Physico-chemical characterisation of sage starch

The physico-chemical characteristics of various sage starch samples from South East Asia were determined and compared to starches from other sources. X-ray diffraction studies showed that all the sage starches exhibited a C-type diffraction pattern. Scanning electron microscopy showed that they consist of oval granules with an average diameter around 30 mu m Proximate composition studies showed that the moisture content in the sage samples varied between 10.6% and 20.0%, ash between 0.06% and 0.43%, crude fat between 0.10% and 0.13%, fiber between 0.26% and 0.32% and crude protein between 0.19% and 0.25%. The amylose content varied between 24% and 31%. The percentage of amylose obtained by colourimetric determination agreed well with the values obtained by fractionation procedures and potentiometric titration. Intrinsic viscosities and weight average molecular weight were determined in 1M KOH. Intrinsic viscosity for amylose from sa,oo starches varied between 310 and 460 ml/g while for amylopectin the values varied between 210 and 250 ml/g. The molecular weight for amylose was found to be in the range of 1.41 x 10(6) to 2.23 x 10(6) while for amylopectin it was in the range of 6.70 x 10(6) to 9.23 x 10(6). The gelatinisation temperature for the sage starches studied varied between 69.4 degrees C and 70.1 degrees C. The exponent 'a' in the Mark-Houwink equation and the exponent 'alpha' in the equation R-g = kM(alpha) was found to be 0.80 and 0.58, respectively for amylose separated from sage starch and these are indicative of a random coil conformation. Two types of pasting properties were observed. The first was characterised by a maximum consistency immediately followed by sharp decrease in consistency while the second type was characterised by a plateau when the maximum consistency was reached. (C) 1999 Elsevier Science Ltd. All rights reserved.