Extending shelf life on product lines
Minimizing staling and antibacterial contamination in baked goods.
by Dan Ettling
This is a break-out article from Help: The Market is Shifting
One key approach to limiting waste and maximizing profitability is to extend the shelf life or slow the staling of baked goods. Whether the baker is guaranteeing sales, wherein the unsold product is credited or returned as a loss to the producer, or simply shipping out or retailing, reducing the amount of “stale”, undesirable product prior to consumption is a key to business and profits. Further, extending the time that the customer is happy with the product and limiting the perception of “bad”, hard or molded product makes for more repeat business.
Staling or extending shelf life falls in two separate categories: mechanical staling and microbial contamination.
Minimizing Mechanical Staling
In the mid 1800s, a scientist baked bread in sealed glass tubes with plungers in them. The idea was to determine if and how much bread hardens over time even if all of the moisture is retained in the sample. By measuring the resistance of the plunger to being pulled through the baked bread sample at degrees of time, the conclusion that bread hardens even if it loses no moisture over time was confirmed. This represents the change in crumb structure and toughness inside a baked product. This has been identified as mechanical staling of baked goods and is a re-crystallization of starches into more linked structures, making the product feel harder in addition to trapping some water molecules as the matrix is enhanced. There are two general forms of starch in a typical flour based baked product. One is a very short linear chain known as amylose. These are easily re- associated during cooling of the product out of the oven and link up by the time the bread or cake is cooled after baking. The other is amylopectin, a very large and complex form of starches that are less available to each other and take more time to associate by linking chains. Simply put, much of the hardening of the bread, cake, etc., product over 1-5 days, and on, is mechanical re-crystallization and linking together of amylopectin and proteins. This mechanical hardening is what technology in formulating and production is directed at slowing.
The two approaches to reducing the rate of mechanical staling of breads and cakes, etc., are processing practices and ingredient usage in formulation.
With regard to processing, the tools are clear. Over and under mixing are detrimental to reducing the rate of staling while optimum mixing and hydration improve or slow the rate of mechanical staling. Fermentation is nature’s way of conditioning bread for slowed staling. Fermentation results in long periods of enzymatic reduction of starch and protein chains and results in less complex starch structures and increased water hydration going into and thus coming out of the oven. Further, fermentation results in byproducts such as organic acids etc., that also tends to make a medium less hospitable to microbes that result in mold. Faster baking thus resulting in meeting target internal temperatures of product coming out of the oven with minimum water bake loss is another tool that is often overlooked and not controlled.
Concerning ingredient in formulation as an approach to reduce mechanical staling, there are a number of tools available. Increased protein, whether from flour or other sources, enhances crumb and crust freshness. Optimum hydration is a key tool as not only will there be a benefit of having more water left in the product after baking but research studies have also shown that higher water levels do slow the action of mechanical re-crystallization. Higher sugar levels also helps. The proper use of enzymes serves to replicate the enzymatic conditioning of starch and protein structures in much the same way as natural fermentation. Some of the best tools we have are emulsifiers. Emulsification is the use of natural surface active agents that are attractive to both water and oil resulting in a significant improvement of the dispersion of these ingredients within the starch protein matrix during mixing and thus a significant reduction in the rate the matrix hardens.
Minimizing Microbial Contamination
Much has been made of various “mold inhibitors”. However, it is generally recognized by informed baking technicians that no matter how much “mold inhibitor” is placed in the formula as an ingredient, short of adding so much that it makes the product inedible, any product will mold if heavily inoculated enough between cooling and consumption. Sanitation practices are the only effective approaches to long term microbial stability.
My experience is that most producers of baked goods are using mold inhibitors in a way that limits their functionality. The most common are Sorbates and Propionates (generally from calcium, potassium or sodium). Propionates are thought to be somewhat effective at finished product pH levels of 5.5 and below. Therefore if a cake, bread or snack food is over the pH level of 5.5, and most are, the propionate will be of little help. Sorbates are deemed to be somewhat effective at pH levels of 6.5 and below, and the higher pH range as compared to propionate allows some functionality at slightly increased pH ranges but it still is limited in its practical use. One way to get more out of them is to use an acid of some type such as vinegar (acetic acid) or citric acid, etc., to lower the pH of a finished product into the functional range of the mold inhibitor used. This method has its limits: low pH products are typically light in color as they do not color up in the oven as well as higher pH products. This is why sourdough bread is typically very light in color. It is difficult to make chocolate cake low in pH, for example, as the high pH or alkaline cake batter colors well in the oven and the chocolate cake stays a rich dark color. This is the reason most cocoa is alkalized or “dutched” in processing. If one attempts to make chocolate cake low in finished pH the color can take on a lighter and somewhat reddish look.
Much is being made of water activity as a defense against microbial activity. However, this is one of the more costly in terms of quality and food cost ways of defending the product and label. There are more effective ways to do this than significantly reducing water activity.
Sanitation is the key to defending a label and product line against microbial activity.
Reducing the compromised product, waste and dissatisfied customers and increasing the quality and saleability of the baked goods produced can have a marked impact on the bottom line and profitability of the bakery. Every little bit helps and by being attentive to all of these little advantages, a profit can still be realized even as we struggle to adjust to the changing environment of food costs.
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