High hydrostatic pressure modification of whey protein concentrate for improved functional properties

Whey protein concentrate (WPC) has many applications in the food industry. Previous research demonstrated that treatment of whey proteins with high hydrostatic pressure (HHP) can enhance solubility and foaming properties of whey proteins. The objective of this study was to use HHP to improve functional properties of fresh WPC, compared with functional properties of reconstituted commercial whey protein concentrate 35 (WPC 35) powder. Fluid whey was ultrafiltered to concentrate proteins and reconstituted to equivalent total solids (8.23%) as reconstituted commercial WPC 35 powder. Solutions of WPC were treated with 300 and 400 MPa (0- and 15-min holding time) and 600 MPa (0-min holding time) pressure. After HHP, the solubility of the WPC was determined at both pH 4.6 and 7.0 using UDY and BioRad protein assay methods. Overrun and foam stability were determined after protein dispersions were whipped for 15 min. The protein solubility was greater at pH 7.0 than at pH 4.6, but there were no significant differences at different HHP treatment conditions. The maintenance of protein solubility after HHP indicates that HHP-treated WPC might be appropriate for applications to food systems. Untreated WPC exhibited the smallest overrun percentage, whereas the largest percentage for overrun and foam stability was obtained for WPC treated at 300 MPa for 15 min. Additionally, HHP-WPC treated at 300 MPa for 15 min acquired larger overrun than commercial WPC 35. The HHP treatment of 300 MPa for 0 min did not improve foam stability of WPC. However, WPC treated at 300 or 400 MPa for 15 min and 600 MPa for 0 min exhibited significantly greater foam stability than commercial WPC 35. The HHP treatment was beneficial to enhance overrun and foam stability of WPC, showing promise for ice cream and whipping cream applications.     

榛子蛋白质提取及功能特性研究

采用碱提酸沉法从脱脂榛子粉中提取榛子蛋白质,研究浓度、温度等影响因素与榛子蛋白质功能特性的关系,并测定榛子蛋白质等电点。结果显示,从脱脂榛子粉中提取蛋白质最佳条件为：料液比1：6,碱溶pH8．0、温度40℃、时间0．5h,酸沉pH4．5;榛子蛋白质起泡性在浓度为4％时最高,泡沫稳定性在浓度为2％时最大;其乳化性在浓度为2％时最大,静置的温度对乳化稳定性影响很小;蛋白质吸油性为3．72ml／g其蛋白质分散指数（PDI）在50℃时最大,50℃以上PDI开始下降,70℃以后变化不大;其在浓度1％、60℃、1．5h条件下持水性最好;其等电点为4．52。     

A review of natural antioxidants and their effects on oxidative status, odor and quality of fresh beef produced in Argentina

Meat derived from pasture feeding, is associated with a high level of antioxidants. Antioxidants are incorporated within cell membranes and protect tissues against oxidation from reactive oxygen species. This maintains the overall quality of meat and secondary products. This paper reviews the implications of incorporating natural antioxidants into fresh beef, focusing on the benefits of feeding cattle good quality pasture. Pasture samples typically have higher levels of α-tocopherol, β-carotene, ascorbic acid and glutathione than feedlot samples. These compounds retard lipid and protein oxidation in fresh and stored meat, and preserve the color and odor quality of beef. The significance of antioxidant enzymes is variable, because their behavior depends on individual redox status before slaughter. Understanding total antioxidant activity requires information on antioxidant and pro-oxidant status. With an abundance of pasture, Argentina has a natural advantage in producing meat with a high antioxidant value.     

The mammalian target of rapamycin pathway and its role in molecular nutrition regulation

Mammalian target of rapamycin (mTOR) is a protein serine-threonine kinase that functions as a central element in signaling pathway involved in control of cell growth and proliferation. mTOR exists in at least two distinct multi-protein complexes, mTORC1 and mTORC2. mTOR kinase controls the translation machinery, in response to nutrients and growth factors, via activation of p70 ribosomal S6 kinase and inhibition of eukaryotic initiation factor-4E-binding protein. In this report, we review the mTOR signaling pathway and its interaction with food intake, insulin resistance, lifespan and adipogenic regulation during the molecular nutrition regulation.     

An analytical approach to reveal the addition of heat-denatured whey proteins in lab-scale cheese making

A simple analytical procedure for the detection of self-aggregated heat-denatured whey proteins (HDWP) in model cheeses was developed. The principle of the approach lies in the solubilization of the cheese matrix by a sodium citrate solution (0.2 M, pH 7.0) resulting in the dissociation of the casein micelles and the insolubilization of HDWP aggregates, which are collected in the pellet after a centrifugation step. The reliability of the procedure was tested in lab-scale cheeses from peroxidase-positive pasteurized milk with different protein-based ingredients (microparticulated whey protein concentrate, milk protein concentrate, whey protein isolate and Ricotta cheese) at concentrations ranging from 0.2 to 1.2% protein (w/v on cheese milk). A linear relationship between the amount of the HDWP added to cheese milk and that recovered from model cheeses was observed. Heat-damage indicators, furosine and lysinoalanine, showed levels in the experimental cheese samples not related with added HDWP, but represented a source of information on the ingredients other than liquid milk. Overall, in the model cheeses, the proposed method was an easy-to-apply and reliable tool for the evaluation of the presence of HDWP-based products. Further investigation is required for the application to real cheeses and for the evaluation of possible interferences from proteolysis during ripening.     

Molecular Partners of Escherichia coil Transcriptional Modulator AidB

The AidB protein is involved in the adaptive response to DNA alkylation damages in Escherichia coli. Functional proteomic experiments were designed to elucidate AidB biological functions in the presence and in the absence of methyl methanesulfonate as methylating agent. Several proteins were identified in both conditions and according to their reported biological activities, the inter-actors were grouped into three different functional categories： stress response, energetic metabolic pathways and nucleic acid metabolism. Particularly, the interaction between AidB and UvrA, a member of the UvrABCD nucleotide excision system, suggested a new interesting putative role for AidB.     

高效破乳菌的破乳效能及活性成分

采用Tween 60、Span 60和航空煤油制备稳定的O/W型乳状液作为模型乳状液,将从大庆油田受石油污染土壤中分离到一株芽孢杆菌属莫海威芽孢杆菌(Bacillus mojavensis)XH-1制成XH-1菌全培养液用于该模型乳状液的破乳,考察培养条件和破乳实验条件对XH-1菌破乳性能的影响。结果表明,与目前现场常用化学破乳剂相比,XH-1菌全培养液具有优良的破乳性能,其对O/W型乳状液破乳24h的破乳率可达85％以上。XH-1菌具有较强的传代稳定性;其最佳培养及破乳条件：以葡萄糖和液体石蜡的混合物为碳源、pH值6. 5、摇床转数140~160 r/min。 XH-1菌的破乳活性成分耐低温不耐高温,超声波破碎处理对其破乳活性影响不大,经胃蛋白酶、胰蛋白酶及尿素处理后其基本失活。显微观察及实验分析表明,XH-1菌主要破乳活性成分为胞外分泌的蛋白物质。     

冲调型鲨鱼骨羹的研制

以鲨鱼骨和碎米为主要原料,经高压蒸煮、真空干燥、挤压膨化等工艺研制成方便鲨鱼骨羹。其原料配比为鲨鱼骨粉36％,鲨鱼肉1％,膨化米粉63％,高味料配方为食盐1．0％,味精0．2％,白糖0．65％,香辛料0．6％。     

利用谷氨酰胺转胺酶生产大豆蛋白食用保鲜膜的研究

初步研究了大豆蛋白食用保鲜膜的成膜条件以及膜的透水性、透油性、水溶性等性能。试验结果表明,利用谷氨酰胺转胺酶生产的大豆蛋白食用保鲜膜,有较好的水蒸汽阻隔性能和隔油性,能达到食品保鲜的要求。     

蛋白质的泡沫分离

蛋白质的泡沫分离是根据蛋白质的表面活性原理而进行的一种分离新方法 ,它在蛋白质的分离方面具有潜在应用价值。影响分离的因素主要有蛋白质浓度、pH值、气速、泡沫层高度和泡沫大小等