP and Hitrap SP HP. The purification factor reached 40.83, with the recovery of 24.15%. And the specific activity of purified enzyme reached 277.61 U/mg. The optimal reaction temperature and pH were 60 ℃ and 5.5, respectively. The enzymatic activity kept stable within 20~50 ℃ and pH 4.5~8.5. The presence of 10 mM Fe²⁺ activated the enzyme, whereas 0.1~10 mM Cu²⁺ inhibited the enzyme. The higher concentration of Cu²⁺, the stronger inhibition of enzyme. Affinity study indicated that the recombinant enzyme had the higher affinity towards substrates with higher molecular weight. Dextran T2000 was the optimal substrate of the enzyme.

Abstract:The high content of soluble carbohydrates in rice causes the blood sugar to rise quickly after eating, and thus rice is not suitable for diabetic patients. In this experiment, oat flour and potato whole powder were used as the main raw materials to develop a kind of fresh extruded rice(FER) suitable for diabetics. The results showed that the glycemic index of in vitro digestion experiment was the lowest and the GI value was 68.36 when the addition of pumpkin powder was 15%. The cross section was smooth and the structure was tight under scanning electron microscopy. After cooking, the heating water absorption rate and expansion rate were as high as 191.35% and 266.67%,respectively. The soluble solid content of rice soup was only 26.042 mg/g. The texture of FER was good, the grains were full and the sensory score was the highest.

Abstract:The heat treatment of electric cooker can enhance the flavor of rice by physical means, however, there is still a lack of corresponding mode in improving the flavor of aged rice. The crucial flavor compounds contributing to the stale odor of rice were identified as hexanal, octanal, nonanal and decanal analyzed by gas chromatography-mass spectrometry combined with flavor threshold analysis. Using sensory evaluation and electronic nose analysis as the evaluation indexes in adjusting the immersion parameters, it was found that soaking at 50 ℃ for 10 minutes had a significant effect on improving the odor of aged indica rice, which was similar to the overall flavor profile of the fresh rice. Compared with the untreated aged rice, the lipase activity of aged rice decreased by 78.2%, the peroxide value dropped to 1.52×10^-2 mmol/kg, and the molality of malondialdehyde only increased by 7.5% after soaked at 50 ℃ for 10 minutes. Pre-soaking effectively delayed the hydrolysis and oxidation of lipids in rice grains and reduced the formation of off-flavor compounds during the cooking process of aged indica rice. The results of this study provided a reference for the design and improvement of flavor refreshness curve of aged indica rice cooked in electric cooker.

Abstract:The molecular weight distribution, DPPH radical scavenging ability, ·OH scavenging ability, ABTS radical scavenging ability, ORAC value and ROS scavenging ability of corn oligopeptides (COPs) before and after simulated digestion by pepsin and trypsin in vitro were measured, in order to explore the effect of simulated gastrointestinal digestion on the antioxidant activity of COPs. The results showed that the relative molecular weight of most peptides in COPs was less than 1000 u. After simulated gastric and intestinal digestion, the weight average molecular weight decreased by 1.47% and 0.05%, respectively, and the free radical scavenging capacity of ABTS increased to a certain extent, 25.47% and 1.39%, respectively. Before and after digestion in simulated gastric environment, the IC50 values of DPPH free radical scavenging capacity were about 1.41 and 1.50 mg/mL, and the IC50 values of ·OH scavenging capacity were about 10.3 and 12.3 mg/mL, respectively. Before and after digestion in simulated intestinal environment, the IC₅₀ values of DPPH free radical scavenging capacity were about 1.39 and 1.48 mg/mL respectively, and the IC₅₀ values of ·OH scavenging capacity were about 8.1 and 9.5 mg/mL, respectively. After simulated gastric digestion, ORAC value decreased by 10.4%, and ROS scavenging ability of 100 μg/mL and 400 μg/mL COPs increased by 1.42% and 16.78%, respectively. After simulated intestinal digestion, ORAC value increased by 1.4%, ROS scavenging activity of 100 μg/mL COPs decreased by 1.71%, and ROS scavenging activity of 400 μg/mL COPs increased by 2.61%.

Abstract:The moisture status, moisture content and moisture distribution of beef jerky at different hot air-drying temperatures (50~70 ℃) within drying time (120~180 min) were investigated by low-field nuclear magnetic resonance and its nuclear magnetic resonance imaging technology. Results: The average drying rates at three drying temperatures were 0.226 5, 0.277 9, and 0.353 9 g/(g·min), and the drying effect of beef jerky mainly depended on its non-flowing water content. The drying rate of dried meat could be significantly increased by increasing the temperature during the hot-air drying process, and the migration of bound water, non-flowing water and free water could also be accelerated. During the drying process, the non-flowing water changed after the combination of free water and bound water. The changing trend of peak area and peak proportion under different hot air temperatures was consistent, and more significant curve changes could be observed under higher temperature. There was a good linear relationship between the moisture content of beef jerky and the peak area, and the linear regression equation of drying at 70 ℃ was y=323.34x- 6 092.77（R²=0.975 0). The T1-weighted image of longitudinal relaxation time showed that the hydrogen proton density distribution was relatively uniform and the drying quality was better during the drying of beef jerky at 70 ℃. The difference comparison of three drying temperatures could provide a theoretical basis for the improvement of jerky quality, product development and energy saving in the future.

Abstract:A discriminant model of muskmelon origin was established to provide theoretical basis for geographical origin trace of muskmelon. In this study, the contents of strontium isotopes m（⁸⁷Sr）∶ m（⁸⁷Sr） and various mineral elements of melon species in melon samples collected from Hami, Turpan, Bazhou and Aksu of Xinjiang were determined by thermoelectric ionization mass spectrometer and inductively coupled plasma mass spectrometer. The discriminant analysis model was established in combination with principal components and discriminant analysis in stoichiometry to conduct discriminant analysis on melon from different producing areas in Xinjiang. Multiple comparison results showed that Al, Fe and Rb contents of Hami melon were significantly higher than those of Turpan, Bazhou and Aksu. The contents of Ca and Na in melon in Bazhou were significantly higher than those in Turpan, Hami and Aksu. The m（87Sr）∶m（86Sr） of melon in Bazhou and Aksu significantly higher than m（⁸⁷Sr）∶ m（⁸⁷Sr） of melon in Hami and Turpan. The discriminant model was establishm（⁸⁷Sr）∶ m（⁸⁷Sr）ed based on m（⁸⁷Sr）∶ m（⁸⁷Sr） and 8 mineral elements, including Ca, K, Na, V, Cr, Ni, As and Rb. The overall discriminative rates of back-substitution and leave-one-out cross-validation of four-ground melon were 100% and 93.8%, respectively. It could be feasible to discriminate muskmelon from different producing areas in Xinjiang by m（⁸⁷Sr）∶ m（⁸⁷Sr） and various mineral elements combined with stoichiometry.

Abstract:This work aimed to study the antibacterial activities of crude and refined extracts of total flavonoids from tartary buckwheat bran on pathogenic bacteria, to analyze the flavonoid monomer components and evaluate the antibacterial activity of different flavonoid glycosides. The antibacterial activity of crude and refined total flavonoids and their four flavonoid glycosides was investigated by the diffusion plate method and double dilution method. Qualitative and quantitative determination of total flavonoids in tartary buckwheat bran were detected by high-performance liquid chromatography (HPLC). The refined extract of tartary buckwheat bran had stronger antibacterial activity on Staphylococcus aureus, Micrococcus luteus, Enterococcus, Escherichia coli, Shigella, and Salmonella than the crude extract. The main flavonoids of tartary buckwheat bran were rutin, kaempferol-3-O-rutin, quercetin and kaempferol. The total flavonoid content of refined extract was 2.84 times that of the crude extract. The antibacterial activities of four flavonoid monomers showed a certain structure-activity relationship. Among them, quercetin showed good antibacterial activity against all tested bacteria.

Abstract:In order to explore the optimal fermentation process and parameters of pumpkin seed yoghurt, pumpkin seed and milk were used as the main raw materials. The comprehensive evaluation method was used to optimize the fermentation process and parameters of pumpkin seed yogurt based on the single factor test and response surface method combined with fuzzy mathematics. The results showed that the optimum fermentation parameters of pumpkin seed yoghurt were as follows: the addition of 50% pumpkin seed pulp by volume fraction with concentration of 17%, 50% milk by volume fraction, 9% sucrose was by mass fraction, 12 kinds of lactic acid bacteria yoghurt bacteria as the starter, the addition of 5 g/L bacteria and the fermentation time of 6 h. Under this condition, the sensory score of pumpkin seed yoghurt was 8.27, with color of slightly green, delicate taste, the aftertaste retaining pumpkin seed flavor, and good solidification.

Abstract:The liquid multistage fermentation of a traditional Chinese medicine prescription (JGZF) was carried out with multiple strains. The changes of trace elements, antioxidant activity in vitro, antibacterial activity and other effective components of JGZF were investigated under three treatment methods (direct boiling, natural fermentation and artificial fermentation). The trace elements were detected by atomic absorption spectrometry, and the antioxidant activities in vitro were detected by ultraviolet visible spectrophotometer, including the superoxide dismutase(SOD) activity, DPPH radical scavenging capacity, hydroxyl radical scavenging capacity and the total polyphenol content. The antibacterial activity was determined by Oxford cup method and evaluated based on the diameter size of bacteriostatic ring. The pharmacodynamic components of JGZF were detected by UPLC-Q-TOF-MS/MS non-target metabonomics detection. The results showed that the contents of trace elements including Zn, Cu, Fe and Ca in JGZF after the natural fermentation and artificial fermentation were significantly increased compared with those of direct boiling. The antioxidant activity in vitro of JGZF was significantly improved by artificial fermentation, in which SOD activity was increased by 1.5 times, DPPH radical scavenging capacity was increased by 2.2 times, hydroxyl radical scavenging ability was increased by 4.2 times, and the content of total polyphenols increased by 2.2 times. The antibacterial activity of JGZF against Salmonella and Escherichia coli was stronger, however, the antibacterial activity against Shigella and Staphylococcus aureus unchanged or slightly decreased. After the artificial fermentation of JGZF, the content of liquid components increased or decreased, including the essential amino acid L-phenylalanine, anti-inflammatory substances such as baicalein increased by hundreds of millions of times, while the contents of huoxuetong schisandrin B, 7-hydroxycoumarin and pesticide residue were significantly decreased.

Abstract:Three different body parts of yak meat from five regions of Qinghai Plateau were selected to analyze, evaluate and compare the nutritional compositions, providing a basis for the development and utilization of yak meat reprocessed products in Qinghai Plateau. SPSS 19.0 was used to conduct the principal component analysis and multiple comparative analysis of nutritional compositions of yak meat from the same body parts in five different regions and the different body parts in the same region in Qinghai plateau, respectively. At the same time, the differences among yak meat in Qinghai plateau region and other provinces, and among yak meat and other varieties of beef were also compared. Finally, the indicative compositions greatly contributing to the yak meat quality were evaluated comprehensively. There were differences in indicative nutrients, but they all had the characteristics of 'high protein, low fat and rich nutrition'. The trend of positive correlation between the nutrients of yak meat and local altitude was related to grazing and feeding management. Yaks at high altitudes got more nutrients by eating grasses with more nutrients and energy. In addition to the above-mentioned factors, the nutritional compositions of different varieties of beef were also related to the life behavioral patterns, eating and feeding conditions, semi-wild grazing environment and other factors. After comprehensive evaluation, the quality of yak meat from Longmen township, Tianjun county, Haixi prefecture and Shaliuhe town, Gangcha County, Haibei Prefecture were better than that from other regions. The reason was that the precipitation of climatic factors was one of the main factors of herbage growth, which indirectly affected the quality of yak meat. This study could provide a basis for quality control of yak meat in Qinghai Plateau with high nutritional value.