Effect of sun drying and oven drying on quality of Roselle (Hibiscus sabdariffa linn)

Boo, Ju Lie (2009) Effect of sun drying and oven drying on quality of Roselle (Hibiscus sabdariffa linn). Universiti Malaysia Sabah. (Unpublished)


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The effect of sun drying and oven drying (50°C; 60°C and 70°C) on the proximate composition, physicochemical properties, microbiological quality and sensory quality of fresh and dried Roselle (Hibiscus sabdariffa L.) calyxes was studied. The time required to obtain the desired moisture content decreased as drying temperature increased. Crude protein crude fiber, crude fat and carbohydrate were found to decrease in all heat treatments except ash contents. Carbohydrate was the most abundant components found in Roselle calyxes. Total soluble solids and pH value increased while citric acid decreased during the drying process. Anthocyanins content were decreased during drying but anthocyanins retention increased as drying temperature increased. Abrupt reduction in ascorbic acids was observed during drying. Oven drying at 70°C gave the highest retention for most of the nutrients such as ash, crude protein, organic acids anthocyanin and ascorbic acid. Colour values (L*, a*, b*, chroma) of Roselle caylxes increased during the drying process. The colour values of sun dried sample appeared to be higher as compared to other dried samples. Microbiological analysis showed that dried Roselle calyxes were almost free from microbes. In multiple comparison test, sensory evaluation showed that lower drying temperatures such as sun drying treatment produced retained closer sensory properties to the fresh sample. In hedonic scale test, oven drying at 60°C gave the highest mean liking for sensorial attributes. Overall, oven drying at 60 °C and 70°C seemed to be the better treatment among the drying methods considered in this study. However, the choices within this two drying methods depend on the purpose of the dried Roselle calyxes that will eventually be used. Oven drying at 60°C was suitable when the dried Roselle calyxes were used as food products since oven 60°C treatment gave the highest liking for the sensory attribute tested. Meanwhile, oven drying at 70 °C was preferable when the dried Roselle calyxes were used as nutritional food since oven 70°C treatment gave the highest retention on most of the nutrients tested.

Item Type: Academic Exercise
Uncontrolled Keywords: Roselle, Hisbiscus sabdariffa Linn., Sun drying method, Oven drying method
Subjects: T Technology > TP Chemical technology > TP1-1185 Chemical technology > Food processing and manufacture
Divisions: SCHOOL > School of Food Science and Nutrition
Depositing User: ADMIN ADMIN
Date Deposited: 18 Jun 2012 17:40
Last Modified: 23 Oct 2017 11:41
URI: http://eprints.ums.edu.my/id/eprint/4234

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