Food Preservation- Chemical Preservatives with Types, Examples

Chemical preservatives are intentional food additives incorporated into food to prevent or retard food spoilage caused by microbiological, enzymological, or chemical reactions.

  • These chemical preservatives should be nontoxic to humans or animals.
  • Chemical preservatives come under the food additives generally recognized as safe (GRAS).
  • Chemical preservatives can also be termed antimicrobials.
  • The main purpose of using chemical preservatives is to inhibit the growth and activity of foodborne pathogens and spoilage microorganisms. 
  • Chemical preservatives used in food can have both bacteriostatic and bactericidal properties per the concentration used.

How food can get chemical preservatives?

  • Intentional addition during food production, processing, or packaging
  • Chemical migration from the packaging materials
  • Due to a chemical reaction occurring in food
  • Residues of pesticides, herbicides, and fungicides on raw food materials
  • Migration of disinfectants used on utensils or equipment into foods

Role of chemical preservatives 

  •  Interferes with the cell wall, cell membrane, enzymatic activity, nucleic acids, etc., to prevent microorganisms’ growth and activity.
  • Retard, prevent or control undesirable changes in flavor, color, texture, or consistency of food and nutritive value of food.
  • Control natural spoilage of food
Chemical Preservatives as Food Preservation
Chemical Preservatives as Food Preservation

Classification of chemical preservatives

  • Class I: Traditional preservatives (natural)
  • Class II: Chemical preservatives (Artificial) 

Class I: Traditional Preservatives: These include preservatives like wood, smoke, sugar, honey, salt, spices, alcohol, vinegar, vegetable oil, spices, etc which are commonly used in our kitchen in past. These chemical preservatives are not restricted to use and there is no imposed limitation on their use. These naturally occurring preservatives are regarded as safe for human health.

Class II: Chemical preservatives: These are synthetic chemical preservatives that are made in the laboratory. For e.g nitrites, propionates, parabens, benzoates, acetates, sorbates, sulfur dioxide, etc.  

Microbial preservatives: These include antimicrobial preservatives like bacteriocins (e.g. nicin) which are produced by some strains of lactic acid bacteria and inhibit the growth of food spoilage or pathogenic bacteria. E.g nisin, produced by lactococcus lactis inhibits the growth of Clostridium tyrobutyricum, C. botulinum, and, listeria monocytogenes in cheese, other dairy products meats, fish, etc.  Using bacteriocins like microbial preservatives help reduce the use of chemical preservatives like nitrates, sorbates, and benzoates which consumers consider bad.

Ideal properties of chemical preservatives

Some food preservatives and their acceptable daily intake

Chemical preservatives with their ADI quantities (mg/kg BW). E (Europe) number refer to code for substance used as food additives. The E numbers for preservatives range from E200 to E399.

Table1: According to EU regulation, chemical food additives with their ADI quantities.

S.N.Chemical preservativeE numberADI (mg/kg BW)
1Sorbic acidE20025
2Sodium sorbateE20125
3Potassium sorbateE20225
4Benzoic acidE2105
5Sodium benzoateE2115
6ParabensE214-E21910
7Sulfur dioxide and SulfitesE220-E2280.7
8Potassium nitriteE2490.07
9Sodium nitriteE2500.1
10Sodium nitrate +E251 +3.7
11Potassium nitrateE2523.7
12Acetic acidE260
13Propionic acid and propionatesE280- E2895
Source: Adding Molecules to Food, Pros, and Cons: A Review on Synthetic and Natural Food Additives.  Marcio Carocho, Maria Filomena Barreiro, Patricia Morales, and Isabel C.F.R. Ferreira.

Factors affecting the effectiveness of chemical preservatives 

Chemical preservative properties

  1. Solubility 
  2. Toxicity

Microbial factors

  1. Microbial inherent resistance to chemical preservatives
  2. Initial microbial load
  3. Growth rate and phase of microorganisms
  4. Stress reaction of microorganisms
  5. Homeostasis ability of microorganisms
  6. Use of additional preservative methods

Intrinsic factors of food

  1. pH of the food
  2. Water activity of food

Extrinsic factors

  1. Storage time and temperature
  2. Gas composition
  3. Atmosphere and relative humidity

Different chemical preservatives and their application in the food industry

S.NChemical preservativesTargeted microorganismsMode of actionAdvantagesDisadvantagesApplications
1Sulfur dioxide (SO2)Yeast, moldIncrease pH and imbalance cellular metabolic process, alter the enzymatic system,Antioxidant properties, prevent browning, preserve color, cheaper and easily availableThe intense pungent odor and corrosive property makes it unuseful in canning Beverages, fruits products, heat-sensitive foods, effective for low pH foods
2Sorbates(Sodium sorbate and Potassium sorbate)   Yeast, Mold, Bacteria Disturb enzyme system, inhibit many enzymes involved in TCA cycleBeverages; juices, wines, cheese, fish meat bakery items,
3Benzoic acid and benzoatesYeast, moldsDisturb enzymatic systemMost active against yeasts and molds.
Used to preserve colored fruit juices
Risk of respiratory diseaseHigh acid foods, fruit drinks, cider, carbonated beverages, pickles, jams, salad dressings, soy sauce
4Parabens (p-hydroxybenzoic acid)Yeast, Mold, bacteriaDestroy complex structure of the cell and denature protein inside the cell Soft drinks, fish products, salad dressing
5Propionic acidMold, yeast, and a few bacteriaDisturb enzyme systemLow acid foods, processed cheese preservation
6Nitrate and nitriteAnaerobic bacteria (Clostridium botulinum), other pathogenic microbesInhibit metabolic enzymePreserve the color of red meat by forming nitrosomyoglobin The formation of carcinogenic nitrosamines is triggering extensive researchUsed in cured meats, better at low pH foods
7PhosphatesMore against gram-positive bacteria (Bacillus, clostridium)Chelating metal ions 
8SulfitesMore Bacteria, less effective to yeast and mold Target to the cytoplasmic membrane, DNA replication, protein synthesis, and enzymatic actions Acts as antioxidants and inhibit enzymatic browning Fruits and vegetable products, wine
9Sodium chloride (NaCl)BacteriaOsmotic shock to PlasmolysisBetter preservation if used as a pretreatment before canning, pasteurization, or dryingWeak against Staphylococcus and listeria monocytogensSalting of meats and fish
10Wood smoke (Traditional method)Bacteria, fungiThe release of different phenolic compounds, ketones, aldehyde, and alcohol, which serves as an antimicrobial preservativeEasy to use Meat, sausage, ham, bacon, fish
11NisinClostridium botulinum and other bacteriaCheese, cooked meat, poultry 

The working mechanism of organic acids on the bacterial cell

Organic acids like Acetic acid, benzoic acid, lactic acid, propionic acid, sorbic acid, etc., are effective as preservatives for foods with a pH of less than 5. So, they are the best for preserving acidic foods.

  1. At acidic pH, protonated or uncharged organic acid crosses the cell membrane and enters the cytoplasm.
  2. In neutral cytoplasmic pH, organic acids dissociate and release the proton that acidifies the cytoplasm.
  3. This cell uses ATP to pump protons out of the cell to deacidify the cytoplasm, which makes energy unavailable for their growth.

Table: Guidelines for using chemical preservatives in food by DFTQC, Nepal 2075 B.S. (2018 A.D.)

S.N.FoodPreservativesPPM
 1Sausage meat containing raw meat, Cereals, spicesSulfur dioxide450
 2Undried fruits: Cherries, Strawberries, and raspberries.

Other fruits
Sulfur dioxide2000        

1000
 3Concentrated fruit juiceSulfur dioxide1500
 4Dried fruitsSulfur dioxide1500
 5Apricots, peaches, apples, pearsSulfur dioxide2000
 6Sugar, dextrose, jaggery, refined sugarSulfur dioxide70
 7BeerSulfur dioxide70
 8CiderSulfur dioxide200
 9Alcoholic wineSulfur dioxide450
 10Dried gingerSulfur dioxide2000
 11Squash, fruit syrups, barley waterSulfur dioxide, or
benzoic acid
350 600
 12PicklesSulfur dioxide, or
benzoic acid
250 100
 13Jam, marmalade, fruit jellySulfur dioxide, or
benzoic acid
40 200
 14Coffee extractBenzoic acid120
 15Tomato or other juicesBenzoic acid750
 16Pickled meat, bacon, canned meatSodium nitrite or potassium nitrite200
 17Cheese or processed cheeseSorbic acid or Sodium sorbate or potassium sorbate3000
 18PaneerSorbic acid or Sodium sorbate or potassium sorbate2000
 19Flour confectionerySorbic acid or Sodium sorbate or potassium sorbate1500
 20Baking flourSodium diacetate,

Propionates,

Methyl propyl hydroxybenzoate
2500

3200  

500

Do you know? 

  • Nitrite and nitrate preservatives should not be used in infant foods.
  • The use of titanium dioxide (E171) is fully banned as a food additive in the EU.

“Preservatives can be used to extend the expiration dates of food but unfortunately not of people.”

References 

  1. Potter NP (1987), Food Science, CBS Pub, India
  2. Rahman MS (1999), Handbook of Food Preservation, Marcel Dekker, Inc, NY
  3. Desrosier EN (1963), The Technology of Food Preservation, AVI Publishing Company, New York
  4. Thomas J. Montville, Food microbiology an introduction (third edition), ASM Press, Washington, DC
  5. PAȘCA, C., COROIAN, A., & SOCACI, S. (2018). Risks and Benefits of Food Additives – Review. Bulletin Of University Of Agricultural Sciences And Veterinary Medicine Cluj-Napoca. Animal Science And Biotechnologies, 75(2), 71. DOI: 10.15835/buasvmcn-asb:2018.0026.
  6. Department of Food Technology and Quality Control (DFTQC), 2075 guideline

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