Industrial toolkit 1 Flashcards
How to control microorganisms in food!
What is a processing aid?
Substance that is used for technical effect in food processing. Does not affect intrinsic characterics of the food, and often not detectable.
Differences of food additive and processing aid
Food additive: affects characteristics of food, part of food and must be on the label.
Processing aid: NO impact on food characteristics, NOT apart of food, no label declaration and often hard to notice.
What is the application of chemical preservatives?
- Minimize health risk.
- Improve nutritional quality
- enhance storage life
- Improve sensory properties.
What is sued for a chemical?
As long as it can inhibit, retard, or arrest decomposition of food.
Add component directly or indirectly to food.
Impairs deterioration by microorganisms.
Positives of chemical preservatives?
Very versatile.
-Apply directly to food (Acid)
- Applied to packaging material (mould inhibitors)
-Can be used in water for washing foods (chlorine for veggies)
- Can be added via microorganisms
INDIRECT ADDITION.. biopreservation.
Acids: Added directly to food. What is the function? What are commonly used?
Function: flavor, pH modification
acetic and lactic acid most common
How do acids work? FIX
pH: log of H ions present
pKa: log of acid dissociation
pH=pKA half is dissociated. @ equilibrium.
WANT acid with pKApH acid will resist dissociation and pH uneffected.
Undissociated acid can enter cell and break enzymes.
What microorganisms are vulnerable to acids?
bacteria, yeast and mold.
Organic acids (acetic and lactic acid)..tell me about them..FIX
produced naturally during fermentation.
pKa
Nitrates importance in food?
Important for food preservation and safety..especially in meats. Adds color and flavor.
What microorganism is inhibited by nitrate?
Inhibits outgrowth of endospores C. botulinum
What are the allowable limits of nitrates?
200ppm is max,
120ppm in baction. (AA mix with nitrite and cause carcinogens)
100ppm in processed meats.
“rate of addition” never found in cooked meats.
How does Nitrite work?
Cells of Clostridium botulinum contain IRON-SULFUR proteins.
Reacts with added nitrite to form iron nitric oxide complexes. This causes destruction of the iron sulfer clusters in enzymes, inactivation of enzymes and growth is inhibited.
Active form is nitrous acid HNO2 (pKa 3.4)
Does increasing activity increase when pH is decreased or increased?
Activity increases when pH decreases.
pH >7.5 growth of microorganism
pH 6-7 slight inhibition
pH 5.5-6 some inhibition
4.5-5.5 definite inhibition. (pH of processed meats)
pH <4.5 HNO2 decomposes and pH inhibits bacterial bacterial growth.
Common use of nitrate/nitrite?
Processed meats
- Perigo factor (heat + nitrite) 10x increase
Perigo factor is antibacterial factor produced when heat is added to nitrite.
Meat decreases perigo.
With added antimicrobials increases effeciency…less nitrite needed.
ex.
nitrite + erythorbate
nitrite + sorbate
What is the risks of nitrite?
carcinogen when nitrite + free amine group.
What is the benefits of nitrite?
Controls C. botulinum spores.
Nitrate in celery powerder
Must be declared by the manufacturer. Min level is 100ppm. and max is 200ppm.
What about natural nitrates?
Not as much control in “natural” nitrates. Nitrate must be converted to nitrite to have microbial effect.
Why do we use sulfites in the food industry?
inhibit bacteria, yeast and mold growth. ( found in wines, fruit juices, not allowed in meat b/c destroyed B1)
When are sulfites more effective?
When used in low pH, used to be sprayed on salad bars but now considered an allergin.
Natural antimicrobial agents
Consumer perception, natural is better.
ex. Lysozyme
avidin found in eggs.
garlic and onions (allicin)
BioPreservation..what is it?
exend storage life and enhance safety of foods using the natural microflora and antibacterial products.
What is the application of biopreservation in the food?
- use bacterial strains.
- Add purified substance
- add fermentation liquor or concentrate.
antimicrobial compounds in LAB
- Organic acids ( lactic and acetic acid) decrease pH
- Hydrogen peroxide H2O2
- CO2
- diacetyl (flavor of butter)
- Bacteriocins (antimicrobail peptides)
Bacteriocins what are they?
Antibacterial peptides or proteins from bacteria
What is the purpose of bacteriocins?
kill or inhibit grow of closely related bacteria. Narrow activity.
Classes of bacteriocins
class I (lantibiotics) nisin
- small, heat stable peptides.
- extensive post-translational modification
class II (nonlantibiotics) pediocin, leucocin
- small, heat stable, hydrophobic peptides
- limited post-translational modificatons
Class III
large, hydrophilic proteins
class IV AS-48 carnocyclin
circular bacteriocins
What can nisin kill? class I
Listeria spp. C. botulinum, Staph. Aureus NOT gram negatives.
What are the benefits of bacteriocin producing LAB?
Natural (consumer acceptance)
production of bacteriocins in food (throughout shelf life)
- Additional hurdle for safety.
- potential replacement ofr chemical preservatives
Biosynthesis of bacteriocins…must have?
Must have structural genes (immunity genes)
May require: transport genes (modifation and regulation genes)
Class i: Lantibiotics
Ribosomally synthesized, produced as pre-petides, and undgergo post-translational modifcations.
A little about Nisin
liscensed in over 50 countries.
Produced by Lactococcus lactis susp. lactis
What is the application of Nisin in food?
UHT milk, canned veggies, pasteurized processed cheese, dariy and liquid egg products.
what causes the inactivation of nisin?
reactions with surfaces and meat components. Poor solubility, sensitivte to food enzymes, high bacterial loads (like growing by itself), interaction with phospholipids, and poor distribution throughout the product.
Class II nonlantibiotics
Micocin: commerically available. from carnobacterium maltaromaticum. prodcues three bacteriocins.
What does micocin do with L. monocytogenes
It decreasese the log numbers increasingly. Overcomes hurdles.
Plant extracts as antimicrobials: 2 popular ones
1. Allyl isothiocyanates: mustard/horseradish inhibits bacterial growth on foods E.coli uncooked ham Listeria ground beef Salmonella- ground beef or adds flavor. 2. Rosemary extract. strong flavor acts as antioxidant and antimicrobial.
