What causes staling?

Answered by Paul Bowser

Staling is a common problem that affects many baked goods, including bread, pastries, and cakes. It is the process by which these products lose their freshness and become dry and hard over time. As a sommelier and brewer, I have encountered staling in both and , where it is known as oxidation. While the specific mechanisms of staling may differ between different types of products, the culprit that causes staling in baked goods is the starch component in the flour.

To understand how starch contributes to staling, it is important to first understand what starch is. Starch is a complex sugar that exists in flour in microscopically sized round granules. These granules contain two polysaccharides, or sugars, known as amylose and amylopectin. While both amylose and amylopectin play a role in the staling process, it is amylopectin that plays a major role.

When a baked good is fresh, the starch granules in the flour absorb during the baking process to form a gel. This gel helps to give the product its soft and moist texture. However, over time, the gel structure begins to break down, leading to staling. This breakdown is primarily caused by the amylopectin component of starch.

Amylopectin is a highly branched polysaccharide, meaning it has many branches and side chains. These branches make it more susceptible to retrogradation, a process in which the starch molecules rearrange themselves and form a more ordered structure. This rearrangement causes the starch molecules to crystallize, resulting in a loss of moisture and a stiffening of the product.

Furthermore, the retrogradation of starch is accelerated by factors such as temperature and humidity. Higher temperatures speed up the retrogradation process, while low humidity allows more moisture to evaporate from the product, exacerbating the staling process. This is why storing baked goods in a cool and dry place can help delay staling.

In my experience as a sommelier and brewer, I have seen the effects of staling in both wine and beer. In wine, oxidation is the primary cause of staling. When a wine is exposed to oxygen, it undergoes chemical reactions that can lead to loss of aroma, flavor, and freshness. Similarly, in beer, exposure to oxygen can cause off flavors and aromas, as well as a loss of carbonation.

The main cause of staling in baked goods is the starch component in the flour. The amylopectin in starch undergoes retrogradation, causing the product to lose moisture and become dry and hard. Factors such as temperature and humidity can accelerate this process. Understanding the science behind staling can help bakers and consumers take steps to delay its onset and enjoy fresher baked goods for longer periods of time.