Blueberry anthocyanins

Abstract

The objectives of this project were to (1) compare methods of extracting bioactive compounds from whole blueberries and pomace, (2) evaluate the effect of carbohydrate-based and protein-based encapsulants on the release properties of encapsulated anthocyanins during simulated digestion, (3) determine the physical and storage stability of microencapsulated blueberry extract using a selected extraction method and encapsulant, and (4) compare the in vitro properties of encapsulated vs. non-encapsulated extracts.

We extracted and purified anthocyanins from whole blueberries and pomace using acetone-, ethanol- and methanol-based methods. Total monomeric anthocyanins, total phenolics, and antioxidant and enzyme inhibitory activities were measured for both liquid and solid extracts. Liquid and lyophilized acetonic extracts retained enzyme inhibitory activities while ethanolic extracts possessed the highest concentrations of anthocyanins and phenolic compounds. Gum arabic and whey protein isolate were used to encapsulate the lyophilized extracts via spray drying. Gum arabic particles rapidly released phenolic compounds with high antioxidant activity during the simulated gastric digestion, while whey protein microcapsules gradually released phenolics with high antioxidant activity throughout simulated gastrointestinal digestion. Encapsulated ethanolic extracts released the highest concentration of phenolic compounds with antioxidant activity. An energy-efficient encapsulation process using ethanolic pomace extract and whey protein isolate was carried out, and subjected to thermal and photo-degradation upon storage. The total anthocyanins decreased rapidly while the total phenolics increased upon storage. The final antioxidant capacity increased by 10-15%. Photodegradation kinetics was similar to exposure at 37 ºC. The release properties of encapsulated whey protein-blueberry pomace extract were compared against non-encapsulated extract and freeze-dried blueberry juice. The encapsulated and non-encapsulated extracts released more phenolics than the juice. The in vitro antioxidant activity was of the order juice > encapsulated extract > non-encapsulated extract. A product with significant potential as a health-promoting food ingredient can be made from blueberry pomace and whey protein.