Physico-chemical characterisation of sage starch

The physico-chemical characteristics of various sage starch samples from So uth East Asia were determined and compared to starches from other sources. X-ray diffraction studies showed that all the sage starches exhibited a C-t ype diffraction pattern. Scanning electron microscopy showed that they cons ist of oval granules with an average diameter around 30 mu m Proximate comp osition 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 va lues obtained by fractionation procedures and potentiometric titration. Int rinsic viscosities and weight average molecular weight were determined in 1 M KOH. Intrinsic viscosity for amylose from sa,oo starches varied between 3 10 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 1.4 1 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 starc hes 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 sepa rated from sage starch and these are indicative of a random coil conformati on. Two types of pasting properties were observed. The first was characteri sed by a maximum consistency immediately followed by sharp decrease in cons istency while the second type was characterised by a plateau when the maxim um consistency was reached. (C) 1999 Elsevier Science Ltd. All rights reser ved.