# Application of Natural Antioxidants from Fruits Waste for Improving Egg Quality Characteristics
## 5 Mechanisms of Antioxidants in Laying Hens
### Mechanisms of Fruits' Waste Antioxidants' Deposition in Eggs  
According to previous studies, egg quality benefits from the presence of antioxidants since these bioactive compounds not only protect cellular structures from oxidative damage but also influence the physiology of the laying hen [80]. These substances, particularly bioactive compounds of plant origin such as fruit waste, become part of hens' metabolism, regulate some physiological processes, and, finally, are transferred to the eggs [81]. After ingestion, the bioactive compounds like phenolics, flavonoids, carotenoids, minerals, and vitamins are absorbed into the birds' digestive systems, influencing the metabolism associated with oxidative stress, immune response, and the absorption of nutrients [82; 91]. Figure 3: Graphical representation of the three phases of mechanisms of antioxidants in laying hens. During peak production periods, laying hens are prone to oxidative stress, which may compromise their health and egg quality [80; 92]. The electron donation provided by the antioxidants to the ROS turns them into a stable state and prevents further cellular harm from the oxidative stress process [93; 94]. For instance, the polyphenonic content in a banana peel may counteract various ROS [95; 96] or the polyphenols from grape and pomegranate waste could result in better health and, possibly, longer hen productivity [97; 98; 99]. Similarly, citrus, grape, pomegranate, apple, and lemon waste can increase the antioxidant ability of the eggs due to a high content of bioactive compounds with antioxidant potential (carotenoids, vitamin, minerals, polyphenols) present in these fruits' waste [100; 101] and, in some cases, can prevent microbial spoilage during storage [102]. The mechanism via which the antioxidants derived from fruit waste improve the eggs' quality is through inhibiting oxidative degradation and microbial increase. The antioxidant compounds found in fruit waste act via neutralizing ROS, mainly in the yolk, which would result in off-flavors, color adjustments, and nutrient loss [103]. By scavenging ROS, these natural compounds reduce oxidative stress, maintaining the egg's freshness for longer durations. This does not only enhance the color of the yolk but also improves the nutritional value of the egg, giving consumers eggs that are enriched in antioxidants and essential nutrients. Vitamin E, from fruit waste like sea buckthorn, is also absorbed into the egg yolk as a highly active lipid soluble antioxidant, as shown by [PERSON] et al. [104], while a high-fat poultry diet results in eggs enriched with bioactive compounds that enhance lipid stability and freshness parameters under different storage times and temperatures [20; 105] due to the presence of a lipophilic, meaning they are absorbed into the lipid components of the egg yolk [106]. Additionally, the phenolic compounds can disrupt microbial cell membranes or interfere with microbial enzyme activity, slowing the increase in spoilage-causing microorganisms (_Salmonella_ and _Escherichia_ coli) [107; 108]. The antioxidants might also chelate iron ions, which are important cofactors for bacterial metabolism, inhibiting microbial proliferation, as shown by [PERSON] et al. [109]. The polyphenols and fiber content from grape waste were already mentioned by numerous studies as beneficial and potent antioxidant compounds that enhance oxidative stability by preventing lipid peroxidation [46; 62; 110] and increasing shelf life during storage [111]. Quercetin from apple waste was reported by [PERSON] et al. [112] to reducing lipid oxidation and prolong egg freshness. Moreover, [PERSON] et al. [113] reported that the pectin in apple pomace further supports gut health and nutrient absorption in chickens, leading to an overall better egg quality. However, apple pomace requires further investigation as the literature data are lacking in studies on laying hens supplemented with this fruit waste. Similarly, pomegranate and mango waste have proven antioxidant potential, as indicated by [PERSON] et al.