Studies on osmotic dehydration of guava (Psidium guajava L.)

Abstract

Guava (Psidium guajava L.) is one of the commercial fruits of tropical as well as subtropical regions. It occupies an important place in the horticultural wealth of India and ranks fourth with respect to area and production after mango, banana and citrus. It is a rich source of vitamin C and pectin. Guava is a seasonal fruits with very short shelf life, therefore it needs to be preserved as self stable value added products using drying technology such as osmotic dehydration. Osmotic dehydration process involves subjecting fruit pieces to aqueous solution of sugar with high osmotic pressure which removes 30-50% of the water prior to drying. The inclusion of osmotic process in conventional dehydration has two major objectives quality improvement and energy savings. This studies was aim to know the effect of syrup concentrations (50, 60 & 700 Brix) and duration of osmosis (4, 18 & 24 hours) on weight loss, solid gain and yield of osmotically dehydrated guava slices of varieties Allahabad Safeda and Pink Flesh. Data was analysed using Factorial Completely Randomized Design (FCRD). Observation on physic-chemical composition and sensory characteristics were taken. Variations were observed with respect to fruit size, TSS, ascorbic acid content, acidity and sugar content in fresh fruits of variety Allahabad Safeda and Pink Flesh. Statistically significant variations were observed for weight loss, moisture loss, solid gain, yield, sugars, ascorbic acid content, titrable acidity, NEB and sensory quality parameters. In osmotically dehydrated gyava slices the values ranged f weight loss (22.73 to 34.55%), moisture loss (36.16 to 53.24%), solid gain (6.24 to 13.97%), yield (32.37 to 39.67%), reducing sugar (29.57 to 38.64%), non-reducing sugar (8.37 to 23.68%) and total sugar (39.02 to 63.32%). Increase in the syrup conentration from 50 to 70 0Brix and duration of osmosis from 4 to 24 hours resulted in increase in weight loss, moisture loss, solid gain and yield in the guava slices. In general, an increase in reducing sugar and non-enzymatic browning (NEB), and decrease in non-reducing sugar and overall sensory score was observed during storage. Dehydrated guava slices were acceptable after 4 months of storage at room temperature. For osmotic dehydration, Allahabad Safeda was rated significantly superior over Pink Flesh.