Desrosiers T, Savoie L
Départment de nutrition humaine et de consommation, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, Québec, Canada.
J Dairy Res. 1991 Nov;58(4):431-41. doi: 10.1017/s002202990003003x.
The effect of heat treatments, at various water activities (aW), on digestibility and on the availabilities of amino acids of whey protein samples in the presence of lactose was estimated by an in vitro digestion method with continuous dialysis. Four aW (0.3, 0.5, 0.7 and 0.97), three temperatures (75, 100 and 121 degrees C) and three heating periods (50, 500 and 5000 s) were selected. The initial lysine:lactose molar ratio was 1:1. Amino acid profiles showed that excessive heating of whey (121 degrees C, 5000 s) destroyed a significant proportion of cystine at all aW, lysine at aW 0.3, 0.5 and 0.7, and arginine at aW 0.5 and 0.7. At aW 0.3, 0.5 and 0.7, protein digestibility decreased (P less than 0.05) as the temperature increased from 75 to 121 degrees C for a heating period of 5000 s, and as the heating time was prolonged, from 500 to 5000 s at 121 degrees C. Excessive heating also decreased (P less than 0.05) the availabilities of all amino acids at aW 0.3, 0.5 and 0.7. The availabilities of lysine, proline, aspartic acid, glutamic acid, threonine, alanine, glycine and serine were particularly affected. Severe heating at aW 0.97 did not seem to favour the Maillard reaction, but the availabilities of cystine, tyrosine and arginine were decreased, probably as a result of structural modifications of the protein upon heating. Heating whey protein concentrates in the presence of lactose not only affected lysine, but also impaired enzymic liberation of other amino acids, according to the severity of heat treatments and aW.
采用连续透析的体外消化方法，评估了在不同水分活度（aW）下进行热处理对乳糖存在时乳清蛋白样品的消化率和氨基酸利用率的影响。选择了4种水分活度（0.3、0.5、0.7和0.97）、3种温度（75、100和121℃）和3个加热时间（50、500和5000秒）。初始赖氨酸：乳糖摩尔比为1:1。氨基酸谱显示，乳清过度加热（121℃，5000秒）会使所有水分活度下的相当一部分胱氨酸、水分活度为0.3、0.5和0.7时的赖氨酸以及水分活度为0.5和0.7时的精氨酸被破坏。在水分活度为0.3、0.5和0.7时，当加热时间为5000秒且温度从75℃升至121℃时，以及当在121℃下加热时间从500秒延长至5000秒时，蛋白质消化率下降（P<0.05）。过度加热还会使水分活度为0.3、0.5和0.7时所有氨基酸的利用率下降（P<0.05）。赖氨酸、脯氨酸、天冬氨酸、谷氨酸、苏氨酸、丙氨酸、甘氨酸和丝氨酸的利用率受到的影响尤为显著。在水分活度为0.97时进行的剧烈加热似乎不利于美拉德反应，但胱氨酸、酪氨酸和精氨酸的利用率下降，这可能是加热后蛋白质结构发生改变的结果。根据热处理的强度和水分活度，在乳糖存在的情况下加热乳清蛋白浓缩物不仅会影响赖氨酸，还会损害其他氨基酸的酶解释放。
