Dyes and pigments

Why are colours important for food?-atractive-indication of ripeness-indication of toxicity\

dyes: synthetic compounds which are food grade water soluble substances and added to improve colours

-coloured because-absorbs light in the visible region of the electromagnetic spectrum, transmit remaining light-appears as complementary colour

poppies are red: absorbs light at 375nm and 530nm-375 nmneed to know approximate values-530nm blue green region of the visible light spectrum-complementary colour to green blue is red

Pigments3 main types: anthicyanins C6-most widely occurring in plantspink red purple blue in fruits and vegetables-cranberries, blueberries, strawberries, raspberries-conjugated double carbon bonds-3 rings 6-3-6 structurecarotenoids-widespread, major produced by algaeprecursor for VA-similarly: conjugated double bondsREASON DOUBLE BONDS CAN EMIT COLOUR-more conjugation, more resonance, more energy

chlorophyllheme-red, haemoglobin: from animals

cooking lobster=> not reversible: some changechemical stability

oxidation=oxidised pigment moleules

pineapple-discolouratuion due to formation of complex with FE3+

delocalised e-s on the ring

carotenoid-extremely reactive allylic bonds due to high hnumber of unsaturated carbon carbon double bondsheating: natural trans isomer rearranges to cis isomer

chlorophjyllstability: heat and phMg2+ ions (stable complex)Baking soda-extremely green (9)Chlorophyll stableOlive greenVinegar –light colour(3)Yellowish brown colourh h Chlorophyll: degrade during heating-no longer can form coordinate bonds w/ magnesium ions-myoglobin+heme is hemogkobinbasis: oxygen can form reversible dative bonds with iron ionsoxyhemoglobin: red in colourautooxidation

foods containing lysine browns readilyheating foods with high carbohydrate content

mr szeto: buffet toniteYH:fraid-cant see toes?

Mr szeto:hes just jealous

Amino acids -sugar only