Effects of supercritical fluid extraction on Curcuma longa L. and Zingiber officinale R. starches

Ginger and turmeric tubers have approximately 45 and 40% of starch, respectively. These starches were analyzed before and after ginger and turmeric were subjected to supercritical fluid extraction to obtain oleoresin and essential oil. The starches were isolated and analyzed with respect to purity, amylose/amylopectin content, X-ray pattern, viscosity, swelling factor, granule morphology by scanning electron microscopy, gelatinization temperature by differential scanning calorimetry and turbidity. Supercritical fluid extraction process did not alter the starchy matrix showing small physical rearrangement of the starch molecules; this effect was more intense in the ginger starch, as observed by X-ray diffraction. The ginger starch became less resistant, in other words, there was a starchy structure relaxing after supercritical fluid extraction, evidenced by the lower setback value in the gelatinization process and nonetheless, it did not alter the granule morphology as observed by microscopy. This study reveals similar characteristics of these starches with commercial starches, indicating their potential for industrial applications.