Barley starch acid hydrolysis

Barley starches exhibit a relatively high rate of acid hydrolysis during the first 10 days, followed by a slower rate thereafter.28,39 The extent of degradation follows the order waxy > normal > high-amylose (Table 16.6). This order is similar to that... 

Table 16.6 Acid hydrolysis of native barley starches with 2.2 N HCI at 350C...

Figure 16.10 Acid hydrolysis of (a) small and (b) large granules ofwaxy, normal and high-amylose barley starches. (Adapted from reference 42 with permission)...

Youa, S. and Izydorczyk, M. (2007). Comparison of the physicochemical properties of barley starches after partial a-amylolysis and acid/alcohol hydrolysis. Curbohydr. Polym. 69(3), 489-502. 

Maltose can be obtained, among other products, by partial hydrolysis of starch in aqueous acid, (-f )-Maltose is also formed in one stage of the fermentation of starch to ethyl alcohol here hydrolysis is catalyzed by the enzyme diastase, which is present in malt (sprouted barley). ... 

The action of dilute acids on starch varies with the concentration, temi)craturc, and prc.ssure, resulting in its gradual hydrolysis or saccharilication. The same result is obtained on starch paste by various enzymes, the most active of which are the diistase of malted barley, the ptyjUin of saliva, aud the pancreatic juice ferment (trypsin). The starch is first converted into soluble starch, then into dextrin and maltose, and finally, on prolonged action, into glucose. 

Maltose, or malt sugar, is produced during the hydrolysis of starch and glycogen by dilute acids or enzymes. It is produced from starch during the germination of barley by the action of the enzyme amylase. The barley, after controlled germination and drying, is known as malt and is used in the manufacture of beer and Scotch malt whisky. Maltose is water-soluble, but it is not as sweet as sucrose. Structurally it... 

Fig. 168. The effect of gibberellic acid on the hydrolysis of starch in the embryo-free half of barley grains (modified from Plant Research 66).

---