Abstract:Sterilization of solid food has always been a key technical problem in food industry. In order to ensure an energy-saving, efficient, and safe sterilization process, in recent years, a series of emerging physical sterilization technologies have emerged in reference to two physical phenomena from the space extreme environment, electromagnetic wave and plasma. These include thermal physical sterilization technologies represented by catalytic infrared radiation, microwave, radio frequency, and non-thermal physical sterilization technologies represented by photodynamic, pulsed light, cold plasma activated water/ice, and in-package cold plasma. These emerging technologies could adapt to the surface or overall sterilization of solid foods with different forms and component characteristics. This article focused on the core issues and latest application research of relevant technologies, and proposed the main tasks for future development of physical sterilization of solid foods from four aspects. 1) Deepen the mechanism research of physical sterilization technology. Based on different solid food matrix environments, explore the response mechanisms of different food-borne microorganisms under different physical field stress. 2) Promote the key technology research of multi-physical field coupling sterilization. According to the characteristics of different solid food materials, coordinate various emerging physical sterilization technologies with their respective characteristics to establish a balance between sterilization effectiveness and food quality reduction. 3) Break through the manufacturing bottleneck of physical sterilization key equipment. Based on interdisciplinary research, overcome the technical difficulties in development of key equipment for physical sterilization, and minimize manufacturing cost. 4) Promote the development and application of in-package physical sterilization technology. According to the real production scenarios of solid food, promote the development of in-package physical sterilization technology to avoid secondary pollution after sterilization.

Abstract:Patulin, a polyketide secondary metabolite produced by fungi, is a major mycotoxin in fruits and their processed products. Penicillium expansum is the primary agent for patulin contamination in food. P. expansum infects most bulk and special fruits, causes serious postharvest decay, and simultaneously produce patulin. The circulation and processing of fresh fruits can introduce patulin into the food chain, which pose a potential threat to the health of consumers. Patulin may damage vital organs in both humans and animals and causes acute and chronic symptoms. The food safety issues caused by patulin contamination are attracting increasing attention, and patulin-related research has become a hot topic. The research advances in patulin biosynthesis and regulation mechanisms were comprehensively summarized. The gene cluster of patulin biosynthesis, catalytic enzymes in different steps of the biosynthetic pathway, and the molecular pathway of patulin biosynthesis and intermediate product transport were introduced. The complex regulatory network of patulin biosynthesis from the aspects of specific regulatory factor of biosynthetic pathway, global regulatory factors responding to environmental signals such as light, pH value, carbon source, and sulfur source, as well as epigenetic factors involved in histone methylation and acetylation modifications were described. The source control and removal strategies for patulin contamination in food were elaborated. The main control technologies based on physical, chemical, and biological principles were summarized, respectively, and the advantages and disadvantages of different control strategies were raised. Finally, the relationship between the research of patulin biosynthetic mechanisms and the development of contamination control technologies was discussed. The green and safe biological control methods as the promising technology was emphasized.

Abstract:Ochratoxin A (OTA) is a toxic secondary metabolite mainly produced by fungi from the genera Aspergillus and Penicillium, and it has nephrotoxicity, hepatotoxicity, teratogenicity, neurotoxicity, potential carcinogenicity, and is one of the mycotoxins of great concern worldwide. However, the classification of OTA-producing fungi, OTA biosynthetic pathway and regulatory mechanism are still controversial, which restricts the efficient and accurate control of OTA contamination in food. Therefore, the main OTA-producing fungi in Aspergillus and Penicillium were systematically sorted out and classified. In particular, some strains of A. ochraceus once considered as the main toxigenic fungi were re-identified as A. westerdijkiae based on genomic comparison data, and the toxigenic ability of the main OTA-producing fungi was introduced. The OTA biosynthetic gene clusters, key biosynthetic and regulatory genes were systematically sorted out and introduced, especially the new gene, the cyclase otaY gene, which may be involved in catalyzing the polyketide cyclizing reaction in the initial step of OTA biosynthesis. Based on the latest research results, the OTA biosynthetic pathway was further improved. According to the different stages of food production, the biological, physical and chemical control and detoxification strategies of OTA-producing fungi were sorted out. The biocontrol methods against OTA-producing fungi, and the biodegradation bacteria and detoxification enzymes for OTA were introduced, and the advantages and disadvantages of different methods were compared and discussed. Finally, it was proposed that the control of OTA contamination in food should be based on the idea of “whole chain control” and “source prevention and control” to ensure food safety and people's life and health. The advantages and disadvantages of biological control and biological detoxification technology were discussed. It was pointed out that a green and safe biological control strategy had broad application prospects and was the key direction of future research.

Abstract:Binding of polyphenols to proteins could affect protein gel properties and thus the texture of food. Hazelnut protein isolate (HPI) was taken as raw material, three polyphenols (TP), including tea polyphenols, epigallocatechin gallate (EGCG) and gallic acid (GA), were combined with HPI. The effects of three polyphenols on the structural properties, gel characteristics, gel structural properties, protein digestibility and the antioxidant properties of digestion products were investigated. The results showed that all the three polyphenols could promote HPI structure unfolding and combine with HPI through hydrophobic interaction and hydrogen bond. With the addition of TP, EGCG and GA, the gel strength of HPI gels were increased by 47.77%, 59.87% and 10.76% (P<0.05), respectively, and the water holding capacity of HPI gels were increased by 37.20%, 39.74% and 28.17% (P<0.05), respectively. Compared with HPI gel, HPI-TP gel and HPI-GA gel, scanning electron microscopy showed that the microstructure of HPI-EGCG gel was denser, and gel rheological properties showed higher storage modulus of HPI-EGCG gel, and Fourier transform infrared spectroscopy showed that the HPI-EGCG gel had stronger hydrogen bonding, higher β-folding content, and better gel strength and water retention. The results of gel intermolecular force showed that hydrogen bond and disulfide bond were the main forces maintaining HPI-TP gel and HPI-EGCG gel. Hydrophobic interaction and disulfide bond were the main forces maintaining HPI-GA gel. Compared with HPI gel, HPI-TP gel and HPI-GA gel, HPI-EGCG gel had lower content of free sulfhydryl groups, higher content of disulfide bonds and more stable gel structures. After in vitro digestion, TP and EGCG decreased HPI gel protein digestibility, and GA increased HPI gel protein digestibility (P<0.05). Among the four gels, the digestion products of HPI-EGCG gel had stronger antioxidant properties (P<0.05). Polyphenols could effectively improve the gel properties of HPI and retain its antioxidant properties, with HPI-EGCG gels having the best gel properties and antioxidant properties of digestion products. It was hoped that the results of the study would provide a theoretical basis for the development and utilization of new hazelnut isolate protein gel products.

Abstract:Antheraea pernyi (A.pernyi) pupa is rich in high quality protein, which is a kind of food raw material with high development and utilization value. The effects of different pH values on the gel properties of A. pernyi pupae flour and the thermal aggregation of protein molecules were studied by texture analyzer, rheometer and confocal laser scanning microscope. The results showed that the gel network formed at pH 7 was relatively continuous and uniform, and the water retention of gel was the highest (51.67%±0.79%, P<0.05). At pH 9, A. pernyi pupae flour had the least critical gel mass fraction (8%), the highest gel hardness (41.67N±3.37N, P<0.05) and elasticity (2.81mm±0.07mm, P<0.05). In addition, the storage modulus of A. pernyi pupae flour gel was significantly positively correlated with the solubility (R=0.92) of proteins (P<0.05), but negatively correlated with the proteins coagulate rate (R=-0.52) and surface hydrophobicity (R=-0.77) (P<0.05). At pH 9, the protein solubility was the highest (62.13%±0.63%, P<0.05), and the surface hydrophobicity was the lowest (70.06μg±9.32μg, P<0.05). More small-size thermal aggregates were formed and the gel matrix was enhanced at pH 9. At pH 5, the protein solubility was the lowest (28.96%±1.13%, P<0.05), and the surface hydrophobicity was the highest (195.66μg±1.30μg, P<0.05), which promoted the formation of more large-size thermal aggregates and disorderly stacking, weakening the gel matrix. The purpose of this study was to control the thermal aggregation behavior of protein in A. pernyi pupae flour by adjusting the pH value, and then the gel with ideal texture and water retention could be obtained.

Abstract:To study the effects of sweet potato protein hydrolysates (SPPHs) on the gel structural properties of sodium alginate (SA) and to achieve the high quality utilization of sweet potato processing residues, SPPHs with different molecular weights (1000,2000,3000,8000Da) were added to SA to investigate their effects on the formation process and gel properties of SA gels induced by calcium ions in terms of gelation process, critical gel behavior, textural properties, water distribution and microstructure. The results showed that the interaction between SPPHs and SA promoted its cross-linking with calcium ions, which could strengthen the intermolecular structure, accelerate the appearance of critical gel point in the process of calcium cross-linking and reduce the amount of calcium ions required for the critical point. Among them, SPPHs with molecular weight of 8000Da had a more significant strengthening effect on SA gel, and the reaction sensitivity with calcium ions was the strongest, resulting in the formation of the largest gel strength. The average value of the storage modulus G′ value of SA-SPPHs8000 during the gelation process with 0.100% CaCl₂ was 17.05kPa. It was much higher than that of blank group SA (2.14kPa). The composite gel with the addition of SPPHs behaved as a typical non-Newtonian fluid, and the larger the molecular weight of the added SPPHs, the stronger the internal structural cross-linking of the formed composite gel, the stronger the pseudo plasticity, and the greater the viscosity. In addition, the addition of SPPHs significantly improved the hardness, elasticity and chewiness of SA gel beads, and improved the water holding capacity and internal structural stability of the gel beads. The results showed that the addition of SPPHs could strengthen the internal structure of SA gels and promote calcium cross-linking to form more compact three-dimensional network gels, which in turn improved the texture and other properties of SA gels. Compared with other protein hydrolysates, SPPHs had greater advantages. Meanwhile, this study could broaden the application scope of sweet potato protein, improve its added value and further realize the comprehensive utilization of sweet patato protein resources.

Abstract:Controlling release of flavor components during brining process can potentially benefit to regulate the industrial standardization degree of brined product qualities. The heat-induced emulsion gels were fabricated after two-phase homogenization of water and oil by using egg white protein and curdlan as matrix material and cinnamon oil as the typical flavor component. The effects of cinnamon oil addition on gel properties and release behaviors of cinnamaldehyde were investigated. The results showed that the emulsion gels containing cinnamon oil became yellowish, the microstructures were denser, and the parameters of water holding capacity, hardness, storage and loss moduli were significantly improved compared with the emulsion gel containing soybean oil. Besides, when the mass fraction of cinnamon oil was 5%, the emulsion gel had the best gel properties. With the increase of cinnamon oil additions, the gel transition time of emulsion gels shortened, while their viscoelasticity decreased, with higher brightness and lower yellowness values. The Schiff base reaction occurred between cinnamaldehyde in cinnamon oil and egg white protein confirmed by infrared spectra, which thus promoted the formation and gel properties of emulsion gels. The release of cinnamaldehyde could be well controlled by the emulsion gels under simulated brined product processing environments. The release rate of cinnamaldehyde in aqueous phase reduced as cinnamon oil additions increased, and when the mass fraction of cinnamon oil was increased from 5% to 11%, cumulative release rate decreased by 35.44% after the emulsion gels cooked in water for 1hour. Compared with cooking in water, the seasonings of sodium chloride, acetic acid, and ethanol promoted the release of cinnamaldehyde in the aqueous phase, and the cumulative release rate increased the most in acetic acid (15.95%). However, protein and polysaccharide in the simulated brine matrix inhibited cinnamaldehyde release, and the cumulative release rate decreased by more than 9.58%. During the simulated brine products processing, the original bulk morphology of emulsion gels kept intact. However, under the acidic condition, the texture of emulsion gels became stiffer after cooking, and meanwhile their volume decreased, their cooking loss rate was the highest, and their gel structure damaged the most severe. These factors promoted the release of cinnamaldehyde. Therefore, the textural and release properties of egg white protein/curdlan emulsion gels could be regulated by the addition of cinnamon oil as the active filler. The findings would potentially provide a technical reference for the development of flavor control release strategies in food industry.

Abstract:To study the immune and anti-inflammatory activities of Lateolabrax maculatus immunomodulatory peptides (LIP), the preparation conditions of LIP were optimized by single factor experiments and response surface methodology with the stimulation index of mouse spleen lymphocytes as an indicator. RAW264.7 macrophage model was used to study the immunomodulatory effect of LIP, and anti-inflammatory activity of LIP was explored by constructing a lipopolysaccharide-induced RAW264.7 macrophage inflammatory model. The results showed that the optimal preparation conditions for LIP were as following:solid-liquid ratio 1.0∶3.8 (g/mL), enzyme adding amount 2.14%, papain hydrolysis time 56min. Under this condition, the stimulation index of mouse spleen lymphocytes reached 2.57. The results of macrophage immunoactivity show that LIP exerted immunomodulatory activity. 400μg/mL LIP exerted immunomodulatory effects by promoting the proliferation and phagocytosis capacity, nitric oxide and reactive oxygen species production, nitric oxide synthase (iNOS) mRNA expression, and proinflammatory cytokines secretion. Moreover, 400g/mL LIP also showed effectively anti-inflammatory capacity by downregulating prostaglandin E₂ and proinflammatory cytokines, and reducing excessive secretion of NO via inhibiting overexpression of iNOS and cyclooxygenase-2 mRNA. These results suggested that LIP exerted bidirectional immunomodulatory activity,including “increasing immune response” and “inhibiting excessive immune response”, which provided a theoretical basis for bidirectional immunomodulatory functional foods research.

Abstract:Lactobacillus paracasei ET-22 is a kind of probiotic that can relieve intestinal inflammation and regulate immune functions, but the effects on oral diseases and its mechanism need to be further studied. In this study, an oral ulcer model based on golden hamster was established by buccal injection of methyl viologen, and the effects of ET-22 on the phenotype of oral ulcer and the inflammatory factors expression level were studied through previously treating hamsters with 1×10⁹CFU/mL/day of live ET-22, inactivated ET-22 and fermented broth of ET-22. The results based on histopathological section observation and score of oral mucosa showed that the intervention of live ET-22, inactivated ET-22 and its fermented broth could improve the epithelial integrity and inflammatory cell infiltration of oral mucosa in oral ulcer model hamsters. And the live ET-22 had the best performance on prevention of oral ulcer, followed by inactivated ET-22 and fermented broth of ET-22, but their effects were all better than the effect of vitamin C intervention. On the one hand, ET-22 could inhibit the secretion of pro-inflammatory cytokines IL-6 and IL-1β by down-regulating the expression of NF-κB, thereby reduced the expression of matrix metalloproteinase MMP-9 and alleviated the inflammatory infiltration and metastasis of oral mucosa. On the other hand, ET-22 could regulate oral microbiota composition and inhibit harmful bacteria related to oral diseases. The study indicated that ET-22 could decrease the risk of oral ulcer and play a positive role in the prevention of oral ulcer.

Abstract:The decarboxylations of the intermediates involved in the industrial production of furanone starting from diethyl α-methyldiglycolate and diethyl oxalate were investigated. Furanone was obtained through two successive Claisen condensations, hydrolysis of esters, methylation, and decarboxylation in this process route. During the reaction, both two ester groups of diethyl α-methyldiglycolate were removed during the process, but the approaches of two decarboxylations were obviously different. After the Claisen ester condensation, the first ester group was removed in the form of a carbonate by an addition-elimination mechanism in the presence of CH₃ONa. The second ester group was removed in the form of CO₂ through a sodium carboxylate intermediate under basic conditions following the methylation. In order to verify the generality of decarboxylation of the intermediate, the decarboxylation of β-carbonyl ester occurred without hydrolysis under basic conditions. The alkylation of α-ethyl acetoacetate was carried out to observe whether the product (α-ethyl-α-butyl acetoacetate) would undergo decarboxylation. However, the expected decarboxylation product of α-ethyl-α-butyl acetoacetate (3-ethyl-2-heptanone) was not observed. Therefore, the results indicated that common β-carbonyl esters could not undergo decarboxylation attacked by a base through an addition-elimination mechanism. The driving force for the two abnormal decarboxylation in the preparation of flavor furanone was due to the formation of stable aromatic conjugated structures after decarboxylation. This research had clarified the reaction mechanism of the preparation process of the flavor furanone, which would be helpful for the improvement and optimization of the technical route.

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.

Abstract:As one of the key hydrolytic enzymes for starch digestion, the hydrolysis of α-amylase enables starch to digest quickly, leading to a rapid increase of postprandial blood glucose levels. Persistent postprandial blood glucose increase is positively correlated with occurrence of metabolic diseases such as diabetes, hyperglycemia and hyperlipidemia, and etc.. Using natural compounds to inhibit the activity of α-amylase is of great significance in reducing the incidence of these metabolic diseases. Chlorogenic acid and α-amylase taken as the research object, the in vitro simulated digestion experiment was carried out. When the substrate concentration was 10mg/mL, the activity of α-amylase was 2U/mL. When the hydrolysis time was 20min, the inhibition rate was 67.3%, and the IC₅₀ was 4.2mg/mL, which confirmed that chlorogenic acid inhibited the activity of α-amylase. Based on enzyme reaction kinetics, the results of Lineweaver-Burk double reciprocal mapping analysis showed that the inhibition type of the enzyme was mixed inhibition. Molecular docking technique was used to reveal the intermolecular interaction between chlorogenic acid and α-amylase. It was predicted that the inhibition mechanism of chlorogenic acid on α-amylase was a mixed inhibition, which was consistent with the results of enzyme reaction kinetics. Molecular docking simulation results showed that chlorogenic acid could not only form hydrogen bonds with Glu261, Asp328 and Tyr193 at the catalytic active site of α-amylase to achieve competitive inhibition with starch, but also form hydrogen bonds with His327 and Ala232 amino acid residues of α-amylase to achieve non-competitive inhibition combined with amylase-substrate complex. Based on the inhibitory effect of chlorogenic acid on α-amylase, chlorogenic acid could be used to inhibit the activity of α-amylase to reduce the digestibility of starch and delay the rapid increase of postprandial blood glucose caused by carbohydrates. It was hoped to provide a theoretical basis and useful reference for the application of chlorogenic acid in food suitable for type Ⅱ diabetes patients.

Abstract:The purpose of this study was to establish polysaccharide gums treatments for clarification and color improvement of restored fruit juice of Docynia delavayi Schneid.. The gum treatments effects on the basic characters (colority, turbidity, browning value, pH value, soluble solid content, and vitamin C content), total phenolic content, chlorogenic acid content, polyphenolic composition, in vitro antioxidant activity, and non-enzymatic browning kinetic parameters of the restored fruit juice were elucidated by spectrophotometry, HPLC, and UPLC-MS-MS. The results indicated that the addition of mass fraction 0.4% apple high-methoxy pectin (AHP), 0.1% tamarind seed polysaccharide (TSP), or 0.2% chitosan (CTS) endowed Docynia delavayi restored fruit juice of clear golden color. The clarifying effectiveness from high to low was in the order of CTS, TSP, AHP. Cold precipitation at 4℃ for 24 h combined with gum treatments resulted in an improved clarifying effect and reduced the initial non-enzymatic browning rate constant k₀ of the juice from 0.150d-1 to 0.071~0.078d-1 at 55℃. The changes in colority, turbidity, browning value, and k₀ were closely, linearly related to total phenolic content. Based on comprehensive considerations on clarity, inhibition against non-enzymatic browning (reducing k₀), DPPH radical scavenging ability and dietary fiber, it was proposed that mass fraction 0.1% TSP treatment gave relatively the best restored fruit juice among treatments in general. The polyphenolic compositions of the restored fruit juice were mainly chlorogenic acid, flavonoids (including quercetin-O-glucoside, kaempferol-O-glucoside and dixylosides, phloridzin, and chrysin), and isoflavonoids (including daidzin, pisumionoside). The compositions of chlorogenic acid and its derivatives, flavonoids, and isoflavonoids contents were lightly reduced by TSP treatment. Thermal treatments resulted in a great loss or removal of polyphenolic compositions, accompanying with an increase in hydroxyl chlorogenic acid derivatives content. The results showed that chlorogenic acid and hydroxyl chlorogenic acid derivatives were the key compositions for non-enzymatic browning reaction. These results were expected to provide a theoretical and technical support for clarifying treatments of restored Docynia delavayi fruit juice.

Abstract:The effects of dry heat treatment on physicochemical properties and nutrient digestion characteristics of rye bran were studied. Lipase activity, phytic acid content and free polyphenol content were used as inspection index under dry heat treatment conditions including 110℃-12min, 130℃-9min, and 150℃-6min. The results of physicochemical properties of rye bran showed that dry heat treatment could significantly (P<0.05) improve the water and oil holding capacity of rye bran. The overall peak type and position of the characteristic absorption peak of infrared spectrum did not changed significantly, but the intensity changed after dry heat treatment. Dry heat treatment could increase the content of free phenols, and reduce the content of total phenols and anthocyanins due to thermal degradation. After dry heat treatment, contents of polyphenols and flavonoids of rye bran increased in varying degrees during gastrointestinal digestion, and the antioxidant capacity increased gradually. The bioavailability of polyphenols at 110℃-12min, 130℃-9min and 150℃-6min groups were 73.26%, 70.74% and 74.44%, respectively, which were significantly higher than those in the untreated group (P<0.05). The bioavailability of flavonoids in 110℃-12min group was 43.17%, which was significantly higher than that in untreated group (P<0.05). Therefore, this study aimed to improve the nutritional quality of rye bran in industrial production by dry heat treatment, and promote the development and utilization of functional rye bran products.

Abstract:In order to clarify the effect of raw chayote tuber flour (RCTF) on processing properties of wheat flour, the basic composition different of RCTF and wheat flour were evaluated, and the effect of RCTF with different additive amount (mass fraction of 0,10%,20% and 30%) on basic physicochemical, pasting properties and rheological properties of wheat flour were subsequently investigated. Results showed that the total starch and crude ash contents of RCTF were higher than those of wheat flour, while contents of crude protein and fat, and average particle size of RCTF were much lower than those of wheat flour. X-ray diffraction pattern analysis showed there were obvious diffraction peaks at 2θ of 5.6°, 14.2°, 17.2°, 19.6°, 22.2° and 23.9°, indicating that the starch structure of RCTF belonged to B-type crystalline. The analysis results of basic processing characteristic indicated that RCTF addition significantly improved the water absorption, swelling degree and light transmittance of mixed flour, and reduced the water solubility index and freeze-thaw stability of mixed flour. The steady-state rheological properties revealed that RCTF addition increased the apparent viscosity, consistency coefficients (K) and flow behavior indexes (n) and yield stress (τ₀). The dynamic rheological properties determination revealed that RCTF addition improved storage modulus and loss modulus value, and lower loss tangent value. Pasting properties analysis showed that the addition of RCTF decreased the pasting temperature and peak time of wheat flour, and increased the peak viscosity, trough viscosity, final viscosity, breakdown and retrogradation value. These findings indicated that RCTF significantly changed the processing characteristics of wheat flour, which provided theoretical basis for the further processing and utilization of raw chayote tuber flour.