Objective To establish and optimize a method for the determination of perchlorate (ClO₄^-) migration in food contact plastic products by large volume injection-ion chromatography (IC). Methods Water, 3% acetic acid (m:V), 4% acetic acid (V:V), 10% ethanol (V:V), 20% ethanol (V:V), 50% ethanol (V:V), and 95% ethanol (V:V) were selected as food simulants, and the isocratic elution was performed with a mixture of 14 mmol/L anhydrous sodium carbonate and 20% acetonitrile (volume fraction) as mobile phases, with an injection volume of 800 μL and a flow rate of 1.0 mL/min. The separation was performed on a Metrosep A Supp 4 ion chromatography column (250 mm× 4.0 mm, 9.0 μm) and a Metrosep A Supp RP Guard guard column (50 mm×4.0 mm, 9.0 μm) at a column temperature of 30 ℃ with a conductivity detector for the determination and the quantification of the extract by the external standard method. Results The method validation results showed that the method was linear with the linear correlation coefficient of the standard working curve greater than 0.995. The limit of detection was 0.15 μg/kg, the limit of quantification was 0.50 μg/kg, and the recoveries were 83.2%~99.1%, and the precision was 2.7%~9.1% (n=6). Conclusion The method is reliable, convenient, sensitive, has good separation effects, and suitable for the determination of perchlorate migration in food contact plastic products.

Objective To compare the differences in spectral characteristics and monocyte immune effects for bacterial endotoxin from different sources. Methods Ultraviolet absorption spectrum and three-dimensional fluorescence spectrum were used to identify excipients (polyethylene glycol 8000 and α-lactose) and biological impurities (protein and nucleic acid) in 5 kinds of control standard endotoxin. Biological contamination was further confirmed by the detection of Toll-like receptors (TLRs) in HL-60 cells. The monocyte activation test was used to compare the release of the inflammatory cytokines interleukin 6 (IL-6), interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) caused by 5 kinds of endotoxins on HL-60 cells. Results As for control standard endotoxin, absorption peaks related to excipients were observed in ultraviolet absorption spectrum, while fluorescence peaks related to excipients and proteins were shown in three-dimensional fluorescence spectrum. The expression levels of TLRs of HL-60 cells indicated that protein contamination was more significant than nucleic acid contamination. All endotoxins induced improvement in cellular IL-6 and IL-1β gene relative expression levels and their protein mass concentrations in HL-60 cells. However, the TNF-α gene relative expression levels and its protein concentrations were not elevated. Endotoxins from the same or different bacterial strains had significant differences in their ability to induce inflammation under the same endotoxin activities. Conclusion Excipients and protein contamination of endotoxins are identified by spectral detection, while proteins and nucleic acids in biological impurity are confirmed by the TLRs assay of HL-60 cells. Molecular structure of endotoxins, as well as protein contamination influence the ability of endotoxins to induce the release of the inflammatory cytokines.

Objective To explore the browning prevention effects of radio frequency and heat shock treatment on honey peach during frozen storage. Methods Heat shock and radio frequency with different durations were used for pretreatment, and the changes in browning and quality were monitored over a 7 days frozen storage period. Results Compared with heat shock treatment, radio frequency treatment showed a smaller impact on the TSS/TA and pH of the peaches, and significantly reduced electrical conductivity (P<0.05), indicating that it could be better maintain the integrity of the peach cell membrane by radio frequency pretreatment. Based on the studies of key enzymes, substrates, and products related to browning, it showed a good inhibitory effect of radio frequency treatment on the activity of polyphenol oxidase, soluble quinones, and total phenols in frozen peaches, and which had a certain effect on maintaining catalase activity. This could reduce the degree of fruit browning and better resist the damage of reactive oxygen species to the peach fruit. A slight increase in malondialdehyde content was observed under higher temperature of radio frequency treatment, but there was no significant difference (P>0.05). Conclusion Radio frequency treatment has a good inhibitory effect on peach browning and can better maintain the physicochemical quality of the peaches.

Objective To explore the effects of nine steaming and nine processing methods on the characteristics, microstructure, and effective components of Polygonatum sibiricum, and provide relevant basis for the processing technology of Polygonatum sibiricum. Methods Jiuhuangjing was prepared using the nine steaming and nine preparation method, and its characteristics, microstructure, and active ingredients were evaluated as quality control indicators for evaluation. Results After six steaming and six processing, the appearance of Polygonatum sibiricum basically meets the requirements of the Chinese pharmacopoeia. The surface of Polygonatum sibiricum after nine steaming and nine processing was black, oily, and smooth, with a uniform and glossy color. The interior was black with red inside and black inside, with a honeycomb like structure. The structure of calcium oxalate was broken, the content of polysaccharides and the water-soluble components were reduced, and the alcohol soluble components were increased. This suggested that after nine steaming and nine processing, the irritants of Polygonatum sibiricum gradually decrease, the polysaccharides undergo hydrolysis, and gradually decompose into monosaccharides, and the taste changes from sour to sweet without a tingling sensation. Conclusion This experiment establishes a scoring standard for the characteristics of nine steamed and nine processed Polygonatum sibiricum, in order to provide a basis for the quality identification and construction of quality standards for nine steamed and nine processed Polygonatum sibiricum.

Objective To establish a method for simultaneous determination of 317 kinds of pesticide residues in pomelo flowers by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) coupled with QuEChERS extraction. Methods Pomelo flowers samples were extracted with acetonitrile and salted with extraction salt pack, cleaned up by ethylenediamine-N-propylsilane silica gel (PSA) and graphitized carbon blank (GCB), the analytes were separated on an ACQUITY UPLC HSS T3 column to achieve the separation within 30 min. The 317 kinds of pesticides were detected in electron spray ionization with positive ion mode and electron spray ionization with negative ion mode with multiple reaction monitoring (MRM) mode and quantified by matrix matching curve external standard method. Results The 317 kinds of pesticides in pomelo flowers showed good linearity with correlation coefficients (r) greater than 0.995 within the range of 2.0-200.0 µg/L, and the limits of quantification were 0.002-0.010 mg/kg, the average recoveries at 3 spiked levels were 74.3%-120.3%, and the relative standard deviations were 0.36%-10.00%. Conclusion The method is simple, rapid, accurate and sensitive, can meet the rapid detection requirements of 317 kinds of pesticides in pomelo flowers and provide reliable data support for further standardizing for edible safety evaluation of pomelo flowers.

Objective To investigate the inhibitory effects of tuna skin collagen oligo-peptide (TSCP) on melanin production and oxidative damage protection in Hacat cells. Methods Through investigated the effects of TSCP on melanin and tyrosinase production in B16-f10 cells, analyzed the antioxidant activity in B16-f10 cells, and assessed its protective effect against hydrogen peroxide (H₂O₂) induced oxidative damage in Hacat cells, the inhibitory mechanism of TSCP on melanin production and its protective mechanism against oxidative damage in Hacat cells were revealed. Results The experimental results showed that TSCP exhibits no significant cytotoxicity to B16-f10 cells at concentrations ranging from 0.01 to 1.00 mg/mL, and significantly inhibited tyrosinase activity and melanin production. At a concentration of 1.00 mg/mL, TSCP significantly reduced melanin content to 83.79%±4.31% (P<0.01) and tyrosinase activity to 78.14%±6.95% (P<0.001). TSCP also significantly reduced the levels of reactive oxygen species (ROS) in B16-f10 cells. At 1.00 mg/mL, the ROS levels decreased to 53.5%±4.4% of the control group (P<0.001), indicating potent antioxidant potential. Additionally, TSCP increased the activity of superoxide dismutase (SOD) to (16.62±0.62) U/mg prot (P<0.001) and reduced malondialdehyde (MDA) content to (0.352±0.051) U/mg prot (P<0.001). Glutathione peroxidase (GSH-Px) levels were also elevated, reaching (284.55±4.99) ng/mL at 1.0 mg/mL (P<0.01). In the Hacat cell model, TSCP similarly exhibited no significant toxicity and, in the H₂O₂-induced oxidative damage model, significantly improved cell viability and suppressed apoptosis. At 1.00 mg/mL, TSCP improved cell survival to 73.66%±5.48% (P<0.01), compared to the model group. Conclusion TSCP can inhibit melanin production, reduce oxidative stress, providing a foundation for its potential applications in skin whitening and antioxidant therapies.

Objective To study the suitability of different varieties of Dioscorea esculenta for vacuum frying. Methods Nineteen varieties of Dioscorea esculenta widely cultivated in China were taken as raw materials. Six quality indexes of fried Dioscorea esculenta chips, namely the yield rate, sensory score, breaking force, adhesiveness, color difference, oil content and flavor, were measured, and difference analysis was carried out. Correlation analysis, principal component analysis, stepwise regression analysis methods were applied to explore the model fitting degree and the significance of the regression model. K-means clustering analysis method was used to preliminarily divide the processing suitability of the 19 Dioscorea esculenta varieties. Results Differences were found in the shape, size and color of fried Dioscorea esculenta chips among the 19 Dioscorea esculenta varieties, and correlations existed among the indexes. Taking the yield rate of Dioscorea esculenta (X₁), color difference value L^* (X₂), sensory score (X₃), breaking force (X₄), adhesiveness (X₅) and oil content (X₆) as the initial independent variables, principal component analysis could be conducted and a quality evaluation model for fried Dioscorea esculenta chips was constructed, which was Y=1.02-3.37X₁-0.19X₂+0.16X₃+0.18X₄+3.01X₅+2.43X₆. Among the 19 varieties, Zhan Shu 12, Mian Zi 12, Bai Shu, Chuan Zi Shu No. 6 and 317 were suitable for making chips; Yu Shu 27, Xu Yu No. 31, Qian Zi Shu No. 1, Wan Shu No. 5, Xiang Shu 98, Yu Shu 17, Zi Yun Hong Shu, Yu Shu 198, Qian Shu No. 8, Shang Shu 19, Kao Shu, Yu Shu 9 and Long Shu 9 were basically suitable for making chips; while Tong Shu No. 2 was not suitable for making chips. Conclusion The research results can be referred to when the Dioscorea esculenta industry in China selects specific varieties for chip processing.

Objective To construct a method for rapid detection of chromium (VI) in drinking water on a paper-based microfluidic chip. Methods The paper chips were manufactured by directly drawing on filter paper with a modified gel pen filled with alkylketene dimmer solution and then dried. The chromium (VI) was detected on the paper chips. Parameters influencing the chromium (VI) determination were investigated, including concentration of sulfuric acid solution and diphenyl carbamide solution, reaction time, and temperature. Results In this study, the linear range of chromium detection was 0~0.20 mg/L, the detection limit was 0.0036 mg/L, and the recovery rate was 97.7%~109.0%. It had wide linear range, high sensitivity and good repeatability. Conclusion The method has the advantages of simple operation and the accurate detection result, does not require expensive and complex large instruments, and has adaptability to simultaneous detection of multiple samples and on-site real-time detection.

Objective To study the effects of ultraviolet pre-sterilization on the quality of fresh pork. Methods Different packaging conditions (bare packaging and fresh-keeping bag packaging), irradiation distance (6, 9 and 12 cm) and irradiation time [bare packaging (3, 5, 10 s), fresh-keeping bag packaging (6, 10, 14 s)] were set in this study. The feasibility of ultraviolet treatment to reduce the number of pork microorganisms and prolong the shelf life of pork was explored by measuring the total number of colonies, sensory evaluation, color difference, total volatile basic nitrogen (TVB-N) and thiobarbituric acid reactive substances (TBARS). Results The results showed that the best ultraviolet irradiation conditions for naked packaged fresh pork were 9 cm-10 s, and the best ultraviolet irradiation conditions for fresh-keeping bag packaged pork were 6 cm-14 s, which could reduce the initial microbial number of fresh pork by 0.44 logCFU/g and 0.61 logCFU/g, respectively, but had no significant effect on fat oxidation, sensory evaluation and color. Conclusion The ultraviolet pre-sterilization treatment can reduce the initial number of microorganisms in pork, slow down the increase of TVB-N value and lipid oxidation, and has no significant effect on the sensory quality and color of fresh meat. The shelf life of pork is prolonged by 3-4 d, which has potential application value in the field of pork preservation.

Objective To compare the changes in muscle nutritional components and quality indicators of Trionyx sinensis at different stages of ecological purification breeding. Methods Nutritional parameters such as morphological index and protein, fat, amino acid and fatty acid in muscle and skirt were measured during the 0th, 15th and 30th d of purification, and the nutritional and quality changes of Trionyx sinensis were compared with the textural and structural characteristics. Results With the extension of ecological purification breeding time, the crude fat of Trionyx sinensis showed a trend of rapid decline followed by a slight increase, while the crude protein showed a trend of initial increase followed by a decrease. The total amino acid content showed a decreasing trend. In the entire ecological purification breeding process, there were significant changesin the crude protein and crude fat content in the muscles of Trionyx sinensis (P<0.05), as well as in the moisture and ash content of their skirts. There were significant differences in the content of saturated fatty acids, monounsaturated fatty acids, and polyunsaturated fatty acids before and after purification (P<0.05), and the content of saturated fatty acids and polyunsaturated fatty acids increased at 15 days. Except for valine and proline, all other amino acids decreased, and there was a significant decrease in cysteine, lysine, glutamate, histidine, aspartic acid, glycine, and alanine in the purified muscles after 30 days compared to the untreated ones (P<0.05). In the whole texture mode, the hardness, adhesion and mastication of the muscle of Trionyx sinensis purified for 15 days were significantly improved (P<0.05) compared with that of the muscle before purification. Conclusion Compared with traditional pond aquaculture of Trionyx sinensis, the crude protein content, essential amino acids, and total umami amino acids are significantly increased, and the optimal purification time is 15 d. Ecological purification breeding can improve the quality of Trionyx sinensis and better meet the needs of consumers. It is a purification breeding method worth applying in production practice, which is conducive to increasing the supply of high-quality and cost-effective Trionyx sinensis and providing research data for improving the quality of high-quality aquatic products.