Improving effect of lyophilization on functional properties of resistant starch preparations formed by acid hydrolysis and heat treatment

In this study, effects of lyophilization on the functional properties of acid modified and autoclaved corn starch preparations were investigated. RS contents and pasting properties of these starch preparations were also determined. Significant increases in solubility were observed as the hydrolysis level of the lyophilized samples increased. All of the acid-modified gelatinized–autoclaved–lyophilized samples had higher water binding values than those of native starch and heat treated oven-dried native starch. Acid-modified gelatinized–autoclaved–lyophilized samples (with storage at 95°C: GASL or without storage: GAL, before lyophilization) improved emulsion properties of soy protein solution significantly. Acid modification seems to be a prerequisite to achieve improving effect of lyophilization. While native starch did not contain any RS, the level increased to 8.1% due to gelatinization, autoclaving and oven-drying (Control 2). The RS content of Control 2 was higher than that of gelatinized–autoclaved–lyophilized native starch (N-GAL, 2.9%). The samples stored prior to lyophilization had higher RS contents as compared to the corresponding unstored samples. The highest RS content (12.4%) was observed in 2h-GASL sample. Cold viscosity was observed in the RVA curves of N-GASL, 2h-GASL, N-GAL and 2h-GAL samples. A possible mechanism/model is suggested to explain the lack or existence of a cold viscosity.