Evaluation of selected binders in a ring-die pellet mill for processing shrimp feed pellets

Abstract

Polymethylolcarbamide (PMC), gura gum and wheat gluten were evaluated as feed binders in a ring-die (R–D) pellet mill at 0.5, 2.0 and 5.0% levels using a shrimp feed formulation. Pelleting of feeds was carried out at three different temperatures of 70, 80 and 90 oC. Highest increase in moisture level was recorded in the case of feed mix with wheat gluten as binder (20.9 – 26.0%), followed by the feed mix with guar gum (16.2 - 17.2%) and least increase in feed mix with PMC (11.4 – 12.6%). The results indicated that wheat gluten has the highest moisture absorbing capacity followed by guar gum and PMC has the least moisture absorbing property. The turbidity of water in which pellets with binder PMC were soaked resulted in lowest nephelometer reading (10.6 maximum). Pellets with wheat gluten resulted in higher values of turbidity (18.6 nephelometric units maximum) while those with guar gum as binder resulted in intermediate values of turbidity (15.3 nephelmetric units maximum) between PMC and wheat gluten. Pelleting temperature of 70, 80 and 90 oC improved hydrostability of pellets for all the three binders from 79.5 to 82% in the case of PMC, 80.5 to 81.5% in the case of wheat gluten and from 77.9 to 80.5% for guar gum. Pelleting temperature had no influence on water turbidity (10.6 – 10.8 nephelometric units) for pellets with binder PMC. Increase in pelleting temperature from 70 to 90 o C reduced the turbidity of water from 18.6 to 17.0 and from 15.3 to 14.9 nephelometer readings, in the case of wheat gluten and guar gum respectively. The drop in turbidity meter reading was more pronounced for wheat gluten than for guar gum. The results of the study indicates that PMC like synthetic binders are more suitable for processing shrimp feeds in ring-die pellet mill, which is required at very low level (0.5%), imparts good water stability to pellets and is also cost effective.