Physico-chemical properties of potato starches

Starches were isolated and characterised from 10 potato cultivars grown under the same conditions (with a commercial starch for reference). The chemical composition revealed some differences amongst the starches with protein ranging from 0.30% to 0.34%, amylose 25.2% to 29.1% and phosphorus 52.6–66.2 mg 100 g⁻¹. High performance size-exclusion chromatography (HPSEC) fractionation of isoamylase debranched amylopectin showed that the amylopectin molecules were less branched and consisted of more B1, but less A-chains, than cereal starches. Gelatinisation onset (T_o), peak (T_p) and conclusion (T_c) temperatures of the native potato starches ranged from 58.7 to 62.5 °C, 62.5 to 66.1 °C and 68.7 to 72.3 °C, respectively, whilst the gelatinisation enthalpies ranged from 15.1 to 18.4 J g⁻¹. The gelatinisation temperatures of the starches increased in common with the amounts of short and intermediate sized amylopectin chains. The ¹³C magic angle spinning nuclear magnetic resonance (¹³C CP-MAS NMR) and wide angle X-ray diffraction (XRD) data (30.6% ± 0.22% crystallinity on average) showed little variance amongst the samples. Particle sizing results, however, revealed more variance (20.6–30.9 μm mean diameter). Overall, these data reveal the subtleties of cultivar specific variation against a background of constant environmental conditions.