Abstract
ABSTRACT The objective of this study was to determine the antioxidant and quality characteristics of yogurt containing olive leaf hot water extract (CON: 0, OLY1: 0.1, OLY2: 0.2, and OLY4: 0.4% (w/v)) stored at 4°С for 15 days. After storage, the lactic acid bacteria count showed no significant difference between yogurt samples either in the presence or absence of olive leaf extract (p > 0.05). The total phenolic content, DPPH radical scavenging activity, and reducing power increased upon increasing the content of the olive leaf hot water extract. Oleuropein was found to be the most abundant phenolic compounds present in olive leaf, and the oleuropein content in OLY4, as measured by HPLC, decreased gradually to 1.09, 1.00, and 0.96 g/L upon increasing the storage time; however, this reduction was not significant (p > 0.05). In sensory evaluations, OLY1 gave the highest score among the experimental groups. The results of this study thereby demonstrate that olive leaf hot water extract can be used to improve the antioxidant capacity and sensory characteristics of yogurt.
Highlights
Olive trees grow mainly in the Mediterranean countries
The fat, protein, lactose, and total solid contents of yogurt samples ranged from 2.53% to 2.83%, 3.40% to 4.03%, 8.40% to 8.83%, and 12.50% to 12.91%, respectively
We found that lactic acid bacteria imparted no significant influence on any experimental group, and a significant reduction was observed for the containing olive leaf hot water extract (CON) group alone after 7 days of storage (p > 0.05)
Summary
Olive trees grow mainly in the Mediterranean countries. Olive fruit, along with its oil and olive leaf, has a rich history as a nutrient, and is known to have medicinal properties (Soni, Burdock, Christian, Bitler, & Crea, 2006). Olive leaves contain bioactive compounds that have antioxidant, antihypertensive, anti-inflammatory, hypoglycemic, and hypocholesterolemic properties (El & Karakaya, 2009). Regular intake of yogurt containing a probiotic strain of lactic acid bacteria can enable control of blood cholesterol levels, can alleviate lactose intolerance, and has anti-cancer effects (Corgneau et al, 2017; Kim et al, 2009; Sah, Vasiljevic, McKechnie, & Donkor, 2016). It is well known for preventing enteropathy and for reducing diarrhea (Vasiljevic & Shah, 2007). It is well known for preventing enteropathy and for reducing diarrhea (Vasiljevic & Shah, 2007). Farvin, Baron, Nielsen, and Jacobsen (2010) reported that the high oxidative stability of yogurt is due to the antioxidant peptides released during milk fermentation by lactic acid bacteria
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