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What is the Actual Low-Temperature Glass Transition for Fish Flesh?

Chotika VIRIYARATTANASAK�EKiyoshi KAWAI�EManabu WATANABE�EToru SUZUKI

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�@ We measured glass transition temperatures in the maximally freeze-concentrated phase (Tg') of tuna and cod tissue by differential scanning calorimetry (DSC) using an annealing technique. In our experiment, the Tg' (approximately -71�‹C) of tuna and cod tissue did not exhibit any significant change after isothermal holding for several weeks at a temperature higher than the Tg. Another Tg' appeared above -45�‹C when annealing was performed at a temperature higher than -60�‹C for one week. We also collected Tg' data for fish flesh from many published studies and discussed them in the light of our data. The Tg' values for fish flesh in most published reports are higher than -40�‹C, although there have been several reports that give values of around -70�‹C. The high glass transition temperature (i.e., -45�‹C) measured in our study agrees with most of the data in the literature. Furthermore, the results suggest that the glass transition behavior at the higher temperature may be correlated to the vitrification of protein itself.
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Key words : Glass transition temperature, The maximally freeze-concentrated phase, Annealing technique, Tuna, Cod
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