In order to improve the physical stability of egg yolk (EY) incorporated in acidic emulsion systems, the electrostatic complex formed by EY protein and phytic acid (PA) was used to stabilize the emulsions. The effects of different PA concentrations (0%–0.8%) on the physical stability of EY protein and EY emulsions under acidic condition were studied. The results show that at pH 3.0 and PA concentration of 0.012 5%–0.8%, EY protein and PA form an insoluble electrostatic complex (EY-PA). The emulsion stabilized by the complex formed between 0.2% PA and EY containing 1% protein had a higher viscosity and a significantly lower particle size and creaming index (P < 0.05) than the control emulsion. In addition, the interfacial protein adsorption capacity was significantly increased (P < 0.05), the emulsion droplets were more evenly distributed, and the anti-cohesion effect was improved. Therefore, the EY-PA electrostatic complex can control the physicochemical properties of EY emulsions and improve the physical stability of EY in the acid emulsion system.

Na-ZSM-5 support was prepared and loaded with Ru by an impregnation method to obtain a supported metal catalyst. The catalyst was activated by electrochemical catalysis for application in the isomerization of corn oil. The influence of the reaction conditions on the isomerization efficiency was studied. The optimum reaction conditions were determined as follows: catalyst dosage 5%, isomerization time 3 h, stirring speed 600 r/min, and isomerization temperature 160 ℃. The relative activity of the supported Ru/Na-ZSM-5 catalyst was maintained at 75.2% after repeated use for five times. Finally, the major components and physicochemical properties of the reacted corn oil were studied. The results showed that the oil contained 12.32% c9,t11-CLA and 8.45% t10,c12-CLA as well as only 1.63% trans oleic acid. Its acid value was 1.17 mg/g, iodine value 103.08 g/100 g, peroxide value 4.31 mmol/kg, saponification value 201.56 mg/g, and unsaponifiable matter content 16.53 g/kg, which revealed good quality.

The structure, physicochemical properties and emulsifying properties of Cerasus humilis fruit pectin (CSP) were studied. Compared with commercial apple pectin (CAP), the content of galacturonic acid (GalA) in CSP was lower, while the contents of some metal elements (Ca, Zn and Mg), protein and total polyphenols were significantly higher (P < 0.05). Structural characterization by scanning electronic microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, gas chromatography (GC-MS) and X-ray diffraction (XRD), demonstrated that CSP showed a smooth surface with continuous and curly lamellar or filamentous structure. It was a high methoxy pectin with degree of esterification (DE) of 52.04% and was amorphous Arabinose (65.7%), galactose (18%) and rhamnose (11%) were the major three neutral monosaccharides in CSP. Moreover, the emulsifying properties of CSP were determined by measuring its zeta potential value and the emulsification index (CI), emulsification capacity (EC), emulsion stability (ES), microstructure, droplet size and rheological properties of an emulsion system stabilized by it. Our results show that CSP has good emulsifying properties and thus has great potential to be used as a natural emulsifier.

In order to better understand the functional mechanisms of the secretome of Rhodosporidium paludigenum in its interactions with Botrytis cinerea and tomatoes, Q Exactive UHMR hybrid quadrupole-orbitrap mass spectrometry combined with bioinformatics was employed to identify the unique peptide sequences of the proteins. The results showed that 1 632 unique peptide sequences from Rhodotorula sourced proteins were found in the fermentation supernatant of R. paludigenum, and 58 classical secretory proteins and 433 non-classical secretory proteins were identified using the software SignalP, WoLF PSORT, TargetP, TMHMM, big-PI Predictor and Secretome P. The secretory proteins of R. paludigenum effectively inhibited the spore germination of B. cinerea by 31.4%, and enhanced resistance of tomato fruits to B. cinerea infection around the wound with an inhibition rate of 50.1%. Moreover, based on the UniParc data, 18 (31.0%) carbohydrate-active enzymes such as alginate lyase and β-glucosidase were found in the secretome of R. paludigenum, which may play a vital role in the interaction between R. paludigenum and Botrytis cinerea and in inducing systematic resistance of tomato fruits to gray mold.

To solve the problem that the glucose consumption capacity of Corynebacterium glutamate differed at different stages of L-isoleucine production, the feeding rate of glucose was dynamically adjusted. Corynebacterium glutamate YILM1504 was cultured at an initial glucose concentration of 80 g/L and with suboptimal glucose feeding at a feeding rate equal to 90% of the maximum feeding rate. The dynamic glucose feeding rate was as follows: 0 g/(L·h) for 0–8 h, 5.40–7.47 g/(L·h) for 8–14 h, 7.47–7.00 g/(L·h) for 16–24 h, and 7.00–5.20 g/(L·h) for 24–40 h. The yield of L-isoleucine was 44.32 g/L and the conversion rate of glucose to L-isoleucine was 19.63%. The comparative analysis of metabolic flows revealed that the ratio of carbon distribution between and the hexose monophosphate pathway (HMP) and the Embden-Meyerhof-Parnas pathway (EMP) was 0.56. Moreover, the metabolic flow toward Ile was increased by 18.92%, while the metabolic flows toward Val, Leu, and Ala were reduced by 67.12%, 72.21%, and 30.23%. In conclusion, this fine glucose feeding strategy can meet the dynamic glucose demand of C. glutamicum during the fermentation process, resulting in enhanced isoleucine titer, reduced by-product accumulation and significantly prolonged acid production peak period.

Lipid transfer protein (LTP, Pru p 3) is the major allergen protein of peach (Prunus persica L. Batsch). In this study, Pru p 3 was purified from the peel and pulp of honey peach, nectarine, flat peach, and yellow-fleshed peach using a microchromatographic column, ZipTipC18, and identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that Pru p 3 with a purity of 95% was obtained and confirmed. The purification method can provide technical support for further studies of peach Pru p 3.

Changes in the quality and protein conformation of semi-dried beef jerky during fermentation with Lactobacillus sakei were investigated. The moisture content, moisture distribution, pH, water activity, shear force and sensory quality of the samples were determined. Besides, in order to examine the quality differences, principal component analysis was conducted on the data from 10 electronic nose sensors. The effect of fermentation time on the protein conformation of semi-dried fermented beef jerky was studied by Raman spectroscopy. The results showed that the pH and water activity decreased with the increase in fermentation time and reached the minimum at 60 h. The shear force decreased first and then increased during the fermentation process, and reached its minimum at 24 h. The moisture content decreased first and then gradually remained stable. After fermentation, the content of immobilized water decreased whereas the content of bound water increased. The sensory scores for color, flavor, chewiness and overall quality of semi-dried beef jerky fermented for 36 h were significantly higher than those at other fermentation times. Electronic nose analysis showed that esters, alcohols and other volatile compounds were produced during fermentation, imparting a unique flavor to the product. By analyzing the Raman spectra, it was found that the relative contents of α-helix and t-g-t conformation were the lowest at 48 h of fermentation, and the protein stability of the product decreased after fermentation. Comprehensive analysis reveals that L. sakei can be used as a starter culture for semi-dried fermented beef jerky, and the fermentation time should be controlled within the range of 24–48 h.

To identify the critical amino acids in the linear immunoglobulin (IgE)-binding epitopes of Jug r 1, a major English walnut allergen and to evaluate the accuracy and efficiency of two immunoinformatics methods in predicting these amino acids, the present study used the immunoinformatics methods to predict the key amino acids in the three linear epitopes of Jug r 1 and identified the amino acids by alanine scanning mutagenesis. Then a series of mutant peptides were synthesized by a solid phase method for the characterization of the epitopes and critical amino acids. The IgE-binding epitopes were immunolabeled with individual sera from walnut-allergic patients in China as probes by enzyme linked immunosorbent assay (ELISA). The results showed that Leu4, Leu7, Leu8, Ile20, Thr21, Ile22, Ile127, Ser129 and Gln130 were the critical amino acids in the IgE-binding epitopes. The combination of the two immunoinformatics gave 100% predication accuracy, but the prediction efficiency was only 11%. Therefore, the prediction accuracy can be improved by the combined use of the immunoinformatics methods, but some critical amino acids may be neglected. Immunoinformatics combined with alanine scanning mutagenesis is an important approach to identify the critical amino acids in the epitopes.

The community composition and diversity of endophytes in Sclerotinia sclerotiorum-infected and healthy mulberry fruits were analyzed using Illumina MiSeq high-throughput sequencing. The results showed that at a 97% sequence similarity level, 281 and 259 bacterial and fungal operational taxonomic units (OTUs) were identified. The endophytic bacterial community mainly included Cyanobacteria, Proteobacteria, Firmicutes and Bacteroidetes, and Cyanobacteria_norank and Mitochondria_norank showed a significant downward trend in the infected fruit with high sensitivity; the endogenous fungal community mainly included Ascomycota, Fungi_unclassified and Basidiomycota. Fungi_unclassified and Basidiomycota were significantly affected by the pathogen. Fungi_unclassified was hardly found in the infected group and the abundance of Basidiomycota decreased by 99.07%. The diversity of endophytic fungi could clearly discriminate between the infected and healthy fruits, being much higher in the former than the latter. Linear discriminant analysis effect size (LEfSe) showed that Pantoea was the major bacterial group in the infected fruit. Ascomycota and its branches (Ciboria, Sclerotiniaceae, Helotiales, Leotiomycetes), Sordariomycetes, Dothideomycetes, Xylariales, and its branches (Xylariales_f_Xylariales_Incertae_sedis, Monographella) were the significantly differential biomarkers between the healthy and infected fruits.

In order to explore the fermentation and storage characteristics of set yogurts made from sheep milk and cow milk, their pH, titratable acidity, texture properties, taste characteristics, viable bacterial population and sensory scores were determined by a pH meter, an acidity titrator, a texture analyzer, an electronic tongue, viable counting and sensory evaluation, respectively. During the fermentation process, the two yogurts showed the same pH trends. The pH decreased slowly in the first 2.5 hours, then dropped rapidly, and finally kept declining slowly from 0.5 h before coagulation until the completion of coagulation. The fermentation was completed after 5 and 4.5 h for fermented sheep milk and cow milk, respectively. During 24 days of storage at 4 ℃, the pH of both fermented milks dropped gradually, and fermented cow milk decreased more than did fermented sheep milk. The titratable acidity of fresh sheep milk was higher than that of fresh cow milk, and the titratable acidity of fermented sheep milk was similarly higher than that of fermented cow milk at the end of fermentation. Moreover, fermented sheep milk containing Lactobacillus paracasei subsp. paracasei Zhang (YSM) and that containing L. bulgaricus and Streptococcus thermophilus (JDM) had higher hardness and consistency, and significantly higher cohesiveness and viscosity than did fermented cow milk containing L. bulgaricus and S. thermophilus (JDN). The type of milk was found to be the main factor that affects the hardness, consistency, viscosity and viscosity of yogurt, while the addition of probiotic L. paracasei subsp. paracasei Zhang had little influence on any of these indicators. The results of electronic tongue revealed that the taste sensation value for richness of fermented sheep milk was significantly higher than that of fermented cow milk, while the sourness sensation value was lower that of fermented cow milk. There was no significant difference in the sensation scores for sweet, bitter, salty, astringent or umami taste between the two fermented milks. The overall sensory score of fermented sheep milk was higher than that of fermented cow milk, and there were differences in the sensory scores for taste, texture, and liking degree but not color or smell between them. Total viable bacterial count gradually declined during the 21-day storage period for all fermented milk samples. YSM showed the highest viable bacterial count and its value on day 21 of storage was over 10- and 100-fold higher than that of JDM and JDN, respectively. In conclusion, L. paracasei subsp. paracasei Zhang can be used as a candidate starter culture in combined with the traditional yogurt starter cultures of L. bulgaricus and S. thermophilus for the production of set yogurt made from sheep milk for improved functional value.

Totally 10 acid-producing strains were isolated from naturally fermented soy whey (Suanjiangshui) collected from two fermented tofu (sufu) producers in Mouding, Yunnan. The strains were identified by morphological observation, physiological and biochemical identification and 16S rDNA sequence analysis, and their growth characteristics were evaluated. The results showed that Lactobacillus fermentum (YQZ1), Lactococcus raffinolactis (YQZ2), Lactobacillus plantarum (YQZ3), Enterococcus casseliflavus (YQZ4), and Microbacterium oxydans (YQZ5) were the dominant strains in one sample, while Enterococcus faecium (XJZ1), L. plantarum (XJZ2), Lactobacillus paracasei (XJZ3), Enterococcus hirae (XJZ4), and L. paracasei (XJZ5) were the dominant strains in the other. The optimal growth temperature was 32 ℃ for strain XJZ4 and 37 ℃ for the other strains and the natural microflora. Strain XJZ2 had the fastest growth rate, and YQZ1 and XJZ2 had the strongest reproductive ability. YQZ1 and XJZ2 had the strongest acid-producing capacity and the largest accumulation of organic acid, giving acid yield of 43.61 and 50.91 g/L after 48 h, respectively. YQZ3 and YQZ5 had the strongest acid tolerance, followed by YQZ1 and XJZ2. The optical density at 600 nm (OD600 nm) for the cell density of YQZ4 was maintained at 1.53 in the presence of 4 g/100 mL NaCl, whereas the growth of the other strains was inhibited by NaCl concentrations of greater than 4 g/100 mL. It is concluded that the strains YQZ1 and XJZ2 had strong reproductive ability and high acid-producing ability, making their mixed cultures promising candidates to be used in the preparation of Suanjiangshui for shortened fermentation period and improved quality of fermented tofu.

Headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to identify and analyze the volatile compounds of Vidal Blanc grapes cultivated on pergola or vertical trellis system. Heat map, partial least squares-discriminant analysis (PLS-DA), and aroma radar chart analyses were applied to explore the influence of different training systems on the aroma profile of Vidal Blanc grapes. The results showed that a total of 87 volatile compounds were identified. Regardless of training systems, higher alcohols and C6 compounds greatly contributed to the total content of volatile compounds in Vidal Blanc grapes. Terpene compounds accounted for a small fraction of the total volatile compounds in grapes grown on pergola, while they were the most abundant volatile compounds in those grown on vertical trellis. The odor activity value (OAV) was mainly contributed by higher alcohols, terpenes, C6 and C9 compounds. C9 compounds were the major aroma components in grapes from the pergola system, while terpene compounds were the major aroma components in grapes from the vertical trellis system. A total of 24 volatile compounds with OAV > 1 were identified. Most of the volatile compounds showed a gradual increase during the harvest period, and 18 volatile compounds were found to be more abundant in grapes from the vertical trellis system. The aroma radar chart showed that the most prominent aroma characteristics were grassy, floral, and fruity notes and the aroma profile of grapes from the vertical trellis system was better than that of grapes from the pergola system. To sum up, vertical trellis was a more training system than pergola for Vidal Blanc grape in Huanren county, Northeast China.

The changes of taste compounds in Lentinula edodes during vacuum freeze-drying (VFD) were explored using an electronic tongue (E-tongue), high performance liquid chromatography (HPLC) and an automatic amino acid analyzer. Sampling took place after pre-freezing, primary drying, and secondary drying (20, 30, 40 or 50 ℃). E-tongue results showed that L. edodes samples collected at different VFD stages were effectively distinguished. The contents of soluble sugars/mannitols and 5’-nucleotides significantly increased after pre-freezing (P < 0.05). After primary drying, the contents of soluble sugars/mannitol and free amino acids (FAAs) in L. edodes reached maximum values of 185.20 and 44.76 mg/g, respectively among all sampling points. After secondary drying, the content of organic acids increased independent of the drying temperature, while the contents of soluble sugars/mannitols and FAAs showed different decreasing trends with the drying temperature. The umami intensity of L. edodes greatly increased after secondary drying at 30, 40 or 50 ℃, leading to an approximately 2-fold increase in equivalent umami concentration (EUC) values as compared to the fresh sample. In conclusion, most of the taste compounds in L. edodes were well retained during the VFD process. These results should provide insights into understanding the mechanism of change in taste compounds in L. edodes during vacuum freeze-drying and provide an important reference for the development of seasonings based on the taste of L. edodes.

In order to understand the difference in aroma quality among different grades of Baiyaqilan tea and the material basis for it, the aroma quality of four different Baiyaqilan teas was analyzed by quantitative descriptive analysis (QDA) and headspace solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS). Multiple stepwise regression analysis and Pearson’s linear correlation were used to further analyze the relationship of different aroma attribute intensities and volatile compound contents with sensory acceptability. The results of QDA showed that the overall aroma profile of Baiyaqilan tea infusion consisted of floral, grassy, sweet, roasted, woody and caramel notes, and the aroma intensity and acceptability of different Baiyaqilan tea infusions were different. The results of GC-MS showed that there were some differences in the types and contents of volatile compounds in different Baiyaqilan teas, and 55 volatile compounds were detected in the four teas investigated, alcohols being the most abundant, accounting for 46.3%–69.7% of the total content of volatile compounds. Hotrienol, indole, (E)-nerolidol, geraniol, 1-ethyl-1H-pyrrole-2-carbaldehyde and linalool were the main volatile compounds in Baiyaqilan tea. Multiple stepwise regression analysis showed that the floral, grassy and sweet notes were positively correlated with the sensory acceptability, and that the floral, grassy and sweet notes were positively correlated with the contents of 6-methyl-5-ethyl-3-heptene-2-one, geraniol, (Z)-3-hexenyl hexanoate, (Z)-jasmone, (E)-nerolidol, and negatively correlated with the content of dimethyl sulfide. The above results may provide a reference for the objective evaluation of Baiyaqilan tea aroma quality.

In this study, ultra-high performance liquid chromatography-quadrupole-time-of-flight-mass spectrometry (UPLC-Q-TOF-MS) combined with principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) was used to analyze the changes of metabolites in high-salt liquid-state soy sauce during the fermentation process. The results showed that the number and the total peak area of metabolites on day 90 were 1.47 and 6.57 times as high as those on day 1, respectively. During the fermentation process, a total of 155 compounds were identified, 34 of which showed significant difference among fermentation times (variable importance in the projection, VIP > 1), including ten amino acid derivatives, nine fatty acids, five isoflavones, three esters, two organic acids and two alkaloids. The percentages of the peak areas of amino acid derivatives, isoflavones and alkaloids relative to the total peak areas of all differential metabolites increased from 0.44%, 6.82% and 0.02% to 20.11%, 14.88% and 10.81%, respectively. These compounds could be considered as key different metabolites during soy sauce fermentation. Our results may be meaningful for understanding the change of metabolites during soy sauce fermentation and for quality control.

Totally nine volatile trace components in 20 samples of different kinds of Chinese Baijiu were analyzed by liquid-liquid extraction (LLE) combined with gas chromatography-mass spectrometry-selective ion monitoring (GC-MS-SIM). The average recoveries of the developed method were in the range of 81.80%–109.30%, with a precision (relative standard deviation, RSD) of less than 6.00%. Excellent linearity was observed in the tested concentration range (R2 > 0.999 0). The limit of detection (LOD) and the limit of quantification (LOQ) were 0.17–0.91 and 0.58–3.04 μg/L, respectively. The results showed that among the nine functional compounds, three terpenes had higher concentrations in Nongxiangxing Baijiu, and their concentrations in the Baijiu samples from a producer in Chengde, Hebei were higher than those in other samples examined. Four phenolic compounds had the highest concentrations in Zhima-flavor Baijiu, and the total amount of phenolics was 4 301.61 μg/L in sample W09. The concentration of tetramethylpyrazine in Jiang-flavor Baijiu was 2 379.65–2 985.09 μg/L, much higher than that in Zhima-flavor Baijiu (1 116.80–1 309.66 μg/L) and Nongxiangxing Baijiu (245.40–555.76 μg/L). The concentration of linoleic acid ethyl ester significantly varied in the range of 1 951.96–7 183.35 μg/L among different samples expect for W17, W19 and W20.

In order to explore the change of lipids in raw milk during cold storage at 4 ℃, acid value (AV) and peroxide value (PV) were measured to determine the degree of fat oxidation in raw milk. Ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) was used to analyze the differences and changes of lipid metabolites during cold storage. The results showed that both AV and PV continued to increase during 6 days of cold storage, and the rate of increase was the fastest from day 0 to day 1. The analysis of differential metabolites showed that the changes of the metabolic system in raw milk were very complicated, and the types and changes of lipid metabolites were the most prominent among the six significantly differential metabolites identified. The number of lipid metabolites increased from 9 to 24. Further analysis found that the expression levels of free fatty acids and phospholipids fluctuated greatly on day 3 to 4 and day 6, respectively. Based on these results combined with KEGG pathway analysis, it was found that fatty acid biosynthesis in which free fatty acids are involved changed significantly during cold storage (P < 0.05). On day 3, the most lipid metabolism pathways (9) were identified. Therefore, the third day of cold storage?could be seen as the key point for quality control of raw milk.

Satsuma mandarin fruit were subjected to heat treatment (HT) or ozone fumigation (OF) treatment after harvest for quality preservation. The change of volatile compounds in the fruit peel before and after treatment was analyzed by gas chromatography-ion mobility spectrometry (GC-IMS). In total, 49 volatile compounds were identified, including 13 alcohols, 12 aldehydes, 9 terpenes, 7 esters, 4 ketones, 3 furans and 1 acid. A GC-IMS fingerprint was developed for each group. It was found that principal component analysis (PCA) could effectively distinguish the different treatment groups. Seventeen volatile marker compounds (variable importance in the projection, VIP > 1) were selected by partial least squares discriminant analysis (PLS-DA), and heat map clustering analysis was performed on these compounds, revealing that the volatile marker compounds of HT and OF samples were similar to each other. The results showed that both treatments significantly increased the contents of alcohols, aldehydes, esters and terpenes in citrus peel, thereby having the potential to enhance disease resistance and prolong the shelf life. Meanwhile, GC-IMS could allow rapid identification of the differences in volatile compounds in samples subjected to different postharvest treatments.

A method for the quantitative determination of ergosterol in edible fungi was established by using deuterated chloroform as the solvent and pyrazine as the internal standard. The C-18H proton single peak at δ 0.63 was selected as the target characteristic peak after optimizing the sampling parameters, acquisition time (AT), the number of scans (NS) and relaxation delay time (D1). The methodological evaluation results showed that the calibration curve was linear in the concentration range of 0.55–5.30 mg/mg with correlation coefficient (R2) of 0.999 7. The limit of detection and the limit of quantitation were 0.001 8 and 0.045 0 mg/mL, respectively. The relative standard deviation (RSD) values for precision and stability were both less than 2% and the average recovery of the added ergosterol was 103.491 9%. The specificity of the developed method was verified by applying it to detect three varieties of edible fungi samples, indicating that this method has the advantage of rapidity and accuracy.

The changes in the mass loss rate, color, water distribution and texture properties of the dorsal muscle of sea bass at different steaming times were analyzed. The differences in taste and smell among fish samples was evaluated by free amino acid analysis, electronic tongue and electronic nose. The results indicated that the mass loss rate increased significantly with the extension of steaming time (P < 0.05), and the immobilized water was gradually transformed into free water and finally lost, while the bound water content did not change significantly. The firmness and chewiness first decreased and then increased significantly, while the opposite trend was observed for the elasticity. The L* and b* value significantly increased during steaming (P < 0.05), while the a* value decreased significantly (P < 0.05). The total amount of free amino acids first increased and then decreased, reaching the highest level after 10 min of steaming. His, Gly, Ala, Lys and Glu were the major flavor amino acids in sea bass muscle. Both the electronic tongue and the electronic nose could well distinguish the taste and smell characteristics of fish muscle at different steaming times. In conclusion, sea bass fillets with specified size steamed for 8–10 min had good quality and flavor.

Free amino acids, organic acids and volatile flavor components in samples of tofu coagulated with fermented tofu whey collected at different ripening stages were determined. The results showed that free amino acids and organic acids were the major sources of taste substances; sour-taste amino acids were the major taste components, accounting for 33%–35% of the total amino acids at all tested ripening stages. Lactic acid, acetic acid and citric acid were the most abundant flavor substances during the ripening process, accounting for approximately 50.08%–65.00% of the total organic acids. A total of 84 flavor compounds, including aldehydes, alcohols, phenols, furans and other compounds, were detected in the tofu samples, together endowing the tofu with a unique fermented flavor.

The change of volatile flavor substances in nano-film packaged Hypsizygus marmoreus was studied in this work. The mushroom was packaged with a new polypropylene nano-film (0.05 mm) and stored at 4 ℃ for up to 12 days. During this period, the volatile components were analyzed by headspace solid phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS), and the characteristic flavor components were determined by relative odor activity value (ROAV) and principal component analysis (PCA). A total of 66 volatile components were identified during storage, including 23 aldehydes, 22 alcohols, 10 ketones, 3 esters, 4 carboxylic acids and 4 furans. The total content of volatile compounds showed a trend of first decreasing and then increasing, with values of 98 927, 28 079 and 89 021 μg/kg on days 0, 6 and 12, respectively. ROAV analysis showed that n-octyl aldehyde, 1-octene-3-ketone and 1-octene-3-alcohol were the characteristic flavor components of H. marmoreus, and 2-pentyl furan also contributed greatly to the flavor of H. marmoreus. Trans-2-octenal played a key role in the formation of the flavor of fresh H. marmoreus. Trans, trans-2,4-nondienal and 3-octyl were the key substances for the flavor deterioration of H. marmoreus. PCA analysis showed that aldehydes and alcohols were the most important flavor contributors. It can be concluded that samples of H. marmoreus from different storage periods could be distinguished according to the change of volatile components, which may provide the basis for rapid quality detection, flavor identification and shelf life prediction.

In order to explore the effect of different processing methods on the flavour of dried Ammodytes personatus, the volatile flavor compounds of dried fish produced by boiling in salt solution followed by cold air drying (SCC) or cold air drying (CD) were analyzed by electronic nose (E-nose), gas chromatography-ion mobility spectroscopy (GC-IMS), an automatic amino acid analyzer and high performance liquid chromatography (HPLC). The results showed that there were significant differences in the smell and taste of dried A. personatus from different processing methods. Both E-nose and GC-IMS could distinguish the smell of the different samples. By GC-IMS we identified 68 volatile components, including heptanal, pentanal and 3-methylbutanal, having an important impact on the formation of the unique flavor of dried fish, and 3-methylbutanal was detected in the CD group but not in the SCC group. The major umami amino acid in dried A. personatus was Glu, and the major flavor nucleotide was inosine 5’-monophosphate (IMP). The contents of umami and sweet amino acids relative to the total free amino acids in the CD group were significantly higher than those in the SCC group. Additionally, the taste activity value and equivalent umami concentration in the CD group were also higher than those in the SCC group. Therefore, the flavor of dried A. personatus prepared by direct cold air drying was superior to that produced by boiling in salt solution followed by cold air drying .

In this study, headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and the Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine (TCM) were used to establish a fingerprint for volatile components in the young leaves and buds of Toona sinensis from different growing areas in Henan Province. Meanwhile, a comprehensive evaluation on volatile components of T. sinensis was conducted through similarity evaluation and chemical pattern recognition (cluster analysis and principal component analysis). The results showed that the established standard fingerprint was consistent with the results of cluster analysis and principal component analysis, and all of them could clearly distinguish T. sinensis from different growing areas. The major components causing the flavor difference among different batches of T. sinensis were identified to be 2-hexenal, 2,4-dimethylthiophene, farnesol acetate and 2-methyl-3-methylene-cyclopentanecarboxaldehyde. Meanwhile, the comprehensive score for volatile components of T. sinensis planted on mountains in Xinyang was the highest. The results from this study may provide a theoretical basis and technical support for rapid geographical origin tracing and quality control of T. sinensis.

In this study, the dry aroma profile and flavor characteristics of coffee samples from Lincang, Yunnan were analyzed by headspace solid phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and were figured out by odor activity value (OAV), and the cupping quality was evaluated by a team of professional coffee tasters. The results showed that a total of 85 dry aroma component were identified, and little differences in the aroma component contents among samples from different regions of Lincang. Meanwhile, 27 characteristic flavor compounds (OAV > 1) were detected, which were responsible for the honey-like, dark chocolate-like, creamy, caramel-like and roasted nut-like notes and also contributed to the maple syrup-like, sour cheese-like, tropical fruity, jam-like and flowery flavors. The cupping test results showed that Lincang coffee scored high overall, and the cupping quality was greatly affected by the geographical origin. The findings of this study can provide a theoretical reference for Lincang coffee sale and promotion.

In this study, headspace solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the types and relative contents of volatile flavor substances in Takifugu bimaculatus during cold storage at 0 or 4 ℃ so as to explore the change of volatile substances in the fish during cold storage. The results showed that the fuzzy mathematics gave high sensory scores for Takifugu bimaculatus cold stored for 1–3 days, and reached the upper limit of consumer acceptance on day 7 and 9 for 4 and 0 ℃, respectively. Principal component analysis (PCA) and linear discriminant analysis (LDA) of the electronic nose data showed clear differences in the volatile flavor substances in T. bimaculatus cold stored for different periods of time, which was consistent with the results of HS-SPME-GC-MS. Forty-eight volatile substances were detected, including hydrocarbons, alcohols, aldehydes, esters, aromatic compounds and nitrogen- and sulfur-containing heterocyclic compounds. The fresh fish flesh smelled fishy smell but refreshing. After 11 days of refrigeration, the fishy smell became stronger, and rancid and sour odors appeared.?Nitrogen- and sulfur-containing heterocyclic compounds and aldehydes were the major compounds responsible for the flavor deterioration. Odor activity value (OAV) analysis showed that 1-octene-3 alcohol, hexanal, octanal, nonaldehyde and 2,3-octandione were the key flavor substances of the fish during refrigeration storage. PCA was used to construct the comprehensive evaluation model for volatile flavor substances: T = 0.83T1 + 0.15T2, and the evaluation results were significantly negatively correlated with the sensory evaluation results (P < 0.01). In conclusion, electronic nose combined with HS-SPME-GC-MS can be used to discriminate the differences in the volatile flavor components of T. bimaculatus during cold storage, which may provide a theoretical reference for investigating the changes of volatile flavor compounds in T. bimaculatus during cold storage.

A comparative analysis of the glyceride composition in infant formula powders (IFP) with five different fat sources and human milk (HM) was studied. The results showed that there were significant differences in the fat composition between HM and IFP. The content of diglyceride (DG) in HM was (7.84 ± 0.57)%, which was significantly higher than the maximum level in IFP, (1.26 ± 0.22)% (P < 0.05). DG(18:2/18:2) and DG(18:1/18:1) were the most abundant types of DG in HM, together accounting for more than 80% of the total DG. In terms of triglyceride (TG) composition, even though 1,3-dioleoyl-2-palmitoyl triglyceride (OPO) has been added to it, the content of TG(16:0/18:1/18:1) in IFE, whose maximum level was (6.70 ± 0.19)%, was significantly lower than that in HM, (7.92 ± 0.58)% (P < 0.05). In addition, the content of TG(16:1/17:2/22:6) in IFP, whose minimum level was (3.68 ± 0.67)%, was significantly higher than that in HM (0.02 ± 0.01)% (P < 0.05), indicating that the major existing form of C22:6 in IFP was different from that in HM. Although IFP was close to human milk in the composition of major fatty acids, the existing form of fatty acids in IFP was obviously different from that in HM.

In this study, the volatile components of sweet fermented oat produced by natural and inoculated fermentation were analyzed and compared by headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that totally 62 and 65 volatile compounds were detected in the samples from natural and inoculated fermentation, respectively, mainly including acids, esters, alcohols, aldehydes and ketones, heterocyclic compounds and hydrocarbons. Using principal component analysis (PCA), esters, alcohols and heterocycles were found to be positive volatile components. The major volatile aroma components of the second sample were alcohols (58.31%), esters (20.70%) and acids (16.75%), while the major volatile aroma components of the first sample were acids (61.94%), esters (18.89%) and alcohols (13.58%). The contents of esters, alcohols, and heterocycles in inoculated fermentation were significantly higher than those in natural fermentation, whilst the opposite was true for acids. The results of this study should be helpful to determine the feasibility of applying inoculated fermentation for producing sweet fermented oat and should provide a theoretical basis for the quality evaluation and production of sweet fermented oat in the future.

In this study, the key factors causing the quality difference between Zhangping Shuixian tea (Shuixianwangzi?and Shuixiangongzhu) manufactured in different seasons (spring and autumn) were explored by sensory evaluation and biochemical analyses combined with multivariate analysis. The results showed that Shuixianwangzi tea was mellow with strong astringency in taste and had a sweet aroma with osmanthus fragrance. Shuixiangongzhu tea had a mellow and brisk taste and a clean aroma with orchid fragrance. Caffeine, tea polyphenols, and thearubigins were the characteristic non-volatile components to discriminate the differences in their tastes. 3-Carene, cis-3-hexenyl acetate, 1-hexanol, α-pinene, and D-limonene were the characteristic volatile components to discriminate the differences in their aromas. The results of this study will provide a theoretical basis for objective and accurate discrimination of different flavor types of Zhangping Shuixian tea.

A method for the determination of the contents and composition of total nucleotides in breast milk and cow milk by high performance liquid chromatography (HPLC) was established. The total nucleotides detected included free nucleotides, free nucleosides, nucleoside polymers and nucleoside adducts. The nucleosides in breast milk were released by enzymatic hydrolysis, purified by polyacrylamide gel (Affi-Gel 601) as a solid phase extraction medium, detected by reverse-phase-high performance liquid chromatography (RP-HPLC) and quantified by an internal standard method. The results were calculated as nucleotides. According to the characteristics of breast milk, a high-temperature inactivation step was introduced into sample pretreatment before the detection of nucleotides in breast milk. The proposed method was systematically validated. The results showed that this method had good linearity with a correlation coefficient (r2) higher than 0.999. The limit of detection (LOD) and the limit of quantification (LOQ) for all nucleotides in breast milk were 0.18–0.45 and 0.60–1.51 mg/L, respectively. The recoveries of total nucleotides in breast milk samples spiked at three concentration levels ranged from 99% to 108%, with relative standard deviations (RSDs) 0.8%–7.8% for six replicate determinations in three consecutive days, suggesting good accuracy and precision. The HPLC method was used to evaluate the composition and contents of total nucleotides in breast milk and five types of commercial cow milk in order to verify its applicability. The sensitivity, accuracy, and precision of this method can meet the requirements for the determination of natural nucleotides in breast milk and cow milk. This study should provide a more scientific and accurate method for the determination of nucleotides in massive samples of breast milk and cow milk in the future.

The aroma compounds of peaches from three different flesh types: “Xiacui” with stony hard, “Xiahui 6” with hard-melting, “Huijingmilu” with soft-melting during postharvest storage at 20 ℃ were analyzed by headspace solid-phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) and electronic nose technology. The results showed that 45 aroma components were identified in the three cultivars, mainly including aldehydes, alcohols, esters, ketones, lactones, terpenes and hydrocarbon compounds. The types and contents of aroma substances in peaches significantly changed during postharvest storage. Totally 40, 27 and 17 aroma substances were respectively detected during the storage of “Xiacui”, “Xiahui 6” and “Hujingmilu” peaches. The total content of aroma substances decreased for all cultivars with increasing storage time. The results of principal component analysis (PCA) showed that electronic nose could significantly distinguish peaches at different storage times. Load analysis (LOA) results showed that sensors W1S, W5C, W3C, W1C, W1W and W2W were the most effective in distinguishing peaches at different storage times. Therefore, HS-SPME-GC-MS combined with electronic nose could accurately evaluate changes in the aroma quality of peaches during storage.

In this work, two tandem solid phase extraction (SPE) methods (Extrelut-PRS-C18 and PRS-C18 SPE columns), MCX SPE column extraction and dispersive SPE (quick, easy, cheap, effective, rugged, and safe (QuEChERS)) were used to extract 16 heterocyclic amines in meat products for analysis by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the four methods were comprehensively compared in terms of analytical figures of merit and cost. The results showed that the recoveries, precision, limits of detection (LOD) and limits of quantification (LOQ) for the 16 HAs were significantly different among the methods. The QuEChERS method was superior to the other methods in terms of recovery and precision. The LOD and LOQ of MCX SPE column extraction and QuEChERS were better than those of the other methods. Both MCX and QuEChERS extraction methods showed lower cost and were more time-saving. In summary, the QuEChERS method can allow accurate detection of HAs in meat products and has the potential for wide application.

In order to evaluate the risk of furazolidone residue in turbot (Scophthalmus maximus) under low-dose exposure to furazolidone in the aquaculture environment and to predict the distribution of furazolidone residue in aquatic products scientifically, the fish were fed on a diet supplemented with furazolidone at concentrations of 0.5, 1.5 and 5.0 mg/kg for 30 days at (16 ± 2) ℃ in this study. During this period, the residue of the furazolidone metabolite, 3-amino-2-oxazolidinone (AOZ) in turbot was determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The relationship between the concentration of furazolidone added to the feed and AOZ residue, steady-state enrichment time, tissue distribution characteristics and bioaccumulation factor (BCF) were determined, and a discriminant model was established to predict the concentration of furazolidone in the feed. The results showed that there was a positive correlation between AOZ residue in turbot and furazolidone concentration in the feed. At 0.5, 1.5 and 5.0 mg/kg furazolidone concentrations, the time required for AOZ to reach steady-state enrichment in muscle and skin was 15, 15 and 25 days, respectively. The distribution of AOZ in different tissues was similar, and the level of AOZ residue followed the decreasing order: liver > kidney > spleen > gill > skin > muscle. The BCF of furazolidone in turbot when added at low concentration to the feed was higher than at high concentration. When the concentration of furazolidone in the feed was greater than or equal to 0.68 mg/kg, the AOZ residue in the muscle of turbot was greater than or equal to 1.0 μg/kg after continuous feeding for 30 days. When the concentration of furazolidone in the feed was greater than or equal to 0.46 mg/kg, the same result was observed for the skin. The trace residue of furazolidone in turbot may be related to the polluted farming environment. Through model prediction and scientific monitoring, the risk of pollution caused by the farming process can be reduced to guarantee the safety of aquatic products for consumption.

A colorimetric method for the rapid detection of hypoxanthine (Hx) content in fish was established using copper nanoclusters (CuNCs) with high intrinsic peroxidase-like activity. Cysteine-stabilized CuNCs were prepared by a simple stirring method at room temperature. The morphology, elemental composition, surface functional groups and luminescence property of Cys-CuNCs were characterized by transmission electron microscopy (TEM), photoelectron spectroscopy, Fourier transform infrared spectrometer (FTIR) spectroscopy and fluorescence spectroscopy, respectively. Ultraviolet-visible spectroscopic experiments showed that Cys-CuNCs sensitively catalyzed the oxidation of 3,3’,5,5’-tetramethylbenzidine by H2O2, allowing for the colorimetric sensing of H2O2 content. On this basis, a colorimetric assay for Hx determination was established by generating H2O2 under the catalysis of xanthine oxidase. Under the optimal conditions as follows: incubation temperature 30 ℃ and incubation time 1 h, good linearity between Hx concentration in the range of 4–100 μmol/L and absorbance was observed and the detection of limit was 1.2 μmol/L. Finally, the proposed method was applied to the determination of Hx content in fish, and the freshness of fish was judged by establishing its correlation with total volatile basic nitrogen (TVB-N) content.

Silica-immobilized ionic liquid modified magnetic nanoparticles (Fe3O4@SiO2@IL) were prepared and applied as a peroxidase mimic for the detection of H2O2. The results showed that Fe3O4@SiO2@IL had higher catalytic activity than horseradish peroxidase (HRP), and could catalyze the coupling of H2O2 with the peroxidase substrate 3,3’,5,5’-tetramethyl aniline (TMB) to form a blue product. On the basis of this phenomenon, a colorimetric method for H2O2 detection was developed, with a linear range of 4–100 μmol/L and a detection limit of 0.698 μmol/L. The method was also available to sensitively and selectively detect glucose, with a linear range of 8–200 μmol/L and a detection limit of 2.39 μmol/L. The recoveries for this method when applied to detect H2O2 in milk samples ranged from 94.0% to 107.8%, with relative standard deviation (RSD) values of 2.24%–3.12%, showing high accuracy and precision. Therefore, Fe3O4@SiO2@IL nanomaterials with peroxidase mimic activity can be a promising candidate for application in clinical diagnosis, pharmaceutical, food and other fields.

An analytical method for the determination of the total arsenic (As) concentration of edible fungi using hydride generation-microwave plasma-atomic emission spectroscopy (MP-AES) was established. After wet digestion of edible fungi samples, arsenic (V) was reduced to arsenic (III) using a pre-reducing solution (containing 50 g/L thiourea and 10 g/L potassium iodide). As (III) was transformed into gaseous arsenic trihydride using a multimode sample introduction system and detected by HG-MP-AES. The spectral line of As at 188.979 nm was selected as the analytical line to avoid spectral overlap interference. The background interference was corrected by using the fast linear interference correction model. The limit of detection for As was determined to be 0.93 μg/L. Total As levels of the different varieties of edible fungi samples tested ranged from 0.087 to 0.482 mg/kg. The results of this method for total arsenic in the standard reference material GBW10022 (garlic powder) were consistent with the certified value, indicating that this method is accurate. To sum up, MP-AES proved to be a fast, accurate and reliable high-throughput method for the determination of total arsenic in edible fungi samples. MP-AES used nitrogen generated from air with a nitrogen generator as the plasma working gas, reducing the cost.

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) protocol coupled to gas chromatography-mass spectrometry (GC-MS) method for the determination of eight volatile N-nitrosamines in Chinese bacon was established and applied to evaluate the risk of dietary exposure to N-nitrosamines in commercial samples. The samples were extracted with acetonitrile in an ultrasonic bath, and after freezing treatment, the extract was purified using primary secondary amine (PSA) and condensed by nitrogen blowing in water bath to a trace volume. Then, the N-nitrosamines were separated on a polar capillary column, detected in the selected ion monitoring (SIM) mode and quantified by the external standard method. The results showed that the calibration curves exhibited good linearity for the eight volatile N-nitrosamines (R2 > 0.997) with matrix effects between 0.86 and 0.98. The limits of detection (LODs) and the limits of quantification (LOQs) ranged from 0.05 to 0.14 μg/kg and from 0.15 to 0.47 μg/kg, respectively. The average recoveries at three spiked levels (0.3, 1.0 and 3.0 μg/kg) were between 71.3% and 94.1% with relative standard deviations (n = 6) in the range of 0.4%–11.2%. Only one of the 12 representative samples sold on the market showed a N-nitrosodiethylamine (NDEA) content exceeding the national standard limit (3.06 μg/kg), while the rest were lower than the limits for individual and total volatile N-nitrosamine (3.0 and 10.0 μg/kg, respectively). This method showed the advantages of good purification effect, low cost, high sensitivity and good accuracy, and was suitable for the detection of the eight volatile N-nitrosamines in Chinese bacon. And the risk level of dietary exposure to N-nitrosamines in Chinese bacon was relatively low overall.

Nanoporous gold (NPG), with high electrocatalytic activity for the oxidation of ascorbic acid was prepared by acid corrosion and used to construct a NPG-modified glassy carbon electrode (GCE) as an electrochemical sensor to detect ascorbic acid in drinks. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to determine that citrate buffer at pH 4.0 was the best buffer for activating the electrocatalytic activity of NPG. Under optimized conditions, ascorbic acid was detected by DPV. The results showed a good linear relationship between the concentration of ascorbic acid in the range of 6.652 8 to 160 μg/mL and the peak current density. The electrode proved to be easy to prepare and have high sensitivity, good stability and strong interference resistance, indicating great potential for rapid detection of ascorbic acids in drinks.

This study aimed to establish a polymerase chain reaction (PCR)-based method for accurately and quickly identifying yellow cattle-, buffalo- and yak-derived components. The species-specific primers and probes were developed and used to establish simplex, duplex and triplex real-time PCR methods for the simultaneous identification of the three kinds of bovines. The ability of each primer/probe set to detect target species was determined using a DNA dilution panel. In the simplex real-time PCR, the limits of detection (LODs) for the three bovines were all 0.025 ng/μL; in the duplex real-time PCR assay, the sensitivity for detection of yellow cattle was reduced to 0.1 ng/μL, while those of the buffalo and yak were still at 0.025 ng/μL. Under optimal condition with the ratio of three primer/probe sets at 3:3:2= yellow cattle:buffalo:yak, the triplex real-time PCR assay showed LOD of 0.1 ng/μL for both yellow cattle and buffalo, but 0.025 ng/μL for yak. However, these detection abilities in the duplex and triplex real-time PCR were all based on that the tested sample DNA, which was a mixture of the target species DNAs mixed in an equal proportion. But if the proportions of the three bovines were quite different, especially if there was great difference between yellow cattle and yak (9:1), the species with the lowest proportion probably would be undetectable. Therefore, triplex real-time PCR is an effective way to simultaneously detect the three animal-derived components in samples of whole meat, while simplex real-time PCR is recommended for use on ground meat.

The background value and traceability of endogenous benzoic acid in soy sauce were investigated and analyzed. All traced samples were collected from producers of soy sauce, and benzoic acid was detected in all samples of crude soy sauce and zero-additive soy sauce at levels ranging from 7.52 to 17.09 mg/kg with an average of 12.72 mg/kg. The average contents of benzoic acid in pre-sale and final zero-additive soy sauce were 13.15 and 13.31 mg/kg, respectively. Benzoic acid content and the δ13C value of benzoic acid were followed up during soy sauce production, showing that benzoic acid in soy sauce came mainly from the raw materials. As a result of the degradation of phenylalanine, the content of benzoic acid increased during the shelf life, with an average annual increase rate of 14.26% and an annual increment of 1.80 mg/kg. Significant differences existed in the content of benzoic acid in regular and zero-additive soy sauce from different manufacturers. The average content of benzoic acid in zero-additive soy sauce was 13.38 mg/kg, which was consistent with the tracing results during the production process. The?results from this study will provide basic data for the regulation of the zero-additive soy sauce market.

Liquid chromatography-triple quadrupole tandem mass spectrometry (LC-MS/MS) was used to detect the migration of the primary aromatic amines 2,4-diaminotoluene (2,4-TDA) and 4,4’-diaminodiphenylmethane (4,4’-MDA) from polyamide/polypropylene (PA/CPP) retort pouches to acidic food simulants (4% acetic acid solution). In addition, different heat treatments and sterilization methods (pasteurization, steaming, boiling, high-temperature sterilization, and ultraviolet sterilization) were compared for their effects on the migration of both substances. The results showed that the limits of detection and the limits of quantifications for the migration of 2,4-TDA and 4,4’-MDA were both lower than 0.02 and 0.05 μg/kg, respectively, which meet the requirements of European Union standard for the limit of primary aromatic amines (PAAs). This study found that pasteurization, steaming, boiling, and high-temperature sterilization significantly promoted the migration of 2,4-TDA and 4,4’-MDA from PA/CPP retort pouches to 4% acetic acid solution in a temperature-dependent fashion (P < 0.05), which was not significantly affected by ultraviolet (UV) sterilization. According to the migration data, UV irradiation and pasteurization were relatively safe methods for the sterilization of foods packaged in retort pouches. In addition, steaming was a safer method than boiling for heating retort pouched foods. After 15 min of high-temperature sterilization at 121 ℃, the migration amounts of 4,4’-MDA from two commercial brands of PA/CPP retort pouches were 2.733 and 3.113 μg/kg, respectively, which were higher than the EU’s revision of the migration limit for individual PAAs (0.002 mg/kg) and could cause potential food safety risks. Hence, the impact of different heat treatment methods on the migration of PAAs from PA/CPP retort pouches and the safety of retort pouched foods is worthy of attention.

An immunochromatographic assay (FMICA) using fluorescent microsphere-labeled antibody as the signal probe was developed for rapid quantitative detection of nitrofuran metabolite residues in aquatic products. The limits of detection (LOD) for NPAHD, NPAMOZ, NPAOZ, and NPSEM were 0.004, 0.01, 0.008 and 0.009 μg/L, and the linear ranges were 0.005–5, 0.01–10, 0.01–10, and 0.01–10 μg/L, respectively. The detection process took 10 min. The assay had good specificity. The spiked samples were detected by FMICA after derivatization treatment, and the recoveries of the four analytes ranged from 75.88% to 104.81%, with variation coefficients of less than 15%. Therefore, FMICA proved to be simple, fast, and low-cost and could be suitable for rapid quantitative detection of nitrofuran metabolites in aquatic products.

A fluorescence sensing system based on the nucleic acid dye Genefinder and aptamer was constructed for the detection of ochratoxin A (OTA) in this study. A double-stranded structure was formed by binding the OTA aptamer to its complementary strand. Binding of Genefinder to double-stranded DNA (dsDNA) generated a strong fluorescent signal. In the presence of OTA, the aptamer bound to it to form a quadruplex structure, melting the double strands and leading to a decrease of the fluorescence intensity of Genefinder. The results showed that the linear range of the sensing system was 50 pg/L–300 ng/L, and the detection limit was 50 pg/L. The sensing system had a high selectivity for OTA and could be widely applied as a simple and fast method.

An analytical method using QuEChERS (quick, easy, cheap, effective, rugged and safe) pretreatment combined with high performance liquid chromatography-quadrupole-time of flight mass spectrometry (HPLC-Q-TOF-MS) was developed for the rapid non-targeted screening of unknown pesticide residues in litchi flower, hive and honey. The samples were extracted with acetonitrile-water, cleaned up with a mixture of anhydrous magnesium sulfate, N-propyl ethylene diamine (PSA) and octadecyl (C18) sorbent, separated on an Xbridge BEH C18 column by gradient elution using a mobile phase consisting of formic acid in water and acetonitrile, and detected using both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) under the positive and negative ion modes. Screening for unknown compounds suspected of being pesticides were carried out through database matching with the exact mass, isotopic distribution, secondary fragmentation information and retention time of the characteristic ions of the target compounds, and in the targeted MS/MS mode, the selected compounds were confirmed based on the ion fragment information at each collision energy. The analytes were quantified by using matrix-matched standard solutions. The results showed that eight pesticides (including azoxystrobin, pyraclostrobin and its metabolite BF 500-3, difenoconazole, carbendazim, chlorpyrifos, diflubenzuron and chlorbenzuron) were screened out. The calibration curves for these analyes had good linearity in the range of 1–1 000 μg/L with correlation coefficients (r2) above 0.99. The limits of detection were 0.03–0.50 μg/kg and the limits of quantification were 0.4–0.8 μg/kg. The average spiked recoveries of the pesticides in litchi flower, hive and honey samples were 80%–96% with relative standard deviations (RSDs) of 1.2%–6.1%. The developed method is quick, easy, sensitive and suitable for the rapid screening and identification of pesticide residues in litchi flower, hive and honey.

The factors affecting the content of vomitoxin (deoxynivalenol, DON), in wheat were analyzed, and the contamination characteristics and distribution difference of vomitoxin in different types of wheat grains and different grain parts were evaluated. The results showed that disease infection, injury, the size of wheat grains, and the type of insect injury affected vomitoxin contamination. Vomitoxin content was weakly positively correlated the percentage of perfect grains, but significantly positively correlated with the percentage of gibberella-damaged grains. Significant differences in the level of vomitoxin contamination were found among different grain types and different parts of the same cultivar; the content of vomitoxin was significantly higher in gibberella-damaged grains than in the uninfected ones, in broken grains than in the intact ones, in small grains than that in the large ones, and in the embryo than that in the endosperm. The content of vomitoxin in the kernel surface accounted for 35.2%–52.1% of the total. More serious vomitoxin contamination was observed in the part closer to the outer layer of the endosperm, while less serious vomitoxin contamination appeared in the part closer to the center of the kernel center. After wheat flouring, the content of vomitoxin was higher in the bran but lower in the flour. Vomitoxin contamination in wheat can be effectively reduced by grading, sorting, washing and milling.