Abstract
Aim: This study aims to evaluate the effect of lactic acid bacteria (LAB) fermentation on the nutritional and mineral composition of millet flour.
Methods: Millet was processed into flour, then fermented spontaneously and with Aerococcus viridans 4448 and Limosilactobacillus fermentum SCB0035 combined in a co-culture for 72 h. 250g of the flour was mixed with sterile distilled water in a ratio of 1:2w/v. Exactly 0.02% of sodium metabisulphite was added to the mixture to suppress the growth of contaminating organisms before the addition of the starter culture. The setup for spontaneous fermentation did not include sodium metabisulphite and starter organisms. The fermentation products were analyzed for proximate and mineral contents using the association of official analytical chemistry (AOAC) and atomic absorbance spectroscopy (AAS) methods respectively.
Result: The result shows that the bacteria load increased within the first 48 h with a slight decrease after 72 h in both spontaneous and LAB fermented flours. There was a decrease in the pH of millet flour during fermentation which ranged from 5.00±0.00 to 4.75±0.00 (spontaneous fermentation) and from 4.92±0.00 to 3.96±0.00 (LAB fermentation). The result for the proximate composition of the fermented and unfermented millet flours showed a significant (P<0.05) increase in moisture, ash, and protein contents with a decrease in lipids, fiber, and carbohydrate contents when the raw flour was compared to the fermented flours. After fermentation, the macronutrient composition of the unfermented spontaneously fermented and LAB fermented millet flours showed a significant (p<0.05) increase in potassium, sodium, phosphorus, and calcium. Potassium increased from potassium from 2003±0.58mg/kg (raw sample) to 2301.33±1.53mg/kg (LAB fermentation). Sodium increased from 1211±1.73mg/kg (raw sample) to 1801.00±1.00mg/kg (LAB fermentation). Phosphorus increased from 727.27±.01mg/kg (raw sample) to 954.567±0.01mg/kg (LAB fermentation) while Calcium increased from 272.70±.0.10mg/kg (raw sample) to 533.10±0.10mg/kg (LAB fermentation). The increases were found more in the LAB fermented millet flour. The result of the micronutrients showed an increase in, iron, magnesium, and copper after fermentation except zinc.
Conclusion: The highest increase in the nutrient contents of the flour was found to be more in LAB fermentation which is an indication of the potential of lactic acid bacteria in enhancing the nutrient's bioavailability and can be employed in natural food fortification.