Evaluating the Effects of Sweet Potato Varieties on Flour Quality

Sweet potatoes are a highly nutritious food
group, they continue to gain interest on account of the
diversity of the tuber and the number of products that
can be developed from the tuber itself. This is true on the
global scale, however; locally the amount of such
products on market is minimal. Such should be available
to cater to gluten intolerant and celiac disease niches and
also exhaust the favorable SP production cycle. The
overall purpose of this study is to determine the best
variety and treatment for flour production, for use in the
formulation of a sweet potato based instant porridge.
Seven varieties of sweet potato tubers: Chingovha (white
flesh), Delvia (orange flesh), Irene (yellow flesh), Victoria
(orange flesh), Namanga (orange flesh), Alicia (yellow
flesh) and Tsumaya (pale yellow flesh) were harvested at
physiological maturity and processed to flour on a labbased pilot via thermal processing. The fresh tubers
were washed, sliced and treated with Ascorbic acid to
prevent browning. Following ascorbic acid
pretreatment; for treatment 1 fresh tubers were dried
immediately, slices for treatment 2 were parboiled for 10
minutes before drying whilst slices for treatment 3 were
fermented prior to drying for 1-3 days in 5% brine and
1% sucrose solution. Post-drying: the slices were ground
to fine powder and the flour product assessed on both
functional and physiochemical properties with particular
emphasis for use in instant porridge formulation. A
Randomized Block Design was used for the experiment
while sensory evaluation wase used to determine product
acceptability. The product was assessed according to
flour quality (color, emulsification stability, oil and
water holding capacity, foreign matter and moisture
content), treatment effect (before and after processing
based on protein content, starch content, phenolic
content, gluten content, Beta carotene content). Together
these parameters determined that the ideal mode of
treatment for flour production was fermentation in that
it exhibited the least nutritive reductive effect across all
varieties. There were significant differences (p-value)
between varieties with respect to flour quality amongst
oil and water holding capacities, moisture content but
not for emulsification stability. The most ideal treatment
was fermentation in that amongst the analyzed
parameters; the greatest nutrient retention was observed
for fermented samples. Tsumaya was observed to
produce favorable samples for all treatments. Sensory
evaluation established that fermentation was a favored
pretreatment option whilst Victoria, Tsumaya and
Chingovha were amongst the popular varieties and as
such should be formulated into sweet potato based
instant porridge.