Abstract:

The effects of four different cooking methods on protein digestion properties of cooked rice from three varieties
were studied by a sequential pepsin-trypsin digestion method. Cooking methods (P1, mechanically adopted cookingsteaming-
boiling; P2, computer-aided cooking-steaming-boiling; P3, high pressure-adopted cooking-steaming-boiling and
P4, micro-pressure-adopted cooking-steaming-boiling) and three varieties of rice (indica rice THXM, Japonica rice JJGM,
and indica rice JZX) were found to exert significant but different effects on protein digestion properties of cooked rice.
Lower-intensity boiling provided the highest protein digestibility (81.64%－93.80%) and free amino acid (FAA) content
(2.10 g/100 g pro－2.21 g/100 g pro). Both protein digestibility and FAA content were decreased by increasing boiling time
or adopting pressure-cooking. Lysine was decreased more significantly and the amino acid score was lower. The effects of rice
varieties on protein digestion properties might be related to the enzymatic hydrolyzability and composition of rice proteins.

Key words: rice, protein, digestion, cooking model, amino acid