Influence of temperature, pH and salts on rheological properties of bitter almond gum

HOSSEINI, Ebrahim; MOZAFARI, Hamid Reza; HOJJATOLESLAMY, Mohammad; ROUSTA, Esmat

doi:10.1590/1678-457X.18116

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Food Science and Technology

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Research Paper • Food Sci. Technol 37 (3) • July-Sept 2017 • https://doi.org/10.1590/1678-457X.18116 copy

Influence of temperature, pH and salts on rheological properties of bitter almond gum

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

This study focuses on the rheological properties of bitter almond gum (BAG) exudate at different shear rates, concentrations, temperatures, pH, and in the presence of various salts. Rheological data fitted with the Power law model revealed that BAG solutions exhibit non-Newtonian, shear thinning behavior without thixotropic effects at all tested concentrations and temperatures. Apparent viscosity of BAG solutions increased with the increasing gum concentrations and decreased with the increasing shear rate at a specified temperature. The viscosity reached a maximum value at pH 7 and it decreased at lower and higher pH values. Salts caused a reduction in viscosity. Comparatively, CaCl₂ had a more pronounced effect than NaCl at a similar concentration. All treatments had significant effects on rheological parameters.

Keywords:
apparent viscosity; bitter almond gum; gum exudate; rheological parameters

Gum (%w/v)	k (mPa.sⁿ)			n
Gum (%w/v)	5 °C	25 °C	85 °C	5 °C	25 °C	85 °C
1	3.4 ± 0.2^Ca^* * Different small or capital letters show significant difference in the same row or column, respectively (p ≤ 0.05).	2.1 ± 0.5^Cb	0.3 ± 0.1^Cc	0.81 ± 0.00^Ac	0.88 ± 0.02^Ab	0.95 ± 0.07^Aa
2	18.1 ± 0. 2^Ba	11.4 ± 0.4^Bb	2.9 ± 0.3^Bc	0.61 ± 0.02^Bc	0.67 ± 0.01^Bb	0.84 ± 0.00^Ba
3	77.6 ± 0.9^Aa	60.5 ± 0.7^Ab	18.6 ± 0.4^Ac	0.51 ± 0.03^Cb	0.52 ± 0.01^Cb	0.62 ± 0.04^Ca

pH	2	4	7	10
k (mPa.sⁿ)	394 ± 1.1^a^* * Different small letters show significant difference in the same row (p ≤ 0.05).	467 ± 1.1^b	605 ± 3.5^c	410 ± 7.8^a
n	0.55 ± 0.01^ab	0.54 ± 0.00^ab	0.52 ± 0.01^a	0.58 ± 0.04^b

Salt (mM)	Control	NaCl (mM)				CaCl₂ (mM)
Salt (mM)	0	100	200	300	500	5	25	50	100
k (mPa.sⁿ)	605 ± 34^a^* * Different small letters show significant difference in the same row (p ≤ 0.05).	161 ± 3.4 ^b	63 ± 6.9^c	53 ± 1.8^c	43 ± 5.9^c	139 ± 7.5^b	108 ± 0.5^b	60 ± 4.2^c	53 ± 0.6^c
n	0.52 ± 0.05^d	0.66 ± 0.01 ^c	0.76 ± 0.02^b	0.78 ± 0.00^ab	0.82 ± 0.03^a	0.68 ± 0.01^c	0.71 ± 0.00 ^b	0.77 ± 0.01^ab	0.79 ± 0.00^ab
Viscosity (mPa.s)	90 ± 1.5^a	41 ± 0.2^b	24 ± 0.5^c	23 ± 0.3^c	20 ± 0.4^c	38 ± 0.1^b	34 ± 0.4^bc	24 ± 0.3 ^c	22 ± 0.1^c

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[1] *Corresponding author: ebihosseini@kau.ac.ir, hoss_ebrahim@yahoo.com