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 (100e300 MPa), number of passes
(1e10 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 BoxeBehnken 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 (R2 ¼ 0.979) and for gum arabic (R2 ¼ 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%.