INVIVO AND INVITRO DIGESTIBILITY OF STARCH IN AUTOCLAVED PEA AND POTATO PRODUCTS

The digestibility of starch in homogenized/autoclaved pea plus potato products was studied in vitro and in vivo. The products were a canned infant puree based on peas and potatoes and products prepared in the laboratory by repeated autoclaving and cooling of either homogenized potatoes or homogenized peas. Small-intestinal digestibility was evaluated through balance experiments in rats treated with an antibiotic (Nebacitin) to supress microbial activity in the hind gut. Parallel experiments in normal rats were performed to study the fermentability of undigested starch. The small-intestinal digestibility was 93, 82 and 70% of total starch in the potato product, infant puree and pea product, respectively. Consequently, significant amounts of starch left the small intestine undigested, particularly with pea-based products. The major portion of the undigested starch consisted of a fraction which resisted amylases in vitro unless solubilized in alkali, ie retrograded amylose. The fermentability of starch reaching the hind gut was high, about 90%. In-vitro digestibility figures varied depending on the method used and were in the ranges 91-93, 76-86 and 71-77 % in the potato product, infant puree and pea product, respectively. One of the methods allowed simultaneous and accurate determination of the in-vivo resistant retrograded amylose fraction.