Food preservation is a growing demand for all parts of the world owing to the increasing human demands for food and the need to utilize the little available food substances. Even though food preservation is as old as humanity and life, advancements to incorporate more effective methods is of crucial importance to the present and future generations alike. Food begins to go bad from the time it is harvested or slaughtered thus the need to preserve it for future consumption needs. Presently, the traditional preservation methods have been replaced by the modern methods which are more efficient and effective compared to their predecessors. Microbial such as bacteria are the main cause of food spoilage. These microbial release certain chemical substances which initiates offensive as well as sensory changes in fresh foods rendering them spoilt (Oladapo, Akinyosoye, & Abiodun, 2013). Spoilt foods can bear serious health effects on the human body leading to illnesses. The illnesses occur as a result of ingestion of harmful pathogens present on the spoilt foods (Nebedum & Obiakor, 2007).
Some microbial that are responsible for foods spoilage include Staphylococcus aureus, Proteus mirabilis, Klebsiella aerogenes, Pseudomonas aeruginosus, etc. Various chemical preservatives have been developed under laboratory conditions to help preserve different kinds of foods. As Abdulmumeen, Ahmed & Agboola (2012) observes, the chemical preservatives are supposed to have certain health friendly characteristics that are friendly to human health and effective in preventing foods from going bad. For instance, the chemicals must be non-toxic, human health friendly, economical, and must not have negative effects on the taste of the foods (Lee, 2004). In correspondence to these mandatory requirements, different chemical preservatives have been made to help in foods preservations of various kinds. This section reviews some of the chemicals used in food preservation to prevent microbial spoilage.
Fruits and vegetables are among food substances considered to be highly susceptible to microbial spoilage. Fruits and vegetables can be contaminated easily by pathogenic microorganisms emanating from various sources. Fruits and vegetables have been preserved since traditional times using the pickling or fermentation processes. Fermentation/ pickling involves increasing the acidic conditions for the fruits and vegetables chemically making them unsuitable for inhabitation by pathogenic microbial (Pal et al. 2015). In pickled foods, the chemicals responsible for food preservation are acids, heating and salt generated when the foods are fermented. However, recent studies such as Omoya & Akharaiyi (2010) established that some microbial have high resistance to the acidic content created due to fermentation. Such include pathogens such as E. coli, and the Salmonella species. As a result, pickling may not be considered safe for such pathogens
Another approach commonly used for foods preservation presently is known as the hurdle technology. The hurdle technology is a conglomeration of several preservation treatment methods (chemical and biological) applied to the same food substance. The method is grounded on the assumption that such combinations have the potential to inactivate the microorganisms compared to using a single method (Brul & Coote, 1999). The chemical constituent of the hurdle technology is believed to stress the microorganisms’ physiological activities responsible for food spoilage such as homeostasis, metabolism, and inflicts stress on the microbes. For instance, Pal et al. (2015) observes that the combined approaches applied in the hurdle technology leads to differential attacks on the physiological processes of the various microorganisms thereby increasing the synergistic effectiveness of the preservation mechanisms used (Elhkim, Heraud, Bemrah, Tanaka & Ogata, 2007). The quality of the preservative using the hurdle technology can be improved by increasing the intensity and character of the chemical preservatives used in the hurdle. However, the hurdle technology is limited to meet products only, a factor that limits its applicability and usefulness.
Hydrogen peroxide is another technologically geared chemical approach that has been used extensively in food preservations, especially to prevent food spoilage caused by bacteria and fungi (Nanda, 2005). The hydrogen peroxide is often combined with thiocyanate to obtain maximum activity. However, this method is majorly active against the microorganisms that produce water. The hydrogen peroxide substance creates an osmo-stressing environment in the bacterial surrounding making it hard for the bacteria to survive. These stressors eventually lead to the death of the food spoiling bacteria hence helping to preserve the food substances. However, Adeleke & Oladapo (2010) observes that in the presence of high concentrations of H2O2, the bacteria are likely to develop resistance to the stressing effect of the H2O2 preservative reducing its effectiveness. Due to this, it is apparently verified that the preservative should be used in low quantities when used alone in order to attain the highest level of effectiveness (Appendini & Hotchkiss, 2002).
Additionally, use of salts such as sodium chloride and sugars have gained increasing prominence in food preservation over the recent past. According to Nanda (2005) observations, both the sodium chloride and sugars have the same mode of action regarding food preservation mechanisms. For instance the salt and sugar compounds become effective preservatives by absorbing the moisture present in the food and on the microorganisms. This inflicts a drying effect not only on the foods being preserved but also on the microorganisms. Consequently, the affected bacteria eventually die leaving the foods fresh and sustainable. The salts and sugars used here can be added to brine before curing or sprinkled on the foods directly. The drying effect helps to prevent the reaction of pathogenic organisms and thus prevent food spoilage (Pal et al. 2015). Application of salts and sugars to foods prevent spoilage by microorganisms by initiating various unfavourable conditions inhibiting microbial survival. For instance, the salts/ sugars cause a high osmotic pressure between the cells thereby leading to cells plasmolysis and consequently the death of the microorganisms. Moreover, the salts/ sugars also dehydrates the microorganism’s bodies leading to their deaths. They also reduce the solubility of water and oxygen into the foods suffocating the microorganisms to death (Handa, 2005).
Another chemical preservative commonly used to preserve meat substances is sodium nitrate (NaNO3) as well as sodium nitrite (NaNO2). These preservatives are used to cure meat substances due to their ability to stabilize the colour of the meat. Also, Pal et al. (2015) observe that these preservatives have the capability to inhibit food spoilage and poisoning by certain bacteria other than promoting the development of flavor in the foods they are used to preserve. The nitric acid produced as a result of the ionization of nitrite is the main active agent that functions to promote the preservative action. Moreover, the nitrite acid often ionizes under acid environments to produce nitrous acid which is also a powerful reducing agent (Sharma & Gautam, 2007). As a result, it induces a serious disruption in the cells metabolism of the microorganisms. It also inhibits the outgrowth of endospores. The nitric oxide, on the other hand, is responsible for maintaining the primary colour of the meat products being preserved (Sharma & Gautam, 2007). In combination, the two preservatives achieve a double conservative effect in meat products (colour preservation and preservation against spoilage).
Other than these methods, other preservation methods that have been utilized technologically recently is jellying which involves preserving the foods by cooking them in chemical substances that solidify to form gels around the food substances. The chemical substances that have been used in the food industry to achieve this effect include gelatin, maize flour, agar, (Sharma, Kappor, & Neopaney, 2006) and other gel forming chemical substances. In jellying, the gel substance formed around the foods creates a coating which prevents entry of microorganisms thus protecting the foods from going bad. Some foods develop the gels automatically upon cooking thus are capable of preserving themselves adequately. Such include eels and elvers which are capable of forming protein gel covering once cooked. The gel cannot be penetrated by the microorganisms responsible for food spoilage. As a result, these foods remain unspoiled for a long time once cooked (Sharma, Kappor, & Neopaney, 2006).
The use of food additives has gained tremendous application in food preservation in developed countries such as the United States. Food additives, as the name suggests includes all kinds of substances added to the foods either directly or indirectly before or after cooking (Mollinos et al. 2005). Food additives vary and exhibit similar characteristics as other food preservatives discussed previously. Some of the food additives used in preservation include antimicrobial agents such as vinegar, salts, calcium propionates, sorbic acids among others. The action of these additives in preventing spoilages vary depending on their chemical compounds and the reaction with the food substances being preserved. For instance, antioxidant additives such as vitamin C acts by preventing oxygen entry into the food substances. This action helps to suffocate the microorganisms responsible for causing food spoilage. They eventually die (Mollinos et al. 2005) leaving the food in stable conditions.
Food preservation is a common factor in the present world as the demand for food, and consequently, their preservation increases across the world. Although food preservation is an old phenomenon in human society, dating back to the advent of man, technological advancements have contributed immensely to promoting food preservation mechanisms used today. Chemical food preservation mechanisms involve the use of chemicals to preserve different kinds of foods. These chemicals must be non-toxic, have no negative impacts on human health and maintain the quality, and flavor of the foods. Different chemical preservatives have been developed for use in food preservation. Such include the use of salts and sugars, chemicals such as acids, food additives, etc. However, different chemical methods are suitable for preserving different kinds of foods and thus must be chosen informatively.
Abdulmumeen, H.A., Ahmed, N.R., & Agboola, R.S., (2012). Food: Its preservatives, additives, and applications. International Journal of Chemical and Biochemical Sciences, 1(2012): 36-47.
Appendini, P. & Hotchkiss J.H. 2002. Review of antimicrobial food packaging. Innovative Food Science Emerging Technology, 3:113–126.
Brul, S. & Coote, P., (1999). Preservative agents in foods Mode of action and microbial resistance mechanisms: Review. International Journal of Food Microbiology, 50(1999): 1–17.
Elhkim, M.O., Heraud, F., Bemrah, N., Tanaka, T., & Ogata, A., (2007). New consideration regarding the risk assessment, intolerance reactions and maximum theoretical daily intake in France. Regulatory Toxicology and Pharmacology, 43(3): 308-16.
Lee, S.Y., (2004). Microbial Safety of Pickled Fruits and Vegetables and Hurdle Technology. Internet Journal of Food Safety, 4, 21-32.
Mollinos, A.C., et al. (2005). Effect of immersion solutions containing enterocin AS-48 on Listeria monocytogenes in vegetable food. Applied Environmental Microbiology, 71: 7781–7787
Nanda, M. (2005). Determination of zone of inhibition. New Delhi: Jaype Brothers Medical Publishers.
Nebedum, J.O. & Obiakor, T. (2007). The effects of different preservation methods on the quality of Nunu, a locally fermented Nigerian dairy product. African Journal of Biotechnology, 6(4): 454-458.
Oladapo, A.S., Akinyosoye, F.A., &Abiodun, O.A., (2013). The inhibitory effect of different chemical food preservatives on the growth of selected food borne pathogenic bacteria. African Journal of Microbiol Research, 1510-1516.
Omoya, F.O.,& Akharaiyi, F.C., (2010). A pasture honey trial for antibiotic potency on some selected pathogenic bacteria. Journal of Natural Products, 3, 5-11.
Pal, M., et al. (2015). The Role of Bacteriosin as Food Preservative. Beverage & Food World, 42(1): 28-33.
Sharma, N., Kappor, G. & Neopaney, B. (2006). Characterization of a new bacteriocin produced from a novel isolated strain of Bacillus lentus NG121. Antonie Van Leeuwenhoek, 89:337–343.
Sharma, N. & Gautam, N. (2007). Use of bacteriocin as potential biopreservative in milk, cheese, and apple juice. Beverage and Food World, 34: 44–47.