Abstract:Starch, as a biodegradable raw material with abundant sources, is widely used in food, medicine, textile and other industries. However, the native starch has low solubility and viscosity in cold water, and it usually needs to be heated into paste for use, which causes inconveniences in application. Cold-water-soluble starch with elevated solubility and viscosity in cold-water, is divided into pre-gelatinized starch and granular cold-water-soluble starch according to the integrity of granular morphology. The two types of modified starch are mainly prepared by physical methods, but their preparation principles are different, and their properties and application range are also different. In this paper, the preparation principle and research status of pre-gelatinized starch and granular cold-water-soluble starch are compared, and the particle morphology, cold water solubility, gelatinization property, thermodynamic property and application of corresponding modified starch are summarized systematically, aiming to provide basis for the development and application of new cold-water-soluble starch.

Abstract:Aspergillus flavus is one of widely distributed fungal, which infects crops related foodstuffs and feeds, especially maize and peanut, upon cultivation, storage, manufacture, and transportation. A. flavus produces a lot of toxic secondary metabolites, and among them aflatoxins (AFs), recognized as Group 1 carcinogens, are the most important ones. AFs contamination severely affects food safety, brings huge economic losses and trade disputes. More importantly, AFs have high toxicity, high carcinogenicity, mutagenicity, and immune suppression, which severely threaten human and animal health. Therefore, the biosynthesis, regulation, prevention of AFs are the critical and hot points of the research of food safety. This study clarified the AFs biosynthesis process and its related regulatory mechanism, introduced various effective prevention methods, emphasized the effects of environmental factors (light, temperature, water activity, nutrient, pH value, oxidative stress) on AFs biosynthesis, illustrated different regulators involved in AFs regulation, and introduced diverse strategies including physical, chemical, and biological methods for AFs control and prevention, summarized the prevention strategies for AFs contamination, and prospected the key research fields, prevention and control measures in the future.

Abstract:Some of the Aspergillus flavus have caused serious pollution to agricultural products. Affected by related genes, Aspergillus flavus will produce a mycotoxin, aflatoxin, which poses major health threats to humans and animals. Aflatoxin contamination may occur in the field, storage or transportation. There are many strategies to prevent aflatoxin from entering the food chain, among which the use of biological method, e.g. microorganisms to control aflatoxins pollution has attracted rising attention from researchers and has been gradually adopted by farmers. It has been widely reported that microorganisms and their metabolites can effectively reduce the pollution of Aspergillus flavus and aflatoxins to food crops and products. Functional components are mainly metabolites of microorganisms, including polypeptides, small molecular organic compounds, organic acids, antibiotics and enzymes. Because of the great economic impact of aflatoxin pollution on crops and its toxicological effects on humans and animals, this problem has attracted great attention all over the world. In this paper, the types of microorganisms, including Bacillus spp., Lactobacillus spp., yeast, Streptomyces spp. and some marine microorganisms, and related functional components that have antagonistic effects on Aspergillus flavus and aflatoxins were all reviewed. Moreover, the mechanism of inhibition on aflatoxins and the degradation of aflatoxins were also summarized, aiming to provide reference basis for biological control of Aspergillus flavus and aflatoxins pollution.

Abstract:Granulation is a physiological disorder of juice sacs in citrus fruit, which made juice sacs become hard and dry and damaged the internal quality of citrus fruit. Honey pomelo is a thick-skinned citrus fruit, and it is hard to identify the granulation levels by observing the outer peel and fruit shape. In this study, a rapid and non-destructive detection method based on near-infrared transmittance spectroscopy combined with machine vision technology was used to classify honey pomelo by the granulation levels. 600 honey pomelos in different growth stages were harvested and divided into five granulation levels according to the granulation changes of samples. Spectral data of samples were recorded in the range of 900~1700nm, which were combined with chemometrics to research the chemical changes of inner quality caused by granulation. Machine vision technology can be used to study the physical changes of external characteristics caused by granulation. Therefore, comparison of the traditional method, this method has better predictive performances in classification models. In particular, the predictive performances of accuracy, sensitivity, and specificity were respectively not less than 0.9700, 0.9231, and 0.9874 in the SPA-KNN (successive projections algorithm-K nearest neighbor) predicted model. The results showed that this method could be used for classification and evaluation of granulation, and had a great potential. The method provides a reference and theoretical basis for the online sorting and inner quality detecting of thick-skinned fruits.

Abstract:In order to improve the shelf life of white Hypsizygus marmoreus, the medium and short wave infrared radiation was used to dry white Hypsizygus marmoreus, and effects of drying temperature (60,70, 80,90℃) and drying power (675,900, 1125,1350W) on drying characteristics of white Hypsizygus marmoreus were investigated. Drying process were fitted through 7 commonly used drying models of agricultural products and a kinetics model of middle and short wave infrared drying in white Hypsizygus marmoreus was established. Results showed that both drying temperature and drying power had effects on the drying process of white Hypsizygus marmoreus. However, drying temperature had a greater impact on the drying process. The moisture content of drying base was obviously declined with the increase of drying temperature. Drying process was controlled by internal moisture diffusion, and the slowdown phase was the main stage. The predicted value of the Page model fitted well with the experimental value, which could accurately reflect the infrared drying process of the white Hypsizygus marmoreus, and could be used to describe the infrared drying process of white Hypsizygus marmoreus quantitatively under different drying temperatures and powers. When the drying power was 1125W, the effective moisture diffusion coefficient of white Hypsizygus marmoreus was increased with the increase of drying temperature, which was from 2.723×10-9m²/s to 9.008×10-9m²/s accompanied by the drying temperature raising from 60℃ to 90℃. At drying temperature of 70℃, the effective moisture diffusion coefficient increased from 4.847×10-9m²/s to 5.243×10-9m²/s when the drying power increased from 675W to 1350W. The midium and short wave infrared drying activation energy of white Hypsizygus marmoreus was 39.45J/mol. This study aims to provide the theoretical reference to the medium and shot wave infrared radiation drying process design, equipment selection, and production control of white Hypsizygus marmoreus.

Abstract:Effects of ultrasound combined with calcium impregnation on physico-chemical properties and lycopene of cherry tomatoes during storage were studied,and the mechanisms were further elucidated. The handness, color, and lycopene content of cherry tomatoes were determined by texture analyzer,color difference meter and HPLC. Meanwhile, the structure of lycopene was also investigated by nuclear magnetic resonance(NMR). The results showed that ultrasound combined with calcium impregnation treatment could enhance the permeation of Ca²⁺ into the tissue of cherry tomatoes, which effectively delayed the decline of hardness,inhibited the increment of browning index, weight loss ratio and decay rate, and maintained titratable acid content, and vitamin C content of cherry tomatoes during storage. Compared to control, ultrasound combined with calcium impregnation treatment had no obvious influence on the all-trans lycopene contents. According to results from NMR, ultrasound combined with calcium impregnation treatment inhibited the oxidation of all-trans lycopene, 5-cis-lycopene and 9-cis-lycopene during storage and maintained theirs structural integrity. Ultrasound combined with calcium impregnation technology could effectively maintain the quality of cherry tomatoes. The results provided a theoretical basis for the application of ultrasound combined with calcium impregnation technology in fruit and vegetable preservation.

Abstract:Pomegranate peel is an easily available and inexpensive industrial by-product which is rich in polyphenols. In this study, ultrasound-assisted extraction method was used to extract polyphenols from pomegranate peel. The technological parameters were optimized and the composition and content of polyphenols from pomegranate peel were determined by high-performance liquid chromatography (HPLC). The changes of pomegranate peel surface after ultrasonic treatment were also studied. The results showed that with ultrasonic assistant conditions, water as a solvent, had a higher yield of polyphenols, which was better than other organic solvents such as methanol. Therefore, water was used as a solvent for subsequent research. In the optimal conditions of liquid-solid ratio (mL∶g) 60∶1, ultrasonic power 400W and ultrasonic time 25min, the optimal yield of polyphenols was 39.30mg/g (using gallic acid as the standard), which was higher than that of conventional solvent extraction method (32.58mg/g). HPLC analysis showed that the content of punicalagin in pomegranate peel polyphenols was highest, followed by punicalin. Ultrasonic treatment could greatly enhance the extraction effect. The microscopic observation on the surface of pomegranate peel showed that ultrasound could significantly destroy the surface of pomegranate peel and affect the integrity of plant tissue, thus releasing more polyphenols.

Abstract:The new gene aurT (GenBank accession number:MH247109.1) in the Aureofuscin biosynthetic gene cluster was obtained by molecular cloning technology. And the function and regulatory mechanism of aurT gene on the Aureofuscin biosynthesis were analyzed by high-efficiency expression, gene knockout, high-performance liquid chromatography (HPLC) and bioinformatics technology in order to enhance the fermentation yield of Aureofuscin. The results showed that AurT belonged to the RhtB family regulator and was an amino acid transporter for Aureofuscin biosynthesis. Compared to original strain, the Aureofuscin production in the aurT gene highly expressing strain (♂aurT) was 1.3 times increased, which was reduced by 65% in the aurT gene knockout strain (ΔaurT), but the Aureofuscin production was not completely inhibited. It indicated that the regulation process of aurT on biosynthesis was different from the pathway-specific regulation gene aurJ3M. Four different structural analogues of PI factors (1,2- propylene glycol, glycerin, ethylene glycol, triethanolamine) were compared, and addition 0.4mL glycerin had the best effect on regulating the Aureofuscin biosynthesis. The yield of Aureofuscin produced by ΔaurT strain was 784μg/mL with exogenous addition of glycerin for 96h, which was only 244μg/mL without addition of glycerin. Further study using RT-PCR experiments verified that the addition of glycerol to the wild-type strain increased the transcription level and expression of aurT gene. It indicated that structural analogues of PI factors might bind to specific receptors in the gene cluster and initiate the expression of related genes. Aureofuscin biosynthesis was regulated by aurT gene via mediating the extracellular transport of PI factors.

Abstract:In order to study the antibacterial properties of antibacterial peptide Brevilaterin secreted by Brevibacillus laterosporus, effect of different external factors of food on its antibacterial activity were investigated, and its MIC and MBC values in varied internal environment of food were further checked. The results showed that Brevilaterin exhibited good stability towards those selected metal ions, emulsifiers (except soybean phospholipid), thickeners, enzymes, high concentration of sugar and repeated treatment of freeze-thaw. Furthermore, MIC and MBC values of Brevilaterin against S. aureus, L. monocytogenes, M. luteus, P. aeruginosa, L. lactis and H. alkalicola could be significantly changed with variation of the temperature, pH and osmotic pressure of food. Compared with the effect at the optimal temperature (37℃) of those foodborne pathogens mentioned above, the MIC and MBC values of Brevilaterin on M. luteus decreased to 1/8 at 4℃, the MIC and MBC values of Brevilaterin on P. aeruginosa, L. monocytogenes and S. aureus were decreased to 1/4~1/2 at 10℃. Compared with the effect when strains were grown at the optimum pH (6~7), the MIC and MBC of Brevilaterin on L. lactis were reduced to 1/2 at pH 2, and the MIC and MBC of Brevilaterin on S. aureus were reduced to 1/2 at pH 8~9. Similarly, the MIC and MBC of Brevilaterin for H. kalicola at pH 7 were reduced to 1/4 of that at pH 11 (optimal pH). The MIC and MBC of Brevilaterin for S.aureus under hypertonic condition were reduced to 1/2 of that under normal pressure. Therefore, when the growth conditions of foodborne pathogens deviated from their optimal conditions, Brevilaterin showed stronger antibacterial effects, while both of MIC and MBC values were reduced to 1/8~1/2 of that at optimal conditions. All of these properties exhibited by Brevilaterin indicated its scientific guideline on the food application in the future.

Abstract:Using functional microorganisms to control contamination is an effective way to control the biogenic amine content in Huangjiu production. Pontibacter beigongshangensis was a new microbial species isolated from Huangjiu koji, which could induce the production of bacteriocin by Pediococcus pentosaceus. Bacteriocins had inhibitory effects on Staphylococcus saprophyticus, Cronobacter sakazakii, Brevibacterium casei, Bacillus, and Enterobacter cloacae, which produce biogenic amines in Huangjiu. Meanwhile, Pontibacter beigongshangensis and Pediococcus pentosaceus do not produce biogenic amines. During Huangjiu fermentation, the natural enhanced Qu created by adding Pontibacter beigongshangensis and Pediococcus pentosaceus, could reduce the biogenic amines content by 29.8% in Huangjiu, but had little effect on the flavor quality of Huangjiu. Therefore, Pontibacter beigongshangensis and Pediococcus pentosaceus can be used as functional species for reducing biogenic amines in Huangjiu brewing.

Abstract:Based on the preliminary results of the untargeted metabonomics in Monascus purpureus, differential metabolites such as arginine, L-malic acid, D-glucose, niacinamide, α-oxoglutaric acid, phenylalanine, lysine, thiamine pyrophosphate,flavin mononucleotide and L-lactic acid were added to the original nutrients, respectively. The yields of Monascus pigment and Monacolin K at 8th and 15th day were detected. The results showed that the addition of arginine, phenylalanine, lysine and flavin mononucleotide promoted the production of Monacolin K. It was speculated that the addition of amino acids could promote the yield of Monacolin K. Among them, the Monacolin K yield after arginine addition was 2.2 to 3.7 times of the control group. The production of Monacolin K was changed with the different addition of niacinamide. The lower level of niacinamide had a promoting effect, while higher level showed an inhibitory effect. Lysine, phenylalanine and flavin mononucleotide had a better effect on the enhancement of Monascus pigment, and flavin mononucleotide increased the yield to 1.5-3.0 times of the control group.

Abstract:Aloididae aloidi was used as raw materials to study the contents of free amino acids, nucleotides and organic acids, and the changes of volatile flavor substances, protein structure and the exogenous enzyme activity of Aloididae aloidi hydrolysates with ultra-high pressure treatment. The results showed that the ultra-high pressure treatment could activate both the flavor protease and compound flavor protease, and the former was activated more strongly. Compared with the normal pressure treatment, ultra-high pressure treatment led to higher contents of free amino acids, succinic acid and monosodium glutamate equivalents in Aloididae aloidi hydrolysates. In addition, ultra-high pressure treatment gave enzymatic hydrolysates better umami and overall flavor, more main volatile substances, and less unpleasant flavor substances, which changed the composition of volatile substances to achieve flavor-enhanced effect. Ultra-high pressure destroyed the protein structure, which could promote the release of flavor amino acids, improve the flavor of the enzymatic hydrolysates, and increase the protein utilization rate. Ultra-high pressure treatment could improve the proteolytic degree and promote the release of flavor amino acid, nucleotides and organic acids by improving the protease activity, especially flavor protease activity, and destroying the protein structure.

Abstract:Cellulose was extracted from kelp and wakame, which were two major edible brown seaweeds in China, and the structural features were analyzed and compared. The kelp had significantly higher cellulose content than that of the wakame, and the cellulose extraction yields were 5.59% and 2.61% of the dry seaweeds. The purity of the cellulose samples reached 99.86% and 98.91% according to the acid hydrolysis-HPLC analysis and FT-IR analysis. The kelp cellulose had a degree of polymerization of 813, which was significantly higher than that of the wakame of 315. X-ray powder diffraction analysis revealed that two kinds of brown seaweed cellulose both had natively highly crystalline structure, with the crystallinity indexes reaching 72.06% and 71.48%, which were comparable to that of the commercial microcrystalline cellulose derived from advanced plant. Further analysis of the X-ray diffractograms suggested that the crystalline region of the brown seaweed cellulose featured Iα (one-chain triclinic) phase-rich structure, evidently different from Iβ (two-chain monoclinic) phase-rich structure of cellulose from advanced plant. This study provides a reference for resource development of high quality dietary fiber.

Abstract:To study the chemical constituents in ethanol extract of Cornus officinalis and their neuroprotective activity. The chemical constituents exerted neuroprotective effect were isolated and purified by normal phase silica gel column chromatography, Sephadex LH-20 gel column chromatography, macroporous resin, normal and reverse phase, cyanide silica gel LPLC (low pressure liquid chromatograph), and reverse phase HPLC, etc. Their structures were identified based on nuclear magnetic resonance spectrum, mass spectrum and published data, and their neuroprotective acitivity were evaluated by H₂O₂ induced SH-SY5Y damage cell model. The results showed that nine compounds were isolated from Cornus officinalis and identified as 7-β-morroniside (1), 7-β-O-methylmorroniside (2), 7-α-O-methylmorroniside (3), kingiside (4), cornolactones D (5), pollenfuran A (6), threo-2,3-bis (4-hydroxy-3-methoxyphenyl)-3-ethoxypropan-1-ol (7), 5-hydroxymethyl furfural (8) and 3,4-dihydroxybenzoic acid (9). Among them, pollenfuran A (6) and threo-2,3-bis (4-hydroxy-3-methoxyphenyl)-3-ethoxypropan-1-ol (7) were isolated from Cornus for the first time, and cornolactones D (5) was identified from Cornus officinalis for the first time. Compounds 7-β-morroniside (1), 7-β-O-methylmorroniside (2), and 7-α-O-methylmorroniside (3) exhibited neuroprotective effect.

Abstract:Lactic acid bacteria (LAB) is widely used in food and food fermentation industries. Among them, acid whey tofu with LAB as coagulant has gradually obtained more and more attention. LAB is the dominant bacteria in the fermentation process of acid whey tofu, which was inevitable above 75℃ during the pasting process of acid whey tofu. Ordinary LAB cannot tolerate this temperature, and a large number of inactivation at this temperature will affect the ripening of the product. In order to develop high temperature resistant LAB, four strains of high temperature resistant and acid producing bacteria were screened by ultraviolation mutagenesis with the strains isolated from Jianshui acid tofu whey in Yunnan province. The results showed that the four strains could resist high temperature at 75℃ for 30min, and maintained a good activity and acid-producing ability. Compared with the original strain, the mutant strains obtained in this study had better temperature resistance and acid-producing ability. Among them, HCUL 1.1801-1912Z had the best activity and acid-producing ability and it will significantly improve the quality of acid whey tofu. The activity of the LAB in the tofu and tofu quality can be obviously improved.

Abstract:Starch is the main component of Qingke barley, its digestion rate and degree directly affects the postprandial blood glucose response. Therefore, in vitro starch digestibility of Qingke barley and it's products were investigated in this study. Meanwhile, 12 healthy volunteers were recruited to measure the glycemic index (GI) of 4 kinds of Qingke barley products according to international standard methods. The results showed that the starch digestibility rate of the cooked Qingke barley flour was significantly lower than that of cooked wheat flour. Cooking and extrusion significantly increased rapidly digestible starch (RDS) and decreased resistant starch in both Qingke barley and wheat. GI values of Qingke barley steamed bread, Qingke barley fresh noodles, Qingke barley noodles and Qingke barley fried noodles were 70±11,60±13,51±11, and 33±14, respectively. The results of correlation analysis showed that GI value was significantly positively correlated with RDS(R=0.733, P=0.007). In vitro and in vivo tests both suggested that different processing techniques could affect the digestive characteristics of Qingke barley products. It is necessary for consumers to select appropriate products according to their own health status. Qingke barley noodles and Qingke barley fried noodles were classified as low GI food, which were conducive to the glycemic control crowd or diabetic patients to eat.

Abstract:In order to improve the economic value of camellia meal and make full use of the camellia meal resources, tea saponin was extracted from camellia meal by continuous multi-stage countercurrent extraction process using hot water, and the parameters of single-stage extraction and continuous multi-stage countercurrent extraction process were optimized. The results showed that the best conditions for single-stage extraction were as follow:extraction time 85 min, extraction temperature 80℃, material-liquid ratio 1∶16g/mL, and the most suitable extraction size of camellia meal 60-100mesh. On the basis of single-stage extraction, the optimal number of extraction stages for continuous multi-stage countercurrent extraction was determined to be 3 stages, and the optimum extraction time for each stage was 20min. Under those conditions,the content of tea saponin in the extract was 33.14mg/mL, which was 123% higher than that of single-stage extraction. Extraction time was shortened 29.41% and extraction efficiency was improved at the same time. In this study, an aqueous solution combined with continuous multi-stage countercurrent extraction was used to obtain tea saponin with a higher mass concentration, and the extraction time was shortened. The extraction process was green and environmentally friendly, and industrial production was easier to achieve.

Abstract:Based on the traditional process, the Zanthoxylum schinifolium sauce sterilized with ultra-high pressure was developed using Zanthoxylum schinifolium as the main raw material supplementing green pepper, garlic and other raw materials. The color protection method of Zanthoxylum schinifolium was optimized and the shelf-life was predicted. The addition of color protection agent was optimized by response surface analysis. The optimized method was soaked Zanthoxylum schinifolium with 0.89g/L ascorbic acid, 0.1g/L zinc sulfate and 2.62g/L citric acid. Using electronic nose to determine the flavor type of Zanthoxylum schinifolium sauce, the results showed that the flavor components in the sauce were mainly composed of inorganic sulfides, terpenoids and nitrogen oxide. The Q10 shelf life prediction model was used to predict the shelf life of the sauce. Based on comprehensive sensory evaluation, color difference, moisture change and the total number of colonies changed under different storage conditions, the shelf-life was 25d at 35℃ and 13d at 45℃. Then the shelf-life model was used to predict the shelf-life of the sauce at 4℃ and 25℃. The results showed that the shelf-life of the sauce at 4℃ was 189d and 48d at 25℃.