Soluble and insoluble-bound phenolics and antioxidant activity of various industrial plant wastes

The potential of selected industrial food wastes from juice and nut production including apple peel, apple pomace, pomegranate peel, pomegranate seed, chestnut shell, and black carrot pomace as resources for natural antioxidants was investigated. Soluble free and insoluble-bound phenolics were extracted from the wastes and analyzed for total phenolic and flavonoid contents, phenolic profile and antioxidant activity. Total phenolic and total flavonoid contents of wastes were positively correlated with their antioxidant activity. The highest total phenolic and antioxidant activity were determined in soluble fraction of pomegranate peel due to a significant amount of punicalagin derivatives. Pomegranate peel and seed had the most phenolics and flavonoids in soluble form while other wastes had more than 45% of total phenolics in insoluble-bound form. Chestnut shell showed more antioxidant activity in insoluble-bound fraction compared to that of its soluble fraction. These findings showed that not only soluble but also an insoluble-bound fraction of the industrial wastes has good potential for valorization as a source of natural antioxidants

Activity and bioaccessibility of antioxidants in yoghurt enriched with black mulberry as affected by fermentation and stage of fruit addition

Pasteurised whole milk was acidified with bacterial culture or glucono-delta-lactone (GDL) to determine effects of fermentation and pH reduction on activity and in vitro bioaccessibility of antioxidants and physical properties of yoghurt with black mulberry. Both pH reduction and fermentation were found to influence activity and bioaccessibility of antioxidants in mulberry yoghurt. Total phenolic content of the sample prepared with bacterial culture was higher than that of the sample with GDL, while there was a similar level of reduction in both samples after three weeks of storage at 4 degrees C. Fermentation with the bacterial culture yielded lower copper reducing activity but higher DPPH scavenging activity compared with acidification with GDL. Bioaccessibility of the antioxidants in in vitro gastrointestinal system was less than 25% in all samples. Addition of fruit after acidification or fermentation of milk, rather than before, resulted in higher antioxidant activity, higher consistency coefficient and less serum separation. (C) 2021 Elsevier Ltd. All rights reserved.WOS:0006349608000052-s2.0-8510132003