Effect of sodium alginate on the gelatinization and retrogradation properties of two tuber starches

Background and objectives: The inherent properties of native starches are undesirable for the industrial applications because of the high tendency of retrogradation. Tuber starches are widely used in starchy foods. However, the gelatinization and retrogradation properties of tuber starches are not much known. This study mainly investigated the gelatinization and retrogradation properties of two tuber starches, potato starch (PS) and sweet potato starch (SPS), with or without the addition of sodium alginate (AG), using rapid visco analyzer, texture analyzer, differential scanning calorimeter, dynamic rheometer, and X-ray diffractometer. The AG-starch mixture gel was stored at 4 degrees C for 1-21days. Findings: The results showed that the addition of AG increased the gelatinization temperature of the two tuber starches, suggesting the gelatinization process was delayed by the addition of AG. The addition of AG obviously decreased the setback (SB) value, while increased the tan values of the two tuber starches. This suggested that addition of AG could retard the short-term retrogradation of starch. AG also significantly reduced the gel firmness, retrogradation ratio, and relative crystallinity of the two tuber starch gels during storage, indicating that the long-term retrogradation was retarded with the addition of AG. Meanwhile, the retrograded starch with or without the addition of AG showed B-type crystallinity pattern. Although PS contains phosphate groups, AG exerted a similar effect on the retrogradation of PS and SPS. Conclusions: Results suggest that the addition of AG could retard the retrogradation and delay the gelatinization process of the two tuber starches. Significance and novelty: This result can provide available information about the interactions between negative polysaccharide and negative/neutral starch, which also can provide an effective method to retard the starch retrogradation.