Published: 23rd March, 2015 Last Edited: 23rd March, 2015
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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).
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.
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).
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 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).
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 (theyââ‚¬â„¢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).
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.
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We have already studied that spoilage of perishable food materials takes place due to their high moisture content, attack by insects or micro-organisms (such as yeast, mould and bacteria) and by the action of enzymes. The various methods of food preservation are based on either of the following two basic approaches:
(a) According to the first approach, the microorganisms responsible for spoilage are eliminated by some suitable technique. The methods of food preservation, which adopt this approach, are called bactericidal methods. For example, cooking, canning etc.
(b) According to the second approach, conditions are created which are unsuitable for the growth and action of microorganisms and enzymes. These methods of food preservation are known as bacteriostatic methods.
Some examples of the methods are salting, pickling and deep-freezing.
Let us now study some common methods of food preservation.1.Dehydration and Sun-drying
Drying in sun is an old method of preserving food materials such as vegetables, fish and meat. Removal of water from fruits and vegetables is called dehydration. Dehydration results in decrease in their moisture content. Due to reduced moisture content the growth of microorganisms as well enzyme action is retarded and thus they can retain their nutritive value for longer periods.
Dehydration can be carried either by drying fruits and vegetables in the sun or by removing their water under controlled conditions of temperature and humidity. Preserving food materials by drying in the sun is one of the oldest methods. For example, vegetables such as methi leaves, spinach, and cauliflower are generally preserved by sun drying. Peas are preserved by carrying out dehydration under controlled conditions. Dehydration of fish, meat and their products is carried out by a process called smoking. In this process, small pieces of meat are first rubbed with salt and then hung from the ceiling or kept on wooden rafters (sloping beams). A fire is lit below. The pieces of meat get dehydrated with the heat and smoke produced by the fire.2.Preservation by salt and sugar
Preservation of food by adding sufficient amount of salt to it is called salting. It is extensively used in the preservation of raw mango, amla, tamrind (imli), beans, fish and meat. When salt is used in high concentration between 15% to 18%, it drains out water from the food material through osmosis. As a result of removal of water, the bacterial growth in the food material is inhibited and thus the food can be preserved. For carrying out preservation salt is used in dry fro as well as in solution from.
Sugar can also be used for the preservation of food. Bacteria cannot grow in a sugar syrup containing more than 68% sugar because it has very little free moisture available. Thus, food materials such as fruits and vegetables can be prevented from being spoiled by adding large quantities of sugar. The microorganisms already present in the food materials gradually die due to lack of available moisture in the sugar syrup. Many fruits such as apple, pineapple, mango, strawberry and guava are preserved in this way in the form of jams, jellies and murabbas.
In addition to salt and sugar some other substances which are used as preservatives are vinegar, oils, spices and critic acid. These substances are used in pickles, ketchups, jams, squashes etc.3.Deep Freezing
This is a direct method for inactivating enzymes and preventing the bacterial growth. In this method, the food material is cooled below 0`C. At low temperature, enzymes become inactive and bacterial growth is also inhibited. As a result, food material can retain its nutritive value for a longer period. This method of food preservation is used for storing fresh fruits, vegetables, and meat and fish products.4.Chemical Preservation
Growth of microorganisms in a food material can also inhibited by adding certain chemical substances. However, the chemical substance should not be harmful to the human beings. Such chemical substances, which are added to food materials to prevent their spoilage, are known as chemical preservatives. In our country, two chemical preservatives which are permitted for use are:
1. Benzoic acid (or sodium benzoate)
2. Sulphur dioxide (or potassium metabisulphate).
Benzoic acid or its sodium salt, sodium benzoate is commonly used for the preservation of food materials. For the preservation of fruits, fruits juices, squashes and jams sodium benzoate is used as preservative because it is soluble in water and hence easily mixes with the food product. 0.06% to 0.1% concentration of sodium benzoate is sufficient for the preservation of fruit juices and squashes.
Potassium metabisulphite or sodium metasulphite is used for the preservation of colourless food materials such as fruit juices, squashes, apples, liches and raw mango chuntney. These are not used for preserving coloured food materials because sulphur dioxide produced from these chemicals is a bleaching agent. These preservations on reaction with acid of the juice liberate sulphur dioxide which is very effective in killing the harmful micro-organisms present in the food and thus prevents it from getting spoiled.Some other Modern Methods of food Preservation
In addition to the various methods of food preservation described above, there are some modern methods of food preservation such as canning, irradiation, bottling and vacuum drying. All these methods are bacteriasidal methods.1.By irradiation:
Irradiation means exposing to high energy radiations. In this technique of food preservation, the food material is exposed to high energy of radiations such as gamma rays or X-rays. These radiations kill the harmful microorganisms present in the food and thus prevent the food spoilage. Irradiated food materials can be preserved for quite long periods.2.By Canning
In the canning process, the foodstuff is cooked and then stored in sterilized tin containers, and then the containers are sealed and made airtight. Canned food materials can be safely stored for long periods.3.By Bottling
Bottling technique is applied mainly for the preservation of milk. Milk is first pasteurised by heating to a temperature of nearly 70`C and then suddenly cooling it to about 20C. Pasteurisation kills most of the disease causing microorganisms present in the milk. Therefore, the milk is stored in bottles or polythene pouches. The process of pasteurisation is also used to disinfect some other food products such as fruit-juices, squashes, ketchups, etc.4. By Vacuum Drying
Milk can be preserved in the form of milk powder. Milk is converted into milk powder by vacuum drying. Due to the absence of moisture, milk powder can be stored without spoilage for quite long periods.
Preservatives found in food are a type of food additive. They can be natural or artificial. Different kinds of preservatives work in different ways. But, mostly preservatives are added to the food to prevent the food from decomposing by microbial growth or by any undesirable chemical changes. However, a process can also help to preserve the food better. Many fruits and meats are dried, so that they stay edible for longer. Also, methods like freezing, pickling, or smoking can greatly help to preserve the food. For example, we tend to store fresh fruits and vegetables in the refrigerator to keep them fresh for longer. Here are some natural common preservatives which we generally find in stored natural food items, and some of the synthetic harmful preservatives; and their short term and long term effects explained.Natural Preservatives
Spices seem to slow down the growth of microbes and also reduce the rate of oxidation. Spices like cloves, sage, mustard, thyme, and oregano are commonly used. Oil helps the foods to stay fresh by preventing microbes coming in contact with the food, also it reduces the rate of oxidation in food. Honey in its undiluted form acts as a great natural preservative, as it creates an excellent barrier against microbes. Wine which is a type of alcohol in itself acts as a good preservative. Processes like heating, cooking, pasteurization, and desiccation also act as a natural preservative alternative.Synthetic Preservatives
Eating foodstuffs which contain natural preservatives in small portions is okay. However, if your body is sensitive to natural preservatives-containing foods too, then you need to completely avoid them. Also, synthetic preservative in food need to be completely avoided. Because, the side effects of synthetic chemical preservative may not be evident in the beginning, but after some time a person might suffer from major side effects.
Disclaimer: This Buzzle article is for informative purposes only, and should not be used as a replacement for expert medical advice.
Last Updated: September 20, 2011
The Skinnygirl Margarita, created by Bethenny Frankel, pictured, has… (Robert Gauthier / Los Angeles…)
Reality TV star Bethenny Frankel's Skinnygirl Margarita was recently yanked from the shelves of Whole Foods markets for purportedly having a non-natural preservative thought to be sodium benzoate. Though the bottle reads "all natural," the grocery chain wasn't OK with it. TMZ reports that a class action lawsuit has also been filed against the parent company alleging misleading claims about the product being natural.
What is sodium benzoate, and should you be worried about ingesting it? The chemical is a preservative commonly found in foods most people consume daily, usually beverages such as sodas and juice drinks that are acidic. It's also found in items such as pickles, salsa and dip, and can turn up in cosmetics and medicines. Sodium benzoate is produced by a reaction of benzoic acid with sodium hydroxide, which makes it disolve in water.
Under acidic conditions, sodium benzoate inhibits growth of bacteria, mold and yeast, extending a product's shelf life, says Randy Worobo, associate professor of food microbiology at Cornell University in New York. "Without it a product's shelf life is much shorter, and that adds costs to the producer," he said.
While benzoic acid is found naturally in low levels in cranberries and other foods, the sodium benzoate listed on a product's nutrition label is typically synthesized in a lab.
Consumed under normal conditions it poses no great health dangers, says Don Schaffner, professor of food science at Rutgers University in New Jersey. "Sodium benzoate is still actively being studied, but in a comprehensive review [researchers] concluded that at levels being used in foods it doesn't pose a risk."
The Food and Drug Administration limits sodium benzoate to concentrations of 0.1% by weight, and Worobo says most foods have concentrations far lower--more like 0.025% to 0.05%.
But Schaffner says that doesn't mean it's OK to take a bath in the stuff, although he adds, "It's my understanding that it's not fat soluble," he added, "so it won't concentrate in the body."
When sodium benzoate combines with ascorbic acid (vitamin C) benzene can form, which is a known carcinogen. Factors such as heat and time can affect its development. Unless you're drinking gallons of soda and Skinnygirl Margaritas every day, Schaffner says, your risk of reaching dangerous levels is pretty low. And if you live in an urban area you're probably sucking up benzene via smog anyway.
Natural alternatives to sodium benzoate do exist, Worobo says. One product on the market is called Natamax and is used in foods such as breads and packaged shredded cheese. "The cost is significantly higher than that of sodium benzoate," he adds, which is probably why most food manufacturers go with the non-natural stuff.
So if processed foods are part of your normal diet and some chemically produced preservatives don't bother you, drink away--and of course, drink responsibly.