Original article Influence of green, white and black tea addition on the antioxidant activity of probiotic yogurt during refrigerated storage Premalatha Muniandy a , Amal Bakr Shori b, *, Ahmad Salihin Baba a a Biomolecular Research Group, Division of Biochemistry, Institute of Biological Sciences, Faculty of Science,University of Malaya, 50603 Kuala Lumpur, Malaysia b King Abdulaziz University, Faculty of Science, Department of Biological Sciences, Jeddah 21589, Saudi Arabia A R T I C L E I N F O Article history: Received 7 February 2015 Received in revised form 29 December 2015 Accepted 16 February 2016 Available online xxx Chemical compounds studied in this article: Catechin (PubChem CID: 9064) p-Coumaroylquinic acid (PubChem CID: 90478782) Kaempferol-3-rutinoside (PubChem CID: 5318767) Gallic acid (PubChem CID: 370) Quinic acid (PubChem CID: 6508) Epicatechin (PubChem CID: 72276) Epigallocatechin (PubChem CID: 72277) Gallocatechin (PubChem CID: 65084) Chlorogenic acid (PubChem CID: 1794427) Epicatechin gallate (PubChem CID: 107905) Keywords: Yogurt Tea Antioxidant activity Total phenolic content A B S T R A C T The present study investigated the effect of green, white or black tea (Camellia sinensis) on the fermentation of milk and antioxidant potential of yogurt during 21 days of storage at 4  C. All yogurts were analyzed for total phenolic content (TPC), identification of phenolic compounds and antioxidant potential using diphenyl picrylhydrazyl radical scavenging (DPPH), ferric reducing antioxidant power (FRAP) and ferrous ion chelating (FIC) assays. Green tea yogurt showed the highest phenolic content (p < 0.05) followed by white tea yogurt and black tea yogurt. LCMS/MS analysis revealed the absence of several phenolic compounds in tea yogurts, despite their presence in tea water extracts, as well as the presence of new phenolic compounds. All tea yogurts showed higher (p < 0.05) FRAP and FIC values than respective control during 21 days of storage. However, BTY showed the lowest values of DPPH scavenging activity and FRAP during storage period. In addition, the antioxidant activity for all tea yogurts remained almost constant over storage period. In conclusion, green, white and black tea can be successfully employed to improve the antioxidant properties of yogurt and provide sustained antioxidants during storage. ã 2016 Elsevier Ltd. All rights reserved. 1. Introduction Free radicals such as reactive oxygen species (ROS) are continually produced in our body as a by-product of many metabolic processes. Under normal conditions, the body has its own antioxidant defense system comprising of several enzymes such as catalase, superoxide dismutase and glutathione peroxidase to detoxify these free radicals (Scheibmeir et al., 2005). Dietary antioxidants such as vitamins C, E and A also play a crucial role in fighting these free radicals. However, when there is an over- production of these free-radicals leading to an imbalance between the generation and elimination of free radicals in the body, a situation known as oxidative stress occurs. This in turn results in oxidative damage to cellular components and biomolecules, thus marks the onset of many degenerative diseases related to aging such as cardiovascular disease, diabetes, cancer and neurodegen- erative diseases (Aruoma, 1998). Since antioxidants are vital for their role to delay or inhibit oxidation of cellular components, adequate intake of these compounds in the diet will be beneficial to protect against oxidative damages to the cell. However, the use of synthetic antioxidants such as butylatedhydroxytoluene (BHT) and butyla- tedhydroxyanisole (BHA) are still under evaluation in many countries due to their potential health hazard (Wang, Jónsdóttir, & Ólafsdóttir, 2009). In this regards, extracts of many medicinal plants or herbs rich in phenolic compounds are increasingly used either as additive in food or consumed directly as a natural source of antioxidant (Wong, Li, Cheng, & Chen, 2006). * Corresponding author. E-mail address: shori_7506@hotmail.com (A.B. Shori). http://dx.doi.org/10.1016/j.fpsl.2016.02.002 2214-2894/ ã 2016 Elsevier Ltd. All rights reserved. Food Packaging and Shelf Life 8 (2016) 1–8 Contents lists available at ScienceDirect Food Packaging and Shelf Life journal homepage: http://www.else vie r.com/locate /f psl