Vitamin C and mineral contents, acceptability and shelf life of juice prepared from four indigenous fruits of the Miombo woodlands of Tanzania

Author: Bernadette K. Ndabikunze ^1*, Bonaventure N. Masambu ² and Bendantunguka M. Tiisekwa ¹

Received 19 September 2009, accepted 11 April 2010.

Abstract

Indigenous fruits from Miombo woodlands play a vital role in the livelihoods of many rural areas of Tanzania. Chemical analysis of Vitex mombassae (smelly-berry), Adansonia digitata (baobab), Uapaca kirkiana (wild loquat) and Sclerocarya birrea (marula plum) indigenous fruits from various Miombo woodlands of Tanzania were carried out to determine their potential for juice processing. Fruit pulp yields were determined and analyzed for total soluble solids, acidity, minerals, and vitamin C and β-carotene. Juices were prepared based on single fruit formulation and preserved using sodium metabisuilphite and sodium benzoate (175 ppm each). The juices were stored at room temperature (25-32°C) and monitored for storage stability over a period of 90 days. Sensory evaluation was carried out to assess consumer’s acceptability using a 7-point hedonic scale for fresh and stored juices. Results show that, U. kirkiana had significantly higher (P > 0.05) pulp yield and total soluble solids (283.4 and 169 g kg^-1 respectively) compared to the other fruits. Acidity was highest in A. digitata (22.7 g kg^-1) and lowest in U. kirkiana (0.5g kg^-1) (P > 0.05). Potassium ranged from 1038.3 in A. digitata to 1758.0 g kg^-1 in V. mombassae. Iron content was higher in S. birrea (3.51 g kg^-1) and lowest in U. kirkiana (2.14g kg^-1). Vitamin C content in the fruit pulps ranged from 201.19 to 404.55 g kg^-1 in S. birrea and V. mombassae respectively. The β-carotene ranged from 0.00 in A. digitata to 9.48 g kg^-1 in U. kirkiana. Pasteurization and storage of the fruit juices did not significantly (P > 0.05) affect total soluble solid and acidity. Vitamin C was reduced by 41%, 55%, 45% and 56% in V. mombassae, U. kirkiana, S. birreaa and A. digitata respectively. These results show that despite the long storage time the fruit juices still contained sufficient vitamin C even to meet the daily-recommended allowance. Sensory evaluation results show that juice prepared from A. digitata was more accepted in all sensory attributes for both fresh and stored juices. V. mombassae was the least liked juice. The combination of pasteurization and chemical preservation increased shelf life of the juices to 90 days. Based on the quality of the fruits juices and stability exhibited, there is great potential for indigenous fruits for juice making.

Key words: Indigenous fruits, juices, Miombo, acidity, minerals, vitamin C, acceptability, shelf life.