Variations in proximate composition and percentage edibility of wild and cultured Indian Backwater oyster ( Crassostrea madrasensis ) in Sri Lanka

Abstract

Indian Backwater oysters (Crassostrea madrasensis) are available en mass around Sri Lanka but nutritional value and seasonal changes have not been studied sufficiently. Proximate composition and percentage edibility (PE) for wild and cultured oysters in Kala Oya estuary and Puttalam lagoon were studied. Influence of environmental factors on proximate composition was also analysed for both cultured and wild oysters. The mean values ranged from 5.67 ± 0.15% to 8.08 ± 0.01% for protein, 1.02 ± 0.01% to 2.08 ± 0.26% for lipid, 1.39 ± 0.02% to 2.61 ± 0.09% for ash, 84.68 ± 0.28% to 89.72 ± 0.21% for moisture, 10.28 ± 0.21% to 15.32 ± 0.28% for dry weight and 1.37 ± 0.43% to 4.41 ± 0.47% for carbohydrate. A positive relationship with salinity was found for mean percentage of lipid (Adj-R2 = 57.68%, p < 0.05), dry weight (Adj-R2 = 61.58%, p < 0.001) and carbohydrate (Adj-R2 = 40.71%, p < 0.001) while a negative relationship was found for moisture (Adj-R2 = 61.58%, p < 0.001). PE varied from 6.10 ± 2.73% to 10.66 ± 6.70%, and a peak was observed from October to February for cultured oysters. The prominent peak of PE during October to February is suggestive of suitable harvesting period of cultured C. madrasensis.