Chemicals Used For Microbial Preservation Of Foods Biology Essay


Food preservation is a process by which food stuffs are prevented from getting spoilt for a long period of time. The taste, color, and nutritive value of food are also preserved. One of the most important reasons for preserving foods is to take care of the excess produce and to make transportation and storage easier. Food is said to be spoilt if there is rotting, bad smell, mold, fermentation, spongy growth on food stuff, or formation of white or brown spots on vegetables and fruits (Manas & Pagan, 2005). Foods get spoilt mainly due to presence of micro organisms, enzymes (present in food), insects, worms, and rats. The principle of food preservation entails a good method that slows down or prevents altogether the action of the agents of spoilage. In addition, the method chosen should not damage the foods. Food is preserved at home using the following methods namely; dehydration, lowering temperature, increasing temperature, drying, and using natural preservatives such as salt, sugar, lemon, vinegar, oil, and sugar (Lewis, 1989; Nakatani, Inatani, Ohta, & Nishioka, 1986).

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A food preservative is any substance that is added to foods to make it last for a longer time. As mentioned in the last paragraph, a preservative can be natural, and also chemical. Examples of chemical preservatives include, potassium metabisulphate, citric acid, sodium benzoate, nitrite, sulphur dioxide, organic acids (sorbic, benzoic, etc), chlorine compounds some of which will be discussed in details.

Nitrite (NO2-)

Sodium nitrite is the active curing ingredient used for meat preservation. It is a highly reactive chemical that reacts with meat to produce nitric oxide (NO) which replaces the oxygen atom in the meat pigment structure (heme group) yield the typical cured pink color that is observed when meat is heated. They function to keep meat from turning brown, and to prevent toxic bacteria that causes food poisoning from developing (Cammack, et al., 1999). Nitrite also functions for meat flavor, helps provide microbial stability and acts as a potent antioxidant. Nitrite is highly reactive and toxic and it is usually combined with a portion of the salt prior to meat addition. Nitrite was evaluated and recommended for daily intake in 1961 and 1964 by the Joint FAO/WHO Expert committee on Food Additives. Absorption of nitrite leads to conversion of haemoglobin to methaemoglobin. Fortunately, there is no controversy concerning the ratios involved in this reaction (Roberts & Greenwood, 2002).

Sulphur dioxide

Typically, pathogenic yeasts and bacteria do not seem to survive in wine due to high levels of alchol and low pH media. However, some bacteria and yeast can spoil a wine so that it is no longer pleasant for consumption. Sulphur dioxide and sorbic acid are commonly used in wine industry to prevent spoilage and prolong shelf life of wine. SO2 blocks the growth of bacteria by disrupting the normal functioning of their cell. Sulphur dioxide is an antioxidant and antimicrobial agent. To prevent bacterial spoilage in sweet wines it is important to add a sufficient amount of sulfur dioxide in addition to sorbic acid. In addition, SO2 is used in dried fruit, dehydrated vegetables, fruit juice, fruit syrup, as well as picklesn (Brul, et al., 2002). Sulphur dioxide has been recommended for human consumption at certain levels. Sulphur Dioxide and Sulfites are bleaches and antioxidants used to stop browning. Sulfites also have limitations in that they destroy vitamin B1, are linked to hyperactivity, and can cause severe reactions--especially in asthmatics. The FDA believes 1 in 100 people are sensitive to sulfite. Sulfites can cause headaches. In 1986, too much sulfites were being used at salad bars, and dozens of people died from anaphylactic shock. The FDA thus banned sulfite use on salad bars. However, in the Food Standards Code, Food Standards Australia New Zealand (FSANZ) states that sulphites can be added to specified food products, at a permitted level up to 500 mg/kg.

Organic acids

Organic acids include preservatives such as sorbic, benzoic and propionic acid and the parabens. Sorbic is a straight-chained monocarboxylic acid whose chemical formula is C6H8O2 and a safe preservatives for cosmetics and personal care products with a pH lower than 6.5. First isolated from the pressed unripened berries of the rowan or mountain ash tree by A. W. Hoffmann, a German chemist, in 1859, its antimicrobial preservative power was discovered 1939 (Tiwari, et al., 2009). Sorbic acid is effective against small populations of common microorganisms in cosmetics (Sheneman & Costilow, 1955). Yeast, molds, and bacteria growth are interrupted by addition of sorbic acid. Sorbates are more effective at higher pH ranges than other organic acids used as preservatives (Piva & Grilli, 2007). For instance, sorbates are effective up to 6.5, whereas benzoates are effective to only 4.5. The European Commission Cosmetic Directive has approved the use of sorbic acid without restrictions or warning labels at levels up to 0.6% (Luck, 1990).

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Benzoic acid is an FDA-approved antimicrobial compound available for food preservation. It has antimicrobial properties and occurs naturally in prunes, greengage plums, apples, ripe cloves, as well as cinnamon. Sodium benzoate is much more preferred to benzoic acid as it is more soluble in water compared to the later. It is effective at low pH below 4.5. The two are used as food preservatives and are most suitable for foods, fruit juices, and soft drinks that are naturally in an acidic pH range. Their use as preservatives in food, beverages, toothpastes, mouthwashes, dentifrices, cosmetics, and pharmaceuticals is regulated. Benzoic Acid is also used as an active ingredient in cough syrup and ointments. Sodium Benzoate is also an active ingredient in many oral medications.Available data in FDA indicate that benzoic acid and sodium benzoate have only a low toxicity potential in the terrestrial environment (Lado & Yousef, 2002).

Propionic acid is used as a rope and mold inhibitors in bread, cheese, fresh dough, puddings, gelatins, jams, and some meat products. It has been approved in the United States as GRAS (Generally Recognized As Safe) substances for food use. Propionic acid is characterized by a pungent, rancid odor and also it is corrosive and flammable; hence safety measure should be adhered while handling this acid. The concentration of propionic acid exceeding 1% will inhibit the growth of molds. The recommended level of propionic acid usage is 0.1 to 0.4 % (Hackett & Gutman, 2005). The Federal regulation act limits the maximum level of bread, flour and rolls at 0.32% based on the weight of the flour.

Parabens are a group of broad-spectrum preservatives used to prevent the growth of harmful micro-organisms especially molds and yeast. They are esters of p-hydroxybenzoic acid, which is a chemical derived from petroleum processing.This type of preservative is derived from benzoic acid. Parabens have been used extensively for over 50 years and have been researched thoroughly. This group of preservatives used in cosmetics, shampoos, skin creams, hair gels and various food product. Parabens have been proven time and time again to be safe ingredients. Parabens are less sensitizing to the skin than most other preservatives used in beauty products around the world. They are low in toxicity (they’re food grade preservatives) and have low potential for irritation. They have a long history of safe use in these products, and have been specifically recognized as safe by the U.S. Food and Drug Administration (Benedict, 2006). Additionally, the Cosmetic Ingredient Review Expert Panel concluded that they were safe for cosmetic use.

Some chlorine compounds are used for disinfection of water as well as ingredient of food. Such a compound is the disinfectant chlorine dioxide. It has been approved by EPA, FDA, FAO, and ministry of health from many countries globally. Commanding features of this compound are free activation, not toxic, efficient and safe to use. It has a unique oxidation feature that enables it to kill various bacteria, fungi, bacteria, and viruses. Stabilized chlorine dioxide also known as sodium chlorite is found in dental care products, and is essential for fighting bacteria in gums. In addition FDA has approved the stabilized form in food processing industry as a sanitizer and also for controlling bacteria and mold.

Food contact surfaces in food processing can include all equipment, utensils and facilities used during processing as well as worker clothing and hands, and packaging materials. It is therefore important to check routinely and chemical test for the safety of food. This is typically accomplished by sanitizers. Acid sanitizers include acid-anionic, carboxylic acid and peroxyacetic acid types. Being acids, they remove inorganic soils, such as hard water mineral scale, while sanitizing.

Hydrogen peroxide, peroxyacetic acid (POAA), octanoic acid, peroxyoctanoic acid (POOA) and 1-hydroxyethylidene-1,1-diphosphonic (HEDP) acid as components of antimicrobial washing treatments recommended by FAO/WHO Expert Committee for Food Additives (JECFA). The recommended use of the components, as aqueous antimicrobial treatments, are for spraying, washing, and rinsing, dipping, chilling, and scalding operations of poultry, meat, fruits and vegetables. Hydrogen peroxide is known to be a very powerful oxidizing agent that is in general effective against a wide spectrum of microorganisms including bacteria, yeasts, molds, viruses and spore-forming organisms (Luck, 1985). They are fast acting even at low temperature and degrade organic soils to environmentally friendly byproducts. The octanoic acid component in the commercial wash treatments has been claimed as major antimicrobial agent at target concentrations of 37-180 ppm (Entis, 2002).

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Consumers are concerned about additives to their food as evidenced by literature. Processed food contain many chemicals that are added to preserve food, add color, enhance flavor and kill insects, fungi, or bacteria. The United States Food and Drug Administration (F.D.A.) have allowed a wide variety of food additives to enter our food supply (Eichholtz, 1954). However, many health practitioners, nutritionists, naturalists, and other health-minded consumers avoid preservatives, additives and other chemical additives.