乳清為牛乳加酸，加熱，或添加凝乳酵素除去沈澱之懸浮液稱之，其總固形物含量約為6.0到6.5％，生物氧需求（biological oxygen demand, BOD)為32000或更高。隨著歐美各國乾酪及發酵奶的產量急遽增加，乳清成了重要的乳製品製造時之副產品（byproduct），因此乳清被濃縮，加工製作成各式不同產品如乳清粉（whey powder），乳清蛋白質濃縮物（whey protein concentrates, WPC）或乳清蛋白質分離物（whey protein isolates, WPI）。 WPC及WPI是將乳清前處理後，利用超過濾（ultrafiltration），膠體過濾（gel filtration），離子交換樹酯（ion exchange），電氣透析(electrodialysate）等方法分離蛋白質。WPC含蛋白質35％至95％，WPI則含高度純化乳清蛋白質90％至95％可直接添加於食物中，其功能有助提高食物溶解（solubility），起泡（foaming），保水（water binding），乳化（emulsification），及凝膠（gelation）。 Whey is the separated watery portion of milk usually obtained by acid, heat, or rennet coagulation. It is opaque and greenish-yellow with total solid generally of 6.0 to 6.5% and a biological oxygen demand of 32,000 or higher. Cheese production is rising sharply, so whey is a major byproduct in United State. Whey can be produced variety products such as whey powder, whey protein concentrates(WPC) and whey protein isolates(WPI). Whey proteins were isolated by ultrafiltration, gel filtration, ion exchange or electrodialysate. WPC contain from 35 to 95% protein, and WPI is a highly purified protein product containing 90 to 95% protein. Whey proteins have excellent functional properties including solubility, foaming, emusification, water binding, and gelation.
