Effects of osmotic dehydration pre-treatment on process and quality of freeze-dried strawberries (Fragaria x ananassa var. Mencir)

Abstract

The freeze-drying of fruits is one alternative to increase the added value of fresh fruit, extend the shelf life which the product, and still have properties like fresh fruit. Osmotic dehydration pre-treatment can be applied before drying techniques to produce a new product, maintain nutritional and sensory quality, and improve the drying process. In this research, the effects of osmotic dehydration on freeze-drying performance and the quality characteristics of freeze-dried strawberries were evaluated. Freeze-dried strawberries were made using fresh strawberries without pre-treatments and pre-treatments by osmotic dehydration (OD) with the freeze-drying method. The treatment of materials and processes used were the duration of storage in the freezer of 36 to 48 h; vertically cutting strawberry before OD; osmotic dehydration agents with a concentration of 50°Brix; immersion time for 30 min at temperature a 30°C; and freeze-drying time of 24 h. Results of each treatment in terms of physical quality parameters (color of skin fruit (L*a*b*), change of color (ΔE), and hardness) and phytochemical quality parameters (water content, vitamin C, total phenolic content, and antioxidant activity by DPPH) were compared and discussed. The osmotic dehydration process causes a water loss of 13%, has a significant difference on the parameters of colors (redness and color of change), hardness, vitamin C, total phenolic content, and antioxidant activity by DPPH.