15 - chemical preservatives Flashcards
What are the two classes of preservatives
- traditional
2. naturally occuring
What are preservatives ?
chemicals that are added to foods that retard the growth of or kill microorganisms. (most of them do not kill they are bacteriostatic)
Traditional preservatives:
1-Have been used for many years
2-Are approved for use in many countries
3-Are produced by synthetic processes
What are the traditional antimicrobial we saw in class
1- organic acids 2- Dimethyl bicarbonate 3- lactoferrin 4- lysosyme 5- nitrites 6- para-hydroxybenzoic acid esters 7- sulfites
___ (weak/strong) organic acids are more effective
weak
The best acids for preservatives are ___protic acids
mono
What are the monoprotic acids seen in class
1- acetic acid 2- propionic acid 3- lactic acid 4- sorbic acid 5- benzoic acid
what are the multiprotoic acids seen in class
1- citric acid
2- malic acid
3- tartaric acid
4- fumaric acid
What are the consideration you need to take when choosing an acid as a preservative
1- pKa value
2- pH of the food
What is the maximal pH foods need to be for the organic acids to have a preservative effect
food needs to have a pH under 5.0
What is acetic acid more effective on?
more effective on yeasts and bacteria than on molds
Why is acetic acid added to breads?
can reduce the ropiness produced by bacillus subtilis
T or F : acetic acid is only used for spoilage microorgnisms
false, it is also used for safety in the poultry processing for the reduction of the salmonella
Benzoic acid is most effective against what kind of microorganisms
most effective against fungi (molds)
What are the common use of benzoic acid
reducing E.Coli
reducing molds in grape juice
What is the use of lactic acid
used on carcasses to reduce the microbial load
What is sorbic acid effective against ?
fungi, bacteria and most yeasts
What are the common use of sorbic acid
inhibtion of fungi in bakery products
salad dressing
what is dimethyl dicarbonate effective against?
yeasts but can also be bactericidal
What is the mechanisms of dimethyl dicarbonate
leads to enzyme deactivation
What is the common use of dimethyl dicarbonate
used in the alcoholic beverages like apple cider or wine
What is lactoferrin effective against
bacteria
What is the mechanism of lysozyme?
it is a peptidoglycan hydrolase that will hydrlyse the bonds in the cell wall and result in cell lysis.
What is the common use of lysosyme
cheese to prevent the fermentation and production of CO2 by anaerobe C. Tyrobutyricum
What are the other use of nitrites in meat products other than preservation?
- nitrosomyoglobin production and pink colour
- yummy taste of cured meats
The primary application of nitrite is for the inhibition of
C. botulinium
what is the mechanism of nitrites?
work by inhibiting the ability of bacterial cells to generate ATP (depletion of the energy stores).
What are nitrites effective against?
bacteria
What is used in combination of nitrites
sorbic acids
What are parabens effective against?
against fungi and gram positive bacteria
What is the mechanism of action of parabens
interference with the electrochemical graident
What are the common use of parabens?
- beers, fruit juices and soft drink to inhibit the fungal growth
- used in baked goods
- wine
- pie fillings
T or F : the use of parabens is really common in the food industry
true
Why do you see parabens more often in low Aw products
because they are effective against fungi
what are the common use of sulfite ?
frutis and vegetables products
Which preservative are we referring to : They also have antioxidant properties that inhibit the enzymatic and non-enzymatic browning of foods
sulfites
what is the downside pf the naturally occuring preservatives
- they lead to adverse sensory changes
- a the concentration they are found they don’t inhibit the microbial growth
What is the downside of the lactoperoxidase system
to use it you need to add extra hydrogen peroxide
What is chitosan effective against?
fungi and bacteria (even more if combined with other organic acids and antimicrobial)
What is the supposed mechanism of chitosan
chelation of the ions associated on the LPS
What is the source of chitosan?
from the chitin of the shrimps
The greatest antimicrobial activity of spices comes from
cloves, cinnamon, oregano, thyme and to a lesser extent sage and rosemary
Cinnamon and cloves contain __ and ___
eugenol and cinnamic aldehyde
What is cinnamon active against?
bacteria, fungus and yeasts
Allicin is effective against the growht and production of toxin of ___
clostridium bottulinum
Onions also produce ____ which may also contribute to the antimicrobial activity of onion essential oils and extracts
chain phenolic compounds (catechol)
What is the mechanism of allicin
oxidation of thiol groups to disulfide, so it inhibits the disulfide contining enzymes
What are hops effective against ?
bacteria and fungi
What part of the hops is antimicrobial?
the resin formed by it is composed of bitter acids
T or F : hopping is noly effective if used in combination with low Aw
true
What are isothiocyanate effective against
yeast, fungi and bacteria
