Process Cheese

Introduction

  • Originated in Germany in 1885; independent development in U.S. resulted in American patent in 1917 by J.L. Kraft.
  • Opportunity to 'engineer' and preserve cheese products
  • Stable process cheese emulsions can be made without any additives or other ingredients but it is both difficult and uneconomical

Standards: Canadian Regulations

  1. Process 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.
  2. Process cheese food must contain 51% cheese, not more than 46% moisture and not less than 22% fat.
  3. Process cheese spread must contain 51% cheese, not more than 60% moisture and not less than 20% fat.

Ingredients

Cheese

  • any type of natural cheese
  • 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
  • frequently plants use processing as an outlet for trimmings and 2nd grade cheese but this represents a small portion of total process cheese volumes
  • most Cheese used in processing is prepared especially for processing; usually stirred curd Cheddar or cheese base prepared by ultra filtration
  • younger cheese is now more frequently used: flavour compensated for with spices, and Cheddar flavour preparations (e.g. enzyme modified Cheddar)
  • too much young cheese gives a corky firm texture to the process cheese because with aging the proteins are broken down to shorter chains which have less interaction with each other and less elasticity, water holding capacity and emulsification capacity

Non-cheese Non Fat Milk Solids (NFMS)

  • skim milk powder, whey protein concentrate (usually 35% protein), whey powder, sodium caseinate
  • caseins bind water, especially sodium caseinate which is formed by reaction with emulsifying salts
  • denatured whey proteins also impart water holding capacity if denaturation occurs during process cheese manufacture
  • amounts of NFMS limited by texture (body) and lactose content (i.e., 15% of lactose in moisture phase will cause crystallization during cold storage.
  • too much whey protein will impair meltability -- an educated guess of an upper limit is about 1.5%

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
  • the fat source is apparently of little consequence except for moisture considerations

Melting Salts

  • also 'emulsifying salts' but not emulsifiers in the true sense
  • commonly: sodium citrate, sodium aluminium phosphate (SALP), Monosodium phosphate (MSP), Disodium phosphate (DSP, Trisodium phosphate (TSP), various polyphosphates; most common are NaCit and MSP
  • functional roles: chelate Ca, solubilize and disperse proteins, hydrate and swell proteins, emulsify fat, stabilize the emulsion
  • emulsifier blends are designed for specific products--for example process cheese slices require a different texture than process cheese

Acid

  • citric acid commonly 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
  • the risk is probably greater with high moisture cheese spreads
  • too low pH: crumbly firm texture, deemulsification
  • high pH: protein bonding and solubility improve, elastic, smooth, better emulsification, more risk of germination of bacterial 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 commonly used as mould inhibitor
  • inverting jars for a minute or two after filling also helps to control mould
  • by destroying mould spores in the head space

Colour

  • annatto present in natural cheese such as Cheddar is not stable in process cheese
  • water dispersable preparations of -Carotene are more successful

Moisture

  • when heated by direct steam injection, about 10% of batch weight is incorporated as condensate for most systems
  • additional moisture added as required

Process Systems

  • Stephan cookers are commonly used: reducing, heating and comminuting in one operation
  • continuous lay down cookers used for large scale production
  • basic process: Cheese selection and analysis, formula calculation, trimming, shredding (reducing), blending, heating, homogenization (optional for process cheese but advised for spreads), packaging, cooling, quality control tests (pH, moisture, fat, high temp storage)

Microbiology

  • process 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
  • precautions are:
  1. Use sanitized packaging
  2. Make sure the pH is not more than 5.6.
  3. Use phosphates in the blend of emulsifying salts to prevent germination of Clostridium spores.

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 additives. 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 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 which 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.

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 70C. Then turn vacuum pump off and continue heating to 85C. Hold at 85C 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 20.1 Process cheese composition control: Example

TABLE 20.2 Process cheese composition control