For thousands of years
For thousands of years, conventional fermentation processes relied on sharing of knowledge and methods of fermentation from generation to generation. Inoculation was done by method known as ‘back slopping’, in which a residue from a previous batch of suitable quality was added to a new batch (Holzapfel, 1997).
The industrial development of food production together with the prospering of microbiology in mid-1900s led to the optimization and upscaling of many food fermentation processes (Leroy & De Vuyst, 2004) and hence, advancement of starter cultures. A starter culture can be described as a preparation comprising large numbers of variable microorganisms, which can be added to speed-up a fermentation process (Holzapfel, 2002). There are three classifications of starter cultures which include single-strain cultures, multiple strain cultures and undefined mixed starter cultures which contain two or more strains. The direct introduction of selected starter cultures to raw materials has been a great revolution in the processing of fermented foods, resulting in a more precise control of fermentation process and stable product (Leroy & De Vuyst, 2004). Utilization of yeast as starter culture for wine fermentation and distillates has led to the production of beverages of more uniform quality with a commercial value (Fundura et al., 2002).
When seeking a yeast strain for industrial use, exact physiological properties and suitable growth conditions need to be established (Osho, 2005). The tolerance of yeast to its substrate, fermentation product and temperature has massive potential to be used in industrial scale fermentation. Therefore, the yeast should have temperature, osmotic pressure and ethanol tolerating capacities to perform efficiently in industrial scale (Balakumar & Arasaratnam, 2012). Therefore, the development of starter cultures has become a vital science with a driving force to search for microorganisms especially appropriate for food fermentations (Nyanga, 2012).
The optimisation and control of the processing of indigenous fruit products, has the potential of multiple benefits, including the improvement of the socio-economic status of rural communities through employment creation, providing a non-seasonal supply of safe and quality beverages, domestication of the fruit trees as well as retaining an important food source (Cavendish, 2000). There has been no attempt to produce alcoholic beverages from these two wild fruits. The long-term goal of this study is to promote and increase the utilisation and consumption of these two indigenous fruits through production of alcoholic drinks.
To scale up the production of the beverage, the development of starter cultures is pre-requisite. The use of appropriate starter cultures will reduce the fermentation time, and improve and stabilise the nutritional, sensory properties and quality of the product. Therefore, the development of starter cultures through characterisation of the yeast that will be used is pivotal to produce the novel beverage.