Quality attributes, moisture sorption isotherm, phenolic content and antioxidative activities of tomato (Lycopersicon esculentum L.) as influenced by method of drying

Abstract

Drying behavior, moisture sorption isotherm (MSI), glass transition temperatures (Tg) and different quality parameters of tomato (Lycopersicon esculentum L.) as affected by drying (sun and solar) was investigated. Drying of tomato under sun displayed a higher rate of moisture loss than those dried in solar drier. However, both the samples finished the drying process after 52 h. Sun and solar dried tomatoes displayed a Tg of −12 °C. When tested against different water activities (Aw), Tg decreased with an increase of Aw. MSI revealed that the relation between Aw and moisture content was found to be exponential (y = 15.959e1.5175x, R2 = 0.9944). Analysis of different quality parameters and antioxidative activity revealed that drying process was known to decrease lycopene, vitamin C, total phenolic and flavonoid content as well as decreased activities was displayed in different antioxidative assays when compared to fresh tomato. Among the samples dried under sun and inside solar drier, there was no significant difference in lycopene and vitamin C content (p < 0.05). However, total phenolic and flavonoid content was higher in solar dried samples. Moreover, antioxidative activity also did not display any difference between the two samples (p < 0.05). More importantly sensory evaluation showed that consumer panelist preferred sun dried samples over solar dried samples. Sun dried sample were more bright red in color with higher a* and L* values than solar dried samples which were darker in color. Therefore, sun drying with some modification can be a promising technique to preserve the perishable tomato and can be effective in preventing the quality losses during drying.