## 1 Introduction  
Nowadays, contemporary dietary trends dictate the consumption of foods manufactured for providing health benefits beyond nutritional adequacy. Such consumer demands have been the driving force for the food industry to develop commodities with increased functionality, yet also devoid of additives which could, in the long term, have a questionable impact on the health status [1, 2]. Antioxidants are some of the commonest food additives, destined to protect mainly lipid-containing foods from oxidative deterioration. This problem is of particular concern to fats and oils, where rancidity is manifested by both organoleptic degradation and loss of nutritional value [3]. Lipid oxidation can be brought about through various pathways, and it is a rapid process involving the generation of lipid radicals, which, via chain reactions, may cause severe effects on fatty acid structure and composition with detrimental consequences to their biological properties, but also the generation of toxic compounds [4]. At the same time, the decomposition of certain lipid oxidation products results in the formation of an assortment of volatile substances, which lend lipid-containing foods highly undesirable sensory attributes. Therefore, battling oxidation onset and progression is of paramount significance for producing palatable and safe foods [5]. Antioxidants are regularly added to lipid foods to provide an effective shield against oxidation and rancidity development. A common practice in the food industry is the use of the so-called synthetic antioxidants, which are mainly represented, but not limited to, butylated hydroxyloluence (BHT), butylated hydroxynisole (BHA), and _tert_-butyl hydroquinone (TBHQ). These additives are permitted in a spectrum of foods, such as vegetable oils, animal fats, cured meats, etc., and their levels usually vary from 25 to 200 mg kg\({}^{-1}\)[6]. By virtue of the low price, high carry-over effect, exceptional efficacy, and ease of procurement, this family of compounds has been the tool of preference in the food industry for many years. However, a significant number of recent studies have raised serious concerns on the safety of these additives, concerning their involvement in adverse effects on human health and the environment [6; 7; 8]. On this ground, consumer pressure has shifted food industries to adopt alternative policies for manufacturing lipid-containing foods, by lowering or even eliminating the use of synthetic antioxidants. In this line, the necessity of natural antioxidants equally efficient or even superior to synthetic ones is pressing, and there has been a significant number of studies reporting on the use of natural products as food antioxidants [9; 10; 11]. The most prominent class of compounds that could effectively replace synthetic antioxidants is polyphenols, a category which embraces a bewildering diversity of chemical structures. Polyphenols are notorious for expressing antioxidant activity, and owing to this property, thorough examinations have been carried out on several food matrices [12; 13; 14]. Nevertheless, most of these studies have dealt with plant extracts rather than pure compounds, and this is an important shortcoming in the relevant field. This is because the species and the relevant proportions of various polyphenic substances in a plant extract may vary largely, and therefore the control and appropriate regulation of the antioxidant protection required might be particularly problematic. On the other hand, the isolation of pure compounds may be laborious, time-consuming, and of a high cost, thus hindering their wide applicability [15]. However, innovative technologies implemented on biomass valorization have paved the way to establishing sustainable and cost-effective routes for the recovery of antioxidant polyphenols from industrial side streams.