Quality of Meat
Meat quality is determined by the muscle pH and its change in time, which in turn is strongly dependent on pre-slaughter conditions (i.e. stress) imposed on the animals. Too much stress can affect the taste and aroma of the meat itself and of further products made out of it. Monitoring the pH of slaughtered meat provides a suitable tool to ensure its quality and consequently also good consumer’s experience of the product. Therefore measuring the pH is a common use in the meat industry and even obligatory in some countries.
Indicator for Fish Freshness
For fish, the pH value is an indicator for the freshness of the meat, which is fundamental to fish quality. A few hours after death, the glycogen in the muscle will be metabolized to lactic acid causing a drop in pH. This lower pH will contribute to an increased shelf-life of the fish and moreover a good nutritional state of the fish. However, during storage the pH will start to increase, reflecting among others the production of alkaline bacterial metabolites in spoiling fish. The higher the storage temperature, the faster is the increase in pH which can be used as a measurement for quality deterioration and shelf life prediction in the fish marketing sector. Thus, checking the pH of the fish after a certain period of storage can determine the state of its freshness.
Behavior of pH in Meat
Glycogen is the substance in living muscle that is cause for pH changes post-mortem. It is the prime “fuel” used during the contraction of muscle. When adrenaline is released to prepare a living animal for a possible burst of immediate activity, it ensures glycogen is broken down in readily available energy providers (glucose). Glycogen however is also involved in the process of stress as too much stress will result in a release of adrenaline, causing the glycogen content to drop. So, depending on the pre-slaughter stress there is a varying amount of glycogen present in the muscles at the time of slaughter.
The pH of living muscle is effectively close to neutral. After slaughter oxygen is not available and the muscle cells try to stay alive using the only source of energy then available, which is glycogen. The glycogen will be converted into lactic acid by a process called anaerobic glycolysis. Since there is no longer any blood supply to remove this lactic acid, it slowly accumulates and the pH will fall within 24 hours. At a certain point conditions in the muscle prevent further glycogen breakdown and the meat is in rigor, also called muscular stiffness.
pH as Measure for Meat Categorization and Carcass Quality
Not all muscles in a carcass will develop the same pH change. It varies between a too slow, incomplete pH fall and a too fast, complete pH fall. For example, when glycogen is nearly depleted by exhaustion by too much stress during pre-slaughter, the pH fall will be slow and incomplete. Categorizing of meat or carcass quality is possible by measurement of pH in one pH critical muscle.
Measurement of pH in Meat and Fish
In non-frozen meat or fish, the pH can be measured by piercing it with the LanceFET pH probe thanks to its PEEK tip with stainless steel point. For those situations where high force and stabbing penetration is required, Wellinq offers the LanceFET probe with thick handle for a comfortable grip while measuring.
The positions of the ISFET and reference electrode have been designed to be clog and pollution resistant. In the event debris has accumulated on the sensor it can be easily cleaned by high pressure flushing, which is of benefit for the probe’s performance and prolonged life.