Investigating the microbiological profile of motoho, a fermented sorghum beverage

Abstract

Motoho is a fermented, non-alcoholic sorghum beverage or porridge manufactured by the Sotho people of South Africa. It is readily consumed, daily or weekly by the entire family however little information is available with regards to the microorganisms responsible for the fermentation of motoho. Motoho is produced by spontaneous fermentation and the resultant product has inconsistent microbiological and sensory qualities. This presents a challenge to large-scale production of motoho. The use of starter cultures could present a possible means of bypassing these drawbacks, however, in order to effectively up-scale the production of motoho, it is imperative to identify the microorganisms associated with the fermentation process before making use of potential starter cultures. This study therefore aimed to employ both phenotypic and genotypic methods to investigate the microbial populations associated with the production of motoho by a traditional method as well as a modified method, and also to assess the effects of the different methods on the nutritional and sensory attributes of motoho. Putative lactic acid bacteria (LAB) and yeasts were isolated using culture dependent methods. These microorganisms were then identified using PCR screening as well as MALDI-TOF which confirmed the presence of the following LAB and yeasts during the production of motoho using both production methods: Lactobacillus fermentum, Lb. plantarum, Lb. coryniformis, Lb. paracasei, Candida glabrata, C. lambica, C. pelliculosa, C. kefyr, Rhodotorula mucilaginosa, Geotrichum candidum and G. silvicola. The protein profiles of the LAB isolated from motoho, analysed using SDS-PAGE, showed differences which could be attributed to the differing origins of the strains, namely the different sampling points of motoho production, or genomic heterogeneity of the strains. The motoho produced using the traditional method used a longer cooking time, and had the same nutritional profile as the motoho produced using the modified method. However, the sensory profile of the modified motoho was preferred by a sensory panel. Lactobacillus fermentum was the predominant microorganism during the production of motoho and could be selected as a potential starter culture for the large scale production of motoho. Also, changes made during the modified production of motoho could be implemented during upscaling as these changes were shown to yield a product with a preferred sensory profile.