Introduction
The diet of many people is supplemented with food items preserved by special method and available in a variety of conditions and stages of preparation. Such food may be frozen, canned or dehydrated; it may be partly or completely baked or pre-cooked, ready for heating and serving.
Ezeama (2007) stated that during preparation, packaging or storage, heterotrophic microorganism can attack thesefoodsand prevent them from meeting their nutritional requirement. The unrestricted growth and multiplication of these microorganisms in food may render it unfit for consumption and can result in spoilage or deterioration.
Definition of food
According to Ariaye (2015), food can be defined as any liquid or solid substance which when ingested, digested and absorbed into the body helps to nourish, gives energy and growth, regulate and protect the body from diseases and infections that enable the body to function properly.
Definition of food spoilage
According to Araye(2015),food spoilage occurs when the original nutritive value texture, colour, flavour of the food are damaged, due to the activities or action of microorganism, insects and enzymes which become harmful and unsuitable to eat.
Goreshine (2010) defined food spoilage as the undesirable change occurring in food due to the influence of air, light, moisture, which fosters the growth of microorganism. According to him, food takes different period of time to lose their natural form through spoilage. In context of food preservation, foods are classified as perishable (meat, fish, milk, fruit and some vegetable), semi perishable (eggs, onions, potatoes, carrot, beans) and non-perishable (cereals, pulse, nuts).
Jeanroy and Ward (2008) stated that the rate of food spoilage is depended of the categories which the food belongs.In furtherance they stated that perishable foods are easier to get spoiled, followed by semi-perishable food. The last category of foods likely to get spoilt under the same conditions is the non-perishable foods.
Types of food spoilage
According to Tricket (2009), food spoilage can be classified in three major types which are:
- Putrefaction
- Fermentation
- Rancidity
Putrefaction
This is the decomposition of organic matter particularly the anaerobic (absence of oxygen) breakdown of protein by bacteria, with the production of foul smelling compound. The decomposition of complex nitrogen containing organic compound (primarily protein) caused by the action of putrefaction microorganism. Because putrefaction is accompanied primarily by the evolution of gaseous ammonia, putrefaction is also called ammonifaction and the microorganism involved in the process are called ammonifiers (Tricket, 2009).
Fermentation
This refers to the breakdown of carbohydrate with the fermentation of acid (lactic), alcohol, carbon dioxide by the action of specific enzymes called ferments, produce by minute organism such as mould, bacteria and yeast. For example, lactase ferment produced by bacteria usually found in milk cause the milk to sour by changing lactose (milk sugar) into lactic acid (Tricket, 2009).
Rancidity
This is the chemical decomposition of fats and oil which result in the production of unpleasant odour and flavours. Tricket (2009) classified rancidity into hydrolytic, oxidative and microbial rancidity.
- Hydrolytic rancidity occurs when triglycerides go through the process of hydrolysis, breaking them down into their fatty acid and glycerol.
- Oxidative rancidity is caused by oxidation in unsaturated oil or fats. When these types of oil or fats are exposed to oxidation, they begin decomposing into short chain fatty acid such as bulyric acid which give the fats a rancid taste
- Microbial rancidity is caused by bacteria breaking down fat with enzymes causing the fat to decompose.
Causes of food spoilage
Different conditions can lead to spoilage of food, notably among these according to Dainty (2011) are:
- Growth and activities of microorganism
- Activities of enzymes
- Action of insect and pest
- Purely chemical reaction
- Mechanical damage
Growth and activities of microorganism
This is brought about as a result of the development and biochemical activities of microorganism. The microorganisms responsible for food spoilage are mould, yeast and bacteria.
- Mould: Moulds are in the form of threads developed on perishable foods and are easily visible to the eyes. They contain spore which can spread through the air and start new mould plants. When these moulds find a favourable environment, they germinate and produce a puffy growth, often white or grey but sometimes bluish–green, red, orange or some other colour depending on the variety of the mould (Dainty, 2011).
- Yeast: Yeasts are tiny organism which are not visible to the naked eyes, but which can be seen through the microscope. They multiply very fast and cause fermentation by acting on certain components of the perishable food like fruit juice, syrups etc.; during yeast fermentation, the sugar present in the food are broken up to form alcohol and carbon dioxide. Foods liable to be spoiled by yeast are fruit juice, syrups, molasses, honey, jams and jellies (Dainty, 2011).
- Bacteria: Bacteria are unicellular organism and are much smaller in size than either yeast or mould. They occur in different size than either yeast or mould. They occur in different sizes and shapes and are classified as coccus (spheroidal), bacilli (cylindrical) or spirilae (spirilla) on the basis of their shape as seen under the microscope. They are also in their requirement for food, moisture, acidity, temperature and oxygen. Bacteria can grow and develop rapidly between and 53o Bacteria are classified according to the temperature ranges that they need for growth. We have mesophile with the temperature between 20oC – 37oC, the psychophile with the temperature between 0oC – 20oC (Dainty, 2011).
Activities of enzymes
Enzymes are biological catalyst which speeds up the rate of specific chemical reaction without undergoing changes at the end of the reaction. The life of every living cell depends upon the chemical reaction. Enzymes in a tomato help it to ripen and enzymes produce by the tomatoes, if not slow down or stop may cause the tomatoes to over ripe and lead to spoilage (Dainty, 2011).
Action of insect and pest
Insect like weevil, bugs, fruit flies, moth cause extensive damage to food and reduce its nutritional value and make it unfit for human consumption (Dainty, 2011).
Mechanical damage
During the harvest and transport they can sustain injuring and this lead to entrance of microorganism which cause food spoilage (Dainty, 2011).
Purely chemical reaction
These are reaction not catalyzed by enzymes. Non enzymes bowing or mallard reaction is of importance in food manufacturing and its result can either be desirable or undesirable. The brown discoloration of evaporated and sterilized milk and oxidative, acidity of fat are undesirable (Dainty, 2011).
Characteristics of spoilt food
Characteristics of food spoilage may include an appearance different from the food in its fresh form. Such characteristics according to Tull (2007) are:
- Change in appearance
- Change in texture
- Change in taste and odour
Change in appearance
When food spoilage occurs the food there is a general change in appearance of the food due to microbial growth (mycelia or colonies on surface development of cloudiness in liquids) or changes in food colour due to heme or chlorophyll breakdown (colony pigments, growth of mycelia, etc.) (Tull, 2007)
Change in texture
There is a general change in the texture of food which had undergone spoilage as a result of slime formation (primarily due to surface accumulation of microbial cells or manifestation of tissue degradation) or tissue softening due to enzymatic degradation (e.g. soft rot in vegetables) (Tull, 2007).
Change in taste and odour
Changes in taste and odour occur in spoilt food due to the development of nitrogenous compounds (ammonia, amines, etc.), sulphides ororganic acids (Tull, 2007).
Health implications of consuming spoilt food
When food spoilage occurs, food may be contaminated by different microorganisms or by chemicals that can cause health problems for anyone who eats it. Some of the most common health implications of food spoilage according to Baranyi and Tamplin(2014) are shown in the table below:
| Organism causing food spoilage | Common Name of Illness | Onset Time After Ingesting | Signs & Symptoms | Duration | Food Sources |
| Bacillus cereus | B. cereus food poisoning | 10-16 hrs | Abdominal cramps, watery diarrhea, nausea | 24-48 hours | Meats, stews, gravies, vanilla sauce |
| Campylobacter jejuni | Campylobacteriosis | 2-5 days | Diarrhea, cramps, fever, and vomiting; diarrhea may be bloody | 2-10 days | Raw and undercooked poultry, unpasteurized milk,contaminated water |
| Clostridium botulinum | Botulism | 12-72 hours | Vomiting, diarrhea, blurred vision, double vision, difficulty in swallowing, muscle weakness. Can result in respiratory failure and death | Variable | Improperly canned foods, especially home-canned vegetables, fermented fish, baked potatoes in aluminum foil |
| Clostridium perfringens | Perfringens food poisoning | 8–16 hours | Intense abdominal cramps, watery diarrhea | Usually 24 hours | Meats, poultry, gravy, dried or precooked foods, time and/or temperature-abused foods |
| Cryptosporidium | Intestinal cryptosporidiosis | 2-10 days | Diarrhea (usually watery), stomach cramps, upset stomach, slight fever | May be remitting and relapsing over weeks to months | Uncooked food or food contaminated by an ill food handler after cooking, contaminated drinking water |
| Cyclospora cayetanensis | Cyclosporiasis | 1-14 days, usually at least 1 week | Diarrhea (usually watery), loss of appetite, substantial loss of weight, stomach cramps, nausea, vomiting, fatigue | May be remitting and relapsing over weeks to months | Various types of fresh produce (imported berries, lettuce, basil) |
| E. coli (Escherichia coli) producing toxin | E. coli infection (common cause of “travelers’ diarrhea”) | 1-3 days | Watery diarrhea, abdominal cramps, some vomiting | 3-7 or more days | Water or food contaminated with human feces |
| E. coli O157:H7 | Hemorrhagic colitis or E. coliO157:H7 infection | 1-8 days | Severe (often bloody) diarrhea, abdominal pain and vomiting. Usually, little or no fever is present. More common in children 4 years or younger. Can lead to kidney failure. | 5-10 days | Undercooked beef (especially hamburger), unpasteurized milk and juice, raw fruits and vegetables (e.g. sprouts), and contaminated water |
| Hepatitis A | Hepatitis | 28 days average (15-50 days) | Diarrhea, dark urine, jaundice, and flu-like symptoms, i.e., fever, headache, nausea, and abdominal pain | Variable, 2 weeks-3 months | Raw produce, contaminated drinking water, uncooked foods and cooked foods that are not reheated after contact with an infected food handler; shellfish from contaminated waters |
| Listeria monocytogenes | Listeriosis | 9-48 hrs for gastro-intestinal symptoms, 2-6 weeks for invasive disease | Fever, muscle aches, and nausea or diarrhea. Pregnant women may have mild flu-like illness, and infection can lead to premature delivery or stillbirth. The elderly or immunocompromised patients may develop bacteremia or meningitis. | Variable | Unpasteurized milk, soft cheeses made with unpasteurized milk, ready-to-eat deli meats |
| Noroviruses | Variously called viral gastroenteritis, winter diarrhea, acute non- bacterial gastroenteritis, food poisoning, and food infection | 12-48 hrs | Nausea, vomiting, abdominal cramping, diarrhea, fever, headache. Diarrhea is more prevalent in adults, vomiting more common in children. | 12-60 hrs | Raw produce, contaminated drinking water, uncooked foods and cooked foods that are not reheated after contact with an infected food handler; shellfish from contaminated waters |
| Salmonella | Salmonellosis | 6-48 hours | Diarrhea, fever, abdominal cramps, vomiting | 4-7 days | Eggs, poultry, meat, unpateurized milk or juice, cheese, contaminated raw fruits and vegetables |
| Shigella | Shigellosis or Bacillary dysentery | 4-7 days | Abdominal cramps, fever, and diarrhea. Stools may contain blood and mucus. | 24-48 hrs | Raw produce, contaminated drinking water, uncooked foods and cooked foods that are not reheated after contact with an infected food handler |
| Staphylococcus aureus | Staphylococcal food poisoning | 1-6 hours | Sudden onset of severe nausea and vomiting. Abdominal cramps. Diarrhea and fever may be present. | 24-48 hours | Unrefrigerated or improperly refrigerated meats, potato and egg salads, cream pastries |
| Vibrio parahaemolyticus | V. parahaemolyticus infection | 4-96 hours | Watery (occasionally bloody) diarrhea, abdominal cramps, nausea, vomiting, fever | 2-5 days | Undercooked or raw seafood, such as shellfish |
| Vibrio vulnificus | V. vulnificus infection | 1-7 days | Vomiting, diarrhea, abdominal pain, bloodborne infection. Fever, bleeding within the skin, ulcers requiring surgical removal. Can be fatal to persons with liver disease or weakened immune systems. | 2-8 days | Undercooked or raw seafood, such as shellfish (especially oysters) |
Wholesome food preservation techniques
To ensure the storage of foods in a condition to prevent or minimize spoilage, Alfaro, Nuin, Pin and Le-Marc (2008) recommended the following wholesome food preservation techniques:
- Drying and dehydration
- Use of preservatives
- Heat treatment
- Irradiation
- Cold treatment
Drying and dehydration
The term drying and dehydration arte applied to the removal of water from food. To the food technologist, drying refers to natural desiccation such as by spreading fruit on track in the sun. Removal of water causes of food spoilage. Microorganisms cannot grow and most chemical reactions are greatly deterred. Dehydration is defined as the application of heat under control conditions to remove majority of the water normally present in foods. The main purpose of dehydration is to extend the shelf life of the food by reduction in water activity. These inhibit microbial growth and enzyme activity but the processing temperature is usually insufficient to cause their inactivation (Alfaro et al., 2008).
Use of preservatives
Preservatives have been defined as any chemical which when added to a food tends to prevents or retard its deterioration. They are used to control spoilage microorganisms or chemical deteriorative processes or insect and rodent attacks. Chemical preservatives must be safe for consumption and not carcinogenic, example of such chemicals are sodium benzoate, ascorbic acid, sodium and calcium propionate (Alfaro et al., 2008).
Heat treatment
Preservation of food by heat destroys most spoilage microorganism and natural enzymes present in the food. There are various ways of heat treatment which include bleaching, sterilization and pasteurization (Alfaro et al., 2008).
Irradiation
Irradiation is the process by which energy in form of light or heat is emitted from molecules and atoms as a result of internal changes. Radiation substances exist in nature but they can artificially induce. Certain electromagnetic radiation destroys microorganism and food enzymes (Alfaro et al., 2008).
Cold Treatment
Low temperature preserves food by retarding chemical reactions, enzymatic action and growth and activity of microorganism. The use of low temperature below freezing and generally stops at freezing temperature are: chilling, freezing and refrigeration (Alfaro et al., 2008).
Conclusion
In conclusion, spoiled food cannot be rectified by any processing method. It results in wastage and food poisoning when consumed. To prevent spoilage and ultimately wastage, any surplus food should be processed and preserved immediately.
References
Araye, F. (2015).Lecture note on Food Science and Commodities.Ughelli: Delta State College of Health Technology, Ofuoma-Ughelli (Unpublished).
Alfaro, B., Nuin, M., Pin, C., Le Marc, Y. (2008). Application of “Fish shelf-life prediction (FSLP) software for monitoring seafood quality in the cold chain.Proceeding of 3rd International Workshop, at Institute of Animal Sciences, Bonn 16-18th December, 2008
Baranyi, J., Tamplin, M. (2014).ComBase: A common database on microbial responses to food environments. J. Food Prot.,67 (9), 1967-1971.
Dainty, R. H. (2011).The control and evaluation of spoilage.Journal of Food Technology (6):209-224.
Ezeama, C. F. (2007). Food microbiology fundamentals and applications.Lagos: Natural Prints Ltd.
Goreshine, H. E. (2010). Food spoilage and deterioration.In F.C. Blanck (ed), Handbook of food spoilage and agriculture. New York: Reinhold Publishing Corporation.
Jeanroy, A. & Ward, K. (2008).Canning & preserving for dummies.Queensland: Valory Inc.
Tricket, J. (2009). The prevention of food poisoning.New York: Sage Publication.
Tull, A. (2007).Food and nutrition (3rd ed.), Oxford: Oxford University Press.
