part 3b Jan 27th Flashcards
- Nitrites
Food Uses and Concentrations (legal)
- nitrites are used in meats, fish and poultry products (e.g. bacon corned beef, hot dogs, luncheon meat, ham); approved for use since 1925
- typical levels: bacon (120 ppm); sausage (100 ppm); cured meats (156 ppm); canned products (50 ppm); other products typically have a 200 ppm maximum level
- Nitrites
Toxicity
- LD50 (oral, rats): 180 mg/kg bwt
- lethal dose (humans): 32 mg/kg bwt
- estimated human consumption: 3.5 mg/day (based on production)
- doses of 1-2 g KNO2 /day or in drinking water (2-3% NaNO2) for 10 months (hens/mice/rats):
- reduction in motor activity - leg weakness and chronic muscular spasms - cardiac and pulmonary damage - high incidence of infant mortality
- FDA lymphocyte study (rats): possible link to the induction of cancer tumor incidence in treated rats was 61% compared to 18% in the control group ( 5000 ppm levels in drinking wateré14weeks)
Nitrites
role of nitrites
Role of nitrites:
NaNO2 + H2O HNO2 (nitrous acid)- major microbial that is present 3HNO2 2NO (nitric oxide- inhibits ferrodoxin)- + H2O + HNO3 (nitric acid)
Mb +NO –” MbNO (nitroso hemochrome; reddish colour of cured meat –” colour boost + flavor
Protects from botulinim and boost of red colour
Risks vs Benefits
dimethlynitrosamines
- LD50 for dimethylnitrosamine: 30 mg/kg bwt
- estimated exposure from foods: 0.1 μg/day
- estimated intake from cigarette second hand smoke: 17 ug/day
- estimated exposure from beer: 0.3 μg/day
- estimated exposure from cosmetics: 0.4 μg/day
WHO 2015 “consumption of red meat as probably carcinogenic to humans” ; “processed neat was “carcinogenic to humans “ (colorectal cancer)
Nitrate: Intake( NaNO3), synthesis and exposure
Intake (nitrate) day:
Vegetables: 92mg Fruits: 4.6 Water: 14mg Baked goods: 1.2mg Cured meats: 1.2 mg
Total: 113mg
- NitritesConversion (reduction) of nitrate to nitrite by bacteria in the mouth and GI tract:
- assume a 25% conversion rate (20-50% is normal), then we assume about a 24mg/day of nitrite from vegetables and fruits
- has been shown that nitrosamines/nitrosamides can be formed in the stomach
- Nitrites
Risks vs Benefits
What has the food industry done?
- limited use to the lowest level required to control the growth and toxin production by Clostridium botulinum
- serendipitous finding: ascorbic acid or erythorbic acid inhibits nitrosamines formation (addition of this compound to cured meat is required in USA and allowed in Canada)
- Sulfites
comprises a group of sulfur containing compounds:
- SO2 (sulfur dioxide) - Na2SO3/K2SO3 (sodium/potassium sulfite) - NaHSO3/KHSO3 (sodium/potassium bisulfite) - Na2S2O5/K2S2O5 (sodium/potassium metabisulfite)
- industrially produced (i.e. chemical synthesis):2SO2 + Na2CO3 + H2O 2NaHSO3 + CO2
- Sulfites
used to ‘stabilize’ (preserve) wines (27 B.C.)
- food carts burned sulfur to ‘stabilize’ (preservative and fumigant) bread, fruits, meats and vegetables (1600–1664)
- naturally present in: vegetables (e.g. garlic, onion, broccoli, cabbage, asparagus), fermented products (e.g. cheese), nuts (e.g. peanuts), fruits (e.g. strawberry, raspberry, plums), eggs, tea, maple syrup, etc.
- Sulfites
Physical Properties
water soluble compounds (e.g. Na2SO3: 28 g/100 mL; KHSO3: 100 g/100 mL)
- available (salts) in solid and liquid forms
- colourless and odourless (exception is SO2)
Activity Spectrum
- inhibits yeasts, moulds and bacteria ()
- used to control acetic acid and malolactic bacteria (responsible for: fermentation, spoilage, surface mould) in fresh fruits and vegetables
Mechanism(s) of Action
- Undissociated H2SO3 (sulfurous acid) is reported to be the only form of sulfite that has antimicrobial activity (i.e. food pH <4.0)
SO2 + H2O H2SO3 (sulfurous acid)H2SO3 HSO3- (bisulfite) + H+ H2SO3 SO- SO3- (sulfite) + 2H+
- undissociated H2SO3 is reported to be the only form of sulfite that has antimicrobial activity
what is the major antimicrobial sulfur
H2SO3 sulfurous acid
- Sulfites
Mechanism(s) of Action
- microbial inhibition results from the interaction of sulfurous acid with the sulfur bridge(s) of structural proteins (i.e. enzymes), and chemical reactions (SO3-) with co-factors/vitamins (thiamine [Vit B1] destruction; essential co-factor for several fermentative enzymes)
- acts as a reducing agent
-s-s- -> -SH hs
SULFUR BRIDGE
- Sulfites
Food Uses and Concentrations (legal)
- SO2 and its salts have GRAS status (lost it and then got it again)
- approved levels of 0.015-0.25%
- solutions (0.1-0.2%) sprayed on fresh fruits and vegetables
- vapourized SO2 solutions are used to treat fruits prior to dedhyration (e.g. raisins; increases storage life, preserves colour and flavour) up to 2000 ppm total SO2
- select food usage: wines (up to 350 ppm), grape/fruit juices (10-100 ppm), fresh shrimp (50-200 ppm), processed meats (up to 450 ppm)
- ADDED TO FRESH MEAT In EU TO RESTORE COLOUR (NOT ALLOWED IN Canada)added to meat to control colour- puts iron in the fe2 so that it can bind to oxygen
used to be in the spray water in grocery stores - used to sanitize food processing equipment
. Sulfites
Toxicity
- LD50 (oral, rats): 1000-2000 mg/kg bwt
- humans: SO2 induces vomiting (fatal dose unlikely)
- no cmta
- sulfites destroy thiamine [SO3-)
- sulfites may boost asthma symptoms (wheezing, tight chest and coughing) [Vally, H. and Thompson, P. 2001. Thorax 56:763-769]
- 1981 study (Stevenson, D.D. and Simon, R.A. 1981. J. Allergy Clin Immunol 68:26-32) linked sulfite consumption to an “allergenic” response in asthma patients -> ban on use (USA) in 1986 (raw fruits and vegetables and a 2-year time limit for use in the food industry)
- ban lifted in 1987 based on FASEB (Federation of American Societies for Experimental Biology 1985 study: “sulfites posed no [health] hazard to most Americans”) requirement that all foods containing sulfites be clearly labelled( 4-5% of americans have athmas- 1% of them got effected
- FDA (1987) proposed to revoke GRAS status for sulfiting agents in potatoes/products rule was held null and void in 1990 (supreme Court) [ politics trumps science?”
polyphenol oxydase- polymerase cut fruit to brown colour- sulfites stop enzymatic browning, chemical browning (on bread) can also stop that a litle bit
- Biologically-derived Antimicrobials (‘Natural’)
A.Nisin (Nisaplin)
polypeptide (lantibiotic; comprised of 34 amino acid residues; molecular mass of ~3500 daltons) produced by Lactococcus lactis
Thiolo either- surfuring – will be mainly talking about nicin a
- naturally present in dairy products (Z variant; e.g. 10-50 ppm)
- industrially produced (A variant) via fermentation
Physical Properties
- water/food solubility is pH dependent: 5700 ppm @PH 2.0; 2000 ppm @ PH 5.0 (insoluble: ph > 6.8)
- stable as a solid (dry state; years) and at refrigerated temperatures (4 oC); slowly loses activity when added to food
- nisin isunstable at high temperatures (i.e. normal thermal processing of foods)- limitation – can’t reheat so for low processing foods
bacteriocin: !!!!!!
protein/polypeptide produced by a bacteria that kills or inhibits the growth of the same or related species
A. Nisin (Nisaplin™)
Activity Spectrum
- effective against a range of gram positive (Gram +ve) bacteria species that are responsible for food poisoning; as examples: Staphylococcus aureus, Bacillus cereus and Clostridium perfringens and botulinum (i.e. bacteriocin: protein/polypeptide produced by a bacteria that kills or inhibits the growth of the same or related species
- also effective against the following gram negative (Gram -ve) pathogens (disease causing microorganism) when used in conjunction with a chelating agent (e.g. EDTA): E. coli, Salmonella, Shigella
A. Nisin (Nisaplin™)
Mechanism(s) of Action
- destroys the integrity of the cytoplasmic membrane generates pores (amphiphile) resulting in leakage of cellular materials (e.g. amino acids, cations) coupled with an influx of anions and cations into the cell
- inhibition of cell wall synthesis (i.e. enzyme inactivation)
- reduces the heat resistance of spores (cell wall) - very hard to kiill
A. Nisin (Nisaplin™)
Food Uses and Concentrations (legal)
- approved for use (A and Z variants; 100-250 ppm levels) in the USA and EU (+50 other countries) for: dairy products (e.g. eggs, milk, cheese), canned foods, baby foods, etc.
- not approved for food use in Canada-> (?) can be in foods imported into Canada and is naturally present in our own dairy products
- limitations?
A. Nisin (Nisaplin™)
Other Uses (legal)
- active ingredient in diaper wipes (Nutrition 21)
- pharmaceuticals (peptic ulcer disease: Helicobacter pylori)
- medical devices (surface treatment to combat microbial biofilms- dentist office tools)
- veterinary medicine (topical treatment for mastitis)
- Biologically-derived Antimicrobials (‘Natural’)
A. Nisin (Nisaplin™)
Toxicity
- LD50 (oral; mice): 6950 mg/kg of bwt (similar to that of NaCl)
- Lactococcus spp are GRAS
- naturally present (Z variant) in dairy products
- no cmta
- no current cross-resistance to thetherapeutic antibiotics
- nisin is rapidly (<24 hrs) inactivated in the human GI
- ADI: 0.83 mg/kg bwt (USA); 0.13 mg/kg bwt (EU); (estimated intake: 0.06 mg/kg bwt; USA; based on maximum permitted levels)
natamycin
macrolide (antibiotic produced by a bacterium that contains a macrocycli lactone ring/cyclic ester produced by the bacterium streptomyces natalensis
- industrially produced via fermentation
physical properties
white/off-white solid; tateless and odourless
low water solubility (30mg/L); very pH (3.0-9.0) and heat stable (100c)
activity spectrum
-effective agaisnt yeast and molds
Mechanism(s) of Action
- incorporation into the cytoplasmic membrane (membrane sterol binding) pore formation (cellular content leakage and death) and/or ergosterol (specific) binding (loss of essential membrane enzyme function(s))
B. Natamycin (Natamax™, Pimaricin)
food uses and concentration (legal)
approved for use in canada /USA for cheese as a surface treatment at a maximum concentration of 20ppm
has been used extensively in the EU for 35 years (approved for use in more than 150 countries): bakery and dairy products, processed meats, wine (6-40 ppm levels)
other uses
-topical drug (fungal eye infection) and for medical devices
