Morula Tree: From Fruit to Wine through Spontaneous Fermentation and the Potential of Deriving Other Value-Added Products

Abstract

Sclerocarya birrea (Morula tree) is one of the indigenous trees bearing wild fruits with various applications in the African communities. Wine is a globally known beverage usually made from grapes; however, recently, other fruits, including wild fruits with a considerable amount of sugars, can be used for making wines. The marula fruit wine is also important in many communities for cultural activities and can be enjoyed by people of varying age groups depending on the age of the product. In recent years, there has been growing interest in shifting from traditional marula winemaking to developing technologies for the marula winemaking process and commercialisation. The process of marula winemaking is similar to the production of grape wines, which entails collection, selection and washing of the fruits; extraction of the juice and mashing; formation and removal of the scum; and ultimately spontaneous fermentation of the resulting juice. The new process in marula winemaking would take into consideration the use of starter cultures as either monoculture or mixed cultures developed from the native marula fruit microbiota and the pasteurisation of the juice. The main challenge or difficulty with marula is the extraction of sugar and other soluble solids from the pulp more than it is for the grapes. The other challenge confronting the sustainability of marula wine is the seasonality of the fruit and poor juice yield. It is therefore imperative to develop strategies to increase the juice yield without affecting the quality, to preserve the marula fruits to ensure the year-round presence of marula fruit wine in the markets and, consequently, to improve the income generation capacity of the households dependent on the product. In addition to achieving a high juice yield, it is imperative to ensure consistent quality wine products. This review gives an overview of the S. birrea subsp. caffra and the biochemical components of the fruits or juice. It also highlights the use of marula fruits for wine production in African communities. The potential economic sustainability of the marula fruit wine is explored, particularly in southern Africa, where the marula tree (Morula) is abundant and the marula fruit wine is popularly produced. The review also examines the opportunities, challenges and future prospects of the marula fruit wine.