| Organic acids: antimicrobial mode of action | inhibition of microbial metabolism due to:
- acidification of the cytoplasm
- protein denaturation
- inhibition of protein synthesis
- inhibition of enzyme activity
- diffusion of proton motive force
- inhibition of nutrient transport |
| Organic acids: antimicrobial mode of action | inhibition of microbial metabolism due to:
- acidification of the cytoplasm
- protein denaturation
- inhibition of protein synthesis
- inhibition of enzyme activity
- diffusion of proton motive force
- inhibition of nutrient transport |
| Antimicrobial preservatives: factors to consider with food use | - antimicrobial properties: antibacterial, anti fungal ?
- suitability for food use: generally regarded as safe, sensory changes ?
- regulatory requirements: allowable levels, restrictions ? |
| Nitrite (NaNO2 and KNO2): applications | - used as curing salts in heat-processed meats, poultry, and fish products
- prevents Clostridium botulinum growth and toxin production
- provides attractive cured meat color (pink) |
| Nitrite: mode of action | - interacts with iron-sulfur enzymes (ferredoxin, hydrogenase) to prevent ATP synthesis
- lactic acid bacteria lack ferredoxin and are resistant to nitrite |
| Nitrite: limits/health impacts | - US regulatory limit: 156 ppm of NO2
- in bacon, nitrate + secondary amine = nitrosamines (carcinogenic)
- Perigo factor: heating medium with NO2 produces a factor that is 10X more inhibitory than NO2 alone |
| Sulfur dioxide (SO2) and sulfites (SO3): applications | Forms used: sulfur dioxide (SO2), sodium sulfite (Na2SO3), sodium bisulfite (NaHSO3), sodium metabisulfite (NaS2O5)
- control of microbes and insects in soft fruits, fruit juices, beverages, wines, pickles, sausages, fresh shrimp |
| Sulfur dioxide and sulfites: limits/health impacts | - US regulatory limit:200-300ppm for antimicrobial use
- more effective against yeast and molds than bacteria
- not permitted in meats
- some peoples (esp. those w/ asthma) are allergic to sulfites --> addition must be stated on food labels
- destroys vitamin B1 |
| Sulfur dioxide and sulfites: antimicrobial mode of action | - enzyme inhibition
- sulfurous acid enters cell and reacts with thiol group of proteins |
| Hydrogen peroxide (H2O2): uses and limits | - 0.05 to 0.1% recommended as antimicrobial agent in raw milk and liquid egg
- 30-50% used to sterilize food containers (aseptic packaging) and equipment surfaces
- heating H2O2 to 150-160F can reduce treatment time |
| Hydrogen peroxide: antimicrobial mode of action | - strong oxidizing effect
- membrane and DNA damage |
| Epoxides (ethylene oxide and propylene oxide): applications | - fumigants to destroy microorganisms and insects in grains, spices, nuts, cocoa powder, dried fruits, and packaging materials
- effective against vegetative cells, spores, and viruses
- ethylene oxide is more effective |
| Epoxides: antimicrobial mode of action | - enzyme inhibition
- react with groups (- SH, - NH2, and - OH) in cellular macromolecules |
| Organic acids: applications | - acetic, propionic, lactic, citric, benzoic, and sorbic acids
- used in a variety of foods as acidulants
- acetic: pickles, salad dressings, sauces
- lactic: salad dressings, pickled vegetables, carbonated beverages, heat processed meats |
| Acidulants | substance, like organic acids (acetic, propionic, lactic, citric, benzoic, and sorbic), used as food additives that act as control agents to alter food pH levels in beverages/sweets or to serve asl evening agents for breads |
| Organic acids: factors regarding use in foods | - difference in pKa (pH at which acid is 50% dissociated) --> variations in antimicrobial effectiveness, HA form of the acid provides the greatest antimicrobial effect
- solubility of the acid
- variation in lipophilic properties (short chain lipophilic acids ex. acetic/ lactic/ sorbic --> cross the cytoplasmic membrane & acidify the cytoplasm, more effective antimicrobials) |
| Organic acids: antimicrobial mode of action | inhibition of microbial metabolism due to:
- acidification of the cytoplasm
- protein denaturation
- inhibition of protein synthesis
- inhibition of enzyme activity
- diffusion of proton motive force
- inhibition of nutrient transport |
