Glassy State and Thermal Inactivation of Invertase and Lactase in Dried Amorphous Matrices
Glassy State and Thermal Inactivation of Invertase and Lactase in Dried Amorphous Matrices
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干燥无定形基质中蔗糖酶和乳糖酶的玻璃态和热失活
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发表时间：
1997
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影响因子：
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通讯作者：
J. Chirife
中科院分区：
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作者：
C. Schebor;L. Burin;M. Buera;J. Aguilera;J. Chirife
研究了乳糖酶和蔗糖酶在糖（海藻糖、麦芽糖、乳糖、蔗糖、棉子糖）和其他一些选定系统（酪蛋白、PVP、牛奶）的干燥无定形基质中的热稳定性。玻璃化转变温度（Tg）作为预测酶失活的阈值参数受到限制，因为（a）在玻璃状基质中观察到酶失活，（b）观察到某些基质（特别是海藻糖）对酶稳定的特定作用，以及（c）酶稳定性似乎取决于加热温度（T）“本身”而不是（T - Tg）。由于这些原因，与维持酶的三级结构相关的糖的保护机制受到青睐。在 T > Tg 的加热蔗糖系统中观察到酶（乳糖酶）活性迅速丧失，这归因于蔗糖结晶，因为众所周知，结晶后糖的保护作用就会消失。因此，稳定效果可能会间接受到基质 Tg 的影响，因为糖的结晶仅发生在高于 Tg 的情况下。海藻糖模型系统（添加转化酶）在干燥状态下加热至高温并长时间加热时，表现出对“变暗”（例如非酶促褐变）的出色稳定性。
The thermal stability of enzymes lactase and invertase in dried, amorphous matrices of sugars (trehalose, maltose, lactose, sucrose, raffinose) and some other selected systems (casein, PVP, milk) was studied. The glass transition temperature (Tg) was limited as a threshold parameter for predicting enzyme inactivation because (a) enzyme inactivation was observed in glassy matrices, (b) a specific effect of enzyme stabilization by certain matrices particularly trehalose was observed, and (c) enzyme stability appeared to depend on heating temperature (T) “per se” rather than (T − Tg) . For these reasons, a protective mechanism by sugars related to the maintenance of the tertiary structure of the enzyme was favored. A rapid loss of enzyme (lactase) activity was observed in heated sucrose systems at T > Tg, and this was attributed to sucrose crystallization since it is known that upon crystallization the protective effect of sugars is lost. Thus, the stabilizing effect could be indirectly affected by the Tg of the matrix, since crystallization of sugars only occurs above Tg. Trehalose model systems (with added invertase) showed an exceptional stability toward “darkening” (e.g., non‐enzymatic browning) when heated in the dried state to elevated temperatures and for long periods of time.