α-tocopherol encapsulation in ora-pro-nobis (Pereskia aculeata Miller) mucilage-whey protein isolate microparticles

Abstract

Microparticles of whey protein isolate (WPI) and ora-pro-nobis mucilage (OPN) encapsulated α-tocopherol were made using long-chain unsaturated (e.g., canola oil (CA)) or medium-chain saturated oil (e.g., coconut oil (CO)) as the carrier oil. Microparticleswere produced from CO- or CA-in-water emulsions by freeze-drying emulsions with various ratios of WPI/OPN. Before freeze dying, emulsions exhibited Newtonian or shear-thinning behavior. Smaller values of mean droplet diameter (230.37 nm) and polydispersityindex (0.144), and higher zeta potential modulus (-49.63 mV) were found for treatments with lower OPN content and prepared with CO. Drying yields for freeze-dried emulsions ranged between 74.1% to 87.1% w/w, depending on the biopolymers ratio and varied depending on whether CA or CO was used as the carrier. WPI:OPN ratios (between 23:1 and 7:1) nor oil phase (CO or CA) significantly affected the physical properties (e.g., oil retention, water content, and activity) of the dried powder between treatments. Higher powder bulk density (0.22 g•cm-3) and encapsulation efficiency (79.8% w/w) were obtained from freeze-drying CO,comparedtoCA-in-water emulsions and with higher concentrations of OPN. The surface roughness of the microparticles increased with increments in OPN concentration, regardless the carrier oil used, as observed by scanning electron microscopy.Over 35 days, α-tocopherol retention and degradation kinetics differed between CO and CA and was dependent on relative humidity. Absorbance peaks characteristic of groups found in the structure of proteins, carbohydrates, α-tocopherol and lipids (CA and CO) were observed in the infrared spectroscopy spectra. Bioaccessibility of encapsulated α-tocopherol was higher with CA WPI/OPN (23:1) (55.0±1.89%) compared to CO WPI/OPN (23:1) (42.4±1.78%), while the rate of α-tocopherol release and induction time for release were statically equal. It is concluded that the CO WPI:OPN(23:1) treatment was the one that presented the best performance for a possible industrial application, since it maintained high bioactive retention during the storage stability test and high bioaccessibility.