Thunell R K, Ernstrom C A, Hartman G H
J Dairy Sci. 1980 Jan;63(1):32-6. doi: 10.3168/jds.S0022-0302(80)82884-0.
Four commercial sterile milk-based dietetic products were inoculated aseptically with small concentrations of a commericial milk clotting enzyme derived from Mucor miehei and incubated at 30 C for 32 wk. One of the products, Sustacal, exhibited no observable changes in body and texture during storage. Enzyme concentrations of 1 x 10(-4) chymosin units per milliliter or higher induced undesirable changes in the body of the other three products, Enfamil Ready-to-Use, Enfamil Concentrate, and Metrecal Shape. None of the products was affected visibly by enzyme concentrations of 1 x 10(-5) chymosin units per milliliter or less. In-can sterilization of Enfamil Ready-to-Use at 126.1 C for 4.5 min and Enfamil Concentrate at 126.7 C for 4.23 min completely destroyed all measurable enzyme activity at concentrations (up to 5.5 x 10(-2) chymosin units per milliliter) in these experiments. However, 1 to 3 h between formulation and sterilization allowed time for the enzyme at concentrations of 1 x 10(-2) chymosin units per milliliter or more to cause coagulation during heat sterilization.
四种市售的无菌乳基营养产品用小浓度的源自米黑毛霉的市售凝乳酶进行无菌接种，并在30℃下孵育32周。其中一种产品Sustacal在储存期间身体和质地未出现明显变化。每毫升1×10(-4)凝乳酶单位或更高的酶浓度会在其他三种产品（即Enfamil即食型、Enfamil浓缩型和Metrecal Shape）的身体上引起不良变化。每毫升1×10(-5)凝乳酶单位或更低的酶浓度对这些产品均无明显影响。在这些实验中，Enfamil即食型在126.1℃下进行4.5分钟的罐内灭菌以及Enfamil浓缩型在126.7℃下进行4.23分钟的罐内灭菌，能完全破坏所有可测量的酶活性（浓度高达每毫升5.5×10(-2)凝乳酶单位）。然而，在配方和灭菌之间间隔1至3小时，使得每毫升1×10(-2)凝乳酶单位或更高浓度的酶在热灭菌期间有时间导致凝固。
