Malaysian Applied Biology Journal

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47_05_23

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Malays. Appl. Biol. (2018) 47(5): 189–196

 

RHEOLOGICAL PROPERTIES OF AQUEOUS DISPERSIONS

OF OKRA (Abelmoschus esculentus) GUM


AIN NADIAH SOFIAH AHMAD KHORAIRI1, NOOR-SOFFALINA SOFIAN-SENG1*,

NURUL SHAHIRAH AZIZ1, NUR AIN NABILA AZALI1, KHAIRUL FARIHAN KASIM2

and NOORUL SYUHADA MOHD RAZALI1


1School of Chemical Sciences and Food Technology, Faculty of Science and Technology,

Universiti Kebangsaan Malaysia, 43600 UKM BANGI, Selangor, Malaysia

2School of Bioprocess Engineering, Universiti Malaysia Perlis (UniMAP),

01000 Kangar, Perlis, Malaysia

*E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it


Accepted 17 October 2018, Published online 30 November 2018


ABSTRACT

This study aims to characterise the rheological properties of okra (Abelmoschus esculentus) aqueous dispersion. Okra gum was extracted by water extraction and was freeze dried before reconstituting to the desired concentration. Proximate analysis of freeze-dried okra gum showed that the major constituent is carbohydrate (84%) and some protein (6%). The effect of mucilage concentration (0.25-1%), pH (3-8) and ionic strength (0-0.2 M) on the rheological properties was also evaluated. Okra gum dispersion exhibited shear-thinning characteristic. Apparent viscosity increased as the okra gum concentration increased. Okra gum concentration had an increasing trend towards k (consistency index), whereas ionic strength and pH displayed no apparent trend. Generally, within the frequency range tested, the okra gum dispersion’s storage modulus (G’) were larger than the loss modulus (G”), except for dispersion with 0.15M NaCl which had a crossover of G’ and G” at higher frequency. However, the gum dispersion was relatively insensitive to ionic strength as the apparent viscosity was within a limited range. Okra gum dispersion at pH 8 resulted in much higher G’ and G” compared to the other pH. Thus, okra gum can be potentially used as food thickener, although it can be influenced by the pH of the food medium.

Key words: Aqueous dispersion, mucilage, Okra gum, rheology

 

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