Effect of different sources of starch guar and guar gum on aqua stability of shrimp feed pellets.

Abstract

A shrimp feed formulation, consisting of fishmeal, squid meal, prawn head meal, soybean meal, cereal flour (different sources), fish oil, lecithin and other feed additives was selected for evaluating aquastability of different sources of starch namely, corn flour, maida flour, rice flour, tapioca flour and wheat flour as binders at 15.3% each in combination with guar gum at three levels of 1, 2 and 3%. The feed pellets were prepared (3-5 mm length, 3mm diameter) by adding 40 ml water for 100g dry powdered feed mix followed by steaming, pelleting in hand pelletizer and drying at 70o C. The aqua-stability of feed pellets was determined by measuring the loss in weight of pellets soaked in water and the turbidity of water as Nephlometer reading (NMR). Among the starch sources tested, maida flour in combination with 2% guar gum in the feed imparted better aqua-stability to pellets followed by tapioca flour, rice flour, wheat flour and corn flour. Further increase in the level of guar gum in feed had no beneficial effect. It was observed that pellets containing guar gum rapidly swelled and developed cracks and these effects were higher with increase in guar gum level. Feed pellets containing wheat flour and tapioca flour showed highest Nephlometer reading (water turbidity), while pellets with maida flour showed the least NMR followed by corn flour and rice flour. While addition of 1% guar gum considerably reduced the NMR of tapioca flour and wheat flour, incorporation of 2% guar gum resulted in the least NMR reading of pellets with wheat flour and maida flour. However, further increase in guar gum (3%) has no beneficial effect. But raising guar gum level to 3% decreased the NMR reading in the case of tapioca flour and increased the NMR of rice flour and corn flour. Feed pellets of the same shrimp feed formulation containing wheat flour along with 2% guar gum and processed in a commercial scale ring-die pellet mill having three stage conditioners and steam injection facility, showed good water stability up to 4 hours (79.5 % stability).