乳清浓缩蛋白WPC80凝胶工艺确定及其凝胶特性分析

以乳清浓缩蛋白(WPC80)为研究对象,分析了温度、时间、料液浓度、钙离子强度、乳糖浓度及pH值对其凝胶的影响,并通过测试样品凝胶特性。确定了WPC80凝胶的最佳工艺条件:配置质量分数为9%的WPC80溶液,室温400 r/min搅拌30 min至样品全部溶解;4℃储存10 h以上,便于蛋白溶解及水合;添加质量分数为0.12%的氯化钙;65℃,转速为80 r/min恒温水浴30 min;调节样品pH值为5.5;85℃水浴静置20 min形成凝胶。

热处理和调节pH改性乳清蛋白浓缩物对搅打稀奶油加工性质的影响

通过热处理和调节p H对乳清蛋白浓缩物80（Whey protein concentrate,WPC80）进行改性处理,并将改性后的WPC80添加至低脂稀奶油中,以改善其搅打性质。结果表明调节WPC80溶液的p H为3,在80℃下加热15min时具有最佳的溶解性和起泡性,相同p H条件下,不同的热处理时间会对溶解性和起泡性产生不同的影响;将热处理和p H改性后WPC80加入搅打稀奶油中,研究发现不同热处理时间,p H为5改性的WPC80可以显著提高搅打稀奶油的打发率（p〈0.05）,但是p H为7处理的WPC80使稀奶油的泡沫稳定性增加了154.67%~193.42%。因此可通过热处理和调节p H改性的WPC80来提高低脂稀奶油的搅打特性,且此操作方法简单易行。

超高压处理对浓缩乳清蛋白80加工性质和蛋白结构的影响

研究了超高压处理(300MPa和600MPa,10min)对浓缩乳清蛋白80加工性质和蛋白结构的影响。结果表明,300MPa和600MPa处理10min后,浓缩乳清蛋白80的△E值显著增加(p<0.05),明度值(L*)、a*和b*也发生不同程度变化;600MPa处理样品D50值较对照样品增加了22.13倍;此研究中的超高压处理条件主要影响了浓缩乳清蛋白80的起泡性和乳化性,对溶解性并未有显著影响(p>0.05);结合聚丙烯酰胺凝胶电泳和圆二色谱分析,300MPa和600MPa处理10min只是改变了蛋白的二级结构,但对乳清蛋白的分子量影响不显著。

不同浓缩乳清蛋白80粉的特性分析及其对酸奶品质的影响

分析了10种商业WPC80的理化指标、热凝胶性、热稳定性、溶解度、变性程度,并对各凝胶型WPC80应用于酸奶后的质构特性、感官特性进行了研究。结果表明,不同WPC80在理化指标方面,脂肪、乳糖、灰分等质量分数方面差异显著(P<0.05)。不同WPC80具有的热凝胶性、热稳定性和溶解度方面都存在差异,在变性程度方面差异较小。WPC80的热凝胶性越强,应用于酸奶后,制备的凝固型酸奶的弱凝胶力则越强,制备的搅拌型酸奶的粘稠度则越强。

Nutritional evaluation of caseins and whey proteins and their hydrolysates from Protamex

Whey protein concentrate (WPC 80) and sodium caseinate were hydrolyzed by Protamex to 5%, 10%, 15%, and 20% degree of hydrolysis (DH). WPC 80, sodium caseinate and their hydrolysates were then analyzed, compared and evaluated for their nutritional qualities. Their chemical composition, protein solubility, amino acid composition, essential amino acid index (EAA index), biological value (BV), nutritional index (NI), chemical score, enzymic protein efficiency ratio (E-PER) and in vitro protein digestibility (IVPD) were determined. The results indicated that the enzymatic hydrolysis of WPC 80 and sodium caseinate by Protamex improved the solubility and IVPD of their hydrolysates. WPC 80, sodium caseinate and their hydrolysates were high-quality proteins and had a surplus of essential amino acids compared with the FAO/WHO/UNU (1985) reference standard. The nutritive value of WPC 80 and its hydrolysates was superior to that of sodium caseinate and its hydrolysates as indicated by some nutritional parameters such as the amino acid composition, chemical score, EAA index and predicted BV. However, the E-PER was lower for the WPC hydrolysates as compared to unhydrolyzed WPC 80 but sodium caseinate and its hydrolysates did not differ significantly. The nutritional qualities of WPC 80, sodium caseinate and their hydrolysates were good and make them appropriate for food formulations or as nutritional supplements.