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In vitro starch hydrolysis by pancreatin and amyloglucosidase, has been used to determine nutritionally-important starch fractions [rapidly available starch (RDS), slowly digestible starch (SDS) and resistant starch (RS)] in flours and starch isolates from plantain, and to study the changes which occur to these fractions with increasing temperature. There was virtually no RDS observed in ripe plantain flour at 40 - 45oC and only ~ 1 ± 0.6% (n = 3), of RDS between 50 - 65oC. Marked increases in RDS were observed between 65 and 70oC for all the samples except in ripe plantain flour where this increase was spread over a broader range of temperature i.e. between 65 - 75oC. RS values were significantly different for all samples between 40oC and 55oC with flours showing higher values of RS than the starch isolates. At 60oC and p ≤ 0.05, the starches have RS values that are not significantly different from each other (22.3 ± 1.8% and 21.3 ± 1.4%) and flours have values not significantly different from each other (89.1 ± 0.4% and 89.5 ± 0.4%). High values of SDS were observed on enzyme digestion of starches, while flours had higher values of RS and RDS than starches. The results obtained indicate that some constituents of plantain flour may interfere with the hydrolysis process, leading to higher values of RS, and lower RDS when compared to the starch isolates. This observation is, however, dependent on treatment temperature.
Keywords: Plantain, starch, flour, bioavailability