Cheese Production

This page describes the general production of cheese and includes the legal Cheese
Definitions, Ingredients, Bacterial Cultures, and General Manufacturing Procedure.

Cheese Definitions

Cheese comes in many varieties. The variety determines the ingredients, processing, and characteristics
of the cheese. The composition of many cheeses is defined by Standards of Identity in the U.S. Code of
Federal Regulations (CFR).

Cheese can be made using pasteurized or raw milk. Cheese made from raw milk imparts different flavours
and texture characteristics to the finished cheese. For some cheese varieties, raw milk is given a mild heat
treatment (below pasteurization) prior to cheese making to destroy some of the spoilage organisms and
provide better conditions for the cheese cultures. Cheese made from raw milk must be aged for at least
60 days, as defined in the CFR, section 7 CFR 58.439, to reduce the possibility of exposure to disease
causing microorganisms (pathogens) that may be present in the milk. For some varieties, cheese must be
aged longer than 60 days.

Cheese can be broadly categorized as acid or rennet cheese, and natural or process cheeses. Acid
cheeses are made by adding acid to the milk to cause the proteins to coagulate. Fresh cheeses, such as
cream cheese, are made by direct acidification. Most types of cheese, such as cheddar or Swiss, use
rennet (an enzyme) in addition to the starter cultures to coagulate the milk. The term “natural cheese” is
an industry term referring to cheese that is made directly from milk. Process cheese is made using natural
cheese plus other ingredients that are cooked together to change the textural and/or melting properties
and increase shelf life.

Ingredients

The main ingredient in cheese is milk. Cheese is made using cow, goat, sheep, water buffalo or a blend
of these milks.

The type of coagulant used depends on the type of cheese desired. For acid cheeses, an acid source such
as acetic acid (the acid in vinegar) or gluconodelta-lactone (a mild food acid) is used. For rennet cheeses,
calf rennet or, more commonly, a rennet produced through microbial bioprocessing is used. Calcium
chloride is sometimes added to the cheese to improve the coagulation properties of the milk.

Flavourings may be added depending on the cheese. Some common ingredients include herbs, spices,
hot and sweet peppers, horseradish, and port wine.

Bacterial Cultures

Cultures for cheese making are called lactic acid bacteria (LAB) because their primary source of energy is
the lactose in milk and their primary metabolic product is lactic acid. There is a wide variety of bacterial
cultures available that provide distinct flavor and textural characteristics to cheeses. For a more detailed
description of cheese cultures and microbiology, see Fox (2004), Kosikowski and Mistry (1997), and Law
(1997).

Starter cultures are used early in the cheese making process to assist with coagulation by lowering the pH
prior to rennet addition. The metabolism of the starter cultures contribute desirable flavor compounds, and
help prevent the growth of spoilage organisms and pathogens. Typical starter bacteria
include Lactococcus lactis subsp. lactis or cremoris, Streptococcus
salivarius subsp. thermophilus, Lactobacillus delbruckii subsp. bulgaricus, and Lactobacillus helveticus.
Adjunct cultures are used to provide or enhance the characteristic flavours and textures of cheese.
Common adjunct cultures added during manufacture include Lactobacillus casei and Lactobacillus
plantarum for flavour in Cheddar cheese, or the use of Propionibacterium freudenreichii for eye formation
in Swiss.

Yeasts and moulds are used in some cheeses to provide the characteristic colours and flavours of some
cheese varieties. Examples of moulds include Penicillium camemberti in camembert and brie,
and Penicillium roqueforti in blue cheeses.

General Manufacturing Procedure

The temperatures, times, and target pH for different steps, the sequence of processing steps, the use of
salting or brining, block formation, and aging vary considerably between cheese types. The following flow
chart provides a very general outline of cheese making steps. The general processing steps for Cheddar
cheese are used for illustration. For a more detailed explanation see the literature references by Fox
(2004), Kosikowski and Mistry (1997), Law (1997), Walstra et al. (1999), and the website
by Goff, www.foodsci.uoguelph.ca/dairyedu/cheese.html.

General Cheese Processing Steps

The times, temperatures, and target pH values used for cheddar cheese will depend on individual
formulations and the intended end use of the cheese. These conditions can be adjusted to optimize the
properties of Cheddar cheese for shredding, melting, or for cheese that is meant to be aged for several
years.

1. Standardize Milk

Milk is often standardized before cheese making to optimize the protein to fat ratio to make a good quality
cheese with a high yield

2. Pasteurize/Heat Treat Milk

Depending on the desired cheese, the milk may be pasteurized or mildly heat-treated to reduce the number
of spoilage organisms and improve the environment for the starter cultures to grow. Some varieties of milk
are made from raw milk so they are not pasteurized or heat-treated. Raw milk cheeses must be aged for
at least 60 days to reduce the possibility of exposure to disease causing microorganisms (pathogens) that
may be present in the milk.
3. Cool Milk

Milk is cooled after pasteurization or heat treatment to 90°F (32°C) to bring it to the temperature needed
for the starter bacteria to grow. If raw milk is used the milk must be heated to 90°F (32°C).

4. Inoculate with Starter & Non-Starter Bacteria and Ripen

The starter cultures and any non-starter adjunct bacteria are added to the milk and held at 90°F (32°C) for
30 minutes to ripen. The ripening step allows the bacteria to grow and begin fermentation, which lowers
the pH and develops the flavour of the cheese.

5. Add Rennet and Form Curd

The rennet is the enzyme that acts on the milk proteins to form the curd. After the rennet is added, the
curd is not disturbed for approximately 30 minutes so a firm coagulum forms.

6. Cut Curd and Heat

The curd is allowed to ferment until it reaches pH 6.4. The curd is then cut with cheese knives into small
pieces and heated to 100°F (38°C). The heating step helps to separate the whey from the curd.

7. Drain whey

The whey is drained from the vat and the curd forms a mat.

8. Texture curd

The curd mats are cut into sections and piled on top of each other and flipped periodically. This step is
called cheddaring. Cheddaring helps to expel more whey, allows the fermentation to continue until a pH
of 5.1 to 5.5 is reached, and allows the mats to "knit" together and form a tighter matted structure. The
curd mats are then milled (cut) into smaller pieces.

9. Dry Salt or Brine

For cheddar cheese, the smaller, milled curd pieces are put back in the vat and salted by sprinkling dry
salt on the curd and mixing in the salt. In some cheese varieties, such as mozzarella, the curd is formed
into loaves and then the loaves are placed in a brine (salt water solution).

10. Form Cheese into Blocks

The salted curd pieces are placed in cheese hoops and pressed into blocks to form the cheese.

11. Store and Age

The cheese is stored in coolers until the desired age is reached. Depending on the variety, cheese can be
aged from several months to several years.

12. Package

Cheese may be cut and packaged into blocks or it may be waxed.