1. Introduction

Processed cheese originated in Germany in 1885. Independent development in U.S. resulted in an American patent in 1917 by J.L. Kraft. The process offers the opportunity to ‘engineer’ and preserve cheese products.

2. Standards: Canadian Regulations

Processed cheese: must be made from cheese in which the maximum content of moisture is less than 40%. Maximum moisture is 3% more than the maximum for the cheese variety used. Minimum fat is 2% less than the minimum for the variety used. If more than one variety is used, the standards are calculated on the basis of the mean standards for the varieties used.

Processed cheese food: must contain 51% cheese, not more than 46% moisture and not less than 22% fat.

Processed cheese spread: must contain 51% cheese, not more than 60% moisture and not less than 20% fat.

Processed cheese product: may contain non-dairy fat and other non-dairy solids. In Canadian regulations, non-dairy solids include rennet and acid caseinates which for reasons to complex to explain here can be produced domestically or imported at relatively low cost. The result is that Processed Cheese and Processed Cheese Food have been mostly replaced by Processed Cheese Product.

3. Ingredients

Cheese

Any type of natural cheese is permitted. In U.S. and Canada, the cheese base is usually Cheddar or Cheddar types where a 3 month blend (some old cheese with young cheese for an average age of 3 months) is preferred. Too much young cheese gives a corky texture to the processed cheese because the proteins in aged cheese are broken down to shorter chains that have less elasticity, water holding capacity and emulsification capacity. Most Cheese used in processing is prepared especially for processing, usually stirred curd Cheddar or cheese base prepared by ultrafiltration. Processing is an outlet for trimmings and 2nd grade cheese, but these represent a small portion of total processed cheese volumes.

Flavour may be enhanced with spices and/or Cheddar flavour preparations (e.g., enzyme modified Cheddar).

Non-Cheese Non-Fat Milk Solids (NFMS)

Any type of milk non-fat solids (skim milk powder, milk protein concentrates, whey protein concentrate (usually 35% protein), whey powder, sodium caseinate) can be used with the following qualifications:

• Caseinates bind water strongly and contribute sheen. Too much caseinate makes the batch too firm and gummy.
• Denatured whey proteins contribute water holding capacity, but too much whey protein will impair meltability. My educated guess of an upper limit is about 1.5% of the batch.
• The amount of non-fat milk and whey solids is limited by lactose content. More than 15% of lactose as a percentage of processed cheese moisture will cause crystallization during cold storage.

Fat

• From cheese or added as cream, butter or butter oil.
• Cheese fat is generally present in fat globules with intact fat globule membranes.
• If butter or butter oil is used, artificial membranes composed mainly of casein are formed during processing, however.
• The fat source is apparently of little consequence except for moisture considerations.

Melting Salts

• Also called emulsifying salts, but are not emulsifiers in the true sense.
• Commonly used salts are: sodium citrate, sodium aluminium phosphate (SALP), monosodium phosphate (MSP), disodium phosphate (DSP), trisodium phosphate (TSP), and various polyphosphates.
• Most common are sodium citrate and MSP.
• Functional role is to bind calcium, so calcium associated with casein is replaced by sodium. The resulting sodium caseinate is more soluble and has increased water holding and emulsification capacities. The physical effects are: the proteins swell with increased hydration, product viscosity increases, and the oil in water emulsion is stabilized.
• Emulsifying salt blends are designed for specific products. For example, processed cheese slices require a different texture than processed cheese spread.

Acid

• Citric acid is used to adjust pH. Melting salts raise the pH or at least increase the buffer capacity of the cheese.
• pH should be < 5.6 to prevent germination and growth of anaerobic spores.
• Low pH: crumbly, firm texture, de-emulsification.
• High pH: protein bonding and solubility improve and the cheese is more elastic and smooth with better emulsification; there is also more risk of germination of Clostridia spores.

Emulsifiers

Mono- and diglycerides may be added in small quantities but may actually interfere with emulsification by preventing protein-fat interactions

Preservatives

Sorbic acid is commonly used as mold inhibitor. Inverting jars for a minute or two after filling also helps to control mold by destroying mold spores in the head space.

Colour

Various water dispersible and heat stable formulations of annatto, Beta-carotene and Apo-8-Carotenol are available to colour process cheese. Annatto preparations used to colour natural cheese are not stable in process cheese.

Moisture

When heated by direct steam injection, about 10% of batch weight is incorporated as condensate for most systems. Additional moisture is added as required.

4. Process Systems

• Stephan cookers are convenient for small scale production. Reducing, heating and blending are completed in one operation.
• Larger scale processes use continuous lay down cookers.
• The basic process is:
  • Cheese selection and analysis
  • Formula calculation
  • Trimming, shredding (reducing), blending, and heating
  • Homogenization (optional for process cheese but advised for spreads)
  • Packaging and cooling
  • Quality control (pH, moisture, fat, shelf stability using high temp storage)

5. Microbiology

Processed cheese is a medium acid food with relatively high moisture content, which means that strictly speaking, it should be sterilized before storing and distributing at ambient temperature. However, the product has been “grandfathered” in and few incidents of food poisoning have been associated with process cheese products. Some precautions are:

• Use sanitized packaging.
• Make sure the pH is not more than 5.6.
• Use phosphates in the blend of emulsifying salts to inhibit germination of Clostridium spores.

6. Calculations

Suppose a processor wishes to make process cheese food of legal composition (46% moisture, 22% fat). To allow for error he decides to set his target composition at 43% moisture and 24% fat. The ingredients on hand are Colby cheese (42% moisture, 29% fat), Cheddar cheese (39% moisture, 30 % fat), butter (16% moisture, 80% fat), whey powder (70% lactose, <1% fat, 4% moisture) and a commercial blend of emulsifying salts. Calculate the formula required for a 10 Kg batch given that the weight of condensate added is 10% of the batch and the amount of cheese added is 70% of the batch of which 75% is Cheddar (75% of 70). See the composition control sheet and follow these steps:

1. Enter the final cheese composition and batch weight in the ‘Total’ row.
2. Enter the composition of the ingredients.
3. Enter the total amounts (as percentage values) of Cheddar (75% of 70) and Colby (25% of 70) in the ‘Total’ column.
4. Calculate the amounts (in percentages) of fat, moisture and NSF contributed by the cheese. For example, the fat contributed by Cheddar is 30% of 52.6.
5. Calculate the percentage of fat required to bring the total fat to 24%, i.e., 24 – (5.1 + 15.8) = 3.1 and enter this value in the “Fat” column opposite ‘Butter’.
6. Calculate the total amount (% of batch) of butter required (3.1 x 100/80 = 3.9). The amount of moisture (16% of 3.9) and solids-non-fat (4% of 3.9) contributed by butter can now be calculated.
7. Enter the required percentage amounts of the various additives. Calculate the amount of additional NSF required to bring the total NSF to 33%. Enter this amount in the NSF column for whey protein concentrate. Note: any combination of whey powder, skim milk powder or whey protein concentrate can be used to adjust NSF providing the total amount of lactose is less than 15% of the cheese moisture.
8. Enter the amount of water contributed by condensate and calculate the amount of additional water required.
9. Determine the totals of each column and row to check your calculations.
10. Calculate the amounts of ingredients required per batch.

Note: the example given above is relatively simple and requires only simple arithmetic. However, consider the case where a manufacturer has quantities of high moisture cheese which he wishes to utilize in processing. He may then need to calculate the maximum amount of this cheese that can be used to replace Cheddar without exceeding the legal moisture content. In this and similar cases the various unknowns must be defined in terms of required amounts of fat, NSF and moisture and the resulting equations solved simultaneously.

7. Procedure

1. Select and analyze (moisture and fat) cheese for processing. Normally a three month blend is preferred for processed Cheddar.
2. Calculate the formula.
3. Add all ingredients into the cooker.
4. Mix thoroughly (3 min at high speed).
5. Remove a sample for pH analysis. If the pH is higher than 5.6, add more acid.
6. Blend and heat with vacuum applied to 70°C. Then, turn vacuum pump off and continue heating to 85°C. Hold at 85°C for 2 min.
7. Package process cheese hot in boxes. Spreads should be homogenized while still hot and packaged in sanitized jars.

References

Price, W.V. and Bush, M.A. 1974. The process cheese industry in the United States: A review. I. Industrial growth and problems. J. Milk and Food Technol. 37: 135 – 152. II. Research and development. Ibid 37:179 – 198.

Table 33.1: Example of Process Cheese Composition Control [long description available].

Accessible Figure Descriptions

Table 34.1 is an example of processed cheese control. It breaks down the ingredients that are put into the processed cheese. In this example, Colby cheese, 6 months aged Cheddar, butter, whey powder, emulsifying salts, salt, acidulant, preservative, colorant, water, and condensate are added to this processed cheese. These ingredients are broken down into fat composition, water composition, and not-fat solid composition. For example, the Colby cheese used in making this processed cheese is made up of 29% fat, 42% water, and 29% non-fat solids. The butter used in making this processed cheese is made up of 80% fat, 16% water, and 4% non-fat solids. In total, with all of the ingredients accounted for, for example, the Colby cheese makes up 5.0% fat, 7.4% water, and 5.0% non-fat solids in the total cheese batch composition. When all of the ingredients are added together, it results in 10 kg of cheese with a composition of 24% fat, 43% water, and 33% non-fat solids.