Studies on the morphological, thermal and rheological properties of starch separated from some Indian potato cultivars

The starches separated from five different Indian potato cultivars (Kufri Chandermukhi, Kufri Badshah, Kufri Jyoti, Kufri Sindhuri and S1) were investigated for morphological, thermal, rheological, turbidity and water-binding properties. The starch separated from all the five potato cultivars had a granule size ranging between 15-20 mum and 20-45 mum. The shape of starch granules varied from oval to irregular or cuboidal. Starch isolated from cv. Kufti Badshah had largest irregular or cubiodal granules while starch from cv, Kufri Chandermukhi had small and oval granules. The transition temperatures and enthalpy of gelatinization (DeltaH(gel)) were determined using differential scanning calorimetry (DSC). The enthalpy of retrogradation (DeltaH(ret)) of gelatinized starch was also determined after 14 days of storage at 4 degreesC using DSC. Kufri Chandermukhi starch showed the lowest DeltaH(gel) and DeltaH(ret) while Kufri Badshah starch showed the highest values. DeltaH(gel) and DeltaH(ret) values of 12.55 J/g and 6.42J/g, respectively, for Kufri Chandermukhi starch against 13.85 J/g and 8.61 J/g, respectively, for Kufri Bhadshah starch were observed. Rheological properties of starches from different potato cultivars, measured using the Dynamic Rheometer during heating and cooling, also differed significantly, The starch from cv. Kufti Badshah showed the highest peak G' and G and lowest tan delta. The starches having higher peak G'(G' at gelatinization temperature) showed higher breakdown in G' and vice versa. The turbidity of gelatinized aqueous starch suspensions from all potato cultivars increased with increase in storage period. Starches with low water binding capacity had higher G' and G and lower tan delta values. (C) 2001 Elsevier Science Ltd. All rights reserved.