New research published in the Journal of Food Engineering has suggested that the thermal cross-linking of whey protein stabilised oil in water (o/w) emulsions with spray drying could produce high oil-content powders for use as functional ingredients.
Led by Yang Wang from Monash University in Australia and Xiamen University, China, the pan Asia-Pacific research team systematically studied the characteristics and stability of powders created by the encapsulation of DHA-containing fish oil – finding that thermal cross-linking of a whey protein stabilized emulsion produced powders with high oil content and good stability.
“The outcomes from this study can provide a better understanding to benefit the production of DHA-oil microcapsules through a better product design for the food and pharmaceutical industries,” wrote the team.
“The strategy could be used to produce high oil content particles with improved storage stability,” they added.
Oil-rich powders
Wang and colleagues tested the encapsulation of fish oil containing 50% DHA using protein-based emulsion systems and a mono-disperse droplet spray dryer.
Oil contents of between 33% a and 90% on dry basis were successfully encapsulated by whey protein isolate (WPI), using the jet spray dryer, said the team.
The emulsion properties and the corresponding dry particle properties of different samples were analysed.
“For high oil content formulas (83%–90% on dry basis), thermal treatment was employed to produce a cross-linked, protein-stabilized oil-water interface prior to spray drying,” they noted.
The authors reported a better encapsulation efficiency when relatively high protein contents of between 50% and 67% on a dry basis were used.
“Comparing the relatively high oil/protein ratio emulsions (sample 1, 2, 3) with relatively low oil/protein ratio emulsions (sample 4, 5, 6), samples with high protein contents showed better oil-droplet distribution and stability, especially for samples 4 and 6 (…) with good emulsification and stability to maintain the emulsions,” said the team.
Under tests in a simulated gastric fluid, Wang and colleagues also reported that particle samples with higher oil content slowly leaked the oil into the solution while the particle shells were quickly dissolved for higher protein content samples.
“Thermally treated precursor emulsions might have formed a less permeable shell to protect the core oil from outside environment, so that during the storage test, fish oil was better protected against oxidation,” they wrote.
Indeed, Wang and colleagues concluded that thermal cross-linking of the whey protein prior to spray drying greatly improved particle properties, “and can be used to produce ultra high DHA oil content powders.”
Source: Journal of Food Engineering
Volume 175, Pages 74–84, doi: 10.1016/j.jfoodeng.2015.12.007
“Micro-encapsulation and stabilization of DHA containing fish oil in protein-based emulsion through mono-disperse droplet spray dryer”
Authors: Yang Wang, et al