Optimization of Protein Extraction from Arachis hypogaea L. and Cucumeropsis mannii Naud. Seeds for Use as Natural Coagulants in Surface Water Clarification

The aim of this study was to improve the quality of protein extracts from Cucumeropsis mannii Naud. and Arachis hypogaea L. The evolution of protein content and microbiological quality of aqueous extracts of A. hypogaea, C. mannii and M. oleifera seed powders were monitored over time during protein extraction. The protein contents of the extracts subjected to decantation and those subjected to centrifugation were determined by the Kjeldahl method. The microbiological quality of the different aqueous extracts was evaluated according to the standards NF EN ISO 7932, NF V 08-059 and NF EN ISO 4833-1. The results obtained show protein contents of 40.6 % for A. hypogaea, 25.4 % for C. mannii and 36.5 % for M. oleifera, after 24 h of decantation. The protein contents of the centrifuged aqueous extracts were higher and 55.9%, 36.7% and 37.6% for A. hypogaea, C. mannii and M. oleifera extracts respectively. The results of the microbiological analysis showed that the aqueous extracts of M. oleifera contain little microbial load. Significant growth of aerobic flora and Bacillus cereus was observed in the decanted extracts of C. mannii and A. hypogaea from 4 h to 24 h of decantation. Extracts obtained by centrifugation have a lower microbial load, because the treatment time was shorter. The aqueous protein extracts of A. hypogaea and C. mannii seed powders obtained by centrifugation were of better quality than those obtained by decantation, because they have higher protein contents and lower microbial loads. The water solubility of A. hypogaea and C. mannii seed proteins was also studied on protein suspensions at 2% at pH 3, 4, 5, 6, 7 and 8. The results obtained showed that adjusting the pH to 7 and 8 could improve the degree of protein extraction for A. hypogaea and C. mannii seeds.