Moisture Sorption in Seed Maize (Zea mays L.) During Hermetic Drying Using Super Absorbent Hydrogel

Abstract

The aim of this study was to establish the feasibility of using super absorbent hydrogel in drying of seed maize (Zea mays L.) under hermetic conditions. The study was conducted at the Jomo Kenyatta University of Agriculture and Technology (JKUAT). Seed maize was obtained from East African Seed Company Limited- Industrial area, Nairobi, while the super absorbent polymer, i.e., Poly-acrylic acid, sodium salt and lightly cross-linked used in the study was purchased from Sigma Aldrich

® Germany. The performance of hydrogel was evaluated based on three (3) treatments consisting of 1:5, 1:10 and 1:15 hydrogel to seed maize ratio by weight dried under different seed drying temperatures of 25, 30, 35 and 40 o C and initial moisture content of 16, 28 and 53% (d.b); the control did not utilize any hydrogel. The results were analyzed using Analysis of Variance (ANOVA) in order to determine whether there existed significant differences within the drying rate of the different treatments, and also from the control. Modeling was done using non-linear regression analysis (MS Excel 2003 TM ) based on the minimization of sum of squares by adjusting the model constants. The coefficient of determination (R 2 ), the Chi-square (χ mean-square error (RMSE) were used to evaluate the goodness of fit of the five (5) tested mathematical models to the actual data. The models considered for this study were Page, Two term exponential, Newton, Logarithmic and Henderson and Pabis model. The viability of seed maize was evaluated by performing germination test to 2 ) and the root-determine the maximum germination potential of a seed lot after drying using superabsorbent hydrogel under hermetic conditions for different treatments.

The moisture content of seed maize was recorded after seven days of drying with each set of treatment having reduced seed moisture content. A ratio of 1:5 seed maize to hydrogel by weight and drying temperature of 40 o C the moisture content of seed maize reduced by 31.1, 15 and 4% for initial seed moisture contents of 53, 28 and 16% (d.b) respectively. The ANOVA results showed that at 1% significance level there were highly significant differences between the final moisture content attained for the drying temperature, ratio and temperature ratio interaction (p < 0.001). High values of coefficient of determination (R models while the corresponding values of χ 2 > 0.95) were obtained for all the five drying 2 and RMSE were in the range of (0.0016- 0.0141) and (0.0400-0.3045) respectively. As a result Logarithmic model was the best fitted model with R 2 (0.9749-0.9876) and the weakest values of χ 2 (0.0016-0.0036) and RMSE (0.04-0.128). Seed drying using hydrogel did not alter seed viability as germination test results revealed germination rates as high as 86.5%.

The results of this study illustrate that hydrogel can be used as a potential desiccant for drying seeds while maintaining their viability.