Impact of process strictures on the composition and sorption isotherms of Bambara nut flour using RSM

Abstract

The global concern for the diversification of the uses of plant foods to improve normal and the paretic nutrition for diabetes control has shifted research interest to enhancing the potential sources of beneficial constituents in plant foods. Studies have shown that the fibre and protein contents of Bambara nut can weaken the absorption of sugar, reduce sugar response and increase insulin sensitivity and therefore recommended as a supplement for type II diabetes. Diabetic patients in Nigeria rely on Bambara nut flour as food because of its insulin building ability in the body system, but the challenge is its unavailability all the year round in the market outlets when needed. Presently, there is paucity of information on the storage techniques of Bambara nut flour that can prolong the shelf-life for later usage. Experimental research design method was adopted. Bambara nut was sourced and milled to flour, stored in a room temperature (28-32°C) for 6 months. Particle size distribution using sieve analysis was carried out to separate the flours at particle size levels 20, 40, 60, 80 and 100 mesh numbers (850, 425, 250, 180 and 150μm) as designed in the face central composite design (FCCD) response surface methodology of Design Expert 7.0.0 software. Moisture sorption characteristic of the flour was determined. The effects of particle size and storage duration on the proximate composition of the flour were investigated. The data obtained were analyzed using the Design-Expert software (Version 7.0.0, Stat-Ease Inc., Minneapolis, USA). The experimental data generated was fitted to a polynomial regression model for predicting maximum shelf-life. In order to correlate the response variables to the independent variables, multiple regressions were used to fit the coefficient of the polynomial model. The quality of fit of the model was evaluated using analysis of variance (ANOVA). The suitability of the models was compared and evaluated using correlation coefficient (R2). The results obtained from the study showed that storage duration had effect on the proximate composition of Bambara nut flour. The flour particle size had effect on the proximate composition. The time for the flour to reach equilibrium varied from 6 – 14 days. The results obtained in the study showed the response surface model employed is a good one. The model correlation coefficient (R2) of the responses was found to be 0.9701, 0.9688 and 0.9138 for the flour ash, protein, and fibre contents, respectively. Levels of significance obtained were 0.02, 0.03 and 0.03 for the flour ash, protein and fibre contents which were high and attested to the fitness of the model in evaluating the responses. Optimum particle size, moisture content and storage time were found to be 150.12μm, 6.32% (wb), and 23.62 weeks.