STANDARDIZATION OF OYSTER SOFT-TISSUE DRY-WEIGHT MEASUREMENTS

Four methods for drying oyster soft tissues were compared: oven-drying at 105, 100 and 80-degrees-C and freeze-drying. Weights were recorded every 12 h for 5 days, and after sample treatments were switched, eve ry 24 h for another 3 days. The time required for all the oysters in a treatment to reach constant weight was 36, 36 and 60 h for 105, 100, 80-degrees-C over-dried treatments and 120 h for the freeze-dried trea tment. Within a treatment, the time required to reach constant weight was not weight-related. The average ratio of wet to 5-day dry weight r anged from 9.07 to 9.47 for oven-drying but was only 7.35 for freeze-d rying. After 3 additional days at 105-degrees-C, the 105, 100, 80-degr ees-C oven-dried and freeze-dried groups lost an additional < 1, 1, 1 and 8% of their mean weights, respectively. All oven-dried groups pine d 1% over the 5-day weight in the freeze drier, while the freeze-dried group lost an additional 2% in 3 days. The temperature for oven-dryin g, at least between 80 and 105-degrees-C, affected final dry weights b y 1% or less, but the drying times required to achieve constant weight were different. Freeze-drying required more time than oven-drying. Ov en-drying should be continued to constant weight whatever the drying t emperature employed and however long that takes.