**1. Introduction**

Burger is one of the most appreciated meat products worldwide for its ease of preparation and versatility of consumption, which is considered a time-saving strategy in the modern lifestyle [1–3]. Nevertheless, the grinding process for raw meat, resulting in the disruption of muscle structure, leads to a less stable food matrix favoring microbial spoilage as well as chemical and enzymatic oxidation processes with possible repercussions on safety and health [4,5]. Several strategies, such as peculiar production processes, packaging and food additives, have been studied during the last few decades in order to reduce the above-mentioned phenomena and enhance the shelf-life of these meat products [6–10]. Studies in the literature demonstrate that antioxidant molecules protect the grinded meat from oxidation and delay the microbial growth [11]. Consequently, in fresh ground meat preparations, additives with antioxidant properties are usually employed. Although food additives are strictly regulated (Regulation (EC) No. 1333/2008, s.m.i.) [12], chemical compounds intentionally added into food are considered with mistrust by consumers due to their potential long-term adverse effects linked to hypersensitivity, asthma, cancer, skin irritation, allergies and gastrointestinal problems [13,14]. As a consequence, growing

**Citation:** Roila, R.; Sordini, B.; Esposto, S.; Ranucci, D.; Primavilla, S.; Valiani, A.; Taticchi, A.; Branciari, R.; Servili, M. Effect of the Application of a Green Preservative Strategy on Minced Meat Products: Antimicrobial Efficacy of Olive Mill Wastewater Polyphenolic Extract in Improving Beef Burger Shelf-Life. *Foods* **2022**, *11*, 2447. https://doi.org/10.3390/ foods11162447

Academic Editors: Marco Poiana, Francesco Caponio and Antonio Piga

Received: 19 July 2022 Accepted: 11 August 2022 Published: 14 August 2022

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**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

interest has been demonstrated by consumers towards products with natural antioxidants, encouraging food industries to continuously research for the newest natural food additives to replace synthetic ones [15].

Several spices, essential oils, extracts, powders and other plant by-products have been studied in recent decades in order to assess their activity and their effects on meat products as food supplementation [16–19]. Among these, olive oil by-products can be considered a source of bioactive molecules that are potentially applicable for processed meat preservation [20]. It is known that olive oil by-products are characterized by a high number of hydrophilic phenols, mainly secoiridoids, found exclusively in the *Oleaceae* family, that have been proven to inhibit or delay the rate of growth of a wide range of Gram-positive and Gram-negative bacteria as well as to have high antioxidant properties [21,22]. In particular, the olive mill wastewater generated in olive oil production has a high generation rate (49% of total mass), and the possible exploitation of this agro-industrial waste through the recovery of high-value bioactive compounds could positively affect the economic and environmental sustainability of agro-industry [23].

Although the chemical composition and the antioxidant capacity of olive oil byproducts as well as their application in foodstuff have been previously studied by several authors [20,24,25], information on the effect of the olive mill wastewater polyphenolic extract on the microbial population of minced meat products to improve their shelf-life is still limited.

In this sense, the role of this natural extract in the replacement of synthetic preservatives in meat products is postulated. With this aim, the antioxidant activity and antimicrobial capacity of olive mill wastewater polyphenolic extract during beef burger shelf-life was evaluated. In order to estimate the potential activity of this polyphenolic extract in comparison with synthetic additives, different formulations were tested and compared to a control formulation and a control formulation with synthetic preservatives (sodium ascorbate) during a period of 7 days of cold storage.
