BCBT 100 – Exam 4 Practice Questions {Bodwin – Fall 2012}

BCBT 100 – Exam 4 Practice Questions {Bodwin – Fall 2012}

Describe and identify the components of a seed.

Describe the difference between monocot and dicot seeds. Give examples of each.

What are some similarities and differences between grains, legumes, and nuts? How do they grow, what food molecules do they contain, etc

How is flour made? (from the McGee book)

What is “leavening”?

Describe the process and chemical reaction of chemical leavening.

What is the difference between baking soda and baking powder? Why are BOTH sometimes called for?

What is gluten? How is gluten formed? What type of interactions between molecules are present in gluten?

How does kneading encourage gluten formation?

Describe the ways in which gluten can be modified when making a dough. What physical or chemical steps can be taken to increase gluten formation? What physical or chemical steps can be taken to decrease gluten formation?

In aerobic metabolism of sugars, what are the products of the chemical reaction?

What are the products of the chemical reaction when yeast metabolizes sugars?

Describe the differences between yeast-leavening and chemical-leavening. What are some advantages of each?

What is Charles’ Law?

If the absolute temperature of 6.0L of a gas is tripled, what is the new volume of the gas?

What role does starch play in the structure of baking bread?

Why is it important that the bubbles in baking bread merge and pop during the baking process?

What are some of the results/effects of having a lot of steam present when baking breads?

What does it mean for a bread to become “stale”? How can staleness be prevented? Reversed?

How does the protein content of different types of flour affect the bread made from those flours?

What food molecules must be present for Maillard browning to occur?

What property/properties do aldehydes contribute to foods?

Above what temperature does significant Maillard browning take place?

What cooking conditions encourage Maillard browning? What cooking conditions inhibit Maillard browning?

Above what temperature does significant caramelization take place?

What chemical reaction is catalyzed by phenol oxidase?

What molecular changes take place that cause enzymatic browning?

What conditions would encourage more sugar browning/caramelization when cooking?

What role does water play in most browning reactions?

Where is chocolate grown?

Describe the process of making chocolate from the tree to the finished bar.

What type(s) of browning is/are responsible for the brown color of chocolate?

Which type of chocolate plant has the most delicate flavors?

What is the purpose of “Dutch processing” of cocoa powder?

Describe the molecular changes that take place when chocolate is tempered.

If a chocolate bar is not stored properly it can have a “dusty” appearance. Describe what has happened.

What causes chocolate to “seize”?

What are the advantages of letting chocolate melt in your mouth when tasting it?

Looks like Fruit & Veg!

But don't worry, we'll also do breads in a couple weeks.

On the fruit & veg side of things... We'll very likely do some tasting in the coming week or so. Are there any fruits or vegetables that you have never tried that you're curious about? Some vegetables that might be a bit less common (but I know I can get pretty easily...) might be some of the root vegetables (rutabaga, parsnip, turnip), or some different varieties of potato, or some different types of greens... On the fruit side, some of the less-typical citrus fruits, or unique berries...
Basically, if there's a fruit or vegetable (broadly defined) that you've always wondered about, let me know, we might use that as part of an in-class tasting, and you can have a new and exciting experience.

Next topics...

Fruits and Vegetables are winning in the early returns, but the polls are still open in the rural areas. Vote early, and in this case you can even vote often.

Exam #2 Practice Problems

#.     What is cheese? – Milk that has been curdled by acid and rennet that has had most of the water removed

#.     What is the primary role of salt in cheese? – Preservative

#.     Some enzymes used in cheesemaking hydrolyse fats and proteins during the aging process. How does this affect the final cheese? – Hydrolyzed fats and proteins usually lead to smaller molecules that contribute flavor and aroma. They can also tweak the texture.

#.     Why is it important to get chymosin (rennet) from young calves rather than adult cows? – Cows only produce chymosin while they are feeding on milk, once they’re off the milk, chymosin production drops off very quickly

#.     How was rennet “discovered? – It was a happy accident. When calf stomachs were used as waterproof bags for milk storage and transportation, the rennet curdled the milk into cheese

#.     What specific protein does chymosin (rennet) react with during cheesemaking? – Chymosin reacts with the kappa-casein proteins that coat casein micelles… This lets the “gooey” inner caseins to stick together and form a network of casein micelle chains

#.     When chymosin (rennet) reacts with protein during cheesemaking, what happens on a molecular level? – Rennet “shaves” some of the kappa-casein off the outside of the casein micelles and they stick together

#.     When acid reacts with protein during cheesemaking, what happens on a molecular level? – Acid denatures the casein proteins much more completely, allowing the individual casein protein strings to interact

#.     What are the main roles of propionibacteria in cheesemaking? – This is the hole-making bacteria

#.     Brevibacterium linens mainly contributes what to cheese? – This is the “stinky cheese” bacteria

#.     What are the properties of Penicillium roqueforti and other “blue molds” used in cheesemaking? – Can survive low oxygen, found inside the cheese, digests fats, contributes sharp/peppery flavor

#.     How are the “white molds” used in cheesemaking different from the blue molds? – Surface molds, digest proteins, make creamy texture

#.     When slowly adding heat to try and melt cheese, what component (food molecule) is affected first? Second? – Fats melt first, proteins denature next, water starts to boil/evaporate off, fat/protein start to brown/burn, things start on fire, chaos ensues

#.     In dishes that contain melted cheese, what causes “stringiness”? – Too many protein-protein interactions, lots of stirring

#.     Where is most of the fat found in eggs? - Yolks

#.     What does the color of the shell of a chicken egg tell you? – It can indicate the breed of chicken, but not much more

#.     What does amylase (an enzyme found in egg yolks) do? – We talked about this one in the food molecules section, amylase digests (hydrolyzes) amylose, that’s starch

#.     After water, what is the largest component (food molecule) of egg white? – Albumen proteins

#.     What happens on a molecular level when eggs are cooked “hard”? – Proteins denature and get all tangled up

#.     Describe the molecular changes that take place when egg whites are whipped. – Mechanical shearing/denaturing  of proteins, proteins stretch and tangle, capture air bubbles

#.     What role does cream of tartar serve in whipped egg whites? – It’s an acid, it prevents the formation of too many disulfide bonds

#.     Why are very strong interactions, like disulfide bonds, unfavorable in whipped egg whites? – Very strong interactions tend to squeeze water out and limit the ability of the protein chains to slide by each other while the meringue is forming/building

#.     How does heat affect an albumen foam (a meringue)? – Heat dehydrates the meringue, also denatures additional proteins (ovalbumen) to form more network connections, if there’s sugar present the heat will also dehydrate and form a bit of a sugar-strand network

#.     What component of an egg preparation has a very high heat capacity? - Water

#.     What component of an egg preparation is an excellent heat insulator? - Air

#.     What component of an egg preparation can melt, solidify or separate depending on temperature? - Fats

#.     What component of an egg preparation affects the structure and texture of the final dish depending upon whether it has been denatured or not? - Proteins

#.     What is “candling” and why is it done? – Shining light through an egg to see the yolk and determine the egg’s grade

#.     Describe the different grades of eggs. – AA = thicker albumen, prominent chalazae; A = less thick, weaker chalazae; B = industrial eggs, yolk swirls around inside the shell

#.     What is specific heat capacity? – The amount of heat/energy required to raise a given amount of a substance by a given temperature. Usually calories per gram-degree-Celcius

#.     If the specific heat capacity of water is 1 calorie per gram-degree-Celcius (1cal/g•°C), adding 100.0 calories of heat to 20.0g of liquid water at 17°C should {increase/decrease} the temperature to _______°C. – This should increase the temperature by 5°C to 22°C. 

(100.0calories) / (1cal/g°C) = 100 g°C

(100 g°C) / (20.0g) = 5°C.

#.     What role does the water bath play when cooking/baking a custard? – Even heating, slows down and evens out the denaturing of proteins in the custard, manages heat transfer

#.     Why is tempering important? – Tempering evens out the denaturing of proteins. If hot and cold were just dumped together all at once, some proteins would denature quickly where the solution was hot and the result would be a clumpy mixture

Exam 2 Format

Exam 2 (and all of your exams in BCBT 100) will be a multiple choice exam. The practice questions I posted do not have "multiple choice" answers included with them because when you are studying for the exam I want you to be thinking about the substance of the questions and topics, not just picking the correct answer out of a list of 4 or 5 options. Good luck and let me know if you have other questions.

(I'll post answer to the practice questions some time late today or tomorrow, make sure you look at the questions and try to formulate a response BEFORE you check the answers.)

You're the expert!

One of the nice things about a science class based on food and cooking is that in some cases YOU have real first-hand experience with the topics we're discussing. That means that sometimes (maybe even quite often), you will have experience or insight that is beyond what I have. I like that! It means that I can learn something too, and I always try to learn at least 1 new thing every day.
Related to this, someone pointed out a pronunciation I slipped up on in class yesterday... I have a very basic understanding of German, and in reading what was written on my slide while I was talking and thinking about what was coming up, I did a really bad job on the word "kuchen". It is absolutely NOT pronounced "koo-chin"... The typical American English "ch" pronunciation is generated almost entirely in the front of the mouth with the tongue and the teeth (it's a more "dental" sound), whereas the "ch" in "kuchen" is generated in the back of the mouth and throat, almost as if you're pronouncing a "hard c" and an "h" at the same time, a little like the "ch" in "chalazae" or "Bach". When this German "ch" is in the middle of a word, it is often pronounced almost like a "g", but a little farther back in the mouth/throat.
The biomechanics of linguistics is really pretty fascinating, and if you think about just how the sound of different letters and words are produced in the mouth, it's fun to experiment. Most people don't think about the way tongue, teeth, lips, cheeks, throat and lungs interact to do something as "simple" as speaking, if this is something you're really interested in you should check out the Speech, Language, Hearing Sciences department at MSUM.

Practice questions

Exam #2 is coming up on Tuesday... I've posted some practice questions {http://www.drbodwin.com/teaching/scicook/bcbt100aexam2practice.pdf}, take a look at them. I posted them in a little more open-ended format to encourage you to think about the question a little more rather than just ferret out which answer is correct. I'll post answers some time over the weekend, make sure you look at and think about the questions before you look at the answers. Good luck.