Foodchem Lecture 13 Pics

Overview of muscle structure

Muscles are made up of muscle fiber bundles held together by connective tissue (collagen) and anchored by tendons (collagen)

Muscles are made up of muscle fiber bundles held together by connective tissue (collagen) and anchored by tendons (collagen)

• Muscle bundle
• Each fiber bundle contains many long muscle cells (called muscle fibers) which can be seen by the naked eye)

• Muscle bundle
• Each fiber bundle contains many long muscle cells (called muscle fibers) which can be seen by the naked eye)

Myofibrils within the cell are composed of overlapping myofilaments which result in regions of dark and light striations (sarcomeres) when viewed under plane polarized light

Myofibrils within the cell are composed of overlapping myofilaments which result in regions of dark and light striations (sarcomeres) when viewed under plane polarized light

• Left = myosin myofilament (thick)
• Right = actin myofilament (thin)

Myofilament is made up of two groupings of contractile proteins - actin and myosin

• Looking at the myofilament in cross section
• Central stem is the myosin bundle with radially distributed rods of actin

• Close up of the myofibrillar proteins
• Responsible for muscle contraction
• Contraction mechanism involves actin, myosin, and ATP/ADP (energy)

The central myosin bundle consists of about 400 individual myosin molecules arranged in a staggered fashion as pictured

Each myosin unit is a double alpha helix terminating in a globular head having ATPase activity

Actin is really a double helix of 'F' actin or 'fibrous actin', which is a polymerized form of 'G' or globular actin

• Contraction/relaxation
• Reversible reaction: G acton <-- / --> F actin

• Close up of a relaxed sarcomere and it contracted
• In the presence of ATP - G actin instantly polymerizes into F actin, causing a shortening or contraction in the muscle fiber

• Overall complexity of a muscle fiber
• Contains even more other proteins present in meat tissue systems

• Actomyosin complex
• F-actin (red), tropomyosin (blue), myosin (yellow)

• Collagen close up
• Connective tissue is mainly made up of collagen - found as part of the tendons, within the muscle and a major component of hide and bones (key sources)
• Has many commercial uses (like for making gelatin)

• The fundamental collagen unit is a triple suprahelix, called tropocollagen
• Made up of three proteins (two similar protein chains and one different held in place by hydrogen bonding)

• Overview of tropocollagen in tissues
• Associates in a staggered fashion in 3 dimensions to form a sheet like material which surrounds the muscle bundles as well as being an integral part of tendons and the matrix in bone tissue

• Gelatin desserts
• Connective proteins have value as gelatin, a useful functional protein in food and medicine
• Gelatin production is somewhat of an art, and there are numerous processes used, depending on the raw material source

• Gelatin desserts
• Connective proteins have value as gelatin, a useful functional protein in food and medicine
• Gelatin production is somewhat of an art, and there are numerous processes used, depending on the raw material source

• Gelatin capsules
• Connective proteins have value as gelatin, a useful functional protein in food and medicine
• Gelatin production is somewhat of an art, and there are numerous processes used, depending on the raw material source

• Gelatin powder
• Made by: Discards of hide, bones and meat placed in water and heated in a retort under pressure
• Around 80°C the collagen matric begins to disintegrate and solubiliz due to the breaking of intermolecular hydrogen bonds
• Fat is skimmed, final clarified product is a viscous solution which will gel if allowed to cool
• This is drum dried and ground to form gelatin powder
• Gel formation: Powder can be re-solubilized in hot water and will form a gel at low concentrations upon cooling
• Gelatin is hydrated in the presence of water and high temperatures

• Fish proteins are similar to mammalian meat proteins but fish muscle structure is organized quite differently due to its peculiar method of locomotion associated with fish
• Also has much less connective tissue (require less support in natural environment)

• Organization of fish muscle
• Fish proteins are similar to mammalian meat proteins but fish muscle structure is organized quite differently due to its peculiar method of locomotion associated with fish
• Also has much less connective tissue (require less support in natural environment)

• Surimi
• Fish muscle protein from under-utilized species is being used extensively in the manufacture of "surimi"
• Made by: Tissue is first ground and washed with water to remove the water soluble sarcoplasmic proteins while retaining the contractile myofibrillar proteins (actin/myosin)
• Residual actin/myosin protein paste is then stabilized with a cryogenic stabilizer (commonly a sugar alcohol)
• Products then formed into crab and scallop analogs to resemble an identifiable product (appropriate flavor is added)

• Surimi - made into meat analog
• Fish muscle protein from under-utilized species is being used extensively in the manufacture of "surimi"
• Made by: Tissue is first ground and washed with water to remove the water soluble sarcoplasmic proteins while retaining the contractile myofibrillar proteins (actin/myosin)
• Residual actin/myosin protein paste is then stabilized with a cryogenic stabilizer (commonly a sugar alcohol)
• Products then formed into crab and scallop analogs to resemble an identifiable product (appropriate flavor is added)