part 3b Jan 27th Flashcards
1
Q
- Nitrites
Food Uses and Concentrations (legal)
A
- 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
2
Q
- Nitrites
Toxicity
A
- 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)
3
Q
Nitrites
role of nitrites
A
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
4
Q
Risks vs Benefits
dimethlynitrosamines
A
- 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)
5
Q
Nitrate: Intake( NaNO3), synthesis and exposure
Intake (nitrate) day:
A
Vegetables: 92mg Fruits: 4.6 Water: 14mg Baked goods: 1.2mg Cured meats: 1.2 mg
Total: 113mg
6
Q
- NitritesConversion (reduction) of nitrate to nitrite by bacteria in the mouth and GI tract:
A
- 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
7
Q
- Nitrites
Risks vs Benefits
What has the food industry done?
A
- 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)
8
Q
- Sulfites
A
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
9
Q
- Sulfites
A
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.
10
Q
- Sulfites
Physical Properties
A
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)
11
Q
Activity Spectrum
A
- 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
12
Q
what is the major antimicrobial sulfur
A
H2SO3 sulfurous acid
13
Q
- Sulfites
Mechanism(s) of Action
A
- 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
14
Q
- Sulfites
Food Uses and Concentrations (legal)
A
- 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
15
Q
. Sulfites
Toxicity
A
- 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
