Dairy Processing and Products Research Unit, U.S. Dept. of Agriculture, Agricultural Research Service, Eastern Regional Research Center, Wyndmoor, PA 19038, USA.
J Food Sci. 2009 Aug;74(6):M319-27. doi: 10.1111/j.1750-3841.2009.01228.x.
Thermal preservation is used by the egg industry to ensure the microbiological safety of liquid egg white (LEW); however, it does not eliminate all microorganisms and impairs some of the delicate functional properties of LEW. In this study, a pilot-scale cross-flow microfiltration (MF) process was designed to remove the natural microflora present in commercial LEW, obtained from a local egg-breaking plant, while maintaining the nutritional and functional properties of the LEW. LEW, containing approximately 10(6 +/- 1.7) colony forming units (CFU) per milliliter of total aerobic bacteria, was microfiltered using a ceramic membrane with a nominal pore size of 1.4 microm, at a cross-flow velocity of 6 m/s. To facilitate MF, LEW was screened, homogenized, and then diluted (1 : 2, w/w) with distilled water containing 0.5% sodium chloride. Homogenized LEW was found to have a threefold lower viscosity than unhomogenized LEW. Influence of MF temperature (25 and 40 degrees C) and pH (6 and 9) on permeate flux, transmission of egg white nutrients across the membrane, and microbial removal efficiency were evaluated. The pH had a significantly greater influence on permeate flux than temperature. Permeate flux increased by almost 148% when pH of LEW was adjusted from pH 9 to pH 6 at 40 degrees C. Influence of temperature on permeate flux, at a constant pH, however, was found to be inconclusive. Microbial removal efficiency was at least 5 log(10) CFU/mL. Total protein and SDS-PAGE analysis indicated that this MF process did not alter the protein composition of the permeate, compared to that of the feed LEW, and that the foaming properties of LEW were retained in the postfiltered samples.
热保鲜被蛋品行业用于确保液体蛋清 (LEW) 的微生物安全性；然而，它并不能消除所有微生物，并损害 LEW 的一些精细功能特性。在这项研究中，设计了一个中试规模的错流微滤 (MF) 工艺，以去除来自当地打蛋厂的商业 LEW 中存在的天然微生物菌群，同时保持 LEW 的营养和功能特性。LEW 中总需氧菌数约为每毫升 10(6 +/- 1.7) 个菌落形成单位 (CFU)，使用孔径为 1.4 微米的陶瓷膜，在 6 m/s 的错流速度下进行微滤。为了便于 MF，LEW 经过筛选、均化，然后用含有 0.5%氯化钠的蒸馏水稀释 (1 : 2，w/w)。均化后的 LEW 的粘度比未均化的 LEW 低三倍。评估了 MF 温度（25 和 40°C）和 pH（6 和 9）对渗透通量、蛋清营养物质透过膜的传输以及微生物去除效率的影响。pH 对渗透通量的影响明显大于温度。在 40°C 时，将 LEW 的 pH 从 9 调整到 6，渗透通量增加了近 148%。然而，在恒定 pH 下，温度对渗透通量的影响则不明确。微生物去除效率至少为 5 log(10) CFU/mL。总蛋白和 SDS-PAGE 分析表明，与进料 LEW 相比，这种 MF 工艺不会改变渗透物的蛋白质组成，并且 LEW 的起泡性能在过滤后的样品中得以保留。
