Chemistry 11

1. Nathanael & Chloe
April 14, 2022
Maple Leaf Interna-onal School – Xi’an
Chemistry 11 – Midterm Assessment
Semester 2 – 2021-2022
April 2022
English Name:
Pinyin Name: Block:
Total 27 Marks
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2. Nathanael & Chloe
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Fundamental
Chemistry Involved
Baking bread & Sealing foods into a can
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Fundamental
Chemistry Involved
Baking Bread
Brief Description of Baking Bread
Bread is a product made from a mixture of flour, water, salt, yeast and other
ingredients. The basic process is to mix the ingredients together and wait for
the bacteria to react until the flour becomes a dough, which is then heated to
make bread.
The Chemical Species Involved
ASCORBIC ACID
Ascorbic Acid is a natural water-soluble vitamin (Vitamin C).
Ascorbic acid is a potent reducing and antioxidant agent that
functions in fighting bacterial infections, in detoxifying
reactions, and in the formation of collagen in fibrous tissue,
teeth, bones, connective tissue, skin, and capillaries.
XANTHAN GUM
Xanthan gum is a polysaccharide with many industrial uses,
including as a common food additive. It is an effective thickening
agent, emulsifier and stabilizer which prevents ingredients
from separating.
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BAKING POWDER
Baking powder is a dry chemical leavening agent, a
mixture of a carbonate or bicarbonate and a weak acid.
The base and acid are prevented from reacting
prematurely by the inclusion of a buffer such as
cornstarch.
CARBON DIOXIDE
Carbon dioxide is a chemical compound occurring as an
acidic colourless gas. Carbon dioxide molecules consist
of a carbon atom covalently double bonded to two
oxygen atoms.
LACTIC ACID
Lactic acid is an organic acid. It has a molecular formula
CH₃CHCOOH. It is white in the solid state and it is miscible
with water. When in the dissolved state, it forms a colorless
solution.
MALTOSE
Maltose is a sugar made out of two glucose molecules bound
together. It's created in seeds and other parts of plants as they
break down their stored energy in order to sprout. Thus, foods
like cereals, certain fruits and sweet potatoes contain naturally
high amounts of this sugar
Chemical Reactions
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Chemical reaction equation for flour fermentation:
C6H12O6 (aq) → 2C2H5OH(aq) + 2CO2(g)
This chemical formula expresses fermentation. Fermentation is a metabolic
process in which an organism converts carbohydrates, such as starch or
sugar, into alcohol or acid. For example, yeast obtains energy by converting
sugar into alcohol for fermentation. Bacteria ferment, converting
carbohydrates into lactic acid.
Chemical reaction equation for Maillard reaction:
C6H12O6→2CO2+2C2H6O+2ATP
This chemical formula expresses the Maillard reaction. Also known as the
carbonyl amide reaction. When monosaccharides and yeast are mixed and
heated, carbon dioxide and alcohol are produced and a small amount of
energy is produced. The reason why we can't eat alcohol from bread is that
it evaporates when it is baked in the oven.
Why Chemistry is Life?
Because chemistry is so important to our world, it plays an important role in
everyone's life and affects all aspects of our lives to some extent. Chemistry is
everywhere from the laboratory to the inside of our bodies.
When we cook, for example, we're just frying and frying, and chemical
reactions are happening every second of every day. Everything from changes
in taste and appearance to rearrangements of bonds between ions and
molecules is happening. Or inside our bodies, our stomach digests food,
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digests the energy from food through stomach acid, and releases it into
chemical energy for us to use.
Sealing foods into a can to extend the
shelf life
Brief description of each process
During the process of preparing foods can, the first step is cleaning and further
preparing the raw food material, filling the containers under a vacuum.
It is very important to heat foods until the high temperature under high
pressure, this step reduce the number of spores of harmful pathogens by more
than 99.9999%, enabling the product to be "commercially sterile" and to be
stored at normal temperatures.
As a result, canned food can be easily stored without refrigeration. There are
chemical principles of canned foods.
Chemical species and reactions involved
When making canned foods, high temperatures are usually used to sterilize the
cans. Because cans often contain a bacterium called botulinum, a type of
bacteria that produces a dangerous toxin (botulinum toxin) in the absence of
oxygen. Moreover, Botox itself is heat-resistant, and in order to make it lose its
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fecundity, it must be heated at 100°C for 6 hours. Therefore, high temperature
sterilization can eliminate the botulism in the can.
Why choose high temperature sterilization?
1. High temperature can destroy proteins, nucleic acids, active substances
in cells, therefore affecting the life activities of cells and destroying the
active biological chain of bacteria, so as to achieve the purpose of killing
bacteria.
2. High temperatures can destroy enzymes. From the point of view of bond
energy, although the bond energy of peptide bonds are difficult to
destroy, but those intermolecular forces are relatively weak, such as only
a few hydrogen bonds. Once these intermolecular forces are destroyed,
the high-level structure of the protein is also destroyed, and the catalytic
activity of the enzyme is extremely dependent on its high-level structure,
so high temperature can destroy the catalytic activity of the enzyme. In
general, high temperatures cause enzymes to denature, destroy the
structure of proteins, and inactivate enzymes.
3. The metal material “Sn ”of the can, can react with oxygen at high
temperatures.
Sn(s) + O2(g) SnO2(s)
The newly formed tin dioxide（SnO2） is usually used to formulate
coatings and polishes in the glass and enamel industries. Most
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importantly, tin dioxide is formed on the surface of tin in the air, which can
protect the film and become stable.
Chemistry is Life
Chemistry and our lives are closely related. Whether it is food,
cosmetics, or mechanical devices, knowledge of chemistry needs
to be applied. For example, in this topic, we discussed the
connection between chemistry and food, because of the nature
of chemistry, we can use high temperature to kill bacteria, make
food more delicious and easier to store.
In life, there are still many chemical substances reacting with
each other to produce toxins, thus causing harm to people. It can
be seen that only by learning chemistry well, can you better
protect yourself
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Reference
1. Bonnett, & D, E. (2015). Brown Apples. https://extension.purdue.edu/4h/Documents/
Volunteer%20Resources/Science%20Made%20Easy/Brown%20Apples.pdf
2. （“Chapter III Storage of food in cans”）
http://www.cnzx.info/JingPinKe/NongChanPinJiaGongGongYi/resource/tzxx/download/
sp2.pdf
3. Chemistry is Life. (n.d.). Www.whatischemistry.unina.it. Retrieved April 14, 2022, from
http://www.whatischemistry.unina.it/en/life.html
4. （“Periodic graphics: The chemistry of canning”.Andy Brunning）
https://cen.acs.org/articles/94/i36/Periodic-graphics-chemistry-canning.html
5. (“Tin”. Badiu)
https://baike.baidu.com/item/锡/1196
6. Wikipedia Contributors. (2019, September 5). Food browning. Wikipedia; Wikimedia
Foundation. https://en.wikipedia.org/wiki/Food_Browning
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7. （“Why do enzymes remain active at low temperatures but deactivate and denaturate
at high temperatures?”. Zhihu)
https://www.zhihu.com/question/33693107
8. 道客巴巴. (n.d.). ⾯包烘烤化学变化. Www.doc88.com. Retrieved April 14, 2022, from
https://www.doc88.com/p-697925262803.html
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