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This article is from the Food Preserving FAQ, by Eric Decker ericnospam@getcomputing.com with numerous contributions by others.


The safety of a home-style canned quick bread was investigated using spores
of Clostridium sporo genes putrefactive anaerobe (PA) 3679. Baking was done
at 177 C for 30, 40 and 50 min, at l91 C for 45, 50 and 55 min, and at 204
C for 40, 45 and 50 min. Products were analyzed for pH, water activity (a)
and vacuum level. The microbial quality of the products was determined
before and after baking. Of the products baked at 177 C, some were stored
for 90 days at room temperature (23 to 25 C) or in an incubator at 35 C to
study their shelf-life. Inoculated and endogenous vegetative cells and their
spores were counted before and after baking and after storage using Fungs
Double Tube method. Results showed germination of endogenous spores in
uninoculated products after baking at 1770C for 30 min and storage at 35
C for 90 days. Survival of inoculated C. sporogenes PA 3679 was detected
for all baking and storage treatments. Further work is recommended to
determine safe processing procedures for this type of product.

Key Words: Clostridium sporo genes PA 3679, home-canned breads, botulism.

Home-style canned quick breads have been featured in popular magazines
and promoted through mail order brochures and specialty shops. They are
typically manufactured by small home-based operations and the process
consists of oven-baking a batter in a wide mouth glass jar. Once baked,
the jars are removed and immediately covered with a two-piece lid. As
the product cools, a hermetic seal is created. The jars undergo no
further heat treatment and are stored at room temperature until
purchase and consumption. Two commercial samples purchased from a local
gift shop exhibited pH values of 7.2 and 7.4, and a of 0.95. Such
conditions coupled with favorable temperatures and the absence of a
chemical preservative could lead to the survival and growth of
Clostridium botulinum and production of toxins in the jars.
Dack (4) reported that white bread dough with an initial pH of 5.4
and 37% moisture inoculated with spores of C. botulinum prior to
baking and hot sealing developed toxin after 6 months of storage.
Although C. botulinum is the most critical microbial hazard in
canning, many inoculated pack studies used C. sporo genes PA 3679 as
the test organism. Clostridium sporogenes PA 3679 is a spore-forming
putrefactive anaerobe whose spores are more heat-resistant than those
of C. botulinum and its testing in such studies is safer because this
organism is non-pathogenic. The objective of this study was to
investigate the safety of a home-style canned quick bread by inoculating
the product with spores of C. sporogenes PA 3679 and challenging survival
and growth of the organism under different baking treatments and storage


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