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