# Current Status and Economic Prospects of Alternative Protein Sources for the Food Industry
## 1 Introduction  
Protein intake is commonly associated with animal-derived foods such as meat, shellfish, fish, dairy products, and eggs. These traditional protein sources cover general nutritional requirements and have been the most produced and consumed throughout history ([PERSON], 2020) [1]. However, there is an increasing social awareness about food production, adequate nutrition, and environmental sustainability. The greenhouse gases (GHG) emissions associated to agriculture, forestry and other land uses have doubled in the last 50 years ([PERSON] et al., 2022; [PERSON] et al., 2023) [2, 3], but the current resource-intensive food production model still does not provide adequate nutrition to around 3.37 billion people ([PERSON] et al., 2023; [PERSON] et al., 2019; UN, 2023a) [4, 5, 6]. In addition, solid evidence has shown that high intake of animal protein is associated with higher risk of cardiovascular disease, diabetes, and mortality ([PERSON] & [PERSON], 2019) [7]. Moreover, ethical concerns towards animal production could also stifle demand in the Western world ([PERSON] et al., 2020) [8]. Pressing issues about the sustainability of food production are expressed in the United Nations Sustainable Development Goals (UN SDG), which highlights concerns related to food security, clean water supply, responsible consumption, and production, among others (UN, 2023b) [9].  
This scenario stimulates consumer interest for alternative protein (AP) sources as a way of providing sustainable, affordable, and nutritional options to replace or partially substitute for current mainstream food products ([PERSON] et al., 2023; [PERSON] et al., 2019;Grossmann & Weiss, 2021) [4; 10; 11]. Also, a significant portion of the population is now more inclined to adopt vegetarian, flexitarian and vegan diets ([PERSON] et al., 2022) [12]. As a result, this shift in consumer demand is the biggest traction in the market now. The current AP market, estimated to be around USD 2.2 bn, is expected to continue growing to reach a market size of more than USD 150 bn by 2030 (Figure 1). The steep sales growth tendency of meat-free products and on market value of plant-based food companies point to a consumer market that is willing to cross the bridge from traditional animal-protein oriented diets into AP-rich diets ([PERSON] et al., 2024) [13].  
Although opportunities for AP sources such as plants, insects and other novel protein sources have skyrocketted in both developing and advanced markets ([PERSON] et al., 2019; [PERSON] et al., 2021) [10; 15], studies have demonstrated the resistance of a significant share of the population to AP sources ([PERSON] et al., 2023) [16]. Food neophobia (the unwillingness to try new foods), and the sense of prejudiced disgust towards specific alternative protein sectors, such as insect-based and cultured proteins, have been identified as the two main factors hindering market growth ([PERSON], 2023; [PERSON], 2022) [17; 18]. Undesirable organoleptic attributes such as off-flavors and unpleasant texture, have also been raised as obstacles for the larger acceptance of AP ([PERSON] & [PERSON], 2023; [PERSON] & [PERSON], 2019) [19; 20]. In this sense, the market interest has driven research and development towards overcoming these challenges and warranting wide access and acceptability of AP.  
Therefore, this short review brings an overview of the fundamental aspects about the composition and applications of promising AP sources (plants, algae, insects, fungi and cultured), as well as the economic potential and perspectives of this emerging protein market. It also identifies key aspects of currently available technologies and foreseeable challenges in the future of alternative proteins.