Spoilage types in shelf life
Bakery Academy explaines the three most common types in bakery.
Moulds are the major spoilage problem for bakeries. They are responsible for big costs due to losses of raw materials and end products. These microorganism are a type of fungi that consists of multiple cells in contrast to yeasts, which are single celled. Moulds favor the presence of water. Appearing frequently in bakery products with a high water activity level such as bread, cakes and creams.
Besides the moulds that grow at a relatively high water activity, there are some moulds that can grow in bakery products with a low water activity, such as fruited cakes and fondants. Xerophilic moulds, Eurotium Amstelodami and Eurotium Chevalieri are examples of extremophilic species that are usually the first fungi to colonize, allowing in a later stage other species to grow on these products.
Overall losses of bakery products due to mould spoilage vary between 1-5 % depending on seasons, type of products and methods of processing. The mould spore counts are higher in the summer months than during winter due to airborne contamination in the warmer weather and more humid storage conditions. Mould spores are generally killed by the baking process. However, this does not apply for the eventual formed mycotoxins (mould species) during cultivation and storage of raw materials. Mycotoxins are very stable compounds that can resist temperatures between 200-300 ̊C.
Spoilage by bacteria
Bacteria also have a potential to contaminate baked products. The spores of Bacillus subtilis for example are heat resistant and will not be killed by the baking process. Several Bacillus species can contribute in the process that makes bread ‘ropy’, like Bacillus cereus. Warm humid conditions are perfect for the spores to germinate and grow, forming the characteristic stringy brown mass with the odor of fruit. As the spoilage continues, the crumb is degraded and becomes soft and sticky due to the production of extracellular slimy polysaccharides typical of ‘rope’.
Spoilage by yeasts
Next to moulds and bacteria, less obvious microorganism can be involved in the spoilage of bakery products namely: yeasts. Problems caused by yeasts can be divided into two types. The first type are visible yeasts. Which grows on the surface of the bread in white or pinkish patches. Surface spoilage on bread is mainly caused by Pichia burtonii. Whereby white spots are visible leading to the term ‘chalk’ bread. Fermentative spoilage can occur, associated with alcoholic and essence odors and hence osmophilic yeasts. Such as Zygosaccharomyces rouxii, that are used to live in high sugar concentrations such as highly sugared toppings and fillings.
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