Effects of Shred Size, Storage Type and Age of Cassava on the Equilibrium Moisture Content (EMC) of Shredded Cassava Samples at 0.17 Water Activity Using Response Surface Analysis

Abstract

This research investigates the effects of shred size, storage types and age of cassava on the equilibrium moisture content (EMC) of shredded cassava samples at 0.17 water activity using response surface methodology. Peeled roots of TMS30572 cassava specie at three levels of maturity 6, 12 and 18 months were washed and steamed for 20-30 minutes. The steamed roots were allowed to cool for 12 hours. The cooled roots were shredded using a machine developed for the purpose.  Three different shredding disc apertures of the machine 3, 6 and 10mm were used. The shredded samples produced were washed shortly after shredding and dried in the open direct sun for 3 days with occasional turning of the flakes to ensure uniform drying. The dried, edible brittle cassava flakes were packaged each in cellophane bags, Bagco sacks and baskets and stored for 12 weeks at room temperature. Equilibrium moisture contents (EMC) of samples were determined by allowing the dry samples to absorb moisture in an atmosphere of controlled humidity until a constant weight was reached at 0.17 water activity. Response Surface Methodology was used in the design of the experiments. Results of the regression and ANOVA of the data on the EMC of cassava shreds showed that none of the studied variables had significant effects (P ≤ 0.05). The variables accounted for only 35.3% of the total variation of the EMC.  The response surface plots show that the EMC decreased with the age of the cassava samples, also the EMC increased with the shred size of the cassava shreds. This shows that the smaller the shred size of the sample, the slower the rate of its moisture absorption and the better the keeping quality. The EMC also increased as packaging material moved from Bagco sack to basket.