Comparative Physicochemical, Microbiological, Antioxidant, and Sensory properties of pre‐ and post‐fermented yoghurt enriched with olive leaf and its extract. Issue 3 (10th January 2022)

• Record Type: Journal Article
• Authors: Pourghorban, Samira; Yadegarian, Linda; Jalili, Maryam; Rashidi, Ladan
• Is Part Of: Food science & nutrition. Volume 10:Issue 3(2022)
• Page Start: 751
• Page End: 762
• Publication Date: 2022-01-10
• Subjects: enriched yoghurt -- fermentation -- olive leaf powder -- sensory evaluation; Food industry and trade -- Periodicals; Food -- Periodicals; Nutrition -- Periodicals; 664
• DOI: 10.1002/fsn3.2704
• Languages: English
• ISSNs: 2048-7177

Abstract

Abstract: This study investigated the comparative effect of yoghurt samples enriched with different concentrations of olive leaf powder (OLP) (0.1, 0.5, 1, and 1.5 mg/ml) and its extract (OLE) (0.5, 1, 3, and 5 mg/ml) on the microbiological, sensory, physicochemical, and antioxidant properties of pre‐ and post‐fermented samples during 21 days of storage. Sensory evaluation showed that concentrations lower than 1.5 and 5 mg/ml of OLP and OLE, respectively, were acceptable. Adding OLP or OLE did not have an influence on yoghurt starter culture bacteria ( p > .05). All enriched samples significantly showed higher acidity and lower pH compared with control samples ( p < .05). The most important polyphenols were oleuropein (from 0.132 to 0.224 and 0.373 to 0.413 mg/g for 0.5 and 3 mg/ml of OLE, from 0.194 to 0.321 mg/g and 0.413 to 1.280 mg/g for 0.5 and 1 mg/ml of OLP, respectively) and catechin (from 0.369 to 0.382 and 0.461 to 0.477 mg/g for 0.5 and 3 mg/ml of OLE, from 0.386 to 0.405 mg/g and 0.310 to 0.710 mg/g for 0.5 and 1 mg/ml of OLP, respectively) in enriched yoghurts. Adding OLP or OLE increased shelf life, antioxidant activity percentage (AA%), and total phenol content (TPC) of enriched samples ( p < .05). During 21 days of storage of all samples, TPC, AA%, and pH decreased and TTA increased. Abstract : In this study, olive leaf and olive leaf extract were used for the enrichment of yogurt. Olive leaf is a rich source of polyphenolic compounds and a healthy raw material. Organoleptic assessment of enriched yogurt samples with different concentrations of olive leaves and olive leaf extract was performed in the National Standard Organization of Iran. The organoleptic assessment of the new functional yogurt samples was performed by a testing panel, including 10 assessors, which evaluated the taste, color, and texture using a 1–5 scale, according to ISO 22935‐1, ‐2, and ‐3 methods. Physicochemical and microbiological tests were performed on novel yogurt formulations according to the method described by ISO 11869 and 7889, respectively. The viability of lactic acid bacteria and the physicochemical and organoleptic assessment of all yogurt samples were evaluated during 21 days of cold storage. Then, antioxidant activity (%AA), total phenol content (TPC), type and amount of polyphenol content of the enriched yogurt were examined during the 21‐day period. In addition, polyphenol compounds were detected and quantified by HPLC.