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IMPACT OF BLANCHING PRE-TREATMENT ON PHYSICOCHEMICAL PROPERTIES AND DRYING EFFICIENCY OF DATE FRUITS (PHOENIX DACTYLIFERA L.)

Abodunrin, D.O. & Atteh, A.P.

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Abstract

The paper evaluated the efficacy of pre-treatment blanching conditions (50 C; 2, 5 and 10 min) on physicochemical characteristics and drying efficiency of Nigerian Khanazi variety of dates (red/yellow varieties). In the context of a large post-harvest losses of dates (21,000 tonnes per annum) and underutilization potential in Nigeria, our focus on critical gaps in local varieties optimization of blanching represents an important step in value addition to the Nigerian date industry. Findings validate that the effect of the combination of blanching and temperature can provide a strong improvement in the drying kinetics: 10-min of blanching at 70 o C yielded 3 times faster drying time (32 h vs. 46 h control) and 37 percent faster peak drying rates (1.82 vs. 1.33 g/h) of oven-dried red dates. Nevertheless, high levels of blanching (5 min and beyond) softened the texture and led to non-enzymatic browning at 60 and above. Blanching of 2 minutes maximised the preservation of quality maintaining enhancement of efficiency (8 to 12 per cent time savings), whereas the cabinet drying performed better than the oven drying in the blanched yellow dates by 20 percent. The trends in moisture diffusivity (D eff) demonstrated the case hardening and the microstructural changes that enhanced it at high temperatures in oven-dried red dates but decreased it with temperature in cabinet-dried yellow dates. The Modified Henderson-Pabis was able to predict behavior of drying reliably (R 2 > 0.98). To Nigerian processors, it is therefore suggested that the use of 2-min blanching at 50 o C to achieve a trade-off between efficiency and nutrient/color yield, minimising post-harvest losses without compromising marketable quality.