Abstract
The potential for lactic acid fermentation to improve the safety of infant weaning foods has been investigated using a model rice based food. The growth and survival of diarrhoeal-causing pathogens (E. coli, Salmonella typhimurium, Shigella sonnei and Staphylococcus aureus) in unfermented, fermenting and prefermented porridge were studied. Saccharification of rice porridge with diastatic malt extract and ragi was found to be essential to ensure a good lactic fermentation. Results indicated that the pathogens grew well in unfermented porridge. Cofermentation of pathogen with lactic acid bacteria adversely affected growth of the pathogen but this was marked only when the lactic acid bacteria was numerically dominant. Prefermentation produced a lethal effect on the pathogen and showed greatest promise as a technique to improve safety. The inhibition of the pathogens was found to be solely due to the acid production during fermentation. The most effective starter organisms were the Lb. plantarum followed by Lb. bavaricus as compared with Lc. lactis. However, Lb. plantarum produced large amounts of the D(-) isomer of lactic acid which is less well metabolised in humans and if used for infant feeding, might lead to acidosis. Even though Lc. lactis produced bacteriocin-nisin during fermentation, it did not contribute appreciably to inhibition of the tested pathogens. Recycling the fermented porridge was found to be the successful way of applying the fermentation technique in developing countries.