Abstract:Carotenoids are pigments widely found in fruits and vegetables. There are many stereoisomers of carotenoids due to the large number of conjugated double bonds present in the molecules. The natural carotenoids in fruits and vegetables mainly exist in all-trans (E) configuration. However, the proportion of cis-isomers of carotenoids detected in human bodies is high. Configuration transformation of all-E -carotenoids, and the relationship between isomer types and bioactivities of carotenoids have attracted the attention of scholars. Through literature and product research, domestic and international regulations comparison, this study reviews preparation of cis-isomers, the detection and analysis of various isomers, stability evaluation, physiological activity and application of carotenoid isomers, providing a reference for the further study on configurations of carotenoids and their application.

Abstract:China is a large country in the production of eggs. Eggs are very popular because they are cheap, high in quality and nutritious. Antioxidant active substances have been found in egg protein and protein derivatives. Therefore, in this review, the research progress on the antioxidant activity of functional components derived from egg protein and the corresponding product development were introduced, and the various models used to study the antioxidant activity of egg components were summarized, including in vitro chemical models, cell models, rat/mouse models and Caenorhabditis elegans models. The future research trend and practical application were prospected to provide a reference for the research and development of bioactive substances from egg sources.

Abstract:Pullulanase is of high industrial value in the fields of starch processing, functional medicine polysaccharide preparation and beer brewing. However, the high costs of the separation and purification of catalytic products and non-renewability of free pullulanase limit its industrial application. Magnetic nanoparticles possess unique features, such as reusability, magnetic recovery and specific surface area, which is helpful to solve the problems of industrial application of free enzymes. The immobilized enzyme complex Fe₃O₄@Histidine/PulASK was prepared by immobilizing PulASK from Anoxybacillus sp. SK3-4 onto the Fe₃O₄@Histidine magnetic nanoparticles. The enzymatic properties and kinetic parameters of the immobilized enzyme was investigated. In comparison with free PulASK, the optimal reaction temperature of Fe₃O₄@Histidine/PulASK increased from 60 ℃ to 65 ℃, while their optimal reaction pH was the same. The residual activity of immobilized enzyme was 62% after 7 h incubation at pH 6.0 under 60 ℃, while that of free enzyme was only 30%. The enzyme kinetics data analysis revealed that K_m of the free enzyme PulASK was 4.7 mmol/L at pH 6.0 under 60 ℃, which was 1.47 times as that of Fe₃O₄@Histidine/PulASK. The k_cat value of Fe3O4@Histidine/PulASK was 350 s^-1, which was comparable to that of PulASK. The k_cat /K_m values of Fe₃O₄@Histidine/PulASK was 1.57 times as that of PulASK. Furthermore, Fe₃O₄@Histidine/PulASK remained more than 50% active after 9 cycles of usage. Compared with PulASK, Fe₃O₄@Histidine/PulASK obtained remarkable thermal stability and reusability, exhibiting potential application value in food industry.

Abstract:Nanostructured lipid carriers (NLCs) are an effective means to improve the oral bioavailability of curcumin (Cur), but the stability and application fields of Cur-NLCs prepared under conventional conditions need to be studied and explored. The gel microspheres with multiple responsiveness were constructed by the composite of Cur-NLCs and magnetic gelatin using electrospray. The particle size, appearance, micromorphology, storage stability, multiple responsiveness and release characteristics of the microspheres containing different mass fractions of magnetic gelatin were studied. The results showed that the prepared microspheres were rough ellipsoid, and the particle size decreased from （231.67±2.82） μm to （175.22±1.96） μm with the increase of magnetic gelatin mass fraction. Meanwhile, the microspheres had good stability during storage, and the retention rate of Cur was generally above 80% after 28 d storage at 4 ℃. Multiple response experiments showed that the microspheres were sensitive to magnetic, temperature, acidic pH and NaCl. The in vitro release test showed that the microsphere had an S-shaped Cur release curve, and the pH and NaCl of the release medium affected the release behavior of Cur. The research showed that the constructed microsphere could be an intelligent delivery system with multiple responsiveness and good stability, showing the practical significance for the expanded application of Cur-NLCs in the food industry and the development of intelligent delivery system.

Abstract:To slow down the fatty acid abortion and prolong the storage period of rice with remained germ, electron beam irradiation was used to treat the rice with remained germ and its quality changes during storage were investigated. The results showed that after 0.5 kGy electron beam irradiation, the germ retention rate, broken rice rate and waist burst rate of rice with remained germ showed little change, and the lipase activity decreased by 28.17%. When the irradiation dose was increased to 1.0 kGy, the rate of waist burst of rice with remained germ increased significantly. During storage, the moisture content of rice with remained germ treated with electron beam decreased rapidly, while the increase rate of fatty acid value slowed down. In addition, the lipase of untreated samples rised first and then decreased during storage, while the lipase activity of samples treated with electron beams linearly decreased during the process. Under the storage conditions of 25 ℃ and 37℃, the shelf life of untreated samples was 15 d, while electron beam treatment could significantly prolong the shelf life (≥60 d). In terms of taste quality, after storage at 25 ℃ for 120 d, the comprehensive score of 0.5 kGy treated samples was 69.9, which was close to that of the corresponding untreated samples (70.6). Increasing the radiation dose and storage temperature accelerated the deterioration of the taste quality of rice with remained germ. In conclusion, electron beam irradiation treatment is an effective method to prolong the storage period of rice with remained germ.

Abstract:In order to improve the stability of ethosomes, ceramide III (Cer3) was used to modify the ethosomes for the first time. The effect of Cer3 amount on the stability of ethosomes was investigated. Subsequently, retinyl palmitate (RP) was loaded into Cer3 ethosomes as a lipid-soluble active substance to investigate the stability, stabilization mechanism and in vitro release performance of RP-Cer3 ethosomes. The results showed that the best stability of Cer3 ethosomes was achieved at 1 mg/mL Cer3. When the RP content of RP-Cer3 ethosomes was 2 mg/mL, the particle size was (68.4±1.1) nm. The appearance and particle size insignificantly changed when stored at room temperature for 120 d. X-ray diffraction (XRD) and total reflection Fourier infrared (FTIR) indicated that RP was well encapsulated in the ethosomes, at the meanwhile, FTIR also indicated that there was hydrogen bond interaction between RP and the ethosomes. The results showed that the addition of Cer3 could reduce the fluidity of ethosomes and thus improve their stability, and RP-Cer3 ethosomes had better in vitro release performance.

Abstract:β-(2,6) levansucrase (LS) with high thermostability was identified and the efficient synthesis of levan by levansucrase was studied. High-temperature molecular dynamics simulation was used to screen the LS with potential high thermostability. The target enzyme was heterogeneously expressed in Escherichia coli BL21(DE3) and purified through one-step Ni²⁺-affinity purification. The thermostability of LS was determined by incubating the enzyme at different temperatures, and the highest conversion was obtained through the optimization of conditions. The Cedi-LS showed the highest activity at 65 ℃, which was much higher than the other identified LSs. Meanwhile, Cedi-LS remained more than 90% active when incubated at 45 ℃ for 72 h, and it also remained more than 60% of its initial activity at 55 ℃ for 60 h, exhibiting excellent thermostability. The Cedi-LS produced oligosaccharides, low molecular weight (LMW) β-(2,6) levan, and high molecular weight (HMW) β-(2,6) levan simultaneously during reaction. When the temperature decreased from 65 to 35 ℃, Cedi-LS tended to produce HMW-levan with a Mw of 8.4×106 Da. At pH 5.5 and 35 ℃, the equilibrium conversion ratio from sucrose to levan was 41.4% with 30% sucrose and 20 μg/mL enzyme. In summary, an extreme thermostable LS was screened which could efficiently produce levan with different molecular weights.

Abstract:Duck egg contains rich protein and nutritional components. Duck egg white contains lysozyme. Lysozyme is the main allergenic protein in duck egg. People may have risk allergic to duck egg. The lysozyme from duck egg white was isolated and purified by and ultrafiltration and ion exchange. The lysozyme with higher purity was achieved by the comparison of polyacrylamide gel electrophoresis. For the antigenicity evaluation of lysozyme from duck egg white, western blotting was used to analyzed the binding ability of the specific anti-lysozyme rabbit serum and mixed serum pool of three egg allergic patients with duck egg white lysozyme IgE. The results showed that the IgE binding ability was quite significant, and there was cross-reaction between hen egg lysozyme and duck egg lysozyme. At the meanwhile, the results confirmed that eating duck eggs could cause allergenicity, and it also provided useful information for allergic patients whether they could eat duck eggs or not.

Abstract:There are many unannotated proteins with unknown functions in cereals, which are difficult to be verified by experiments. However, computational methods have become one of the mainstream methods to evaluate the functions of the cereal proteins. In this study, maize, wheat, indica rice and japonica rice proteins were studied, and their structural domain interaction information was obtained from the related databases. The protein-protein interaction information was obtained and the protein-protein interaction network was constructed, starting from the relatively stable domain information of protein and combining the AdaBoost algorithm. Combining it with the biomolecular structure similarity network obtained by blast, the functions of the cereal proteins were predicted based on the cooperative classification and multi-layer perceptron algorithms. Results showed that both of cooperative classification algorithm and multi-layer perceptron algorithm could accurately predict the functions of the proteins. Moreover, collaborative classification algorithm showed a better recall rate, whereas multi-layer perceptron algorithm showed a better accuracy. This sudy revealed a new idea and method for the unannotated protein investigation, and provided a strong guarantee for cereal processing and nutrition research.

Abstract:The frozen Takifugu obscurus is delicious, but there are no products related to room-temperature fish soup in the market. In order to solve the problems of instability of fish soup such as flocculation and stratification during storage and to prolong its storage period, this study investigated the effects of homogenization conditions on the stability of Takifugu obscurus soup based on the average particle size, dispersion coefficient and ζ-potential of micro- and nano-particles in fish soup, and the effects of different sterilization methods on the nutrition and flavor quality of fish soup were studied. The results showed that the best stability of fish soup was achieved when homogenized under 30 MPa at 60 ℃ for 2 times. By comparing different sterilization methods, the loss of nutrients in the ultra-high temperature sterilization group was smaller than that in the pasteurized group or in the thermal temperature sterilization group. In addition, the contents of total nitrogen, amino acid nitrogen and collagen in the fish soup decreased by 0.92%, 2.73% and 4.38%, respectively, compared with the control group. The flavor components were most similar to those in the control group, and only trans-2-octenal as a characteristic flavor component increased. The pasteurized group had low cost, however, its storage time was only 6 weeks. The storage time of fish soup in the thermal sterilization group was up to 20 weeks, but the relative content of the compounds expressing the steaming flavor increased, which had an adverse effect on the flavor of fish soup. This study could provide theoretical reference and data support for the industrial production of puffer fish soup.

Abstract:In order to determine the optimal picking time of fresh Shiitake mushroom, the taste components (free amino acid and 5’-nucleotide) in fresh fruiting bodies of Shiitake mushrooms harvested at different growth stages were studied, and the data were statistically analyzed by principal component analysis and cluster analysis. Results indicated that the levels of free amino acids and 5’- nucleotides in Shiitake mushroom harvested at different stages of maturity varied, and significant differences existed among all samples based on maturity. Principal component analysis (PCA) combined with amino acid and 5’-nucleotide data could clearly discriminate samples from different maturity, with results obtained from hierarchical cluster analysis (the euclidean distance of 4.0) being in agreement with those of PCA. The contents of amino acids and 5’-nucleotides in fresh Shiitake mushroom fruiting bodies, the equivalent umami concentration (EUC), the sensory evaluation and the comprehensive evaluation scores reached the peak at the bud stage (T1). And the conventional picking periods, i.e., six degree of maturity (T4) and eight degree of maturity (T5), were at the middle stage. The optimal picking time to ensure the appearance, economic efficiency, EUC value, sensory quality and comprehensive evaluation score of Shiitake mushrooms remained at a relatively high level and under our experimental conditions, was determined to be T4. The results could serve as a theoretical foundation for determining the optimal harvest period for Shiitake mushrooms and other similar agricultural products with high quality.

Abstract:The volatile components and the key aroma components of black tea prepared using three tea cultivars (Jin Peony, Jin Guanyin, Xiaocai tea) by the ‘Zunyi Red’ processing technology were determined and analyzed through sensory evaluation and gas chromatography mass spectrometry technology. The results of sensory evaluation showed that the final scores of Jin Peony, Jin Guanyin and Xiaocai tea were 90.50, 89.75 and 85.85, respectively. The quality of ‘Zunyi Red’ black tea made from Jin Peony was the best, followed by Jin Guanyin, and the quality of Xiaocai tea was worst. A total of 78 aroma compounds were identified by GC-MS from the volatile components of three different tea varieties of ‘Zunyi Red’ black tea, namely, Jin Peony, Jin Guanyin and Xiaocai tea. There were 37, 33 and 42 kinds of aroma compounds, respectively, and 17, 17, and 15 types of special aromas. The aroma compounds of three tea varieties included esters, alcohols, ketones, phenols, aldehydes, alkanes, acids, and so on. The relative content of flower and fruit aroma substances from three tea varieties ranked in the order of Jin Peony (36.00%) > Jin Guanyin (35.07%) > Xiaocai tea (19.66%). According to the sensory evaluation and GC-MS detection, the ‘Zunyi Red’ black tea made by Jin Peony had a best quality, followed by Jin Guanyin, and that of Xiaocai tea was the worst. This study could provide a theoretical basis for maintaining and improving the quality of ‘Zunyi Red’ black tea.