Effect of various dehydration methods and storage on physicochemical properties of guava powder

Present study was carried out to assess the effect of various dehydration techniques on the guava powder, physicochemical and nutritional properties. The fruits of Allahabad safeda variety of guava were used to prepare powder by different dehydration techniques like freeze drying, tunnel drying, sun drying and vacuum drying. Lightness, redness and yellowness of guava powder in terms of L*, a*, b* values was measured. Bulk density of the various powders showed that the freeze dried powder has the minimum bulk density followed by tunnel dried. Significant differences (p < 0.05) in chemical composition of guava powder were observed when prepared by different techniques. The freeze dried powder had the highest ascorbic acid content followed by vacuum dried powder. As expected, lowest concentration of ascorbic acid was found in sun dried powder. The oxidative loss of ascorbic acid during storage was considerably lower in freeze dried powder as compared to others. Freeze dried samples showed maximum mineral contents in terms of potassium (6.2 mg/g), calcium (0.84 mg/g), phosphorus (7.6 mg/g) and iron (0.036 mg/g). Amount of polyphenolics was found in the decreasing order of freeze dried > vacuum dried > tunnel dried > sun dried in guava powder samples. The 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging activity in freeze dried guava powder was found to be 88.1 (%) percent.