1.1 Background of Study
Fruits and vegetables are important for good health and certainly good for all age categories because the class of foods forms an important portion of a healthy diet (Zhang et al., 2010). Fruits are highly perishable, non-staple foods which make up about 39% of the food intake (fresh state or processed form) of people living in developing countries of Africa (Bates et al., 2001). Based on fruits antioxidant capacities, they are used as indicators for healthy nourishment as well as protection factors of the human body against oxidative destruction (Costescu et al., 2006). Fruits have been shown to contain high amount of minerals, moisture, low ash and crude fibre (Wall, 2006) and are sources of sugar, vitamin A, C and B groups, low protein and lipid (Ogbonna et al., 2013).
Cashew (Anacardium occidentale L.) is a very popular and widely propagated tree in Nigeria. It is often propagated for the economic importance of the nut it produces as well as the “cashew apple” or pseudo-fruit which is actually a swollen stalk leading to the nut. Cashew trees are enjoyed for their fruit during its fruiting season and as a sun shed at off season. Its fruit consists of a nut and an apple which is attached to the stalk of its tree. Common uses include: analgesic (Pawar and Pal, 2002), diuretic (Yusuf et al., 2009), antiseptic for oral hygiene (Pell, 2004), asthenia treatment, respiratory problems, genital infections, and skin diseases (Florêncio et al., 2006). Literature reports evidences of its successful uses as a hyperglycemic (Sokeng et al., 2007), an antimicrobial (Akinpelu, 2009; Gonçalves and Gobbo, 2012), antioxidant (Melo et al., 2003; Trevisan et al., 2006), anti-inflammatory (Olajide et al., 2004; Vanderlinde et al.,, 2009) anti-ulcerogenic (Konan et al., 2007), and antiophidic (Ushanandini et al., 2000).
Cashew is rich in vitamins and minerals. According to Augustin (2001), the moisture content of cashew apple ranges from 85 to 89%, while its protein content was put at 0.2 and 0.1% for fat content, 11.6% carbohydrates and 0.9% crude fiber. Its mineral content was found to be 261 mg /100 g while vitamins such as thiamin - 0.02 mg/100 g, riboflavin- 0.5 mg/100 g, nicotinic acid - 0.4 mg/100 g and vitamin A - 39 IV were also found to be present in cashew apple. Cashew apple, a potentially useful nutritional source, is almost entirely wasted during current standard processing methods (Abdul and Peter, 2010).
Drying is one of the processing techniques used to preserve the fruit. Dehydrated products present high stability and are easy to transport and store. Drying is one of the most efficient ways to preserve foods. It reduces product’s water activity, which inhibits microbial growth and decreases degradative reactions, resulting in higher stability. Besides, drying results in substantial volume reduction, this facilitates transport and storage (Marques et al., 2009; Maskan, 2001). It is a commercial process widely used to preserve the quality of agricultural products with the objective of promoting long storage periods without significant losses during the process (Martinazzo et al., 2010). The seasonal nature of the production of the perishable cashew apple, the poor storeability and the lack of information on an appropriate processing technology are the reasons hindering the full utilisation of the fruit (Bidaisee and Badrie, 2001).
- Problem Statement
Fruit and vegetable are mostly are seasonal so that they cannot be available throughout the year and due to high moisture content, fruit and vegetable always have low shelf life. Dehydration is the best option to preserve the fruit during abundant production and it process concentrates the nutrients. Dehydrated fruits are rich in protein, total phenolics compounds, natural antioxidants, vitamins, minerals and fiber so it can be used in different products for enrichment.. Meanwhile, only the nut of cashew is being processed by roasting and removing the edible portion for direct consumption, grinding into powdery for different uses thereby neglecting and wasting the fruit. Therefore, drying of the fruit too should be put into practice to eradicate its negligence making it to be more useful and preventing its wastage.
1.3 Aim and Objectives
The aim of this study is to study the drying kinetics of cashew fruits.
The objectives of the study are to:
- To determine the drying characteristics of cashew using oven dryer at 60, 70, 80 ºC.
- To select the model that best describes the drying processes of cashew fruit.
Consumers, in a bid to have healthier and more natural foodstuffs, have been encouraged to increase their daily intake of fruits and vegetables because their nutritional values as suppliers of vitamins, minerals, fiber, and low fat are well recognized. However, the water content of most fruits and vegetables is higher than 80%, which limits their shelf-life and makes them more susceptible to storage and transport problems. Vegetables and fruits can be made more acceptable to consumers by drying. In addition, there is market for dehydrated fruits and vegetables which increases the importance of drying for most of the countries worldwide. In sub-Saharan Africa, a lot of losses of fruit and vegetables are usually experienced during the peak seasons and only a few cold storage of fruits and vegetables is practiced. Although drying is an energy intensive operation, it is highly very indispensable. Drying is needed to extend the shelf-life of foods without the need for refrigerated storage; to reduce weight and bulk volumes, for saving in the cost of transportation and storage; to convert perishable products (surplus) to stable forms; to produce ingredients and additives for industrial transformation (so-called intermediate food products (IFPs), and to obtain particular convenience food, with rapid reconstitution characteristics and good sensorial qualities. Also, the loss of product moisture content during drying results in an increasing concentration of nutrients in the dried food than in the fresh.