Soy Protein–Gum Karaya Conjugate: Emulsifying Activityudand Rheological Behavior in Aqueous System and Oil in WaterudEmulsion

摘要

The main objective of this study is to investigateudthe effects of mixing and conjugation of soy proteinudisolate (SPI) with gum karaya on the characteristics of theudhybrid polymer (protein–gum) in both aqueous systemsudand oil-in-water (O/W) emulsions. It was hypothesizedudthat the covalent linkage of gum karaya with SPI wouldudimprove the emulsifying activity and rheological propertiesudof both polymers. Conjugation occurred under controlledudconditions (i.e., 60 °C and 75 % relative humidity, 3 days).udThe conjugated hybrid polymer produced smaller dropletudwith better uniformity, higher viscosity and stronger emulsifyingudactivity than native gum karaya, suggesting the conjugatedudpolymer provided a bulkier secondary layer withudmore efficient coverage around oil droplets, thereby inducingudstronger resistance against droplet aggregation andudflocculation. Emulsions containing the native gum karayaudproduced the largest droplet size among all prepared emulsionsud(D3,2 = 8.6 μm; D4,3 = 22.4 μm); while the emulsionudcontaining protein–gum conjugate (1:1 g/g) had the smallestuddroplet size (D3,2 = 0.2 μm; D4,3 = 0.7 μm) with lowerudpolydispersity. The protein–gum conjugate (1:1 g/g) alsoudshowed the highest elastic and viscous modulus, the lowest polydispersity (span) and the highest emulsifying activityudamong all native, mixed and conjugated polymers. Therefore,udthe percentage of gum karaya used for production ofudO/W emulsion can be decreased by partially replacing itudwith the conjugated gum.