Abstract
In the brewing process, the consumption of resources and the amount of waste generated are high and due to a lot of organic compounds in waste-water, the capacity of natural regeneration of the environment is exceeded. Residual yeast, the second by-product of brewing is considered to have an important chemical composition. An approach with nutritional potential refers to the extraction of bioactive compounds from the yeast cell wall, such as β-glucans. Concerning the potential food applications with better textural characteristics, spent brewer’s yeast glucan has high emulsion stability and water-holding capacity fitting best as a fat replacer in different food matrices. Few studies demonstrate the importance and nutritional role of β-glucans from brewer’s yeast, and even less for spent brewer’s yeast, due to additional steps in the extraction process. This review focuses on describing the process of obtaining insoluble β-glucans (particulate) from spent brewer’s yeast and provides an insight into how a by-product from brewing can be converted to potential food applications.
Highlights
This review focuses on describing the process of obtaining insoluble β-glucans from spent brewer’s yeast and provides an insight into how a by-product from brewing can be converted to potential food applications
It is known that in the fermentation process of beer, yeasts use for biogenesis approximately 10% of fermentable sugars from the environment [43]. This energy is stored in a 200 nm thick wall in the form of carbohydrates, which are of high interest in food processing or as food contact materials (FCMs) [44,45,46]. 85%–90% of the wall polysaccharides consist of a mixture of water-soluble mannans, soluble glucans (10–48%) and alkali-insoluble (15–48%), as well as minor amounts of chitin [47]
Apart from the adaptive response to stress, which depends on the metabolic conditions of cells [60,81] during the fermentation, the carbon source from the media influences the polysaccharide composition of the cell wall. Such changes during fermentation were highlighted by an ultrafine section of yeast samples with a diamond knife and examined using a transmission electron microscope (TEM), in which it was clearly observed that the thickness of the cell walls after replication increased [33]
Summary
Β-glucans are polymers of glucose with different types of glycosidic linkages and anomeric configurations [11] These glucans act as a barrier with the main role in supporting the cell wall due to a rigid structure of β-D-glycosidic bonds that are interconnected with other glucose chains, through the β-1,3 and β-1,6 bonds [12]. Insoluble β-glucans found in yeast refers to those that have a fibrous backbone consisting of β-1,3-glucan chains branched to β-1,6-glucose polymers. Of these glucans, other components of the wall are bound with low content in chitin or mannoproteins [17].
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