Multifaceted roles of foam-mat freeze-dried catechins nanoencapsulation to enhance catechins stability and bioaccessibility, and quality of green tea catechins-fortified milk

Catechins, widely used as functional ingredients and health supplements, face usage limitations due to their poor stability and bioaccessibility. In this study, encapsulation techniques including nanoemulsion and foam-mat freeze-drying were utilized to enhance the stability and bioaccessibility of catechins. Catechins nanoemulsion (CaNE) was ultrasonically fabricated and foam-mat freeze-dried CaNE (FD-CaNE) was prepared by mixing with a blend of maltodextrin and gum arabic as wall material and foaming with hydroxypropyl methylcellulose before freeze drying. Unencapsulated catechins (UN-Ca), CaNE, and FD-CaNE were fortified in pasteurized milk to improve its functional properties. FD-CaNE was shown to be the best at preserving total flavonoid content (TFC) and catechins' antioxidant activity (AA), retarding lipid oxidation, and inhibiting bacterial growth. In vitro gastrointestinal digestion test, digested CaNE and FD-CaNE showed better bioaccessibility of catechins by having higher percentage of TFC recovery and AA than the digested UN-Ca. This study has proved that FD-CaNE can be used as bioactive food ingredients to enhance the stability and bioaccessibility of catechins in food matrices and digestive system, and to improve quality and shelf life of catechins-fortified milk.