Impact of In Vitro Gastrointestinal Digestion on the Bioaccessibility of Phytochemical Compounds from Eight Fruit Juices

Fruits contain a number of useful substances including antioxidants. Their bio-accessibility after passing through the digestive tract is of primary importance when considering their benefits. In this respect, we investigated the effect of in vitro digestion on the phytochemicals of eight fruit juices. Freshly prepared juices from pomegranate, orange and grapefruit were used as well as commercially available juices from cherry, black grapes and aloe vera, blackberry and chokeberry, and two types of chokeberry and raspberries. Spectrophotometric and HPLC methods were used in order to analyse the sugar content, the total phenolic (TPC) and flavonoid contents (TFC), anthocyanins, phenolic acids and antioxidant activity. Principle component analysis was used to explain the differentiation among the types of fruit juice. Sugar recovery variation was between 4–41%. The bio-accessibility of TPC ranged from 13.52–26.49% and of flavonoids between 24.25–67.00%. The pomegranate juice and the juice of black grapes and aloe vera kept 58.12 and 50.36% of their initial anthocyanins content, while for the other samples less than 1.10% was established. As a result, a maximum of 30% remaining antioxidant activity was measured for some of the samples, but for most this was less than 10%. In conclusion, fruit juices are a rich source of biologically active substances, but a more detailed analysis of food transformation during digestion is needed.