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Från Harlod McGees "På mat och matlagning: Kökens vetenskap och lore":
The muscles that make up meat are mainly water and the protein fibers
that do the work of contraction, which are not dispersable in water.
The soluble and dispersable materials in muscle include about 1% by
weight of collagen, 5% other cell proteins, 2% amino acids and other
savory molecules, 1% sugars and other carbohydates, and 1% minerals,
mainly phosphorus and potassium. Bones are around 20% collagen, pig
skin around 30%, and cartilaginous veal knuckles up to 40%. Bones and
skin are thus much better sources of gelatin and thickening power than
meat. However, they carry only a small fraction of the other soluble
molecules that provide flavor. (pg 598)
Följaktligen kan den 7% (5% + 2%) anses vara den övre gränsen för proteinutvinning, vilket givetvis kommer att bero på kött- och kokningsprocessens specifika egenskaper. McGee fortsätter sedan att diskutera den lämpliga processen för utvinning, börjar med kallt vatten gradvis uppvärmd:
The cold start and slow heating allow the soluble proteins to escape
the solids and coagulate slowly, forming large aggregates that either
rise to the surface and are easily skimmed off, or settle onto the
sides and bottom. A hot start produces many separate and tiny protein
particles that reamin suspended and cloud the stock; and a boil churns
particles and fat droplets into a cloudy suspension and emulsion. (pg 599)
Detta indikerar också att mängden emulgerat fett i hög grad beror på tillagningsprocessen utöver fettinnehållet hos de ursprungliga ingredienserna. (Jag har inte kunnat hitta mycket på skillnader i extraktionsprocessen för olika animaliska fetter.)