Effect of lentil proteins isolate concentration on the formation, stability and rheological behavior of oil-in-water nanoemulsions

- Stable oil-in-water nanoemulsions were formed with 0.5-5 wt% lentil protein isolate.
- Nanoemulsion with 2 wt% protein was most stable.
- With 3-5 wt% protein, nanoemulsions were transformed into strong viscoelastic gels.
- Gelled nanoemulsions showed a two-step yielding behavior upon strain application.
- Excess lentil proteins formed a strong protein-droplet network upon storage.

The formation, stability and rheology of 5 wt% oil-in-water nanoemulsions as a function of lentil protein isolate concentration (0.5-5 wt%) at pH 3.0 was investigated for 28 days. All nanoemulsions, except 1 wt% protein, showed bimodal droplet size distribution where the larger diameter peak was ascribed to protein aggregates and entrapped oil droplets. The average droplet size for all nanoemulsions measured from the lower diameter peak ranged from 161 to 357 nm, which did not change over 28 days. Stable flowable nanoemulsions were formed at 1-2 wt% protein concentrations. Nanoemulsions with 3 and 5 wt% protein formed strong non-flowable gels which showed a two-step yielding behavior during strain-sweep rheology, indicating gel formation by interconnected clusters of proteins and oil droplets. This study demonstrated that lentil protein has a potential to be utilized as an emulsifier in nanoemulsions, as well as in the formation of emulsion gels at higher protein concentrations.

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