Effects of phenols extracted from olive vegetation water on oxysterols, mutagenicity and genotoxicity of cooked beef hamburgers

By-products of the olive oil mechanical extraction process are sources of high value molecules for the production of new foods and/or ingredients with higher functionality. In particular, replacing chemical additives (i.e. nitrite/nitrate salts) in meat preparations with natural compounds from agro-food by-products (such as biophenols) is of great interest to both food industry and consumers, because it increases the sustainability of the food chain while promoting at the same time the launching of clean label meat products. Due to its high concentration in secoiridoids’ derivatives and verbascoside, the addition of a phenolic extract from olive vegetation water in fresh meat products, is expected to exert an antioxidant action towards lipids and myoglobin, as well as an antimicrobial activity especially versus those Gram-positive bacteria having a significant impact on food safety, such as Listeria monocytogenes and Clostridium botulinum. The aim of this study was to evaluate the effect of an extract rich in phenols obtained from olive vegetation water on the oxidative stability of cooked beef hamburgers prepared without chemical additives during storage, as well as on their mutagenicity and genotoxicity. To prepare the hamburgers, minced beef meat was added with 0.8% salt, 2 starter cultures (SafePro® and Bactoferm®) and different concentrations of phenolic extract: control (C), L1 (0.35% of spray-dried phenolic extract, equivalent to 87.5 mg of phenols/Kg), L2 (0.70% of spray-dried phenolic extract, equivalent to 175 mg of phenols/Kg). Raw hamburgers were packed under modified atmosphere and stored under alternating exposure to fluorescent light (12 h dark/12 h light) at 4±2 °C for 9 days. Hamburgers were sampled at different times (0, 6 and 9 days) and grilled at 70 °C. The oxidative stability of the cooked hamburgers was evaluated by thiobarbituric acid reactive species (TBARs) and oxysterols. To assess the in vitro DNA damage and mutagenicity, the Comet assay and the Ames test were performed on the extract of cooked hamburgers, respectively. The results show that the phenolic extract at both concentrations proved to effectively reduce TBARs and oxysterols during shelf-life. Remarkably, TBARs and oxysterols were up to 5.7- and 4-fold lower in phenol-enriched cooked hamburgers, respectively, as compared to the control samples. Moreover, the extract of cooked hamburgers proved to be genotoxic on PBMCs (Primary Peripheral Blood Mononuclear Cells) humans’ cells, while they were not mutagenic. Nevertheless, the genotoxicity was reduced by presence of the phenolic extract. In conclusion, the phenolic extract from olive oil wastewater proved to be an effective antioxidant and to reduce the production of genotoxic compounds (responsible for carcinogenicity of red meats, according to IARC), thus confirming to be a promising ingredient for clean label fresh meat products.