## 5 Antintutitional Factors and Reduction Strategies  
A range of factors can affect protein digestibility, including the formation of protein conjugates, such as polysaccharides and polyphenols, which can lead to structural modifications that hinder enzymatic hydrolysis, as well as the presence of antinutritional compounds. Antintutitional factors (ANFs), also known as anti-nutrients, are naturally occurring compounds found in plant sources that interfere with the absorption or utilization of nutrients in the body. Antinutritional factors present in plant sources have been shown to impede the process of protein digestion and elevate endogenous nitrogen losses in faeces, resulting in reduced protein digestibility and heightened protein requirements [3]. Numerous studies have shown the negative impact of these compounds on protein digestibility, with some indicating their susceptibility to heat degradation, while others suggest their resistance to heat-induced changes [108; 109]. The critical challenges in the plant protein field encompass the quest for plant sources that exhibit nutritional profiles comparable to animal-based proteins, and the exploration and refinement of innovative food processing methodologies aimed at augmenting the nutritional attributes of conventional plant protein sources [3]. Hence, it is imperative to mitigate or eradicate these substances to enhance the biological utilization of plant proteins, which typically exhibit lower digestibility (75-80%) in comparison to animal proteins (90-95%) such as meat, poultry, eggs, and milk [3]. Furthermore, it should be noted that plant proteins encounter reduced enzyme accessibility due to the presence of rigid cell walls and seed coats [110]. The major ANFs found in consumable crops involve amylase inhibitors, protease inhibitors, phytic acids, tannins, saponins, lectins, gossypol, and goitrogens [111]. These compounds negatively affect the protein and AA digestibility [112; 113] by decreasing bioavailability and disrupting metabolic processes, leading to harmful effects on the gastrointestinal tract's physiology [114; 115; 116; 117]. Among the ANFs, phytate is one of the major compounds present in many cereals, legumes, and oiseeds [118]. phytate is a chelating agent and primarily impacts the bioavailability of micronutrients such as calcium, cooper, zinc, and iron [119]. Thus, high phytate intake can lead to mineral deficiencies over time. Nevertheless, phytochemicals, including phenolic compounds, have demonstrated notable antioxidant activity by effectively scavenging reactive oxygen species (ROS), exhibiting strong reducing power, and displaying metal-chelating capabilities towards ferric and ferrous ions [111]. Although not all polyphenols possess chelating properties, certain phytochemicals, such as isoflav, genistein, and biochanin A, are particularly valued as antioxidants due to their dual attributes as reducing agents and metal ion-chelating agents [120]. Regarding proteins, phytate interferes with protein digestibility by competing for essential mineral cofactors required to activate peptidases. Additionally, phytate directly interacts with the protein, further affecting its digestibility [121]. In addition, protease inhibitors such as trypsin and chymotrypsin are other ANFs found in legumes such as soybeans and kidney beans. These ANFs can impact the globular structure of proteins, hindering digestive enzyme activity in the small intestine [3]. By interfering with the digestion process, protease inhibitors inhibit the enzymes responsible for protein breakdown, potentially resulting in reduced protein digestibility. Haemagglutinins such as lectins are other ANFs that are proteins that bind to carbohydrates. Lectins are found in various plant sources, including legumes, grains, cereals, and certain vegetables, but are mainly present in legumes. Lectins can cause the agglutination of red blood cells by reversibly binding to specific mono-oligosaccharides and oligosaccharides found in glycoproteins and glycolipids [122].