Hafsa Alam

Anti microbial preservative

Food and Dairy Microbiology

Control by antimicrobial preservative in food industry

It is done for the following reasons: To preserve the natural characteristics of food. To preserve appearance of food. To increase shelf life of the food. To save the food from spoilage causing microbes.

Food preservation

Definition: Chemicals used in food in relatively small

dose to kill undesirable microorganisms. Prevent decomposition of food by

preventing growth of bacteria or fungi.

Antimicrobial preservatives

Differ greatly in ability to act against different microorganism.

Some are Narrow spectrum.

Some are Broad spectrum.

Some act against viruses,bacterial spores,or fungi.

Characteristics

Cont.…

Germicide Fungicide Bactericide Sporicide viricide

Fungistatic bacteriostatic

Some have killing effect

Some have static effect

Less toxic. Broader antimicrobial spectrum. Cidal effect. Not only effective against vegetative cells but also

against spores. Stable to heat and storage Chemically compatible. Reasonable cost. Acceptable taste,odour and color.

An antimicrobial preservative must be

Available in aqueous phase at effective level concentration.

Should be in unionized state to penetrate bacteria.

Must no bind to other components of emulsion.

Cont…

There are some preservative chemicals that have antimicrobial role in food:

Examples of food preservatives

Nitrites Sulphur dioxide

Hydrogen peroxide

Epoxides BHA,BHT, TBHQ

EDTA Parabens Acids

Diacetyle Chitosan

Lysozyme Monolaurin Wood smoke

Antibiotics Spices

Acetic acid Disrupt cell membrane function(bacteria,yeast and some molds)

Benzoic acid Disrupt cell membrane function/inhibit enzyme(mold,yeast& some bacteria)

nitamycin Bind sterol group in fungal cell membrane(mold & yeast)

nicin Disrupt cell membrane function(gram positive bacteria& lactic acid producing bacteria)

Nitrates,nitrites Disrupt cell membrane function/inhibit enzyme(bacteria primarily chlostridium botulinum)

Propionic acid Disrupts cell membrane function(molds and some yeast)

Sorbic acid Disrupt cell membrane,inhibit enzyme,disrupt bacterial spore germination)

Suphites,sulphur dioxide

Inhibit enzyme and form additional compounds(bacteria,yeast and mold)

Antimicrobials

Used in heat processed meat, poultry & fishTo control growth & toxin production by c.botulinum.

Used in some cheeses to prevent gas production by c.butyricum &

c.tyrobutyricum. Inhibitory to Staphylococcus aureus, Escherichia,

Pseudomonas & Enterobacter.

Nitrites

Mode of action:• React with enzymes in vegetative cells &

germinating spores, restriction of bacterial use of iron and interference with membrane

permeability,thereby limiting transport.

Side effect :Nitrite can lead to formation of

carcinogenic compounds,nitrosamines.So there is trend to reduce nitrite or to use

other preservation.

Used in soft fruits, fruit juices, lemon juices, beverages, wines, sausages, pickles, and fresh shrimp.

Antimicrobial action:

produced by undissociated sulfurous acid that rapidly enters cell and reacts with thiol groups in structural proteins, enzymes, and cofactors, as well as with other cellular components.

Sulphur dioxide & sulfites

Fungicidal: at low pH. & low Aw.

Bacteriostatic; at low concentration.

Bactericidal: at higher concentration.

Hydrogen peroxide: Germicidal

Mode of action:In secreted fluids, the enzyme lactoperoxidase (LP) catalyzes the oxidation of thiocyanate ion (SCN-) by hydrogen peroxide (H2O2), producing the weak oxidizing agent hypothiocyanite (OSCN-), which has bacteriostatic activity.

• Used in Cheese production

& Liquid egg

for destruction of Salmonella.

EpoxidesEthylene oxide & propylene oxide

Germicidal & fumigants

Mode of action:act as alkylating agents and react with various groups (e.g., –SH, –NH2, and –OH) in cellular

macromolecules, particularly structural proteins and enzymes, adversely affecting their functions

Indirect antimicrobials. BHA inhibits growth of many Gram-positive and

Gram-negative bacteria and also effectively prevent growth and toxin production by molds and growth of yeasts.

The antimicrobial action is most likely produced by their adverse effect on the cell membrane and enzymes.

Butylated Hydroxyanisol (BHA), Butylated Hydroxytoluene (BHT), and t-Butyl Hydroquinone (TBHQ)

Chitosan

Polycationic polymer,obtained by alkaline hydrolysis of chitin from shell of crustaceae.

Effective against bacteria,yeast &

molds.Mode of action:

Causes destabilization of cell wall and cell

membrane functions.

Ethylenediaminetetraacetate(EDTA)

Inhibitory for germination & outgrowth of spores of c.botulinum.

Mode of action:EDTA may not have much antimicrobial effect, but because of its ability to chelate

divalent cations, it can destabilize the barrier functions of the outer membrane of Gram-negative bacteria and, to some extent, the

cell wall of Gram-positive bacteria.

Present in large quantities in some foods such as egg white and shellfish (oysters), as well as in small amounts in milk and some plant tissues.

Used in wine (sake) to prevent growth of undesirable lactic acid bacteria.

Mode of action: It hydrolyzes the mucopeptide layer present in the cell wall of Gram-positive bacteria and in the middle membrane of Gram-negative bacteria

Lysozyme

Monolaurin(glycerol monolaurate)

The ester of lauric acid and glycerol, is one of the most effective bactericidal agents.

Its effectiveness in deboned meat, chicken sausages, minced fish, and other foods has been observed against undesirable bacteria, particularly the anaerobes.

It enhances the thermal inactivation of spores of Bacillus spp.

In combination with monolaurin, the fungistatic activity of several antifungal

compounds is enhanced

The antimicrobial activity of monolaurin is produced through its ability to

destabilize the functions of the membrane.

Stop or kills the microbes that cause spoilage of food. Used to preserve cheese. Used in feed given to food animals. Mostly following are used: Netamysin Tetracycline Tylosin

Antibiotics

Tetracycline was approved by FDA to

extend the refrigerated shelf life of seafood and

poultry in the 1950s. However, because of the

possible increase in antibiotic-resistant

bacteria, use of these antibiotics in food was

later banned.

Natamycin, a microlid produced by

Streptomyces natalensis, is an

antifungal agent. Its use as a dip or spray to

prevent growth of molds and formation of

mycotoxins on the surface of some cheeses,

sausages, and in raw peanuts.

Tylosin, a microlid that inhibits protein synthesis, is a bactericidal antibiotic that

is more effective against Gram-positive than Gram-negative bacteria and also

inhibits outgrowth of germinated endospores.

Contain chemicals that deposited on food:

formaldehydePhenolsCresols

Smoking can be bactericidal, bacteriostatic, antifungal.Depending on temperature,time, degree of surface drying, & concentration.

Wood Smoke

It include cinnamic aldehyde in cinnamon; eugenol (2- methoxy-4-allyl phenol) in cloves, and paramene and thymol in oregano and thyme. Their bacteriostatic and fungistatic properties depend on the active agent.

Mode of action:Forms a layer over a food product & hence it forms a layer between air & microbe and restrict them.

Spices

Benzoic acids• Used in acidified food• inhibit function of enzymes and membrane

protein ,destroy membrane potential.

Propionic acid• Used in bread,bakery products etc..• causes acidification of cytoplasm,

destabilization of membrane protein

Sorbic acid• Effective against molds and yeasts.• Interferes with synthesis of cell

wall,protien,RNA,DNA.Inhibit spore germination.

Broad spectrum Used in alcohlic beverages,jams, pickles, salad

dressing,mustards etc. Mode of action: inhibit function of enzymes. Interfere with transport of nutrients by binding with

lipids. Interfere with synthesis of proteins,RNA, DNA. Destroy membrane potential.

Parabens

Broad spectrum. Mostly used in dairy products. The antibacterial action is probably produced by

deactivating some important enzymes. The dicarbonyl group (–CO–CO–) reacts with arginine in the enzymes and modifies their catalytic sites.

Diacetyle

A number of chemical compounds are being used in food preservation that kill or retard the microbes.So,the food spoilage reduces due to the presence of these compounds.The concentration of these chemicals varies in different food products.These chemicals are approved by regulatory agencies.These chemicals must be harmless.

Conclusion