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The use of salt in cooking (1) The use of salt in cooking (2) By how much does salt increase the boiling point of water? Is all salt the same? "Low sodium” salt substitutes What affects the colour and texture of cooked vegetables? Should beans be cooked with the lid on or off? The chemistry of baking powder The structure of ice and water Why do pans stick? Enzymes and jellies The chemistry of flavour Chemical changes during cooking The science of ice cream ‘Asparagus pee’ How hot are chilli peppers?
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Index SS01

 

Is it possible to detect which beans have been cooked in salted water and which have not?

Ask students to devise a tasting test to see if it is possible to detect which beans have been cooked in salted water and which in non-salted water.

Students will need to consider how much salt to use in the cooking water, ie what is a realistic amount as used by cooks.










Taste testing

Taste is very subjective. One way to make a taste test more reliable is to offer the taster three samples, two of which are the same (cooked in salted water, say) and one that is different (cooked in unsalted water). Can the tester tell which is the odd one out? The experimenters will have to make sure that there are no other clues as to which sample was salted. If colour is suggested as a possible clue, blindfold tasting could be used. Other factors such as length of cooking time will also need to be controlled for a fair test.

Apparatus and equipment
Each group of students will need:

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fresh green beans – about 20 g should be enough. The beans can be cut into short lengths (about 1 cm or so) for tasting
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access to two saucepans or large beakers (say 1 dm3)
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access to a cooker or other means of boiling the beans
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access to a top pan balance
• disposable forks or toothpicks can be used to distribute lengths of bean for tasting.

Chemicals
Each group of students will need:
•
Salt – about 20 g. Buy table salt rather than ‘laboratory’ sodium chloride.

 

Questions for students

These questions are in the students’ sheet and may be used to stimulate discussion.

1. How many times should you try the taste test? How often does the tester get it right? How many testers should you use? Do all the testers get similar results? What other factors will you have to keep the same to make this a fair test?
2. Does the length of cooking time affect the results?
3. You could use similar experiments to test the effect of salt on colour and texture (crispness/sogginess). In each case ask the tester to pick the odd man out from three samples and make sure that there are no clues to indicate which of the samples was cooked with salt. What other factors will you have to keep the same to make this a fair test?
4. Are the results similar for different foods – rice or potatoes, for example?


Safety
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Wear eye protection.
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Make sure that students follow proper hygiene precautions (see the section Experiments with food in How to use this material).
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Your employer’s risk assessment should be consulted before carrying out this activity. This activity is covered by model (general) risk assessments widely adopted for use in UK schools and colleges such as those provided by CLEAPSS, SSERC, ASE and DfES. Bear in mind, however, that these may need some modification to suit local conditions.

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