lecture 8-saftey and adverse effects Flashcards
what makes a substance toxic?
if it is consumed in a quanity/[]/under conditions that have or may have immediate or long term harmful effects to the body
what is LD50
it is the dose that will kill 50% of animals in the test series
what are the three levels of toxicity?
- acute toxicity: eat something→ symtpoms within 1 hour to day
- subacuate toxicity: symptoms develop within 2-4 weeks after consumption
- chronic toxicity: this results in long term health consequences
what is ADI
the acceptable daily intake, is the maximum level of daily intake of a toxic substance.
define natural toxins
these are toxins that are produced by living organisms that are not harmful to themselves. but other toxic to others when eaten. The chemicals have a diverse function, structure and level of toxicity.
gram positive and gram negative bacteria produce different toxins, what are they?
gram positive: produce exotoxins which are mainly protiens. They are heat stable
gram negative: produces endotoxins which include protiens and other components in their structre. They are bound to cell wall and are released upon disrubtion
give an example of a gram negative and positive bacteria which produces toxins
- positive: clostridium botulinum (neurotoxin)
- negative: e. coli
what are methods to prevent bacterial intoxication?
- thermal treatments: inactive cells, and spores, denature toxins (remember exotoxins are resistant)
- adicification
- low water activity
- antimicrobial additives
plant toxins a form of natural toxins are called?
secondary metabolites which are compounds made by organisms that are not essential to their growth or reproduction
what are endogenous toxins?
toxic substances which are naturally present in a food item
what are lectins?
They are a substance contained in many pulses, it only takes a few raw beans to cause serve gastrointestinal issues. They bind to red blood cells. Not to fear tho lectins can be destroyed when soaked and boiled
what are protease inhibitors
Released by plants in response to damage or infection. They block active site of protease and form a very stable complex which results in reduced protien digestion rate and reduces the quality of protien
describe kuntiz soybean trypsin inhibitor
KTI forms a highly stable non covalent complex with active site of trypsin making the enzyme inactive. The binding that happens is irreversible
Describe bowman brik soybean proteinase inhibitor
Binding sites for both trypsin and chymotrypsin forming tight binds, it is reversable though, so it basically delays digestion. The big problemw with this inhibitor is that is is very heat, and acid and base stable
what are the physical processes to inactivate inhibtors
- thermal
- extrusion
- ultrasound: sound waves with a high frequency cause unstable blubbles in liquid which disrupt peptide structure
- ultra filtration: removes small molecular weight peptides
- soaking: increase moisture→ smaller molecular weight and more water soluble
what are the chemical processes to inactivate inhibitors
- reducing agents: break dislfide bonds and stable 3 structure
- acids and bases: destabilize intramolecular electrostatic bonds and stabilize 3 structure
what are the biological processes to inactive inhibitors
- germination: through germination the enzymes in the seeds come out and hydrolyze protiens
- fermentation
what is avidin?
a glycoprotien present in egg which binds biotin
what is a food allergy and how is it caused?
an unsual immune response to food protiens. This happens because immunoglobulin E binds to specific amino acid sequence in protien (epitopes)
what are the two types of epitopes?
- continous (sequential-from sequence)
- discontinous (conformational-from structure)
in simple words what is the development process of allergic reactions?
- sensitization: allergen is recognixed by cells like dendrtitic cells which activates T-cells -> which stimulates B cells and they will differantiate and produce IgE antibodies these will bind to receptors on mass cells and basophils and now they are primed and ready to react at subsequent exposures
- re-exposure: at a later exposure the allergan will bind to the antibodies on the mast cell, which will cross link and activate the mast cells which will release inflamtory things like histamine, from here a cascade of reactions will result in the allergic symptoms
what are the identification tests for allergens?
- skin prick tests or oral food challangen: this is where the patient is exposed to the known allergen epitopes and observe if they have a reaction
- ELISA assay: uses antibodies to bind the allergen in a sample, followed by an enzyme-linked reaction that produces a measurable color change. The intensity of the color indicates the allergen concentration. Normally done in for food but can be done in people, by taking a blood sample and seeing if it binds.
whats the difference between contains and may containg warnings?
- contains: list of common allergans known in the product
- may contain: is a list of allergans which may have enterted the product
which method can get rid of allergens
None literally none, the only real solution is to complete exlude it
what are methods that can reduce allergencity
- thermal treatment
- ultrasound
- high pressure treatments
- gamm irradation
the principle behind all these methods is that it induces structural changes in protiens which disrupts or destroys the IgE epitopes
what is the difference between celiac disease and gluten sensitivity (intolerance) and gluten allergy
Celiac disease is an autoimmune disease not an allergy, the body is trying to fight against gluten like its a virus. Celiac disease is a result of an abnormal gene. Gluten intolerance is when people experience symtpoms after having gluten but have no marker of autoimmune marker of celiac disease or IgE mediated reaction of a food allergy. And gluten allergy is IgE mediated and results in the overreaction of the immune system after you eat gluten.
explain what is believed to cause gluten intolerance?
not exactly known but some research says its not gluten itself but certain carbs in food that arent absorbed and stay in the gut and ferments causing sickness
what is the challange in producing gluten free products especially related to oats
Oats are 100% contaminated from wheat and therefore still pose a risk, they must recieve documentation and be tested for segreation. Gluten has a large air holding capacity so it must be done with something else like guar gum or xanthan gum. Pulse flours are frequently used as a sub
what are gluten sources
- wheat
- barley
- rye
- triicale
- oats (no gluten but contaiminated)
explain the formation of the processing induced toxin: acrylamide
Acrylamide is formed during the malliard reaction. It happens because of a reaction between asparagine and reducing sugars in starchy foods. It is carcinogenic, but there is no universally agreed safe level in food
what are other malliard reaction products that are bad
- carboxymethyl lysine (CML)
- heterocylcic amines (HCA)
- Advanced glycation end products (AGE): carsinogenic and with adverse affects
what are indicators used to monitor malliard reactions progression
- Hydroxymethylfurfural (HMF) : indicator of reaction progession
- furosine: indicator of heat damage
explain the formation of the processing induced toxin: nitrosamines
nitrate is reduced into nitrite, which can be absorbed into blood stream where it will react with myoglobin and make nitroasamine. This occurs in high heat and acic enviroments. they are commonly folund in cured meats and are carcinogenic.
why are nitrates and nitrite added to cured meats?
for color, flavor and preservation. The perservation is especially important to work agaisnt C. botulinum which is aneorbic this is especially important for vaccum packaged meats as that is the best condition for that bacteria.
what are the strategies to decrease nitroasamine fromation
- temperature control: avoiding high heat
- incorporating inhibitors: prevent reduction
- limiting nitrites and nitrates: have a balance between beneifts and negatives
