The effect of pregelatinized potato starch on the functional properties of an extruded aquafeed.

The most important physical properties affecting quality in aquaculture feeds are floatability, hardness, stability and sinking velocity. An evaluation was done of the effect of different concentrations (25, 50, 75 and 100 g Kg-1) of native potato starch (PSt) and pregelatinized potato starch (PPSt) on functional properties in an extruded aquafeed. Maximum bulk density values were observed in the PPSt treatments, with a high value of 1.06 g cm-3 in the 25 g Kg-1 PPSt treatment. Hardness increased from 1.63 to 5.11 N in the PPSt treatments. Sinking velocity also increased, from 5.84 to 7.47 cm s-1, while water solubility index values decreased from 12.8 to 7.9%. Use of PPSt did not affect (P > 0.05) the expansion index, the water absorption index (g Kg-1) or color (L*, a* and b*). Addition of PPSt improved aquafeed pellet hardness without affecting the expansion index, preventing pellet disintegration and lixiviation of hydrosoluble nutrients. Of the tested concentrations, the optimum PPSt level was 100 g Kg-1 in fish meal (60%) based formulas.