Dairy Chemistry And Biochemistry

396 DAIRY CHEMISTRY AND BIOCHEMISTRY

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EXTERNAL Lactose Lactose Lactose

ENVIRONMENT

CELL WALL MEMBRANE I’MF

CYTOI’LASM

Laciore-P Lactose i Laclose J.

I

t

Glucose Lactose Glucose

Galactose-6-P p4-t ADI’ Glucose-6-P - Galactose-I-P GlUCoSe-I-P KT1’ t AUI’ + - Glucore.6.P LlDP

{C::::

6-Phosphogluconate

1

Fructose-6-P

J

Tagatose.6-P

k”, K ::,

$

t

co2

ADI’ t

$.

Ribulose-5-P

Tagatose.1.6.blP Fructose-1’6-hiP

Xylulose.5-P

p,

v

Acetyl-P

1

CuASH

Dthydroxyacetone-P -1 Glyceraldehyde-3-P t

:::,yp

1.3-Diphosphoglycerate

3-Phosphoglycerate 24 ACETY L-CoA

CnASH

?-Phosphoglycerate t

I

Tagatose

pathway

Phosphoenolpyruvate

A,.. ‘\I I’ Fyruvare 2

Lactate

Glycolytic pathway

ACETYLALDEHYDE NADH

K l\AIl’

Ethanol

Leloir Phosphoketolase
pathway pathway
Figure 10.12 Metabolism of lactose by lactic acid bacteria; many Lactobacillus species/strains
can not metabolize galactose (from Cogan and Hill, 1993).

Solubilizes of colloidal calcium phosphate and thereby affects cheese

texture; rapid acid production leads to a low level of calcium in the cheese

and a crumbly texture (e.g. Cheshire) and vice versa (e.g. Emmental).

Promotes syneresis and hence influences cheese composition.

Influences the activity of enzymes during ripening, and hence affects

cheese quality.