Staling or firming causes baked goods to lose their freshness and initial eating qualities.1 Depending on the product, staling involve both crumb and crust:
Harsh, dry and crumbly
Increased hardness and firmness
Deterioration of taste and aroma
Loss of moisture via migration from product core to crust
Loss of crust crispness
Along with mold contamination, staling is the main reason for bread waste in the world. Also, it is the greatest challenge for shelf-life extension and can have serious economic consequences for large scale bakeries.
Staling was once thought to be only caused by moisture loss from baked products. This theory was quickly disproved over 150 years ago. Now, it is associated with the retrogradation or recrystallization of starch molecules. It can even occur without water loss from the crumb.
How staling works
Staling occurs in products that contain starch, such as bread, buns and cakes. It begins immediately after bread comes out of the oven. Then, gelatinized starch starts to cool down to an ambient temperature and solidify, leading to retrogradation and molecular realignment.
Retrogradation of amylopectin in bread is a slow process. It is believed to be the major contributor to staling during storage. On the other hand, amylose retrogrades very quickly, during bread cooling. This is an advantage in slicing loaves without the product collapsing.1,2
Approaches to reduce staling in bakery products
Consumers often squeeze a loaf of bread before buying it to check its freshness. In this situation, they are assessing the elastic deformation of the loaf. A soft yet springy texture tells the consumer the bread is fresh. If the bread is too firm, the loaf is rejected as stale.
Strategies for delaying staling in bread are:1,2,3
Emulsifiers as crumb softeners: do not produce softer fresh bread, but they do slow the rate of firming over time.
Amylases: maltogenic amylases of intermediate thermostability from fungal or modified bacterial sources can break down starch into dextrins and sugars. The latter can penetrate the starch helix structure and inhibit the realignment process.
Lipases: clean label emulsifier replacements which break down lipids to produce mono- and diglycerides that function as crumb softeners.
Hydrocolloids (gums): they bind and hold water, preventing moisture migration and reducing the firming rate.
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