Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II, 132, 84084 Fisciano, SA, Italy.
ProdAl S.c.ar.l., Via Ponte don Melillo, 84084 Fisciano, SA, Italy.
Food Res Int. 2017 Sep;99(Pt 1):419-425. doi: 10.1016/j.foodres.2017.06.003. Epub 2017 Jun 3.
The effect of pulsed light (PL) on the aggregation of whey protein isolate (WPI) solutions was investigated. PL fluence values from 4 to 16J/cm were used to treat WPI (1% w/v) solutions in sodium phosphate buffer (pH=7.5). Whey protein structural modification and aggregation were assessed through the determination of free SH-groups and UV-absorption spectra. Additionally, covalent and non-covalently linked protein-protein interactions were identified through the measurement of turbidity, aggregation index, particle size distribution, and SDS-PAGE. WPI upon PL treatment showed structural changes as demonstrated by the immediate increase of free SH-group content (unfolding) and the subsequent formation of a small fraction of aggregation of unfolded proteins, due to both hydrophobic interactions and the formation of disulphide bonds. Turbidity, mean particle size, and aggregation index increased in samples treated at PL fluence from 4 to 16J/cm. Furthermore, particle size distribution analysis of samples treated at higher fluence indicated that WPI dimer dissociation and formation of larger particles were likely to occur. The association of intermediate and larger protein molecules as well as the formation of soluble aggregates between β-lactoglobulin and α-lactalbumin were also observed in gel electrophoresis analysis. In conclusion, the results of this investigation demonstrated the potential of PL treatments to induce protein denaturation, with a minimal formation of soluble protein aggregates.
研究了脉冲光（PL）对乳清蛋白分离物（WPI）溶液聚集的影响。使用 4 至 16J/cm 的 PL 剂量处理 pH=7.5 的磷酸钠缓冲液中的 1%（w/v）WPI 溶液。通过测定游离 SH 基团和紫外吸收光谱来评估乳清蛋白结构修饰和聚集。此外，通过浊度、聚集指数、粒径分布和 SDS-PAGE 的测量来鉴定共价和非共价键合的蛋白质-蛋白质相互作用。PL 处理后的 WPI 表现出结构变化，这表现为游离 SH 基团含量的立即增加（展开），以及随后由于疏水性相互作用和二硫键形成而形成一小部分展开蛋白的聚集。在 PL 剂量从 4 到 16J/cm 处理的样品中，浊度、平均粒径和聚集指数增加。此外，在更高剂量处理的样品的粒径分布分析表明，WPI 二聚体解离和形成更大的颗粒可能发生。在凝胶电泳分析中还观察到中间和较大蛋白质分子的缔合以及β-乳球蛋白和α-乳白蛋白之间可溶性聚集体的形成。总之，这项研究的结果表明，PL 处理具有诱导蛋白质变性的潜力，同时形成最小量的可溶性蛋白质聚集体。
