Effects of Vacuum Freeze-drying on the Quality of the Oyster Ostrea rivularis
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Abstract:
Oysters are abundant in China, and a large number are processed as dried products However, the dried oysters prepared by traditional methods have poor rehydration characteristics and are low value-added products. To produce a high-quality dried oyster, fresh oyster meat was processed by vacuum freeze-drying, and the rehydration characteristics, texture, and contents of protein, fat, and various flavor components were studied. The eutectic point and melting point of the fresh oyster Ostrea rivularis were -25 ℃ and -17.5 ℃, respectively. Fresh oysters were pre-frozen at temperatures of -30 ℃ to -35 ℃ for two hours, and were then vacuum freeze-dried for 15 hours to produce a dried product with a cold trap temperature of -40 ℃ and a vacuum pressure of 20 Pa. Compared with the control product (commercial dried oyster), the freeze-dried product exhibited better rehydration capacity, and could be rehydrated completely within 20 minutes with a rehydration ratio of 3.68. The texture of freeze-dried oysters was better than that of the control product, and the contents of protein and various flavor components were higher than those of the control. Therefore, vacuum freeze-drying can not only decrease protein loss, but maintains the texture and flavor of oysters, indicating that this method can be used to produce high-quality dried oysters.
