LPT 321: Meat Science (1+1)

ESTIMATION OF MYOFIBRILLAR FRAGMENTATION INDEX

Principle

• Myofibrillar fragmentation index as the name suggests is an indirect index of the fragmentation (disintegration) of the myofibrillar (cytoskeletal) proteins (proteolysis) that is associated with ageing.
• Hence as ageing advances the myofibrillar fragmentation increases and this increase in myofibrillar fragmentation is perceived as enhancement in tenderness associated with ageing, on sensory evaluation.

Equipment

• Virtis 45” homogenizer
• Glass Flouted Homogenisation Flask
• Virtis Filtration Unit
• Stainless steel screen (250 μm)

Reagents

• 0.25 M sucrose and
• 0.02 M potassium chloride

Procedure

• Epimysial tissue is removed from the sample of meat and frozen.
• The frozen pieces are cut into approximately 7 cm³ and 10 g cubes are weighed into a Virtis glass flouted homogenisation flask containing 50 ml of cold solution of 0.25 M sucrose and 0.02 M potassium chloride.
• The muscle cubes are allowed to thaw in the solution for 5 minutes.
• The sample after thawing, is homogenised in a Virtis 45” homogeniser (with the 2 virtis steel blades aligned and positioned 1 mm below the surface of the solution) for 40 seconds at full speed.
• The homogenate is then filtered through a 250 μm stainless steel screen in the filtration unit.
• The homogenate is stirred to enhance the filtration process.
• The resulting fraction left behind in the stainlees steel screen (muscle fragments greater than 250 μm) is blotted on a Whatman No 3 filter paper and allowed to dry at 25^₀ C for 40 minutes.
• The net fraction weight is determined after the drying step and the myofibrillar fragmentation index is calculated as follows

Myofibrillar fragmentation index = Net fraction weight X 100

Assesment

• As, the myofibrillar fragmentation index is a product of the net fraction weight left behind in the stainlees steel screen, it represents the myofibrillar proteins that has not disintegrated and hence lower the myofibrillar fragmentation index, the greater the tenderness, and the more the process of ageing has progressed.