The change in smell of sliced bread after being in the refrigerator for a while is due to a process known as "retrogradation" or "staling." Retrogradation is a complex chemical and physical process that occurs in starch-based foods like bread.
When bread is initially baked, the starches in the bread absorb water and form a gel-like structure, giving the bread its soft and moist texture. However, as the bread sits in the refrigerator, the starch molecules start to crystallize and recrystallize, leading to the retrogradation process. This crystallization causes the bread to lose moisture and become stale.
Several factors contribute to the retrogradation process:
Starch Retrogradation: Starch molecules in the bread realign themselves as they lose water, resulting in a tighter, more crystalline structure. This restructuring affects the texture and changes the aroma of the bread.
Loss of Moisture: Refrigerators are dry environments, and the cool temperature accelerates moisture loss from the bread. As the bread loses moisture, it becomes drier and less soft.
Staling Compounds: The breakdown of starch molecules during retrogradation leads to the production of staling compounds. These compounds can interact with other components in the bread, such as fats and proteins, contributing to the change in smell and taste.
It's worth noting that refrigerating bread is not the ideal storage method to maintain its freshness. While it can help slow down the growth of mold, the cold temperature accelerates the retrogradation process, leading to a faster staleness. For optimal freshness, it's better to store bread in a cool, dry place in an airtight container or wrapped in plastic wrap or aluminum foil.