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Fish muscle, which makes up 15-25% of the total protein in fish, is a desirable and nutritious protein source for humans. The edible part of a fish, the fillet, consists of several muscles (myomeres) that are fitted together and separated by thin connective tissue membranes called myosepta. The muscle mass of fish used for food represents 35-60% of their body weight. Fish usually have a combination of different types of muscles, each with different physiological roles. The difference in colour depends on the amount of myoglobin, an oxygen-carrying protein in the muscle, as well as the type of food the fish consumes.
| Characteristics | Values |
|---|---|
| Composition | 15%–25% of total protein in fish |
| Types of muscles | Red and white muscles |
| Muscle structure | Two bundles of large lateral muscles that run on both sides of the backbone |
| Muscle blocks | Myotomes |
| Muscle fiber length | Less than 20 mm |
| Muscle fiber diameter | 0.02–1 mm |
| Number of myofibrils in each muscle fiber | 1000–2000 |
| Myofibril diameter | 1–2 µm |
| Myofibril composition | Actin (thin filament) and myosin (thick filament) |
| Connective tissues | Sheets of collagen |
| Connective tissue in skeletal muscle | Endomysium, perimysium, and epimysium |
| Connective tissue sheaths | Myosepta |
| Muscle movement | Contraction |
| Muscle mass | 35% to 60% of body weight |
| Muscle fibers | 90% of skeletal muscle |
| Tenderness | Firm, cohesive flesh with good water-holding capacity |
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What You'll Learn
- Fish muscle makes up 15-25% of total protein in fish
- Fish muscle is divided into myofibrillar, sarcoplasmic, and stromal proteins
- Fish have a combination of different types of muscles, each with different physiological roles
- The edible part of fish, the fillets, consists of several muscles (myomeres)
- Fish muscle protein hydrolysates are desirable functional ingredients for human food
Fish muscle makes up 15-25% of total protein in fish
Fish muscle constitutes 15-25% of the total protein in fish. Fish are a primary source of protein and other nutrients, and they come in a diverse array of shapes, sizes, and muscular systems. Fish muscle is a desirable protein source as it is easily digestible and rich in essential amino acids. The hydrolysate from fish muscle contains physiologically active amino acids and various essential nutrients, which has led to its high demand as a functional food.
The proportion of red to white muscle in fish varies depending on the activity level and speed required for swimming. White muscle has thicker fibres and fewer capillaries, resulting in reduced blood flow and oxygen availability. In contrast, red muscle is rich in mitochondria, well-supplied with capillaries, and has a higher content of myoglobin, making it suitable for slow and continuous swimming.
Fish muscle can be divided into myofibrillar (50-60%), sarcoplasmic (30%), and stromal (10-20%) proteins. The consumption of fish muscle protein is associated with health benefits, including anti-inflammatory, antioxidant, and angiotensin-converting enzyme inhibitory activities, as well as antimicrobial effects. Clinical studies have also suggested that fish consumption may reduce the risk of cardiovascular diseases and major depressive disorder in elderly persons.
Fish are a good source of complete protein and can be incorporated into meals or snacks. Examples of fish with high protein content include salmon, with 22.5 grams of protein in a 3-ounce cooked serving, and tilapia, with 22.8 grams of protein in an 87-gram cooked fillet.
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Fish muscle is divided into myofibrillar, sarcoplasmic, and stromal proteins
Fish muscle is an important source of protein for humans worldwide, constituting up to 16% of the animal protein consumed by the global population. The muscle proteins in fish are categorised into three types: water-soluble sarcoplasmic proteins, salt-soluble myofibrillar proteins, and insoluble stroma proteins. These proteins make up approximately 20-50%, 50-70%, and 3% of the total muscle protein, respectively.
Sarcoplasmic proteins are responsible for various physiological functions in the fish's body. They include glycolytic enzymes, creatine kinase, myoglobin, and parvalbumin. Myoglobin, an oxygen-carrying protein, contributes to the red colour of some fish muscles, along with the type of food the fish consumes. The sarcoplasmic protein content remains relatively stable, even with changes in physiological functions.
Myofibrillar proteins, on the other hand, are composed of subunits called sarcomeres, which are made up of contractile proteins actin (thin filament) and myosin (thick filament). These proteins play a crucial role in muscle contraction and movement. The myosin heavy chain is a significant component within the myofibrillar protein structure.
Stroma proteins, constituting a smaller proportion of the total muscle protein, are primarily composed of extracellular matrix proteins such as collagen. Collagen is essential for the textural properties of fish muscle, influencing its firmness and overall texture.
The composition and structure of fish muscle proteins can vary depending on the species and environmental factors. For example, elasmobranchs (sharks and rays) and lungfish have higher concentrations of urea in their muscle tissues, which helps in osmoregulation. Additionally, deep-sea species may accumulate trimethylamine oxide (TMAO) to counteract the effects of urea and protect proteins from denaturation caused by high hydraulic pressure.
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Fish have a combination of different types of muscles, each with different physiological roles
Fish have a combination of different types of muscles, each with varying physiological roles. The edible part of a fish, the fillet, consists of several muscles (myomeres) that fit together like a jigsaw puzzle. These muscles are separated by thin connective tissue sheaths called myosepta, which are just a few millimetres thick. Myosepta play a crucial role in transmitting the contraction forces of the individual myomeres to the surrounding myomeres, the skeleton, and the skin. This unique structure gives fish meat its soft, flaky texture.
The fillet consists of two bundles of large lateral muscles that run along both sides of the backbone. A thin connective tissue membrane called myocommata divides the fish muscle into muscle blocks known as myotomes. Each myotome is made up of muscle fibres generally shorter than 20 mm in length and 0.02–1 mm in diameter. These muscle fibres contain thousands of myofibrils, which are composed of contractile proteins called sarcomeres.
The colour of fish meat depends on the amount of myoglobin, an oxygen-carrying protein in the muscle, and the type of food the fish consumes. Red muscle, rich in mitochondria and myoglobin, has a higher oxygen availability due to its well-supplied capillaries. It is typically found directly under the skin along the side of the body and near the spine in active fish species. Red muscle is ideal for slow and sustained swimming, making it prevalent in persistent-swimming fish like herring or mackerel, constituting nearly 48% of their body weight.
On the other hand, white muscle has thicker fibres and fewer capillaries, resulting in reduced blood flow and oxygen availability. These muscles contract rapidly and are suitable for quick movements, such as escaping predators or catching prey. White muscle is more common in slow-moving or bottom-feeding freshwater fish. The proportion of red to white muscles in fish varies depending on their activity levels and the speed required for swimming.
Fish muscle is a valuable source of protein, contributing 15%–25% of the total protein content in fish. It also contains physiologically active amino acids and essential nutrients, making it a desirable component of human food.
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The edible part of fish, the fillets, consists of several muscles (myomeres)
Fish muscle constitutes 15%–25% of the total protein in fish, making it a desirable and nutritious protein source for humans. Fish are one of the primary sources of protein and other nutrients, providing almost 16% of the animal protein consumed globally. The edible part of fish, the fillets, consists of several muscles (myomeres) that are fitted together and separated by thin connective tissue sheaths called myosepta. Myomeres are bundles of muscle fibres that are relatively short and insert into septa of connective tissue, known as myocommata, between adjacent myomeres. This unique structure of muscle and connective tissue gives fish meat its soft, flaky texture.
Each myomere is made up of muscle fibres generally less than 20 mm long and 0.02–1 mm in diameter. Each muscle fibre contains 1000–2000 myofibrils, which consist of small subunits called sarcomeres. Sarcomeres are composed of the main contractile proteins actin (thin filament) and myosin (thick filament). The connective tissue in skeletal muscle includes the endomysium, perimysium, and epimysium, which surround each muscle fibre, bundles of muscle fibres, and the muscle as a whole, respectively. When a meat piece consists of a single muscle, the epimysium is removed.
The skeletal muscles attached to the backbone facilitate voluntary movements and posture in fish. They exhibit a wide range of shapes, sizes, locations, and functions. Skeletal muscles also contain connective, adipose, vascular, and nervous tissues, with muscle fibres, intramuscular connective tissue, and intramuscular fat influencing the quality of meat and fish flesh. The collagen content in intramuscular connective tissues directly affects the textural properties of fish muscle, such as firmness.
Fish typically have a combination of different muscle types, including red and white muscles, each with distinct physiological roles. The colour variation depends on the amount of myoglobin, an oxygen-carrying protein, and the fish's diet. Red muscles, rich in mitochondria and capillaries, have higher myoglobin content and greater oxygen availability, making them suitable for slow and continuous swimming. They are commonly found in active fish species, such as herring or mackerel, comprising nearly 48% of their body weight.
On the other hand, white muscles have thicker fibres, fewer capillaries, and reduced oxygen availability due to less blood flow. These muscles contract rapidly and are suitable for quick movements, such as escaping predators or catching prey. They are prevalent in slow-moving or bottom-feeding freshwater fish. The ratio of red to white muscles varies depending on the fish's activity level and swimming speed.
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Fish muscle protein hydrolysates are desirable functional ingredients for human food
Fish muscle accounts for 15%–25% of the total protein in fish and is a desirable protein source for humans. Fish muscle protein hydrolysates (FPHs) are in high demand as functional foods due to their essential amino acids and various nutrients. The hydrolysate's composition depends on the source of protein, protease, hydrolysis method, hydrolysis conditions, and degree of hydrolysis. The molecular weight, length, and sequence of the peptides, and their amino acid composition influence their bioactive properties.
FPHs have a variety of applications in food systems, including as a potential ingredient in human nutrition. They are used to fortify existing foods, such as mayonnaise and yogurt, and are also used in dietary supplements and capsules with various health benefits. The market for FPHs is expected to grow due to their rapid absorption, ability to increase muscle mass, and disease prevention.
The amino acid composition of food proteins plays an important role in human physiological activities and directly or indirectly affects human health. Fish muscle proteins are rich in essential amino acids such as lysine, tryptophan, histidine, phenylalanine, leucine, isoleucine, threonine, and methionine–cystine. These amino acids have various functional and bioactive properties that support human biological functions.
The production of FPHs involves the use of enzyme technologies for protein recovery and modification, and the development of a broad spectrum of food ingredients and industrial products. The conditions applied during hydrolysis, such as enzyme type, duration, pH, and temperature, significantly influence the final colour of the FPHs, which is important for consumer acceptance. Overall, FPHs are desirable functional ingredients for human food due to their nutritional benefits, bioactive properties, and potential health improvements.
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Frequently asked questions
Fish muscle is made up of myofibrillar (50-60%), sarcoplasmic (30%), and stromal (10-20%) proteins. The muscle fibres are divided by connective tissue, known as myosepta, which are a few millimetres thick.
Fish muscle is a good source of protein, providing 15-25% of the total protein in fish. It also contains amino acids and other essential nutrients. Fish consumption has been linked to a reduced risk of cardiovascular disease and depression.
Fish muscle has a softer, flakier texture due to its thin connective tissue sheaths. Fish muscle also has a higher water-holding capacity compared to mammal muscle.
Red muscle lies under the skin along the side of the body and is rich in mitochondria and myoglobin, providing greater oxygen availability. White muscle has thicker fibres and fewer capillaries, resulting in reduced oxygen availability. The proportion of red to white muscle varies depending on the activity level and swimming speed of the fish.
The quality of fish flesh is influenced by the muscle fibres, intramuscular connective tissue, and intramuscular fat. Fish with firm, cohesive flesh and good water-holding capacity are considered to be of better quality.
