Food Chemistry

736 15 Cereals and Cereal Products

Table 15.58.Concentrations of the odorants in the
headspace of baguettes as a function of storage at room
temperaturea

Odorants Concentration
(ng/lair)after

1h 2 .5h 4h

Methylpropanal 830 536 400
2-Methylbutanal 320 230 170
3-Methylbutanal 150 85 68
2,3-Butandione 980 705 670
2-Acetyl-1-pyrroline 3. 73. 33. 7
Hexanal 216 237 254
(E)-2-Nonenal 28 36 44
(E,E)-2,4-Decadienal 7. 86. 56. 6

aTo determine the concentration, the air above the

baguette was collected for 15 min.

Table 15.59.Decrease (%) in 2-acetyl-1-pyrroline in
the crust of white bread during storage

Time (h) 2-Acetyl-
1-pyrroline

00
346
24 77
168 89

Table 15.60.Influence of the fermentation time and
temperature on the concentrations of odorants in the
baguette crusta

Odorant Concentration (μg/kg)

Baguette I Baguette II

2-Acetyl-1-pyrroline 16 14
Methylpropanal 1733 4331
2-Methylbutanal 1147 1487
3-Methylbutanal 426 680
Methional 31 49
1-Octen-3-one 3. 82. 1
(E)-2-Nonenal 61. 840. 4

aDough I was fermented for 2 h 40 min at 26◦C,

dough II for 2 h at 22◦C and then 18 h at 4◦C.

and the resulting increase in the dough tempera-
ture result in a decrease in theStreckeraldehydes
in the crust (Fig. 15.48).

15.4.3.3.2 White Bread Crumb

In dilution analyses, 3-methylbutanol, 2-phe-

nylethanol, methional, (E)-2-nonenal and (E,E)-

2,4-decadienal were identified as the most

important odorants in the baguette crumb. The

odorants which produce the intense aroma note

were detected in a comparison of two baguettes

which were baked with two differently composed

pre-fermented doughs. The crumb of baguette I

had a pleasant intense odor, but in II this note

was weak and a rancid aroma defect appeared.

Table 15.61 shows that the concentrations of

2-phenylethanol and 3-methylbutanol, which

have a flowery/intense and alcoholic odor, are

higher in I than in II. The higher concentration

of the sweaty 2-/3-methylbutyric acid in II

produces the rancid aroma defect. A low yeast

concentration in a liquid preliminary dough,

whichisonly1.5% based on the finished

dough I compared with 4.6% in dough II, is the

prerequisite for an optimal formation of both

the alcohols shown in Fig. 15.49. The curves

show that the concentrations of the two aroma

substances reach a plateau after eight hours

under the selected conditions. Their precursors

phenylalanine and leucine, which originate in the

flour and are degraded by yeast via theEhrlich

pathway to give the odorants (cf. Formula 15.8)

are converted after this time or the bioconversion

stops because important yeast nutrients are

increasingly lacking.

Table 15.61.Odorants of white bread crumb – compar-

ison of two kinds of bread subjected to different dough

makinga

Compound Concentration (mg/kg)

Bread I Bread II

2-Phenylethanol 11. 82. 87

3-Methylbutanol 18. 19. 7

2-/3-Methylbutyric acid 0 .55 1. 5

aRecipe (kg): flour (I: 4.15; II: 4.9), water (I: 2.27;

II: 2.825), salt (I, II: 0.11), yeast (I: 0.125; II: 0.325),

pre-ferment (I: 2.005 of A; II: 0.5 of B). Pre-ferment A:

a suspension of flour (1 kg), water (1 kg) and yeast (5 g)

was incubated for 15 h at 30◦C. Pre-ferment B: dough

made of flour (250 g), water (175 g) and yeast (75 g)

was incubated as in A.