IB Chemistry
Food Chemistry Web Quest
Visit Mrs. Mucci’s home page and scroll down to the food chemistry web quest and follow the links to
answer the following questions.
Text
http://www.pearsonschoolsandfecolleges.co.uk/Secondary/Science/IB%20Resources/PearsonBaccalaureate/S
amples/SampleMaterialChemistry/ChemistryHigherLevelChapter17.pdf
Your Mother was a Chemist http://kitchenscience.sci-toys.com/Introduction
Fats and oils
http://kitchenscience.sci-toys.com/fats
http://kitchenscience.sci-toys.com/protein
http://kitchenscience.sci-toys.com/oxidation
http://kitchenscience.sci-toys.com/heating
1. Olive oil is mainly mono-unsaturated, whereas sunflower oil is mainly poly-unsaturated. Explain what is
meant by these terms. How would you expect the melting points of these two oils to compare? Explain
why this is so.
2. Most naturally occurring unsaturated oils are the cis-isomer, but hydrogenation of poly-unsaturated oils
can give the trans-isomer of unsaturated oils. Explain how cis- and trans- isomers differ and state what
differences you would expect between these isomers firstly with regard to melting point and secondly with
regard to nutritional value.
3. You are planning to make a ‘strawberry candy’ with a texture similar to chocolate by blending together
a lipid base, sucrose, food colouring and artificial strawberry essence. What kind of lipid would you choose
for this? Justify your choice.
4. Going from lard, through olive oil to canola oil to corn oil the degree of unsaturation increases. How
would you expect the chemical stability of these lipids to vary? Explain this.
5. Vegetable oils are frequently hydrogenated. Give the reagents and conditions used for these
reactions. Give two advantages for the food industry of doing this and two health concerns that the
general public might have about the products.
IB Chemistry
Food Chemistry Web Quest
Shelf Life
http://www.medlabs.com/Downloads/food_product_shelf_life_web.pdf
http://www.thenfl.com/product-integrity-services/shelf-life
http://www.pearsonschoolsandfecolleges.co.uk/Secondary/Science/IB%20Resources/PearsonBaccalaureat
e/Samples/SampleMaterialChemistry/ChemistryHigherLevelChapter17.pdf
Methods of Food Preservation
Introduction
Description: Food Preservation is the process of increasing the shelf life of foods by preventing spoilage
from microorganisms by the use of chemical preservatives, heat or the removal of moisture from the
food. Various methods are used to achieve this, some of which are: Dehydration/Drying, Fermentation and
Pickling, Canning, and Freezing.
Grade Level: First year college students
Curriculum: Food Science
Keywords: Food Preservation, dehydration, drying, fermentation, pickling, canning, freezing
microorganisms, preservatives, moisture content.
Task
Students are required to read information and make notes on:
1. reasons for food preservation
2. methods of Food preservation, namely: dehydration, drying, fermentation and pickling, canning,
freezing.
Process
Reading assignment:
Students will access the following websites to read and make notes
and answer questions on food preservation . You may also wish to
refer to your notes.
http://www.buzzle.com/articles/food-preservation-methods-ofpreserving-food.html
http://hubpages.com/hub/Methods-of-Food-Preservation
6. Give three specific examples of changes you might notice in specific foods that would indicate that they
had been in storage beyond their shelf life.
IB Chemistry
Food Chemistry Web Quest
7. Many cultures have traditional ways of preserving foods. Some that are common across a number of
cultures are fermentation, pickling, salting and drying. For each of these give an example of a food that is
preserved in this way and explain the reason why this method of preservation works.
8. What is meant by the term ‘rancidity’? State which food group becomes rancid and give two changes
you could make to the way in which the food is stored which would decrease this effect.
9. Adding antioxidants can increase the shelf life of foods. What is meant by the term antioxidant and
what type of food degradation does it combat? Name one synthetic and one naturally occurring
antioxidant used in foods.
10. Rancidity can occur by two distinct processes. Describe a way in which substances become rancid that
i) affects all types of lipids.
ii) affects unsaturated lipids much more than saturated ones. In the case of the latter what other
conditions are likely to accelerate the reaction?
11. If you were wanting to increase your consumption of antioxidants, name two foods that you would be
advised to eat more of and for each food name the active antioxidant present in it.
12. In food storage often the packaging is very important. Explain how each of these will help to increase
the shelf life of the product.
i) the moisture level is kept very low.
ii) the packaging excludes air.
iii) the wrapping is opaque.
iv) the product is stored at a low temperature.
IB Chemistry
Food Chemistry Web Quest
See text and PPT Food Additives
13. Additives are often introduced into foods to delay the onset of microbial growth. Name two specific
additives used for this along with one example for each of a foodstuff they are generally added to.
14. Auto-oxidation occurs by a free radical chain reaction. Explain what this means. Write equations for the
two reactions that are responsible for generating the major product.
15. Antioxidants added to food can reduce oxidative degradation in three specific ways. Outline these
mechanisms and give a specific example of an antioxidant that operates in this manner.
Colour
Watch the video http://www.sciencedaily.com/videos/2009/0112-chemistry_of_cooking.htm
Refer to the article starting on pg 214
http://books.google.ca/books?id=KF2A8Cz7BcC&dq=organic+chemistry+food&printsec=frontcover&source=in&hl=en&ei=dsD_S7LlO4P48AbYbHxDQ&sa=X&oi=book_result&ct=result&resnum=11&ved=0CE4Q6AEwCg#v=onepage&q=organic
%20chemistry%20food&f=true
16. Name three groups of compounds that are responsible for the colours of foodstuffs and, for each, give two
examples of specific foodstuffs in which they produce the colour.
17. One group of naturally occurring pigments has a structure closely related to that of vitamin A. Which group
of pigments is this and what are the principal structural features of this group of compounds?
18. The colour of red cabbage often changes when it is cooked or preserved. What is the principal colouring
agent in red cabbage? Give three factors that might affect the colour of this group of compounds when being
prepared as foodstuffs.
IB Chemistry
Food Chemistry Web Quest
19. Heme and chlorophyll are both frequently responsible for the colour of foods. Which groups of foods are
they found in? They have closely related structures; state one similarity and one difference in their structures.
What is the principal change that occurs when heme is converted into myoglobin, the major pigment in muscle
tissue?
20. Discuss some health concerns that people have with regard to the use of synthetic dyes in processed foods.
What regulatory changes, other than banning their use, would you propose that could reduce public concerns in
this regard.
21. When heated on their own, carbohydrates undergo changes that result in the formation of a brown colour.
What name is given to this process and how does it occur?
22. When carbohydrates are heated with proteins a second group of browning processes can also occur. What
name is given to this second group? Describe how these food groups interact to produce brown products.
23. What is the normal oxidation state of iron in heme. Under some conditions this may alter and lead to
undesirable changes in the appearance of meat – describe this change and the conditions required. Give
suggestions of two ways in which the storage of meat could be altered to delay this undesirable change.
24. Anthocyanins, carotenoids and chlorophyll all have very different structures. Why is it that all are coloured?
25*. When beetroot is boiled the water becomes a bright purple colour, but when carrots are boiled little
colouration of the water is noticed, but if carrots are fried, the oil becomes orange coloured. Use your
knowledge of the compounds responsible for the colour of these vegetables to explain these observations.
IB Chemistry
Food Chemistry Web Quest
Genetically Modified foods
Web sites to help you
http://www.csa.com/discoveryguides/gmfood/overview.php
http://www.albrightseed.com/biologicalengineering.htm
26. Briefly describe the process by which a plant or animal can be modified to produce a genetically
modified (GM) food.
27. Give three separate ways in which genetic modification might improve the yield from a food crop.
28. As well as improving the viability of plants and animals, genetic modification can also result in novel
substances being produced by organisms. Give a specific example of such a modification.
29. Many people are opposed to the introduction of genetically modified plants and animals. Explain what
their major concerns are.
Texture
Websites to help you
http://kitchenscience.sci-toys.com/solutions
http://kitchenscience.sci-toys.com/Foams
http://kitchenscience.sci-toys.com/Emulsions
http://kitchenscience.sci-toys.com/Gels
30. What physical properties of a food contribute to its texture? Disperse systems often display highly
desirable textures. What is meant by a disperse system?
IB Chemistry
Food Chemistry Web Quest
31. Three common disperse systems are suspensions, emulsions and foams. Distinguish between these
in terms of the states of the components.
32. The production of stabilised disperse systems often depends on additives such as emulsifiers and
stabilisers. Explain the role of these two groups of substances and name a synthetic example of each.
33. What characteristics do all emulsifiers have? Explain how these characteristics allow an emulsifier to
produce a stable disperse system from two immiscible components.
34. As well as requiring an emulsifying agent, the production of an emulsion always involves vigorous
beating of the components. Explain why this mechanical agitation is necessary.
IB Chemistry
Food Chemistry Web Quest
Food Chemistry Lab Next week on food preservation
Laboratory activities: In groups of three (3), students will do the following activities:
Lab exercise 1. Dehydration and Drying:
Cut fruits in thin slices and weigh, add 1tsp citric acid to sliced fruits, Place in container and put in solar
dryer for five days. Record weight of dried fruits. Use the lab report format to write up your lab report.
Discuss your findings.
Lab exercise 2: Fermentation and Pickling:
1. Wash and clean the vegetables and spices. Cut the vegetables in desired shapes approximately one-eight
of an inch thick. Add salt to vegetable, after 5minutes, drain off liquid. Prepare jars and lids by boiling in
water for 15 - 20 minutes. Remove from hot water and drain. Pack prepared vegetables and spices in. Pour
in warm acetic acid. Seal tightly.
Lab exercise 3 & 4: Freezing:
1.Vegetables - Wash, clean and blanch vegetables in brine. Drain and cool. Place in plastic freezer bags,
seal. Place in freezer for storage.
2. Fruits - wash and prepare fruits, cut in quater inch slices or half inch cubes where appropriate. Boil for 20
minutes in light syrup. Cool and place in plastic freezer bags. Place in freezer for storage.