Effect of kappa- and iota-semi refined carrageenan coating on osmotic dehydration of guava

Choong , Kar Kei (2012) Effect of kappa- and iota-semi refined carrageenan coating on osmotic dehydration of guava. Universiti Malaysia Sabah. (Unpublished)

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Abstract

The main objective of this study was to determine the effect of different kappa and iota-semi-refined carrageenan (SRC) concentration and dipping time on the quality of osmotic dehydrated guava in terms of water loss, solid gain, total soluble solid, moisture content, water activity, and sensory properties. Two sets of 3 X 2 Factorial Design with three coating concentrations (1% w/v, 1.5% w/v and 2% w/v) and two dipping time (60 sand 120 s) were employed. Osmotic dehydration condition was fixed at 600 Brix sucrose solution and 32°C, where the ratio of guava sample to sucrose solution was fixed at 1:10 (w/w). During mass transfer, iota-SRC was found to be instable and experienced dissolution into osmotic medium, causing negative solid gain and increased water loss (p<0.05). However, increasing dipping time to 120 s led to reduced water loss (p<0.05) in iota-SRC coated sample. In contrast, kappa-SRC was found to lowered water loss (p<0.05) with increased coating concentration due to moisture barrier effect. Kappa-SRC was also found to be more brittle than iota-SRC that it caused detachment of coating upon long hour of immersion in osmotic medium. Although both kappa- and iota-SRC were found to demonstrate potential in lowering total soluble solid, kappa-SRC had no effect in controlling solid gain (p>0.05). The coating formed by 2% of kappa- and iota-SRC was found to inhibit moisture vapour evaporation during oven drying and resulted in higher moisture content and water activity (p<0.05) which subsequently reduced the firmness of the dried guava (p<0.05). However, iota-SRC was able to enhance firmness of dried guava (p<0.05) at 1% and 1.5% of coating concentration, which was not observed for kappa-SRC. In addition, SRC had no effect on the color of dried guava and did not affect much on the sensory attributes being studied (p>0.05). Nonetheless, sensorial result showed that kappa-SRC coating was able to reduce the dryness of guava slice (p<0.05), indicating its ability to prevent excessive drying of fruit sample. In overall, it was found that concentration of SRC produced more pronounced and consistent effect than dipping time during osmotic dehydration as well as various quality aspects of final product. Increased coating concentration in iota-SRC was found to enhance mass transfer to a certain extent, but adversely affected the qualities of dried guava due to additional barrier to moisture evaporation during oven drying, particularly kappa-SRC. Generally, 1% of kappa SRC was found to be a better coating considering its stability during osmotic dehydration and beneficial coating effect during oven-drying process, as well as higher acceptance by sensory panels.

Item Type:Academic Exercise
Uncontrolled Keywords:iota-semi-refined carrageenan, oven-drying process, kappa, guava, osmotic dehydration
Subjects:T Technology > TX Home economics > Nutrition. Foods and food supply
Divisions:SCHOOL > School of Food Science and Nutrition
ID Code:7901
Deposited By:IR Admin
Deposited On:31 Dec 2013 11:13
Last Modified:31 Dec 2013 11:13

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