ESTIMATION OF SHELF LIFE OF AMBIENT STORED FLOUR FROM SELECTED FOOD CROPS

Ojo Oladimeji George
Food Science and Technology, Federal University of Agriculture, Abeokuta
October, 2014
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Abstract

Data on the shelf lives of indigenous particulate products are very scarce in literature. This study there was designed to determine the shelf lives of flours from eight indigenous crops (sweet potato, cocoyam, ginger, cassava, rice, maize, soy bean and Bambara nut) as using a controlled ambient storage conditions (27±2°C, 92% RH). Samples were stored in low density polyethylene (LDPE) and were analysed for moisture content and colour changes at interval during storage. The water vapour permeability coefficient of LDPE used was determined as 1.708×10-14 g.mm/d/mmHg Moisture sorption isotherm, calculation and verification of shelf life for the flours were determined. The moisture sorption of the flour products was more rapid in the initial stages with lesser amount of moisture adsorbed as time increased. Moisture contents of the flour ranged from 3.84 to 10.44%. Soy bean flour had the highest rate of moisture gain followed by Bambara nut, ginger, sweet potato, maize, rice, cocoyam and cassava flour. The higher the relative humidity used, the more pronounced the effect. The sigmoidal moisture sorption isotherms of all the flour products can be classified as type II. Peleg model fitted the experimental data to an accuracy of 83-99%. The percentage root mean square error (%RMSE) was used to show the quality of model fitting. In terms of colour stability, redness (a*) changed more rapidly across all flour samples while Lightness (L*) was the most stable. Stability of L* values was least for rice flour while maize flour the greatest L* stability. The estimated shelf lives of the flours stored at 92% RH and 27±2°C ranged from 97-172 days depending on initial moisture contents.