Solar drying of different tomato hybrids for powder production
2017
Phon, S. | Buntong, B. | Acedo, A. L. Jr | Easdown, W. | Hughes, J. A. | Keatinge, J. D. H.
This study evaluated two types of simple solar driers, an RUA solar dryer with a circulating chimney (SD-CC) and a commercial-scale tunnel-type solar dryer (SD-TT), for drying tomatoes of two AVRDC advanced processing lines ('CLN3670B' and 'CLN3125L-5X65'). A local cultivar ('KK3') and open sun drying were included as controls. After drying to about 10% moisture content, the dried tomato slices were processed into powder following a standard protocol and analyzed for physicochemical properties. SD-CC and SD-TT driers maintained higher temperatures than under-the-sun drying conditions. SD-CC had higher relative humidity (RH) compared with SD-TT and sun-drying conditions. As a result, fruit dried slowest in SD-CC and fastest in SD-TT regardless of cultivar. Powder characteristics differed with cultivar and drying conditions. Powder yield was markedly higher in SD-CC than in the two other drying treatments. It was also much higher in the two AVRDC lines than in 'KK3'. Water activity and pH of the powder did not differ widely with treatment, and ranged from 0.25 to 0.36 and 3.98 to 4.64, respectively. Yet, ash content only varied from 6 to 7%. Marked variations in fat and carbohydrate contents were obtained. 'KK3' generally had higher fat contents and lower carbohydrate contents than the two AVRDC lines, regardless of drying conditions. The results indicate that the SD-TT drier was more promising than SD-CC in producing better-quality tomato powder. Also, the better responses of the AVRDC lines than the local variety imply that breeding can be harnessed to develop suitable varieties for drying and powder processing.
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