Sorghum fermentation followed by spectroscopic techniques

The effect of lactic bacteria fermentation on sorghum was followed by spectroscopic techniques (H-1 NMR and FT-IR) and chemical analysis. Wet-cooked sorghum flour was inoculated with lactic bacteria (Lactobacillus fermentum, Lactobacillus bulgaricus, Lactobacillus lactis, Pediococcus pentosaceus and Pediococcus cerevisiae) and a mixture of Lactobacillus bulgaricus and Streptococcus thermophilus from a commercial natural yogurt. Only L. fermentum and the commercial yogurt inoculum were able to grow in sorghum. The induced lactic bacteria fermentations were compared with a spontaneous traditional fermentation carried out with flour used for fermentation purposes. In all fermentations, a decrease in pH was noticed and consequently an increase in titratable acidity was detected. Also observed were an increase in free amino acids and total protein content. Reducing sugars, soluble protein and starch decreased during the fermentation processes. These chemical results were confirmed by H-1 NMR and FT-IR. This study showed that spectroscopic methods are suitable and less time-consuming than chemical methods for following fermentation processes, giving the same relevant information and allowing large screening experiments. (C) 2004 Elsevier Ltd. All rights reserved.