In this paper, the effect of Lactobacillus rhamnosus fermentation on the physicochemical and processing properties of corn four and corn dough was investigated. We also examined the effect on the quality of steamed sponge cake. The results showed that L. rhamnosus fermentation reduced the water-binding capacity of corn flour by 11.52%, and increased the gelatinization enthalpy change by 23.68%, the total gas production of corn dough by 42.93%, and the gas retention coefficient by 5.88%. Compared to the control, the 48 h fermented corn flour increased loss modulus (G”) and storage modulus (G’), obviously improved elasticity, and decreased loss tangent value (tanδ); the specific volume of the resulting steamed sponge cake was 2.63, increasing by 11.55% compared to the control, and the size of bubbles in it increased by 58.85%, showing good swelling performance. L. rhamnosus fermentation increased the hardness, and improved the springiness and chewiness of steamed sponge cake. These results can provide experimental data for the application of probiotics in the quality improvement of gluten-free staple food.

The contents of total polyphenols and total and individual flavonoids in celery juice and two celery extracts (which were adsorbed onto polyamide resin and then eluted with 40% or 60% ethanol) before and after simulated oral, gastric and intestinal digestion were measured and compared. The protective effect of the digests against oxidative stress in cells was studied. Besides, the correlation between polyphenol and flavonoid contents and the protection against oxidative stress was evaluated. The results showed that the contents of total polyphenols, total flavonoids, luteolin-7-O-glucose-2-O-selenoside, luteoloside, apigenin and 3-methoxy apigenin were increased by 6.82, 6.03, 26.18, 8.62, 22.17 and 9.07 times for the extract eluted with 40% ethanol; 6.54, 6.50, 12.46, 5.21, 17.60 and 4.09 times for the extract eluted with 60% ethanol; 29.26, 26.10, 5.16, 2.63, 8.58, and 4.67 times for celery juice, respectively after in vitro simulated digestion. The antioxidative stress ability of celery juice and both extracts increased first and then decreased during the simulated digestion. Alcohol extraction and normal dietary intake had no significant effect on the in vitro digestion of celery flavonoids, and there was a positive correlation between total phenol and flavonoid contents and antioxidative stress ability.

The effect of heat treatment on the surface hydrophobicity (H0) of 11S glycinin was researched and its secondary structure was analyzed by Raman spectroscopy before and after heat treatment. As the heat treatment time increased (80 ℃), H0 was increased and α-helix was transformed to β-turn and random coil structures. At both 90 and 100 ℃, H0 increased first and then decreased, while it changed faster and more significantly at 100 ℃, and α-helix and β-sheet were transformed to β-turn and random coil structures. Moreover, the tyrosine and tryptophan residues in the protein molecule were exposed after heat treatment. At the same time, the vibration mode of intermolecular disulfide bond in 11S glycinin was changed, transforming the disulfide bond from g-g-g configuration to t-g-t configuration, which may lead to an increase in protein surface hydrophobicity.

The aim of this work was to understand the effect of different kinds of vegetable oils (peanut oil, linseed oil and sunflower seed oil) added in different proportions (0%, 10%, 20%, 30% and 40%) on the formation of N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) in an in vitro model system. We also examined the effect of nitrosation conditions (substrate concentration, pH, reaction temperature and reaction time) on the production of NDMA, NDEA and N-nitrosopyrrolidine (NPYR) in the presence of 20% peanut oil using the oil-free aqueous phase system as a control. The results showed that all three kinds of oils promoted the formation of NDMA and NDEA. The production of N-nitrosamines was higher in the presence of peanut oil and linseed oil than in presence of sunflower seed oil, and it increased with the increase in oil concentration. Nitrite concentration had greater effect on the formation of NDMA and NDEA than the formation of NPYR. The production of NDMA and NDEA decreased with increasing pH from 5.4 to 7.0, while pH had little effect on the formation of NPYR. The formation of N-nitrosamines increased significantly with increasing temperature above 80 ℃. The formation of NDMA and NDEA showed an increasing first and then slightly decreasing trend with reaction time, whereas reaction time had little effect on the formation of NPYR. The formation of NDMA, NDEA and NPYR was significantly higher in the emulsion system containing lipids than in the control group, and the production of three N-nitrosamines was in the decreasing order of NDMA > NDEA > NPYR under the same reaction condition. All of these results suggested that higher temperature, lower pH, higher concentrations of sodium nitrite and the existence of a certain amount of oil can promote the synthesis of NDMA and NDEA, and that temperature can be considered as the principal factor influencing the formation of NPYR. Therefore these factors should be controlled during in the production of meat products to minimize the level of N-nitrosamines.

Soy protein isolate was used to prepare protein emulsion gels due to its emulsifying and gelling properties, and the gels were used for co-delivery of vitamin E and sodium isoascorbate. The effects of pectin addition on gel structures and the stability of vitamins were investigated. The results indicated that emulsion droplet size was increased with increasing pectin content, and protein-pectin mixtures pre-heated at higher temperature resulted in bigger droplet size. Emulsion gelation was induced by glucono-δ-lactone (GDL), and the gelling time and gel strength were both significantly affected by pectin content. Textural analysis revealed that pectin content and pre-heating temperature did not affect gel hardness, and springiness was firstly increased and then decreased with pectin content. When mixed vitamins were incorporated within emulsion gels, the stability of vitamins was decreased with pectin content, and sodium isoascorbate was degraded at higher rates than vitamin E. It was concluded that the structural properties of the emulsion gels could be modulated by the addition of pectin, and that the stability of vitamins was associated with gel structures.

This study was undertaken to evaluate the effect of five different decoloring agents (attapulgite, diatomite, activated carbon, zeolite and activated clay) on the volatile flavor compounds and fatty acid composition of crude fish oil was investigated. Gas chromatography (GC) and headspace solid-phase microetraction coupled with gas chromatography-mass spectrometry (GC-MS) were used to determine the volatile flavor compounds and fatty acid composition of decolorized fish oils. The main flavor components were identified by sensory thresholds. The results showed that the relative contents of nonanal, hexanal, and 2-nonyl ketone, which contributed to the fishy odor and the fatty and waxy aroma, significantly decreased after decolorization, thereby significantly improving the flavor of fish oil. The relative content of saturated fatty acids declined, whereas the relative content of unsaturated fatty acids increased. Acid value and peroxide value rather than iodine value and saponification value changed significantly. The decoloring effects of attapulgite and activated clay were good, while diatomite, activated carbon and zeolite had poor deodorizing effect. The results from the present study will be helpful for improving the decoloring process and the flavor of fish oil in the future.

This study investigated the effect of adding oxidized tannic acid (OTA) to oil-in-water (O/W) emulsions prepared with porcine plasma protein hydrolysates (PPPH) as an emulsifier on improving their physical stability during storage. The changes in emulsion droplet size, zeta potential, flocculation index, creaming index and protein partition coefficient during storage were determined, and the microstructure was visualized via confocal laser scanning microscopy (CLSM). The results showed that compared with the control group, D[3,2], D[4,3], flocculation index and coagulation index were decreased significantly with the increase in OTA concentration (P < 0.05), whereas zeta potential value was obviously increased (P < 0.05), reaching its maximum when 1% OTA was added, during the period from 1 to 10 d of storage. Meanwhile, OTA slightly induced cross-linking of PPPH, significantly increasing their distribution at the emulsion interface (P < 0.05). The CLSM micrographs also revealed that the interfacial membrane in emulsions with the addition of 1% OTA was more compact and more massive than other groups. The results indicated that the addition of OTA significantly improved the physical stability of O/W emulsions containing PPPH during storage, which will lay a theoretical foundation for the application of OTA in food emulsions.

Starches were extracted from newly released Guihuai cultivars of Chinese yam and their properties were studied. It turned out that starch from Guihuai 7 showed lower peak viscosity, pasting temperature and setback value, whereas starch from Guihuai 8 had higher peak viscosity, shorter peak time and weaker thermal stability. Furthermore, both cultivars exhibited poor freeze-thaw stability, although their cohesiveness was good. They showed poor retrogradation properties after being left to stand for 2 h. Good solubility was observed in water bath at 60–90 ℃. The different cultivars of Chinese yam showed distinct differences in starch properties. This finding can provide useful guidance for deep processing and application of different cultivars of Chinese yam and also provide insights into the development of new cultivars suitable for processing.

Protein isolate (PEPI) was extracted from Pleurotus eryngii by alkali dissolution followed by acid precipitation and the major protein components were isolated by the Osborne method. Their physicochemical and functional properties were studied. Results showed that the protein content of P. eryngii was 17.57% (dry mass), and the mainly protein fraction was albumin (PEA), accounting for 81.12% of the total protein isolate. Both PEPI and PEA contained 18 amino acids with essential amino acids accounting for 40.80% and 40.51% of the total, respectively. The surface hydrophobicity of PEA (265.25) was significantly higher compared to that of PEPI (164.27) (P < 0.05), while the contents of total sulfhydryl group and disulfide bonds were lower, which were 61.53 and 10.39 μmol/g, respectively. The thermal denaturation temperature of PEA (100.98 ℃) was lower than that of PEPI (108.27 ℃) and water holding capacity (1.64 mL/g) and oil holding capacity (5.59 mL/g) were significantly lower than those of PEPI (3.58 and 8.36 mL/g) (P < 0.05). The solubility, foaming capacity, foam stability, emulsifying property and emulsion stability of PEPI and PEA showed similar trend with pH, and were the lowest at pI. Fourier transform infrared spectroscopy (FTIR) showed that the secondary structures of PEPI and PEA consisted mainly of β-sheet and β-turn. Scanning electron microscopy showed that PEPI possessed a honeycomb structure. Compared to PEA, PEPI exhibited better functional properties.

In order to study the genetic background of yeast strains used in the fermentation of Chinese rice wine, the HO gene from a Chinese rice wine yeast strain, Sacchromyces cerevisiae 11-1, was knocked out. Stable haploids of the opposite mating type (a and α) were obtained by culturing the yeast strain on McClary medium for 5?7 days at 25 ℃. A diploid yeast strain (Sc-11-1-HOΔ) with knockout of the whole HO gene was successfully obtained by population hybridization and was used to ferment Chinese rice wine. The results demonstrated that there was no distinct difference between wild Sc-11-1 and Sc-11-1-HOΔ and that this modified yeast could be used in industrial production. Our results from this study can provide useful information for future exploration of the genetic base and metabolic mechanism of Chinese rice wine yeast strains.

This study aimed to investigate the structure and diversity of microbial communities in traditional spontaneously fermented sticky bean bun dough samples collected from different households in Heilongjiang province by polymerase chain reaction-denaturing gradient gel electrophorese (PCR-DGGE). The results showed that the dominant bacterial species identified in the samples of sticky bean bun dough were Weissella cibaria, W. confuse, Leuconostoc mesenteroides, Lactobacillus reuteri and Lactococcus lactis as well as uncultured bacteria and the dominant yeast species were Candida zeylanoides, Pichia caribbica, Guehomyces pullulans and uncultured saccharomycete. The microbial community structure of sticky bean bun dough was related to its ingredients. The findings from this study can provide theoretical support for improving the quality of sticky bean bun, developing special starter cultures, and realizing large-scale automatic production of sticky bean bun.

The dextranase-encoding gene (dex) was amplified by reverse transcription PCR from the genome of Penicillium aculeatum F1001. The gene consisted of 1 866 base pairs and encoded a protein of 622 amino acid residues. According to the codon usage bias of Pichia pastoris, optimized gene (opt-dex) was obtained. The expression recombinant plasmids dex-pPICZαA and opt-dex-pPICZαA were constructed and then separately electro-transformed into P. pastoris X33 to form transformants. The dextranase-producing transformants were selected out using blue-dextran T-2000 specific plates and shake flask expression. The purified recombinant dextranase showed only one band about 65 kDa, as analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The recombinant dextranase reacted optimally at pH 5 and 35 ℃ and specifically cleaved α-1,6 glycosidic bonds. The shake-flask fermentation conditions of the recombinant strain were optimized as follows: temperature 25 ℃, initial pH 5.0, addition of 1% (V/V) methanol, 4 g/L Tween-80 and 5 g/L sorbitol at 24 h intervals, and 50 mL of medium contained in a 500-mL shake flask. Under the optimized conditions, the activity of dextranase was as high as 240.74 U/mL. In conclusion, this study indicates that P. pastoris X33 is suitable for heterologous expression of P. aculeatum dextranase and that the recombinant dextranase can be used as an alternative to the native dextranase in producing dextran for industrial application.

In the present work, high throughput de novo sequencing of the Morchella importuna transcriptome was carried out, and the annotated sequences were classified using gene ontology (GO), eukaryotic orthologous groups (KOG), and Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways. After assembly, a total of 14 637 unigenes were formed, 8 495 of which were annotated. By functional classification using GO and KOG, the annotated unigenes were divides into 58 and 25 categories, respectively, involved in many physiological and biochemical processes including synthesis and metabolism of biomolecules, respiration and energy metabolism and signal transduction. Furthermore, a large number of key genes involved in energy metabolism, the synthesis and hydrolysis of nutrients, the softening of texture, oxidation of polyphenols and browning were identified through analysis of the unigenes related to postharvest physiology. The data obtained in this study can provide important information for the understanding of the molecular mechanism of postharvest quality changes in Morchella importuna and for the development of new preservation technologies.

In this study, a thermophilic fungal strain (HBHF5) producing tannase was identified. Also, the enzymatic properties of tannase from strain HBHF5 were evaluated and transcriptomic analysis of its carbohydrate?active?enzymes (CAZymes) was carried out. We aimed to explore the potential of strain HBHF5 for use in the development of food enzyme preparations. Based on its morphology and ITS sequence alignment analysis, strain HBHF5 was identified as Aspergillus fumigatus. A. fumigatus HBHF5 did not produce tannase under solid-state fermentation (SSF), but it produced both?extracellular and intracellular tannase when cultured under submerged fermentation conditions. The extracellular enzyme was found to be dominant (94%) and its activity was as high as 136 U/mL. Tannase activity was optimal at pH 6.0 and 60 ℃. After treatment at 60 ℃ for 30 min, more than 90% of the initial activity was retained, and the residual activity was over 60% in the pH range of 5.0 to 9.0. The tannase activity was inhibited by some metal ions, such as Cu2+, Fe3+, Mn2+ and Zn2+. Transcriptomic analysis showed?that 239 CAZymes?genes including those encoding amylase, cellulase and pectinase were?expressed when wheat bran was used as the sole carbon source. Among these the most abundant was glycoside hydrolase, accounting for about 70% of the total CAZymes. It has been demonstrated that A. fumigatus HBHF5 is a good producer of tannase and has the potential to be used to develop food enzyme preparations.

Monascus produces many beneficial secondary metabolites including Monascus pigments (Mps), while some Monascus strains can produce citrinin (CIT), which arouses people’s concern about the safety of Monascus products. In this study, the contents of Mps and CIT in fermented rice with 22 Monascus strains (including 14 model strains) were analyzed by ultra performance liquid chromatography (UPLC) after being pretreated with a composite extractant. The results showed that of the 22 strains, 13 could produce both Mps and CIT, 4 could only produce CIT, while 5 produced neither Mps nor CIT. Monascus 3.4443 and 3.4384 possessed the highest yields of Mps and CIT, respectively. Principal component analysis (PCA) indicated that CIT was positively correlated to yellow and orange pigments but negatively correlated to red pigments from the Monascus pigments producers. The results from this study can provide valuable information for the systematic analysis of Monascus metabolites and the development of Monascus products with high Mps content.

In this study, we screened 9 secretory (Sec) pathway signal peptides for the production of recombinant hyperthermoacidophilic α-amylase PFA from Pyrococcus furiosus in Bacillus subtilis WB600. The signal peptide YfkN achieved the highest extracellular α-amylase activity. Then we used saturation mutagenesis of Ile3 and Gln4 of the signal peptide YfkN as a novel approach to improve the secretion of PFA. The culture supernatant of the recombinant strain contained the signal peptide I3G/Q4R and had remarkable α-amylase activity (up to 715 U/mL). The purified α-amylase PFA showed maximal activity at pH 5.0 and 100 ℃, and its half-life at 100 ℃ was about 13 h with or without 5 mmol/L Ca2+ added. To the best of our knowledge, we obtained higher yield of PFA in a food-grade host, which may benefit the industrial production and application of PFA.

Objective: To study the bacterial diversity of waxy corn during natural fermentation and the influence of lactic acid bacterial fermentation on processing properties of waxy corn meal. Methods: The V3–V4 variable region of bacterial 16S rDNA genes from naturally fermented waxy corn was sequenced using MiSeq platform and the bacterial diversity was evaluated. One dominant strain was screened out and identified. Additionally, the effects of pure strain and natural fermentations on the pasting and textural properties of waxy corn meal were compared as well. Results: Lactobacillus fermentum was identified as the dominant bacteria by morphological, physiological and biochemical characteristics and 16S rDNA gene sequence analysis. Pure fermentation significantly increased the peak viscosity, final viscosity and breakdown value and significantly reduced setback value; furthermore, steaming significantly increased hardness, adhesiveness, and chewiness, thereby improving the farinographic properties of waxy corn meal.

The chitinase-encoding gene of Pyrococcus furiosus was synthesized and the recombinant enzyme solubly expressed in Escherichia coli. Chitosan with low degree of deacetylation was hydrolyzed by this enzyme and the composition and structure of the resulting chitooligosaccharides were analyzed. Size exclusion high performance liquid chromatography (SE-HPLC) results showed that the relative molecular masses of the hydrolysis products ranged from 1 000 to 5 000. Matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis revealed that the hydrolysates contained chitooligosaccharides with a degree of polymerization of 2?9 and different degrees of deacetylation. Structural characterization by nuclear magnetic resonance (NMR) indicated that the reducing end of all oligosaccharide fractions was mainly composed of two successive N-acetylglucosamines. In summary, we have prepared chitooligosaccharides with low degree deacetylation having determined reducing end structure using recombinant chitinase from P. furiosus, which can lay the foundation for the study of the structural-activity relationship of chitooligosaccharides with complex structures.

The purpose of this study was to gain genomic insights into the proteolysis system and amino acid biosynthesis in Streptococcus thermophilus KLDS SM. Firstly, whole genome sequencing was performed using combination of Illumina Hiseq 2500 sequencing and Pacific Biosciences RSII sequencing and the circular genomic map was constructed; subsequently, in silico bioinformatics analysis was carried out with respect to extracellular proteinase, peptide transport system, intracellular peptidase and amino acid biosynthesis; finally, comparative genomics of amino acid biosynthesis between strain KLDS SM and 14 other S. thermophilus strains, all of which have had the whole genome sequenced, was performed. The results showed that the genome of S. thermophilus KLDS SM consisted of a circular chromosome (1 856 787 bp) with GC content of 39.08%. A total of 1 732 protein-encoding genes were predicted. S. thermophilus KLDS SM had a complete proteolytic system and could biosynthesize eight amino acids. Furthermore, comparative genomics analysis showed that the amino acid biosynthesis abilities of 15 strains were relatively conservative except for a large difference in histidine biosynthesis among different strains. The results of this study can provide a theoretical basis for better understanding of nitrogen metabolism in S. thermophilus KLDS SM and are of important significance to exploiting it as a starter culture.

To investigate the diversity and dynamics of microbial communities in hairtail from different oceans during chilled storage. high-throughput sequencing was used to analyze the microbial communities of hairtail samples from different oceans in southeast China. The results showed that there were great differences in the microbial community structures of fresh hairtail samples from different geographical regions. At the genus level, Psychrobacter, Thermus and Oceanisphaera were the dominant bacteria in the samples from Nantong. Meanwhile, a wide variety of bacterial genera were found in the samples from Zhoushan and the relative abundances of seven different genera were similar, about 10%. After being refrigerated for 6–8 days, Psychrobacter and Oceanisphaera became the dominant spoilage bacteria in the samples from both regions. The relative abundances of the two genera exceeded 89%. The microbial community diversity and microbial community structure changes during the refrigerated storage of hairtail showed potential food safety risks. The findings of this study can provide experimental data for food safety monitoring during refrigerated storage of hairtail and its preservation.

This study aimed to obtain the endolysin lys56 encoded by Staphylococcus aureus phage qdsa001. First of all, the characteristics (physicochemical properties, signal peptide, transmembrane helices and structure domains) of lys56 were predicted by several online software. Subsequently, the target protein was obtained by cloning and expression. For this purpose, the target gene was synthesized and inserted into a prokaryotic expression vector pET-30a to construct recombinant plasmid pET-30a-lys56, which was subsequently transformed into E. coli Rosetta (DE3). Ni-IDA affinity chromatography was applied to purify the recombinant protein. The results showed that lys56 had a relative molecular mass of 35.1 kDa without signal peptide or transmembrane domain and contained only one Ami_2 domain. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the recombinant protein was successfully expressed in the cell supernatant with a molecular mass of about 35 kDa, which was consistent with the expected size. Optimal expression of the endolysin lys56 was induced by 0.5 mmol/L isopropyl-β-D-thiogalactopyranoside (IPTG) overnight at 20 ℃.

A novel pathway for the biosynthesis of caffeine with xanthine as substrate has been found in microbes, which is an effective way to improve the efficiency of caffeine synthesis from xanthine produced from guanine catalyzed by guanine deaminase. This study aimed to clone the guanine deaminase gene and to construct a prokaryotic expression system to synthesize xanthine efficiently. The two guanine deaminase genes gud1 and egud were amplified from Saccharomyces cerevisiae and Escherichia coli by PCR, respectively. The target fragments were inserted into the pMAL-c5X vector and then the recombinant plasmid transformed into E. coli BL21(DE3) to induce protein expression. The expressed products were determined by high performance liquid chromatography (HPLC). Both the recombinant vectors pMAL-gud1 and pMAL-egud had the capability of synthesizing xanthine, and the efficiency of xanthine synthesis with GUD1 was higher as compared to EGUD. This study can enrich the theory of black tea processing technology and provide a theoretical foundation for constructing engineered strains that are capable of producing caffeine.

Objective: The bacteriocin-producing strain QF01, isolated from water kefir grains, was identified and the antibacterial activity of bacteriocin from the isolate was evaluated. The gene sequences encoding bacteriocin were analyzed as well. Methods: The antibacterial activity of bacteriocin was determined by the Oxford cup method. The bacteriocin-related genes were amplified by PCR, 16S rDNA analysis was used for bacterial identification and bacteriocin gene analysis was carried out by using online software (ProParam tool, TMHMM 2.0, InterProScan, SOPM and SWISS-MODEL). Results: Bacteriocin produced by strain QF01 demonstrated a strong inhibitory activity against Escherichia coli JM109. This strain was identified as Lactobacillus plantarum based on its 16S rDNA sequence. The four bacteriocin-encoding genes plnD, plnEF, plnV and plnR were found in Lactobacillus plantarum QF01. The plnV gene encoding product had a helical transmembrane structure with signal peptide characteristics at its N-terminal. In addition, each of the four gene encoding products contained α-helix, β-turn, extended chain and random coil structures, as predicted from the tertiary structure model. Conclusion: L. plantarum QF01 contains the bacteriocin-encoding genes plnD, plnEF, plnV and plnR, and has a strong inhibitory activity against E. coli.

Adopting bioinformatics software, this study aimed to predict the secondary and tertiary structure model of the A2 chain of 11S globulin G2 in order to locate the B cell epitopes. The results indicated that the conformational epitopes were mainly at the random coil areas and the probable linear epitopes may contain 37KPDNRIE43, 79PSYTNGP85, 114SQQRGRSQRP123, 52WNPNNK57, 196QQGGSQSQKGKQQE209, 241QGENEEED248, 267RKPQQEEDDDDEEEQ281, and 287TDKGC291. This prediction can be utilized to find out accurate peptides sequences for subsequent peptide preparation and immunization so as to develop a technique to detect soybean allergens for people allergic to soybean foods in China.

The gene encoding glutamate decarboxylase (GAD), a key enzyme for the biosynthesis of γ-aminobutyric acid (GABA), from GABA-producing Lactobacillus plantarum BC114 was amplified by using PCR. Bioinformatics analysis of this gene was performed. Then, the target gene?was?subcloned?into the expression vector pGEM-T-gad and the recombinant plasmids were transformed into competent Escherichia coli BL21 (DE3) for heterogeneous expression. Real-time reverse transcription PCR (RT-PCR), polyacrylamide gel electrophoresis (PAGE) and high performance liquid chromatography (HPLC) were used to measure the mRNA and protein expression of GAD and GABA production, respectively. Results showed that the size of the GAD gene from L. plantarum BC114, encoding 469 amino acids, was 1 410 bp. The predicted secondary structure of the GAD protein contained 32.2% α-helix, 11.5% β-sheet and 56.3% random coil. Meanwhile, the three dimensional structure?was also predicted by using homologous modeling method. The recombinant E. coli harboring the gad gene was obtained successfully. The highest expression level of the gad gene was achieved after induction for 6 h, while the maximum protein expression level appeared 2 h later and the highest production of GABA of 2 387 mg/L was also obtained at this time.

This study aimed to reveal the succession pattern of yeast populations during the fermentation of Luzhou-flavour liquor and its influence on the formation of flavor compounds. For this study, yeasts were isolated from fermented grains at different stages of fermentation, and the variations among different yeast species were analyzed by single-strand conformation polymorphism (SSCP). Furthermore, the sequences of the D1/D2 region of the 26S rRNA gene of 130 yeast strains were analyzed and identified, belonging to 9 genera and 15 species, Pichia fermentans, Naumovozyma castellii, Torulaspora delbrueckii, Saccharomyces cerevisiae, P. membranifaciens, Candida humilis, Kazachstania exigua, Saccharomycopsis fibuligera, Millerozyma farinosa, C. cabralensis, P. kudriavzevii, C. ethanolica, P. occidentalis, Zygosaccharomyces bailii and C. rugopelliculosa. In addition, we investigated the impact of yeast succession on the formation of selected flavor compounds. Our results lay a theoretical foundation for the study of functional microorganisms for traditional Chinese liquor.

The fungal community structure in Zhaguangjiao was analyzed by Miseq high throughput sequencing and the relative intensity of various taste attributes of Zhaguangjiao samples was determined using an electronic tongue. Furthermore, the correlation between the fungal diversity and taste quality of was evaluated. The results showed that Ascomycota was the most dominant fungal phyla with a relative abundance of 99.97%. Candida, Eurotium, Pichia, Fusarium, Galactomyces, Cladosporium, Guehomyces, and Debaryomyces each accounted for more than 1.0% of total sequences at the genus level, with a relative abundance of 56.63%, 10.12%, 11.19%, 2.67%, 2.48%, 2.21%, 1.50% and 1.01%, respectively. The results of Pearson correlation analysis indicated that there were positive correlations among the relative abundance of the dominant fungal genera and the defective indexes of taste quality. Thus, we can consider that the fungal microbiota played inactive roles in the taste quality formation of Zhaguangjiao.

In order to improve the activity of glutamate decarboxylase (GAD) of Bacillus megaterium, its encoding gene was molecularly modified by directed evolution. Mutants A5-3, E2-4 and E3-11 were screened out from more than 13 000 mutants by two rounds of error-prone PCR, whose specific activities were increased respectively by 157%, 115% and 97% and whose Kcat/Km ratio was also increased compared to the wild-type strain. The amino acid sequence of A5-3 showed two mutations, A55D and D451E. From the results of 3-dimensional simulations, the alanine to aspartate mutation at position 55 may provide H+ to the enzymatic reaction, thereby accelerating the reaction rate. In mutant E2-4, the leucine to glutamine mutation at position 34 may improve the thermal stability of the enzyme. As for mutant E3-11, the mutation of alanine 325 to serine was conducive to the formation of more hydrogen bonds inside the protein, increasing the flexibility of the site and facilitating the interaction between amino acid residues. The circular dichroism analysis showed that the mutants had similar three-dimensional structure to the wild-type strain. Compared to the wild-type enzyme, the mutant enzymes contained less α-helix but more random coil, indicating a slight decrease in rigidity and an increase in flexibility. This study indicates that directional evolution can effectively improve the glutamate decarboxylase activity of B. megaterium, which will lay the foundation for its industrial application.

A method for the separation of six monosaccharides was established by using high performance liquid chromatography (HPLC) with 1-phenyl-3-methyl-5-pyrazolone (PMP) pre-column derivatization. This method was applied to analyze the monosaccharide composition of polysaccharides isolated from 10 fruit samples of Lycium barbarum L. collected from different growing areas and 8 commercial samples obtained from different companies. With the merits of simplicity, high sensitivity and good repeatability, the HPLC method was suitable for the monosaccharide composition analysis and quality control of L. barbarum polysaccharides. Results showed that polysaccharides isolated in our laboratory were composed of mannose, rhamnose, galactose acid, glucose, galactose and arabinose at an average molar ratio of 1.00:1.38:0.63:92.37:1.18:3.55. Polysaccharide contents were determined to be within the normal range for 6 of the 8 commercial samples, while the remaining ones exceed the average. The commercial samples contained 2?3 times more glucose (in mole) than the laboratory prepared samples.

In order to study the effect of different drying methods on the umami taste components in different parts of the fruiting body of Suillus granulatus, the contents of non-volatile components in the mushroom samples after natural drying (ND), hot air drying (HAD), vacuum drying (VD) and vacuum freeze drying (FVD) were determined. The umami taste was evaluated by equivalent umami concentration and umami taste scores from an electronic tongue. The results suggested that among four drying methods, HAD provided the highest umami amino acid content (18.49 mg/g) and equivalent umami concentration (EUC) (113.18 g/100 g) in Suillus granulatus tube, the highest umami amino acid content in pileus (15.11 mg/g) and the highest EUC value in stipe (27.66 g/100 g) (P < 0.05). After vacuum drying, the soluble sugar content of Suillus granulatus tube (26.35%) and stipe (23.25%), the umami amino acid content (10.04 mg/g) of stipe, the umami nucleotide contents of tube, pileus and stipe (3.63, 3.06 and 2.84 mg/g) and the EUC value (39.51 g/100 g) of stipe were all significantly higher than those from the other three drying methods (P < 0.05). After vacuum freeze drying, the soluble sugar content (30.29%) and the contents of sweet amino acids (16.90 mg/g) and non-taste-active amino acids (16.23 mg/g) in Suillus granulatus pileus, the sweet amino acid content (16.74 mg/g) of stipe, and the bitter amino acid content (27.66 mg/g) of tube were all significantly higher than those from the other three drying methods (P < 0.05). After natural drying, the umami taste score (11.46) and bitter amino acid content (21.13 mg/g) of Suillus granulatus pileus and the contents of bitter amino acids (37.48 mg/g) and non-taste-active amino acids (17.44 mg/g) in stipe were all significantly higher than those from the other three drying methods (P < 0.05). Therefore, during the deep processing of S. granulatus into umami seasonings, hot air drying is suitable for S. granulatus tube and stipe, while vacuum drying is suitable for S. granulatus pileus.

In this paper, a high performance liquid chromatography coupled to ion trap mass spectrometry (HPLC-ITMS) method was used to identify synthetic ester-type and natural glyceride-type deep sea fish oils by lipid analysis. Lipids were separated by reversed phase HPLC on a C18 column using gradient elution with isopropyl alcohol and acetonitrile. Multistage fragmentation fingerprints were acquired by ion trap mass spectrometry under a data-dependent scan mode. The fingerprint information was identified from the total ion current spectra, mass spectra and tandem mass spectra. It was found that docose hexaenoie acid (DHA) and eicosapentaenoic acid (EPA) existed in ester-type fish oil as CH3CH2O-DHA and CH3CH2O-EPA, respectively, while both existed as triglycerides in glyceride-type fish oil. This method can accurately distinguish between ethyl ester-type and glyceride-type deep sea fish oils.

This work was conducted to compare the effects of ultra-high pressure (UHP) and heat treatments on the volatile components of Chinese seabuckthorn pulp. The pulp was subjected to UHP treatment at 500 MPa at 30 ℃ for 15 min or heat treatment at 90 ℃ for 40 min. The volatile components of the two treated samples were analyzed by headspace solid-phase micro-extraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that UHP treatment increased the amount of volatile components in seabuckthorn pulp by 61% as compared to heat treatment. A significant difference in the content of each group of volatile components was found between both treatments and the contents of alcohols and esters were significantly higher in the UHP-treated pulp than in the heat-treated pulp; the UHP-treated pulp contained more esters and acids, while there was no difference was observed for all other groups of volatile compounds. A total of 12 aroma compounds with odor activity value greater than 0.2 were identified in seabuckthorn pulp and of these, 10 including α-terpineol and ethyl hexanoate were more abundant in the UHP-treated pulp than in the heat-treated pulp while nonanal and 3-methyl butyric acid were significantly lower. To sum up, UHP treatment significantly improved the volatile composition of Chinese seabuckthorn pulp, which was closely related to promoting the release of substrates and activating glycosidase and esterase for the breakdown of bound volatile compounds.

In this study, head-space solid phase microextraction coupled to gas chromatography-mass spectrometry (HS-SPME-GC-MS) ws applied to analyze the main volatile flavor substances of Pixian soybean paste (PSP) sampled at five different fermentation stages from stable fermentation (six months) to the end (five years), and the obtained data were analyzed by principal component analysis (PCA). The results revealed that over 140 volatile flavor substances were detected in all PSP samples, mainly including ethyl acetate (18.39%), 4-ethyl gualacol (10.58%), phenethyl alcohol (7.64%), alcohol (7.16%) and phenylacetaldehyde (6.59%). The relative contents of aldehydes, esters, hydrocarbons and heterocyclic compounds increased with fermentation time, while the relative contents of alcohols, phenols and ketones decreased. The change of volatile aroma compounds was far greater during the early maturation stage than during the late maturation stage and it was very slow after 3 years of post-fermentation and did not significantly change subsequently.

In this study, the fermentation of kelp (Laminaria japonica) by yeast was carried out to deodorize it. Fermentation conditions were optimized using response surface methodology based on a three-variable, three-level experimental design. The responses were sensory score, pH value, color deference and chlorophyll content. The optimal fermentation conditions were determined as 0.17% inoculums size, 28 ℃ and 100 min. Under these conditions, higher sensory score of 74.6 points and higher total chlorophyll (a + b) content of 2.23 mg/kg were obtained. By monolithic material sorptive extraction coupled with gas chromatography and mass spectrometry (MMSE-GC-MS), a total of 43 volatile compounds, belonging to seven chemical groups, were detected in unfermented and fermented kelp, 11 of which were identified as odor-active compounds with odor activity value (OAV ≥ 1). Compared with unfermented kelp, the number of volatile compounds in fermented kelp decreased from 43 to 23, the total concentration of volatiles from 287.65 to 151.92 ng/g, and summated OAV value from 91.75 to 55.28. The efficiency of deodrization was 39.75%. The findings of this study can provide experimental data for improving kelp processing technologies.

In this study, a new process was developed for the preparation of anthocyanidins from blueberries using combination of liquid-liquid extraction and macroporous resin adsorption chromatography. Crude blueberry anthocyanins were obtained using ethyl acetate as the extraction solvent and anthocyanins were isolated from the crude extract by column chromatography on Amberlite XAD-7HP. After acid hydrolysis and concentration of the anthocyanins, the removal of acid and sugar was carried out by solid-phase extraction with C18, yielding 0.2% pure anthocyanidin mixture. The mixture was further fractionated into four high purity anthocyanidin monomers by semi-preparative high performance liquid chromatography (HPLC), including delphinidin (98.2% purity), cyanidin (96.3%), petunidin (92.6%) and malvidin (90.5%). The developed procedures are expected to provide technical and theoretical support for the preparative-scale separation of anthocyanidin monomers and the evaluation of their functional activity.

Radish anthocyanins (RA) were purified by ultrafiltration and XAD-4 macroporous adsorption resin. PA was identified to consist mainly of anthocyanin diglucoside by Fourier transform infrared spectroscopy (FT-IR) and mass spectrometry (MS), and its solubility in 4 ℃ cold water and 65% ethanol were 46.43% and 63.07%, respectively. Then RA was modified with glucosaccharase and the effect of pH, enzyme-to-substrate ratio and reaction temperature on the modification efficiency was optimized by orthogonal array design method. FT-IR and MS analyses indicated that the glycosidic bond of RA was specifically hydrolyzed by glucosaccharase into anthocyanin monoglycosides. The solubility of the modified anthocyanins in cold water and 65% ethanol was improved by 115.38% and 58.55%, respectively compared to the native counterpart. Furthermore, the hydroxyl radical scavenging activity of the modified anthocyanins, as determined using bromopyrogallol red oxidation assay, was significantly higher than that of native anthocyanins, but was slightly lower than that of procyanidine B2. Cytotoxicity evaluation suggested that the modified anthocyanins at concentrations from 5 to 40 μmol/L significantly inhibited the cancer cell growth of MHCC97L cells for 24 to 72 h in a concentration-dependent manner.

Traditional tofu puffs have a high percentage of fat and become rigid upon frying at high temperature. To address this problem, this study developed and optimized a new low-temperature vacuum frying process. The results indicated that the optimum process parameters were frying time 7.5 min, oil temperature 95 ℃ and vacuum degree 0.085 MPa. The moisture content, oil content and sensory score of tofu puffs obtained under these conditions were 77.52%, 27.97% and 94 points, respectively. Texture properties and microstructures of tofu puffs produced using the new frying process were compared with those obtained using the traditional process. Texture profile analysis showed that the springiness and chewiness of low-temperature vacuum fried tofu puffs were those of traditional tofu puffs. Traditional tofu puffs had a more coarse surface with larger?aperture and lost more water as observed by scanning electron microscope. In conclusion, the optimized low-temperature vacuum frying process can provide experimental guidance for the tofu industry and other related industries.

MLM-type (medium-long-medium carbon chain) structured lipids were synthesized by the reaction between lauric acid (C12:0) and refined soybean oil using Lipozyme RM IM lipase as a catalyst. The effects of molar ratio of between soybean oil and lauric acid, reaction temperature, reaction time and lipase dosage on the insertion rate of lauric acid were studied. The physicochemical properties of the MLM-type structured lipids prepared under optimized reaction conditions were determined. The optimal conditions for the synthesis of MLM-type structured lipids were as follows: molar ratio of soybean oil to lauric acid 6:1, reaction temperature was 45 ℃, reaction time was 24 h, and enzyme/substrate ratio 13%. Under these conditions, the insertion rate of lauric acid was 29.26%. The iodine value (97.38 g/100 g) and viscosity (70.39 cP) of the structurzed lipids were lower than those of soybean oil, and the saponification value (calculated as KOH equivalent) (229.58 mg/g), crystallization starting temperature (4.89 ℃) and melting starting temperature (?19.87 ℃) were significantly higher than those of soybean oil (P < 0.05), while no significant different (P > 0.05) in smoke point (231.24 ℃) was found. The MLM-type structured lipids synthesized in this study had higher nutritional value than soybean oil and could be developed as anti-obesity and lipid-reducing high-quality oils.

A nutritious animal protein-derived peptide beverage was prepared from an enzymatic hydrolysis of duck liver protein with white sugar and pectin added. Optimization of the major factors (ingredients) affecting the stability of the beverage was optimized using one-factor-at-a-time method and response surface methodology. It was found that incorporation of 2.0% duck liver peptide, 8% white sugar and 0.09% pectin gave a product with the highest stability (stability coefficient 99.1%). Amino acid composition analysis indicated that the peptide was rich in amino acids and had high nutritional value. After autoclaving, E. coli, mold and pathogens were not detected for 30 days. Sensory evaluation showed that the beverage was uniform and stabile. The results of antioxidant assays showed that the IC50 values of the beverage for 2,2’-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radical scavenging and ferrous iron chelating were 0.035 and 0.101 mg/mL, respectively. The results indicated that the peptide beverage had good antioxidant activity and stability. This study can provide experimental evidence for deep processing and high-value utilization of meat processing by-products.

A method for the simultaneous identification and quantification of dinotefuran and its metabolites 1-methyl-3-(tetrahydro-3-furylmethyl) guanidium?dihydrogen (DN) and 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) in vegetables (cucumber, tomato, potato, and cabbage) was developed using quick polar pesticides (QuPPe) extraction procedure combined with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The analytes were separated on a UPLC BEH-C18 column, detected in the positive ion mode (ESI+) using multiple reaction monitoring (MRM), and quantified by an external standard method. The proposed method showed good linearity in the range of 1.25–500 μg/L with regression coefficients of higher than 0.991. The limits of detection (LODs) ranged between 0.04 and 0.66 μg/L, and the limits of quantification (LOQs) were between 0.13 and 2.20 μg/L. The average recoveries of the analytes from spiked samples of cucumber, tomato, potato, and cabbage (the lowest spiked concentration level was 10 μg/kg) were in the range of 72.0%–109.1% with good precisions (relative standard deviation, RSD = 1.4%–12.8%). The majority of the analytes exhibited moderate or strong matrix effects. Results suggested that the method is simple, accurate, efficient and useful for rapid screening and quantitative analysis of dinotefuran and its metabolites in vegetables.

The goal of this study was to evaluate the accumulation levels and safety of heavy metals in cold water fish in Xinjiang. The concentrations of Pb, Cd, Cr, Hg, As and Ni in different organs and tissues of Coregonus autumnalis from the Sayram Lake were measured by atomic absorption spectrometry (AAS) and atomic fluorescence spectrometry (AFS) after microwave digestion, and the associations of heavy metal distribution profiles with body length and body mass were also examined. The single factor pollution index and the target hazard quotient were used to evaluate the degree of pollution and the safety of dietary intake of heavy metals through fish consumption. The results showed that the concentrations of heavy metals in C. autumnalis was tissue specific, and the concentrations of different heavy metals in each organ or tissue were different. The contents of Cd and As were the highest in intestinal and pancreatic tissues and lowest in muscle, while Pb content was the highest in skin. The levels of all three heavy metals were lower than the national standard limit (Pb < 0.5 mg/kg, Cd < 0.1 mg/kg, As < 0.1 mg/kg). Correlation analysis showed that there were significant correlations between the concentrations of all heavy metals except for Ni and Cr in some tissues and biological parameters such as body mass and length of C. autumnalis (P < 0.05). Heavy metal pollution evaluation and health risk assessment showed that all tissues and organs except muscle were polluted by heavy metals at different levels. Consumption of C. autumnalis from the Sayram Lake posed no obvious health risks and showed good safety.

In order to explore the feasibility of two-dimensional correlation synchronous spectra to select feature variables for meat freshness, visible/near infrared reflectance spectral information and total volatile basic nitrogen (TVB-N) content of 58 pork samples stored for 1–15 days were obtained. Then TVB-N content was employed as “external disturbance” and 10 representative spectra were selected for continuum removal. Seven spectral subregions were chosen according to the spectral difference and used for two-dimensional correlation analysis. By analyzing the synchronization spectra and the autocorrelation spectra, sensitive variables, which were closely related to TVB-N content, were obtained. Finally, using the selected variables, support vector machine (SVM) models for discrimination of pork freshness were established based on the original, standard normal variate preprocessed and normalized spectra, respectively. The results showed that 17 characteristic wavelengths, which accounted for only 1.61% of the total variables, were extracted by two-dimensional correlation spectral analysis, and that the overall accuracy rates of the SVM models were 94.83%, 98.28% and 98.28% respectively, indicating that the models performed well. Hence two-dimensional correlation analysis can be used to screen out the characteristic variables related to meat freshness. The research will be helpful for analyzing the change of spectral characteristics during meat spoilage and also provide new insights into variables selection in near infrared spectroscopy analysis.

A high performance liquid chromatographic (HPLC) with ultrasonic-assisted two-step enzymatic pretreatment for the determination of the starch content in meat products was developed. After pretreatment, the sample was separated on a C18 column (4.6 mm × 250 mm, 5 μm), using acetonitrile-20 mmol/L ammonium acetate (22:78, V/V) as mobile phase at a flow rate of 1.0 mL/min, and detected by an ultraviolet detector at a wavelength of 245 nm. The calibration curve was linear in the range of 5–50 mg/L with a correlation coefficient (r) of 0.999. The average recoveries of spiked hydrolysate were between 88.0% and 96.6% with relative standard deviations (RSDs) of less than 5% (n = 6). The limit of detection (LOD) was 0.4 μg/mL, and the limit of quantitation (LOQ) of the method was 0.16% by using α-amylase and amyloglucosidase. With the advantages of high repeatability and recovery over the national standard methods, this method is suitable for the determination of starch in meat products.

A new and sensitive method was developed for the determination of casein phosphopeptides (CPPs) in infant formulas by isotope dilution ultra-high performance liquid chromatography-triple-quadrupole tandem mass spectrometry (UPLC-TQ-MS/MS) under the multiple reaction monitoring (MRM) mode. The sample pretreatment procedure involved the addition of isotope-labeled signature peptide as an internal standard, followed by acid precipitation to remove casein from the sample. The signature peptide was chosen and identified from CPPs with Q Exactive Orbitrap based on Proteome Discoverer protein software searching. CPPs were separated on an ACQUITY UPLC BEH 300 C18 column. The content of CPPs in infant formulas was calculated based on the content of the signature peptide in CPPs and in sample. The results of method validation showed that a good linearity with R2 > 0.999 was achieved within the range from 10 to 150 mg/100 g. Satisfactory recovery (96.2%–100.2%) and inter-day reproducibility (5.3%–7.8%) were obtained at three spiked levels in blank infant formula matrices. The limit of quantification (LOQ) of the reported method was 1 mg/100 g for infant formula. This method can be suitable for the determination of the content of CPPs in infant formula.

A rapid method was established for detecting 14 mycotoxins (aflatoxin B1, aflatoxin B2, aflatoxin G1, aflatoxin G2, aflatoxin M1, ochratoxin A, citrinin, T-2 toxin, sterigmatocystin, fumonisin B1, fumonisin B2, zearalenone, deoxynivalenol, and penicillic acid) in liquid milk by solid-phase extraction coupled with ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Samples were defatted and extracted with 0.1% formic acid acetonitrile and the extract was cleaned up with Oasis PRiME HLB solid-phase extraction column. The analytes were separated on HSS T3 column (2.1 mm × 100 mm, 1.8 μm) with a mobile phase composed of 0.1% formic acid and acetonitrile using gradient elution. Detection was carried out by tandem mass spectrometry using positive ionization in the multiple-reaction monitoring (MRM) mode. An external standard method was applied for quantification. Results showed that the limits of quantitation (LOQs) of 14 mycotoxins in matrices were between 0.5 and 5 μg/kg. Average recoveries at 3 different spiked levels were 67.7%–112.7% with relative standard deviation (RSD) of 0.43%–7.28%. With the advantages of rapidity, high purification efficiency, low matrix interference and accurate and reliable results, the method is useful for the analysis of mycotoxins in liquid milk.

Ultra performance liquid chromatography-quadrupole linear ion trap mass spectrometry (QTRAP-UPLC-MS/MS) was employed to determine several amino acids and their isomers formed upon irradiation of seafood and the effect of irradiation dose (0.5–20 kGy) on the contents of m-tyrosine and o-tyrosine as irradiation markers in different seafood products was studied. Also, this study investigated the effect of storage conditions and processing methods on the specificity and stability of m-tyrosine and o-tyrosine as well as on the detection of irradiation seafood. Our results showed that phenylalanine could be converted to p-tyrosine, m-tyrosine and o-tyrosine by irradiation without microorganism or enzyme, which was linearly related to irradiation dose. Furthermore, the irradiation dose and moisture content were closely related to the production of m-tyrosine and o-tyrosine, which had good stability at ?20 ℃. Different storage conditions and processing methods had certain effects on the contents of m-tyrosine and o-tyrosine in irradiated seafood; however, the amounts of extracted m-tyrosine and o-tyrosine were sufficient for identification of irradiated seafood. The QTRAP-UPLC-MS/MS method with m-tyrosine and o-tyrosine as markers could precisely identify irradiated seafood with a dose as low as 0.5 kGy, and provide the basis for food safety monitoring.

This study investigated the influence of different sample pretreatments: enhanced matrix removal-lipid (EMR-L) for lipid, Oasis PRiME hydrophile lipophilic balance (HLB) and liquid-liquid extraction (LLE) on the assay of 16 quinolone residues in porcine tissues by ultra-high performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (UPLC-TQ-MS/MS) or quadrupole-time-of-flight tandem mass spectrometry (Q-TOF/MS). The target compounds were quantified by the matrix-matched calibration curve. Good linearity was observed for all analytes in the range of 1.0–100.0 μg/L. The recoveries using the EMR-L and Oasis PRiME HLB methods at spiked concentration levels (5, 10 and 20?μg/kg) were 71.7%–106.9% and 70.7%–118.3% with relative standard deviations of 0.2%–16.8% and 0.1%–17.8%, respectively; the limits of quantification of the two methods were 0.13–0.56 and 0.27–1.36 μg/kg and the limits of detection were 0.04–0.23 and 0.08–0.41 μg/kg, respectively. All these figures of merit met the requirements for the determination of quinolones. In order to avoid false positive results, a suitable sample pretreatment method should be chosen for different matrix samples. The two pretreatment methods used in this study, thanks to their ease of operation, high sensitivity and good repeatability, could be suitable for the qualitative and quantitative analysis of multiple veterinary drug residues in porcine tissues.

An ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for the determination of 3 microcystins (MCs) in aquatic products. The samples were extracted with methanol-water (8:2, V/V) and the extract was then cleaned up by multi-walled carbon nanotubes (MWCNTs). The target analytes were detected by UPLC-MS/MS using positive electrospray ionization (ESI+) in the multiple reaction monitoring (MRM) mode. Different MWCNTs were investigated for their suitability as sorbents for dispersive solid phase extraction (DSPE) and the purification conditions were optimized. The efficiency of the optimized DSPE conditions was compared to that of solid phase extraction using HLB column. Both purification methods showed a good linearity (R2 ≥ 0.99) over the concentration range from 1 to 50 μg/L and their limits of quantification were in the range of 0.1–0.2 μg/kg. The average recoveries of three MCs at different spiked levels were 88.7%–95.5% with relative standard deviations (RSDs) equal to or lower than 4.2%. This DSPE method can be suitable for the rapid detection of trace microcystins in aquatic products.

A method for the simultaneous determination of six blood lipid regulating drugs (nicotinicacid, pravastatin sodium, fluvastatin sodium, mevastatin, lovastatin and simvastatin) illegally added to antilipemic functional foods by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established. The samples were extracted with methanol. The analytes were separated on a Waters Acquity BEH-C18 column with a mobile phase consisting of 0.1% aqueous formic acid solution and acetonitrile using gradient elution at a flow rate of 0.2 mL/min, detected by multiple reaction monitoring (MRM) with an electrospray ionization source in the positive ion mode, and quantified by the external standard method. Under the experimental conditions in this study, all analytes were separated well, and they were quantified accurately and rapidly within 4 min. The limits of detection of the method ranged from 4 and 39 μg/kg, and the recoveries for spiked samples were 80.2%–106.1%. Twenty batches of antilipemic functional foods were tested by the method and out of these, 3 were found to contain nicotinic acid and lovastatin. This method exhibited good linear relationships and it was fast, simple and highly accurate, and thus could be used for the simultaneous determination of the six drugs illegally added in antilipemic functional foods.