This article is from the Food Preserving FAQ, by Eric Decker firstname.lastname@example.org with numerous contributions by others.
A preliminary study showed baking at 177 C (350 F) for 30 min and at 204
C (400 F) for 50 min to be respectively the minimum and maximum treatments
that would result in an acceptable product. Acceptability, defined as any
product that was not underbaked (grayish crust, doughy) or burned (black
crust, dry), was determined by a consensus of four taste panelists.
Gisslen (5) recommended baking of the product at 1910C (3750F) for about
50 min. However, given the possibility of temperature gauges and human
preference as to degree of doneness, different baking treatments with
regard to product acceptability were investigated: baking at 1770C for
30, 40 and 50 min, at 191 C for 45, 50 and 55 min and at 204 C for 40,
45 and 50 min. Baking was done in a rotary type Hearth oven (National
Manufacturing Co., Lincoln, NE) calibrated with a mercury thermometer
and preheated to the desired temperatures. Baking times were measured
from the time the oven was equilibrated to the desired temperature.
Because use of thermocouples was not possible in the rotary oven,
product temperature at the center of the bread was monitored in
representative jars by inserting a mercury thermometer in the batter and
taking readings through the oven's glass window at 10 min intervals.
After baking, the jars were immediately sealed and allowed to cool at room
temperature (23 to 25 C). Because of their greater acceptability by
preliminary evaluations of taste panelists, samples of products baked
at 177 C were stored for 90 days at room temperature (23 to 25 C) or
in a LablineTM incubator (Labline Co., Chicago, IL) at 35 C for
extended evaluation. The latter storage condition was chosen to
mimic extreme summer weather conditions that would result in
temperature abuse of the product.
Vacuum level, pH and A,a
Vacuum level inside the jars was measured using a Ametrex U.S. Gauge
Division vacuum gauge (Metek, Sellersville, PA). With an AccumetlM pH
meter (Fisher Scientific Co., Pittsburgh, PA) final pH of the bread
was measured using a suspension of 10 g sample mixed with 90 ml of
distilled water. Water activity of the center portion of the bread
was measured using an AquaLab Model a~ meter (Decagon Devices, Inc.,
Pullman, WA). All readings were taken in duplicates.