Characteristics of single and mixed culture fermentation of pito beer

Abstract

Abstract:The fermentation of Pito, a traditional alcoholic beverage, was done using selected yeast strains or a crude mixed yeast culture collected from traditional breweries and two types of sorghum malt. The fermentation characteristics and product quality of the pure and mixed fermentations were monitored and compared. Significant differences were observed between the mixed culture fermentation and the single culture fermentations. Acid production of the mixed culture fermentations was higher whereas ethanol production and sugar utilisation were lower than those of the pure strain fermentations. Sensory observations and analysis of volatile compounds also indicated differences in the fermentations. The use of pure cultures in fermentations proved to yield more ethanol. The sorghum variety was also observed to have an influence on the fermentation pattern. Utilisation of nutrients from the white sorghum malt extract was greater and faster than those from the red sorghum.

Determination of several flavours in beer with headspace sampling–gas chromatography

“…Changing trends of flavours was helpful to monitor the process of fermentation; in addition, of interest were their rapid variations during the whole fermentation process. It was known that beer flavours were produced by the metabolism of yeasts (Bvochora & Zvauya, 2001;De Stefano & Montanari, 1996;Demuyakor & Ohta, 1993;Vanderhaegen, Delvaux, Daenen, Verachtert, & Delvaux, 2007). The rapid increase of four flavour compounds at the beginning of fermentation demonstrated that metabolism of yeasts was robust and malt juice was immediately utilised (Guido et al, 2004;Petersen et al, 2004;Zaldivar, Martinez, & Ingram, 1999).…”

Parameters of processing and microbial changes during fermentation of borde, a traditional Ethiopian beverage

“…To avoid changes in product characteristics during scientific improvements of traditional food processes, it is important to understand the processes and formulation of the product (Demuyakor and Ohta, 1993). Some limited information is available on the fermentation (Bacha, 1997) and microbial load (Ashenafi and Mehari, 1995) of borde in central and southern Ethiopia respectively.…”

Sorghum

“…If allowed to ferment longer, the beer becomes progressively sourer in taste. The mieroorganisms responsible for souring have not been identified, but in view of the ambient fermentation temperature (27 -32°C) [76] and the aromatie character of the beer [79] theyare presumably heterofermentative lactic acid bacteria.…”

“…They are characterized by being filtered, but are somewhat doudy, sweetish and generally slightly sour tasting, of fruity aroma and contain 1-5 vol. % alcohol [69,77,79]. Brewing of these beers is a small-scale commercial enterprise [69,76].…”

“…The residue in the pot from previous brews provides the inoculum for the rapid (overnight) fermentation. Candida species and Saccharomyces cerevisiae appear to be the most important yeasts responsible for the fermentation [78,79]. The beers are consumed in an active state of fermentation within 24 h [69,77].…”