Institute of Food Research
Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK
www.ifr.ac.uk Tel: +44(0) 1603 255000 Fax: +44 (0)1603 507723
Taste and Flavour
Taste and Flavour
Learning objectives:
- Identify tastes and flavours
- Provide examples of tastes and flavours
- Distinguish between taste and flavour
- Explain the difference between taste and flavour
Key words: smell, flavour, aroma, olfactory, epithelium, volatile, pungent, chemesthesis
Background
The flavour of food depends more on its smell, than on its taste, and we can recognise a very large number of different odours indeed. What you think of as taste, is more likely to be aroma. That’s why food seems so tasteless when you have a cold. When you have food in your mouth, as you breathe molecules of the food that come off into the air (volatile chemicals) pass over a part of your nose called the olfactory epithelium.
Your olfactory epithelium is the super star of food flavour sensation!
You have about 350 different types of odour receptor, each one works like a lock and key to detect a particular set of scent molecules. The individual receptors work together in combinations to produce the sensation of smell. It is like the letters of a giant alphabet and the smells we perceive are the words made up from a 350 letter alphabet. Your memory recognizes the smell and tells you what it is.
The 10,000 different scents which humans usually recognize as ‘tastes’ are often actually ‘flavour’ (see activity Taste and Flavour), which many people who can smell confuse with taste. This sense of ‘flavour’ is greatly diminished by a loss of the sense of smell, often causing those with sudden onset anosmia (loss of the sense of smell) a great deal of concern when all food suddenly loses its flavour. Congenital anosmics often have a much more developed sense of taste than those who could smell at some point in their lives, and can enjoy food just as much as someone who could smell.
The olfactory bulb can detect around 3,000 compounds, which when combined together with the 5 tastes will make between 10,000 and 100,000 recognisable flavours.
Sensations other than taste that contribute to our sense of flavour are termed chemesthesis.
Activity
Ask the question “What is the difference between taste and flavour?”
Do the parma violet or jelly bean test. Ask the student to hold their nose and start to suck the parma violet or chew the jelly bean. Ask if they can tell what flavour it is and what they can taste. They will probably only say it is something sweet, which is the sugar taste in the parma violet or jelly bean. Now tell them to let go of their nose and they will get a sudden rush of the flavour and be able to tell you what it is. This demonstrates that it is smell which gives it flavour. Just like when you have a cold you can not “taste” your food properly.
Invite pupils to sniff four individual chemicals, and then the four mixed together. The sniff solutions are ethyl butanoate (1%), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (3%), methyl 3-phenylpropenoate (0.03%) and 5-hexyloxolan-2-one (0.02%) dissolved in propan-1,2-diol. Flavouring solutions should be made up before hand in suitable containers and diluted as indicated.
They will be asked to describe the smells and suggest the smell they would produce if mixed together.
Pupils then smell the four mixed together and describe the smell before it’s supposed smell and use is described (artificial strawberry).
Extension activity
The ability to distinguish between apple and pear can be tested by chopping or grating the two fruits and tasting one while smelling the other.
What you will require
• Jelly beans or parma violets
• Flavouring solutions dissolved in propan-1,2-diol (aka propylene glycol):
o ethyl butanoate (1%) – fruity
o 4-hydroxy-2,5-dimethyl-3(2H)-furanone (3%) – candy
o methyl 3-phenylpropanoate (0.03%) – balsamic
o 5-hexyloxolan-2-one (0.02%) – creamy
Health and Safety
Do not handle sweets without washing your hands or wearing gloves if pupils are eating them. Check for diabetes or use sugar free sweets. Instruct pupils to put sweets in the bin straight away if they do not like the taste to prevent the spread of germs.
Flavouring solutions should be handled with care and diluted to the indicated concentrations due to their potency and potential hazards at full strength. The flavourings are used in a variety of foods and fragrances and are safe at recommended dilutions. The % concentrations are recommended fragrance concentrations and pupils should not taste the solutions. Hazard indication of undiluted chemicals; Ethyl butanoate (irritant), 4-hydroxy-2,5-dimethyl-3(2H)-furanone (harmful), methyl 3-phenylpropenoate (irritant), 5-hexyloxolan-2-one (irritant). It is recommended that the fragrances are applied to an absorbent material such as cotton wool to prevent spillage.
Further reading
Neuroscience for kids – Taste http://faculty.washington.edu/chudler/taste.html
Neuroscience for kids – Test your taste lesson http://faculty.washington.edu/chudler/pdf/tastetg.pdf
New Scientist. How To Fossilise Your Hamster – and other amazing experiments for the armchair scientist. Pages 60-61. Ed. Mick O’Hare, 2007, Profile Books Ltd.
RegesCoffeeBreak.com 