Part 3b Flashcards
colour and form of nitrities?
white to pale yellow crystalline; solid and liquid forms
nitrites come in these two forms
sodium nitrite, potassium nitrite
nitrites water solubility?
100%!
nitrites involved in this flavour response
salt
how produce nitrites?
industrially by rxn nitrogen oxides with alkaline solution
what are nitrites primarily used for?
inhibit growth of clostridium botulinum in processed/cured meats
antimicrobial activity increases as ____ increases
alkyl chain length
what to watch out for with nitrites?
explosive
what are mechs of action for nitrites?
enzyme inhibition, cell mem damage/destruction
example of enzyme inhibition?
ferridoxin involved in many metabolic rxns as electron carrier, via iron oxidation from Fe2+ to Fe3+ (loss of electron carrier and transfer ability by nitric oxide)
cell membrane damage caused by _____
nitrous acid (major active compound of nitrites)–>affects permeability/leakage
do nitrites have GRAS status?
no
what is max level of nitrites in most?
200ppm
how is nitrites diff form others in terms of toxicity?
more lethal for humans than rats (this is rare)
having 2-3% diet as NaNO2 over 10 months caused:
decrease motor activity, leg weakness and chronic musc spasms, cardiac/pulmonary damage, ^ incidence infant mortality
FDA lymphocyte study showed:
possible link to induction of cancer (^ tumour incidence)
why industrial resistance to eliminating use of nitrites?
colour and flavour
___ has iron in the Fe2+ oxidation state, and in the presence of reducing agents (abundant in meat) oxidized to Fe3+, resulting in ____
myoglobin (purple); MetMb (brown-grey)
Mb+NO–>MbNO which contributes to:
reddish colour of cured meat (colour boost and flavour), NO also inhibit ferridoxine
daily intake of nitrates or nitrites higher?
nitrates
how convert nitrates to nitrites?
bacteria in mouth and GI tract (about 25% conversion)
nitrosamines/nitrosamides can be formed in the ___
stomach
___ inhibits nitrosamine formation
ascorbic/erythorbic acid
comprises a group of sulfur containing comps that are industrially produced
sulfites
sulfites naturally found in:
veg, fermented products, nuts, fruits, eggs, tea, maple syrup
sulfites used to stabilize ___
wines (since 27 BC), bread, fruits, meats, veg (since 1600s)
physical properties of sulfites?
water soluble, available in solid and liquid forms, colourless and odourless
exception to being colourless/odourless sulfites?
SO2 in winemaking
sulfites inhibit ___
yeasts, moulds, bacteria
sulfites used to control ____ bacteria in fresh fruits and vegetable
acetic acid/malolactic bacteria
only form of sulfite that has antimicrobial activity?
undissociated sulfurous acid (H2SO3)
in water, regardless of which sulfite you start with, you will get ___
sulfurous acid
mech of action for sulfites?
interaction of sulfurous acid with sulfur bridges of structural proteins, and chem rxns of SO3 with cofactors/vitamins
example of chem reaction with cofactors/vitamins?
thiamine destruction–>cofactor for several fermentative enzymes
sulfites act as ___ agent
reducing (break sulfide bridges)
do sulfites have GRAS status?
yes, was taken off but now back
how are sulfites used?
sprayed on fresh produce, vapourized solutions used to treat fruits before dehydration, wines, juices, shrimp, processed meats, sanitize equipment
why treat fruits before dehydrating?
^ storage life, peserve flavour and colour
what are sulfites added to in EU, and why?
fresh meat, restore colour
sulfites may boost :
asthma symptoms
examples of biologically derived antimicrobials?
polypeptide (lantibiotic) produced by lactococcus lactis, nisin
what is nisin?
naturally present in dairy, industrially produced via fermentation
industry nisin is ___, natural is ___
A; Z
phys properties of nisin?
water/food sol. is ph dependent
nisin is stable as ____ and at ___ temp
solid; refrigerated
nisin unstable when?
high temp, also lose activity when added to food
what is activity spectrum of nisin?
range of gram positive and also gram neg. like e. coli, salmonella, shigella when used with chelating agent
what is bacteriocin?
protein/polypeptide produced by bacteria that kills/inhibits growth of same or related species
example of chelating agent?
EDTA
what is mech of action for nisin?
destroy cyto mem by making pores resulting in leak of cell materials coupled with influx of anions/cations, inhibits cell wall synth thru enzyme inactivation, reduce heat resistance of spores
nisin approved for use in ____ but not in Canada
dairy, canned, baby foods
nisin usage in things other than food:
diaper wipes, pharmaceuticals (for peptic ulcer disease), med devices, vet. medicine (mastitis)
Are Lactococcus species GRAS?
yes (rapid inactivation in human GI)
