Dairy Science Department, South Dakota State University, Brookings 57007, USA.
J Dairy Sci. 2012 Nov;95(11):6332-8. doi: 10.3168/jds.2012-5649. Epub 2012 Aug 29.
The objective of this research was to produce whey protein concentrate (WPC) with modified functionality using exopolysaccharide- (EPS) producing cultures. Two different EPS-producing cultures, Lactococcus lactis ssp. cremoris JFR and Streptococcus thermophilus, producing EPS1 and EPS2 respectively, were used in this study. One EPS-nonproducing commercial cheese culture (DVS 850; Chr. Hansen, Milwaukee, WI) was used as the control. Reconstituted sweet whey powder was used in this study to eliminate variations from fresh whey. Cultures grown overnight in reconstituted WPC (10% wt/vol) were added, directly or after overnight cooling (cooled EPS), at 2% (wt/vol) to 6% (wt/wt) solution of reconstituted whey. Whey was then high-temperature, short-time pasteurized at 75 °C for 35s and ultrafiltered to a volume reduction factor of 5. Ultrafiltered whey (retentate) was spray dried at inlet and outlet air temperatures of 200 and 90 °C, respectively, to obtain WPC. In general, the solubility of WPC was higher at pH 7 than at pH 3. Whey protein concentrate containing EPS2 exhibited higher protein solubility than did WPC containing no EPS. Also, the presence of EPS in WPC decreased protein denaturation. The emulsifying ability of WPC containing EPS was higher than that in control. Addition of EPS to WPC significantly enhanced its gelling ability. Foam overrun and hydrophobicity of WPC were not affected by addition of EPS. In conclusion, data obtained from this study show that EPS modify WPC functionality. The extent of modification depends on the type of EPS. Cooling of culture containing EPS before its addition to whey further reduced WPC protein denaturation and increased its solubility at pH 7 and gel hardness.
本研究的目的是利用产生胞外多糖（EPS）的培养物生产具有改良功能的乳清蛋白浓缩物（WPC）。本研究使用了两种不同的产生 EPS 的培养物，即乳球菌乳亚种。 cremoris JFR 和嗜热链球菌，分别产生 EPS1 和 EPS2。使用一种不产生 EPS 的商业奶酪培养物（DVS 850；Chr。汉森，密尔沃基，威斯康星州）作为对照。本研究使用再水合的甜乳清粉来消除新鲜乳清的变化。 overnight 在再水合的 WPC（10%wt/vol）中培养 overnight 的 culture 被添加，直接添加或 overnight 冷却后添加（冷却的 EPS），以 2%（wt/vol）至 6%（wt/wt）再水合乳清溶液。然后将乳清在 75°C 下进行高温短时间巴氏杀菌 35s，并进行超滤，体积减少因子为 5。超滤乳清（保留物）在入口和出口空气温度分别为 200°C 和 90°C 的条件下喷雾干燥，以获得 WPC。一般来说，WPC 的溶解度在 pH 7 时高于 pH 3。含有 EPS2 的 WPC 表现出比不含 EPS 的 WPC 更高的蛋白质溶解度。此外，WPC 中 EPS 的存在降低了蛋白质变性。含有 EPS 的 WPC 的乳化能力高于对照。向 WPC 添加 EPS 显著增强了其胶凝能力。添加 EPS 不会影响 WPC 的泡沫上升率和疏水性。总之，本研究获得的数据表明 EPS 可改变 WPC 的功能。修饰程度取决于 EPS 的类型。在将含有 EPS 的 culture 添加到乳清之前对其进行冷却，可进一步降低 WPC 蛋白质变性，并提高其在 pH 7 时的溶解度和凝胶硬度。
