Test your knowledge and understanding of cheese science and technology

The questions below have been designed to test knowledge and understanding of cheese science and technology. They are based on an E-book that I will eventually incorporate into the site. In the meantime 'browsers' can test their knowledge and understanding of cheese technology by attempting the questions below. A link to most of the answers is also given at the end of the question section. Professor Arthur Hill's E-book on Cheese is also a major free resource and is available at https://www.uoguelph.ca/foodscience/book-page/cheese-making-technology-ebook .

Cheese science and technology questions.

• Define the term cheese. 
• List the major cheese varieties made in Europe and North America.
• List the ingredients used in the manufacture of Cheddar and Feta cheeses.
• Explain the role/importance/significance of the ingredients you listed in Cheddar and Feta cheese manufacture.
• Casein constitutes ______% of milk protein?

• What is the concentration of fat in

  (a) un-separated whey  and (b) separated whey  from Cheddar manufacture?

Starters

• Explain the functions of a starter in cheese manufacture, and in cheese maturation.
• How effective are starters in inhibiting the growth and / or killing the major pathogens encountered in cheese?
• Describe the species composition of modern DVI / DVS cultures used for Cheddar and British Territorial cheese manufacture.
• Explain why Streptococcus thermophilus is used in these cultures.
• Discuss the salt tolerance of lactococcal starter strains compared with those of Str. thermophilus and its significance in cheese making.
• Explain the effect of temperature on acid production by lactococci and Str. thermophilus and its significance in cheese making.
• List the main causes of starter failure in cheese manufacture.

Many types of cheese making can be described as processes for removing moisture from a rennet gel. This moisture removal process or whey expulsion is termed syneresis.

• List the major factors that influence syneresis.

The following questions are designed to test your understanding of the factors that influence syneresis in commercial cheese manufacturing situations.

• The moisture level in Cheddar cheese is too low. What can the cheese maker do to increase moisture levels? 
• The moisture level in Cheshire cheese is too high. What can the cheese maker do to bring the moisture level down?

 Cheese yield

• Define the term Cheese yield
• Why is this term often corrected for moisture?
• Name the major components in milk that contribute to cheese yield.
• What does yield potential mean?
• Theoretical yield can be obtained using a yield equation. A well known equation is the Van Slyke equation. State the Van Slyke equation.
• Explain the meaning of the terms used in the Van Slyke equation and the assumptions implicit in the use of this equation. This equation can be shown to overestimate the yield of Cheddar cheese. Explain.
• While the Van Slyke equation is useful in practice it has not been derived from fundamental principles. Give an example of a yield equation that has been derived using fundamental principles.
• Milk of 2.5% casein and 3.8% fat was used to produce Cheddar cheese of 36% moisture. Calculate the theoretical yield of cheese expected from 1000 kg of this milk. 
• If the actual yield of cheese was 10% lower than the theoretical yield what would be the significance of this finding?
• How can you determine process efficiency in cheese manufacture?
• List target retention values for:
  protein, fat and casein in Cheddar cheese manufacture.
• There are TWO main reasons why storing milk at refrigeration temperatures results in a yield decrease of ~ 0.6%/day. Explain.
• How do different commercially-available coagulants, and especially the recently-introduced Camel
  chymosin, affect cheesemaking efficiency and key changes in the cheese during maturation?

Standardisation of cheese milk

• List the compositional standards for Cheddar, Cheshire, Cottage and Camembert cheese.
• Why is milk for cheese manufacture standardised?
• Given that milk of 4.0 fat and 2.5% casein is available for Cheddar manufacture and the cheese produced is of 37% moisture. Calculate what effect adjusting the fat content of the milk (standardising) to 3.0% ,3.2% and 3.5% fat would have on the FDM level in the cheese.
• Suggest standard deviations for key Cheddar quality attributes from a well controlled process. 

Mellowing

• How does mellowing influence cheese composition, cheese quality and yield?

Modeling can be useful in understanding differences between cheeses

• Using an appropriate model explain the differences between Emmental, Cheddar, Cheshire and Gouda cheese.
• What practical significance does the model approach discussed above have in the development of new cheese varieties including understanding the technology used?

Lawrence and colleagues have developed a model which has been used to select New Zealand Cheddar cheese for maturation and subsequent export.

• Discuss how cheese quality has been assessed traditionally, the theoretical basis of the Lawrence model and outline how the model might be improved following its commercial evaluation.
• Explain how flavour is developed in Cheddar or Gouda cheese including the importance of starter cell lysis.
• What makes some cheeses taste sweeter than others? How can 'sweetness' be developed? What are the product development implications of sweetness modification?
• Discuss how you would develop a 'cheese variant' with a sweet Italian-cheese taste but having a gross chemical composition and a manufacturing process similar to Cheddar. 

Pathogen control

• What microorganisms are responsible for most commonly encountered causes of food poisoning related to cheese? 
• Draw a flow diagram listing the critical food safety control points for a cheese made with pasteurized milk.
• If you were to amend this diagram for a raw milk cheese, what additional controls would you add? Comment on the control options if you suspected that there were low concentrations of Listeria monocytogenes or Mycobacterium avium subspecies paratuberculosis (MAP) in the incoming raw milk supply.
• What control elements are frequently missing in HACCP schemes for raw milk-cheeses?
• Discuss the limitations of starters in controlling pathogens in cheese.

Quality issues

• Explain how bitter off flavours sometimes develop in cheese.
• Outline strategies to avoid bitterness.
• A cheese buyer rejects a batch of bland, slightly curdy mild Cheddar cheese from a major cheese manufacturer. The cheese has been ripened for 3-months at 8°C and has a pH of 5.3. What might be wrong with the cheese?
• Discuss the role of NSLAB in cheese.
• Discuss how the growth of NSLAB can be controlled during cheese ripening

There are still several significant engineering challenges in designing mechanised cheesemaking systems. 

• Explain the advantages of cheese mechanisation.
• List the major mechanised systems for making Cheddar.
• Draw a flow diagram of a mechanised cheesemaking system of your choice.
• Explain how major manufacturers have tried to solve salting problems. How successful have they been? Can you suggest any design improvements?
• What pressures are commonly used in cheese pressing? Use imperial and metric units.
• How long is cheese pressed for?
• List the major mechanised cheese pressing systems.
• Draw a labelled diagram of a Blockformer.
• What pressure is used? What is the purpose of the vacuum? How long is the cheese pressed?
• The FSA in the UK has produced guidelines for salt intake. Why might these be of significance to cheese makers?

Making Cheddar cheese to meet the specifications of major UK supermarkets

•  Explain how you would make a typical mild Cheddar.
•  What would you do differently to produce a premium mature Cheddar for an 'up-market' retailer?

View selected answers to cheese science and technology assessment. PLEASE read text below before accessing the selected answers. Note also that only selected questions have been answered.

Please note that while I have taken reasonable precautions to ensure that these freely available answers are factually correct I cannot be held responsible for any financial losses, or other negative consequences of this material being used by anyone, for whatever reason! Note the Ebook covers all the questions above, contains references to the literature; has more examples, diagrams and more emphasis on cheese development.