Lab #4- Meghan Wright Exercise #1 Part 1-Milk Effect of treatment on the denaturation of milk proteins
treatment
pH
effect (visual, smell, tactile, consistency)
acid
4
Smells acidic, curdled when acid added
base
7
No change
salts
5
fizzy
heat
6
Browns, thins - if heated till browned tastes bad because its burned
plain tap water
6
thins
control
6
Protein structure in Milk: 1. What has happened to the globular structure of milk proteins?
2. Why do cheese makers normally use rennet (an enzyme which coagulates protein) rather than vinegar? Because it helps to preserve dairy products better.
3. Are there milk products that are coagulated with acid? Cream Cheese and Mozzarella cheese (to avoid maturation) and cultured Milk
4. How is sour cream and yogurt made? By letting cream ferment (or sour = tangy taste) with the addition of lactic acid bacteria.
5. What kind of factors degrade the quality and taste of milk? Milk can spoil when introduced to extreme variations in temperature - bacteria can form in the milk and it can begin to curdle because of the lactose content in the milk; Milk spoils when bacteria converts the lactose into glucose and galactose, which produces lactic acid; bacteria can form on the butterfat and mold can begin to grow from it.
6. There are two kinds of "allergies" to milk. Describe the symptoms, what the allergy is to. -The actual allergy to milk stems from an adverse reaction to the proteins in milk; symptoms include those normally associated with allergic reactions ranging from intestinal discomfort to skin reaction to anaphylaxis; the reaction will occur when any quantity of milk is ingested -Lactose intolerance is often assumed to be an allergic reaction to dairy products but is actually just a food sensitivity to the sugars in milk that cannot be properly broken down due to an individuals' inability to produce the enzyme lactase that breaks them down; a reaction usually occurs when larger quantities are ingested Part 2- Eggs and Egg Yolk Effect of treatment on the denaturation of egg white proteins
treatment
pH
effect (visual, smell, tactile, consistency)
acid
5
Acid congeals
base
7
Won't mix
salts
9
congeals
whipped
9
foam
plain tap water
8
Won't mix
control
9
Effect of treatment on the denaturation of egg yolk proteins
treatment
pH
effect (visual, smell, tactile, consistency)
acid
4
Cloudy when added
base
9
Becomes glue-like
salts
5
Won't mix
Whipped
5
Cloudy consistency
plain tap water
6
Cloudy when added
control
8
1.
2. Why is there such a difference in how egg whites and egg yolks respond to denaturation? -egg whites respond to the unfolding of proteins by producing foam, egg yolks respond to heat by solidifying when the heat breaks down the enzymes needed to synthesize its main anti-oxidant
3. Find 2 or 3 ways that egg whites can be stabilized so they hold their shape. -hard boiling them -sunny side up eggs
4. Can milk be "whipped"? Yes, whipped cream - heavier form of milk
5. What happens when eggs are whipped? Why should eggs be warm when whipped, but cream needs to be cold? When eggs are whipped the two parts come together and a foam will form from the egg whites; the activity in both and their need to be cold or warm when whipped stems from the activity of the proteins.
6. Compare the percentage of proteins in milk vs. eggs. Did this have an effect on the results you saw in the two exercises? -One large egg has 6 grams of protein and 1 cup of milk has 8 grams;
Exercise #1
Part 1-Milk
Effect of treatment on the denaturation of milk proteins
Protein structure in Milk:
1. What has happened to the globular structure of milk proteins?
2. Why do cheese makers normally use rennet (an enzyme which coagulates protein) rather than vinegar? Because it helps to preserve dairy products better.
3. Are there milk products that are coagulated with acid? Cream Cheese and Mozzarella cheese (to avoid maturation) and cultured Milk
4. How is sour cream and yogurt made? By letting cream ferment (or sour = tangy taste) with the addition of lactic acid bacteria.
5. What kind of factors degrade the quality and taste of milk? Milk can spoil when introduced to extreme variations in temperature - bacteria can form in the milk and it can begin to curdle because of the lactose content in the milk; Milk spoils when bacteria converts the lactose into glucose and galactose, which produces lactic acid; bacteria can form on the butterfat and mold can begin to grow from it.
6. There are two kinds of "allergies" to milk. Describe the symptoms, what the allergy is to.
-The actual allergy to milk stems from an adverse reaction to the proteins in milk; symptoms include those normally associated with allergic reactions ranging from intestinal discomfort to skin reaction to anaphylaxis; the reaction will occur when any quantity of milk is ingested
-Lactose intolerance is often assumed to be an allergic reaction to dairy products but is actually just a food sensitivity to the sugars in milk that cannot be properly broken down due to an individuals' inability to produce the enzyme lactase that breaks them down; a reaction usually occurs when larger quantities are ingested
Part 2- Eggs and Egg Yolk
Effect of treatment on the denaturation of egg white proteins
Effect of treatment on the denaturation of egg yolk proteins
1.
2. Why is there such a difference in how egg whites and egg yolks respond to denaturation?
-egg whites respond to the unfolding of proteins by producing foam, egg yolks respond to heat by solidifying when the heat breaks down the enzymes needed to synthesize its main anti-oxidant
3. Find 2 or 3 ways that egg whites can be stabilized so they hold their shape.
-hard boiling them
-sunny side up eggs
4. Can milk be "whipped"? Yes, whipped cream - heavier form of milk
5. What happens when eggs are whipped? Why should eggs be warm when whipped, but cream needs to be cold? When eggs are whipped the two parts come together and a foam will form from the egg whites; the activity in both and their need to be cold or warm when whipped stems from the activity of the proteins.
6. Compare the percentage of proteins in milk vs. eggs. Did this have an effect on the results you saw in the two exercises?
-One large egg has 6 grams of protein and 1 cup of milk has 8 grams;