Study on biochemical properties of dehydrated coriander leaves at different drying conditions

Abstract

A study on biochemical properties (chlorophyll content, vitamin C and rehydration characteristics) of dehydrated coriander leaves in relation to was conducted at three drying conditions, namely, pretreatment, loading density and drying methods. A greenhouse type solar dryer (5m x 3m x 2.3m) of modified quonset shape covered with 200 micron UV stabilized polyethylene sheet was developed for dehydration of leafy vegetables. Dehydration of fresh coriander leaves at three levels of pretreatments viz. (i) dipping in a solution (leaves to water ratio: 1:5) containing 0.1% MgCl2 + 0.1% NaHCO3 + 2% KMS in distilled water for 15 min at room temperature, (ii) blanching in boiling water containing 0.5% sodium metabisulphite for 2 min, and (iii) untreated (control); three levels of loading density, viz. 2.0, 2.5 and 3.0 kg/m2; and two levels of drying methods, viz. greenhouse type solar dryer and in open sun was done. The higher values of rehydration ratio, chlorophyll content and ascorbic acid content under greenhouse type solar dryer were observed as compared to open sun drying. The product quality was found to be most acceptable of coriander leaves treated in the solution of 0.1% MgCl2 + 0.1% NaHCO3 + 2% KMS, and dried under GSD using 2.5 kg/m2 loading density. The developed greenhouse type solar dryer can be successfully used for dehydration of coriander leaves.