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

University dissertation from Food Technology, Engineering and Nutrition, Lund University

Abstract: Popular Abstract in English In Mozambique, many wild fruit species occur naturally in forest environments. Most of the wild fruits are consumed fresh because of their short shelf-life when ripe. Forests play an important role in rural communities as a source of food and medicinal and social/cultural services and also provide a source of income when fruits are sold at local markets. Some parts of Mozambique are still poor with food insecurity, and wild fruits can provide a mean of relieving malnutrition. Vangueria infausta (African medlar) is common in forests, especially in southern and central Mozambique. The fruit is a source of vitamins, minerals, protein and carbohydrates. The fruit also contains sugars, dietary fibre and organic acids, which are very important for human nutrition. People in Mozambique traditionally eat fruits between meals while herding cattle or working in the fields. The V. infausta tree grows to a height of 3 to 7 m, with an average annual yield of 35 kg fruit per tree. The fruit has 3 to 5 seeds, which must be removed before processing. Due the problem of rapid deterioration after harvest, drying is one way of prolonging the shelf life of V. infausta fruit. The objective of this project was to investigate how V. infausta fruit can be dried and used as a consumer product. The fruit studied in this project was collected in the Paquete district of Maputo, Mozambique, vacuum packed, frozen and transported to Sweden. All experiments and analysis were performed in Sweden using V. infausta pulp. The first challenge in this study was the lack of literature on drying of this fruit. Therefore, different temperatures and air velocities were tested. Drying temperatures of 60 °C and 80 °C in combination with an air velocity of 3 m/s resulted in a reasonable drying time and safe water activity, but the product was extremely hard. Two additives, namely sucrose and maltodextrin, were investigated to soften the dried fruit pulp. V. infausta pulp with and without these additives was dried using convective drying and solar-assisted pervaporation (SAP). SAP is a new technique for concentrating liquid and pulp foods using breathable textiles. The water activity and water content were measured during drying. Mechanical properties such as the hardness and toughness were also evaluated. A predictive model was used in order to simulate the water activity and water content during drying. Commercial samples of dried figs, dried pineapple and dried cranberries were investigated for comparison with the dried V. infausta pulp. The water activity and water content were measured to ensure microbiological safety and hardness and toughness were measured to determine a suitable softness of dried fruits. To get guidelines of how to combine microbiological safety and hardness the commercial window was introduced. The loss of aroma during convective drying of V. infausta fruit pulp was also investigated. The findings showed that the samples of dried pulp without additives were too hard to be consumed. The convectively dried samples with added maltodextrin were close to the commercial window, but still too hard. However, the addition of sucrose softened the dried product sufficiently, and both the convectively dried and SAP-dried samples fell within the commercial window. This dried product is thus both microbiologically safe and accepted by consumers. The aroma components present in pure dried V. infausta pulp were retained for at least 240 min of drying. Samples dried for 300 min showed reduced amounts of volatile compounds, and at the end of drying 420 min no aroma components could be identified. The loss of aroma components is thought to be the consequence of the crystallization of sugars during the drying process. The results of this work thus demonstrate that dried Vangueria infausta fruit has the potential to be used as an ingredient in desserts and ice cream, or as a nutritious snack.