Electrochemical characteristics of heme proteins in hydroxyethylcellulose film

A stable film made from hydroxyethylcellulose (HEC) on pyrolytic graphite (PG) electrode was employed for incorporating hemoglobin (Hb), myoglobin (Mb) and horseradish peroxidase (HRP), and the electrochemical characteristics of the proteins were studied correspondingly. Experimental results revealed that HEC film could greatly accelerate electron transfer between the proteins and electrode, and the proteins showed a thin layer electrochemical behavior in the film. Moreover, all the proteins in the film exhibited good catalytic activity towards the reduction of hydrogen peroxide (H₂O₂) in the low H₂O₂ concentration range. In the high concentration range, H₂O₂ would exhibit toxicity effect on the proteins. The electrochemical properties and electrocatalytic abilities of the three heme proteins in HEC film have been compared, and the optimal conditions for H₂O₂ biosensor fabrication have been obtained.     

Recovery and utilization of effluents from meat processing industries

Production of wastes during the processing of meat products is not desirable because it significantly deteriorates the quality of the final product as well as causes some serious health threats if not properly disposed-off. The majority of the waste, in the meat industry is produced during slaughtering. The composition of waste generated by the meat industry depends on species of animals slaughtered. The waste material of the meat processing industry contains plentiful amount of organic compounds due to which its disposal is quite difficult. Efficient utilization of by-products has direct impact on the economy of the country and reduce environmental pollution. Edible meat by-products are claimed to have high nutritional value as compared to the lean meat. Organ meats can be used for human consumption, animal feed production and medicinal purposes after proper treatment and processing. This article provides information regarding the waste material generated by meat processing plants, its health impacts, nutritional status of meat by-products and their utilization.     

次氯酸钠对德尔卑沙门氏菌生物被膜的抑制作用及机制

目的：为控制德尔卑沙门氏菌（Salmonella Derby）在食品加工过程中的污染，研究不同体积分数次氯酸钠对S. Derby生物被膜的抑制作用及其机制。方法：采用结晶紫染色法和平板菌落计数法观察次氯酸钠对生物被膜的抑制和清除效果，进一步观察不同体积分数次氯酸钠作用下沙门氏菌泳动能力和生物被膜内细胞的代谢活性、胞外聚合物含量和微观形态的变化规律。结果：次氯酸钠的最小抑菌浓度（minimum inhibitory concentration，MIC）为0.08%（体积分数，下同），亚MIC（0.04%、0.02%、0.01%）的次氯酸钠可以抑制S. Derby生物被膜的形成，对成熟生物被膜也有一定的清除效果，且不同亚MIC次氯酸钠的作用效果差异显著（P＜0.05）；不同体积分数次氯酸钠处理能降低生物被膜内细胞代谢活性，抑制胞外多糖的合成，且不同体积分数次氯酸钠的作用效果差异显著（P＜0.05）。激光共聚焦扫描显微镜结果显示，与对照组相比，次氯酸钠处理使得生物被膜厚度减小、活菌数减少、死菌数增多、细菌由聚集状态变为分散状态。结论：不同体积分数次氯酸钠对S. Derby生物被膜的形成有明显的抑制作用，这一作用与干扰细菌生长、生物被膜内细胞代谢活性和胞外多糖的合成有关。     

Correlation between instrumental stress and oral processing property of chicken broiler breast under wooden breast myopathy

Wooden breast myopathy affects the quality of fresh and processed chicken breast muscle. The objective of this study was to construct a classification method by instrumental stress, and the effects of wooden breast myopathy on meat quality and oral processing property, and was to explore correlations between stress and oral processing parameters. The severity of wooden breast myopathy was highly correlated to fillet weight (R² = 0.740), thickness (R² = 0.826) and hardness (R² = 0.803) (P < 0.01). The 3D scatter model based on stress is robust and reliable to classify the fillets into four categories (normal, mild, moderate and severe wooden breast fillets), avoiding manual grading. Moisture, fat, collagen, pH, drip loss, cooking loss, thawing loss, purge loss, hardness, gumminess and chewiness significantly increased with the severity of wooden breast myopathy, whereas fat, ash and water/salt-soluble protein contents significantly decreased (P < 0.05). Shear force reached the maximum (36.32 N) when this myopathy was moderate. The myopathy led to an increase in masseter activity and the particle size of the bolus. Significantly higher correlations between stress, Dx(50) (R² = 0.790), Dx(90) (R² = 0.771) and D[4,3] (R² = 0.797) were found (P < 0.01). This study also showed that jaw movement and muscle activity could be used to understand the links between physical property and orally sensory property.     

Stability of antioxidant peptides from duck meat after post‐mortem ageing

The stability of antioxidant peptides from aged duck meat during processing and simulated gastrointestinal digestion was investigated. The antioxidant peptides preserved a high stability in the presence of diverse NaCl or upon various time heating. The antioxidant activities were strengthened by the addition of 4–8% glucose or by heating at 100 °C, whereas they were lost under alkaline conditions. During in vitro digestion, the antioxidant activities increased with pepsin treatment but then decreased following trypsin digestion. Pepsin hydrolysed peptides into short fragments and results in the increased exposure of internal hydrophobic amino acids. With further treatment by trypsin, peptides can be hydrolysed completely and more free amino acids were released, leading to the decline in surface hydrophobicity. These variations might be responsible for the change in antioxidant activity during in vitro digestion. The antioxidant peptides from aged duck with high stability can be used as functional food ingredients to improve human health.     

Influence of ultrasonic treatment on the structure and emulsifying properties of peanut protein isolate

Effects of ultrasonic treatment on emulsifying properties and structure of peanut protein isolate (PPI) were evaluated by analysis of particle size distribution, protein surface hydrophobicity, SDS-PAGE, circular dichroism spectra and environmental scanning electron microscopy. The emulsifying properties of the PPI were found to be improved by ultrasonic treatment. The mean particle size decreased from 474.7 nm to 255.8 nm while the molecular weight remained unaffected. The results of intrinsic fluorescence spectroscopy and surface hydrophobicity indicated that ultrasonic treatment induced tertiary structural changes of the proteins in PPI. Emulsifying activity index and emulsion stability index were found to be correlated fairly well with surface hydrophobicity (H₀) (r = 0.712 and r = 0.668, respectively).     

压力水平及氯化钠浓度对兔肌球蛋白凝胶保水性及其胶凝过程中理化特性和结构变化的影响

以含不同浓度的氯化钠(1.0%、1.5%、2.0%)的兔骨骼肌肌球蛋白为实验对象,在不同压力水平(100、200、300 MPa)下对其进行超高压处理(9 min,25 ℃)后加热制备凝胶。以未经高压处理的含2%氯化钠的蛋白作为对照组。根据凝胶保水性、水分分布、凝胶微观结构、蛋白在升温过程中的贮能模量、表面疏水性、活性巯基含量以及二级结构等指标的变化,研究压力水平及氯化钠浓度对经高压处理的肌球蛋白加热胶凝过程中的蛋白流变特性,二三级结构以及形成的热凝胶的水分特征的影响。结果显示:含1%氯化钠的兔肉肌球蛋白经100或200 MPa高压处理后,包埋的疏水基团和巯基在40~55 ℃间快速暴露,且蛋白中的α-螺旋结构的比例也显著下降(p<0.05)。其较高的热变性速率使蛋白分子得以充分解折叠与相互作用,最终形成的热凝胶的保水性,微观结构及贮能模量均优于其他处理组,该研究结果可为利用超高压技术生产低盐功能性肉制品提供理论依据。     

明胶对鸡肉糜3D打印成型稳定性的影响

采用流变扫描、凝胶强度、核磁共振、扫描电子显微镜等,探究明胶对鸡肉糜3D打印成型稳定性的影响。结果表明,不同明胶添加量（0%、2%、4%、6%、8%,以肉质量计）的鸡肉糜均表现出剪切稀化行为,具备3D打印可行性。明胶增强了体系的黏度和凝胶强度,提高了鸡肉糜3D打印成型稳定性,但过高的明胶添加量会影响物料的挤出,降低打印样品的形状精度。当明胶添加量为4%时,样品表现出良好的精度和成型稳定性,此时打印后形状塌陷率为2.46%。对添加4%明胶的3D打印样品进行蒸煮品质评价,发现3D打印会使样品的蒸煮损失增大,但质构特性得到适当改善。