Encapsulation of flaxseed oil within native and modified lentil protein-based microcapsules

• Entrapment unmodified lentil protein isolate led to the lowest surface oil.
• Encapsulation protected the oil from oxidation compared to the free oil.
• Partially hydrolyzed lentil proteins were not effective as an encapsulating agent.

The physical properties of lentil protein-based maltodextrin microcapsules with entrapped flaxseed oil was investigated using native (n-LPI) and pre-treated (heated, un-hydrolyzed (u-LPI); and heated, hydrolyzed (h-LPI)) lentil proteins and as a function of oil load (10, 20 and 30% of total solids). Specifically, the moisture, water activity, surface oil and entrapment efficiency (EE) were assessed, along with droplet size and emulsion morphology of all formulations. Moisture (< 6%) and water activity (< 0.2) of all capsules were characteristics of dried powder ingredients. Light microscopy imaging of the emulsions, revealed that the h-LPI had slightly larger oil droplets than the n-LPI and u-LPI, which both appeared similar. Findings were confirmed by light scattering, where droplet sizes were 6.7, 4.2 and 4.2 μm for the h-LPI, u-LPI and n-LPI stabilized emulsions, respectively. Overall capsules prepared from h-LPI showed significantly higher surface oil and lower EE than both the n-LPI and u-LPI materials. Furthermore, as the oil content increased, overall surface oil became higher and EE became lower. Based on testing, capsules prepared using n-LPI with 10% oil loading was found to have the lowest surface oil content (~ 3.7%) and highest EE (~ 62.8%) for all formulations, and was subjected to an oxidative storage stability test over a 30 d period vs. free oil. The encapsulation process proved to be effective at lowering the production of primary and secondary oxidative products than free oil.