antimicrobial preservative
TRANSCRIPT
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