Baking & Snack - May 2004 - 99

EQUIPMENT

PROOFBOX TEMPERATURES

HEAT FLOW IN OVENS

"Former [proofing] standards called for a temperature of 35°C (95°F), a relative
humidity (rh) of 85% and a proofing time of 60 to 65 minutes. These parameters still
constitute valid guidelines, ..." (Baking Science & Technology, 3rd Ed., Vol. II.)
"... for sponge/dough white bread, the typical proofing condition was 46°C
(115°F), 75% rh (8° dry/wet bulb spread), for 55 to 60 minutes." (A.I.B. Technical
Bulletin, IX:2 [February 1987])
LOAF VOLUME AT VARIOUS
A higher proof temperature
PROOFING TEMPERATURES
shortens proof time when a
constant yeast level is used.
Temperature Dough-side Loaf
Increasing proof temperature by
yeast
volume
11°C (20°F) reduces proof time
(°F)
(%)
(cu cm)
by about 10 minutes. If 3.7%
75
5.7
3,058
yeast gives the desired proofed
85
4.3
2,975
volume in 60 minutes at 41°C
95
2.4
2,810
(105°F), only 3.0% yeast is
105
1.2
2,694
needed for 60 minutes at 46°C
115
0.5
2,579
(115°F). But what of the effect
125
0.5
2,365
on loaf volume (ovenspring)
and quality?
A study of the influence of proof temperature (Siffring and Bruinsma,
Cereal Chemistry, 70:351, 1993) on finished quality of a variety pan bread
used the sponge-and-dough method, with 2.5% compressed yeast on the
sponge side. The 1-lb loaves were proofed to a height of 0.5 in. above the pan
rim in 50 to 55 minutes. Additional yeast was added at the dough mixing
stage to maintain this proof time at each of the experimental proof temperatures. The results in loaf volume are instructive, as seen in the table ("Loaf
Volume at Various Proofing Temperatures"). It was reported that as proof
temperatures increased the crumb grain and texture of the bread declined
in quality.

During baking, heat energy does several things. This graph shows data obtained
for cookie baking. The area under the "dough heating" and "water evaporation"
curves relates to the heat distribution. The estimate is that dough heating takes
up about 35% of the heat input, water evaporation takes up about 60% and
freeing "bound water" (mainly water associated with the swollen starch granules)
accounts for the
other 5% of heat
energy. Weight
loss is due primarily to water
evaporation.
How should
heat zones and
dampers be
set in a zoned
oven? This varies somewhat
according to
the nature of
the oven band, the product being made and the desired final characteristics. A
few general rules of thumb are:
* Initial zones: high bottom heat, low top heat, dampers closed. The idea is
to maximize leavening action, which is accelerated by heat conducted from the
band, while minimizing the setting reaction in the crust.
* Middle zones: equal top and bottom heat, dampers closed. This finishes internal baking and begins setting the crust to stabilize the final product dimensions.
* Final zone: low bottom heat, high top heat, dampers open. Crust browning
is the main desired reaction at this point, along with moisture removal, which is
facilitated by opening the dampers, hastens it.

For more information, see Page 162

May 2004/ BAKERS PRODUCTION MANUAL / 99

Baking & Snack - May 2004

Table of Contents for the Digital Edition of Baking & Snack - May 2004