南美白对虾肉玻璃化转变温度测定的影响因素

Factors Influencing the Determination of Glass Transition Temperature of Penaeus vannamei Meat

摘要:

为准确测定南美白对虾肉的玻璃化转变温度（Tg），对影响其Tg测定的因素（包括差示扫描量热仪（DSC）测定过程中程序扫描次数、退火温度和时间、加热速率、样品湿基含水率）进行了系统研究。结果表明，含非冻结水的虾肉宜采用单扫描程序。含冻结水的虾肉冰晶体出现始、末对应的温度范围为-22 ℃~-53 ℃，在此温度范围内退火30 min，焓变ΔH先降低后增加，当ΔH达到最小值171.1 J/g时，与之对应的温度为-35 ℃，即为虾肉适宜的退火温度。虾肉Tg随退火时间的延长而降低，且在超过30 min后逐渐趋于稳定，因此适宜退火时间为30 min。虾肉Tg随升温速率的降低而降低，并在速率低于5 ℃/min后逐渐趋于恒定，适宜升温速率范围5 ℃/min。Tg随虾肉含水率的增加而降低，含水率＜25.88%时，Tg降低趋势明显；而含水率＞25.88%时，Tg降低幅度很小并逐渐趋于恒定。本研究结果可为南美白对虾肉DSC扫描程序的确定提供理论依据。

Abstract:

In order to accurately determine the glass transition temperature (Tg) of Penaeus vannamei meat, the factors affecting the Tg determination, including the scanning mode type (single or double scan), heating rate, annealing temperature and time, and sample wet-basis moisture content during the measurement as determined by differential scanning calorimetry (DSC), were systemically investigated. The experimental results showed that single scan mode was appropriate for the DSC analysis of shrimp samples containing nonfreezable water. For the samples containing freezable water, the corresponding beginning and end temperatures for ice crystallization were between -22 ℃ and -53 ℃. When the annealing treatment was conducted in this temperature range for 30 min, the enthalpy change (ΔH) first decreased and then increased. When the ΔH value achieved the minimum value of 171.7 J/g, the corresponding temperature was -35 ℃, i.e., the suitable annealing temperature. The Tg values of the shrimp meat decreased with increasing annealing time and were gradually stabilized after 30 min. Therefore, the optimum annealing time was 30 min. The Tg values decreased with decreasing heating rate and were gradually stabilized when the heating rate was lower than 5 ℃/min. Therefore, the optimum heating rate was 5 ℃/min. The Tg values decreased with increasing moisture content in the shrimp meat. Tg had an apparent decreasing trend when the moisture content was lower than 25.88%; the reduction of Tg was very small and it gradually stabilized when the moisture content was higher than 25.88%. The results could provide a theoretical basis for determining DSC scanning protocols for Penaeus vannamei meat.