Conformational changes induced by high-pressure homogenization inhibit myosin filament formation in low ionic strength solutions

Myofibrillar proteins (MPs) of chicken breast are generally insoluble in water. We have developed a new method whereby MPs are solubilized in water by applying high-pressure homogenization (HPH) thus potentially enabling greater utilization of meat in various products. To clarify the mechanism of solubilization of MPs by HPH, we investigated their conformation, solubility and filament forming behavior in low ionic strength solutions induced by 15,000 psi HPH (103 MPa). HPH induces unfolding of MPs which subsequently exposes sulfhydryl and hydrophobic groups to the surface. Our findings, determined by circular dichroism, ATR-FTIR, SDS-PAGE and LC-ESI-MS/MS analysis suggest that HPH leads to unraveling of helical structures and to formation of myosin oligomers through disulfide bond. Due to intermolecular electrostatic repulsion and physical barrier of disulfide bonds in the rod induced by HPH, we suggest that the altered myosin conformation in MPs inhibits filament formation, thus contributing to high solubility of MPs in water.     

Repurposing fish waste into gelatin as a potential alternative for mammalian sources: A review

Mammalian gelatin is extensively utilized in the food industry because of its physicochemical properties. However, its usage is restricted and essentially prohibited for religious people. Fish gelatin is a promising alternative with no religious and social restrictions. The desirable properties of fish gelatin can be significantly improved by various methods, such as the addition of active compounds, enzymes, and natural crosslinking agents (e.g., plant phenolics and genipin), and nonthermal physical treatments (e.g., ionizing radiation and high pressure). The aim of this study was to explore whether the properties of fish gelatin (gel strength, melting or gelling temperature, odor, viscosity, sensory properties, film-forming ability, etc.) could be improved to make it comparable to mammalian gelatin. The structure and properties of gelatins obtained from mammalian and fish sources are summarized. Moreover, the modification methods used to ameliorate the properties of fish gelatin, including rheological (gelling temperature from 13–19°C to 23–25°C), physicochemical (gel strengths from ∼200 to 250 g), and thermal properties (melting points from ∼25 to 30°C), are comprehensively discussed. The relevant literature reviewed and the technological advancements in the industry can propel the development of fish gelatin as a potential alternative to mammalian gelatin, thereby expanding its competitive market share with increasing utility.     

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).     

酱鸭强化高温风干成熟工艺优化

以麻鸭为试验原料,通过酱腌风干成熟制作风干酱鸭,分析加工过程中脂肪氧合酶（lipoxygenase,LOX）酶活、硫代巴比妥酸（thiobarbiturie acid reactive substance,TBARS）反应底物值和过氧化值（peroxide value,POV）,研究强化高温风干处理对酱鸭加工过程中脂质...     

Inhibitory effects of garlic and other spices on biogenic amine production in Myeolchi-jeot,Korean salted and fermented anchovy product

This study was carried out to reduce biogenic amine contents in Myeolchi-jeot, Korean salted and fermented anchovy (Engraulis japonicus). The effects of a variety of spices including ginger, garlic, green onion, red pepper, clove and cinnamon, on biogenic amine production were determined by HPLC. The greatest inhibitory effect on biogenic amine production was observed in the culture treated by garlic extract. In the culture, the contents of putrescine, cadaverine, histamine, tyramine and spermidine were reduced by up to 11.2%, 18.4%, 11.7%, 30.9% and 17.4%, respectively, compared to control. The other spice extracts tested showed less or no effect in reducing biogenic amine contents. In addition, the extract of garlic showed the highest antimicrobial activity against the amine producers tested. The extract of garlic at a concentration of 5% (weight basis) was finally applied to the ripening of Myeolchi-jeot in situ, and then overall production of biogenic amines in Myeolchi-jeot was found to be reduced by up to 8.7%, compared to control. Consequently, it is expected that the findings of this study might be helpful for enhancing the safety of Myeolchi-jeot.     

Gelation properties of goose liver protein recovered by isoelectric solubilisation/precipitation process

Isoelectric solubilisation/precipitation (ISP) process was applied to goose liver (GL) for protein extraction. The gelation properties of proteins extracted by acid processes (ACP, pH 2.0, 2.5 and 3.0) and alkaline processes (ALP, pH 11.0, 11.5 and 12.0) were estimated, where the unextracted ground GL was set as the control. Nearly 58.39~79.00% of GL proteins were recovered by ISP treatments. High molecular weight (100~250 kDa) proteins were found to be partially hydrolysed by ACP, while few changes in proteins occurred during ALP. As evidenced by rheological and textural measurements, ALP proteins formed gels with high elasticity and superior texture, whereas ACP proteins had inferior gelation properties. Moreover, ALP proteins were able to form a highly interconnected and homogeneous three‐dimensional microstructure. Predominantly, gels produced by 11.0 had optimal texture and the lowest cooking loss (P < 0.05). These results suggested that the ISP process (ALP) is a potential method to improve the economic value of GL.     

KCl部分替代NaCl腌制对干腌肉制品蛋白质水解和感官品质的影响

以猪后腿肉为原料,利用添加量20%～60%的KCl部分替代NaCl对原料肉块进行腌制,NaCl腌制为对照组,对干腌肉块的理化、蛋白水解和感官指标进行测定。结果表明：KCl替代NaCl比例在0～60%时,对产品蛋白水解指数、氨基氮、肽氮和丙氨酰胺肽酶活力均无显著影响;感官评定结果表明KCl替代比例不超过40%时,对产品的各项感官指标的影响均无显著差异（P＞0.05）;说明KCl替代NaCl最佳比例为40%,产品中NaCl含量降低至3.14%,且蛋白降解指标和风味不产生明显变化。     

顶空吹扫捕集-气相色谱-质谱法分离鉴定强化高温火腿中的挥发性风味物质

采用顶空吹扫捕集法提取、气相色谱-质谱联用技术分离鉴定强化高温加工过程中腌制结束、成熟中 期、成熟结束、后熟中期、后熟结束期火腿中的挥发性风味化合物,并研究新工艺过程中挥发性风味物质的发展 规律,并采用相对气味活度值判定其特征性风味化合物。结果表明：挥发性风味成分种类与传统工艺相似,但相 对含量有所不同,尤其是酸类、酯类;同时新检测出茚、二苯并呋喃、2,3-二甲基萘等化合物;相对气味活度法 判定其主体挥发性成分为3-甲基丁醛、二甲基二硫化合物、2-壬烯醛、2-辛烯醛、辛醛、壬醛、庚醛、戊醛、己 醛、1-辛烯-3-醇、1-庚醇11 种。     

樱桃谷鸭胸肉脂肪氧合酶的分离纯化及其酶学特性研究

用硫酸铵分级沉淀和DEAE-Sepharose柱层析法分离纯化樱桃谷鸭胸肉中脂肪氧合酶(lipoxygenase,LOX),同时对酶学性质进行研究。结果显示：在DEAE-Sepharose柱层析时,当NaCl洗脱浓度在0.3～0.35mmol/L时,LOX被分离出,LOX经过分离纯化后其纯化倍数可达到54.3,SDS-PAGE电泳显示其分子质量约为96kD;粗酶和纯酶性质略有不同;以亚油酸为底物,粗酶和纯酶的最适底物浓度分别为6.4、10mmol/L,最适反应温度分别为40、30℃,最适pH值分别是5.0、5.5;纯酶Km=1.139mmol/L、Vmax=0.07608U/min,纯酶与底物的亲和能力大于粗酶。