Decay

8 Key excerpts on "Decay"

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  eBook - ePub

  Food Preservation and Biodeterioration

  • Gary S. Tucker(Author)
  • 2016(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  1 Control of Biodeteriorationin Food

  1.1 OVERVIEW

  All food undergoes deterioration to some degree once harvested or slaughtered. The deterioration may include loss of nutritional value, organoleptic and colour changes, and most importantly, safety may become compromised. It is the challenge of the food industry to control this deterioration and maintain the safety of the food, while making sure that the food is as convenient, nutritious and available as it can possibly be.

  Biodeterioration is defined as any undesirable change in the property of a material caused by the vital activities of organisms [1]. It is applicable to many materials for example food, wood, paper, leather, fuels, cosmetics, building materials and building structures. Biodeterioration may be a result of the metabolic processes of one of many microorganisms, or it can be caused by insect, rodent or bird damage. As an incredibly broad and diverse field, all biodeterioration has as a common theme in that it affects materials and substances that we need and value, and that it can largely be controlled by proper understanding of the materials and the possible spoilage organisms and their mechanisms of Decay.

  Biodeterioration is also specifically different from biodegradation in that the changes are ‘undesirable’. Biodegradation occurs when complex materials are broken down by microorganisms to form simple end-products. Within a biological ecosystem, there are microorganisms that produce a host of enzymes that can biodegrade natural as well as some synthetic products; this is very important for maintaining the stability of the ecosystem and is extremely important for water purification and sewage treatment. It is also widely used in the food industry. The main differences between biodeterioration and biodegradation are the undesirability and uncontrollability of the former [2].

  Another important feature of biodeterioration is that it is caused by organisms. According to the definition, it is not the degradation that occurs naturally in some organic materials or foods caused by intrinsic enzymes. These enzymes are present in the product and cause degradation or Decay after death. Loss of food quality by intrinsic enzymes is an important topic as it can cause quality deterioration and render food unacceptable. Reactions due to these enzymes will not be considered in detail in this text, but are important to bear in mind as their activities can make nutrients from the product available and accessible to microorganisms so that biodeterioration reactions can follow [2, 3].

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  eBook - ePub

  Insects and Society

  • Timothy D. Schowalter(Author)
  • 2019(Publication Date)
  • CRC Press

    (Publisher)

  Chapter 16 ). The sequence of assemblages will vary with temperature (for example, between summer and winter) and degree of exposure (for example, on the surface or buried). Furthermore, because flies are initially attracted to open wounds or other injuries, the spatial pattern of maggot distribution can guide investigators to the cause of death.

  Finally, blow fly larvae feed only on dead tissue and avoid any living tissue. Therefore, these larvae have been used for medical treatment of wounds, especially where risk of bacterial infection may preclude more invasive surgical techniques (see Chapter 11 ).

  14.5 Summary

  Decomposition is a key ecosystem process that results in the recycling of dead organic material into new plant growth. In the absence of decomposition, dead plant and animal material would accumulate, interfering with plant growth and making our lives unpleasant. A variety of insects and other arthropods are instrumental in initiating and driving the decomposition process, although bacteria and fungi are responsible for the final breakdown of organic molecules.

  Decomposition consists of four sub-processes. Photo-oxidation is the abiotic breakdown of organic molecules by exposure to sunlight. Leaching is the loss of soluble molecules during percolation of water through organic material. Comminution is the fragmentation of organic debris, largely as a result of feeding by insects and other arthropods. Mineralization is the breakdown of organic molecules, by bacteria and fungi, into simple molecules that can be used by plants for new growth. In the absence of arthropods to fragment litter and introduce bacteria and fungi, decomposition will be delayed and/or greatly prolonged.

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  The Science of Forensic Entomology

  • David B. Rivers, Gregory A. Dahlem(Authors)
  • 2022(Publication Date)
  • Wiley

    (Publisher)

  The types of chemical pathways associated with postmortem biochemistry point to yet another fea- ture of animal Decay: the breakdown of cells and tissues is dependent on both abiotic and biotic decomposition. Abiotic decomposition relies on the Time Body mass loss (%) Above ground Buried or concealed Figure 10.1 Body mass changes of corpse over time based on location. Mass changes with concealed bodies vary dependent on the means of concealment (i.e., wrapped, container) or location. Figure is based on Carter et al. (2007) and Payne (1965). Chapter 10 Postmortem decomposition of human remains and vertebrate carrion 197 chemical action of autolysis and putrefaction as well as physical processes associated with the environ- ment and microhabitat of the corpse. The latter can expand over time to become what is known as a cadaver decomposition island (CDI), which essen- tially encompasses the animal remains and the soil (and inhabitants) that has become saturated with expelled body fluids (Carter et al., 2007). By contrast, biotic decomposition or biodegradation is the cata- bolic degradation of organic material facilitated by living organisms. Several organisms play significant roles as necrophagous and saprophagous nutrient recyclers and include bacteria, fungi, necrophagous insects, and invertebrate and vertebrate scavengers (Barton et al., 2020). Such organisms are pivotal to human decomposition as their presence has a direct effect on the rate of chemical and physical Decay. 10.2 Numerous factors affect the rate of body decomposition Even just a cursory examination of the physical and chemical processes involved in animal degradation should reveal that decomposition is quite complex and can be influenced by a wide range of factors at each step. Temperature is the most important factor affecting chemical and physical decomposition of soft tissues.

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  Fundamentals of Soil Ecology

  • David C. Coleman, D. A. Crossley Jr., D. A. Crossley, Jr.(Authors)
  • 2004(Publication Date)
  • Academic Press

    (Publisher)

  Wasylik, 1995 ).

  Decomposition per se is the catabolism of organic compounds in plant litter or other organic detritus. As such, decomposition is mainly the result of microbial activities. Few soil animals have the enzymes that would allow them to digest plant litter. Animal nutrition depends upon the action of microbes, either free-living in the soil or specialized in the rhizosphere or in animal guts. However, the term “decomposition” is often used more generally to refer to the breakdown or disappearance of organic litter. In that context, the decomposition of organic residue involves the activities of a variety of soil biota, including both microbes and fauna, which interact together. The term “litter breakdown” has been applied to the interactive process, which results in the disappearance of organic litter.

  Continuing interest in decomposition is apparent from the large number of studies of the process that have been published during the past 25 years. More than 1000 such publications have appeared in peer-reviewed journals, and the number would be much larger if symposia or reports on heterotrophs themselves were to be included (

  Heal et al ., 1997

  ). Improved understanding of the decomposition process has accompanied the refinement of methods and conceptual models. The litterbag technique (Bocock and Gilbert, 1957 ; Shanks and Olson, 1961 ; Edwards and Heath, 1962; Crossley and Hoglund, 1962 ) has become a major tool in these studies, despite its limitations (

  Heal et al ., 1997

  ). Radioactive tracers (Olson and Crossley, 1962) have been replaced by methods using stable isotopes of carbon and nitrogen (Nadelhoffer and Raich, 1992 ; Boutton and Yamasaki, 1996 ). Early models of mass loss (Jenny, 1941 ; Olson, 1963 ) defining a decomposition constant, k , are being supplanted by more sophisticated models that consider different constituents of litter (Jenkinson et al ., 1987; Parton et al ., 1994; Sinsabaugh and Moorhead, 1997

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  Biogeography

  A Study of Plants in the Ecosphere

  • Joy Tivy(Author)
  • 2018(Publication Date)
  • Routledge

    (Publisher)

  c . 70–90 per cent of their ingested food to the substratum where it is rapidly decomposed by micro-organisms. As a result termite nests can form virtually closed nutrient systems in which unhealthy and dead individuals are consumed in the nest and losses by predation and breeding flights are relatively small.

    DECOMPOSITION PROCESSES Organic decomposition involves three basic processes (Mason 1977):

  1. The rapid leaching of soluble products either from the foliage or the decomposing detritus;

  2. Mechanical breakdown of DOM by freezing and thawing, wetting and drying, etc.;

  3. Biological degradation — the maceration (comminution) and ingestion of DOM by meso- and macrofauna and oxidation by microbial respiration.

  The main temporal and spatial stages in this process are illustrated in Fig. 7.3 .

  Once mechanical and/or biological degradation is initiated, leaching from, and rapid microbial invasion of, exposed cells proceeds rapidly. Enzymatic secretions accelerate the process, particularly the breakdown of carbohydrates. As a result the C : N ratio of the organic matter decreases. This stimulates the proliferation of the microbial decomposers and soil fauna. Decomposition, however, involves not only the breakdown of organic material but the synthesis of new animal and microbial tissues. The latter, in time, constitutes an increasing proportion of the soil organic matter (SOM) and may prove as, or more, resistant to degradation than the original detritus (DOM). This is the result of two processes:

  1. Mineralisation (or oxidation) of organic compounds during microbial respiration;

  2. Immobilisation or remineralisation , i.e. assimilation of the inorganic nutrients released into new microbial tissues (see Fig. 7.4

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  Environmental Impacts Of Land Use In Rural Regions: The Development, Validation And Application Of Model Tools For Management And Policy Analysis

  The Development, Validation and Application of Model Tools for Management and Policy Analysis

  • Piet Groenendijk, Joop G Kroes, Peter Emile Rijtema(Authors)
  • 1999(Publication Date)
  • ICP

    (Publisher)

  CHAPTER 5 BIO-CHEMICAL PROCESSES Many compounds when present in the soil are subject to conversion reactions of a bio-logical and especially microbiological nature. This is so for specific materials like organic chemicals, but also for organic materials of natural origin, which are added to the soil, e.g. as manure, falling foliage and remaining rests of harvests. Conversion of such organic materials into smaller compounds is strongly enhanced by the activity of micro-organisms. These micro-organisms use the organic materials both for energy supply and assimilation. A special group of degradation reactions involves Decay chains in which solutes are subject to sequential or consecutive degradation reactions. Problems of solute transport involving sequential degradation reactions frequently occur in soil and groundwater systems. Biological conversion reactions constitute the main processes for disappearance of organic compounds from the soil system. The first step in the decomposition process, with big molecules like cellulose, hemicellulose, pectin and lignin, is the decomposition of these big molecules into smaller compounds. Micro-organisms use exo-enzymes, operating outside the organism, to perform this task. The oxidation starts with the formation of peroxides, primary alcohols and mono-carboxylic acids. Generally spoken, the smaller the compounds formed the better their solubility is. The smaller molecules can be taken up by the micro-organisms to be decomposed finally to C0 2 . In particular for oil components, halogenated hydrocarbons and pesticides, the intermediate products must be considered separately because these products may play an important role in groundwater pollution, with regard to taste and toxic effects.

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  eBook - ePub

  Biomolecular Archaeology

  An Introduction

  • T. A. Brown, Keri Brown(Authors)
  • 2011(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Those biomolecules that survive the initial, rapid degradative activity occurring during autolysis have the chance of being preserved in the archaeological record. They then become subject to the slower but nonetheless incessant Decay promoted by environmental factors, both chemical and physical. The chemical factors are primarily water and oxygen, both of which are highly reactive compounds participating in, respectively, hydrolytic and oxidative reactions. It is also possible that chemicals released by Decay of one biomolecule can react with and promote the breakdown of a second type of biomolecule. The physical factors include the various forms of radiation – cosmic, ultraviolet, and geological – which have a significant impact on the integrity of some biomolecules in living cells, and equally important effects after death. Heat is also an important physical factor that influences biomolecular Decay, not by initiating its own specific chemical reactions but by increasing the rate of the reactions promoted by all the other factors. The relative impacts of these different chemical and physical factors on the overall Decay of the biomolecules in a specimen will depend on the nature of that specimen and the environmental conditions to which it is exposed. Desiccated remains, for example, might be expected to suffer less from hydrolytic attack, ones buried in an anoxic environment will be less subject to oxidative reactions, and specimens in permafrost should undergo relatively slow biomolecular Decay due to the low temperature.

  Microbial activity can be looked on as a special type of environmental factor. We have already learnt about the important impact that bacteria and fungi have on the overall diagenesis of bones and other bioarchaeological specimens (Chapter 7 ). Microorganisms are initially attracted by the organic material within biological remains, which provide a source of energy and nutrients. To utilize this material, a microbe must be able to secrete one or more enzymes able to break down the biomolecule into smaller units that can be absorbed. These enzymes are similar to those that are released by the cell itself during autolysis, and have the same effect, although much more slowly. The overall impact that microbial attack has on the biomolecular content of an archaeological specimen depends on the nature of the microflora in the environment in which the specimen in buried. Microbes that secrete extracellular nucleases and/or lipases are relatively common in the biosphere, but ones able to digest other biomolecules such as collagen and keratin are much rarer.

  8.1.2 There are limitations to the approaches available for studying degradation

  There are two ways of studying the degradation pathways of an ancient biomolecule. The first is to carry out experiments in the laboratory, using standard chemistry procedures, and through these to identify the effects of hydrolysis, oxidation, and other known factors, chemical and physical, on the breakdown of the molecule. This approach has two major strengths. First, because it follows the principles of experimental chemistry the resulting information is precise and can be made very detailed. Second, rate constants can be determined for each of the various reactions that contribute to Decay, enabling the length of time that the biomolecule can survive in the archaeological record to be predicted.

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  eBook - ePub

  Building Mycology

  Management of Decay and Health in Buildings

  • Dr Jagjit Singh, Jagjit Singh, Dr Jagjit Singh, Jagjit Singh(Authors)
  • 2006(Publication Date)
  • Taylor & Francis

    (Publisher)

  Detection and biocontrol of wood Decayorganisms

  8

  John W.Palfreyman and Alan Bruce

  INTRODUCTION

  In this chapter current developments in research in two specific areas related to the biology of timber Decay are discussed, namely the use of molecular methods for organism identification and the use of biological control systems as an alternative to currently used chemical preservatives.

  DETECTION AND BIOCONTROL OF WOOD Decay ORGANISMS

  Increasing restrictions on the use of toxic chemicals to preserve timber resulting from both recent legislation and consumer awareness are likely to enhance the need for the development of a more targeted approach to problems associated with timber Decay. Fortunately this need comes at a time when a wide range of new and developing technologies can be applied to the problem. Examples of such technologies include environmental monitoring systems, information handling systems and certain aspects of biology/biotechnology. Increased economic interest in the biological characteristics of some wood Decay organisms able to biodegrade certain toxic waste products, together with legislative and consumer pressures on related (though more advanced) fields such as plant pathology, will indirectly aid developmental research into more appropriate methods for the preservation and treatment of timber.

  Building Mycology. Edited by Jagjit Singh. Published in 1994 by Chapman & Hall, London.ISBN 0 419 19020 1

  MOLECULAR ANALYSES AND THEIR APPLICATION TO WOOD Decay FUNGI

  INTRODUCTION

  Over the last 20 years most areas of biological research have been affected by the introduction of new techniques in molecular biology. These techniques have allowed many new types of analysis to be undertaken and have had a major impact on our understanding of all types of biological process. The impact of such techniques in mycology, and in particular in the identification and detection of wood Decay fungi of economic importance, forms the basis of this review. Whilst it may be considered that current technologies for identification and detection are adequate, various types of evidence indicate that this is not the case. For example, problems have occurred concerning the actual identification of specific organisms (Vigrow et al

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