The effects of gelatinization and gel storage conditions on the formation of canna resistant starch (RS) were investigated. Starch slurries (10%, dwb) were autoclaved at 121 °C for 30, 60, and 120 min. The gels obtained were subsequently stored at different temperatures (4 °C, 30 °C, and 100 °C) and times (0, 1, 3, 5, and 7 days). Analyses of the RS content in gelatinized starch samples in comparison with that in granular starch showed that the RS fraction in granular starch was very high (97.3% w/w); however, nearly all of the RS was thermally unstable, as indicated by a great reduction in RS content (to 1.9% w/w) after cooking at 100 °C for 20 min. The RS contents in gelatinized starch samples were 12.0–15.9% w/w, which were reduced to 7.9–10.8% w/w after cooking. Storage of gels resulted in a significant increase in the amount of the thermally stable RS fraction, e.g., a thermally stable RS content of 16.8% w/w was found in the gel sample gelatinized for 120 min and stored at 4 °C for 3 days. This indicated that the ordered structures of the RS portion were tightened under the storage conditions. The gelatinization temperature of canna starch was 72.2 °C, whereas the RS products exhibited two melting temperature ranges, 51.1–76.3 °C and 163.1–165.1 °C, indicating that the newly formed crystals were very strong.
Resistant starch; Canna starch; Gelatinization; Retrogradation; Storage