Peach fruit is susceptible to Monilinia fructicola during storage and logistics, leading to occurrence of brown rot and fruit quality deterioration. However, the regulatory effects of volatile organic compounds (VOCs) on brown rot remain unclear. This study analyzed the antifungal effects of major VOCs in ripe peach fruit on M. fructicola. The results showed that 12 VOCs involving carvacrol and (E)-2-hexenal were identified to have significant inhibitory effects on the growth of M. fructicola on media. Further research was conducted on the regulatory effects of 12 VOCs on postharvest brown rot of peach fruit. The results showed that the fumigation treatment with VOCs could effectively inhibit the growth of M. fructicola and delay the occurrence of brown rot. Among them, volatile aldehydes exhibited positive effects on maintaining fruit quality. Fumigation with 25 μL/L (E)-2-hexenal significantly inhibited the growth of M. fructicola and reduced brown rot symptoms in peach fruit. Meanwhile, the fruit appearance, ethylene release rate, hardness, total soluble solid content and sensory quality indicators were not affected, therefore maintaining the merchant ability of peach fruit during the postharvest storage. In summary, (E)-2-hexenal has the potential to be developed as a plant-based fungicide, offering quality assurance for the peach fruit supply chain.

Taking ten kinds of commercial dried hawthorn fruits [seven kinds of Crataegus pinnatifida Bge. or C. pinnatifida Bge. var. major N.E.Br. (with the trade name “Beishanzha”), two kinds of Malus doumeri (Bois) Chev. (with the trade name “Guangshanzha”) and one kind of C. cuneata Sieb. et Zucc. (with the trade name “Nanshanzha”)] from different producing areas of China as research materials, the contents of main nutrients and biochemical indexes were determined, and the quality difference analysis and principal component analysis were carried out. The results showed that among the three types of commercial dried hawthorn fruits, Beishanzha had the highest titratable acid content, while Guangshanzha had the highest ratio of soluble sugar to titratable acid. The contents of soluble dietary fiber, α-tocopherol and β-carotene decreased in the order of Beishanzha, Nanshanzha and Guangshanzha. The results of principal component analysis indicated that ‘Yeshanzha’ from Huanggang of Hubei Province and ‘Tieshanzha’ from Jizhou of Tianjin City showed the best overall performance in the contents of main active components (total phenolics, total flavonoids, total procyanidins and total dietary fiber); Beishanzha, especially ‘Dajinxing’ from Linyi of Shandong Province and ‘Yubeihong’ from Xinxiang of Henan Province, had greater contents of titratable acid, soluble dietary fiber and soluble sugar compared with Guangshanzha and Nanshanzha. This study systematically sorted out the quality differences of commercial dried hawthorn fruits from different areas in China, and the results can provide data to support the diversified development and utilization of Chinese commercial hawthorn resources.

In this study, the whole fruit of Citrus×aurantium L.Changshanhuyou was divided into five parts, namely, the flavedo, albedo, segment membrane, juice sacs and seeds, from which polyphenols and pectin polysaccharides were extracted sequentially. Ultra-high performance liquid chromatography-tandem mass spectrometry was used to determine 30 kinds of citrus polyphenols, and the compositions and molecular weights of pectin polysaccharides were compared to comprehensively analyze the compositions of the main functional components in different parts of Citrus×aurantium L.Changshanhuyou fruits. The results showed that flavonoids in various parts mainly existed in flavanones, and the contents of neohesperidin and neoeriocitrin in the albedo were the highest, reaching 13 700.72 μg/g and 6 270.24 μg/g (by dry mass and the same as below), respectively. The contents of cinnamic acids in various parts were higher than that of benzoic acids, and the contents of cinnamic acids in the flavedo were the highest. The yield of pectin polysaccharides extracted from albedo by amylase-assisted ethylenediamine tetraacetic acid solution was the highest (27.46%). The yield of pectin polysaccharides from the flavedo by the extraction of NaOH solution was the highest (11.30%), and the molecular weights (M_W) of pectin polysaccharides extracted by the two extraction methods in the flavedo were up to 6.888×10⁵ g/mol and 2.343×10⁵ g/mol, respectively. The flavedo, albedo and segment membrane of Citrus×aurantium L.Changshanhuyou can be used as the main processing sources of flavonoids and pectin, and their rich contents of neoeriocitrins provide new development direction for processing byproducts.

In this study, the effects of different methods on the extraction of protoilludane sesquiterpene aryl esters from Floccularia luteovirens were studied.Using the ultrasonic-assisted extraction method, the extraction process conditions were optimized by Box-Behnken response surface methodology based on a single-factor experiment. The in vitro antioxidant activity of protoilludane sesquiterpene aryl esters was determined, and the antibacterial activities against three common pathogenic bacteria were evaluated via the inhibition zone method. The results showed that ethyl acetate was the most suitable solvent for the extraction of protoilludane sesquiterpene aryl esters. The optimal extraction conditions for accessing protoilludane sesquiterpene aryl esters from F. luteovirens were as follows: solid-liquid ratio of 1∶33 (mass to volume), ultrasonic time of 33 min, and ultrasonic power of 166 W. Under these conditions, the extraction content of protoilludane sesquiterpene aryl esters was 10.107 μmol/g. In addition, the protoilludane sesquiterpene aryl esters had strong scavenging effects against 2, 2-diphenyl-1-picrylhydrazyl free radicals and hydroxyl free radicals, and had different antibacterial effects on Escherichia coli, Staphylococcus aureus, and Bacillus cereus. This study provides data support and a theoretical basis for the further development of F. luteovirens related products.

To explore the differences in flavor between flowers of ‘Zijuan’ and ‘Yingshuang’ tea varieties, the abundance of non-volatile metabolites in two light fermented tea flowers was tested, and the metabolites identified via widely targeted metabolomic technology based on ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The evaluation factors were evaluated by tea sensory evaluation methods and the contents of taste components, such as catechins and flavonoids, were detected by high performance liquid chromatography and colorimetric method. The results showed that ‘Zijuan’ tea flowers tasted sweet and fresh, and a little bitter and slightly astringent, while ‘Yingshuang’ tea flowers tasted sweet, slightly bitter and a little astringent. There were 219 kinds of significantly differential metabolites, including phenolic acids (56 kinds), flavonoids (46 kinds), lipids (26 kinds), tannins (19 kinds), amino acids and their derivatives (17 kinds) and others between the two varieties. Furthermore, metabolic pathway annotations revealed that amino acid-related metabolic pathways and flavone and flavonol metabolism pathways were the main differential metabolic pathways between ‘Zijuan’ and ‘Yingshuang’ tea flowers. In addition, the total contents of flavonoids and anthocyanins and the contents of catechins and some alkaloids between ‘Zijuan’ and ‘Yingshuang’ tea flowers were significantly different (P＜0.05), while the differences in the soluble sugar contents were not significant. The above results preliminarily showed that the flavonoids made the taste of tea flowers had a certain degree of bitterness and astringency, while compared with those in ‘Yingshuang’, the increase of contents of some amino acids and their derivatives in ‘Zijuan’ tea flowers was the main reason for its fresh taste.

In order to study the changes in muscle proteins of Larimichthys crocea during the seawater slurry ice-assisted preservation period, tandem mass tag (TMT)-based proteomics technology was used to quantitatively analyze the muscle proteins of fresh (stored for 0 d) L. crocea and the samples preserved by seawater slurry ice for different storage times (7 and 23 d). The differential proteins under different storage times were screened out, and they were analyzed by gene ontology (GO), clusters of orthologous groups/clusters of eukaryotic orthologous groups (COG/KOG), and Kyoto Encyclopedia of Genes and Genomes (KEGG). The results showed that the total number of differential proteins identified in the three comparison groups (7 d vs 0 d, 23 d vs 7 d, and 23 d vs 0 d) was 215, 133 and 269, respectively. The number of up-regulated differential proteins was 117, 37 and 113, respectively, and the number of down-regulated differential proteins was 98, 96 and 156, respectively. At the same time, a total of 44 common differential proteins were identified in the three comparison groups. GO analysis showed that the differential proteins were mainly involved in cellular process, biological regulation, cell and intracellular components, binding function, and catalytic activity. COG/KOG analysis showed that the functional activities of differential proteins were mainly concentrated in cytoskeleton, carbohydrate transport and metabolism, signal transduction mechanisms and posttranslational modification, protein turnover, and chaperones. KEGG analysis showed that 38 signaling pathways were involved and the number of differential proteins involved in the two signaling pathways of tight junction and pathogenic Escherichia coli infection was the highest at the late storage (23 d), which might be the main metabolic pathways causing the sharp decline in the freshness of L. crocea. The correlation analysis between 44 common differential proteins with the freshness indexes of L. crocea showed that five freshness indicator proteins were screened out, including fragile X mental retardation syndrome-related protein 2, inositol-1-monophosphatase, Rho GDP-dissociation inhibitor 1, ankyrin-1, and methyltetrahydrofolate synthase domain-containing protein. This study provides a basis for revealing the quality change mechanism, the freshness evaluation, and the preservation process improvement of L. crocea during the storage period with seawater slurry ice.

This study investigated the sensory traits and flavor chemical constituents and their contents of Zhejiang typical particle-shaped famous green teas including Juenong·Cuiming (from Shaoxing, Zhejiang, China), Pingshuirizhu (Shaoxing, Zhejiang, China), and Fenghuaquhao (Ningbo, Zhejiang, China). The differences in sensory characteristics and their key chemical contributors were analyzed. The results showed that there were obvious differences in appearance traits, including tightness, pekoe and color of different typical samples. The Juenong·Cuiming samples show fine and compact granules. The surface of Fenghuaquhao is covered with pekoe and its color is emerald green. For tea taste, Juenong·Cuiming has sweet and mellow taste, while the taste of Fenghuaquhao and Pingshuirizhu are mellow and thick. The gallic acid, catechin, epigallocatechin, epigallocatechin gallate, glutamic acid, arginine, methionine, theanine and γ-aminobutyric acid, etc. were identified as key differential compounds. For tea aroma, Fenghuaquhao is characterized by fresh aroma, while others have tender aroma and moderate toasty aroma. The volatile constituents with fresh and floral aroma such as dihydrolinalool, 1-octanol, and nerol, and volatiles with fruit and sweet aroma such as (E)-nerolidol, 1-nonanal, decanal, 3-nonen-2-one, and α-calacorene, and volatiles produced under high-temperature processing, such as β-ionone epoxide, dihydroactinidiolide, and tea pyrrole, were analyzed to be related with sensory aroma differences. In conclusion, there are obvious differences in appearance, taste, and aroma traits among particle-shaped green teas from different tea producing areas. The sensory differences of particle-shaped green teas were caused by diverse key chemical constituents and their contents, which were induced by tea cultivars, growing environment, and tea processing technology.

The existing traditional active preservation packaging has disadvantages such as low porosity and poor air permeability, so the fabrication of nano-scale packaging materials that can release slowly and retain freshness is a hot research topic in the field of storage and logistics of postharvest fruits and vegetables. In this study, polycaprolactone (PCL) nanofiber membranes loaded by thymol (THY) were prepared by the solution blow spinning technique, and the properties of THY/PCL nanofiber membranes were evaluated by material characterization and bacterial inhibition experiments. The results showed that the THY/PCL nanofiber membranes had lower crystallinity and increased thermal stability, while their water vapor permeable properties, surface hydrophobicity, and mechanical properties were not affected. In addition, the THY/PCL nanofiber membranes showed good antibacterial activity against Escherichia coli and Staphylococcus aureus, demonstrating a good application prospect in the field of postharvest preservation of fruits and vegetables.

Sulfated polysaccharide is an important nutritional component in shellfishes. In this study, a rapid microextraction and purification process for sulfated polysaccharides from marine shellfishes was established and applied to nine different shellfishes. Types of glycosaminoglycans (GAGs) from nine species of edible shellfishes were qualitatively analyzed by their basic chemical components, molecular weights and monosaccharide compositions. The results showed that the method could rapidly separate and purify polysaccharides. The purified polysaccharides were single components with molecular weights ranging from 24 to 55 kDa. Analysis of monosaccharide composition and infra-red spectra results showed that sulfated polysaccharides had GAGs-like properties. The polysaccharide samples from Buccinidae and Trichomya exhibited the characteristics of chondroitin sulfate (CS), which were represented by Buccinum pemphigum and Perna viridis. The polysaccharide samples from Argopecten irradians showed heparin (HP) characteristics. This study provides a micro- and rapid pretreatment technology for the structural analysis of sulfated polysaccharides from edible shellfishes.

In order to measure the tea lipid contents in different types of tea and to analyze the tea lipid compositions, twenty tea samples such as Xihulongjing, Jiuquhongmei, Baihaoyinzhen, etc., were used as materials to analyze the lipid contents through acid hydrolysis method and Soxhlet extraction method. The results showed that the tea lipid contents tested with Soxhlet extraction method were lower than the tea lipid contents tested with acid hydrolysis method. As for the tea lipid contents, they were changed due to tea materials and processing technologies. The tea lipid contents roughly showed as follows: green tea (non-fermented tea)＞yellow tea (lightly fermented tea)＞oolong tea (semi-fermented tea)＞black tea (completely fermented tea)＞white tea (lightly fermented tea)＞dark tea (post-fermented tea). Further study on the lipid content of white tea was analyzed, and it was found that the tea lipid content of Shoumei was higher than that of Baihaoyinzhen or Bai peony, and with the increase of storage years, the tea lipid content in white tea decreased; tea lipids were composed of phospholipids, lipoproteins and free fatty acids according to the qualitative analysis results. This study provides a theoretical and practical basis for the determination of tea lipids.

The objective of this study was to establish the optimum enzymolysis technology for Portunus trituberculatus seasoning based on the cooking liquor. Taking the flavor amino acid contents as evaluation indicators, a two-step enzymolysis technology with alcalase and flavorzyme was determined by response surface optimization methodology, and volatile flavor compounds in the secondary enzymolysis liquor were qualitatively and quantitatively analyzed by headspace-solid phase microextraction (HS-SPME) with gas chromatography-mass spectrometry (GC-MS). The results indicated that the optimum technological conditions of the primary enzymolysis were alcalase of 6 825 U/g, primary hydrolysis pH 8.45, hydrolysis time of 2.50 h, and the content of flavor amino acid in the hydrolysate was (7.18±0.09) mg/mL. The optimum technological conditions of the secondary enzymolysis were flavorzyme of 3 750 U/g, primary hydrolysis pH 6.81, hydrolysis time of 3.33 h, and the content of flavor amino acid in flavor precursors of P. trituberculatus seasoning was (10.49±0.12) mg/mL, which was 135.2% higher than that of P. trituberculatus cooking liquor. There were 62 volatile flavor compounds in the secondary hydrolysate; among them, hexanal, benzaldehyde and unsaturated alcohol were the main flavor components.The results provide a theoretical basis for the research of seasoning products of cooking liquor and high value utilization of P. trituberculatus.

The main anthocyanin components in white tea (Baihaoyinzhen, Baimudan, Gongmei and Shoumei) were preliminarily identified by high performance liquid chromatography-mass spectrometry, and then the composition characteristics and contents of anthocyanins were analyzed. The results showed that the main components of anthocyanins were delphinidin-3-O-galactoside, cyanidin-3-O-galactoside, pelargonidin-3-O-galactoside, cyanidin, delphinidin-3-O-[6-(Z)-p-coumarin] galactopyranoside, delphinidin-3-O-[6-(E)-p-coumarin] galactopyranoside, delphinidin-3-O-rutinoside, cyanidin-3-O-[6-(E)-p-coumarin] galactopyranoside and pelargonidin-3-O-rutinoside. The anthocyanin composition of Baihaoyinzhen, Baimudan, Gongmei and Shoumei was quite different. The anthocyanin contents of top grade and first grade of Baihaoyinzhen, top grade and first grade of Baimudan, first grade of Gongmei, and first grade and second grade of Shoumei were 83.80, 88.70, 90.59, 70.67, 122.75, 126.04 and 122.28 μg/g, respectively. The anthocyanin contents of Gongmei and Shoumei were significantly higher than those of Baihaoyinzhen and Baimudan. The above research results provide a scientific basis for the analysis of white tea anthocyanin components.

The main chemical compositions of Oolong tea infusions brewed in three different clay materials (red clay, purple clay and Duan clay) made boccaro teapots were investigated and compared. Aroma components in the tea infusion were determined using headspace liquid-phase microextraction (HS-LPME) and gas chromatography-mass spectrometry (GC-MS), and their differences were compared through visual pattern recognition based on principal component analysis (PCA). The sensory evaluation was used to score the aroma, tea taste and infusion color. The results showed that the flavoring compound contents and water extraction of infusion brewed in the boccaro teapots were higher than those in the control group (beaker). The contents of water extraction were red clay pot＞purple clay pot＞Duan clay pot＞control group. Fresh and sweet substances such as amino acids and soluble sugar’s contents were relatively higher in the red clay pot. Substances which taste heavy, strong and bitter, such as tea polyphenols and caffeine’s contents were higher in the purple clay pot. There were more kinds of aroma components in boccaro teapots, including nerolidol, indole, linalool and its oxide, β-ionone and some other components with pleasant flower flavors. The proportions of different aroma components were significantly different from each other. The results of PCA showed that the comprehensive scores from high to low were red clay pot＞purple clay pot＞Duan clay pot＞control group. The red clay pot group was the best in enriching the aroma components with flower and fresh flavors. The results of sensory evaluation showed that the boccaro teapots could affect the Oolong tea in aroma, taste and infusion color. The comprehensive scores of sensory evaluation were red clay pot＞purple clay pot＞Duan clay pot.

Using Tarocco blood oranges as experimental materials, the changes of anthocyanin, soluble sugar and organic acid contents and the expression characteristics involved in related metabolic genes during room temperature storage were analyzed by high performance liquid chromatography (HPLC) and quantitative real-time polymerase chain reaction. The results showed as follows: During room temperature storage, the anthocyanin content of blood oranges was increased by 222%. The mRNA levels of 4CL, CHI and ANS were significantly positive correlation with the anthocyanin content. The total sugar, sucrose, fructose and glucose contents of the fruits were significantly promoted by 12.0%, 7.7%, 19.7% and 12.7%, respectively. The mRNA level of SS1 was significantly positive correlation with the sucrose content, and the mRNA level of AI was extremely significant and negative correlation with the sucrose content. The accumulation of citric acid fluctuated significantly, and the mRNA level of IDH was extremely significant and negative correlation with the citric acid content. The 4CL, CHI, ANS, SS1, AI and IDH genes played important roles in the metabolism of anthocyanin, sugar and acid. Correlation analysis indicated that the anthocyanin content in blood oranges was significantly positive correlation with the contents of total sugar, sucrose, fructose, and glucose during room temperature storage, which had the highest correlation with the sucrose content. The above results show that the anthocyanin and soluble sugar contents of Tarocco blood oranges are promoted by short-term room temperature storage, and the changes of soluble sugar accumulation may regulate the anthocyanin synthesis.

This study focused on the effects of irradiation, artificial microbe treatment, temperature and humidity control on the aging and transformation of raw Pu’er tea, and explored the relationship between the factors such as microorganisms, irradiation and the quality of raw Pu’er tea. The results showed that the water content of tea samples during storage was between 7.0% and 9.0%, and the microbial changes of tea samples were not regular. Aqueous extract, free amino acid, tea polyphenol, catechin components showed a consistent change trend among different treatments. The contents of amino acids and tea polyphenols in the irradiated 9 kGy tea samples stored under the room temperature and 30 ℃ decreased more after 200 d, with the decline range of 40.37%, 38.82% and 37.65%, 36.73%, respectively, and the sensory quality was significantly lower than the aseptic treatments. The treatment A₂B₂C₁ namely irradiated 5 kGy sterile tea samples stored at 30 ℃ and 70% humidity had better sensory quality. The quality of tea samples treated with microbe after irradiation was improved with the extension of storage time and was superior to that treated without irradiation.But the sterile treatments under the same irradiation condition still had better overall flavor performance.The above results indicate that the microbial involvement has no direct effect on the quality of raw Pu’er tea under the storage conditions of this study.However, the irradiation treatment with its radiochemical oxidation has an obvious effect on the aging and transformation of raw Pu’er tea.

Rapid detection of Bacillus cereus in rice by loop-mediated isothermal amplification (LAMP) with microfluidic chip method was established. Based on the published B. cereus hblA gene sequence, primers were designed, and the fluorescent dye SYTO-9 was added to the reaction system, which allowed to be tested in real-time fluorescence reading performed by LAMP with microfluidic chip. The specificity was verified by 24 strains, and the sensitivity, limit of detection (LOD) and repeatability were tested by positive plasmid and positive strain of B. cereus, respectively. The results showed that two strains of B. cereus were positive and 22 strains of non-B. cereus were negative. The sensitivity for B. cereus was 170 CFU/mL for pure cultures in 35 min and 10 μL^－1 for positive plasmids in 15 min. The sensitivity of this method was 10 times higher than that of the traditional method. The LOD for B. cereus inartificially contaminated rice was 570 CFU/g, and could be completed in 45 min. The detecting repeatability of the positive plasmid from B. cereus was good and its coefficient of variation (CV ) was 2.02%. It is indicated that LAMP with microfluidic chip method has high specificity, sensitivity and accuracy. It could be used for rapid detection of B. cereus in rice.

Longjing tea is a famous traditional tea in China and the aroma is an important factor in the quality evaluation of tea. In this study, Longjing tea samples were widely collected and explored by sensory evaluation, which dividing them into three aroma groups: tender aroma type, clean and refreshing aroma type, and approaching high aroma type. Then, simultaneous distillation extraction (SDE) and gas chromatography-mass spectrometry (GC-MS) were used for extraction and determination of aroma compositions. The result suggested that the aroma-characteristic compositions of Longjing tea with tender aroma, clean and refreshing aroma, and approaching high aroma, respectively, showed differences in types and relative contents of alcohols, aldehydes, terpenes, ketones, alkanes, alkenes, heterocycles, esters and so on. The results of principal component analysis (PCA) based on main aroma components showed that: 1) The contents of styrene, cetane, 3-methoxy-1, 2-propanediol were significantly and positively correlated with the tender aroma of Longjing tea; 2) the contents of (E)-β-farnesene, trans-4-tert-butylcyclohexanol and methyl jasmonate were significantly and positively correlated with the clean and refreshing aroma of Longjing tea; 3) the relative contents of phenylacetonitrile, acetophenone, 1, 3-cyclohexadiene-2, 2, 6-trimethyl-benzaldehyde were higher in Longjing tea with approaching high aroma. This study provides a theoretical basis for aroma description in sensory evaluation of Longjing tea.

DNA min-barcoding methods based on cytochrome C oxidase subunitⅠ (COⅠ) sequence were developed to detect adulteration in 11 fresh meat products. DNA extraction was carried out with the DNeasy blood and tissue kit after samples were treated with vacuum freeze drying. The amplification of mini-barcoding region from DNA extracts was carried out using universal primer sets. Polymerase chain reaction (PCR) products were purified with DNA purification kit and analyzed by clone sequencing. The sequencing results were queried in GenBank (http://blast.ncbi.nlm.nih.gov/Blast.cgi) using the Blast align. The primer set COⅠ-A was found to be optimal, showing 100% amplification efficiency in 11 fresh meats (including pork, beef, mutton, chicken, duck, pigeon meat, horseflesh, ass meat, goose, rabbit meat and rat meat) with optimized PCR procedure. Eighteen meat adulteration models were founded to test the minimum detected adulteration rate by low economic value meat, and the results showed that the minimum detected adulteration rates of beef and mutton were 5%, and the rates of pigeon meat, goose, and rabbit meat were 10%, when added by the six low economic value meats (including pork, chicken, duck, horseflesh, ass meat and rat meat). To sum up, the method is simple, sensitive and reproducible, which is suitable for the detection of adulteration in the 11 fresh meat products.

Aiming to explore the effects of four commonly used tea packaging materials, including aluminum foil bag, kraft paper bag, aluminum foil-kraft paper bag, and corn fiber bag, on the qualities of Lapsang Souchong black tea during storage, samples were stored at 40 ℃ for eight weeks, and were taken for sensory evaluation and determination of contents of water, tea polyphenols, soluble proteins, free amino acids, and infusion color and aroma at the 1, 2, 4, 6 and 8 weeks. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was used to compare the effects of different packaging materials on aroma components in detail. The results showed that the four kinds of packaging materials had effects on preventing the increase of water content and decrease of tea polyphenol, soluble protein and free amino acid contents. Aluminum foil-kraft paper bag had the best effect on the sample storage quality, and aluminum foil and kraft paper bags had similar effects, and corn fiber bag had the worst effect. However, compared with the unpackaged control tea samples, the protective effects of packaging materials on the above indicators were relatively limited. The packaging materials had obvious influence on aroma retention, and the aluminum foil-kraft paper had the best effect. The aroma sensory score increased first and then decreased, and the optimal aroma sensory of tea in four packaging materials appeared at different time points. This study showed that none of the four commonly used black tea packaging materials could effectively slow down the overall quality deterioration of Lapsang Souchong black tea in this storage model. It’s necessary to use some fresh-keeping measures for the preservation of Kungfu black tea as green tea and oolong tea.

A membrane separation technology was used to make a grading preparation of theabrownines from Tibetan tea, and four theabrownine fractions (TBFs) with the molecular mass of 5-10, ＞10-50, ＞50-100, and ＞100 kDa were got, which were named as TBFs1, TBFs2, TBFs3 and TBFs4, respectively. The physicochemical properties, microstructure, and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity of the four TBFs were comparatively studied. The results showed that the molecular mass of theabrownines was not less than 5 kDa, and the four TBFs with different ranges of molecular mass were all weakly acidic, which had different contents of phenolic hydroxyl, carboxyl group, and the complex compounds including proteins and polysaccharides. Spectroscopic analysis showed that the theabrownines were polyhydroxyphenols and were characterized by an absorption peak near 202 nm. The scanning electron microscope observation showed that the aggregation state of the TBFs was significantly different from each other. Within the range of 10-80 μg/mL, there was a positive linear correlation between the theabrownine concentration and its DPPH radical scavenging ability. In addition, the four TBFs showed significantly different antioxidant activities from each other, and the most active fraction was TBFs4 (＞100 kDa).

Combined with gas chromatography-mass spectrometer (GC-MS), we compared the adsorption characteristics and laws of aroma compounds for green tea, yellow tea and white tea by using three methods, i.e. headspace solid-phase micro-extraction (HS-SPME), headspace stir bar sorptive extraction (HS-SBSE), and Tenax TA. Under the same ratio of tea to water, equilibrium time, extraction temperature and adsorption time, the enrichment effect of the three methods on aroma compounds for nine tea samples was analyzed. The results showed that the absorption capacity of Tenax TA was the highest; HS-SBSE was the second; and HS-SPME was the lowest. HS-SPME and HS-SBSE showed better enrichment effect for terpene and low water-soluble compounds, while Tenax TA showed better adsorption capacity of aldehyde and could trap some of the water-soluble and highly volatile substances easily. In addition, compared with Tenax TA, the relative content of long carbon chain compounds such as linalool, linalool oxide and cis-3-hexenyl hexanoate extracted by HS-SPME and HS-SBSE was significantly higher (P＜0.05), while the relative content of short carbon chain compounds including 2-methylbutyraldehyde and 1-penten-3-ol was lower (P＜0.05). In conclusion, the analysis results of Tenax TA method is more authentic in aroma composition, in consideration of a strong competition effect during HS-SPME and HS-SBSE extraction.

In this experiment, the biochemical components of 18 white tea samples with different grades, three-year-aging and compressed treatments or not from Fujian Province were tested and compared. At the same time, the umami, bitterness and astringency of white tea samples were graded by the method of taste equivalent quantification evaluation. Based on the above results, correlation analysis, principal component analysis and multiple linear regression analysis were used to screen the main biochemical components related to each taste; furthermore, evaluation models were established. The results showed that the average amount of tea polyphenols and amino acids in Baihaoyinzhen (BHYZ) samples were 20.14% and 5.42%, respectively. With the decrease of white tea grade, the contents of tea polyphenols, ester catechin and gallic acid decreased, while the flavone content increased. Amino acids and caffeine contents were similar in BHYZ and Baimudan (BMD), but significantly higher than those in Shoumei (SM) white tea. In aged white tea, the contents of amino acids, soluble sugar, tea polyphenols, ester catechin and gallic acid in compressed aged white tea were lower than those in loose aged white tea. For quantitative evaluation of the umami, BHYZ got the highest score, and BMD had the higher scores in umami, astringency and bitterness. For SM, all taste scores were the lowest. The umami and astringency scores of aged white tea were lower than those of new white tea, and the umami score of the compressed aged white teas further declined. Overall, this study provides consumers with a scientific method to understand the quality of white tea, enriches the biochemical theory for white tea, and provides a theoretical basis for the promotion of white tea.

Taking advantage of TaqMan^? array microfluidic card technology, 24 primer-and-probe sets of real-time fluorescence quantitative polymerase chain reaction (RT-PCR) for identification of 24 different animal species (categories) were assembled in one array to achieve simultaneous detection of multiple animal-derived components. The repeatability, specificity and sensitivity of the method were verified. Coefficient of variation (CV) value was used to indicate the repeatability in one array card when detecting the same component (species). Among 66 CV values, 11 CV values were less than 1%; 15 CV values were more than 2%; and the remaining 40 CV values were between 1% and 2%; but none of them was higher than 3%. P value showed the repeatability among different array cards when detecting the same component. Among the 22 P values of the 22 animal-derived components, only one was less than 0.05, which indicated the significant difference of the CV values of the components between the cards. But none of the resting 21 components showed significant inter-plate differences. Therefore, the vast majority of the components tested in this study showed good repeatability both in-card and inter-card. No false positive results were found in TaqMan array tests, but false negative results were appeared in two component detection. The sensitivity of TaqMan array assay was not higher than that of the individual RT-PCR assay. Ten of the 22 components decreased to 10% of the originals in detection sensitivities; another one component even decreased to 1%. And the remaining 11 components were consistent with that of the individual RT-PCR. However, in general, TaqMan array approach can meet the needs of authenticity identification in terms of repeatability, specificity and sensitivity, which offers promise for rapid and simultaneous identification of multiple animal-derived components.

Twelve different flavonoid glycosides were identified and quantified by ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) method from tea flower of five different tea plant cultivars (Meizhan, Shuigu, Huangyezao, Zhenghe Dabai, and Fujian Shuixian), which were myricetin-3-O-rutinoside (Myr-rut), myricetin-3-O-galactoside (Myr-gala), myricetin-3-O-glucoside (Myr-glu), quercetin-3-O-rutinoside-galactoside (Que-rut-gala), quercetin-3-O-rutinoside-glucoside (Que-rut-glu), kaempferol-3-O-rutinoside-galactoside (Kae-rut-gala), quercetin-3-O-galactoside (Que-gala), quercetin-3-O-glucoside (Que-glu), kaempferol-3-O-rutinoside-glucoside (Kae-rut-glu), kaempferol-3-O-galactoside (Kae-gala), kaempferol-3-O-rutinoside (Kae-rut）, kaempferol-3-O-glucoside (Kae-glu）.The contents of Kae-rut-glu and Kae-rut-gala were significantly higher than other flavonoid glycosides in tea flower, which were up to 1.208 mg/g in Meizhan and 0.962 mg/g in Huangyezao, respectively. The content of Que-rut-gala in tea flower of Zhenghe Dabai, Huangyezao, and Shuigu were significantly higher than that in others; the content of Que-rut-glu in tea flower of Fujian Shuixian was the highest among the five tea plant cultivars, which was significantly higher than that of Zhenghe Dabai, Meizhan, and Huangyezao; the amount of Myr-glu in Fujian Shuixian tea flower was four times higher than that of in others; however, its Myr-gala’s amount was the lowest in the five cultivars. The total amount of flavonoid glycosides in Zhenghe Dabai tea flower was the lowest in the five cultivars. In three kinds of flavonoid glycosides, kaempferol glycosides’ content was the highest, and myricetin glycosides’ content was the lowest, and the majority of them were glycosylated with tri-glycosides in all the tested cultivars.

Headspace solid-phase microextraction and gas chromatography-mass spectrometry were used to study the aroma components and differences of 14 white tea samples of different grades in Fuding of Fujian Province. The results showed that 50 kinds of main aroma components were detected, including leaf alcohol, benzaldehyde, benzyl alcohol, linalool and its oxides. Using heat map, we found that the aroma components of Baihaoyinzhen (BHYZ) and Baimudan (BMD) were similar, and both of them were rich in alcohols with floral aroma. While Shoumei (SM) contained more aldehydes, ketones, esters and lactones, including ionone, dihydro-actinidiolide and methyl salicylate. Furthermore, the characteristic aroma components in different grades of white tea were screened by partial least squares-discriminant analysis (PLS-DA). The results showed that the characteristic aroma components of BHYZ were phenylethyl alcohol, cis-jasmone, etc. For BMD, they were β-cedarene, β-elemene, etc; and for SM, they were nerylacetone, ionone and other aroma components. The above results provide a scientific method to determine the main aroma substance in different grades of white tea, and to distinguish the grade of white tea according to the main aroma components.

In order to extend the shelf life of chilled meat, the effects of preservative treatment conditions on the quality of chilled meat were studied. Taking the meat from Yuanxiang black pigs as raw materials, the chilled meat (pork Longissimus dorsi muscle) were stored at 0 ℃ with the treatments of cinnamon essential oil-chitosan coating and polyethylene (PE) fresh-keeping film packaging (treatment group A), impregnated in dilute glacial acetic acid and polyvinyl dichloride (PVDC) low-oxygen conditioning (50% CO₂+35% O₂+15% N₂) packaging (treatment group B), cinnamon essential oil-chitosan coating and PVDC low-oxygen conditioning (50% CO₂+35% O₂+15% N₂) packaging (synergistic group), and impregnated in dilute glacial acetic acid and PE fresh-keeping flim packaging (control group). The physicochemical and biological indicators were investigated, including pH value, total volatile basic nitrogen content, total numbers of colony, the numbers of Pseudomonas and Brochothrix thermosphacta, redness value (a^*), elasticity and juice loss rate during storage, and the principal component analysis was carried out. The results showed that: compared with the control group, the treatment group A, treatment group B and synergistic group could effectively inhibit the increase of pH, total volatile basic nitrogen content, total numbers of colony, Pseudomonas, B. thermosphacta, and juice loss rate; and they could significantly slow down the decrease of a^* and elasticity (P＜0.05). In the late storage period (7-9 d), the fresh-keeping effect of synergistic group was significantly better than that of the treatment group A and B (P＜0.05). Compared with the control group, the synergistic group could significantly improve the storage quality of chilled meat and prolong its shelf life for about 4 days. Through the principal component analysis of the eight indicators, the total volatile basic nitrogen content, total numbers of colony, pH, juice loss rate, the numbers of Pseudomonas and B. thermosphacta showed a positive correlation among these indicators. The above indicators were negatively correlated with a^* and elasticity (P＜0.01). The eight test indicators could be simplified into one principal component, and the variance contribution rate was 96.557%, which could better reflect the original information. The order of contribution rate in the first principal component was Pseudomonas count＞B. thermosphacta count＞total numbers of colony＞juice loss rate＞pH＞elasticity＞total volatile basic nitrogen content＞a^*. The first principal component mainly reflected the degree of microbial proliferation and protein hydrolysis and oxidation of the chilled meat during storage. The linear regression function for the first principal component was Y₁=0.128X₁＋0.126X₂＋0.128X₃＋0.129X₄＋0.129X₅－0.123X₆－0.126X₇＋0.128X₈, which can provide data support and reference for the low temperature preservation of chilled meat.

Skipjack tuna was enzymatically hydrolyzed to prepare xanthine oxidase (XOD) inhibitory peptides. The enzymatic hydrolysis process was optimized by investigating the effects of protease types and enzymatic dosages, pH, temperature, time and their interactions on degree of hydrolysis, nitrogen recovery, XOD inhibition activity and the contents of carnosine and anserine using one-factor-at-a-time method and response surface methodology. The optimal process parameters were as follows: the application of neutrase with the dosage of 489.86 U/g, the pH of 7.08, the temperature of 49.5 ℃, and the time of 5 h. Under the optimal conditions, the degree of hydrolysis was 22.38%; nitrogen recovery was 83.81%; XOD inhibition activity was 62.26%; and the contents of carnosine and anserine were 0.05% and 2.45% (on a dried basis), respectively, which were all in good agreement with the predicted values. The XOD inhibitory peptides obtained were mainly composed of a fraction with molecular mass of less than 1 000 Da. The Pearson’s correlation analysis showed that the XOD inhibition activity of dorsal and ventral muscle in skipjack tuna was not associated with the contents of carnosine and anserine, and it may be due to the production of other XOD inhibitory peptides during the enzymatic hydrolysis.

This study aimed to improve the withering process of the white tea manufacturing and to achieve the stability and controllability of white tea quality. Fresh leaves plucked from tea (Camellia sinensis) bushes of 15 cultivars were used to explore the effects of withering temperatures (30, 25, 20 ℃) on the dehydration rate, sensory quality and biochemical compositions of white tea. The contents of biochemical compositions were compared among the samples based on the two-dimensional point set distribution and principal component analysis. The results showed that the water loss rates of all tea shoots tended to decelerate gradually under the different withering temperatures, the higher the withering temperature, the faster the water loss rate. Dehydration rate equation was consistent with the hyperbolic function. Compared with the natural withering, the average withering time at 25 ℃ was significantly shortened by 13.6 h. The sensory evaluation suggested that the white tea prepared under the withering condition of 25 ℃ had the highest quality, which was equivalent to the quality under the natural withering. The analysis of biochemical composition found that there was no difference between withering at 25 ℃ and natural withering. In conclusion, the time of the white tea withering at 25 ℃ was greatly shorten and the quality of the prepared white tea was superior, which could further improve the production efficiency of the white tea, and provide effective references for the improvement of the white tea process.

The taste quality of yellow tea and the contribution of taste-chemical compositions to yellow tea taste were explored by sensory evaluation, taste-compound detection, chemometrics analysis and dose-over-threshold factors (DoT), based on Zhejiang partial main cultivated cultivars and an improved process in north Zhejiang yellow tea production area. The results showed that the yellow tea, which was processed from Yingshuang, Baiyeyihao and Zhenong 113 tea cultivars and different yellowing process, presented varying degrees of sweet, mellow, umami, astringency and stewed taste. There were significant differences on the most of taste-chemical compositions among yellow teas from three tea cultivars, while there was a small difference among yellow teas from the same tea cultivar. The content analysis and partial least square discriminant analysis (PLS-DA) indicated that the taste quality of yellow tea was influenced remarkably by tea cultivars. The catechins like (-)-epigallocatechin-3-gallate (EGCG), (-)-gallocatechin-3-gallate (GCG), (-)-epigallocatechin (EGC), flavonol glycosides like myricetin-3-O-galactoside (Myr-gal), quercetin-3-O-glucoside (Que-glu), kaempferol-3-O-rutinoside (Kae-rut), amino acids like glutamic (Glu), theanine (Thea), arginine (Arg), aspartic acid (Asp), asparagine (Asn), et al., had great contribution to yellow tea taste characteristic under the experimental conditions. The further research of DoT value indicated that the specific taste of single compound in the aqueous solution would change in the complex tea liquor, which may be due to the interaction among different compounds.

Acetylcholinesterase (AChE) is a key enzyme for the detection of organophosphorus and carbamate pesticide residues by enzyme inhibition method. In this study, human acetylcholinesterase (hAChE) was secreted and expressed by Pichia pastoris expression system, and its sensitivity to eight pesticides was evaluated, which laid the foundation for large-scale industrial production of highly sensitive enzyme sources. Primers F1 and R1 were designed according to the published gene sequence of hAChE in GenBank. Then the hAChE gene coding region sequence was amplified by high fidelity PCR using pReceiver-M02-hAChE-ORF plasmid as the template, and the recombinant expression vector pPIC9K-hAChE was constructed by inserting into the vector pPIC9K through double enzyme digestion of SnaB I and Avr Ⅱ. The transformant was selected to sequence and verify the accuracy of the sequence. The linearized pPIC9K-hAChE by Sal I was electro-transformed into P. pastoris GS115. The recombinant strains were screened by minimal dextrase medium (MD) plate and G418 resistance gradient plate. Finally, the positive strain colony was screened on the yeast extract peptone dextrose medium (YPD) plate with 4.00 mg/mL G418 resistance and was identified by polymerase chain reaction (PCR). The expression of the recombinant strain was induced by 0.5% methanol for 144 h. The sodium dodecyl sulfonate (SDS)-polyacrylamide gel electrophoresis map of the fermentation supernatant showed an obvious protein band at 65 kDa, and the size was consistent with the expected hAChE protein. The purified hAChE was obtained using a Q-Sepharose FF chromatography. The content of hAChE protein in the fermentation supernatant was 1.330 mg/mL and accounted for 5.58% in total protein by Bradford method. The highest enzyme activity reached 1 080 nmol/(min?mL) after purification. By preliminary calculation of the 50% inhibitory concentration (IC₅₀) of the eight common pesticides of the fermentation supernatant, it was found that trichlorfon＞dichlorvos＞arbofuran＞malathion＞dimethoate＞Methamidophos＞Carbaryl＞chlorpyrifos, suggesting that hAChE is most sensitive to chlorpyrifos.