Assessment of emulsifying ability of almond gum in comparison with gum arabic using response surface methodology

The emulsifying properties of almond gum from Prunus dulcis were assessed in comparison with gum arabic from Acacia senegal. Interfacial properties were preliminary evaluated by pendant drop method, while emulsifying ability was quantified in terms of mean droplet size of O/W emulsions prepared at different intensity levels of high pressure homogenization as well as of stability of resulting optimized emulsions. Response surface methodology (RSM) was used to determine the optimum emulsification conditions for minimum mean emulsion droplet size. Homogenization pressure (100-300 MPa), number of passes (1-10 passes) and gum concentration (5, 7.5 and 10% w/w) were the factors investigated. Experiments were designed according to a three-level, three-variable Box-Behnken design (BBD), and a second-order polynomial model was developed for the response variable using multiple linear regression analysis, which resulted to be very accurate both for almond gum (R-2 = 0.979) and for gum arabic (R-2 = 0.993). Results showed that almond gum exhibited good emulsifying abilities, yet different from gum arabic. The measured interfacial properties of almond gum showed slower dynamics of adsorption and reorganization at the oil-water interface. Coherently, the optimum emulsification conditions determined by RSM required for almond gum a lower emulsifier concentration (5.7%) than for gum arabic (8.4%), but the use of gum arabic allowed for a smaller mean droplet size at lower intensity of high pressure homogenization treatment. Remarkably, the stability of 10% oil emulsions using almond gum as emulsifier was comparable to those using gum arabic, for gum concentrations in excess of 5%. (C) 2013 Published by Elsevier Ltd.