Selection of lactic acid bacteria for use as starter cultures in Lafun production and their impact on product quality and safety

Abstract

Lafun is one of the fermented cassava products of West Africa. However, current production systems, which use spontaneous fermentation, result in variable product quality and reduced safety. Therefore, there is an interest in developing a manufacturing process to overcome these challenges. An important element that could resolve the above issues is the use of starter cultures. Therefore, this thesis focuses on the selection of lactic acid bacteria (LAB) from fermenting cassava that have potential use as starter cultures for lafun production and explores their impact on final product quality and safety. Lactic acid bacteria isolates (n=41) from spontaneous fermentation of cassava were characterised and screened for flavour compounds production. Four strains were identified as having the greatest potential use as starter cultures (n=4) and were genotypically identified as Weissella koreensis (2 strains), Lactococcus lactis and Leuconostoc mesenteroides. These four strains were further screened for antibiotic resistant genes and did not seem to contain any such genes. Following starter culture addition, subsequent processing operations may impact on lafun flavour. Therefore, fermentation time and drying of lafun were investigated to enhance the laboratory production of lafun. Acidification rate of the selected isolates was also assessed to also identify possible starter culture combinations where one strain is a strong acidifier while the other enhances flavour. The impact of the developed starters, singly and in combination, on lafun nutritional quality, rheological properties, volatile flavour profile, NMR metabolite profile, cyanide reduction and microbial load was evaluated. Three cassava varieties (Bitter: IBA30527; Fortified: IBA011371; and Sweet: TMEB117) were fermented, in duplicate, to produce samples for analyses. Fermentation for 48 h without pressing the fermented cassava roots favoured the yield of desirable flavour compounds. The results support the adoption of fortified cassava for lafun production due to its positive flavour, nutritional and physical properties.