The African continent has a variety of indigenous fruit, and many are not processed and this study will try to mitigate the fact that little research is done on the processing of many of this indigenous fruits, the focus is on Strychnos cocculoides commonly known as monkey orange. The monkey orange tree is a compact tree 2-8 m tall (occasionally reaching 10m) found in the Kalahari and its surrounding savannas and dry woodlands. It is found on sandy soils and rocky slopes in Botswana, northern Namibia and parts of Zimbabwe and South Africa.
Strychnos cocculoides is a tree indigenous to the tropical and subtropical Africa. (Bille, P. G. 2013)
In Namibia it is commonly found within the dry woodland of the North Eastern part of the country such as. Strychnos cocculoides is one of three Strychnos species that stand out including S. spinosa and S. pungens. These species of monkey orange fruits produce large, pleasantly flavoured that are easy to handle and often in short supply.
In general S. cocculoides adapt to a harsh environment and can survive severe drought the thick bark makes it possible to survive wild fire and be able to coppice afterwards.
It produces, sweat-sour, yellow fruits containing numerous hard brown seeds, it bears round fruits 6-10 cm in diameter, with hard, woody, brittle shells. When immature they look like avocados. They fall from the tree before they ripen. As they mature the thick shell turns orange, at which point it can be broken open and the yellow or brownish pulp scooped out.
The pulp is known to be very refreshing, and its taste has been variously described as a combination of citrus and pineapple or a mixture of citrus and banana. (Bille, P. G. 2013)
The Monkey orange pulp is a good source of Vitamin C, zinc and iron. It has potential to improve the nutritional status of rural populations, mostly pregnant women and young children. A deficiency of vitamin C weakens the immune system and promotes the vulnerability to diseases and results into scurvy. This research aims to study the best time- temperature heat treatment combinations on the juice to lengthen its shelf life and preserve maximum nutritional quality. The acquired knowledge can be used to pave way for small scale production and develop a new stable product that will ensure food security in Namibia. Since it is not commercialized in Namibia, this study targets to encourage future commercialization of Monkey orange product.
The research might be more effective if the researcher had more time to conduct an in-depth investigation. Thus time will be one of the limiting factors, however time management will be practiced so as to fulfil the objectives of the study.
Corky monkey-orange (Strychnos cocculoiddes) commonly known as monkey orange tree is an evergreen to semi-deciduous tree grows up to 2-8 m tall (occasionally reaching 10m) on Kalahari sands in dry woodland. The corky bark is pale grey to grey-brown and the under bark is a pale brown colour. The leaves are bright green above and a paler green below. Small, green-white flowers display from October to December. A round berry is dark-green with white to pale green specks and turns yellow when mature in a hard, woody shell. The fruit is edible and the fermenting fruit can be made into an alcoholic drink. The seeds are toxic and the bark contains strychnine. (Ngadze, R. T., et al. 2017)
In Namibia it is distributed within the dry woodlands, commonly found in the northern and north eastern Namibian region such as along the Kavango River, Zambezi Region (or the Caprivi Strip) and also around Rundu. The strong wood is used for tool handles. In general S. cocculoides adapt to a harsh environment and can survive severe drought the thick bark makes it possible to survive wild fire and be able to coppice afterwards. (Ngadze, R. T., et al. 2017)
Ngadze et al. reported that the fruit of S. cocculoides is used for medicinal purposes. Immature fruit can be crushed and mixed with water to treat snakebites, ear pain, and swellings. The pulp of mature fruit mixed with table sugar is used to treat coughing. Immature (green) fruit are used to induce vomiting. (Ngadze, R. T., et al. 2017)
It has great potential to improve the nutritional status of rural populations, it being a food source in places with constant shortages, since it is rich in vitamin C, zinc, and iron. Monkey oranges are widely consumed by rural communities, particularly women and children in Southern Africa. (Ngadze, R. T., et al. 2017)
Nutritionally, the fruits has health benefits known for high energy, fiber, minerals (iron and zinc) and vitamin C. Strychnos spp. depending with species have an iron content up to 140 mg/100 g, giving potential to deliver iron when used as a food source by pregnant or lactating women and children. Fruit sweetness depends highly on sugar composition. Sitrit et al. report accumulation of sugars and organic acids during ripening and sucrose conversion to glucose and fructose at the onset of ripening for S. spinosa. Total sugars were 28.2 g/100 g and the most abundant sugar was sucrose (12.9 g/100 g), a disaccharide, followed by the monosaccharides glucose (4.6 g/ 100 g) and fructose (1.9 g/100 g). Organic acids in fruits originate from biochemical processes or from the activity of some microorganisms such as yeasts and bacteria. The presence of organic acids (citric, malic and succinic acids) explains the acidic component that blends with sugars and results in the species characteristic blended acid-sweet taste. (Ngadze, R. T., et al. 2017).
Saka et al further reported a mean acidity of 1.13% for S. cocculoides processed juice. The pH of S. spinosa was 3.2 and 2.8, while that of processed S. cocculoides juice was 3.5.
Food high in fiber are known to be richer in micronutrients, this might explain the high micronutrient content of S. innocua and S. spinosa. The ash content of the four monkey orange species was between 0.5 g/100 g to 4.7 g/100 g for S. innocua and S. cocculoides.
The reported mean mineral contents of S. cocculoides had highest mean content of Fe (70.5 mg/100 g) of the four monkey orange species. The vitamin C content of monkey orange fruits ranged from 34.2 mg/100 g to 88 mg/100 g. The moisture content of monkey orange ranges from 60% to 91%. (Ngadze, R. T., et al. 2017).
When picked, ripe monkey orange can be stored for up to two weeks under ambient conditions -mainly in shade-before they spoil. Slow spoilage can be accredited to the hard shell of the fruit, which also resists fungi and fruit flies. However, fresh fruits with a high moisture content like monkey orange undergo direct or indirect nutrient and quality losses during storage. (Ngadze, R. T., et al. 2017).
Pulp is sieved or strained with a mesh sieve substituted traditionally with a woven high-density polyethylene (HDPE) fruit sack. Water is added in a 1:1 ratio and lemon fruit juice or citric acid (depending on availability) is added as a preservative for the juice. The juice is boiled and crystalline sugar added, again depending on consumer preference and intended storage time. (Ngadze, R. T., et al. 2017).
Heat treatment or pasteurization of juice has a great effect on pathogens and several spoilage microorganisms, however this does not prevent the effects it has on sensory and nutritional quality (Aneja.et al, 2014). The shelf-life stability of fruit juices has been achieved by thermal processing. Low temperature long time and high temperature short time are the most commonly used heat treatments for juice. Traditionally juice is pasteurized by batch heating technique at 63-65 degree Celsius for a longer time. (D’Amico et al. 2006). Antioxidant activities of the juice is highly affected by uncontrolled heating and storage temperature with a reduction in vitamin C content. 72 degree Celsius for 15 seconds is the recommended to retain bioactive compounds with refrigeration of about 6 degree Celsius to preserve this compound over 60 days.
The Monkey orange fruit was provided by the University of Namibia for a Small Scale Product Development project with the department of Food Science and Technology. The fruit with a hard shell, pulp and numerous seeds will be obtained with cracking the hard shell open with a hammer to obtain the pulp embedded with seeds. The pulp will be separated from the seeds using a finisher, which does this by means of a brush and rotating sieve that lets the pulp and seeds exit from different openings. The pulp will be diluted with distilled water and sugar might be added.
Monkey orange fruit Sugar ph meter Refractometer
0.1 M sodium hydroxide QuerceinPhenolphthalein indicator Sodium carbonate 20% DPPH Plate count agar Methanol Folin- Ciocaltue reagent
The Monkey orange fruit will be cracked open with a hammer, the pulp with seeds will be weight. The pulp will be separated from the seeds using a finishing machine, the pulp is then weight alone. A given amount of pulp will be mixed with an equal amount of water, this will be filtered and pasteurized at temperatures: 70, 85 and 95 degree Celsius for 2 minutes, 1 minute and 30 seconds respectively. This will be stored at temperatures 6 and -3 degree Celsius over a time of 21 days.
The moisture and total solids of Monkey orange juice will be determined with the method outlined by AOAC: 1995
Fruits, fruit juice, have an ash content about 0.2 – 0.6%. The total mineral content of the juice will be determines as ash content, which is the inorganic residue after organic matter is burned away.
A spectrophotometer will be used to read the sample of juice at a wavelength of 430nm.
A pH meter will be used to determine the hydrogen ion concentration of the juice using a100ml Erlenmeyer flask.
Total acidity will be determined by titration with 0.1M sodium hydroxide and 10 ml of Monkey orange juice using 0.3 ml of 0.1M phenolphthalein as an indicator to obtain the total acidity of the juice as a percentage of citric acid.
% Citric acid = T*192*103*1000 Brix
A Refractometer will used, where by a drop of juice will be placed on a Refractometer with a pipette to determine its brix.
Its determination will be done using the DPPH (2, 2-diphenyl-1-picrylhydrazyl) assay following McCune & Johns (2002).
The Folin- Ciocalteu for total phenolic content determination described by Singleton and Rossi (1965) and modified by Waterman & Mole (1994).
Total plate count will be carried out on the Monkey orange juice under all treatments to indicate the bacterial population of the sample. Tenfold serial dilutions of the juice will be prepared by pouring of plate count agar into serial petri dishes and incubated at 35 degree Celsius for 48 hours and 25 degree Celsius for 72 hours.
The mean will be obtained from Microsoft excel and SPSS will be used to analyse and compare variances at a significance level of 0.05.