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101.
In this study, we aimed to examine the effect of phosvitin on lipid and protein oxidation of raw and cooked ground beef treated with high hydrostatic pressure (HHP). Ground beef patty with 0, 500, or 1000 mg phosvitin/kg meat was treated with HHP at 0.1, 300, or 600 MPa. Half of the patties were used in a raw meat analysis, and the other half were used in a cooked meat analysis. Phosvitin and HHP treatment at 300 MPa synergistically reduced microbial growth, and HHP treatment at 600 MPa reduced microbial counts to undetectable levels (< 1 log CFU/g) throughout the length of the study in all samples. Phosvitin delayed lipid and protein oxidation in HHP-treated cooked and raw ground beef, respectively. However, phosvitin had no effect on the color changes of raw ground beef attributable to HHP. The results indicated that phosvitin could enhance the stability of lipids and proteins but not color changes of raw ground beef caused by HHP.  相似文献   
102.
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.  相似文献   
103.
Hydrostatic pressure (HP) and heat treatments of myofibrillar proteins have both been shown to induce protein denaturation, but different gel formation properties result from these treatments. To characterise differences in the properties of proteins resulting from HP or heat treatment, Ca‐ and Mg‐ATPase activities (ATP, adenosine triphosphate) and protein solubility in 0.1 and 0.6 mol L?1 KCl buffers (pH 7) were evaluated in this study. The inactivation rate of Ca‐ATPase of myofibrillar proteins (Mf) induced by HP was slower than that of Mg‐ATPase at each of the tested pressures. However, the inactivation rate of Ca‐ATPase induced by heating was faster than that of Mg‐ATPase at each of the tested temperatures. The level of soluble proteins in Mf suspension induced by HP in 0.1 mol L?1 KCl buffer increased with increasing pressure up to 400 MPa and then decreased slightly at 500 MPa. However, the level of soluble proteins in Mf suspension induced by heat treatment in 0.1 mol L?1 KCl buffer increased with increasing temperature up to 55°C. According to the results of sodium dodecyl sulfate polyacrylamide gel electrophoresis, the levels of soluble myosin heavy chain and actin in Mf suspension induced by HP in 0.6 mol L?1 KCl buffer decreased simultaneously at pressures higher than 300 MPa. The level of soluble MHC in 0.6 mol L?1 KCl buffer decreased gradually with increasing temperature, but there were no changes in the level of soluble actin in 0.6 mol L?1 KCl buffer with increasing temperature up to 50°C. These results showed that the mechanism of HP‐induced protein denaturation was different from the mechanism underlying heat‐induced protein denaturation. Copyright © 2006 Society of Chemical Industry  相似文献   
104.
2 可控中高辊静压支承的设计计算根据可控中高辊的工作特性 ,其静压支承的结构与普通静压支承有较大差异 ,因此在设计计算上也有不同的思路和计算方法。如图 1、图 2所示 ,装设在固定芯轴里的每个柱塞的顶面上布置了 1个中央油腔和 4个边缘小油腔。中央油腔与液压系统供油口直接相通而不像传统结构那样在二者之间设置阻尼器。在 4个小油腔的进油路上则各设置 1个节流阻尼。在各油腔的周边均布置一环形回油槽 ,以消除各油腔间的内流 ,从而提高油膜的支承刚度 ,并有利于柱塞推力的对中自调性。在以下计算中 ,各符号的说明 :Pa——柱塞下腔的…  相似文献   
105.
该研究以山药、秋葵、猕猴桃为原料制备得到的复合山药泥为研究对象,对比分析了超高压(High Hydrostatic Pressure,HHP)处理(400 MPa/5 min,400 MPa/10 min,500 MPa/2 min)和热处理(Thermal processing,TP)(97 ℃/2 min)对复合山药泥在4 ℃下贮藏24 d中微生物、营养成分、抗氧化性、内源酶活性及粒径等品质指标的影响。结果表明,贮藏期间,HHP能很好地抑制微生物生长,400 MPa/5 min和500 MPa/2 min处理样品菌落总数均小于1 lg CFU/g,且所有处理样品中均没有霉菌和酵母菌检出;相比于TP处理,HHP处理后的复合山药泥的总酚含量提高了60.66%~227.54%,因此在贮藏期间其抗氧化能力相对更强;贮藏期间,HHP组的?E显著小于TP组,24 d后TP组的?E达到了25.26,而500 MPa/2 min组仅为5.44,因此HHP处理更能维护复合果蔬泥在贮藏期间的色泽。但是,由于不能有效抑制PME的酶活,HHP处理组在贮藏期间的粒径和黏度均高于TP处理。综上,HHP处理能够满足复合果蔬泥的商业应用需求,但对内源酶活性的抑制效率不高。  相似文献   
106.
Shellfish may internalize dangerous pathogens during filter feeding. Traditional methods of depuration have been found ineffective against certain pathogens. The objective was to explore high hydrostatic pressure (HHP) as an alternative to the traditional depuration process. The effect of HHP on the survival of Vibrio parahaemolyticus in live clams (Mercanaria mercanaria) and the impact of HHP on physical characteristics of clam meat were investigated. Clams were inoculated with up to 7 log CFU/g of a cocktail of V. parahaemolyticus strains via filter feeding. Clams were processed at pressures ranging from 250 to 552 MPa for hold times ranging between 2 and 6 min. Processing conditions of 450 MPa for 4 min and 350 MPa for 6 min reduced the initial concentration of V. parahaemolyticus to a nondetectable level (<101 CFU/g), achieving >5 log reductions. The volume of clam meat (processed in shell) increased with negligible change in mass after exposure to pressure at 552 MPa for 3 min, while the drip loss was reduced. Clams processed at 552 MPa were softer compared to those processed at 276 MPa. However, all HHP processed clams were found to be harder compared to unprocessed. The lightness (L*) of the meat increased although the redness (a*) decreased with increasing pressure. Although high pressure‐processed clams may pose a significantly lower risk from V. parahaemolyticus, the effect of the accompanied physical changes on the consumer's decision to purchase HHP clams remains to be determined. Practical Application : Shellfish may contain dangerous foodborne pathogens. Traditional methods of removing those pathogen have been found ineffective against certain pathogens. The objective of this research was to determine the effect of high hydrostatic pressure on V. parahaemolyticus in clams. Processing conditions of 450 MPa for 4 min and 350 MPa for 6 min reduced the initial concentration of V. parahaemolyticus to a nondetectable level, achieving >5 log reductions.  相似文献   
107.
本研究运用超高压处理、碱性pH偏移处理对大豆分离蛋白(soy protein isolate, SPI)进行单独和复合处理后,将其与麦芽糊精进行糖基化反应,并测定不同预处理条件对复合物结构及乳化性质影响。结果表明,与单一超高压处理或pH偏移处理相比,高压协同碱性pH偏移处理对糖基化反应的促进效果更明显。复合处理使糖基化复合物的接枝度与褐变程度增大,二级结构由有序向无序的转变程度增大,蛋白质内部疏水基团暴露量增多,蛋白分子三级结构趋于松散。其中400 MPa高压处理协同碱性pH偏移处理对糖基化改性的促进效果最为显著,所得糖基化样品的乳化活性(31.38 m2/g)和乳化稳定性值(36.88 min)最大,分别为对照组的1.89倍和1.60倍。  相似文献   
108.
采取不同的高静水压条件(处理压强、施压温度、保压时间)处理产犊后48 h内的牛初乳,研究高静水压处理牛初乳对免疫球蛋白G(immunoglobulin G,IgG)活性的影响。将牛初乳离心去除酪蛋白、乳脂肪等,取上清液进行高静水压处理,采用高效液相色谱法和十二烷基硫酸钠-聚丙烯酰胺凝胶电泳法(sodium dodecyl sulfatepolyacrylamidegel electrophoresis,SDS-PAGE)对处理后的样品进行检测。结果表明:高静水压处理后的样品,经高效液相色谱仪检测,其与亲和色谱柱发生特异性吸附的能力下降,IgG检出质量浓度降低;经SDS-PAGE检测和凝胶电泳成像仪扫描处理,不同处理条件下IgG的轻链和重链的质量变化不显著。因此,当牛初乳在200 MPa、30 ℃和20 min的高静水压处理条件下,IgG的活性最好,检出质量浓度为16.843 9 mg/mL。  相似文献   
109.
超高压番茄汁杀菌条件的优化研究   总被引:3,自引:0,他引:3  
本研究通过响应面法(RSM)建立了超高压杀灭番茄汁中枯草芽孢杆菌(B.subtilis)AS1.1380的二次多项数学模型,验证了模型的有效性。同时利用模型的响应面及其等高线对影响超高压杀菌的关键因子温度、压力和保压时间及其相互作用进行了深入的探讨。优化出杀灭番茄汁中6个数量级枯草芽孢杆菌AS1.1380的工艺参数为:温度33.5℃,压力469.2MPa,时间14.0min。  相似文献   
110.
在满足传动性能和边界约束条件下,根据汽车起重机转向机构的内、外转向轮理想的转角关系,以内侧转向轮理论转角和实际的内轮转角之间均方根误差最小为优化目标,建立了优化设计的数学模型。由于传统的优化方法存在着求解过程复杂和寻优过程容易陷入局部最优解的问题,故应用matlab遗传算法工具箱寻求最优解,使求解过程得到简化,能可靠地获得全局最优解。  相似文献   
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