Transfer and Mass Balance of Ellagitannins, Anthocyanins, Flavan-3-ols, and Flavonols during the Processing of Red Raspberries (Rubus idaeus L.) to Juice

The putative health benefits of raspberries and raspberry-based products are potentially attributable to the presence of polyphenolic compounds, such as ellagitannins, anthocyanins, flavanols, and flavonols. Their content in the products of raspberry processing into juice may be affected by the fruit cultivar, technological process parameters, and the properties of the polyphenolics themselves. The objective of the study was to investigate the composition and quantity of the above polyphenolics in raspberries and the products of their processing (that is, juice and press cake, including its seed and seedless fractions). The study also examined the relationship between the molecular mass of ellagitannins and their transfer to juice. The average percentage contributions of ellagitannins, anthocyanins, flavanols, and flavonols to total polyphenolics in the fruits were 64.2%, 17.1%, 16.9%, and 1.8%, respectively. Analysis of raspberry products showed that the dominant compounds in juice were anthocyanins, with 65.1% contribution to total polyphenolics, while in raspberry press cake, they were tannins (98.0%, mainly ellagitannin including lambertianin C and sanguiin H-6). As shown by our mass-balance calculations, on average, 68.1% of ellagitannins and 87.7% of flavanols were retained in press cake, especially in its seedless fraction. In addition, a significant negative correlation was found between the molecular mass of ellagitannins and their transfer to juice. An increase in molecular mass from 1568 to 2805 Da resulted in a more than 10-fold decrease in ellagitannin transfer.