Yeast Flashcards
What are brewing yeast?
Yeast are nonphotosynthetic unicellular fungi (Saccharomyces)
How do yeast uptake food and nutrients?
In aciduric aqueous solutions yeast absorb dissolved vitamins, minerals and simple nitrogenous matter (amino-acids and very simple peptides) through their hemicellulose cell membranes.
What do yeast use metabolic pathways to generate?
Yeast use metabolic pathways to break down amino acids to nitrogen and sugars to carbon.
Fact on oxygen
Yeast obtain dissolved oxygen for metabolism or remove oxygen from other molecular compounds
What is fermentation?
During fermentation simple sugars are reduced to alcohol and carbonic gas in the presence of a constitutive intracellular enzyme group called zymase. Zymase enzyme is responsible for fermentation of sugar.
What type of sugars do ale yeast ferment?
Ale yeast ferment glucose, fructose, mannose, galactose, maltose, sucrose, xylulose, and maltotriose and they will partially ferment the trisaccharide raffinose.
What type of sugars to lager (Saccharmyces Carlsbergensis) yeast ferment?
Lager yeast ferment glucose, fructose, mannose, galactose, maltose, sucrose, melibiose, xylulose, and maltotriose and fully ferment raffinose.
Is lactose fermentable?
Lactose is not fermentable by saccharmyces cerevisiae
Yeast fact on fermentability of sugar
All sugars but monosaccharides need to be reduced by enzymes before they can be fermented
What is sucrose reduced to?
Sucrose is split into glucose and fructose by invertase (sucrase)
What are maltose and maltotriose reduced to?
Maltose and maltotriose are reduced to gluscose by maltase (a-glucosidase)
What is the only disaccharide that is able to be absorbed by yeast?
Maltose is the only disaccharide that can be absorbed into yeast cell before being hydroloyzed. All other disaccharides need to be reduced to monosaccharides by excreted enzymes before they can be absorbed by yeast.
What compose yeast?
Yeast are constituted of proteins (especially volutin, a mucleo-protein), glycogen (a starchlike reserve), minerals, enzymes, and vitamins (especially B-complex)
What minerals do yeast need and where do they come from?
10% of the cell is calcium-based and requires renewal as do the minerals and trace elements that account for 5% of its structure.The other minerals include phosphorus and potassium, magnesium, sodium, and sulfur. Magnesium and calcium sulfates supply the trace elements and calcium. Other trace elements includeing zinc, boron, and manganese are available from malt, hops, and water.
How do yeast reproduce?
Yeast reproduce by binary fission or budding
