Effect of drying methods and pre-treatments on phytonutrients of tomato slices

Tomato slices pre-treated with 4% potassium metabisulphite (KMS) and dried by hot air drying at 58°C and freeze drying at 0.008 m Bar vacuum were assessed for phytonutrient quality. Freeze drying was found to retain better antioxidant activity and phytonutrients in tomato slices compared to the hot air dried tomato slices. Sulphur dioxide exerted beneficial effect (antioxidative) on retention of phytonutrients during hot air drying but had negligible effect during freeze drying. Total carotenoids in pretreated hot air dried tomato slices were 17.49% higher than control samples whereas in case of freeze drying, carotenoids were 3.01% higher in control samples than pretreated samples Rehydration ratio was the highest in pretreated freeze dried tomato slices (6.69) compared to pretreated hot air dried tomato slices (5.77). Maximum nutrients were retained by KMS treated slices during storage.