# Current Status and Economic Prospects of Alternative Protein Sources for the Food Industry
## 2 Alternative Protein Sources
### Cultured (Cell-Based) Protein  
Cultured protein, also known as cell-based, in vitro or lab-grown protein, refers to protein products obtained from the cultivation of mammalian cells under controlled conditions ([PERSON] & [PERSON], 2019)[20]. Developed by the biopharmaceutical industry and usually implemented for monoclonal antibodies and vaccine production, the technology for mammalian cell cultivation has secured significant investments both from industry and academia, aiming to a rapid technological advance on protein production. However, this protein segment is still in its infancy, as the first patents and technical reports addressed this subject around the year 2000. In 2013, the first cultured beef was tasted in London ([PERSON], 2021)[71]. Significant improvements in product quality and affordability have occurred along the last decade, from around USD 1.2 million per pound, in 2013, to around USD 50 per pound, in 2021 ([PERSON] & [PERSON], 2020; [PERSON], 2020)[72; 73]. The process of producing cultured protein can be divided into four main steps: (1) The mammalian stem cells are harvested from an animal via biopsy, followed by mechanical and enzymatic digestion for isolation; (2) The cells are proliferated in a culture medium to increase the number/concentration of viable cells; (3) The cells are differentiated into skeletal muscle cells and fibers; (4) The cells can be assembled in scaffolding materials to deliver a final meat product ([PERSON], 2014)[74]. Two main types of stem cells are considered suitable for protein production: skeletal muscle cells, also known as satellite cells, and embryonic stem cells ([PERSON] et al., 2018; [PERSON] et al., 2020)[75; 76]. When satellite cells are used, the final product is composed only of skeletal muscle fibers and do not resemble the complexity of animal-based protein, which includes other components such as fat and connective tissue, leading to a decrease in consumer appeal and overall quality (Bryant & Barnett, 2020; Bryant & Sanctorum, 2021)[77; 78]. A highly complex meat structure can be achieved with embryonic stem cells, which are able to be further differentiated into different tissues including intramuscular fat and connective tissues, via adipogenesis and fibrogenesis, respectively, and microvascular network, via vascularization ([PERSON] & [PERSON], 2019)[79]. Considering that they come from mammalian cells, cultured protein is expected to deliver the same structure, taste, texture, and functionality of animal-based protein ([PERSON], 2020; [PERSON] & [PERSON], 2019; [PERSON] et al., 2021)[20; 72; 80]. Studies have shown that cultured protein digestibility scores high in the PDCAAS test (around92%), with an amino acid balance comparable to beef. However, there is little information on the presence and bioavailability of minerals, such as iron, zinc and selenium, and vitamins, such as A, B12, D and E, commonly found in animal-sourced proteins ([PERSON] & [PERSON], 2010) [81]. Consumer acceptance of cultured protein is still hampered by taste and texture, which are still far from being considered optimal, when directly compared to them by consumers ([PERSON] & [PERSON], 2021) [78]. The food industry has targeted committed products such as burgers, minced beef and nuggets, for example, in order to overcome texture issues ([PERSON] & [PERSON], 2019; [PERSON] et al., 2021) [20; 80]. Furthermore, consumer preference studies have shown that the perception of \"unnatural\" production, coupled with concerns with food safety and proper production regulations, can generally lead to a sense of disgust and neophobia that increases consumer resistance to cultured meat proteins (Bryant & Barnett, 2020) [77]. Scalability and environmental performance remain the biggest challenges in the implementation of cultured protein ([PERSON], 2020) [73]. Because it involves unprecedented and yet to be established techniques, there is a lack of previous operational data and economically efficient cultivation protocols on a larger scale.