Development and in vitro digestion analysis of kefir fortified with by-product extracts: Prediction of total antioxidant and phenolic compounds bioavailability
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Unit of Human Nutrition, Department of Food Science and Nutrition, School of the Environment, University of the Aegean, Myrina, Greece
Panagiota Potsaki
Unit of Human Nutrition, Department of Food Science and Nutrition, School of the Environment, University of the Aegean, GR-81400, Lemnos, Myrina, Greece
Publication date: 2022-05-27
Public Health Toxicol 2022;2(Supplement 1):A101
Moving forward to a sustainable nutrition and as studies have shown that food byproducts are a source of bioactive compounds, they could be used for the production of novel functional foods.

Our study aims to
  1. determine total antioxidant and phenolic content and predict their bioavailability (BAvI%) in byproduct extracts from bitter orange, lemon and rosehip and
  2. develop a kefir product fortified with byproduct extracts.

  3. Methods:
    Samples (peels and seeds) were collected and dried in air oven. Water extracts were obtained from 10 g of each sample into 100 mL of distilled water in ultrasonic bath, followed by filtration. The extracts were analyzed with in vitro digestion method and total antioxidants and phenolics were determined with FRAP assay (expressed as mmol of Fe2+/L), and Folin-Ciocalteu assay (expressed as gallic acid (GAE)/ g of dried sample), respectively. Extracts were finally added to kefir and the above bioactive compounds were determined in the new product.

    Antioxidant and phenolic content of bitter orange peel and rosehip seeds (BoR) was 21.87 ± 1.41 Fe2+/L and 67.07 ± 1.67 GAEs/g while for bitter orange and lemon peels (BoL) was 12.11 ± 0.41 Fe2+/L and 47.92 ± 2.10 GAE/g, respectively. After digestion total antioxidants were 3.70 ± 0.50 Fe2+/L for BoR (18% BAvI) and 3.85 ± 0.35 Fe2+/L for BoL (32% BAvI) while phenolic content was 5.95 ± 2.69 GAE/g (10% BAvI) and 7.42 ± 2.75 GAE/g (15% BAvI), respectively. Antioxidant content of kefir fortified with BoR was 0.37 ± 0.15 Fe2+/L and with BoL 0.35 ± 0.12 Fe2+/L while their phenolic content was 3.33 ± 1.72 GAE/g and 1.49 ± 0.75 GAE/g, respectively.

    BoR presented high bioavailability of total phenolics, therefore can be used for the fortification of kefir products in a concentration up to 27% w/w.

Dimou C, Karantonis HC, Skalkos D, Koutelidakis AE. Valorization of Fruits by-products to Unconventional Sources of Additives, Oil, Biomolecules and Innovative Functional Foods. Curr Pharm Biotechnol. 2019;20(10):776-786. doi:10.2174/1389201020666190405181537