Our cooking plan: The higher ratio of corn syrup to sugar is, the harder the sugar glass is.

Labor Division：

Material preparation: Wu Siqi

Measurement: Wang Jiayi & Wu Siqi

Experimental operation: Ding Xinying & Wang Jiayi
Recording: Dai Xiyang
Experiment designer: all group members

Project title: The higher ratio of corn syrup to sugar is, the harder the sugar glass is.

Introduction and reasons:

 Introduction:

Sugar glass is a transparent but brittle sugar sheet that looks like glass, which is made by dissolving sugar in water, adding corn syrup (major ingredient: glucose), then heating it to “hard crack” (146 - 154 Celsius degree) that makes 99% sugar concentration. 

This process inspired us to research for the factors affecting the hardness of sugar glass. 

 Reasons:

Sugar glass has an amorphous structure instead of crystalline structure. It is formed by sucrose molecule, that is a glucose molecule joined to a fructose molecule. When we add more glucose, it bonds well with the sucrose in the solutions because they are similar molecules. The glucose will prevent the sugar from recrystallization by getting in the way of sugar molecules forming crystals.

Hypothesis: 

The higher ratio of corn syrup to sugar is, the harder the sugar glass is.

Variables:

 Independent variable:         ratio of corn syrup to sugar

 Controlled variables:          weight of water (g)

                                             weight of butter (g)

                                             temperature of boiling (celsius degree)
               
                                             heating power 1600W

                                             source of sugar, corn syrup, water and butter

                                             contact point of plastic bottle

                                             contact area of sugar glass and supporting table

                                             stirring direction (clockwise)

                                            stirring frequency (50 times per minute)

 Dependent variable:            the hardness of sugar glass.

Experimental setup:

Ingredient

      Sugar, corn syrup, water and butter (easy to remove sugar glass out of the mould).

Tools

      Pan, an empty plastic bottle (which can be added more weight in it), rice grains, kitchen thermometer, mould, electronic balance, two same supporting tables.

Steps

1. Combine 250g of water with 100g of different proportioned sugar and corn syrup respectively. 

2. Number them 1~10 in the increasing rank of proportion of sucrose. ( corn syrup to sugar ratio: 0:10, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1, 10:0, keep their total weight unchanged of 100g)

3. Heat the mixture to 150 celsius degree in the same pan, and keep stirring in the  same direction and frequency during this process. 

4. Pour the same-weighted mixture in the buttered mould to ensure the same  thickness of sugar glasses.

5. Put the mould horizontally and wait for solidification.

6. Take the sugar glass out of the mould carefully.

7. Put the sides of sugar glass on two supporting tables with the same contact area  and let the center area of sugar glass hanging in the air .

8. Put an empty plastic bottle at the center point of the sugar glass.

9. Add rice grains for 0.5g each time until the sugar glass breaks down to test its  hardness.

A. Pre-trial experiment (Failure cases):

a. 
Procedure: 
1. Put 3.0 spoons of water, 3.0 spoons of sugar and 1.0 spoon of corn syrup in the pan 0. 
2. Heat the mixture using 2000W. 
3. Keep stirring the mixture clockwise for 4 minutes.
4. Pour the mixture into the mould to cool it down.

Result:
The mixture turns to solid very quickly even before we pour it out. 

Reason: 
We think it is because the temperature is too high that it exceeds the point of hard crack, thus the sugar turns to caramel state directly. 

Improvement: 
We decide to use 1600W instead of 2000W in the following experiments.

b. 
Procedure:
1. Put 3 spoons of water, 3.0 spoons of sugar and 1.0 spoon of corn syrup in the pan 1.
2. Heat the mixture using 1600W. 
3. Keep stirring the mixture clockwise for 4 minutes. 
4. Pour the mixture into the mould to cool it down.

Result: 
It’s very difficult for the mixture to become solid. (We have waited for 30min and the mixture is still in liquid state.)

Reason:
We think it is because the time for heating is too short to evaporate all the water in the mixture.

Improvement: 
We decide to lengthen the heating time to 4 minutes and 20 seconds.
Put the mixture into refrigerator to accelerate the solidification. 

B. Trial experiment:
Procedure:

1. Put 3 spoons of water, 3.0 spoons of sugar and 1.0 spoons of corn syrup in pan 2; 
    Put 3 spoons of water, 2.0 spoons of sugar and 2.0 spoons of corn syrup in pan 3; 
    Put 3 spoons of water, 1.0 spoons of sugar and 3.0 spoons of corn syrup in pan 4. 

Heat the mixture at the same time using 1600 W. 
Keep stirring the mixture clockwise for 4 minutes and 20 seconds. 
Pour the mixture into the mould and put it in the refrigerator to accelerate the solidification.

2. Take out the sugar glass from the mould carefully.

3. Throw sugar glass 2, 3 and 4 from a 35cm distance off the table and observe which one breaks.

4. Throw sugar glass 3 and 4 from a 50cm distance off the table and observe which one breaks.

Observation and Result

We find that the more corn syrup to sugar ratio added in the mixture, the darker of the color of the sugar glass. Moreover sugar glass marked 2 breaks from the distance of 35cm, sugar glass marked 3 breaks from the distance of 50cm, and sugar glass 4 doesn’t breaks.

In our experiment, we verify that the higher the ratio of  corn syrup to sugar is, the harder the sugar glass is. The hypothesis tends to be true.

However, these trial experiments are not strictly follow our design of experiment steps.

1. We use the number of spoons to measure the weight of variables. We should use a electronic balance.

2.The scale of kitchen thermometer is up to 110 celsius degrees, nevertheless, we need 150 celsius degrees. So we control the heating power unchanged in the sample tests. We should buy a candy thermometer which has a wider range up to 200 celsius degrees.

3. The regular mould we used is a bowl with flat base. But it is too small to make a thin sugar glass. It also leads to a quite long duration to cool down. We should use a larger rectangle flat-based mould, in order to make thiner sugar glass and reduce time of solidification.

4. Because the sugar glasses are quite thick, we do not use the original setup to test its hardness. Instead, we put them in the same height level and make them free fall at the same time and check which one breaks. We should use the well-designed setup in the formal experiments. 

5. There is some systematic error.
a. Indeed, this experiment is based on the effect of glucose to sucrose in the solidification of sugar glass. It is hard to find out a pure-glucose contained solution. Even though the major ingredient of corn syrup is glucose, it still contains other impurities. Further more, sugar converts into glucose and sucrose when heating. 

b. When we pour the boiling mixture from pan into mould, there exists residual sticking on the pan and is difficult to remove completely. It results the biased weight of sugar glass.

  

Reference:

César Vega; Erik Van Der Linden (30 December 2011). "Sweet Physics". The Kitchen As Laboratory: Reflections on the Science of Food and Cooking. Columbia University Press. p. 186. ISBN 978-0-231-15344-7. Retrieved 1 November 2012.

Provost, Joseph J.; Colabroy, Keri L.; Kely, Brenda S.; Bodwin, Jeffrey; Wallert, Mark A (02 May 2016). The Science of Cooking: Understanding the Biology and Chemistry Behind Food and Cooking. John Wiley & Sons. ISBN 9781118674208.

Sean Kelly; Bill Heffner. (29 July 2006). “Science and Property of Sugar Glass". Retrieved from:https://www.lehigh.edu/imi/scied/docs_students/Kelly_ReuPresentation.pdf