Salmonella exhibits a strong inducible acid tolerance response (ATR) under weak acid conditions, and can also induce high-risk strains that are highly toxic, acid resistant, and osmotic pressure resistant to aquatic products. However, the induction mechanism is not yet clear. Therefore, this study aims to simulate the slightly acidic, low-temperature, and high-protein environment during squid processing and storage. Through λRed gene knockout, exploring the effects of low-acid induction, long-term low-temperature storage, and two-component regulation on Salmonella ATR. In this study, we found the two-component system, PhoP/PhoQ and PmrA/PmrB in Salmonella regulates the amino acid metabolism system and improves bacterial acid tolerance by controlling arginine and lysine. Compared with the two indicators of total biogenic amine and diamine content, biogenic amine index and quality index were more suitable for evaluating the quality of aquatic products. The result showed that low-temperature treatment could inhibit Salmonella-induced ATR, which further explained the ATR mechanism from the amino acid metabolism.

This study used Aeromonas hydrophila infection and culture of tilapia (Oreochromis mossambicus) renal cells to analyze the time dependent expression of miR-23a in tilapia renal cells infected with A. hydrophila. The current results showed that the expression of miR-23a changed significantly at different time points of infection. Using RNAhybrid software to predict the target site of miR-23a and construct a plasmid, the binding ability of the target gene 3`-UTR to miR-23a was verified through dual luciferase reporter gene assay. We found that target genes were reverse regulated, and tbk1, glut1 were identified as miR-23a target genes. Expression of ldha, ldhba, pdha 1a and pdha 1b was suppressed after overexpression of miR-23a. These results indicated that miR-23a was involved in the regulation of the immune response in tilapia kidney cells after A. hydrophila infection. tbk1 and glut1 are the target genes of miR-23a that can affect the expression of downstream genes by targeting GLUT1. The above results provide important insights into the role of miR-23a in regulating the immune response in bony fish and further understanding of miRNA-mediated multiple target genes to regulate innate immunity in fish.

The creation of potentially carcinogenic heterocyclic amines (HAs) during high-temperature frying must be prevented with efficient inhibitors. In this paper, we discover that pan-frying cephalopods (squid, octopus, and cuttlefish) can significantly increase their moisture content, decrease shear force and hardness, and inhibit the formation of potential carcinogens called heterocyclic amines by applying Ultraviolet C-treated gallic acid (UVC-GA). The pH of the fried cephalopods is steady between 5.92 and 6.19 after UVC-GA treatment, which significantly improves the color change and meat tenderness of the products while lowering their loss rate. The synthesis of several types of heterocyclic amines is strongly inhibited by UVC-GA in various cephalopods, with a maximum inhibition rate of 54.89% for all heterocyclic amines. This work discusses the rationale for using UVC-GA to prevent potentially cancer-causing heterocyclic amines in cephalopod food and also offers technological support for expanding the UVC-GA's range of applications.

Background This study aimed to investigate the genetic molecular mechanism of body color differentiation and variation of red tilapia, selecting the main genes related to the variation and cultivating the pure and stable red tilapia variety. Results The effects of different temperature treatments on body color and survival of Guam red tilapia, pearl white red tilapia and Florida red tilapia were compared. Besides, comparative transcriptome analysis was used to screen the candidate genes linked to the skin color differentiation of pearl white red tilapia. Among them, the body color of Guam red tilapia changed when the water temperature dropped to 16 − 14 °C, and continued to drop to about 11 °C, it was discolored in a large area reaching above 90%. According to the differential analysis: Tyrosine Kinase STYK1, HSP70, HSP30 and Transcription factor Sp6 expressions were significantly increased in the low temperature group, while MC1R, Transcription factor (MafB, jun-D, AP-1, E2F5, ETV6, Sp9, Sp7, E2F1, Sp4) expressions were notably decreased. Conclusions In this study, the expressive quantity of tyrosine protein kinase in the low temperature group HLF7 was significantly higher than that in the normal temperature group HLF3, which indicated that the melanin synthesis ability was enhanced in the low temperature group HLF7. The result was consistent with the tendency of red tilapia to become darker as the temperature gradient decreased.

The predicted model of the sensory quality of refrigerated tilapia skin at 8 degrees C was constructed using near-infrared spectroscopy (NIRS) based on the princi-ple of sample packaging integrity. The characteristic spectral intervals were chosen from preprocessed spectral data using synergy interval partial least squares (siPLS), principal component analysis, and Jordan-Elman back propagation-artificial neural network (JENN) was used to build a prediction model for tilapia skin quality parameter. The results showed that the multiple scatter correction (MSC) + 2nd derivative was the best-preprocessed method, and the four characteristic spectral intervals were 680-740, 742-800, 980-1040, and 1150-1210 nm. Further, the cumulative contribution rate of the first three principal components was 99.15%. Additionally, the root mean square error of cross-validation set (RMSECV) of transfer function (tanh) of the model was 0.386, the determinant coefficient for prediction (R-p(2)) was 0.973, and the RMSECV and R-p(2) were 0.393 and 0.971 for unknown samples, respectively. The results showed that NIRS combined with JENN could allow rapid and accurate evaluation of tilapia skin quality in the range of 73.00-97.00 scores.

Fish skin gelatin is an important functional product used in food, medicine and other industries. However, the structure and function of gelatins extracted with different methods differ significantly, thus limiting its production and application. This study used dry-salting, wet-salting, pepsin, acid and heat methods to extract gelatins from the skins of tilapia, grass carp and sea perch. Then, their structural characteristics (micro- and ultra-structure, amyloid-like fibril, etc.) and functional properties (viscosity, emulsifying performance, antioxidant abilities, etc.) were analyzed, and interaction between gelatin components were also explored. According to the results, the gelatins extracted with dry-salting and wet-salting methods had better reticular structure, larger fiber length/height, and higher viscosity properties, emulsifying and antioxidant capacity. The gelatin extracted by applying heat has the highest gel strength, and the gelatin extracted using pepsin had better thermal stability, water absorption capacity, and fat absorption capacity. Further analysis of component interaction showed that 11 types of collagens detected in the gelatins might promote the conversion of collagen to gelatin through self-assembly ability. The co-assembly of different types of collagens enhanced the properties of gelatin. Decorin had a positive effect on gelatin network structure, but Metallopeptidase inhibited the formation of network structure. Different methods can produce personalized gelatin products according to specific needs. The mining of component interaction would reveal the mechanism of gelatin formation and promote the development of gelatin synthetic biology.

Fish skin gelatin is an important functional product in the food, cosmetics, and biomedicine industries, and establishing a green and effective fish skin gelatin extraction method is an effective way to obtain high-quality gelatin and improve its production efficiency. In this study, a trypsin method was used to extract the skin gelatin of sea perch, tilapia, and grass carp, and the microstructures of skin gelatin of these three fish species were analyzed, with such functional characteristics as thermal stability, gel strength, and emulsifying properties measured. The study results show that the skin gelatin of sea perch and tilapia obtained through the trypsin method has a relatively big molecular mass, a dense network structure, and a stable trihelix conformation. In addition, the skin gelatin of these three fish species has a relatively high β-turn content in the secondary structure, good gel strength, and water absorption properties. The compositions of the collagen-associated proteins in the skin gelatins of these three fish species extracted with the trypsin method are significantly different from each other, with positive effects of decorin and biglycan on the stability of the network structure of gelatin and a certain damaging effect of metalloendopeptidase on the network structure of gelatin. The skin gelatin of tilapia has high thermal stability and good emulsifying performance. Therefore, this gelatin type has bright application prospects in such fields as food processing, cosmetics, and drug development. In contrast, the skin gelatin of grass carp has poor functional properties. Therefore, there are significant differences among the structures and functions of skin gelatin extracted from different kinds of fish through the trypsin method. This finding has provided a useful reference for the production of customized fish gelatin according to demand.

Dry-salting, wet-salting, trypsin, pepsin, acid, and heat methods were used to extract the gelatin from a few saltwater (snakehead) and freshwater (shark) fish skins, and their structural and functional properties and components were then investigated. The results show that enzyme techniques produce fish skin gelatin with a robust triple-helix organization and a sponge-like mesh structure, exhibiting good water absorption(10.67%), fat binding(10.63%), and emulsification properties(89.37 m(2)/g). The gelatin fiber length and height of shark gelatin extracted by wet salt method were the highest with 617.77 +/- 44.04 nm and 17.30 +/- 1.45 nm, respectively. Shark skin gelatin produced via heat methods and blackfish skin produced via trypsin exhibits impressive thermal stability, its T-m value was 77.5 degrees C and 75.7 degrees C respectively. heatly extracted snakehead and shark gelatin has a high gel strength with 3.06 +/- 0.04 N and 3.14 +/- 0.04 N. A more in-depth component analysis demonstrates that blackfish skin and shark skin gelatins contain 14 and 9 different forms of collagen proteins, respectively, according to a more thorough component study. Different varieties of gelatin also have other extracellular matrix elements. Notably, trypsin-derived gelatin from shark and blackfish skin has been shown to include biglycan and member 3 (NESH)-binding protein b. The co-assembly of type II improved the gel strength and thermal stability of the gelatin and type XI collagen. Biglycan and decorin can promote the growth of dense network structures. These findings will significantly contribute to the customized applications of fish gelatin and the mechanistic clarification of synthetic biology.

Investigation of the influences of eight antioxidants on the quality indexes of squids, octopuses, and cuttlefishes to broaden their application field. Furthermore, this paper studies the composition of heterocyclic amines (HAs) and the inhibition effects of eight selected antioxidants using Ultra High-Performance Liquid Chromatography Mass Spectrometry System (UPLC-MS). The results show that ultraviolet C-treated gallic acid (UVC-GA) has the best effect on keeping moisture content, decreasing frying loss rate, reducing color alteration, and improving tenderness and texture. The eight antioxidants inhibit the formation of PhIP, 8-MeIQx, and Norharman significantly in squids. As for octopuses, adding the eight antioxidants depresses the formation of PhIP, 8-MeIQx, and 4,8-DiMeIQx remarkably. For cuttlefishes, the other seven antioxidants could significantly inhibit the formation of PhIP except for the GA treatment group (p < 0.05). Overall, the inhibition effect of UVC-GA is relatively the best in three oil-fried marine cephalopod species

Bacteria or viral outbreaks can cause tilapia hemorrhage, ensuring considerable volume of hemoglobin (Hb) into the tissue. However, the hemoglobin toxicity on tissue and high doses also effect on tissue this phenomena is still under consideration. Therefore, current study exploited Nile tilapia kidney (NTK) cells to deeply expose the toxic effect of Hb on NTK cells. Toxicity of Hb on NTK cells was determined in terms of cells growth, expression of iron metabolism and inflammation-related genes, consequently examined antioxidant-related enzymes genes expression, intracellular iron and reactive oxygen species (ROS) contents, and apoptosis-related genes expression. The results showed that Hb and heme significantly inhibited NTK cells growth and up-regulated iron metabolism-related genes expression in different degrees. The Hb and heme activated the expression of pro-inflammatory cytokines (TNF-α, tumor necrosis factor-α; IL-1β, interleukin 1β; IL-6, interleukin 6), the anti-inflammatory factor (IL-10, interleukin 10) and the chemotactic factors (IL-4, interleukin 4; IL-8, interleukin 8) through NF-κB pathway, meanwhile activated the expression of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). Moreover, the Hb significantly increased intracellular iron and ROS contents while the expression of apoptosis-related genes was significantly activated by both Hb and heme. Current investigation suggested that high oxidative activity of Hb could activate iron metabolism- and inflammation-related genes expression, and increase intracellular iron and ROS levels, lead to up-regulated the expression of apoptosis genes in NTK cells.

基于罗非鱼皮食品在24℃贮藏12 d,建立了检测活菌总数(TVC)的电子鼻(EN)-支持向量机模型(SVM).采用琼脂平板计数法测定TVC,运用主成分(PCA)分析对EN信号聚类,利用偏最小二乘法(PLS)建立描述EN信号响应与TVC相关性的模型,并对模型进行优化和验证.研究结果表明,训练模型和验证模型的相关系数分别U为0.94～0.98和0.88～0.90,SVR模型的检测有效性较好.说明EN结合SVM的方法可快速准确检测鱼皮食品的TVC,为实现TVC快速检测提供参考,为保障鱼皮食品食用安全提供技术支撑.

建立甲醇中酰胺醇类混合标准溶液的稳定性评定方法,使用液相色谱串联质谱法精确测定混合标准溶液中各标准物质浓度随储存条件及储存时间的变化.结果表明,制备的混合标准溶液均匀性良好,各标准物质F值均小于95％的置信水平下的理论临界值;酰胺醇类混合标准溶液热稳定性不好,在40℃存储条件下降解较明显,浓度越低降解率越高;配制浓度高的混合标准溶液,在运输过程中避光并采取冰袋或其他控温措施,更易于保持其稳定性;该混合标准溶液在4℃避光储存6个月,其浓度值基本保持稳定,6个月以后浓度值呈现下降趋势.该混合标准溶液可用于食品和环境的残留检测及相关分析方法的确认与评价,有效期为6个月.

[目的]研究不同投喂频率(2次/d、3次/d)和水平(即每日投喂量占试验鱼体重的比例,2％、4％、6％、8％、10％)对长吻鮠幼鱼消化酶和肝胰脏脂肪代谢酶活性的影响,为长吻鮠的人工养殖提供更健康的养殖模式.[方法]采用SPSS 17.0软件进行双因素方差分析后采用Duncan多重比较检验,显著水平为0.05.[结果](1)当每日投喂频率为3次、投喂水平为6％时,长吻鮠幼鱼消化酶中的肠道蛋白酶、肠道淀粉酶和胰蛋白酶的活性最高,显著高于每日投喂频率为2次、投喂水平为10％的试验组以及每日投喂频率为3次、投喂水平为2％和10％的试验组(P＜0.05).(2)当每日喂频率为3次、投喂水平为6％时,肝胰脏脂肪代谢酶中的肉毒碱脂酰转移酶(CACT)、乙酰辅酶A羧化酶(ACC)、脂蛋白酯酶(LPL)和肝脂酶(HL)的活性最高,显著高于每日投喂频率为2次、投喂水平为2％的试验组以及每日投喂频率为3次、投喂水平为8％和10％的试验组(P＜0.05).[结论]最适宜投喂频率和水平分别是3次/d和6％,更适合长吻鮠幼鱼的健康养殖.

We analyzed the effects of creatine monohydrate (CMH) and conjugated linoleic acid (CLA) on muscle fiber type, related genes, metabolic enzymes, and growth performance in tilapia (Oreochromis mossambicus). The addition of CMH and CLA in the basal feed significantly reduced the daily intake of tilapia, indicating that CMH and CLA had positive effects on improving the tilapia feed conversion rate. CMH up-regulated the relative mRNA expressions of MyHC I, IIa/IIb in the tilapia muscle. The activities of oxidases (SDH, MDH), AMPK, and the mRNA expression levels of PGC-1α, MEF2C, and GLUT4 were increased but those of MyHC IIx and LDH activity were decreased. CLA increased the proportion of oxidative muscle fibers in tilapia muscle while enhancing the activities of MDH, SDH, and AMPK and increasing mRNA expressions of PGC-1α and GLUT4. However, it decreased the proportion of glycolytic muscle fiber types and LDH activity. CMH and CLA could activate the AMPK activity in the muscle, further up-regulating the gene expression in the AMPK pathway, enhancing oxidative metabolic ability, and transforming the muscle fiber type. The study provides a strategy for improving the quality of future tilapia culture by regulating muscle fiber type transformation through CMH and CLA supplementation.