Cheddar cheese is a firm solid compressed curd which has a pale yellow color, a texture that varies from rubbery to flaky, a mildly acidic taste and a characteristic flavor/aroma. It has a shelf life of several days to several weeks depending on the storage conditions. It is used as an accompaniment to main meals, as a snack or in preparation of other foods.
Principles of preservation and methods of processing
Cheese is preserved by a number of different mechanisms:
- The raw milk is pasteurized to destroy most enzymes and contaminating bacteria.
- Fermentation by lactic acid bacteria increases the acidity which inhibits growth of pathogens and most spoilage bacteria.
- The moisture content of the separated curds is reduced and salt is added, both of which inhibit contamination.
- From raw milk, pasteurize it by heating 63°C for 30 minutes.
- Cool with stirring, to 35-40°C
- Inoculate. Add 2% starter for faster acid production and less for a slower fermentation. Use an aluminum or stainless steel tub.
- Add and mix prepared rennet (1% by weight of milk).
- Incubate. Stop stirring and allow milk to stand (30 minutes) until it sets to a firm curd.
- Cut curd with spatula to determine if ready. Cut curd in cubes (8mm). Rectangular stainless steel frames with nylon or stainless steel wire are available.
- Stand for 5-10 minutes for curd to firm.
- Heat. Slowly increase temperature 1°C for each 7 1/2 minutes up to 34°C and then finally to 38°C.
- Stop stirring when half of the whey is removed.
- Stir and drain until final whey is removed.
- Cut into blocks 150cm thick and turn them every 14-20 minutes
- Cut into potato sized pieces using knives.
- Add salt (approx 2% by weight).
- Fill the required amount of curd into a cheesecloth I (which has been sterilized in hypochlorite ), and place I in the wooden cylinder of a cheese press.
- Apply pressure gently. Allow to stand for 30 minutes. Apply more pressure and press for 8 hours (usually overnight)
- Remove from press, inspect, trim and package.
- Store at temperature not exceeding 15°C. Leave to mature for 3 months.
Hygiene and raw material control
As milk is a low acid food that is very susceptible to spoilage and transfer of pathogenic bacteria to consumers, the methods used to handle milk at the dairy play an important role in determining the quality of the final product. The main hygienic requirements are:
- Thoroughly clean and sterilize (with chlorine solution or boiling water) all equipment and utensils before and after processing (NB aluminum equipment should not be cleaned with chlorine solution).
- Strict enforcement of personal hygiene measures.
- Filter milk after milking to remove visible dirt and any ‘ropiness’.
- Cool milk immediately to control further growth of micro-organisms and enzyme activity. Milk which is likely to contain antibiotics should not be used as they will inhibit the action of lactic acid bacteria.
The main control points are:
- The temperature and time involved in heating and cooling the milk. Overheating and slow cooling causes changes to flavor, color and nutritional value; underheating may result in inadequate destruction of enzymes and micro-organisms leading to contamination. The following control points affect the flavor and texture of the final product.
- Correct amount of rennet added.
- Incubation temperature to allow rapid production of lactic acid by the inoculated bacteria.
- If the temperature is too high the bacteria will be destroyed, if it is too low there may be insufficient acid production.
- Adequate cutting and draining of the curd to remove most of the whey.
- Correct time and temperature of cooking the curd.
- Correct amount of salt added.
- Correct time and pressure during pressing the curd.
The main quality factors for cheese are the color, taste and texture. The color is determined mostly by the amount of heating during processing and the fat content of the milk. The taste and texture are both determined by the amount of lactic acid produced during the fermentation and this in turn depends on the amount of inoculum added to the milk and the temperature/time of incubation.
Packaging and Storage
Cheese does not require sophisticated packaging provided that the temperature is kept relatively low and it is not allowed to dry out. In a refrigerator the product may be wrapped in polythene. In a cool box the product requires protection against dust, insects etc. It should be stored in a cool place away from sunlight.
- Starter culture
- Cutting frame
- Cheese press
For more information, contact:Dept. of Science and Technology
Rm. 303 DOST Bldg., DOST Complex,
Gen. Santos Ave., Bicutan, Taguig City 1631
Telephone Nos: (632) 837-20-71 to 82