Growth potential of Salmonella infantis and Escherichia coli in fermenting tempeh made from horsebean,pea and chickpea and their inhibition by Lactobacillus plantarum

Salmonella infantis and Escherichia coli multiplied to varying degrees during the fermentation of unacidified horsebean, pea and chickpea tempeh. Active mycelial growth on the beans resulted in a sharp increase in pH. This was always accompanied by a sharp increase in the growth rate of the test organisms. Acidification of the beans during soaking decreased the growth rate of the test organisms only until active mycelial growth started. Inoculation of cooked beans with Lactobacillus plantarum resulted in a complete inhibition of E coli in unacidified and acidified chickpea tempeh and acidified pea tempeh. Marked inhibition of E coli was also noted in unacidified pea tempeh and acidified horsebean tempeh. S infantis was also completely inhibited by L plantarum in unacidified and acidified chickpea tempeh. In pea and horsebean tempeh, counts of S infantis were always lower in Lactobacillus-inoculated fermenting beans than in the control. Beside the pH, undissociated acids and other substances produced by L plantarum may be inhibitory to the test organisms. The use of L plantarum may be considered for the control of pathogens during commercial-scale tempeh production.