Evaluating performance of the improved hybrid passive and active mode solar dryers for processing Mangoes and Pineapples

Farmers in East Africa have no access to modern processing technologies because they are costly and high-energy demanding to operate. As a result, they solely rely on the traditional open sun drying (OSD) method, which is ineffective and causes further loss of the produce. In response, a modified passive-mode hybrid solar dryer dubbed ‘Improved Solar Dryer (ISD)’ unit was developed. A conventional active mode hybrid solar dryer nicknamed a ‘Solar Photovoltaic and Electric (SPE)’ dryer was fabricated. In this study, the drying performance of the individual ISD and SPE dryers was evaluated and compared against that of the OSD method. The effect of the individual ISD and SPE dryers on the nutritional content and sensory quality of the solar-dried fruits, namely mangoes and pineapples, was also assessed. The fruits were dried using the ISD and SPE dryers, and OSD methods while following randomized complete block design experimental procedures. Results show that the drying performance of the ISD and SPE dryers was better than that of the OSD method. The SPE and ISD dryers took 10 and 18 hours to effectively dry the fruit products, respectively, as opposed to the 30 hours taken by the OSD method. The mean daily ambient temperature and relative humidity were 26.8oC and 26.7%, respectively. The mean drying air temperatures achieved by the ISD and SPE dryers were 27.7 and 40.3oC, respectively. The mean relative humidity achieved by the ISD and SPE dryers during the entire food drying process were 25.8 and 24.6%, respectively. The mean solar thermal energy recorded for the ISD dryer, SPE dryer, and OSD method were 4795, 5994, and 3595 W/m2 (Watts per square meter), respectively. The results suggest that the SPE dryer exhibited better drying performance than the ISD dryer. The results also confirm that the drying conditions attained by both the SPE and ISD dryers were superior to that of the OSD method. Results confirm an enhanced capacity and superior role of the ISD and SPE dryers in retaining both the sensory quality and nutritional content. Therefore, the ISD and SPE dryers are recommended for drying fruits.