THEIN VIVOANDIN VITRODEGRADATION OF BARLEY AND MALT STARCH GRANULES

Abstract

The susceptibilities to amylolytic hydrolysis of the two different types of starch granule in barley and malt have been investigated. The large and small granules from both germinated and ungerminated grain were subjected to the sole action of malt a-amylase under conditions which otherwise simu lated those of a conventional infusion mash.Large starch granules from barley are hydrolysed at a slower rate than those from malt. The faster conversion of the latter is attributed to prior modification of the starch granule structure during germination. The small granules from barley are extremely resistant to attack by a-amylase and even pre-cooking does not appreciably increase their susceptibility to amylase attack. Although the small starch granules from malt are less susceptible than the corresponding large granule fraction, they can be hydrolysed to a greater extent than can the small granules from barley. The increased susceptibility of small granules from malt is probably due to the partial removal of their protecting surface layer of protein.Although during malting the small granules of barley are hydrolysed more rapidly than the large granules, the situation is reversed during mashing. Very little loss of extract can be attributed to the enzymic resistance of small starch granules in all-malt mashes. If raw barley is used in the grist, sub stantial amounts of small starch granules may remain in the mash.

Gelatinisation Characteristics and Enzyme Susceptibility of Different Types of Barley Starch in the Temperature Range 48-72°C1

“…There is little difference in the gelatinisation temperatures (Tm amylopectin) of barley and malt starches 13 . Therefore, the values of Tm amylopectin shown in Table I should mirror those that might be expected from starches isolated from malted samples of the corresponding barley lines but gelatinisation of malt starch may start at lower temperatures than that of barley starch 5 . The DSC runs were carried out at a solids content of 17% (w/w) to mimic the starch content in typical high gravity mashes.…”

Molecular basis of barley quality

“…The level of this enzyme is not usually detectable in barley but increases once germination commences (Bathgate and Palmer 1973). In most cereals, the α-amylase I (Amy2) form appears shortly after anthesis.…”

Effect of Different Steeping Conditions on Endosperm Modification and Quality of Distilling Malt

“…Despite the pioneering studies on barley which date back to over a century, for example, in the 1900s 53 , in the 1920s 19 , in the 1950s 29,51 , in the 1960s 33 and studies by scientists of the 1970s to the present day 4,6,[12][13][14]18,[20][21][22][23]27,28,[30][31][32][35][36][37][38]40,41,44 , the complexity and incompleteness of our knowledge of grain physiology have resulted in continuous research on cereals, with research studies on barley and malt receiving the most attention when compared to other cereals. This is because of the pivotal role malted barley plays in many applications in the food, alcoholic and non-alcoholic beverage, baked products and the spirit industries.…”

“…The friabilitimeter was introduced in the early 1980s as a mechanical test to assess the uniformity of endosperm modification of malt samples 24 , although friability scores do not always correlate to brewhouse performance 1,26,27,45,47 . The extensive research into barley has led to a better and in-depth understanding of the physiology of barley and malt 4,6,[12][13][14]18,[20][21][22][23]25,[27][28][29][30]31,32,[35][36][37][38]40,41,44 . As a result, experimental observations and conclusions have been drawn and accepted as a pattern of behaviour for barley and malt.…”