Fermentative Microbes of Khadi, a Traditional Alcoholic Beverage of Botswana

Abstract

Khadi is a popular traditional alcoholic beverage in rural households in Botswana. The product is produced by fermentation of ripened sun-dried Grewia flava (Malvaceae) fruits supplemented with brown table sugar. Despite its popularity, its growing consumer acceptance, its potential nutritional value, and its contribution to the socio-economic lifestyle of Botswana, the production process remains non-standardized. Non-standardized production processes lead to discrepancies in product quality and safety as well as varying shelf life. Identification of unknown fermentative microorganisms of khadi is an important step towards standardization of its brewing process for entrance into commercial markets. The aim of this study was to isolate and identify bacteria and yeasts responsible for fermentation of khadi. Yeasts and bacteria harbored in 18 khadi samples from 18 brewers in central and northern Botswana were investigated using classic culture-dependent techniques and DNA sequencing methods. Additionally, we used the same techniques to investigate the presence of bacteria and yeasts on six batches of ripened-dried G. flava fruits used for production of the sampled brews. Our results revealed that Saccharomyces cerevisiae closely related to a commercial baker’s yeast strain sold locally was the most predominant yeast species in khadi suggesting a possible non-spontaneous brewing process. However, we also detected diverse non-Saccharomyces yeasts, which are not available commercially in retail shops in Botswana. This suggests that spontaneous fermentation is partially responsible for fermentation of khadi. This study, presenting the first microbiological characterization of a prominent traditional alcoholic beverage in Botswana, is vital for development of starter cultures for the production of a consistent product towards the commercialization of khadi.

Functional Characterization of khadi Yeasts Isolates for Selection of Starter Cultures

“…5). In our previous work, we recorded an average of pH of 3.1 ± 0.31 [6] in agreement to a range from 2.87 to 3.16 reported by Mapitse et al (2014). Our current results suggest that all the strains tolerated a pH of 3 except T1 (Z. bailii), and Z1 (R. nothofagi).…”

“…Uncontrolled spontaneous fermentation, unstandardized brewing processes, unsafe practices such as the use of marijuana, car battery acid, tobacco, and even dagga are documented as responsible for product inconsistencies and food poisoning [2,3]. A subsequent study by Motlhanka et al (2020) documented the dominance of both Saccharomyces and non-Saccharomyces yeasts in khadi, suggesting their important role in the production of this beverage. Functional characterization of khadi yeast isolates is one of the crucial lead steps towards the development of starter cultures.…”

Production and Comparative Assessment of Alcoholic Drinks Produced From Cassava, Maize and Plantain Flour Using Locally Produced and Imported Enzymes

“…Similar practical example was established in indigenous distilled liquor (Areki), where the observed least total dissolved solids liquor was proportional to higher alcohol content [23]. Nonetheless, the light alcohol contents (3.28-5.03%) observed for the drinks produced was in conformity with other local alcoholic beverages reported by several authors; tella: 2-6% [28], maize and banana extract: 3.32-4.63% [17], banana alcohol: < 8% v/v [29], cassava spirits: 7.8-26.3% [6] and Kachasu from maize meal: 9-41% v/v [30]. The density of a liquid sample is defined as mass of the liquid per volume [31].…”

Metabolomics of Non-Saccharomyces Yeasts in Fermented Beverages

“…khadi [85], and chicha [86], to name just a few. These traditional fermented beverages are likely an excellent source of yeast with diverse impacts on sensorial properties as they represent a diverse range of flavour and aroma characteristics and are also likely to contain yeasts well suited to industrial fermentative environments.…”