Demott B J, Praepanitchai O A
J Dairy Sci. 1978 Feb;61(2):164-7. doi: 10.3168/jds.S0022-0302(78)83573-5.
Xanthine oxidase activity in milk was determined by measuring the rate of formation of vanillic acid from vanillin. Raw milk received at a dairy plant had .208 units xanthine oxidase activity per ml and after 24-h storage at 4 C, .228 units per ml. Upon further storage activity decreased. Heating the fresh raw milk in a water bath to 55 C increased xanthine oxidase activity to .236 units per ml. Partial inactivation of the enzyme occurred when milk was heated at 60, 65, or 70 C for 5 min, and destruction was almost complete with heat at 75 C for 5 min. Raw milk heated at 48 C for 5 min and homogenized at pressures between 70.3 and 281.2 kg/cm2 had xanthine oxidase activities which were a linear function of pressure and showed that each additional kg/cm2 pressure resulted in additional xanthine oxidase activity of .16 milliunits per ml of milk.
通过测量香兰素生成香草酸的速率来测定牛奶中的黄嘌呤氧化酶活性。一家乳制品厂收到的原料乳每毫升含有0.208单位的黄嘌呤氧化酶活性，在4℃储存24小时后，每毫升为0.228单位。进一步储存后活性降低。将新鲜原料乳在水浴中加热至55℃，黄嘌呤氧化酶活性增加至每毫升0.236单位。当牛奶在60℃、65℃或70℃加热5分钟时，酶会部分失活，而在75℃加热5分钟时，酶几乎完全被破坏。在48℃加热5分钟并在70.3至281.2千克/平方厘米的压力下均质化的原料乳，其黄嘌呤氧化酶活性是压力的线性函数，表明每增加1千克/平方厘米的压力，每毫升牛奶的黄嘌呤氧化酶活性就会增加0.16毫单位。
