Structure and physicochemical properties of palmyrah (Borassus flabellifer L.) seed-shoot starch grown in Sri Lanka

Starch from palmyrah (Borassus flabellifer L.) seed-shoot flour was isolated and its composition, morphology, structure and physicochemical properties were determined. The yield of starch was 38.4% on a whole flour basis. The shape of the granule ranged from round to elliptical. Bound lipid, total lipid, apparent amylose, total amylose and resistant starch contents were 0.03%, 0.04%, 30.9%, 32.7% and 32.2%, respectively. The X-ray pattern was of the A-type and relative crystallinity was 34.1%. Palmyrah starch exhibited a high proportion (31.8%) of short amylopectin chains (DP 6–12) and a low proportion (1.2%) of long amylopectin chains (DP > 36). Gelatinization temperatures were 73.1–82.0 °C and enthalpy of gelatinization was 13.6 J/g. Pasting temperature, viscosity breakdown and set-back were 76.5 °C, 147 and 74 BU, respectively. Palmyrah starch exhibited high granular swelling, and restricted amylose leaching. Susceptibility towards in vitro α-amylolysis and retrogradation was low. The results showed that physicochemical properties of palmyrah starch were largely influenced by strong interactions between amylose–amylose and/or amylose–amylopectin chains within the granule interior.