Cashew Processing and Quality Indices

Abstract

Cashew is made up of the nut attached to the apple (false fruit) both of which have nutritional significance and economic value. Evaluating the changes that occur during growth and maturation as well as processing will help to optimize quality. This is what the study involved. Compositional and physical changes were monitored in six cultivars of cashew (apple and nut). Local cashew trees were selected randomly after flowering. Collection of samples commenced after fruit set and at weekly intervals till 8 weeks (maturity). Physical analysis included weight (whole cashew, nut, apple, cashew nut, nut kernel and shell) and size (length of apple and nut, thickness and width of nut and top and bottom diameter of apple).All the physical indices of apples showed a single phase of continuous increase after fruit set reaching maximum values at 8 weeks. Weight and length of apples increased from 0.31 ± 0.01-68.56 ± 0.32g and 0.69 ± 0.03-5.82 ± 0 .12cm respectively. Unlike the apples, the growth pattern of nuts occurred in two stages. There was initial rapid increase with the attainment of maximum values at 4 and 5 weeks after which a decrease occurred. At 8 weeks the nuts attained a proportion o f their maximum values i.e. weight (4.89 ± 0.09-6.33 ± 0.15g) and length (2.41 ± 0.01- 2.90 ± 0.02cm). Growth time was more strongly correlated with the physical indices of apples.Similar trends of total sugar accumulation occurred in both the apples and cashew nut kernels. Increases were observed with maturation and optimal values of 10.01-10.85% for apple and 5.04-6.14% for the kernels was observed at 8 weeks. Increase in the ash (0.48-2.70g/l OOg), total solids (27.57-80.28%), fat (1.81-39.42g/100g) protein (0.95-20.93g/100g) and mineral (e.g K:20.81 -491.3 5mg/1 OOg) contents occurred in the kernel from fruit set to 8 weeks. These increases were rapid after 4 weeks of growth. The apples increased in moisture (69.42- 86.95%), vitamin C (72.51-225.9-49mg/100g) and titratable acidity during growth and maturation (Fruit set-8 weeks). All the above constituents in the cashew kernel and apple were at maximal values by the eighth week of growth. The nut kernel generally decreased in moisture (73.46-19.46%) with growth. pH (4.11-3.65) of apples generally decreased whilst total solids (30.58-13.05%)ash(0.84-0.45g/100g)andmineral(e.g.P:243.04-128.21mg/100g)contents decreased continuously from fruit set to 8 weeks. Pectin and tannin contents of the apples increased to maximum values generally between 3-5 weeks, after which depletion occurred. At 8 weeks, minimum values of pectin (0.59-0.76%) and tannin (0.19-0.40 g/1 OOg) was attained. Changes in chlorophyll (total chlorophyll, chlorophyll a & b) and absorption spectra of two apple cultivars were monitored during growth. Chlorophyll contents of the apples (e.g. total chlorophyll: 15.05-1,04mg/l OOg) decreased with maturation (fruit set to 8 weeks). The same occurred for the number of peaks (5-1) in the absorption spectra. Processing methods, peeling, steaming and peeling before steaming were applied to the apples. Quality indices o f the resultant juice was analyzed by objective and sensory methods and during one week of storage. pH, acidity, vitamin C and tannin contents of apples were significantly affected by the methods of processing (P < 0.05). Peeling before steaming was most effective in reducing tannin contents. Apart from tannin, vitamin C (266.42- 155.42mg/100g) and pH (4.41-4.08) decreased whilst titratable acidity increased during storage. Sensory analysis included sweetness, colour, flavour, astringency intensities, and overall acceptability. Panelists generally preferred and most accepted the quality indices of juices obtained from steamed (SAJ and PSAJ) apples as compared to unsteamed ones (WAJ and PAJ).