Microbiological characteristics and deteriorative changes of ‘k woka’ (a nigerian non‐fermented maize dish) produced using potassium sorbate and various steaming treatment

‘Kwoka’ (a popular Nigerian non-fermented maize meal) was produced using steaming for either 30 or 60 min or a combination of potassium sorbate (KS) treatment with steaming for 60 min. Microbiological characteristics and chemical quality were investigated during production and storage, together with organoleptic and objective (firmness only) assessment of quality during ambient storage (30 ± 2°C). The slurry (ie before steaming) and 30 min steamed K woka showed more diverse genera of moulds and bacteria than K woka steamed for 60 min (with or without KS). The organisms isolated from the raw materials and product belonged to the genera Bacillus, Staphylococcus, Lactobacillus, Enterobacter, Klebsiella, Aspergillus and Fusarium. During storage Bacillus cereus, Lactobacillus delbrueckii, L leichmannii and Klebsiella pneumoniae predominated. Coliforms and fungi were not detected on day 0 in KS-treated and 60 min steamed K woka. Marked reductions in aerobic plate counts (APC) and in the population of the different bacterial groups were observed in all samples following steaming, These increased sharply within 1 day of storage, the highest (6.50 log cfu g−1) APC occurring on day 3 in 30 min steamed K woka. Of the bacterial groups, the Lactobacillus population increased most markedly and this probably reflects the significant increase in acidity observed especially on day 6. Adverse quality changes in appearance, aroma and firmness were more apparent in the control (ie without KS treatment) and the samples were unacceptable after 1 day but the shelf-life of K woka produced using KS treatment and 60 min steaming was extended by 2 days.