The selection of lactic acid bacteria to be used as starter cultures for Ting production

Abstract

Most of the traditional foods in Africa are fermented before consumption. Fermentation is an old technology; however, during this process, especially in traditional fermented cereal based products with special emphasis on Ting, there is very little control involved during the processes. Fermentation is thus left to chance inoculation from the environment. Ting is a sorghum based product that is a result of LAB fermentation and has 0.6-0.7% lactic acid with a final pH of 3.5-4.0. However, there is presently no adequate information on the employment of starter cultures for most South African traditional fermented foods. The aims of this research were therefore to evaluate the use of different isolates of LAB that had been previously isolated from Ting as potential starter cultures for Ting production, to evaluate whether these would result in a product with sensory characteristics similar to those of the naturally fermented Ting and also to determine the nutritional composition of Ting. Six isolates LAB isolates (Lactobacillus collinoides 1.42, Lactobacillus cellobiosus 3.42, Leuconostoc mesenteroides 2.35, Lactobacillus cellobiosus 4.35, Lactobacillus cellobiosus 3.30 and Lactobacillus curvatus 5.30) previously isolated from Ting were used in this study. When inoculated into sorghum mash to initiate Ting fermentation, the LAB starter cultures reduced the pH from 6.5-6.8 to levels below 4.5 within a reduced fermentation time of 12 h instead of 48-72 h as is the case with the naturally fermented Ting. The same starters increased the amount of lactic acid present in the samples from 0.02 to 0.3% within 12 h, reaching up to 0.5% after 72 h of fermentation. The nutritional composition of all the products was similar. The minerals calcium, phosphorous, magnesium and iron were analysed and phosphorous was the highest followed by magnesium; with calcium and iron being the lowest. Among all the amino acids analysed, glutamic acid was the highest in all the samples, followed by proline and leucine with cystine and lysine being the least. Generally, Ting was found to be high in protein and energy although with a low fat content. Based on the results of the consumer acceptability study, of all of the six LAB isolates; the LAB isolate L. cellobiosus 4.35 could be the best option when considering a starter culture for Ting production since the sample had the highest consumer acceptability results similar to the naturally fermented Ting sample.