Preservatives in food processing, The food industry is one of the most important industries in the world, as manufacturing food products requires many technologies and measures to ensure product quality and consumer safety
. Among these technologies, preservatives play a prominent role in keeping food fresh and safe for long periods. We will take an overview of preservatives used in the food industry and their vital role.
Table of Contents
New preservatives and permitted preservatives
We define preservatives as substances that are used to protect some foods from microbial spoilage and oxidation reactions. The percentage of food losses due to microbial spoilage, according to the Food and Agriculture Organization of the International Organization (FAO), is estimated at about 20%. This shows us the importance of microbial spoilage in food and the need to move towards reducing or preventing it.
The processes of protecting food from microbial corruption began thousands of years ago, as salting and pickling processes were used for this purpose, then the drying technique was used, followed by canning and freezing techniques, to achieve the same goal, which is to protect food from corruption. Not all of the above-mentioned food preservation techniques and methods are suitable for all foods. For example, canning as a preservation method against microbial spoilage can be applied to foods that are consumed cooked and cannot be applied to many foods. There are many foods marketed on a daily basis that need only minimal protection against microbial spoilage. Such food cannot be treated with known preservation methods such as drying, canning and freezing. Perhaps the best way to preserve such food is to add preservatives. These foods include jams, jellies, natural fruit juices, squash, fruit nectar,
cheeses, sausages, bread, cured meats, soft drinks, fruity yogurt, and more.
It is worth mentioning in the field of preservatives that foods for infants and young children should not contain nitrate or sodium nitrite. The addition of mixtures of preservatives (more than one preservative) to certain food groups is controlled by law. Food legislation defines food groups to which preservatives may be added, and defines the permitted preservatives and the upper limit of these materials. It remains to be known that the law does not oblige the food factory to add preservatives in the foods it manufactures, except for some cases. In Britain, for example, British law forces salted and cured meat factories to add preservatives to them.
The primary function of preservatives is to prevent microbial spoilage, and the mechanism for this prevention may be one or more of the following:
- The preservative interferes with the work of the cell membrane in microorganisms.
- Interaction with genes.
- Contrasting with enzymatic activity inside the cell.
First, the most widely used preservatives
Sulfur dioxide and various sources of sulfate
Sulfur dioxide (SO2) is a gas produced by burning elemental sulfur, and if it is dissolved in water, it will form sulfuric acid, which is sulfur salts that can be crystallized in the form of a powder. In America, for example, five types of sulfite sources are allowed as food preservatives, which are sodium sulfites, sodium bisulfites, sodium metabisulfites, potassium bisulfites and potassium metabisulfites. As for English legislation, it allows the use of six types of sulfites sources, which are the five permitted by American law in addition to potassium sulfite While the international list also contains six types of sulfite sources as food preservatives, these substances are the same as those allowed by the US legislator, in addition to calcium metabisulfite.
Sulfur dioxide has been used as a food preservative for a long time, and there are indications that the ancient Egyptians used smoke from burning sulfur to preserve their wines. Sulfur dioxide and sulfite salts are multi-use additives. In addition to being preservatives, they prevent enzymatic or non-enzymatic browning and oxidation. Sulfites are also used as processing aids in the biscuit industry, where they are added to change the physical properties of the biscuit dough.
It is evident from the properties of some of the most commonly used preservatives, including sulfur dioxide and various sulfur salts. It turns out that the various sources of sulfite are more soluble in water than sulfur dioxide, and sodium bisulfite is the most soluble in water, as its solubility reaches 3 kg / liter.
2- Benzoic acid, benzoate and parahydroxy esters of benzoic acid or the so-called parabens:
Benzoic acid and its salts of sodium, potassium and calcium are effective against microbial activity. The sodium esters of benzoic acid in the form of heptyl are considered the most effective against fungi and gram-positive bacteria, followed by sodium esters in the form of propyl valethyl
and finally methyl. The undissociated part of benzoic acid is the active part against microorganisms and this is due to the fact that it does not carry a charge, which facilitates its entry into the microbial cell as it does not carry a charge, and the effect of benzoic acid and its esters as preservatives is greatly affected by the pH, where The higher this number, the greater the dissociated ionization rate, so we find that the optimum pH for the action of benzoates is between 2.5-4, meaning that benzoates are effective in an acidic medium, while esters of benzoic acid (parabens) work at a wide range of pH, which is is ionized.
It is clear that benzoate has better solubility than benzoic acid, while the effectiveness of sodium benzoate is 85%, the effectiveness of calcium benzoate reaches only 76%. The same table also shows that benzoic acid and benzoate have good activity against fungi, food poisoning bacteria and spore-forming bacteria. Among the most important foods to which benzoic acid and benzoate are added are soft drinks, fruit juices and pickles. The concentration used ranges from 160 parts per million in the case of soft drinks to 800 parts per million in the case of fruit juices. What is wrong with benzoic acid and benzoate is that they sometimes add a phenolic taste to foods that help preserve them.
3- Nitrates and nitrites
Sodium and potassium nitrates and nitrites are used to preserve meat and meat products and some types of cheese. This is due to two main reasons. The first is its ability to preserve the red color in meat. This is done by microbial reduction of nitrates to nitrites and then nitrites to nitrous oxide, where the latter reacts with myoglobin pigment and gives the red colour. The second reason is that some studies have indicated that nitrates and nitrites have good efficacy against the activity of botulinum toxin bacteria, as well as coliform, which causes gas pockets in cheeses. It is worth noting that some recently published research raised some doubts about the effectiveness of nitrites against bacteria, and for this reason it was suggested to reduce the amount of nitrate used in meat to 40 mg/kg, which is the minimum for color fixation. Another permitted preservative is added to improve microbial inhibition.
Nitrates and nitrites are water soluble, and sodium nitrite is more effective (68%) than potassium nitrite (55). 3.4).
What is taken from the use of nitrates and nitrites as preservatives is the possibility of their interaction with secondary amines to form nitrous amines, which are carcinogenic substances. As a result, the use of nitrates as a preservative has become a subject of debate and controversy in the past twenty years, which has prompted some countries to re-review and revise the limits or permissible concentrations of nitrates used in foods. When comparing the English position with the American position on the use of nitrates, we find that the English position is less strict. The English position is based on the results of assessing the safety of nitrates, which are positive, and that the concentrations used are few, in addition to the fact that the possibility of nitrites converting to nitrous amine is small compared to the amount of nitrites formed by saliva, not to mention that the quantities of nitrates that enter the human body through water The vegetables are relatively large.
4- Sorbic acid and sorbate
Sorbic acid and both sodium, potassium and calcium sorbate are used as food preservatives and are good against fungi and to a lesser extent against bacteria and ineffective against lactic acid bacteria. It is also clear that the appropriate pH for making the sorbate is 4.8 and the action of the sorbate against microorganisms can be maintained up to pH 6.5. Sorbic acid is slightly soluble in water, fat and brine, and has good solubility in ethyl alcohol.
Sorbic acid and sorbate are used as preservatives in many foods such as wines, cheeses, soft drinks, jams with low sugar content, delicate desserts, as well as salads and mayonnaise. The concentrations used for sorbets range from 200 ppm in the case of wines to 1,000 ppm in the case of salads and mayonnaise. In America, for example, it is allowed to use sorbic acid with a concentration of up to 2000 mg/kg and potassium sorbate with a concentration of up to 3000 mg/kg.
5- Propionic acid and propionate
Propionic acid and sodium, potassium and calcium propionate are used as preservatives for bread in Britain and for bread, puddings, and
puddings in America. Propionate is very effective against fungi and bacteria that cause worms in bread, but it is less effective against other types of bacteria. As in the case of benzoate, sorbate and nitrate, propionate is also highly dependent on the pH degree in its effectiveness as the most suitable pH for its work as a preservative is 4.9. As is also the case in sorbates and benzoates, the calcium salts of propionate are considered to have a lower solubility in water compared to the sodium salts. Propionate is added in concentrations of up to 3000 ppm in the case of bread and to 1000 ppm in the case of delicate desserts. The fault for the propionate is that it has a cheese taste. Propionic acid is naturally produced in some types of cheese, such as Swiss cheese, and its concentration reaches 1%. The list of preservatives included Sodium, Calcium and Potassium Propionate, which has international numbers 281, 282, 283.
6- Nisin
Nisin is a polypeptide made up of seven amino acids. It is an antibiotic, its solubility in water depends on the pH. It is soluble in an acidic medium (pH less than 5) and insoluble at pH 7. Its effectiveness as a preservative appears at a pH between 6.5-6.8, and it is not effective against bacteria. Botulism is active against Gram-positive bacteria, lactic acid bacteria, Streptococcus, Bacillus and Clostridium. Nisin is added as a preservative to cheese at a concentration of 12 ppb, dairy products at a concentration of 9 ppb, and to canned foods at a concentration of 9 ppb as well. Nisin is a natural product in cheese, produced by the bacterium Streptococcus lactis.
7- Hexamine
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Hexamine is called hexamethylenetetraamine and is produced by the reaction of formaldehyde with ammonia, so its effectiveness as a preservative depends on its decomposition and the production of formaldehyde. Hexamine is insoluble in water but is soluble in most organic solvents. Hexamine is effective as a preservative at a wide range of pH, especially after pH 4.5, so it is used to preserve fish that were
initially preserved with benzoates. Hexamine is effective against most microorganisms. Hexamine is also used to preserve some types of cheese and is added to it in concentrations not exceeding 25 mg / kg, which is equivalent to 25 parts per million, while in the case of fish it is added at concentrations not exceeding 50 parts per million.
8- Biphenyl and the sodium salt of hydroxybiphenyl
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It is noted that these two preservatives are not mentioned in the international list of preservatives, meaning that they are not allowed to be used in countries that apply international legislation for additives, including Jordan, as a preservative, but it has been classified as a pesticide. A committee of the International Health and Food and Agriculture Organizations has set the allowable residue of biphenyl in food as 0.1 mg/kg. Biphenyl is used to prevent spoilage of fruits, especially citrus fruits, as it is added at a concentration of up to 70 parts per million. It is also added to packaging materials for citrus fruits. Biphenyl and its hydroxy derivative are considered effective against fungi and at a wide range of pH.
9- Thiazole Benzimidazole
This preservative is insoluble in water, but soluble in organic solvents. It works at a wide range of pH and is effective against fungi. It is used to preserve bananas and citrus fruits from microbial corruption. It is added at a concentration of 3 parts per million on the surface of citrus and 10 parts per million on the surface of bananas.
Second / least used preservatives
hydrogen peroxide
Hydrogen peroxide is one of the preservative additives dissolved in water and works until a pH is reached. Hydrogen peroxide has good activity against Gram-negative bacteria such as coliform group and against Staphylococcus and lactic acid bacteria. It is mainly used to preserve milk and is added in concentrations up to 1000 ppm.
Sodium chloride
Table salt is blamed for adding a salty taste to the food that is preserved in it, and from the food that is usually preserved in it is butter, industrial margarine and some types of cheese, and it is added to it at a rate of 2%, and it is also used to preserve fish where it is added by up to 28%. The pH at which table salt operates is wide and is effective against Gram-negative Bacillus and lactic acid bacteria.
EDTA (Tetra-Acetic Acid Ethylene Diamine)
This additive is basically a chelating substance, but it has activity against some microorganisms such as Gram-negative bacteria and Clostridia, and it acts as a preservative in both neutral and alkaline mediums. Among the foods in which salads and fish are preserved, where they are added on their surface, the concentrations used as a preservative are between 100 and 300 parts per million.
4- Butyl Hydroquinone
This additive is also used mainly as an anti-oxidant, but it is effective against the activity of some microorganisms such as fungi, Staphylococcus aureus, and has a low solubility in water, but it is soluble in corn oil and propylene glycol. The appropriate pH for its work is between 4-9, and it is mainly used as a preservative for fats and oils and is added at concentrations of up to 200 parts per million.
Third / the new preservatives included in the 2004 list.
The following is a brief summary of the new preservatives included in the 2004 list.
- Dimethyl Dicarbonate, which carries the international number 242 and is added to six food groups, such as flavored drinks that contain water,
not fruit juice, tea, coffee and hot cereal drinks, except for cocoa. The amount of addition is between 200 to 250 mg/kg.
- Calcium Disodium Ethylene Diamine Tetra Acetate and Disodium Ethylene Diamine Tetra Acetate with the numbers 385 and 386. These two substances have many uses. In addition to being preservatives, they are basically antioxidants and chelating substances.
Since these two substances are multi-use, they are added to a large number of food groups (10 groups), such as oils and fats, fruits, vegetables, meat, fish…etc. The concentration to which it is added ranges from 25 mg/kg as in malt barley drinks to 800 ppm in dried vegetables.
- Ferrous Gluconate, bearing the international number 579. This substance also has many uses. In addition to being considered a preservative, it is basically a color stabilizer and an acidity regulator. It is added to vegetables, including mushrooms, tubers and legumes. The concentration used is 150 mg/kg.
- Formic acid, which carries the international number 265, was approved as a preservative added to sauces and similar products in 2001 with a concentration of 200 mg / kg, while it was added at a concentration of 100 mg / kg to flavored drinks that contain water and not fruit juice, including energy and sports drinks and the like. .
- Hexamethylene Tetramine, international number 239, is only added to mature cheeses and at a concentration not exceeding 25 mg/kg, and has been included in the international list of preservatives since 2001.
- Isopropyl Citrate, number 384, which is versatile. In addition to being a preservative, it is used as an antioxidant and as a chelating agent. It is added to several groups of foods such as oils, meat, drinks, and others. The concentration in which it is added ranges between 100-200 mg/kg, and it has been included in the international lists of additives since 2001.
- Lysozyme Hydrochloride, No. 1105, was approved as a preservative added to mature cheeses since 1999, and the concentration to which it is added is based on GMP Good Manufacturing Practice.
- Ortho Phenylphenol, number 231, has been approved as a preservative added to the surface of fresh fruits since 1999, with concentrations of up to 12 mg/kg.
- Pimaricin or Natamycin, which is an antibiotic that was separated from a type of bacteria in North Africa in 1955 and approved as a preservative
Preservatives added to meat
by the Codex Alimentarius Committee since 2001 AD. Natamycin is considered to have good efficacy against molds and yeasts and has no effect on bacteria or viruses. It bears the international number 235 and is added to cheeses at concentrations up to 40 mg/kg and to cooked meats at concentrations up to 6 mg/kg.
- Stannous chloride, INC number 512, is multi-use. In addition to being a preservative, it is used as an antioxidant, chelating agent, and color stabilizer. It is added to several food groups, such as canned fruits (20 mg/kg), drinks that do not contain fruit juice and water-based (20 mg/kg), and canned vegetables, including mushrooms, tubers and legumes (25 mg/kg). It has been included in the international lists of additives since 2001.
It is noted in the last amendment to the specification of food additives by the Codex Alimentarius Committee in 2004 the absence of a large number of traditional preservatives such as sulfur and sulfites and their many sources, as well as nitrates, nitrites, propionates, sorbates and others. The revised list included only 15 preservatives out of 53 items on the list.
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