Effect of Stevia rebaudiana Bert. Addition on the Antioxidant Activity of Red Raspberry (Rubus idaeus L.) Juices

The demand for antioxidant-rich beverages is steadily expanding. At the same time, the possibility of manufacturing products with reduced sugar content, sweetened with natural ingredients, represents a decisive aspect of obtaining quality products with health benefits. Stevia rebaudiana Bertoni (stevia) is a natural sweetener that can help to control caloric intake and is also a good source of antioxidant compounds. The present study was designed to assess the feasibility of producing high-quality berry juices sweetened with dry-grinded stevia leaves or their crude extract. The effect of the stevia supplementation on the antioxidant activities of raspberry juices was determined at two different production steps by means of the Folin–Ciocalteu, the oxygen radical absorbance capacity (ORAC), and the cellular antioxidant activity (CAA) assays. The addition of stevia significantly increased the antioxidant activity of the juices and resulted in significantly higher ascorbic acid and total phenolic content. A positive correlation was observed between ORAC, CAA, and total phenolic values. These findings show that supplementation with stevia not only promotes a healthy diet by reducing sugar intake but may also enhance the antioxidant potential of the beverage.