| T Mahendran
Department of Agricultural Chemistry, Faculty of Agriculture, Eastern University of Sri Lanka, Chenkalady
Abstrsact
Dehydration of guava juice into powdered particles gives a considerable reduction in volume and is an effective method of prolonging the shelf life. Therefore, a research study was conducted to determine the effect of different drying methods and the addition of drying aids on the physico-chemical proper-ties and sensory characteristics of dehydrated guava concentrate. Instant guava-drink-powder samples were obtained by dehydrating the concentrated guava juice using freeze drying, spray drying and tun-nel drying techniques. Guava juice at 10.5°Brix was used to prepare the fruit powders. A significant reduction (p<0.05) in titratable acidity of 0.22 % as citric acid and an increase in pH of 0.44 after dry-ing of guava juice indicated that some acids were lost during the drying process. The oxidative loss of ascorbic acid was considerably lower in freeze drying (18.8%) compared to tunnel drying (32.2%). Spray dried powders were obtained from the guava juice with different maltodextrin concentrations as drying aids. When 30% maltodextrin was added to guava juice, the solubility of powder was 95% whereas, adding 60% maltodextrin decreased the solubility to 86%. The chromametric parameters L* (lightness), a* (redness) and b* (yellowness) were found to be significantly (p<0.05) affected by drying methods. Twenty trained sensory panellists ranked the juice prepared from the freeze dried powder as the highest and there were no significant differences (p>0.05) between the juice prepared from spray drying of guava juice upto 50% added maltodextrin. The freeze dried product had superior nutritional and sensory qualities, however spray dried product was stable and more economical to produce free-flowing guava powder with good stability.
Key words:Freeze drying, guava-drink-powder, maltodextrin, spray drying
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