Flour and starch were produced from 11 cassava genotypes. Starch and total dietary fiber contents were determined using a single-enzyme gravimetric procedure and high-performance anion exchange chromatography, pasting profiles by rotary viscometry, water holding capacity gravimetrically, and granular characteristics by scanning electron microscopy. Starch and total dietary fiber contents varied among genotypes. Flour peak viscosities, setback, and final viscosities differed significantly. Flour water holding capacity correlated with flour peak viscosity (r = 0.7). Starch granules ranged from 9 to 20 mm. Predominant granule shapes were oval, rounded, and truncated. The results provide insights into cassava genotype characteristics, and functionality of cassava starch and flour.

Interlaboratory performance statistics was determined for a method developed to measure the resistant starch (RS) content of selected plant food products and a range of commercial starch samples. Food materials examined contained RS (cooked kidney beans, green banana, and corn flakes) and commercial starches, most of which naturally contain, or were processed to yield, elevated RS levels. The method evaluated was optimized to yield RS values in agreement with those reported for in vivo studies. Thirty-seven laboratories tested 8 pairs of blind duplicate starch or plant material samples with RS values between 0.6 (regular maize starch) and 64% (fresh weight basis). For matrixes excluding regular maize starch, repeatability relative standard deviation (RSDr) values ranged from 1.97 to 4.2%, and reproducibility relative standard deviation (RSDR) values ranged from 4.58 to 10.9%. The range of applicability of the test is 2–64% RS. The method is not suitable for products with <1% RS (e.g., regular maize starch; 0.6% RS). For such products, RSDr and RSDR values are unacceptably high.

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Maize flour, potato flour, cocoyam flour, plantain flour, yam flour, and rice flour were assayed for starch digestibility by an established enzymatic procedure. These were either autoclaved, microwaved, or parboiled and then freeze-dried. Freeze-dried samples were stored for 10 days either below freezing or at ambient temperature. Parameters assessed were readily digestible starch (RDS), slowly digestible starch (SDS), and total starch (TS). Data was analyzed by t-test (P < or = 0.05). RDS levels among raw flours ranged from 1.01 g/100g in rice flour to 8.16 g/100 g in cocoyam flour. Autoclaving and parboiling increased RDS levels in most flours, while microwaving significantly reduced RDS compared with raw flour. Ambient temperature storage reduced the RDS content. SDS levels ranged from 4.95 g/100 g in yam flour to 22.2 g/100 g in maize flour. SDS levels were increased by autoclaving and parboling, but significantly reduced by microwaving, compared with the raw flour. Storage at ambient temperature resulted in lower SDS. The TS content in raw flour ranged from 28.0 g/100 g in plantain flour to 68.4 g/100 g in rice flour. Autoclaving resulted in reduced TS levels insome flours. Moist heat processing and the post-process storage temperature therefore result in significant changes in starch susceptibility to enzymic digestion. This information will be useful in developing food processing and storage procedures that modify starch resistance to digestion in order to optimize its nutritional quality and to enhance the physiological benefits.

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