How Long Will Pork Fat Last in the Freezer? The Complete Guide

Freezing is a well-known and widespread preservation method, prolonging the shelf-life of meat and many other food items. Many people like to freeze meat because it keeps it almost fresh for a long time and can be shipped long distances. However, depending on the time and temperature combinations during frozen storage, changes in meat quality can indeed occur. One of these changes is lipid oxidation, which is a major cause of meat going bad and giving it that unpleasant rancid taste and smell. It is important to remember that freezing, which is how we store and distribute food today, is not a permanent way to keep food fresh, and quality losses that happened before freezing do not go away.

It is important to look at what pork is made of in order to figure out what might affect how stable it is while it is frozen. Pork is mostly made up of water, protein, and fat. The amounts of these three things vary a lot between cuts, with some being more fatty than others. g. pork belly than others e. g. pork loin. When it comes to storage time, the amount of unsaturated fat in the fat has a big effect on how long it will last. This is because unsaturated fats are easily turned into oxygen. Furthermore, pork also contains components that may promote oxidation such as iron. Finally, the amount of water influences the freezing process, as high water content requires increased freezing times.

Freezing is a well-known and widespread preservation method, prolonging the shelf-life of meat and many other food items. Many people like to freeze meat because it keeps it almost fresh for a long time and can be shipped long distances. However, depending on the time and temperature combinations during frozen storage, changes in meat quality can indeed occur. One of these changes is lipid oxidation, which is a major cause of meat going bad and giving it that unpleasant rancid taste and smell. It is important to remember that freezing, which is how we store and distribute food today, is not a permanent way to keep food fresh, and quality losses that happened before freezing do not go away. It is important to look at what pork is made of in order to figure out what might affect how stable it is while it is frozen. Pork is mostly made up of water, protein, and fat. The amounts of these three things vary a lot between cuts, with some being more fatty than others. g. pork belly than others e. g. pork loin. When it comes to storage time, the amount of unsaturated fat in the fat has a big effect on how long it will last. This is because unsaturated fats are easily turned into oxygen. Furthermore, pork also contains components that may promote oxidation such as iron. Finally, the amount of water influences the freezing process, as high water content requires increased freezing times.

Freezing is a well-known and widespread preservation method, prolonging the shelf-life of meat and many other food items. Many people like to freeze meat because it keeps it almost fresh for a long time and can be shipped long distances. However, depending on the time and temperature combinations during frozen storage, changes in meat quality can indeed occur. One of these changes is lipid oxidation, which is a major cause of meat going bad and giving it that unpleasant rancid taste and smell. It is important to remember that freezing, which is how we store and distribute food today, is not a permanent way to keep food fresh, and quality losses that happened before freezing do not go away.

It is important to look at what pork is made of in order to figure out what might affect how stable it is while it is frozen. Pork is mostly made up of water, protein, and fat. The amounts of these three things vary a lot between cuts, with some being more fatty than others. g. pork belly than others e. g. pork loin. When it comes to storage time, the amount of unsaturated fat in the fat has a big effect on how long it will last. This is because unsaturated fats are easily turned into oxygen. Furthermore, pork also contains components that may promote oxidation such as iron. Finally, the amount of water influences the freezing process, as high water content requires increased freezing times.

Several things affect the freezing process: 1) the size of the meat cuts; 2) the difference in temperature between the meat’s surface and core; and, as we already said, 3) the amount of water in the meat. During the freezing process, the water will gradually change into ice, see Figure 1.

The speed by which the meat is frozen is closely related to the freezing method used. An example of this is the time used for reaching -18°C. Freezing with cryogen is one of the fastest ways. A three-kilogram pork loin will reach -18°C in just two hours. It will take 17 hours to reach -18°C with air blast, and 24 hours with still air in a freeze room. That is, if the loins aren’t stacked on pallets and packed together in cardboard boxes, it will take a lot longer for them to reach -18°C. In the worst case, it could take several days before all the meat cuts are frozen.

The impingement freezer is another example of a fast and industrial way to freeze meat. In this freezer, each piece of meat is put on a separate belt and moved through a tunnel with air blasts. The meat is frozen within a short time e. g. one hour depending on the size of the individual cuts.

Shelf-life depends on temperature, packaging method and meat quality

The big question is how long pork can be kept in the freezer. Danish rules from the 1960s say that pork has a five-month shelf life at -18°C and a seven-month shelf life at -20°C. Even though these shelf-life estimates were based on half-cashes and can’t be directly applied to smaller cuts, the fact that the shelf-life increases exponentially with temperature is interesting and is thought to be true for pork in general (Figure 4). For smaller cuts like pork chops, an estimated shelf-life for storage at -20°C is 10 months3. This clear exponential relationship between temperature and shelf life shows that temperature is very important for keeping pork stable while it’s frozen.

At DMRI, frozen pork loins were stored in the freezer (approximately -18°C) for 4. 5 years, during the first two years in oxygen permeable film and the following 2. 5 years in air tight vacuum packs. The loins were cut into chops, pan-fried, and tasted by a trained panel of tasters. The meat’s outer layer had started to oxidize, giving it a rancid, old, cardboard-like taste. The core of the meat, on the other hand, did not taste oxidized; instead, it had a pretty bland taste.

It’s likely that pork would last between 5 and 10 months when stored frozen. 5 years. But there aren’t any well-documented rules about how long different pork products (cuts with more or less fat), packaging methods, and temperatures should be kept.

It is important to remember that meat that has been thawed is never better than meat that has been frozen. The most important things that affect the quality of thawed meat are 1) the quality of the meat when it was frozen, 2) the freezing process, especially how fast it was frozen, and 3) how it was stored.

One of the major quality concerns is the drip loss after thawing, as drip loss equals money loss. The amount of water lost from the meat is directly related to the speed of freezing. An example based on a DMRI experiment is shown in Table 1.

As can be seen from Table 1, the loss of water is minimised by the faster freezing method.

Table 1. Pork loins. Loss of water based on drip loss after thawing and cooking loss after heat treatment (medium done, approx. 68°C core temperature) in relation to two different freezing methods.

The materials used to package meat after it has been frozen are also important for its quality. As we already said, the degree to which materials let oxygen through affects the oxidation process. Table 2 shows data from a DMRI experiment that shows how the type of packaging material used can also change the amount of water lost.

Table 2. Drip loss after being frozen is affected by the type of packaging used: PE-Wrap (polyethylene, oxygen-permeable film) vs. vacuum pack (oxygen-impermeable film)

When engineers at DMRI came up with the “EZ drip loss method”4, it became easy and accurate to measure drip loss.

There are a lot of things that affect how long frozen pork will last and how good it will be when it’s thawed. These include the quality of the meat when it was frozen, how it was packaged, and how it was stored. It’s important to remember that freezing meat doesn’t make it better, and bad handling before freezing doesn’t make it better after freezing.

1. Jay, J.M. (2000). Modern Food Microbiology. 6th edition. Aspen Publishers, inc. pp.679

2. Hansen, E. , Lauridsen, L. , Skibsted, L. H. , Moawad, R. K. , Andersen, M. L. (2004). Oxidative stability of frozen pork patties: Effect of fluctuating temperature on lipid oxidation. Meat Science 68: 185-191.

3. Bøgh-Sørensen, L. , Jensen, J. H. , Jul, M. (1983). ”Chapter 5: Freezing” in Konserverings teknik 1, 2nd edition. DSR Forlag, Copenhagen.

4. Christensen, L.B (2003). Drip loss sampling in porcine longissimus dorsi. Meat Science 63: 469-477

Dr. Lene Meinert has been a consultant, since 2008, at the Danish Meat Research Institute, centre of meat quality. Lene has a master’s degree and a PhD in food science from the University of Copenhagen. Her studies focused on chemistry, microbiology, and sensory science. We are now seeing her in a number of R Lene has a wide experience in the coordination of research projects involving both universities and the industry.

Effects on shelf-life during frozen storage

Generally, the shelf-life of meat is limited by the growth of bacteria and chemical changes in the meat. In frozen meat, it is the chemical changes that prevail. However, chemical reactions are slowed down closely related to the lowering of the temperature. Also, the lack of oxygen slows or stops the oxidation reactions, which means that the packaging materials also affect how long the food will last.

It is not good for most bacteria to grow at temperatures below 0°C. Molds and yeasts are more likely to grow at freezing temperatures. Some processed products e. g. Bacon and other foods that might contain so-called “cryoprotectants” are more likely to allow microbes to grow below zero degrees. g. sugar compounds, that depress the freezing point of water1. It is important to remember that adding sugar to bacon is only done for taste and not because it will freeze better. Adding salt will also make it freeze faster.

Chemical changes, and especially lipid oxidation, can still occur at low temperatures and even below -20°C. As the temperature is lowered, the reactions do slow down. But when water freezes, the amount of pro-oxidants (compounds that start the oxidation reaction) increases. This causes reactions to keep going.

Oxidation progresses in several steps, each step generating oxidation products with different properties. In the beginning, the oxidation products (also known as primary oxidation products) don’t change the meat in a way that can be seen. Later on, though, when secondary oxidation products are made, the rancid taste and smell will become clear to anyone who uses the meat, whether they are a meat processing plant or a consumer. So, if oxidized meat or fat is used to make sausages, for example, there is a good chance that the sausages will taste bad. A test with vacuum-packed frozen pork patties showed that lipid oxidation, as shown by secondary oxidation products (TBARS), did happen at -23°C. Interestingly, changes in temperature between two storage temperatures sped up the oxidation process, leading to TBARS levels that were similar to those found in patties that were stored at one of the two temperatures all the time (e g. -10°C and -20°C). On the other hand, at -40°C no increase in TBARS was observed2 (see Figure 3).

Although patties made from pork belly had 23% fat and patties made from loin had 2% fat, the TBARS rose in a very similar way and reached the same level after about 270 days (not shown). Because of the way the fatty acids were made, a lot of the fat from the pork belly was saturated and not likely to turn rancid. So in this case the higher fat content did not lead to a higher degree of oxidation. In fact, pure pork lard, which is mostly made up of saturated fat, stays fresh longer than pork cuts that only have a small amount of fat (e.g. g. loin), as this fat intra muscular fat is generally unsaturated and may oxidise.

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