PROTEIN ENRICHMENT OF CASSAVA WITH YEAST FOR CASSAVA FLOUR PRODUCTION

Abstract

Cassava flour (lafun), a processed product from cassava consumed in Nigeria as a staple food, is a major source of carbohydrate, though it is nutritionally inferior in terms of protein contents. This study investigated the use of yeast strains isolated from palm wine for the enrichment of cassava flour. A total of nine yeast strains were isolated on Potatoe Dextrose Agar (PDA) using pour plate method while four were selected based on their potentials to grow in cassava medium using ultra violet spectroscopy to determine the turbidity level at 600nm. The isolates were thereafter characterized using biochemical and molecular methods. The proximate composition, microbiological safety as well as sensory evaluation of the cassava flour samples were determined using standard methods. Four experimental setup of cassava were produced using the four organisms as monoculture which were inoculated with PDA broth containing 3.5× 102 - 4.5× 102 cfu/mL of the yeast cells while the fifth setup without organism served as control and were allowed to ferment for 3 days. Selected potential yeast isolates were identified using 16rRNA as Candida ethanolica (NR077165.1), (Pw2b), Candida ethanolica (NR077165.1) (Pw3b), Candida ethanolica (NR077165.1) (Pw4) and Sacchromyces cerevissiae (LC413771.1) (Pw6). Results of proximate composition revealed that cassava flour enriched with Candida ethanolica (No26) has the highest crude protein content of 2.54% compared with the crude protein of 1.74 % for commercial control. Uneriched cassava flour has the highest moisture and fat content of 15.07 % and 1.03 % while enriched cassava flour with Candida ethanolica (NR077165.1) (Pw3b) and Saccharomyces cerevisiae have the least values of 8.20 % and 0.56 % respectively. The crude fibre and ash content obtained for all the cassava flour samples ranged from 0.07 – 0.16 % and 0. 14 - 0.53 % respectively. The carbohydrate content of the commercial control (88. 41 %) was higher than all the values obtained for enriched (83.94 – 88.36 %) and unenriched (81.65 %) cassava flour. The microbial load for bacteria and fungi of the enriched and unenriched cassava flour ranged from 4×104cfu/g - 9×104cfu/g and 2×103 cfu/g - 8×103 cfu/g while the commercial control have bacterial and fungal load of 1.1×105 cfu/g and 9×103 cfu/g respectively. Microorganisms identified on all the cassava flour included Bacillus cereus, Bacillus mycoides, Staphylococcus aureus, Micrococcus luteus, Streptococcus sp, Aspergillus niger, Candida spp and Saccharomyces cerevisiae. Generally, there was good acceptability and organoleptic qualities (taste, aroma, colour, texture) in the protein enriched cassava flour when compared to the unenriched and commercial control cassava flour samples analyzed. This study suggests that cassava flour can be enriched with yeast strains to enhance nutritional quality.