Water in meat

• Water serves as a vehicle for transport of nutrients in the body.
• It constitutes about 75% of fresh meat.
• Water content varies inversely with the fat content in meat.
• The ratio of water to protein is relatively constant 3.6 or 3.7 to 1.
• The retained water contributes to the juiciness and palatability of meat .
• Water within muscle is attached to protein as water is bipolar.
• Water is present in muscle in three forms—
  
  i) Bound water – about 4-5 percent of total water is located in muscle in bound form. It is tightly bound
  and remains so even during application of severe mechanical or any other physical force.
  
  ii) Immobilized water– The water molecules are slightly away from the protein molecules and are
  attached to the bound water molecules but the binding force is weaker as compared to bound water.
  
  iii) Free water – the water is held by the surface forces i.e. capillary forces. The orientation of free water
  molecules is independent of the charged groups.
  
  
• The ability of meat to retain its water during application of external forces such cutting, heating,
  grinding and pressing is called the water holding capacity (WHC) of meat.
  
• Several factors influence the water holding capacity of meat out of which there are two effects which
  are very important–
  
  i) Net charge effect – The post- mortem production of lactic acid and drop in pH lead to reduction
  of reactive groups on proteins as a result the binding sites are not available to water molecules. It
  happens due to pH at isoelectric point which results into equal positive and negative charges on the
  myofilaments. This results in attraction of the charges to each other and reduction in number of reactive
  groups therefore only the left overs are available to attract water. As a result less water will be held. A
  look at the Graph will further explain the net charge effect to you.
  
  ii) Steric effect – it occurs due to combining of divalent cations such as Ca2+ and Mg2+ with the negatively
  charged reactive groups on the proteins. This results into attraction between the protein chains and
  prevent the available reactive groups on proteins from binding with water. The steric effect can be minimized
  by aging of meat which permits proteolytic activity and redistribution of monovalent ions around the
  proteins. As a result divalent cations are freed which causes freeing of half of the binding sites which
  would then become available for binding water.