Experimental Study of the Effects of Convective Drying on Some Selected Vegetables

Aim: This work gives the reports on experimental study of the effects of drying on some selected vegetables, namely fluted pumpkin (specimen I), spinach (specimen II), lettuce (specimen III), and waterleaf (specimen IV).

Methodology: The vegetable specimens were dried at regulated drying temperatures of 323K, 333K, and 343K, and the percentage amount of water, fat, crude fibre, ash, protein, and carbohydrate, as well as the fungi and bacteria counts in the vegetable specimens was determined at these temperatures.

Results: The results revealed that the amount of water in the vegetable specimens reached 0% earlier at the regulated drying temperature of 343K than at the other regulated drying temperatures. The results also indicated that the dried vegetable specimen II has highest fat content of 8.2%, the dried vegetable specimen III has highest crude fibre content of 14.5%, the dried vegetable specimen IV has highest ash content of 18.6%, the dried vegetable specimen I has highest protein content of 30.3%, and the dried vegetable s specimen III has highest carbohydrate content of 42.2% at the regulated drying temperature of 323K. The same trend of results was obtained for the regulated drying temperatures of 333K and 343K. Furthermore, the results showed that at the regulated drying temperature of 323K, the dried vegetable specimen III has the lowest bacteria counts of 4.3 x 107 CFU/g. The trend of result obtained for the regulated drying temperatures of 333K and 343K is similar to that of the 323K. At the regulated drying temperature of 323K, the dried vegetable specimen II has the lowest bacteria counts of 1.7 x 107 CFU/g. The same trend of results was obtained for the regulated drying temperatures of 333K and 343K.

Conclusions: Drying has effects on the percentage amount of fat, crude fibre, ash, protein, and carbohydrate in the vegetable specimens. The microbial counts and the fungi counts decrease when the temperature increases. The present work can be applied in food engineering industries, and engineering in agriculture.