Chapter 2: Literature Review - Perspectives in the Processing and Utilisation of Indigenous
2.2 The Marula fruit
2.2.6 Common processing methods for marula fruit and various indigenous fruits in South
In South Africa, the post-harvest processing of marula fruit involves two methods, i.e. the processing of the pulp into various products and the processing of the kernels into edible nuts and oils. Figure 2.3.1 below shows a brief summary in the processing of the pulp and figure 2.3.2 shows a brief summary of steps in the processing of oil.
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Figure 2.3.1: Steps in processing of marula pulp. Adapted from Bille et al. (2013)
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Figure 2.3.2: The processing of marula oil. Adapted from: Bille et al. (2013) 2.2.6.1 Marula Juice
According to Rampedi and Olivier (2013) methods applied during marula juice, jams, jellies (products shown in Figure 2.1.2) and traditional beer preparation are also applicable for other indigenous fruits processing, such as Kei Apple (Dovyalis caffra), Mobola Plum (Parinari curatellifolia), Wild Medlar (Vangueria infausta), Monkey Apple (Strychnos spinose), Sand apricot vine (Landophia kirkii), Sweet prickly pear (Opuntia ficus indica), sour plum (Ximenia caffra) etc. In the context of South Africa, S. birrea lays a base example representing other indigenous fruits since it has thrived its way to the international markets.
As described by Rampedi and Olivier (2013), refreshing marula juice is prepared from fully ripe fresh marula pulp. Where after the removal of fruits’ skin, the fruits pulp are collected into clean containers and water is added to dilute them in a ratio of approximately one part per ten
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parts. The mixture is allowed to soak overnight. The next day the fruits pulp mixture is squeezed by hand in order to extract the juice, seeds removed. Figure 2.3.3 below also illustrates flow steps involved in the making of marula juice.
Figure 2.3.3: Flow diagram for the preparation of marula juice. Adapted from: Rampedi and Olivier (2013).
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The processing method for traditional marula beer slightly differs from making juice and Figure 2.3.4 below summarises steps involved. The first step in the processing of marula beer is the separation of the skin from the flesh with either a fork or knife. The pulp is then squeezed and the resulting juice is collected into containers. The nuts with the remaining fruits flesh are mixed with water to release any remaining juice and pulp (Shackleton, 2004). Making marula beer requires the fruits pulp mixture to be concentrated in traditional clay pot. In so doing, ambient temperatures of approximately 25 °C must be maintained (Shackleton, 2004, Rampedi and Olivier, 2013).
The pulp mixture is left and allowed to ferment spontaneously for a period of two to four days (Shackleton, 2004, Rampedi and Olivier, 2013). After this period, the pulp mixture will resemble semi-solid masses of slurry suspended on top, having bubbles, signalling that the breakdown of fermentable sugars into alcohol has occurred (Rampedi and Olivier, 2013).
During the fermentation process, the slurry formed on top of the liquid is removed once or twice daily (Shackleton, 2004), within the 2-4 days period mentioned. After this stage the mixture is carefully filtered, and the beer is ready for drinking. The shelf-life of the beer is however limited, that is, it last for about 2-4 days, depending on the ambient temperatures (Shackleton, 2004). In a study by Shackleton (2004), the author mentions that other producers could make the beer last longer if they topped it with fresh marula juice on a daily basis, and this added 2-3 days in its’ shelf-life or they stored it into fridges. Unlike any traditional beer, marula beer preparation requires no additional supplementary ingredients like brown sugar, maize, yeast, sorghum (Rampedi and Olivier, 2013). For instance, traditional beer derived from bitter fruits of sour plum (Ximenia caffra) will require some sugar addition to improve it sensory taste, (Rampedi and Olivier, 2013).
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Figure 2.3.4: The marula beer process. Source: Nwonwu (2006) 2.2.6.3 The processing of Marula Liqueur (Amarula Cream)
Gathered by the rural populace, approximately 2435 tonnes per year of marula fruits are bought by Mirma (company involved in the production and processing of Amarula Cream). Ripe marula fruits are pulped or crushed, the kernels are removed in a destoner and the flesh is crushed from the skin. The marula pulp is then fermented under conditions similar to those of making grape wine. However, after fermentation, the marula wine undergoes a double process of distillation making use of copper pot-stills. The juvenile and immature liqueur will then be matured into small casks of oak for a period of about 2 years.
During this period, the liqueur will be enriched with pure marula extracts obtained from a special process that captures the unique flavour of the marula in a concentrated form. Following this is the creaming process; the obtained spirit will be blended with fresh cream until a smooth consistency is reached. The creaming process results into a rich and soft stable product, the
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Amarula Cream liqueur, with an alcohol content of 17% by volume (Amarula website, http://www.superbrands.com/za/pdfs/pdf2010/amarula.pdf, Accessed 07 August, 2016).
2.2.6.4 Other marula derived products
The nuts found inside the marula kernels are also utilized to supplement the diet of rural households. They are either consumed roasted or ground into powder and used a flavourant during meat and vegetable cooking, or used as a mix during cake and biscuit making. The residues from oil extraction can be used to produce marula seed meal, a protein rich by-product which can be used as a dietary feed for livestock (MlamboV et al., 2011).