Effects of blanching and soaking on some physical characteristics of grass pea (Lathyrus sativus)

Abstract

Lathyrus sativus, containing a lathyritic principle, called β-ODAP (β-N-Oxalyl-L- α, β-diaminopropionic acid), is widely grown and consumed in Ethiopia. It is a hardy crop grown under various agro-ecological situations. The major drawback in the use of the legume is the fact that the seeds, in common with other legumes, are not easily rehydrated, are difficult to cook, the seed coat is difficult to remove and long cooking time is required by traditional processing methods for tenderization. In this study, the effect of processing methods like blanching, soaking and cooking on water absorption, leached solids, swelling power, cooking time and sensory qualities of grass pea seeds were investigated. The soaking solutions used were mixed with salt solution, wood ash solution and double distilled de-ionized water. Blanching significantly (p < 0.05) increased total water absorbed, swelling power, leached solids and reduced cooking time compared to unbalanced seeds. Soaking blanched seeds in salt or wood ash solution was noted to be most effective in promoting seed softening during cooking, compared to double distilled water. Blanched grass pea seeds soaked for 12 hours in the three soaking solutions caused reduction of 60%, 73% and 68%, respectively, in cooking time. In contrast, unblanched grass pea seeds soaked for 12 hours in the three soaking solutions caused reduction of 30%, 46% and 40%, respectively, in cooking time. Water absorption, swelling power and leached solids values were negatively correlated (p < 0.05) with the cooking time. The study results indicated that blanching and hydration of grass pea seeds improved the sensory characteristics of cooked seeds, significantly reduced the cooking time and increased the weight and texture of the cooked seeds. Application of blanching preceded by soaking at village level as an integral part of traditional methods of processing grass pea seeds, thus offers the dual advantage of saving of valuable fuels by shortening cooking time, as well as rendering the seeds more acceptable to consumers. In the absence of salt, wood ash suspension treatment may be a satisfactory alternative in the production of quick-cooking grass pea seeds.

Keywords: blanching, cooking, Lathyrus sativus, soaking

African Journal of Food, Agriculture, Nutrition and Development Vol. 6(1) 2006