Development and application of an automatic system for determining seed volume kinetics during soaking

Soaking is an important unit operation during the processing of seeds used for direct consumption. The change in seed volume over time during soaking (volume kinetics) relates to water uptake and the quality of final product, and affects the design of the entire processing operation. Since volume determination is labor-intensive and time consuming, volume kinetics is usually not well monitored throughout seed hydration. The first chapter of this thesis is a review on the importance of soaking and volume kinetics monitoring during seed processing, the factors affecting hydration in seeds, current volume measurement methods and models used to determine and describe the change in volume over time in seeds during soaking. The second chapter describes the design, construction and evaluation of a bean volumetric auto tester (B-VAT) for volume kinetics determination of seeds during soaking. Evaluation tests suggested the system can generate reliable, reproducible, and detailed volume kinetics results for seeds soaking at different conditions with limited labor requirements. In the third chapter, the volume kinetics of 6 pinto, 5 navy and 3 black bean cultivars were tested during soaking at 25 ºC and 55 ºC. Significant differences were observed among varieties and cultivars at both temperatures (p<0.01). As temperature increased, the hydration efficiency were enhanced for all cultivars, but with various degree. In the fourth chapter, we tested the hypothesis that a thin hydrophobic layer on the seed coat was responsible of the extended initial lag phase observed during the soaking of pinto beans. Hexane pre-treatment before soaking were used for all cultivars and contact angle measurement were done to determine the surface hydrophobicity of the beans. Good correlations were found between surface hydrophobicity and hydration efficiency of beans. Hexane effectively reduced the hydrophobicity of bean surface and improved the hydration efficiency of pinto beans. The fifth chapter covers the overall conclusion of this study and states recommendations of future work regarding the improvement of the developed system and further exploration of the bean hydration process.