2009_Book_FoodChemistry

12.5 Water Holding Capacity of Meat 591
Fig. 12.26. Swelling of meat as affected by salts. Beef
muscle homogenate; the ionic strength of the salt added
to homogenate is µ = 0.20; — control, −−− NaCl,
−·−·−NaSCN (according to Hamm, 1972)
The water holding capacity of muscle tissue
soon after slaughter is high because the muscle
Fig. 12.25. Swelling of meat as affected by pH. a Beef
muscle homogenate, 5 days post mortem, b beef muscle
cut in cubes 3 mm edge length, −−−weight increase,
— volume increase (according to Hamm, 1972)
ments (M line, Z line, cf. 12.3.2.1.4) probably occurs,
which facilitates the extension of myofibrils.
The water holding capacity of meat is of great
practical importance for meat processing and is
affected by pH and the ion environment of the
proteins (cf. 1.4.3.1 and 1.4.3.3).
The total charge on the proteins and, hence, their
electrostatic interactions are the highest at their
isoelectric points. Therefore, meat swelling is
minimal in the pH range of 5.0–5.5 (Fig. 12.25).
Addition of salt to meat shifts the isoelectric point
and, hence, the corresponding swelling minimum
to lower pH values, due to the prefered binding
of the anion. This means that, in the presence
of salts, water holding is increased at all pH’s
higher than the isoelectric point of the unsalted
meat (Fig. 12.26).
Fig. 12.27. Water holding capacity and rigidity of beef
muscle. — Water holding capacity, −−− rigidity
(stiffness) expressed as the surface area acquired by homogenate
after being pressed between filter papers, under
standardized conditions (according to Hamm, 1972)