酵母抽提物中呈味核苷酸含量偏低的原因探讨(Ⅱ) 啤酒酵母自溶过程核酸的降解规律研究

The Reason for the Low Content of Flavor Enhancer ( 5'-GMP) in the Yeast Extract (Ⅱ) RNA Degradation Properties in Yeast Autolysis

本论文通过详细测定酵母自溶过程中蛋白质、核酸以及各种核苷酸在产物中的变化量,研究pH、外加5’-磷酸二酯酶(麦芽根核酸酶)、外加蛋白酶等对酵母自溶的影响,从而探讨外加5’-磷酸二酯酶不能显著提高酵母自溶产物中呈味核苷酸含量的原因。研究结果显示:在自溶过程直接添加麦芽根核酸酶只能略提高酵母抽提物中呈味核苷酸的含量,但提高程度不明显;在pH8自溶的产物中5’-核苷酸和3’-核苷酸的量均显著低于在pH5自溶的产物中的量。酵母在pH8～8.5条件下自溶时,外加蛋白酶可以显著提高酵母自溶物产物中可溶性固形物含量、可溶性蛋白质和核苷酸的含量,显著降低核酸含量,产物中的5'-核苷酸含量显著比3'-核苷酸含量高。上述结果说明了酵母在外加麦芽根核酸酶条件下自溶时,核酸未能迅速降解并生成大量的呈味核苷酸的原因之一是由于酵母细胞壁的存在阻碍了细胞器中核酸的溶出,致使外加的5'-磷酸二酯酶不能很好与核酸底物接触,从而不能有效提高呈味核苷酸的产量。

The effects of pH value, RNase from malted barley roots and the added proteinase on the yeast autolysis wereresearched. The results showed that: (1) 5'-nucleotide contents in yeast autolysate was slightly increased by adding RNase frommalted barley roots; (2) higher pH did not improve the 5'-nucleotide contents even in the presence of RNase from malted barleyroots, but at the pH 8.0, the addition of Acalase could increase the final yield, soluble protein contents and 5’-nucleotide inthe presence of RNase from malted barley roots. These results suggested that the reason for the low content of flavor enhancer( 5'-GMP) in the yeast extract may be due to the yeast cell wall that block the degradation of the adding RNase from maltedbarley roots on the RNA.