## 1 Introduction  
Oxidation is a major problem that reduces the gallantry life of fresh, frozen, chilled, or processed meat and meat products. Antioxidants are used to stabilize free radicals by delaying the oxidation of lipids and proteins and the late development of unpleasant odours, as well as to improve colour stability [1]. Due to the potentially toxic effects of synthetic antioxidants, the demand for natural antioxidants has increased in recent years [2]. Regarding toxicity, studies have shown that these substances can have adverse health effects when not used within the established safety limits [3]. Sodium nitrite and nitrate are some of the most widely used in the meat industry as curing salts. Regardless, an excess of these ingested substances can interact with amines and amides, giving rise to N-nitroso compounds such as nitrosamines with mutagenic, teratogenic, and carcinogenic potential [4]. Given the negative health effects of synthetic antioxidants, consumers are now opting for healthier meat products containing natural antioxidants. Recently, researchers have focused on identifying new antioxidants from plants, fruits, and vegetables due to their high content of phenolic components and offering an alternative to the conventional antioxidants currently used [5]. These natural antioxidants contain certain active compounds that exert antioxidant potential in meat and meat products through different mechanisms of action. The efficient extraction of these antioxidants from natural sources, together with the establishment of their activity in vitro and antioxidant products, has been a great challenge for researchers involved in this field [6]. Peppers (_Capsicum annuum_) as vegetables are botanically classified in the family Solanaceae, genus Capsicum [7]. The production of bell peppers has increased considerably in recent years. In 2019, the production was 35.98 million kg/year, and in 2020, it increased to 36.09 million kg/year; however, the annual losses of this crop are estimated at 40% [8]. The bell pepper is a vegetable with a high nutritional value. After processing, it generates significant quantities of by-products (5-30%) (peel, seeds, leaves, stems, seeds and unused pulp) rich in phytochemical compounds. The by-products resulting from the processing of peppers contain significant amounts of bioactive compounds (phenols, flavonoids, carotenoids, tocopherol, and pectin polysaccharides) which exhibit antioxidant, antibacterial, antifungal, immunosuppressive, and immunostaining properties and antidiabetic, antitumor, and neuroprotective activities, and they have potential use as functional food additives. In this context, the valorisation of by-products is an area of great interest in technology and innovation, with beneficial effects for the population, economy, and environment [9; 10], contributing to low-waste technology in agribusiness and providing economic benefits to producers [11]. Due to their content in bioactive compounds, special attention is needed in characterising and exploiting these multi-purpose plant products, which are currently under-studied. Thus, this work aims to develop a new type of nitrite-free meat products with increased functionality by introducing yellow and red bell pepper processing by-products into the manufacturing recipe as a substitute for the synthetic antioxidant (sodium nitrite). In a previous study [12], we assessed the antioxidant potential of a tomato processing by-product and its effectiveness in providing protection against lipid oxidation in nitrite-free sausage formulas. Encouraging results in this respect have led us to extend our research to other types of plant-based powders obtained from vegetable processing by-products.