Purge, also known as drip or weep refers to the loss of water due to gravity acting on fresh meat or muscle during storage and handling.
What causes purge in meat?
A combination of altering temperatures and shifting of the structure within the meat causes it to lose the water contained therein.
The liquid which is sometimes found at the bottom of a meat package is what meat scientists call “purge,” is a combination of water and meat proteins that drain from meat. One of those proteins, water-soluble myoglobin which gives the meat its red color, is why the water is also red or dark pink. Meat is normally 75 percent water, which adds to the juiciness of cooked meats. As meat is aged, processed, handled, or cut, proteins lose their ability to hold onto water in a process known as syneresis. Over time, some water is released, and myoglobin flows out with it.
Why should meat retain its juices?
Water holding capacity of fresh meat is an important property as it affects both the yield and the quality of the end product. This characteristic can be described in several ways, but in fresh products that have not been extensively processed, it is often described as drip loss or purge. Purge is among other things unappealing and depending on conditions it can be a breeding ground for harmful bacteria.
The main factors that cause purge in meat
Handling and processing – the number and size of cuts interfere with muscle integrity. The cuts across the meat grain, cause the more processed meats (like ground beef) to drip more.
Temperature – including the rate of freezing and thawing causes the formation of ice from the water molecules which shreds the cell structure. Therefore, chilling at a steady temperature is preferable to freezing.
Reducing purge in meats
Excessive purge is likely to affect the meat or meat product in numerous ways, making it unappealing to consumers. Other than the nutrients lost resulting in quality loss, there is also the proof available upon sight – the discerning consumer is not likely to pick meat sitting in a puddle of liquid within its packaging.
Purge not only affects sales but the shelf life too, and in the long run, the bottom line. When meat cuts are injected with a brine - made from water combined with functional proteins – it helps meat retain moisture, thus extending the yield.