Olatidoye OP*, Awonorin SO, Shittu TA, Ajisegiri ESA, Sobowale SS and Adebo OA
The use of inappropriate temperature-time combinations during roasting of nuts could lead to quality defects, such as burnt taste, dark colour, short shelf-life, rancidity, and poor flavour. The objective of this study was to determine the effect roasting temperature (100-160°C) and time (20-60 min) on colour parameters (L*, a*, and b*- values), Browning Index (BI), Hardness, consumer acceptability and moisture content of both whole cashew-kernel and cashew nut paste using Response Surface Methodology. The experimental runs were established using central composite rotatable design. Second-order polynomial models were developed for predicting the determined product properties. The results showed that CIELAB L*-value of the colour decreased from 54.41 to 41.23 while a*- and b*- values increased from 6.08 to 15.84 and 13.77 to 25.92, respectively, p<0.05 as the temperature and time increased. The moisture content and hardness decreased from 6.35 to 1.02% and 34.24 to 19.94 N, respectively, while BI increased from 47.47 to 97.94 as the temperature and time increased. The results showed that colour parameters (L*, a*, b*-values, BI) of whole cashew-kernel and a*-values of cashew nut paste could be used to monitor the roasting quality of cashew nut. The regression models significantly described the changes in moisture, hardness and colour parameters at p<0.05 (R2=0.96). The recommended range of roasting temperature and time of wholekernel for cashew paste was 145°C and 40 min with desirability of 0.85 which is measure of goodness of fit of RSM model. The study showed that the optimized processing conditions produced acceptable cashew kernel and paste of desirable colour and superior flavour quality with short processing time that will enhance direct and commercial utilization.
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