Case Study-Reduced Cheese Yields in a Commercial Cheddar Cheese Factory

Background

A consultant was asked to investigate an apparent reduction in the yield of Cheddar cheese made in October of year X compared with the same month a year previously. 

The consultant supervised the manufacture of 5 vats of cheese and the sampling of the milk and cheese for chemical analysis. The samples were analysed at a reputable laboratory.

The following data (Table 1) for milk and cheese composition and yield (adjusted per 100 kg of milk) were obtained.

Composition of milk and cheese, and yield of cheese

Table 1.  Composition of milk and cheese in five yield trials

Tasks

• Use the data in Table 1 to determine the efficiency of the cheese making process.

• Comment on the significance of your results. What does your analysis suggest as the cause of the perceived yield problem?

• Data for salt and starter have not been provided. Explain the implications, if any, of this missing data.

• Explain any limitations of your approach.

Data analysis

You may find it helpful to:

a. Determine casein and fat retentions.

b. Determine the casein:fat and/or protein:fat ratios of the milk in each vat.

c. Compare actual yields, yields adjusted for moisture and theoretical yields.

d. compare published data for milk composition in the UK and Ireland in October with other months.

Casein and fat retentions

In practical Cheddar cheese manufacture fat and casein retentions of 91 % and 96 % are often used as 'benchmark values'.

Determine the fat and casein retention values. You may use the calculator provided to calculate fat and casein retentions. How do your data compare with the benchmark values? How valid are these benchmark retention values? The casein:fat and protein:fat ratios can also be calculated using the calculator supplied.

Cheese yield

While there is a range of equations for calculating 'theoretical' yield the Van Slyke equation is still widely used. You may use the calculator provided to calculate the theoretical yield of cheese using the Van Slyke formula. Note that this equation overestimates yield by about 1%-why?

• How does actual yield compare with theoretical yield? What is the process efficiency?

• The moisture content of cheese has a major effect on yield. What is the effect of adjusting the moisture content of cheese to 37% on yield? What are the implications of this finding?

• What recommendations would you make regarding how this problem should be resolved?

How to approach this and similar yield investigations

Guidance on how to approach this and similar problems has been provided. This should be helpful to both students and trainee production managers.

© Copyright February 2002. All rights reserved. W M A Mullan.
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