In this article we will discuss about the role of microorganisms in brewing and making of cheese.
The enzymes carry on hydrolysis of polysaccharides to monosaccharide’s or in glycolysis lead to formation of ethanol. In brewing also the starting material is the polysaccharide starch while in wine making the starting material is generally mono or disaccharides. The largest carbohydrates fermented by most of yeasts are tri-saccharides.
The main raw material used in brewing is the starch from barley. Therefore, the barley seeds are permitted to germinate which leads to release of amylase. The release of hydrolytic enzymes from germinating barley is shown in Fig. 41.3. The enzyme amylase leads to break down of starch. The starch grains are present in the cells of endosperm. The walls of the cells are surrounded by a number of polymers like 1, 3 -D-glucans.
It is needed to degrade these glucans so that the amylase may come in contact with starch granules. The release of some peptidases is also important which catalyze the degradation of endogenous protein releasing peptides and amino acids. The amino acids and peptides are required for the growth of yeast cells which occur at the fermentation stage.
The starch granules dispersed in water are maintained above 60°C to prevent gelatinization. Also the enzyme amylase has to be stabilized to remain active at this temperature. The pH is maintained 5 to 6 facilitated by addition of Ca2+ and having a high substrate concentration.
The amylases hydrolyse the α-1, 4 links found in amylose and amylopectin. It may be stated that amylopectin is polymer of D-glucose units linked α-1, 6 as well as α-1, 4 and constitute from 17 to 30 per cent of starch, the rest of that is amylose with α-1, 4 links only.
The hydrolysis of amylose and amylopectin leads to production of a mixture of glucose, maltose, maltotriose and higher un-fermentable sugars called dextrins α-Amylase is an endoamylase which randomly hydrolysis starch to dextrins while β-amylase which is an exoamylase attacks both starch and dextrins, from non-reducing end removing maltose units. However, neither attack a-1, 6 links present in amylopectin. The second stage consists of anaerobic glycolysis in which ethanol is the end product.