Influence of thermal enzymatic hydrolysis of cereal starch on the physico-chemical quality of kunun-zaki (A fermented non-alcoholic cereal beverage).

ABSTRACT

Millet grains were steeped in 1% sodium metabisulphite (12w/v) for 5min and subsequently washed and wet milled; the cereal paste was gelatinized with boiling water (11w/v, 76±2oC) and immediately hydrolyzed separately either with α+β-amylases, α+amyloglucosidase or rice malt. The hydrolyzed cereal starch was inoculated with a 12h starter culture (2%v/w) of Lactobacillus plantarum, L. fermentum, and Lactococcus lactis and fermented for 6h. Chemical (pH, titratable acidity), physical (viscosity, S.G., total soluble solids) and sensory quality of the hydrolyzed cereal slurry and the fermented product were determined. The results obtained in this study show that the pH of the products decreased with concomitant increases in titratable acidity (% lactic acid) during production; however, the decrease in pH was more prominent in the ‘kunun-zaki’ produced from the cereal starch treated with α+β-amylases and this, differed from the other products (p<0.05). There was an increase in viscosity with a corresponding decrease in the total soluble solids (TSS) in all the samples throughout production; the decrease in TSS is an indication of an increase in the activity of the fermenting LABs. Furthermore, the sensory quality attributes of the three products were generally acceptable by the taste panelist in all the parameters evaluated (appearance, aroma, taste), however, the ‘kunun-zaki’ produced using the cereal starch treated with rice malt was preferred in taste and this was significantly different (p<0.05) from the other products. This study has shown that ‘kunun-zaki’ of acceptable quality could be produced within 7h, the marked reduction in the processing time of ‘kunun-zaki’ from 12-7h could encourage large-scale production of this popular drink.