Storage to maintain optimum quality
In order for feed to be in an acceptable state when fed to fish, appropriate measures and practices must be undertaken. Incorrect storage can result in loss of nutritional value, mould growth, fat rancidity and infestation by insects and rodents. During storage, it is inevitable that the vitamins in formulated foods will degrade with time. Vitamins are highly reactive and unstable organic compounds that can be easily denatured by oxygen, heat, moisture and ultraviolet light. The rate of the loss depends largely on the vitamin and the conditions in which the food is stored. Thus dried foods should be stored away from direct sunlight in a sealed, airtight container. The conditions under which it should be stored should be cool, dry and exempt from rapid changes in temperature.
During manufacture certain measures are taken to eliminate bacteria and moulds including heat and dehydration steps, but there are certain spores of moulds that are able to survive the harshest of treatments (Soyaqua, 2008). These spores are able to become active only when favourable conditions arise, such as sufficient moisture levels and temperature. These spores grow best when the moisture content of the feed is 14.5 to 20% combined with a relative humidity of 70 to 90% (Soyaqua, 2008). Therefore moisture must not be introduced to dried foods through actions such as letting water droplets enter the container during feeding or leaving the container open for unnecessarily long periods of time.
Fish feed is generally quite high in levels of unsaturated fatty acids as they are essential for good health and growth of many fish species. Though beneficial, it renders the feed highly prone to oxidative rancidity resulting in ‘off’ odours and flavours, and so must again be stored away from direct sunlight, as this can speed up the oxidative process.
Frozen foods should be stored at a steady temperature of approximately -18oc with minimum fluctuations. These foods should not be defrosted and refrozen repeatedly as it will degrade the food value.
Live foods can be kept in the refrigerator to slow biochemical reactions, prolonging the time in which they can be kept.
