Utilization of Wild Fruit in Mozambique – Drying of Vangueria infausta (African medlar)

Detta är en avhandling från Food Technology, Engineering and Nutrition

Sammanfattning: Vangueria infausta (African medlar) is a wild fruit found in southern and central Mozambique. The ripe fruit has a leathery skin enclosing three to five seeds embedded in a soft pulp that tastes like apple. It plays an important role in the diet of the rural population and has the potential for commercial use. The fruit is mostly eaten fresh, and sometimes mixed with porridges, but in some parts of the country it is stored dried for use in times of food scarcity. The V. infausta plant has been used to make herbal remedies to treat malaria, chest ailments such as pneumonia, as a purgative, to treat ringworm, and also for the relief of toothache. The V. infausta fruit has a short shelf life after ripening. The ripe fruit can be dried as whole fruits or pulped and dried in thin layers. The long term objective of this work was to investigate how V. infausta could be preserved by drying. More specifically, the aims were to determine and optimize the drying characteristics of V. infausta by convective drying with and without additives (saccharides), and also to try to implement this drying technique in an area where the fruit grows. The effect of temperature during drying (from 40 to 100 °C) was investigated by studying the moisture content, water activity, and the mechanical parameters, hardness and toughness, of the dried fruit. Solar-assisted pervaporation (SAP), involving a novel technique for concentrating liquid and pulp foods using breathable textiles, was investigated as an alternative to convective drying of V. infausta fruit. Finally, loss of aroma compounds from the pulp during drying was also investigated using gas chromatography. The addition of sucrose at different levels proved to be useful to soften the product so that it was acceptable for consumption regarding softness of the product and microbiologically safety. Convective drying and SAP resulted in dried products with similar characteristics regarding shelf life and softness. These results show that SAP could be an alternative method of preserving V. infausta in areas with little or no infrastructure. The main aroma components present in V. infausta pulp were identified and it was found that they were retained for at least 240 min of drying, after which they decreased with drying time. Potential applications for dried V. infausta are in desserts and as nutritious snacks.

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