Molecular causes for the effect of cooking methods on rice stickiness: A mechanism explanation from the view of starch leaching.

Microwave, electronic pressure cooking (EPC), and water absorption method are the common but different ways used for cooking rice. To explore mechanisms for effects of cooking methods on rice stickiness, starch leaching behaviour and the fine structure of leached starch are investigated. We find: (i) EPC improves starch leaching, i.e. the highest amount for total solids and leached amylopectin (AP), while microwave restricts starch leaching; (ii) the chain-length distributions (CLDs) of leached AP between rice samples are similar while CLDs of leached amylose (AM) are mainly ranged between degree of polymerization (DP) 100 and 1000; (iii) microwave makes rice leaching more long-AM chains with DP 1000-10,000; (iv) the varied stickiness of differently cooked rice are mainly caused by total amount of leached materials, especially leached AP, rather than the molecular structure of leached starch. This mechanism explanation provides better view towards helping consumers improve cooking and eating quality of cooked rice.