Dairy Chemistry And Biochemistry

CHEMISTRY AND BIOCHEMISTRY OF CHEESE AND FERMENTED MILKS^409

Saturated fatty acids (CJ

i

P-Oxitliltitin. -2H2+ H20

CoA.SH

CoA-SH

Keio acyl CoA

Thiohydrdilsu

CoA-SH + P-Keto acid Acalyl CoA + Acyl CoA (C2,J

Methyl ketone (C,,.]) + CO,

Rcduciasc

!

Secondary alcolinl (C,,.])

Figure 10.18 P-Oxidation of fatty acids to methyl ketones by Penicilliwm roqueforti and

subsequent reduction to secondary alcohols.

Table 10.6 Typical concentrations of alkan-2-ones in Blue cheese (from Kinsella and Hwang,

1976)

pg per 10 g dry Blue cheese

2-A1 kanone A" Ba C" Db Eb Fb G' H'

2-Propanone 65 54 75 210 -^0 60 Td
2-Pentanone 360 140 410 1022 367 51 372 285
2-Heptanone 800 380 380 1827 755 243 3845 3354
2-Nonanone 560 440 1760 1816 600 176 3737 3505
2-Undecanone 128 120 590 136 135 56 1304 1383

2-Tridecanone - - - (^100 120 77 309 945)
Total 1940 1146 4296 5111 1978 603 9627 9372
"Commercial samples of ripe Blue cheese.
bSamples D, E and F of Blue cheese ripened for 2, 3 and 4 months, respectively.
'Samples G and H of very small batches of experimental Blue cheese ripened for 2 and 3
months, respectively.
*Trace.
The level of proteolysis in cheese varies from limited (e.g. Mozzarella)
through moderate (e.g. Cheddar and Gouda) to very extensive (e.g. Blue
cheeses). The products of proteolysis range from very large polypeptides,
only a little smaller than the parent caseins, to amino acids which may, in
turn, be catabolized to a very diverse range of sapid compounds, including
amines, acids and sulphur compounds.