Food Additives including Chemical Preservatives-Classification, functions and uses in foods

Foodnon-nutritive additives are substances or mixture of substances, other than a base food stuff,  which either improve the flavor, texture, colour or chemical preservatives, taste, appearance or function as processing aid. Food additives as  substances added intentionally to food, generally in small quantities, to improve its appearance, flavor, texture or storage properties.
Need for Food Additives:
Additives provide protection against food spoilage during storage transportation, distribution or processing.
 Many of these chemical additives are used to fortified or enriched the food Potassium iodide, for instance, added to common salt can eliminate goiter, enriched rice or bread with B-complex vitamins can eliminate pellagra, and adding vitamin D to cow milk prevents rickets.

The use of food additives is to maintain the nutritional quality of food, to enhance stability with resulting reduction in waste, to make food more attractive, and to provide efficient aids in processing, packaging and transport.
Classification of food additives
Class of additive
Function
Examples

Anti-caking agents
Keep powdered products (e.g. salt) flowing freely when poured
Bentonite (558),
Calcium aluminium silicate (556),
Calcium silicate (552)

Anti-foaming agents
Reduce or prevent foaming in foods
Polyethylene glycol 8000 (1521),
Triethyl citrate (1505)

Antioxidants
Retard or prevent the oxidative deterioration of foods
Butylated hydroxyanisole (320),
Ascorbyl palmitate (304),
Calcium ascorbate (302)

Artificial sweeteners
Impart a sweet taste for fewer kilojoules/calories than sugar
Sorbitol (420),
Alitame (956),
Aspartame (951),
Saccharin / calcium saccharin (954)

Bleaching agents
Whiten foods
Chlorine (925),
Chlorine dioxide (926),
Benzoyl peroxide (928)

Bulking agents
Increasing the bulk of a food without affecting its nutritional value
Ammonium chloride (510),
Isomalt (953),
Polydextrose (1200)

Colourings
Add or restore colour to foods
Curcumin (110),
Brilliant blue FCF (133),
Tartrazine (102)

Colour retention agents
Retain or intensify the colour of a food
Ferrous gluconate (579)

Emulsifiers
Prevent oil and water mixtures separating into layers
Lecithin (322),
Sorbitan monostearate (491),
Ammonium salts of phosphatidic acids (442)

Enzymes
Break down foods (e.g. ferment milk into cheese)
α-amylase (1100),
Lipases (1104),
Proteases (papain, bromelain, ficin) (1101)

Firming agents
Strengthen the structure of the food and prevent its collapse during processing
Calcium chloride (509),
Calcium gluconate (578),
Calcium sulphate (516)

Flavour enhancers
Improve the flavour and/or aroma of a food
Calcium glutamate (623),
Disodium 5′-ribonucleotides (635),
Ethyl maltol (637)

Food acids
Maintain a constant level of sourness in a food
Acetic acid (260),
Citric acid (330),
Fumaric acid (297)

Flour treatment agents
Improve flour performance in bread making
Sodium metabisulphite (223),
Ammonium chloride (510),
Potassium bromate (924)

Glazing agents
Impart a shiny appearance or provide a protective coating to a food
Beeswax, white and yellow (901),
Carnauba wax (903),
Shellac (904)

Gelling agents
Thicken and stabilize various foods (e.g. jellies, deserts and candies)
Agar (406),
Calcium alginate (404),
Carrageenan (407)

Humectants
Prevent foods from drying out (e.g. dried fruits)
Glycerin or glycerol (422),
Lactitol (966),
Oxidised polyethylene (914)

Mineral salts
Improve the texture of a food (e.g. processed meats)
Cupric sulphate (519)

Preservatives
Protect against deterioration caused by microorganisms
Sodium nitrate (251),
Benzoic acid (210),
Sodium benzoate (211)

Propellants
Gases which help propel a food from a container
Carbon dioxide (290),
Nitrogen (941),
Nitrous oxide (942)

Sequestrants
Bind and remove unwanted minerals that cause oxidation
Potassium gluconate (577)

Stabilisers
Maintain the uniform dispersion of substances in a food
Xanthum gum (415),
Guar gum (412),
Bleached starch (1403)

Thickeners
Improve texture and maintain uniform consistency
Tannins (181),
Sodium alginate (401),
Pectins (440)

Vitamins
Restore vitamins lost in processing and storage
B vitamins, including niacin
Vitamin C
Vitamin E

Caffeine and other GRAS (generally recognized as safe) additives such as sugar and salt are not required to go through the regulation process.
Preservatives
Definition:
A preservative is defined as any substance which is capable of inhibiting, retarding or arresting the growth of microorganisms of any deterioration of food due to microorganisms, or of marking the evidence of any such deterioration. Microbial spoilage of food products is also controlled by using chemical preservatives.
The inhibitory action of preservatives is due to their interfering with the mechanism of cell division, permeability of cell membrane and activity of enzymes. Pasteurized squashes, cordials and crushes have a cooked flavour. After the container is opened, they ferment and spoil within a short period, particularly in a tropical climate. To avoid this, it is necessary to use chemical preservatives. Chemically preserved squashes and crushes can be kept for a fairly long time even after opening the seal of the bottle. It is however, essential that the use of chemicals is properly controlled, as their indiscriminate use is likely to be harmful. The preservative used should not be injurious to health and should be non-irritant. It should be easy to detect and estimate.
Classification of preservatives
Class I preservatives are generally preservatives that are found in the common kitchen. The Class-I Preservative includes salt, vinegar, salt, vegetable oil, honey, sugar and wood smoke. When looking at the two preservatives, it is always better to choose products that come with Class 1 preservatives as they are not dangerous to the health.
Class-II Preservative is manmade. Class-II Preservatives are unnatural preservatives. Sorbates, sulfites and benzoates are some of the Class II preservatives used. There are certain limits in using Class II preservatives and more restrictions are implemented in its usage.                                                      As Class 1 preservatives are natural, there is no need to be cautious while using it. On the other hand, some risk is involved when using Class II preservatives as they are chemicals. Example, Benzoic acid, sulphurous acid, Nitrates / nitrites of sodium/ potassium in respect of foods like ham, pickled meat, Sorbic acid- sodium, potassium & calcium  salts, Nisin, Sodium  and calcium propionate
Permissible limits of Class II preservatives   in food products (FPO)
Sulphur dioxide
1.
Fruit pulp
-
2000-3000 ppm SO2

2.
Fruit juice concentrate
-
1500 ppm SO2

3.
Dried fruits viz., apples, peaches pears and other fruits
-
2000 ppm SO2

4.
Raisins
-
750 ppm SO2

5.
Squashes, cordials, crushes, fruit syrups and fruit juices
-
700 ppm of KMS

6.
Jam, marmalade, preserve
-
40 ppm SO2

7.
Crystallized and glazed  fruits
-
150 ppm SO2

8.
RTS
-
70 ppm

9.
Pickles  and chutneys
-
100 ppm SO2

10.
Dehydrated vegetables
-
2000 ppm SO2

11.
Syrups  and sherbets
-
350 ppm SO2

12.
Wines
-
450 ppm SO2

Benzoic acid



1.
Squashes, crushes  fruit, syrups, cordials
-
600 ppm

2.
Jam, jelly, marmalade
-
200 ppm

3.
Pickles  and chutneys
-
250 ppm

4.
Tomato and other sauces
-
750 ppm

5.
Tomato puree and pasta
-
250 ppm


Class-I Preservative /Natural preservatives:
Sodium chloride: Salts stop the growth of microorganisms and interfere with the action of proteolytic enzymes. Salts also cause food dehydration by drawing out water from the tissue cells. Salt is employed to control microbial population in foods such as butter, cheese, cabbage, olives, cucumbers, meat, fish and bread. The amount of salt added determines the extent of protection afforded to the food. In the preservative action of NaCl, there is synergistic action with other intrinsic factors such as PH or extrinsic factors such as temperature, partial pressure of oxygen etc.,
Sugar: Sugar aid in the preservation of products in which it is used. The high osmotic pressure of sugar creates conditions that are unfavourable for the growth and reproduction of most species of bacteria, yeasts and moulds. The preservative action of moderate strength of sugar can be improved if invertase is used to increase the concentration of glucose relative to sucrose. Foods in which sugars aid preservation include syrups and confectionary products, fondant fillings in chocolate, honey, jellies, marmalades, conserves and fruits such as dates, sultanas and currants.
Class-II Preservative /Chemical preservatives:
Sulphur Dioxide: It is used in the treatment of fruits and vegetables before & after dehydration to extend the storage life of fresh grapes, prevents the growth of undesirable microorganisms during wine making, and in the manufacture of fruit juices. It has good preserving action against bacteria and moulds and inhibits enzymes, etc. Sulphur dioxide is also the most useful agent for the prevention of browning reactions in dried fruits. Most cut fruits are treated with sulphur dioxide to prevent enzymatic browning. In addition, it acts as an antioxidant and bleaching agent. These properties help in the retention of ascorbic acid, carotene and other oxidizable compounds. It is generally used in the form of its salts such as sulphite, bisulphate and metabisulphite.
Potassium metabisulphite (K2O2So2 (or) K2S2O5) is commonly used as a stable source of So2. It is fairly stable in neutral (or) alkaline media. When added to fruit juice (or) squash it reacts with the acid in the juice forming the potassium salt and So2 which is liberated and forms sulphurous acid with the water of the juice.
SO2 has a better preservative action than sodium benzoate against bacteria and moulds. It also retards the development of yeasts in juice, but cannot arrest their multiplication, once their number has reached a high value. The toxicity of So2 increases at high temperature. Hence its effectiveness depends on the acidity, pH, temperature and substances present in fruit juice.
According to FPO, the maximum amount of So2 allowed in fruit juice is 700 ppm, in squash, crush and cordial 350 ppm and in RTS and nectar 100 ppm.
 Advantages of using So2 are
It has a better preserving action than sodium benzoate against bacterial fermentation.
it helps to retain the colour of the beverage for a longer time than sodium benzoate.
being a gas, it helps in preserving the surface layer of juices also.
being highly soluble in juices and squashes, it ensures better mixing and hence their preservation
any excess of So2 present can be removed either by heating the juice to about 71oC or by passing air through it or by subjecting the juice to vacuum. This causes some loss of the flavoring materials due to volatilization, which can be compensated by adding flavours.

Disadvantages of using So2 are
It cannot be used in the case of some naturally colored juices like those of jamun, pomegranate, strawberry, coloured grapes, plum etc. on account of its bleaching action.

Organic acid:- Various acid like acetic acid, benzoic acid, sorbic acid, etc. are used as chemical preservatives n pickles, sauces, syrup, soft drink etc.

Sorbic acid: It is found in the mountain ash berries. Sorbic acid (CH3-CH = CH  CH = CH  COOH) and its sodium and potassium salts inhibit moulds and yeasts, in foods such as cheese, baked products, fruit juices, wines and pickles. The antimicrobial action of sorbic acid is due to its inhibitory influence on various enzymes in the microbial cell. The enzymes inhibited by sorbic acid include the following:
1. Enzymes involved in carbohydrate metabolism such as enolase and lactate dehydrogenase.
2. Enzymes of citric acid cycles such as malate dehydrogenase, isocitrate dehydrogenase, ketoglutarate dehydrogenase, succinate dehydrogenase, and fumerase.
3. Several enzymes containing SH group, and other enzymes such as catalase and peroxidase. The antimycotic action of sorbic acid is due to the inability of moulds to metabolize the conjugated unsaturated structure.
Propionic acid: Propionic acid (CH3CH2COOH) and its sodium and calcium salts exert antimicrobial activity against moulds and some bacteria. The acid finds extensive use in bakery field, where it not only inhibits moulds effectively but is also active against the ropy bread organism Bacillus mesentericus. The toxicity of propionic acid to moulds and certain bacteria is related to the inability of the organisms to metabolize the three-carbon unit.
Benzoic acid: Benzoic acid is widely used as an antimicrobial agent. Its sodium salt is more soluble in water than the free acid and hence it is generally used. Sodium benzoate is nearly 170 times as soluble as benzoic acid; pure sodium benzoate is tasteless and odourless. The antibacterial action of benzoic acid is increased in the presence of Co2 and acid e.g.Bacillus subtilis cannot survive in benzoic acid solution in the presence of Co2.
Benzoic acid is more effective against yeasts than against moulds. It does not stop lactic acid and acetic acid fermentation. The quantity of benzoic acid required depends on the nature of the product to be preserved, particularly its acidity. In case of juices having a pH of 3.5-4.0, which is the range of a majority of fruit juices, addition of 0.06 to 0.10% of sodium benzoate has been found to be sufficient. In case of less acid juices such as grape juice at least 0.3% is necessary.
According to FPO its permitted level in RTS and nectar is 100 ppm and in squash, crush and cordial 600 ppm. In the long run benzoic acid may darken the product. It is, therefore, mostly used in colored products of tomato, jamun, pomegranate, plum, watermelon, strawberry, coloured grapes etc.
It cannot also be used for juices which are to be packed in tin containers because it not only corrodes the tin causing pinholes, but also forms H2S which has a disagreeable smell and reacts with the iron of the tin container to form a black compound, both of which are highly undesirabl
 So2 gives a slight taste and colour to freshly prepared beverages but these are not serious defects if the beverage is diluted before drinking.
Acetic acid: Acetic acid (CH3COOH), in the form of vinegar, has been used to preserve pickled vegetables from antiquity. Acetates of sodium, potassium and calcium, are used in bread and other baked foods to prevent ropiness and the growth of moulds, but they do not interfere with yeasts. The acid is also used in foods, such as mayonnaise and pickles, primarily for flavor but these products also benefit from the concurrent anti-microbial action. The anti-microbial activity of acetic acid increases as the PH decreases.
Nitrites and Nitrates.  (NaNO2 and NaNO3)
Used in meat to cure to:
Stabilize red meat color
 inhibit spoilage and pathogenic organisms
contribute to flavor
Mode of Action
Nitrate is reduced by bacteria in the meat to nitrite, which is further reduced to nitric oxide (NO), a compound that reacts with heme or iron-sulfur groups.
In meat, NO reacts with the heme in myoglobin to form nitrosohemochrome which gives meat a red color.
In bacteria, NO reacts with and destroys and iron-sulfur enzyme, ferredoxin, that is involved in ATP synthesis.  Without ferredoxin, the cells cannot synthesize energy and die.
Nitrates or nitrites are added as a preservative, antimicrobial agent or colour fixative to processed foods such as meats and cheese. Nitrite is added in the food as an antioxidant. Nitrate also occurs naturally in water, vegetables and plants. Nitrite when added in the food as preservative they combine with feradoxine of the microorganism so the action of this protein stoped and due to which ATP synthesis stopped in the microbial cell.  The human body converts nitrate in food into nitrite. Nitrite has been implicated in a variety of long term health effects, including gastric cancer.
 Parabens: These are alkyl esters of p-hydroxy benzoic acid. The methyl, ethyl, propyl and heptyl esters are generally used . These are effective inhibitors of moulds and yeasts, but are relatively ineffective against bacteria. They are active at PH 7 and higher and have little effect on flavor.
 Epoxides: Epoxides are cyclic ethers that destroy all forms of microorganisms including spores and even viruses. The epoxides used as preservatives are ethylene oxide and propylene oxide. The epoxides are used in gaseous form and after adequate exposure; the residual epoxide is removed by flushing & evacuation. Their use is limited to dry items, such as nuts and spices.
Nisin. Incorrectly called an antibiotic, actually a bacteriocin. Used in processed dairy foods and low acid canned foods.    (some true antibiotics are used in other countries)
Useful properties:
nontoxic to humans
natural
heat stable (at low pH)
good storage stability
doesnt create off odors or flavors
no cross resistance to other clinical antibiotics, no clinical applications
Use in low acid canned foods (e.g. green beans) allows a dramatic reduction in heat processing time and temp-gives increased quality to the food. Use in U.S. is limited to pasteurized process cheese spreads to prevent botulism.