Dairy Ingredients for Food Processing

250 Chapter 10

undergo biochemical transformation to yield

an array of fl avor compounds. For example,

butyric acid, long - chain free fatty acids,

several lactones, and others form the back-

bone of the fl avor profi les of Camembert,

Brie, Roquefort, blue, Stilton, feta, Romano,

and provolone cheeses. The aroma of mold -

ripened cheeses is attributed to degradation

products of fatty acids, methyl ketones, and

secondary alcohols. Milk - fat - derived γ - and

Δ - lactones participate in the overall fl avor

profi le of cheddar cheese.

Caseins

Caseins are the substrates for production of

an array of fl avor compounds. In the early

stages of ripening, hydrolysis of caseins is

carried out successively by rennet, plasmin

of milk, culture proteinases, and peptidases

to produce peptides and amino acids. The

peptidases release large varieties of amino

acids which degrade further to amines, α -

keto - acids, hydroxy acids, sulfur compounds,

aldehydes, alcohols, esters, and thio - esters.

The level and ratios of many known and

unknown compounds orchestrate typical

fl avor profi les. The aroma is partially ascribed

to dimethyl sulfi de, dimethyl disulfi de, and

dimethyl trisulfi de, which arise from methio-

nine. Although a better understanding of

fl avor profi les exists for several cheese vari-

eties, it is still not possible to duplicate cheese

fl avor by mixing various chemicals in a

fl avor cocktail.

Proteolysis is also responsible for textural

modifi cations during ripening. As ripening

proceeds, protein degradation intensifi es, and

water - soluble nitrogenous compounds regis-

ter a signifi cant increase. Their level is gener-

ally used as an index of cheese maturation.

Control of Ripening Conditions

Moisture

Higher moisture early in ripening of cheddar

cheese is likely to accelerate ripening and

Lactose

Lactose is fi rst broken down via the glyco-
lytic pathway by starter bacteria to L - lactic
acid. In cheddar cheese types, most lactic
acid is produced in the cheese vat, whereas
in other cheeses, acid formation occurs in the
curd blocks. Nearly all of the lactose is
metabolized within a day of cheese making
in the Swiss variety because of effi cient
draining of whey. Furthermore, L - lactic acid
gives rise to propionic acid, acetic acid, and
CO 2 by propionic acid bacteria. The CO 2
gas pressure creates “ eyes ” in the cheese
texture. In the surface - mold ripened cheeses
(Camembert, Brie), lactose breaks down on
the surface to H 2 O and CO 2 , allowing the
mold growth with the resulting pH increase
in cheese. In washed curd varieties, espe-
cially Gouda, salting is delayed, which leads
to quick utilization of lactose. Salting is done
early in colby, which delays the total utiliza-
tion of lactose. During ripening, non - starter
lactic acid bacteria convert L - lactic acid to
DL - lactic acid, which further degrades to
acetic acid by lactobacilli and pediococci.
Cheese ripened for an extended period may
display a white surface due to the formation
of insoluble calcium lactate crystals.

Citrate

Citrate is naturally present in milk. During
cheese making, 0.2% to 0.5% citrate is
retained in the cheese curd (Singh and
Cadawallader, 2008 ). The Leuconostocs and
Lactococcus lactis biovar. diacetylactis
produce fl avor compounds from citrate,
acetate, diacetyl (2,3 butanedione), acetoin
(3 - hydroxy - 2 - butanone) and 2,3 butandiol.
Carbon dioxide is also produced, which gen-
erates small eyes in Dutch - type cheeses.

Milk Fat

Milk fat is the source of a host of fl avor
compounds. It is hydrolyzed by lipases to
yield fatty acids which form substrates and