Effect of Fatty Acids ( Myristic and Palmatic Acids ) on the Rheological Properties and Swelling Power of Sago Starch

Effect of fatty acids such as Myristic and Palmatic acids, on the rheological properties of sago starch during heating and cooling were studied using a dynamic rheometer, Haake Rotovisco RT20. Fatty acids were applied at 0.5% and 0.1% levels on the starch weight basis( 20% w/w). The gelatinization temperature ( TG' ) of sago starch dispersion was determined at 68.4 o C. The addition of both fatty acids inhibited the swelling of the starch and then caused an increase in TG' compared to the native starch. The storage modulus (G') increased to a maximum value and dropped during heating of the starch. The reduction of peak G' value was 737 900 Pa. The extent of breakdown in G' during heating was high without addition of fatty acids. Hence the G' values of sago starch increased on cooling as well with the addition of fatty acids. The peak loss tangent (tan δ) reached a maximum value at 2.728 and then dropped on heating. In contrast, during cooling the loss tangent values decreased. Swelling behaviour of sago starch granules with and without fatty acids was studied. As a result, the addition of Myristic acid to the sago starch decreased the swelling power values (SP) rather than the Palmatic acid .