Keeping molds, bacteria at bay
|High-volume bakeries can use a variety of
preservatives and preservative delivery systems to ward off mold
and bacteria growth.
Many people find that sitting in a warm, moist sauna is a great way to relax and unwind. Likewise, most molds and bacteria find that sitting in a warm moist loaf of bread or package of tortillas is a great way to thrive and multiply.
A combination of ambient temperatures, pH levels in the range of 6.5 to 7.5, and water activity in the range of 0.75 to 0.98, provide the perfect environment for tainted bakery foods. Mold and rope bacteria represent two common culprits in bakery food spoilage, and their presence in bakery foods turns off customers and creates a major economic impact on wholesale bakeries.
To prevent mold and bacteria growth, high-volume bakers must implement a series of quality assurance measures that begins with a solid HACCP program and ends with the ideal preservative and preservative delivery system.
Eliminating mold, bacteria
To control spoilage microbes in a plant environment, high-volume bakers should first install a HACCP plan. A solid HACCP program promotes thorough cleaning of production equipment, and monitors plant moisture, temperature, and air flow to minimize conditions for mold growth. Wholesale bakeries also must carefully scrutinize raw materials and rework, which are potential sources of contamination.
The next step in mold prevention is formulating products with pH and water activity levels that minimize microbial growth. Most chemical preservatives used in bakery foods increase in effectiveness as product pH is lowered because more of the organic acids, which are the active components of the preservative, disassociate at lower pH levels. Simply reducing the pH of a corn tortilla from 5.2 to 5.0 can add about 12 days to a product's shelf life.
Bakeries also must monitor a bakery food's water activity to determine the ideal way to prevent mold and bacteria growth. Higher water activity promotes microbial growth, and bakery foods vary in water activity levels depending on the product. Cookies and crackers generally have a water activity level of 0.20 to 0.30, and breads and rolls' water activity level typically hovers in the range of 0.96 to 0.98.
The final step to inhibiting mold and bacteria growth is selecting the ideal preservative and preservative delivery system to optimize shelf life, cost effectiveness and consumer acceptance.
Calcium and sodium propionate inhibit a broad spectrum of mold and rope bacteria while increasing the shelf life of bakery foods. Compared to other preservative options, propionates minimally impact yeast, making them the ingredient of choice for yeast-raised products and tortillas. However, calcium propionate, which is most effective at a pH of 5.5 or lower, may adversely affect baking powder. As a result, sodium propionates are more frequently used in chemically leavened products.
"In breads and rolls the common usage level for calcium propionate is between 4 and 6 ozs. per hundredweight of flour," one preservative supplier says. "Purity levels of commercial propionates vary considerably so always check with the supplier for actual content."
To minimize the inhibitory effect of calcium propionate, bakers can choose to add this preservative to the dough at the mixing stage rather than the preferment stage.
Spurred by a paper from American Institute of Baking detailing some of the benefits of liquid calcium propionate, this once little-used preservative delivery system is receiving more attention from the wholesale baking industry.
Liquid calcium propionate provides a 1:1 replacement for dry calcium propionate. "A liquid product eliminates dust in the bakery, thus improving the employee environment," one preservative supplier states. "A liquid system can also streamline operations to eliminate weighing and addition errors."
Although both liquid and dry calcium propionate are derivatives of the same compound, they possess different attributes. Liquid propionate has a slightly acid pH compared to dry calcium propionate's alkaline pH.
According to the American Institute of Baking study on sponge and brew dough methods, liquid propionates reduce proof times, increase gas production, improve finished bread volume and produce breads with a more closed, even grain compared to dry calcium propionate. These studies also showed that adding liquid propionate to the sponge or brew side of the dough has a stimulating effect on yeast and allows as much as a 25% reduction in yeast content.
An automated liquid preservative system injects liquid calcium propionate into a water line for ideal dispersion and effectiveness. For older, less automated bakeries, setting up a liquid propionate system requires the installation of an application pump to inject the preservative into the water line. For highly-automated plants controlled by PLCs, the only installation requirement should be the reprogramming of the system.
"A large bakery will see tremendous economic benefits by installing a bulk tank and receiving bulk deliveries," a liquid preservative supplier says. "This eliminates the costs associated with packaging into smaller containers and frees up valuable warehouse space and eliminates handling."
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