Effect of Cooking Conditions on Protein Quality of Nile Tilapia (Oreochromis niloticus) Meat

Abstract

To suggest the effective method of protein source utilization for third world people, optimum cooking time and temperature for protein quality of Nile tilapia (Oreochromis niloticus) meat were studied. A significant change in proximate composition between raw and cooked samples was observed in fried samples. Protein content of tilapia meat was ranged from 71.13±0.24 to 94.23±0.34 % on dry weight base. Lipid content was increasing in fried and grilled samples while decreasing in boiled and steamed samples. In nutritional bases, these results prove that tilapia (Oreochromis niloticus) meat is a comparable protein source with other fish species.

Protein digestibility was decreased with the increase of cooking time and temperature. When tilapia meat was boiled for 0.5 minute, digestibility was reached to 88.41±0.33% while it showed 87.66±0.22% in boiled sample for 10 minutes. Similar trend was observed in the rest of cooked samples. Though this difference is not statistically significant but nutritionally it has the meaning that tilapia meats have to be cooked for short time.

Trypsin indigestible substrate (TIS) increased with the decrease of digestibility. When digestibility was 86.96±0.22% in fried samples, TIS was 48.18±1.23mg/g solid but in case of samples showing 84.39±0.83% digestibility, the TIS was 56.46±0.87mg/g solid. This phenomenon entails protein in tilapia is available for digestion by digestive proteolytic enzymes in the digestive tracts.

Higher computed protein efficiency ratio (C-PER) and discriminant computed protein efficiency ratio (DC-PER) than standard ANRC casein could imply that protein found in tilapia is an excellent protein source especialy in essential amino acids (EAA). C-PER was 2.62 for boiled sample and 2.60 for fried sample which showed maximum protein digestibility. DC-PER was 2.70 for boiled and 2.67 for fried sample. Presence of EAA in different levels also supports this winding up. Total Amino acids for boiled samples were around 100 g.a.a/16g N and that of fried samples were 98 g.a.a/g N.

Experimental results suggest that best cooking condition is boiling trailed by steaming and grilling. Although fried samples showed digestibility within the necessary range, it is not nutritionally advised due to its high fat content and low protein digestibility due to severe protein-oxidized lipid interaction.