Physicochemical quality of twin layer solar tunnel dried tomato slices

The objective of this experimental study was to evaluate the effect of twin layer solar tunnel drying on physicochemical quality of tomato slices. The novelty of this dryer is that it has two layers of trays unlike Hohenheim solar tunnel dryer which makes it to have drying capacity of more than two times compare to type hohenheim solar tunnel dryer with equal collector area. The experiment consists of two (tray position and drying position) factors with two levels of tray position (upper tray (samples exposed to direct solar radiation) and lower tray (samples are exposed to only heated air)) and three levels of drying position (collector out let,middle of the dryer and dryer out let) with three replications. During the experiment 180 kg of Tomato slices of Galilea variety with 5mm thickness were dried in the twin layer solar tunnel dryer. Data on physicochemical quality of tomato were collected and analyzed using SAS (version 9.2). software. From the experimental result; an increase in lycopene and phenolic content retention along the length of the dryer was observed while Vitamin C retention showed a decreasing trend. Large retention of total phenol, lycopene and beta carotene content were observed for the lower tray dried tomato slices compared to the upper tray dried ones. The water activity and PH values of the solar tunnel dried tomatoes were within the safe range from microbial growth, enzymatic and non-enzymatic browning. Compared to sun drying; solar tunnel dried tomatoes showed a much better nutrient retention for all quality parameters which is comparable with the data reported for energy intensive mechanical dryers.