Handbook of Food Science and Technology 3

1.3.5.
 Cream and butter
Cream and butter are dairy products with a higher fat content than milk; 
except for low-fat products, the fat content of cream and butter, respectively, is 
greater than 30% and at least 80%. Thus, the production of cream and butter 
begins with the separation of the fat globules from the skimmed milk. This is 
achieved by centrifugal separation in hermetic separators with conical plates 
(see Chapter 3, Volume 2) at a temperature usually ranging between 45 and 
55°C. 
1.3.5.1.
 Cream
Cream can be liquid (whipping cream), thick (sour cream) or aerated 
(whipped cream). Liquid cream has either undergone pasteurization (“crème 
fraiche”) or UHT sterilization. Thick cream is obtained after inoculating a 
pasteurized cream with certain starters. Whipped cream is obtained by 
introducing air into pasteurized or sterilized cream at low temperatures 
(usually between 4 and 10°C). 
Homogenization and heat treatment 
After separation, cream is homogenized to improve storage stability 
(creaming in liquid creams, release of whey in thick cream, etc.) or 
functionality (viscosity of cream, stability for cooking, foaming capacity, etc.). 
The concentration of available proteins in cream (casein, whey protein) for 
interface creation during homogenization is often limited. As a result, they are 
located at the interface of adjacent fat globules, leading to aggregate formation 
conducive to creaming. To limit this phenomenon, cream is homogenized 

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From Milk to Dairy Products 59 
using a two-stage homogenizer. The homogenization pressure of the first 
stage, between 13.5 and 20 MPa, is used to create the interface and decrease 
fat globule size; the second stage, set at a homogenization pressure of 10 – 
20% of that of the first stage, separates the aggregates of fat globules formed 
during the first stage.
Cream is heat-treated in plate heat exchangers (before or after the 
homogenization); the exchange area is about three times larger than that used 
in the treatment of milk due to the lower heat transfer coefficient in cream. In 
addition, temperatures are higher generally due to higher microbial load in 
cream and to the high thermal resistance of microorganisms in the presence of 
fat: the intensity of the heat treatment increases with increased fat content. In 
the case of pasteurization, the time/temperature combination is approximately 
50–10 s/80–100°C. Heat treatment is particularly challenging, since cream is a 
fragile emulsion and rapid temperature variations can significantly alter the 
properties of the emulsion.
Ripening 
Ripened or sour cream is a thick cream. Pasteurized cream is inoculated 
with up to 0.5% starter culture consisting of a combination of acidifying, 
aromatic (
Lactococcus lactis
subsp. 
Lactis cremoris
, 
Lactococcus lactis
subsp 
Lactis diacethylactis
, 
Streptococcus thermophilus
) and sometimes thickening 
strains (
Leuconostoc
), which produce exopolysaccharides generating thick 
creams at less acidic pH. The ripening phase takes 12 – 18 h at temperatures 
between 12 and 22°C. Acidification causes the gradual destabilization of 
casein micelles, some of which are adsorbed on the surface of the 
homogenized fat globules, resulting in the formation of a network of proteins 
and fat globules, and a thickening of the cream. The most significant changes 
of texture occur at a pH below 5.0–5.2.
Whipping 
Whipped cream is a foamed emulsion in which air bubbles are 
incorporated into a network of partially coalesced fat globules; in the presence 
of emulsifiers (mono- and diglycerides) and stabilizers (gelatine, carrageenan, 
etc.), this network ensures the rigidity and stability of the foam.
Cream intended for whipping is first homogenized, which increases the 
number of fat globules, and heat-treated before being refrigerated (4 – 10°C) 
for several hours (approximately 20 h) to promote fat globule crystallization. 

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60 Handbook of Food Science and Technology 3 
During the aging of cream at low temperature, emulsifiers gradually displace 
adsorbed proteins from the homogenized fat globule surface, thereby reducing 
fat globule stability [GOF 17]. During whipping, the collision of destabilized 
fat globules promotes partial coalescence. Partially coalesced homogenized fat 
globules move to the air interface and form a network that stabilizes air 
bubbles. In addition, stabilizers increase the viscosity of the non-fat phase and 
limit drainage by interaction with proteins of the non-fat phase and adsorbed 
proteins on the fat globules.
1.3.5.2.
 Butter
Butter consists of a continuous liquid fat phase in which triglyceride 
crystals, small fat globules, aqueous phase droplets and air bubbles are 
dispersed (Figure 1.27). It is made from cream, typically pasteurized, 
containing 40 – 50% fat, which is traditionally ripened (cultured butter) and 
then churned to induce phase inversion. Ripening includes two combined 
operations: 
– fat globule crystallization to develop the rheological properties of butter; 
– cream fermentation to develop aroma and decrease the pH of cream. 
These combined operations occur in cultured butters obtained by traditional 
batch churning or a continuous manufacturing process (Fritz process). The 
manufacture of cultured butters has gradually been replaced by the NIZO 
method, which is more flexible and economical, whereby fat globule 
crystallization and the production of flavor and acid are separate.