Adipocere is a decomposition product of hydrolysis and is composed of primarily composed of fatty acids. Adipocere mainly forms in warm, humid, and anaerobic environments. Despite the number of studies done on its formation, frequency, and physical characteristics, it is not a well-defined subject (Pfeiffer, Milne, & Stevenson, 1998). Adipocere can help preserve possible wounds and physical characteristics of the remains, while a positive, It can make the determination of the post mortem interval challenging since the remains are preserved continuously, therefore making the post mortem interval unreliable (Kasuda et al., 2016). Adipocere formation has a broad range of factors that are present in the type of decomposition environment that allows adipocere formation to either advance or be disrupted during the early stages of the process.

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Adipocere forms from the adipose tissue in ideal anaerobic environments. It results from hydrolysis and the hydrogenation of triglycerides, and this happens to be a significant component of adipose tissue by bacterial enzymes (Shari L. Forbes, Stuart, Dadour, & Dent, 2004). When hydrolysis of fatty tissue takes place, fatty acids and glycerol will result. In most studies, Gas Chromatography-Mass Spectroscopy (GCMS) is used to determine fatty acid composition. Adipocere is composed of primarily palmitoleic, palmitic, myristic, stearic and oleic acids (Forbes et al., 2004). One of the byproducts during the process of hydrolysis and hydrogenation can be formed due to cation exchange once the fatty acids have been severed and attach to the potassium or sodium ions that are found in interstitial fluid, likely happening early in the decomposition process. In the case that a body is placed in an aquatic or soil environment, ions become displaced from the magnesium or calcium ions, forming the salts found in fatty acids later in the decomposition process (Forbes et al., 2004).

The ideal environment for the formation of adipocere needs to have hotter temperatures, a water source needs to be present and an anaerobic environment (Forbes et al., 2005). However, it has been found that though excess water helps advance the formation of adipocere, it is not necessary. It is a general misconception that adipocere forms on remains wholly immersed in a water body or an excess amount of water need to be present in the burial site. In recent studies it has been found that water in the bodily tissue is enough for hydrolysis to occur, meaning that adipocere can occur on remains found in a dry environment (Forbes et al., 2005). It is difficult to determine when adipocere begins to be detected as it varies from multiple studies and literature, depending on the physical condition of the body, cause of death, and burial environment it can range from as little as a few days, months, and even years.

Adipocere formation deals with several different factors, such as the physical condition of the body, cause of death, burial environment and on time spent between the time of death and the time of burial. In these environmental factors, temperature, oxygen content, soil type, humidity, pH, and if there are microorganisms are present are essential in order to understand what factors affect adipocere formation and how the factors affect adipocere formation.

The effect temperature has on a body that is buried deals with the ideal temperature that allows bacteria to thrive (Mohan Kumar, Monteiro, Bhagavath, & Bakkannavar, 2009). A study recovered 37 bodies, and it was found that the environmental climate needs to be humid and anaerobic, where moisture is favoured (Sikary, Behera, & Murty, 2018). It is more likely for adipocere formation to occur in subtropical climates.

The oxygen levels that are present in a burial environment are significant as the bacteria that help to advance decomposition and is found on decomposing bodies needs an adequate amount of oxygen to survive and thrive (Forbes et al., 2005). In anaerobic conditions, adipocere formation is favoured due to adipocere being a result of oxygen deprivation from the incomplete degradation of triglycerides that produces fatty acids. In the study of Forbes et al., a piece of tissue was placed in an anaerobic environment and was compared with a control sample placed in an anaerobic environment. It was found that in the aerobic environment, no adipocere was present, and after 12-months, there was no tissue left to observe, the entire tissue sample decomposed instead of being preserved by the adipocere. This proves that anaerobic conditions are favourable for adipocere formation.

In the presence of bacterial enzymes, the rate of hydrolysis can increase as hydrolysis has a vital role in adipocere formation. In some studies, it has been found that the most common bacteria is the Clostridia (anaerobic) species. Certain species of Clostridia produce active lipolytic enzymes that help to increase hydrolysis and hydrogenation of adipose tissue in the proper temperature conditions, enhancing the adipocere formation (Takatori, Gotouda, Terazawa, Mizukami, & Nagao, 1987).

The soil type is one of the most, if not the most important environmental factor in buried remains. In the Forbes et al. study, the focus was on the effect of the soil type on adipocere formation. Five types of soil samples were collected from Portugal: organic, sandy, gravel and clay gravel. In a high moisture environment, organic and gravel soil had no significant amounts of fatty acids whereas in the sandy soil there were high amounts of palmitic and myristic fatty acids, being followed by the clay gravel soil. In a low moisture environment, the sandy soil continued to form adipocere, but smaller amounts of fatty acids were found.

The presence of clothing and different types of materials on the body when it is buried can have a dramatic effect on the decomposition rate and the formation of adipocere on the remains. In the Notter and Stuart study, pieces of tissue were taken and covered in polyester, acrylic, wool, cotton materials. It was observed that the synthetic fibres had poor water absorption, not being able to attract water molecules not allowing decomposition products to be removed steadily. More natural fibres were more water-absorbent due to hydrogen bonding, possibly allowing decomposition products to be removed more steadily. The synthetic fibres formed adipocere slightly slower than the natural fibres that advanced the process early.

In many cases, even when the conditions are favourable, adipocere does not form on the body. When this happens the antemortem conditions of the body become more critical, all body decomposition occurs differently and in the presence of adipocere formation sex, age, and the physique of the body can have different effects. Females are more likely to form adipocere due to the higher content of adipose tissue on the body (Pfeiffer et al., 1998). Some studies have found that in infants generally under the age of one who is well-nourished can be prone to forming adipose tissue (Fiedler & Graw, 2003). The size of the body and physique is essential due to the fat tissue on the body. Slim individuals are less likely to form adipocere since there is less fat tissue present in the body, whereas more significant individuals are more likely due to more fat tissue being present (Pfeiffer et al., 1998).

Many of the studies have shown just how many factors are involved in the formation of adipocere. Only a few of these factors are fully agreed upon by the majority of researchers, the few factors agreed upon are the presence of adipose tissue, a mild temperature, an ample amount of moisture and an anaerobic environment. It is understandable how the majority of factors presented can be contradicted between research groups. It is stated that temperatures need to be relatively high (below 40 degrees but above 10 degrees celsius) in order for adipocere to form (Forbes et al., 2005). Kasuda et al., the study focused on a body that was found at the bottom of a lake, the temperature ranged from 5 to 8 degrees Celsius in the winter and 21 to 25 degrees in the summer. It was around 25 degrees Celsius when the body entered the lake seven years earlier. The temperature declined shortly after as the seasons changed and the adipocere formation still moved onto the early and intermediate stages suggesting that the adipocere formation continued to take place even when the temperature was below 10 degrees Celsius.

It is generally accepted by researchers and the scientific community that anaerobic conditions are necessary for adipocere to form. It is also common knowledge that anaerobic bacteria can advance adipocere formation. A study was done by Forbes et al. found this unnecessary. It was thought that the soil surrounding the remains contained the bacterial enzymes that increase adipocere formation instead of the anaerobic bacteria through the experimentation on sterilized soil. Instead of the bacteria in the soil, the bacteria needed to form adipocere was present on the decomposing tissue, explaining how adipocere can form in a sealed environment (Forbes et al., 2005).

It has also been believed for a long time that moisture is necessary in order for adipocere to form due to the hydrolysis of the triglycerides needing water to go through the process. Two studies, Forbes et al. and Sikary et al.found that adipocere formation can happen in a dry environment. A majority of the moisture found in the body’s tissue is all that is needed for adipocere to form and extra moisture helps to forward the process.

Another factor has to deal with body coverings found on remains that are more likely to aid in adipocere formation. Notter & Stuart. studied four types of fabric. The synthetic fibres formed adipocere but at a slower rate than the natural fibres. The natural fibres had formed adipocere quite quickly as the moisture absorbance rate was quick, allowing decomposition product to flow out faster.

Once the environmental conditions have been discussed, there are antemortem body conditions that can factor into the formation of adipocere. Sex and body size is a factor that can be agreed on in most scientific groups. Females tend to have a higher fat composition and different distribution than males making them likely more susceptible to adipocere formation (Fiedler & Graw, 2003). If a person is smaller, they are less likely to form adipocere, and if a person is larger, they are more likely to form adipocere due to the higher fat composition (Pfeiffer et al., 1998). Age is a factor that is more controversial since there have been studies showing that young people are more likely to form adipocere due to a higher fat composition. There have also been studies where there was no correlation in age and adipocere formation. This factor could depend more on antemortem weight.

Numerous factors and their impacts have been discussed. Environmental factors could be area specific. Temperature, moisture, the soil type and presence of microorganisms can change with the seasons and correlate with a specific geological area. If the effects of each factor are known and can apply to a specific location, it would help in estimating the post mortem interval. Body coverings are generally used in illegal burials and should be dealt with on a case to case basis. If a corpse were buried directly in soil wearing polyester clothing, a knowledge that this would increase adipocere formation would help to represent the post mortem interval. The impact of antemortem conditions deals with sex, age, and body size. In future studies, female and male bodies with the same fat composition should be compared and buried under identical conditions in order to truly understand what affect sex has on adipocere formation. It is hard in developing an estimate for a post mortem interval even though there are proven factors that contribute to adipocere formation, and it is likely to be almost impossible to figure out. Too many factors contribute to adipocere formation, and it would be hard to develop a scale that could be used in every situation. Many effects are known today and can continue to make contributions in helping to develop an estimate of the post mortem interval.

Literature Cited

Fiedler, S., & Graw, M. (2003). Decomposition of buried corpses, with special reference to the formation of adipocere. Naturwissenschaften, 90(7), 291–300. https://doi.org/10.1007/s00114-003-0437-0

Forbes, Shari L., Stuart, B. H., Dadour, I. R., & Dent, B. B. (2004). A Preliminary Investigation of the Stages of Adipocere Formation. Journal of Forensic Sciences, 49(3), 1–9. https://doi.org/10.1520/JFS2002230

Forbes, S. L., Dent, B. B., & Stuart, B. H. (2005). The effect of soil type on adipocere formation. Forensic Science International, 154(1), 35–43. https://doi.org/10.1016/j.forsciint.2004.09.108

Forbes, S. L., Stuart, B. H., & Dent, B. B. (2005). The effect of the burial environment on adipocere formation. Forensic Science International, 154(1), 24–34. https://doi.org/10.1016/j.forsciint.2004.09.107

Henderson, C. Y., King, G. A., Caffell, A. C., & Allen, R. (2013). Adipocere Inside Nineteenth Century Femora: The Effect of Grave Conditions. International Journal of Osteoarchaeology, 25(6), 960–967. https://doi.org/10.1002/oa.2350

Kasuda, S., Kudo, R., Yuui, K., Imai, H., Nakata, M., & Hatake, K. (2016). An autopsy case of complete adipocere formation. Legal Medicine, 18, 49–51. https://doi.org/10.1016/j.legalmed.2015.12.003

Mohan Kumar, T. S., Monteiro, F. N. P., Bhagavath, P., & Bakkannavar, S. M. (2009). Early adipocere formation: A case report and review of literature. Journal of Forensic and Legal Medicine, 16(8), 475–477. https://doi.org/10.1016/j.jflm.2009.07.004

Notter, S. J., & Stuart, B. H. (2011). The Effect of Body Coverings on the Formation of Adipocere in an Aqueous Environment. Journal of Forensic Sciences, 57(1), 120–125. https://doi.org/10.1111/j.1556-4029.2011.01943.x

Pfeiffer, S., Milne, S., & Stevenson, R. M. (1998). The Natural Decomposition of Adipocere. Journal of Forensic Sciences, 43(2), 368–370. https://doi.org/10.1520/JFS16147J

Sikary, A. K., Behera, C., & Murty, O. P. (2018). Adipocere Formation in Subtropical Climate of Northern India: A Retrospective Study. Journal of Forensic Sciences, 64(1), 260–263. https://doi.org/10.1111/1556-4029.13847