1 It’s a matter of taste




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It’s a matter of taste


The way we experience tastes involves our noses, taste buds on our tongues, and different areas for sensing and remembering things in our brains.

Different people prefer different flavours. For example, some people prefer sweet foods, others prefer salty or savoury foods. Are these differences in what people like because people taste the same flavour in different ways? Or is it maybe because of memories associated with those flavours when we first tasted them? Or is there another reason?

You have the opportunity to plan and carry out an experiment to test what affects people's sense of flavour using different kinds of chocolate.

Choosing the right question


You need to choose a good scientific question to investigate. This question needs to be one that you can test with a scientific experiment that produces good data that you can study and draw conclusions from.

A question such as 'Do certain chocolates taste nicer than others?' is not a scientific question. It asks what people think and cannot be answered using an experiment – different people may have different ideas of what 'nice' means.

A question such as 'Do people respond to the same flavours in the same way?' is a better question because you can test this question more scientifically. For example, you could give people a range of chocolates of different sweetness and ask them to place them in order of sweetness.

Try writing a good scientific question for each of these investigations:



  • whether everyone responds to the same flavour in the same way

  • whether the same person responds to the same flavour in different ways at different times

  • whether a person's mood affects their response to a flavour

  • whether a person's sense of taste is linked to their other favourite foods.

Then choose one of the questions to plan as an investigation.

Deciding how to take measurements


You will have to ask the people you test to answer a question about what they are tasting. This question will generate the data that you will analyse.

Choosing a question that allows a range of answers will give you better data for analysis. For example, you could ask each person 'On a scale of 1 to 5, 1 being very bitter and 5 being very sweet, what grade would you give this chocolate?' This will give you more data than just asking 'Is this chocolate bitter or sweet?'

Using numbers for the grade makes the results quantitative, which means they are easier to manipulate (such as by taking averages of groups) and to present in tables, charts or graphs.

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t is often a good idea to take repeat measurements for each test (though you will need enough chocolate to do this!). You can then average the results to reduce the effect of differences that happen by chance.


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It’s a matter of taste

Making the test fair


In a fair test all the variables are controlled apart from the independent variable (the variable you are interested in changing, which in this case is the type of chocolate). The variable you measure, the dependent variable, is each person's response.

Many factors affect people's responses in a test situation, particularly sight and smell. For example, colouring a food blue often puts people off a food, even if they know it's their favourite. You will need to think of how to avoid these factors.


Recording your results


The best way of presenting your results will depend on what data you collect. In most cases a table will help you organise the results in a way that helps you to identify any pattern in the results.

The independent variable (type of chocolate) is qualitative. If the measured variable (person's response) is quantitative, then you will also be able to present your results as a bar chart. This may also help you identify any pattern in the results.


Considering your results/conclusions


Use your results to draw a conclusion for your investigation. Remember to refer back to your original question when you do this. Have your results answered your original question? If so, what is the evidence for this in your results?

If you can, try to use your science knowledge to explain your conclusion. In this case, you would talk about how the taste buds and brain respond to flavour.


Evaluation


At the end you should evaluate your investigation. Here are some questions you could consider in your evaluation.

  • Did the results help you answer your question well? If not:

    • was this because your question was not a good scientific question?

    • or was it because you didn't collect good enough data to answer your question?

  • How could your original question be improved to make it easier to answer with a scientific investigation?

  • How could your method for asking people be improved, in order to collect better data?


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Chocolate energy

The table shows the mass and energy content of a range of chocolate bars.

Convert all the values to kJ/100 g of chocolate so that you can compare the energy content of the chocolate in each bar. Note: 1 kcal = 4.18 kJ.

Use your results to decide which chocolate would be the best for use as 'emergency rations' on an expedition, that is the chocolate that contains the highest amount of energy for the same mass.




Chocolate

Mass of chocolate bar (g)

Energy content

milk chocolate bar A

75

1654 kJ

diet chocolate bar B

60

998 kJ

dark chocolate bar C

200

1050 kcal

milk chocolate bar D

75

2270 kJ

white chocolate bar E

100

580 kcal

milk chocolate bar F

100

2340 kJ

dark chocolate bar G

75

390 kcal

white chocolate bar H

60

345 kcal


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Chocolate’s melting point

The chocolate in a chocolate bar, chocolate shape (such as an Easter egg) or surrounding a soft centre is 'tempered' chocolate. This means that it has been treated in a particular way to make it crisp and brittle when you bite it. It also gives it a shiny surface.

If chocolate is treated in other ways, these properties change. This is because the cocoa butter in the chocolate forms a different structure depending on how it is treated. The melting point of the chocolate may also change.

In this investigation you will measure and compare the melting points of chocolate from the same bar. Some of the chocolate will have been melted and then chilled rapidly to solidify it before you use it.

Safety

Do not taste the chocolate, as it has not been prepared in hygienic conditions.



Apparatus

hot water (no more than 50 °C)

beaker

grated chocolate, some treated and some untreated



thermometer

boiling tube

stopclock

Method


  1. Pour some hot water into a beaker.

  2. Place 1 cm depth of grated, untreated chocolate into a boiling tube (enough to cover the bulb of the thermometer when the chocolate melts).

  3. Place a thermometer into the tube and measure the temperature.

  4. Place the tube into the hot water and start the stopclock. Use the thermometer to slowly stir the chocolate.

  5. Measure the temperature of the chocolate every 15 seconds for 5 minutes. Record each temperature.

  6. Repeat steps 1–5 with the treated chocolate.

Recording your results

  1. Draw a table to display your results.

  2. Use your table to draw a graph or chart that best displays the results for both kinds of chocolate.

Considering your results/conclusions

  1. Use your graph to decide whether the two kinds of chocolate had the same or different melting point.

  2. Explain your decision.


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Activity courtesy of the Nuffield Foundation


Exploring Science Extra Student worksheet © Pearson Education 2012



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