W20 Eggs & Milk & Cheese Lab Report PDF

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Eggs, Milk & Cheese Lab Report ...

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HTM*2700 Winter 2020

Name: Clena Aboagye-Mensah Lab Day and Time: Wednesday 1:30 PM

UNDERSTANDING FOODS EGG, MILK and CHEESE LABORATORY REPORT 1.a) Explain the role of cream of tartar during the formation of an egg white foam.(4 marks) Cream of tartar acts as an acid source which would provide protons which neutralize the negative charges around the egg white protein molecules and cause them to reach their IEP. At their IEP the molecule is unstable and therefore it will denature faster which would result in the foam forming easier and also produce a more stable, larger, stiffer foam. Egg Lecture #2 February 27th, 2020 Coursepack: Egg Unit pg. 105 b) Explain the change which occurs when an egg white foam is baked. (2 marks) When an egg white foam is baked the proteins coagulate resulting in a permanent foam. Egg Lecture #2 February 27th, 2020 2. Explain the two (2) functions that egg yolks perform in Soft Custard / Gelato (Product II Creamy Citrus Gelato, Egg Lab)? (8 marks) In this recipe, the egg yolks act as a thickener and an emulsifier. The egg yolks function as a thickener in the soft custard base. When the egg is cooked, heat causes coagulation. When it is stirred a sol is created and the amount of hydrogen bonds allowed to form decrease. The egg yolks also function as an emulsifier, due to the lecithin found in them. As an emulsifier, the hydrophilic end attracts water or ingredients containing water such as the lemon juice and the hydrophobic end is attracted to ingredients with fat such as the milk. Lemon juice is in the continuous phase and lecithin is keeping lemon juice in suspension and therefore creates a permanent emulsion between the mixture and lemon juice. Coursepack: Egg Unit pg. 122 3. a) After the vinegar is added to the milk-cream mixture (Step #3) when making the Homemade Ricotta Cheese (Product VI, Milk & Cheese Lab) the mixture quickly changes in appearance. Describe and explain what is happening (8 marks) Because of the acid source, hydrogen ions neutralize the negative charges around them which allow them to repel each other and the overall charge of the molecules become 0. The molecules become they become attracted to each other. This causes the casein proteins to reach their IEP making them unstable.At IEP, they denature faster and coagulate faster causing them to precipitate out of colloidal dispersion which is known as curdling. Milk Lecture #1 March 3rd, 2020 b) As you were heating the milk-cream mixture you forgot to stir for a while and notice there was a film /skin developing on the surface. What caused this film / skin to form? How can it be avoided? (3 marks) This is formed when water evaporates due to no lid, and this causes the casein molecules to concentrate at the surface and this is seen by the film formation. This can be avoided if the lid is on to retain water and the mixture is stirred occasionally to make sure the casein proteins don’t become concentrated. Milk Lecture #1 March 3rd, 2020

4. a) Explain why it is best to chill the whipping cream, bowl and beaters before beating the cream into a foam. (6 marks) Whipping cream contains a high fat content which is due to the lipoproteins present. At lower temperatures, the fat globules are more solid which results in a thicker cream. The solid fat globules clump together easier on the surface of the air bubbles. A thicker cream is easier to incorporate air bubbles into it which creates a higher volume foam. Milk Lecture #2 March 5th, 2020 Coursepack: Egg Unit pg. 138

b) When should sugar be added to a whipped cream foam is you want a high volume foam? Explain what happens if sugar is added earlier. (4 marks) Sugar should be added during the soft peaks or when a partial foam is created to ensure that it does not decrease the foam volume and stiffness. Adding sugar to early causes a lower foam volume because it interferes with denaturation; hydrogen ions form hydrogen bonds within the protein causing it to take longer to denature which increases beating time. 5. a) Can mozzarella be substituted for old cheddar cheese in the Welsh Rarebit? Consider the melting and blending properties of the two cheeses when explaining your answer. (6 marks) Mozzarella is an unripened cheese therefore it doesn’t mean the standards of a cheese that will blend well. However it has medium moisture and fat which would allow it to melt well. Because the changes in the protein of the cheese during the ripening process are not occurring in the mozzarella, this would ruin the finished product. However, old cheddar meets all the requirements, it is medium moisture, high in fat and is ripened. Therefore, old cheddar cheese is the best option for this recipe. Coursepack: Egg Unit pg. 122 ,138 b) The Welsh Rarebit (Product VI, Milk & Cheese Lab) prepared in the lab was a stringy, oily mixture. Explain what happened. (5 marks) This is due to overheating. When making this recipe, the double boiler probably wasn’t turn off as instructed using the cheese to overheat. Proteins were over coagulated due to a prolonged exposure of heat which resulted in the cheese being tough and stringy. Additionally, the fat emulsion is broken which causes the fat to form together which results in the oiliness.

TOTAL = ______ = ______ 46 10...