LPT 321: Meat Science (1+1)

WATER HOLDING CAPACITY

• Water holding capacity is the ability of muscle to hold on to or retain its own water or added water under application of pressure.
• The pressure applied may be cutting, grinding, chopping, heating etc,.
• WHC determines weight of meat in fresh meat trade, as lower WHC would mean greater losses in water; the juiciness of fresh meat as well as processed meats, as greater WHC means that greater quantities of meat juices are retained; yield of processed meat products as WHC is directly related to cooking losses and emulsion stability in emulsion based meat products.
• WHC is closely related to pH of meat, both the rate and extent of fall in post-mortem pH.
• Water holding capacity is at its lowest when ultimate pH (the pH at about the time of completion of rigor, and there is no further drop in pH) is reached.
• Water exists in three states in the muscle
• Free Water
• Immobilized Water and
• Bound Water
• Free water is about 10% of the total water present in muscle and this is held by capillary forces ante-mortem, which is lost as the animal dies and hence this fraction of water is inevitably lost, hence does not contribute to WHC.
• Bound water constitutes about 2% of the total water present in muscle and is called so because it is chemically bonded to the proteins of muscle, commonly by hydrogen bonds.
• About 50% of bound water cannot be removed from the muscle and it can’t be removed either in the form of steam by heating or can be frozen, and hence this fraction does not account for the variations in WHC from one sample and the other
• Immobilized water constitutes about 80% of total water in muscle and its state practically determines WHC. Immobilized water, as the name indicates is immobilized by the myofibrillar proteins in the inter myofibrillar spaces.
• The most important factors determining WHC are the ionic effect and steric effects.
• Ionic effects refer to the state of ionization of the proteins of muscle, which directly influences the hydrogen bond formation, as a small polarity is required for two molecules to engage in hydrogen bond formation.
• This is one of the reasons for WHC to be at its lowest when ultimate pH (pHu) is reached, as the pHu of meat is in the range of 5.2 -5.6, and the iso-electric point of myosin, the most important player in hydrogen bond formation is 5.5; hence myosin being neutral in charge, cannot form hydrogen bonds and as a consequence there is depression of WHC.
• Steric effects refer to spatial or more appropriately volume changes in the muscle. If the steric effect are such that the volume available for water to be held in the inter myofibrillar spaces due to close packing of the myofibrillar decrases, as is the case at pHu,WHC diminishes ( Rigor is at its peak as also are actinomyosin formation contraction which obliterates inter myofibrillar spaces).
• WHC is affected by genetics (Halothae gene of pigs prone to Porcine Stress Syndrome,and Rendenment Napole Gene are both associated with Pale Soft Exudative (PSE)condition); handling of animals peri-slaughter, as stress of any kind results in PSE in pigs and Dark Firm Dry (DFD) meat in cattle; and post-mortem handling of meat(Quick freezing, and low temperature during chilling results in greater WHC, and cutting into thin and many cuts resulting in an increase in surface area results in decrease in WHC
• Pale Soft Exudative pork is characterized by very low WHC a Dark Firm Dry beef is characterized by high WHC.