Encapsulation of green tea extracts by different encapsulation techniques

In this study, the aqueous extract obtained from green tea was encapsulated with 3 different techniques: Spray drying, electrostatic extrusion, solid lipid nanoparticle. In each encapsulation technique, different coating materials and different process parameters were studied, and the capsules were characterized. In encapsulation by spray drying, microcapsules were obtained at 120˚C and 140˚C inlet temperatures by using maltodextrin and starch at 20% and 40% (w/v) concentrations as coating material. In encapsulation by electrostatic extrusion technique hydrogel microbeads were obtained in gelation times of 30 and 60 minutes by using sodium alginate at different concentrations (3.5% and 4.5% (w/v)) as a coating material. In the solid lipid nanoparticle technique, by using carnauba wax and beeswax as coating material, capsules were formed with different emulsion acquisition times (5 min and 10 min) and with different extract amounts (15 mL and 30 mL). The effects of coating materials and some applied process parameters on the encapsulation efficiency were investigated and bulk density, solubility, particle size, SEM, water activity, moisture, color, antioxidant activity, thermal stability analyzes were performed on the capsules. In addition, the stability of the microcapsules throughout the gastrointestinal tract was investigated with in vitro digestion model. It was determined that the encapsulation yield was between 35.19-89.28% in the spray drying technique, the encapsulation efficiency was between 38.93-78.32% in the electrostatic extrusion technique, and between 30.38%-52.71% in the SLN-melt dispersion technique. It was determined that the highest yield belonged to the particles obtained by using MD as the coating material. The increase in the coating material concentration and gelation time increased the %EE (P<0.05). The sizes of the particles obtained by spray drying, electrostatic extrusion and SLN-melt dispersion techniques are between 8.44-30.80 µm, 362.90-406.13 µm and 0.31-119.19 µm, respectively and the surface weighted average diameters of the microparticles obtained by MD compared to NS was found to be lower. It was determined that the increase in coating material concentration and gelation time increased the diameters of the hydrogel microbeads. It was determined that the temperatures at which thermal degradation started in the encapsulated samples were ~200°C and above in all three techniques. For all three techniques, the percentage of bioaccessibility of microparticles (78.29-91.03%) was found to be higher than the non-encapsulated sample (69.13%). According to the results obtained from this study; it was observed that the obtained capsules were in micron size (0.31-406.13 µm) in all three methods and the microcapsules had different characteristics depending on the technique and the coating material used. In addition, it was determined that the microcapsules obtained by all three techniques were preserved throughout the gastrointestinal tract compared to the non-encapsulated green tea extract. In addition, it has been demonstrated that encapsulation increases the thermal stability of the extracts, making it more suitable for use in many food processing processes.