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Formation of adipocere

Formation of adipocere

Formation of adipocere

Introduction

Various studies have been conducted to analyze and determine how adipocere is formed. For example, Takatori (1996) investigated the meachanism of adipocere formation and its relation to other biochemical reactions, whereas Forbes, Stuart, & Dentl (2002) investigated the identification of adipocere in grave soils. The authors further enhaned their research in 2005 by focusing their concentration on the effect of the burial environment on adipocere formation. In the following sections, the author analyze these studies in order to comprehensively describe the process of adipcere formation and relate the findings in the  context of forensic anthropology and how the recent researches and findings can be helpful in this field.

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Research Method

The researcher has adopted the meta-analyis research method for this paper in order to collect the secondary data from different journals and libraries and analyse the formation of adipocere and its significance in the forensic anthropology. With regard to meta-analysis, there is a growing recognition of the fact that the careful integration of knowledge about a topic in itself constitutes an important scholarly endeavor that can contribute new knowledge (Patten, 2005). Meta-analysis treats the findings from one study as a single piece of data; in other words, the study is the unit of analysis. The findings from multiple studies on the same topic, therefore, can be combined to produce a data set that can be analyzed in a manner similar to that obtained from individual subjects. By using the meta-analytic procedure, the researcher is provided with a convenient and objective method of integrating findings from a large body of studies and of observing patterns and relationships that might otherwise have gone undetected (Patten).

Data Sources and Selection

The studies used here are from original research. Lam and Kennedy (2005) emphasize that meta-analysis “can summarize various findings…more objectively than can expert opinion or qualitative reviews” (p. 168). However, there is a best practice process for meta-analysis to obtain a high quality study (Lam & Kennedy):

 

Reading and Coding of Each Study.

The research studies analyzed met the following criteria:

  1. Be written in English or be an English translation.
  2. Have the concept of formation of adipocere.
  3. Describe the results concluded from the previous researchers.
  4. Have been completed since not older than 2000.

 

Computer searches were conducted using the following retrieval databases/search engines: Educational Resources Information Center (ERIC), Dissertation Abstracts, Cumulative Index to Nursing & Allied Health Literature (CINAHL), Academic Search Premier, Article 1st, ECO, Expanded Academic ASAP, Gale Virtual Reference Library, Ingenta, ProQuest Journals, ProQuest Research Library, UMI ProQuest Digital Dissertations, and Wilson Select Plus. These resources were selected because they are the most efficient in obtaining information regarding economical issues.

Descriptor search terms that were used are: formation of adipocere, forensic anthropology, death, dead body and chemistry. In addition, all studies retrieved were examined to identify additional studies that could be included within this study. In order to increase reliability, this researcher was the only one reading the research articles and applying the tool to the information. As noted by Cooper andSchindler (2001), reliability is increased when a researcher minimizes “external sources of variation” and standardizes “conditions under which measurement occurs” (p. 218).

Cooper and Schindler (2001) have identified these four rules for coding: The category sets should be “appropriate to the research problem and purpose, exhaustive, mutually exclusive, and derived from one classification principle” (p. 425). Polit and Hungler (1999) suggest that no matter what type of coding is used that “it is important that all responses be of the same form and precision” (p. 547). McCune (1988) also added another category termed other “for which less than five studies investigated the variable in association with adult self-direction in learning” (p. 38). This was used to write in “those variables for which at least five studies had examined the variable in relation to adult self-direction in learning, but which were not indicated on the coding instrument” (McCune, p. 38).

Limitations of Meta-analysis

Primarily, the researcher needs to choose quality studies to be able to produce quality results (Fitzgerald & Rumrill, 2003; Gall, Borg, & Gall, 1996; Patten, 2005). It may be impossible to find research studies that are exactly alike with the variety of researchers and the quality of reporting; but an attempt was made to match all salient features of McCune’s 1988 analysis from the selection of reports to the coding of features. It is important to remember that a meta-analysis reflects only what has been published and is only as good as the studies reviewed.

Formation of adipocere

The first study that seemed to be significnat on the topic was of Forbes, Stuart, & Dentl ( 2002) whoe investigted the identification of adipocere in grave soils. According to the authors, adipocere is formed due to the postmortem conversion of body fat into a lipid mixture. It is bellied that partial formation of adipocere can occur in as little as 6 weeks whereas complete transformation of the whole body may take years, depending on the conditions under which the process takes place (Forbes, Stuart, & Dentl ( 2002). However, it should be noted that immediately after the death of human beings, the process of decay commences and will usually pass through a number of stages including autolysis and putrefaction (Forbes & Stuart, 2005). The previous researches have shown the importance of water and bacteria in the formation of adipocere (Pfeiffer, Milne and Stevenson, 1998). Although the researchers have determined that the free fatty acids which contain even number of carbon atoms are the major constituents of adipocere, however, the exact nature of adipocere is yet to be determined. Due to its importnance in forensic anthropology, researchers have found infrared spectoscocpy for the understanding of adipocere in grave soils. The technique of infrared spectroscopy has been proved useful for detection and characterization of adipocere. However, it is not clear if the minimal amount of adipocere contained in soil samples may be proved insensitive in these cases. Some other methods like Gas chromatography–mass spectrometry (GC–MS) have also been used for the investigation of very low concentrations of adipocere. Especially Gas chromatography has been used by many researchers and particualry Takatori et al . (1996) was successful in identifying hydroxy fatty acids and oxo fatty acids present in human adipocere.

In the study on identification of adipocere in grave soils Forbes, Stuart, & Dentl ( 2002) used GC-MS to analyze the adipocere content of soil samples recovered from human grave exhumations. For this purspose, the researchers collected a sample from cemetery sites, as well as forensic grave sites. The researchers also studied the soil using X-ray diffraction to characterise the mineral content of the soils’ environments. The results of this study demonstrated that the composition of the adipocere was found to be dependent on the soil environment. From this finding  the researchers concluded that relatively subtle differences in the soil mineralogy and texture can inhibit the formation of adipocere, whilst the presence of coffins or the influence of other organic materials may also be a factor.

In another study Forbes, Stuart, & Dentl (2005) enhanced their research and focused on the the effect of the burial environment on adipocere formation. In this study, the researcher  prepared three replicates of the control and other burial environments and conducted the experiment for a period of 12 months. The researchers monitored each container regularly to ensure it accurately mimicked the particular environment which it aimed to investigate. After the completion of the study, the adipocere formation was documented in situ. Samples of adipocere were collected from each burial environment and placed in a sealed specimen container prior to analysis. The results of this study demonstrated that  the control burial environment involved the minimum factors necessary for the formation of adipocere (i.e. adipose tissue, moisture, bacteria and anaerobic conditions). The loamy sand environment was representative of a common soil and the formation of adipocere in this environment allowed it to be classed as the control for experimental purposes. All other burial environments included the same soil type and fatty tissue and were subsequently compared with the control environment to determine the effect of the particular burial factor on the extent of adipocere formation.

The formation of adipocere requires moisture for the hydrolytic conversion of triglycerides to free fatty acids. It was previously believed that adipocere formation could only occur in large bodies of water or water-logged environments. Studies have since shown that adipocere can form by utilising the moisture present within the body’s tissues. Hence, the presence of adipocere in a burial environment is not unusual even in a dry, soil environment.

 

In order to determine the effect of particular burial conditions on adipocere formation, experiments were conducted in a laboratory environment so that the individual variables could be adequately controlled. The experiments were conducted in large decomposition containers which included a tap for draining purposes and an airlock seal for the release of gases present within the container. Due to ethical restrictions within Australia, the use of human adipose tissue was not a viable option for this study. Current considerations suggest that decomposing pigs are the next most reliable model [16,17] and this study therefore utilised domestic pigs which were reared for commercial use. Pig adipose tissue collected from the abdominal region and still containing muscle and skin was used for each experiment. To ensure adipocere formation occurred, each experiment included those factors known to enhance adipocere formation, namely sufficient adipose tissue, moisture, bacteria, and a relatively anaerobic environment. A control environment was created whereby the tissue was buried within a damp soil containing a loamy sand composition with pH approximately 5.2. Additional environments were prepared in the same manner with the individual variable of interest altered accordingly. The experiment was conducted in a temperate environment which averaged approximately 22 8C over a 12-month period. The factors investigated in this study were pH (including the presence of lime), temperature, moisture and oxygen content. The pH of the burial environment was altered to investigate both acidic and alkaline environments. A highly acidic environment (pH approximately 2.4) was created through the addition of 10 M hydrochloric acid (HCl) to the soil. A mildly alkaline environment (pH approximately 8.5) was produced through the addition of 5 M sodium hydroxide (NaOH) to the soil whilst the highly alkaline environment (pH approximately 12.6) was created by covering the pig tissue in lime. The latter environment was included due to its occurrence in forensic situations whereby lime is often used to hide the odour and alter the rate of decomposition [18]. The pH values were determined using calibrated meters for measuring pH. Avariation in temperature was explored by investigating the extremes of cold and warm environments. A cold environment was achieved by placing the decomposition containers in a refrigerated environment held at 4 8C. A warm environment was created by placing the containers in a large water bath maintained at 40 8C. Both environments mimicked extremes in temperature variation when compared to the mild temperature of the control environment. The extremes aimed to represent temperature fluctuations which may be experienced in shallow grave sites of a forensic nature.

 

This study demonstrates the effect of physical conditions on the rate and extent of adipocere formation from pig adipose tissue in a controlled soil, burial environment. The majority of factors considered were shown to be conducive to adipocere formation in a soil burial environment. The burial factors of cold temperature, lime and aerobic conditions showed a reduced or inhibited rate of adipocere formation when compared to the control environment, whereas those of mildly alkaline pH, warm temperatures, and anaerobic conditions proved to promote the formation of adipocere. The results are useful for demonstrating the effect of an individual burial factor on adipocere formation but cannot be extrapolated to all burial environments. Further studies must be carried out to replicate these results and investigate the effect of combining the individual factors in a soil decomposition environment (Forbes & Stuart, 2005).

 

According to Takatori (1996), adipocere can be formed from any of the body fats. However, there has been no evidence that fatty acids synthesized from protein by some microorganisms could become adipocere. The fat in human adipose tissues is liquid at normal temperatures. More than 60% of total fatty acids in the fat of adipose tissues consist of oleic, linoleic and palmitoleic acids, which are liquid at normal temperatures. (Takatori, 1996).

The study conducted by Takatori (1996) revealed that adipocere, one of the postmortem changes , is charactereised with specif fatty acids possessing higher melting points, together with soap, play an important role in the formation of adipocere.  In his analsis of the formation of adipocere, Takatori (1996) concluded that the fatty acids were shown to be mainly lo-hydroxystearic and IO-hydroxypalmitic acids. Moreover, slight amounts of lo-oxostearic and lo-oxopalmitic acids, which have higher melting points than those of hydroxy fatty acids, exist in the adipocere as well. The substantial adipocere is formed and stabilized by these specific fatty acids together with the soap. The hydroxy fatty acid (OHFA) and 0x0 fatty acid (OXOFA) are biosynthesized by some bacterial enzymes.

Conclusion of the study

From the meta-analysis of this study, it becomes evident that all the researchers agree that soon after the death of human being, the process of decay of human remains commences and usually passes through a number of stages including autolysis and putrefaction. Fatty tissues are the major components of its formation which comprise mainly triglycerides which during decomposition undergo hydrolysis to yield free fatty acids. Although the process of formation of adipocere starts within the first 6 weeks after the death of human being, the complete transformation of the whole body may take years, depending on the conditions under which the process takes place. Water and bacteria have been found to be necessary ingredients in the formation of adipocere

Significance of the adipocere

The understanding of formation of adipocere is vitally important especially in forensic cases in which the forensic experts can determine the death period of a dead body. This can be very helpful in the cases where some unknown dead body is found and the forensic expert can determine when it died.