4.4. the effect of processing on colour Flashcards
how can colour influence food?
-plays a role in the acceptability and enjoyment of food
-indicates the quality and nutritional value of food e.g. the bright colour of fruits and vegetables when they are at their peak in terms of nutritional value and texture
-can be used to judge the freshness
what are the uses of colour additives?
-to make up for colour losses following exposure to light, air, moisture and variations in temperature
-to enhance naturally occurring colours
-to add colour to foods that would otherwise be colourless or coloured differently
examples of naturally occurring pigments?
-Anthocyanins
-Chlorophylls
-Carotenoids
Anthocyanins - sources and the impact of processing
-Found in red cabbage, eggplants (aubergines) blueberries, strawberries
-Acids change it to a deeper red colour
-Alkalis change it to a blue / grey colour
-Metals can cause a reaction and so cans used in the canning process need to be lacquered
-Used in yoghurts, soft drinks, desserts
Chlorophylls - sources and the impact of processing
-Found in leaves, unripe fruit and many vegetables
-Unstable and damaged during cooking
-Acids change it to an olive green colour
-Alkalis make the colour greener but damage the texture of the food and affect the nutritional value
-Used in canned vegetables
Carotenoids - sources and the impact of processing
-Found in carrots, grapefruit, oranges and apricots
-Stable during heat processing
-Readily oxidised when food is dehydrated to form a colourless compound
-Often used in manufactured foods
-Insoluble in water, so often used in an emulsion of oil and water
-Used in drinks, sweets, jelly, margarines
what are the naturally occurring pigments in meat and what do they do?
-how is it affected by processing?
-The colour of meat is due to myoglobin, a pigment similar to haemoglobin
-Myoglobin is a dull purple/red colour but when combined with oxygen it will be bright red
-During storage myoglobin is converted to a dull grey/brown colour called metmyoglobin
-When meat is cooked, myoglobin is converted to a brown compound called haemochrome
impact of heat preservation on colour?
Brief heat treatment blanching can help preserve the colour of vegetables that are then frozen
how can the colour of fruits and veg be impacted by storage?
-Ethylene gas destroys chlorophyll and causes an undesirable colour.
-Freezing fruit and vegetables incorrectly can lead to freezer burn, which results in a brownish grey colour and spongy in texture.
how can consumer attitudes be affected by food colours?
-in fresh foods colour indicates freshness and ripeness
-is linked to consumer expectations
-Therefore If the colour of food products do not match a consumer’s expectations, they may perceive the taste and flavour of the food differently.
-however consumers have concerns over synthetic food dyes due to adverse health effects
-Most synthetic food dyes are complex nitrogen containing structures derived from coal-tar. Tartrazine, a bright yellow colour used in soft drinks and confectionery, has been known to cause food intolerance and allergic reactions.
how are food colours regulated and controlled?
International and national risk assessments are carried out to establish the safe use and safe levels of food colours
-eg.European Food Safety Authority (EFSA)
what does the European Food Safety Authority (EFSA) do?
-Assesses the safety of new food colours before they are authorised for use in the European Union.
-Reviews food colours in the light of new scientific information or changing conditions of use.
-food additives are given an international code. Numbers for colours are E100 - E199
-eg. E100 - Curcumin (from turmeric) - yellow-orange
E127 - Erythrosine (FD&C Red 3) - red
E164 - Saffron - Yellow-orange-red
examples of synthetic food dyes and what are they used for?
-tartrazine -synthetic lemon dye
-quinoline-yellow dye
-erythrosine-red dye
-used to replace colours lost in processing
health impacts of synthetic food dyes?
-an intolerance to tartrazine can cause skin rashes, hives, and nasal congestion. Rarely, tartrazine is said to cause asthma in sensitive individuals.
-Exposure to quinoline can potentially increase a person’s risk of certain types of cancer, including cancer in the liver, blood vessels, and the nasal cavity
-Long term erythrosine usage influences childhood behaviour, thyroid function, and results in inhibition of drug-metabolizing enzymes
