1. Introduction:
Meat is an important food providing proteins to most people in the world. Global meat consumption is continuously increased, reached 286 million tonnes in 2013 and is expected to rise to 486 million tonnes by 2050 [
1]. The global population is growing and the world population reached 7.5 billion in 2015, which may be expected to reach 10 billion by 2050, with current resources, producing enough meat for the increasing population appears to be a difficult task (
Figure 1) [
2].
Not only animal sources of meat, but also meat quality is a major determinant of consumer satisfaction, which differs country to country depending on culture and heritage [
3]. Although meat quality is a complex concept, ISO (International Organization for Standardization) defined general meat quality, in particular, for beef meat, as the totality of features and the characteristics of a product or service that impact its ability to meet stated or implied requirements [
4]. A number of characteristics, including colour, tenderness, water holding capacity, pH, appearance, smell, and taste, are used to evaluate beef meat quality. Animal species, sex, age, feeding, and pre- and post-slaughter conditions all have an impact on these parameters. Additionally, the definition of beef meat quality varies according to farmers, processors/companies, and customers. High yield was the most essential criterion for farmers' perceptions of meat quality, functional quality seemed significant for processors' perceptions of meat quality, and eating quality or palatability is significant for consumers' perceptions of meat quality [
5].
It is unlikely that existing animal agriculture and meat production techniques will be able to meet the rising demand for meat. An alternative technique is required to replace traditional meat production. Cell-culture meat is a novel concept in meat industries, which can produce edible biomass by
in vitro culture of stem cells harvested from the muscle of live animals [
6]. Compared to conventional meat production, the
in vitro technology ensures public safety, nutritional security, and an ethical manner of producing meat, while using less water and emitting fewer greenhouse gases [
7]. There are still numerous challenges to be solved, including those related to cells (selection, collection, and maintenance), culture techniques for high yield, secure production, and appropriate quality [
8]. Specifically, serum markers of evaluation are used to evaluate the yield and quality of traditional beef meat production. Additionally, the possible use of serum indicators as dietary supplements in culture media for meat production in cell cultures is considered. We aim to update knowledge on serum markers for assessing the quality of beef meat and explore their possible applications to the production of cultured meat.
5. Potential Application of Serum Markers for Culture Meat Production:
Muscle tissue engineering can be applied to produce cultured meat for human consumption it is an alternative to conventional meat. The motive of cultured meat production is animal/serum-free cultured meat development. The serum contains lots of proteins, lipids, enzymes, electrolytes, hormones, and other elements which support cell growth. In-vitro meat might be biologically equivalent to conventional meat but there are still many technical difficulties to solve to produce fresh meat-like cultured meat [
99]. Serum influences the cultured meat color, taste, aroma, etc. Due to a lack of serum or serum-free media utilization for cultured meat production, the end product may lead to quality and quantity differences from conventional meat [
88]. However, cultured meat production media/serum-free media to date have had limited success, suggesting that a better understanding of optimization conditions is needed.
Cultured muscle tissues generally have a pale color due to the deficiency of myoglobin, which is a potential biomarker for meat color, and the amount of myoglobin content in meat may influence the color of meat (dark to pale). Myoglobin contains heme, which has iron in the center of its structure, and its expression is suppressed under ambient oxygen conditions. Several approaches have been suggested to increase the myoglobin content of cultured meat [
100]. The addition of metmyoglobin (oxidized form of myoglobin) to the culture media was shown to increase the cell proliferation capacity and myoglobin content in the cultured cells [
101]. However, myoglobin contents were still much lower compared to traditional meat, and the resulting color was brown because there might be a limit to the number of nutrients, the cells can incorporate in in-vitro conditions, to solve this issue needs to be optimizing the culture conditions and media. Retinol (RBP-4) and vitamin-E supplements, according to prior research, may improve the color of the meat.
The composition of amino acids in meat is important because they determine the quality and taste, cultured meat has fewer amino acids and nucleotide composition and when compared to traditional meat, it gives taste and tenderness differences compared to a normal steak, and it shows a negative effect on consumer acceptance and economy. Cultured meat of beef showed that the aspartic acid and glutamic acid range was lower than the conventional meat, aspartic acid is a potential marker related to the meat taste and palatability. Glutamic acid was most closely related to taste. It is necessary to find a method to increase the ratio of aspartic acid and glutamic acid when culturing satellite cells [
102]. We suggest micro-supplements of amino acids and vitamin D3 may improve the amino acid composition, taste and tenderness of cultured meat.
Nucleotide-related compounds like adenosine-5 monophosphate, inosine-5 monophosphate; inosine, and hypoxanthine were responsible for the umami, mouth feel, and juiciness senses. In the case of cultured meat, inosine-5 mono phosphate content was significantly lower than traditional meat it may cause weaker umami intensity [
103]. It is necessary to find a solution to increase the number of nucleotide derivatives that involve umami, and juiciness in culture meat production. The addition of vitamin E and protein-rich components in the medium may improve the juiciness and umami taste of cultured meat.
Insulin is a potential meat quality marker, deficiency of insulin in culture media, may significantly affect induced pluripotent stem cell (iPSCs) attachment, proliferation, morphology, expression, colony formation, cell cycle profile, and protein phosphorylation. In cultured meat production, the differentiation of pluripotent or adipose-derived stem cells into adipocytes can be stimulated by insulin and insulin growth factors [
104]. The addition of natural substitutes instead of insulin cannot meet such criteria. It is necessary to solve this problem needs to be optimizing the culture media supplement with insulin.
Retinol is the alcohol form of vitamin A, and it is associated with the maintenance of self-renewal and differentiation of embryonic stem cells and pluripotent stem cells. Retinol executes its function via retinoic acid and regulates the function of genes involved in cell proliferation, differentiation, and development [
105,
106]. Retinol executes its function by activating the phosphatidylinositol 3 (PI3) kinase signaling pathway via the insulin-like growth factor 1 (IGF1) receptor [
107]. Retinol deficiency in culture media may lead to associated immune deficiency causing the impaired function of lymphocytes and detrimental to blood cells [
105]. So this information gives a clear idea of retinol deficiency in media may decelerate stem cell proliferation, differentiation, and development and may influence cultured meat production yield and quality.
Cholesterol is an essential component for mammalian cells, it plays a crucial role in cellular functions such as the biosynthesis of bile acids, production of steroid hormones, embryonic development, water salts, electrolyte balance, and cell proliferation [
108]. The serum contains numerous cholesterols and lipids; it will lead to support cell survival, at the same time cholesterol deficient cells suffer from impaired osmatic resistance disrupting the cell membrane, apoptosis, and necrosis [
109]. Serum-free media contains fewer nutrients and growth factors when compared to commercial media, it is necessary to optimize the serum-free media and keep the right amount of cholesterol-like compounds for enhancing cell growth and cultured meat quality.
Paraoxonase-1 (PON1) is a calcium-dependent serum protein, involved in lipid metabolism and plays a key role against oxidative stress. PON1 is an HDL-associated protein that can hydrolyze oxidized LDL-cholesterol, with potential atheroprotective effects [
110]. PON1 shows a positive association with the fatty acid composition of the adipose tissue [
111]. PON1 level was positively associated with meat quality, supplementation of PON1 may increase the fatty acid composition and adipose tissue formation which may enhance the quality of cultured meat.
Leptin is a hormone synthesized and secreted from adipocytes and plays a crucial role in biological functions in cattle. Leptin concentration is positively correlated with meat thickness, marbling score, and intramuscular fat, and is also negatively correlated with cholesterol content [
112,
113,
114]. This indicates supplementation of leptin in meat culture media gives us promising results and improves the meat yield and quality.
Non- esterified fatty acids (NEFA) are involved in the improvement of the intramuscular fat content and fatty acid composition of meat. Cellular lipids and albumin associated lipids are involved in the regulation of stem cell differentiation. NEFA and meat composition are closely related because they influence flavor, texture, and caloric content [
115,
116]. These facts point to NEFA's significant contribution to the development of cultured meat. Blood urea nitrogen (BUN) was positively correlated with total protein, albumin, and NEFA; this indicates that BUN affects the protein content, flavor, and texture of meat. Micro supplementation of Blood Urea Nitrogen (BUN) and also other compounds may enhance cultured meat quality and yield [
60]. In the development of stem cells, serum total protein (TP) in the media, supplies energy to increase the rate of cell division, regeneration, and proliferation. Total protein is necessary for metabolic processes and affects yield grade, yield score and quality of the meat [
117].
Alanine aminotransferase (ALT) was positively connected with AST, NEFA, albumin, and BUN and negatively correlated with leptin, cholesterol, and glucose These connections could affect the color and quality of meat [
58].
The enzyme serum aspartate aminotransferase (AST), which is present in the liver, heart, skeletal muscles, and brain, is widely distributed. It is necessary for cell survival because it promotes cell growth and prevents mitochondrial disintegration by controlling the release of calcium into the cytoplasm. The link between AST and cytoplasmic free calcium, which is robust, is essential for the death of cells. In order to maintain calcium homeostasis during the postmortem period, increased AST activity can prevent the release of apoptotic agents as well as the activation of calcium-mediated enzymes, whereas decreased AST activity may be associated with a rapid apoptotic process. Lower AST activity may lead to a faster pH decrease and generate inferior-quality meat in the post mortem muscles. Higher AST activity showed a slower pH decline and WBS values (Warner-Bratzler shear force), which led to less force being needed to break down the cooked meat [
66,
118]. AST levels can regulate apoptosis, glycolysis and rate of lactate generation. This highlights how crucial AST supplementation in culture media is.
6. Conclusion:
In contrast to conventional meat production, cultured meat production offers a promising answer to future meat shortages, global food security, and the preservation of the environment resources. Despite the fact that it ought to be economical, it is still at the budding stage and has not yet been developed for large-scale production. Additionally, important problems including social, religious, and legal difficulties have an impact on the production of cultured meat. The price of culture media will always be too expensive; hence culture conditions must be optimized. Researchers concentrated on better and more sustainable production inputs, including cell selection, culture conditions, and co-culturing, specialized bioreactors, appropriate scaffolding material, and formulation of serum-free media.
There is currently no optimal medium for cultured meat production, as scientists are concentrating on serum-free media implementations. The type of grown cells determines how the media should be optimized. Promising alternatives to serum media for the development of cultured meat include materials generated from plants and bacteria that have undergone genetic engineering. Beefy-9, AIM-V, Sericin, Ultroser-G and KnockoutTM Serum Replacement (KSR) are the serum-free culture media, yet still concentrating on production and yield concerns due to a media gap during media optimization, some essential elements that are necessary to raise meat grade and quality were lacking. In this study, we discussed significant concerns regarding conventional meat quality and yield, particularly serum markers of evaluation, and we also made some suggestions regarding the potential use of serum markers for the production of cell-cultured meat.
Therefore, to increase the output and quality of the cultured meat, productive research on the optimization of cultured meat production settings is needed. We propose that, adding serum markers to the culture media is a cutting-edge and secure method for increasing the production and quality of cultured meat. Consumer awareness is the only way to combat food phobia, clarify consumers' beliefs and behaviors regarding cultured meat, and provide comprehensive product tracking, tracing, sensory information, and an affordable price. These elements may attract consumers to cultured meat and have an impact on their acceptance of it.