Determination of moisture and fat content of angel fish caught as by-catches in Namibia

Abstract

Abstract by author:

The fat and moisture content in fish is expressed in percentage, however the methods used to determine them are different from each other. In this practical I determined the moisture by drying the samples in a vacuum oven to evaporate the moisture. The fat I determined by placing the samples in a warm water bath for digestion followed by a cold-water bath to separate the layers of the sample. Fats are described as substances that are soluble in non-polar solvents but insoluble in water. Water (moisture) and fat content are the two major nutrients found in fish. Their content varies greatly from species to species, also according to seasonal changes, etc. The variation of the fat content has lead to fish being categorized into three different fat classes, namely, lean fish, moderate-fat fish and high-fat fish. Studies done on fish have revealed that the higher the fat content in the fish is, the lower the water content will be and vice-versa. The moisture and fat content of the fish also affect the spoilage rate of the fish. The moisture provides an environment for spoilage microorganisms, whereas the fat is susceptible to rancidity if exposed to the air. Different methods such as freezing and drying, are used for preserving fish because they make water unavailable to the spoilage microorganisms and prevent degradation of the fats. The study on B. brama species for the moisture and fat is considered successful because the results were within the ranges of earlier studies done by Kirschmann (1984) and other food scientists