Why is spoilage of protein foods particularly bad

The microorganisms break down the fats in butter to produce glycerol and acids, both of which are responsible for the smell and taste of rancid butter. Another example occurs in meat , which is primarily protein. Bacteria able to digest protein proteolytic bacteria break down the protein in meat and release odoriferous products such as putrescine and cadaverine.

Chemical products such as these result from the incomplete utilization of the amino acids in the protein. Food spoilage can also result in a sour taste. If milk is kept too long, for example, it will sour. In this case, bacteria that have survived pasteurization grow in the milk and produce acid from the carbohydrate lactose in it. The spoilage will occur more rapidly if the milk is held at room temperature than if refrigerated. The sour taste is due to the presence of lactic acid, acetic acid, butyric acid, and other food acids.

Sources of microorganisms. The general sources of food spoilage microorganisms are the air, soil, sewage, and animal wastes. Microorganisms clinging to foods grown in the ground are potential spoilers of the food. Meats and fish products are contaminated by bacteria from the animal's internal organs, skin, and feet. Meat is rapidly contaminated when it is ground for hamburger or sausage because the bacteria normally present on the outside of the meat move into the chopped meat where there are many air pockets and a rich supply of moisture.

The bacteria that cause infections in humans are known as pathogens. As all bacteria thrive in similar conditions, it is important to avoid conditions which favour their growth in order to prevent infection.

They are active over a wide range of temperatures. Some like warmth and are active at 75oC. Others like cold conditions and grow at temperatures as low as 5oC. This may cause problems in storage of foods. Some bacteria can form resting bodies called spores to protect them when the conditions are unfavourable for normal growth, for example the wrong degree of acidity or alkalinity, temperature or lack of moisture. Although normal bacteria are destroyed during heat treatment by boiling, some spores survive boiling for hours.

They can resume normal activity when conditions become more favourable and contaminate some preserved foods.

Bacteria are lalled in an acid medium, and therefore they are not a problem in preserving fruits and making jams. The pasteurization of milk does not destroy all bacteria in milk but does destroy those bacteria likely to cause disease.

Freezer temperatures must be low enough to prevent bacteria activity during storage. Although some bacteria die in the freezer, some remain inactive in the food and start to grow again when the food thaus.

The removal of moist are by drying or by addition of large quantities of sugar and salt make conditions unsuitable for bacteria, and these methods are therefore use in food preservation. See unit They go putrified when they are contaminated. This is the situation where protein foods rot, and produce very bad smell. They go rancid. This is the condition where food containing fats and oils begin to smell and tasted bad when they are old. Cooked cereals become marshy and slimy when affected by micro-organisms.

This condition is known as serenasis. Flour products smell and taste unpleasant when they are spoilt. They are described as being stale. Jump to: navigation , search. Navigation menu Personal tools Log in Request account. Namespaces Page Discussion. Views Read View source View history.

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Just leave the above mentioned food items on the kitchen shelf for about three to five days and observe what happens to them. You will realize that their appearance, smell and taste have changed. Some of them will be covered with a whitish substance, others some orange powdery substance and some also will smell very badly.

All these signs indicate that these foods are not wholesome since they are contaminated. It relies on specialized energy-intensive industrial—technological processes to preserve and store food and to transport it from producer to consumer. Some of the losses are due to inefficient harvesting, and some are due to the disposal of perfectly edible food, but a substantial proportion is due to spoilage because of inadequate preservation, storage, and transport.

Many writers have left the impression that wastage can be reduced to near zero Kantor et al. There will always be substantial spoilage and wastage, in large part because we will never completely win the battle with our competitors.

Substantial quantities of food are lost because of consumption and spoilage by rodents and insects, but we have focused here on bacteria and fungi, which cause most of the spoilage Ruxton et al. Both humans and microbes are subject to the Malthusian—Darwinian dynamic: the universal tendency of all organisms to push against the limits and grow exponentially in population Nekola et al.

The result is an evolutionary arms race, with each party continually seeking any advantage Janzen , Ruxton et al. In this case, it is mostly a race between the capacity of microbe populations to grow on human foodstuffs and evolve adaptations to changing conditions and the capacity of humans to come up with new technologies for preserving, storing, and transporting food.

Although less heralded than the evolution of antibiotic resistance in microbial pathogens, food-spoiling microbes rapidly evolve adaptations to resist new preservation technologies so as to colonize and grow on foodstuffs Bower and Daeschel Although we briefly mentioned preservation technologies that fundamentally alter the thermodynamic, kinetic, or stoichiometric properties of food, given the enormous natural variety, adaptability, and rapid generation time of many microbes, it will be impossible to completely defeat the ones that cause food spoilage, just as it will be impossible to eliminate all disease.

The ecology of the food-supply system outlined above has major implications for food security and sustainability. As the demographic transition continues and cities grow, their ecological footprint increases.

An increasing food shadow means that food must be preserved for greater transport distances and longer travel times, leading to even greater preservation challenges. The trade-off between speed and energetic efficiency of transport means that reducing travel time by increasing speed—by airplane rather than rail, truck, or ship—is possible, but only by expending increasingly costly energy.

Keeping food cold by refrigeration or freezing during transport retards spoilage but requires continual energy expenditure to run the compressors in refrigerated transport vehicles. These densely populated tropical cities in developing countries have food security issues not experienced by similar-sized cities in the middle and high latitudes: Higher ambient temperatures and higher humidity in the tropics mean that foods spoil more rapidly without preservation and that more energy must be expended to maintain a set refrigeration temperature.

The greater poverty of the developing world increases the challenges of paying higher food prices, in large part because of increasing energy costs for storage and transport. Although tropical cities in developing countries may be especially vulnerable, even the most developed countries, such as the United States, also face serious issues of food security Godfray et al. After dropping during the last century because of cheap fossil fuels and advances in mechanization, global food prices have increased rapidly since FAO , correlated with increasing oil prices USEI These trends are likely to continue as energy-dense fossil fuels are depleted and renewables are unable to compensate.

Spatial and temporal fluctuations in food supply will continue to threaten food security. With the inevitable depletion of fossil-fuel reserves and increasing energy costs, major changes in food-supply systems will be required to sustain current populations, levels of economic prosperity, and quality of life.

In areas of favorable climate and fertile soils, farms and small villages should be able to feed themselves cheaply and efficiently from local food production, making the local-food movement a trend of necessity rather than choice.

The greatest gains in food preservation and transportation have allowed us to move food items across the globe before spoilage but have focused on increasing the geographic extent of food networks, ignoring the energetic cost. To diminish the impacts of future spatial and temporal fluctuations of food supply, more research is needed to increase the fuel efficiency of our current storage and transportation technologies and to motivate novel innovations that move storage and food-transportation technologies away from fossil fuels and toward more sustainable regional and global food networks.

Over historical time, humans have used advances in storage and transportation technologies to increase the geographic extent of food networks.

In hunter—gatherer cultures, these technologies have largely been used to buffer against the temporal variation in food supply. With the advent of agriculture, storage and transportation allowed for growing cities to be supported by regional food producers. In our modern industrial—technological society, continued technological advances and increasing fossil fuel energy inputs allow for a truly global food network: Even fresh seafood can be transported between continents.

Hammond and James H. Joseph R. Burger and Trevor S. Tatiana P. Flanagan is supported by a James S. Chang for their enthusiastic and insightful conversations and to Clair Terni, Amy Wilson, and Adam Fletcher for their honest thoughts on the anthropological, historical, and economic aspects of this article.

The supplemental material is available online at Supplementary Data. Archer DL. Freezing: An underutilized food safety technology? International Journal of Food Microbiology 90 Google Scholar. Bailey GN. Concepts of resource exploitation: Continuity and discontinuity in palaeoeconomy World Archaeology 13 1 Barnosky AD et al. Approaching a state shift in Earth's biosphere Nature 52 Beaubien J.

National Public Radio 22 May ; www. Google Preview. Burger JR et al. The macroecology of sustainability PLoS Biology Featherstone S A review of development in and challenges of thermal processing over the past years: A tribute to Nicolas Appert Food Research International 47 Foley JA.

Can we feed the world and sustain the planet? Scientific American 60 Gerland P et al. World population stabilization unlikely this century Science Hinrichs CC Regionalizing food security?

Specific power required for propulsion of vehicles Mechanical Engineering 72 Lieberson AD How long can a person survive without food? Scientific American 22 May ; www. Nekola JC et al. The Malthusian—Darwinian dynamic and the trajectory of civilization Trends in Ecology and Evolution 28 Notteboom T Carriou P Fuel surcharge practices of container shipping lines: Is it about cost recovery or revenue making?

Notteboom TE Vernimmen B The effect of high fuel costs on liner service configuration in container shipping Journal of Transport Geography 17 Peel M. Hunger strikes: Understanding the underlying physiology will help doctors provide proper advice British Medical Journal Reif-Acherman S The early ice making systems in the nineteenth century International Journal of Refrigeration 35 Oxford University Press is a department of the University of Oxford.

It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Sign In. Advanced Search. Search Menu. Article Navigation. Close mobile search navigation Article Navigation. Volume Article Contents Abstract.

Spoilage, preservation, and storage. Implications for food security and sustainability. Supplemental material. References cited. Hammond , Sean T. Hammond seant. James H. Fristoe, and Jeffrey C. Jordan G. Oxford Academic. Trevor S. Norman Mercado-Silva. Jeffrey C. Cite Cite Sean T. Select Format Select format. Permissions Icon Permissions. Abstract Human societies have always faced temporal and spatial fluctuations in food availability.