Staling of Bakery Products and Mold Infection
There are three ways in which bakery products stale.
- Starch Retrogradation (firming of the crumb)
- Getting infected by molds
In simple terms, staling of crumb (firming of crumb) is the process the starch molecules go through when they shrink upon cooling. Starch molecule consists of a very long chain of Carbon, Hydrogen and Oxygen that are stretched out when warm and feel soft. Upon cooling, the chain shrinks and thus become firm which is called staling. You have probably experienced that when a stale product is warmed, it becomes soft. The starch chain has stretched again. Upon cooling, it shrinks again and become firm.
For the past several years bakers used emulsifiers called bread softeners to produce bread that will remain soft for a longer period of time. It is added to the dough during mixing. Some of the more common ones are monoglycerides, calcium stearoyl lactylate, and sodium stearoyl lactylate. The softening action takes place after the bread is baked. Also, Potato bread will resist staling because potatoes act as anti-staling ingredients to some degree. Some anti-staling ingredients also perform as dough conditioners or dough strengtheners.
Enzyme manufacturers are hard at work on generic engineering and protein engineering producing enzymes to extend the shelf life of bread many fold. In a paper presented at the 1999 American Society of Baking's Annual Convention, it was stated that some of these enzymes are available now. However, since every baker wants to have one better, enzyme manufacturers will continue to work on developing better ones. It was also stated that there is a lag time of between 2 and 3 years between the time a specific enzyme is identified and actually having it available for the baker to use.
Advantages of Using Enzymes instead of Chemicals. Since enzymes are produced from natural ingredients, they will find greater acceptance by the housewife than when chemicals are used.
Mold and Mold Inhibitors.
Sanitation plays a very important role in preventing mold in bread. Mold spores do not survive baking temperatures. The interior of the loaf, when it comes out of the oven is about 210 to 212 degrees F. which will destroy any mold spores which may be present in the dough. Therefore, bread and other bakery products can only be contaminated after they leave the oven.
Some of the more dangerous areas for mold contamination are storage rooms, and slicing machine blades which come in direct contact with the interior of the loaf where there is an abundant supply of food and moisture. Mold spores also thrive in dark places. You can extend the length of time that it takes bakery products to mold by several days by using Mold Inhibitors such as Calcium Propionate for yeast raised doughs and sodium propionate in chemically leavened products. Propionates are present in many foods, but in very small amounts. Swiss Cheese, however is an exception. For this reason, Swiss Cheese rarely molds, unless it is improperly developed. Propionates may be obtained by the oxidization of propyl alcohol, forming propionic acid. The propionic acid is in turn combined with other chemicals to form the well known Sodium and Calcium propionates sold under different Trades Names. Mold Inhibitors react as an alkaline in doughs, and since yeast doesn't like an alkaline condition, Mineral Yeast Foods containing monocalcium phosphate are added to the dough. Monocalcium Phosphate reacts as an acid in doughs therefore counter-acting the alkaline which is formed by the propionates. Also, vinegar can be used at the rate of about 1 pint per 100 pounds of flour. Inhibitors are called inhibitors, because not enough is used to kill the mold. They only retard the growth of molds. Bread will mold eventually if kept in a warm moist environment. The amounts of Calcium Propionates to use in bread varies with the climate, season of the year, or type of product. Dark Breads require more than White Breads. For average climates, 2.5 to 3.5 ounces are used per 100 pounds of flour in White Breads and 4.0 to 5.0 ounces are used in Dark Breads.
Types and Color of Molds.
There are many different types of molds and they have different colors. Mold spores are practically everywhere, because they are very tiny and are carried in the air. They are so tiny that they can only be seen under a microscope. Mold Spores are like seeds that you plant in the garden. When they come in contact with the proper food, moisture and warmth, the spores produce mold plants which you can see with the naked eye.
Rope is a bread disease caused by the bacteria, Bacillus mesentericus. This disease breaks down the cells of the bread and leaves a sticky, pasty mass. When the crumb is pressed together, and pulled apart, it will stretch into long, sticky, web-like strands. The product will have the odor of over-ripe cantaloupe. The rope bacteria are too small to see with the naked eye, but they can be seen with a microscope. The bacteria can be present in the ingredients, especially flour and yeast. Unlike mold, rope spores are not destroyed by baking temperatures. Calcium propionate, sodium diacetate or one pint of vinegar per 100 pounds of flour can be used in bread doughs to increase the shelf life of the product. If the bakery is contaminated, thorough cleaning with special chemicals will be necessary and/or the bakery may have to be steam cleaned.
NOTE: SODIUM PROPIONATE IS USED IN CAKE BAKING (NOT CALCIUM PROPIONATE).
To lower the Ph to 6.5 (Most effective Ph) in cakes when using Sodium Propionate is to use an acid ingredient and then you would have to do some experiments to determine how much to use.
Some of the acid ingredients which you might use in the event you wanted to try to lower the Ph of your products are listed below.
- Monocalcium phosphate
- Anhydrous monocalcium phosphate, has greater stability by being coated with potassium and aluminum phosphates.
- Sodium aluminum phosphate.
- Cream of tartar or potassium acid tartrate.
Representative Ph ranges of various types of finished cakes (not their batters) follows: White layer cakes 7.0 to 7.5; Devil's food cake 8.0 to 9.0; Angel food cake 5.2 to 6.0; yellow layer cake 6.7 to 7.5 and chocolate cake 7.5 to 8.0.
One Text Book on Baking (Breadmaking Technology) by Wulf T. Doerry published by the American Institute of Baking recommends using a 5 percent solution of potassium sorbate to spray the products as they leave the oven. This method is quite effective against mold growth, since the preservative is concentrated on the surface of the product where recontamination with mold spores takes place. Sorbate Spray Applicators are available for spraying the potassium sorbate solution.
One text book (Baking Science and Technology), Third Addition, Volume 1 by E. J. Pyler published by Sosland Publishing Company suggest using 0.03 to 0.125 percent of Sorbic Acid based on batter weight in cakes, pies. pie fillings, fruit cakes and icings. At that level it will not affect the taste and flavor of the finished product. The problem with sorbic acid is that it is not effective at high Ph (9.0 or higher) such as in devils food cake.
Acknowledgments. Material on Mold and Mold Inhibitors was also derived from the following sources:
1. A Treatise on Baking by The Fleischman Division of Standard Brands, Inc.
2. Conversion Factors and Technical Data of the Industry by The Research Department, Pillsbury Mills, Inc.