RAW STARCH DIGESTION: A COMPARISON OF THE RAW STARCH DIGESTING CAPABILITIES OF THE AMYLASE SYSTEMS FROM FOUR ALPHA‐AMYLASE SOURCES^a

Abstract

Little is known concerning the enzymes responsible for the digestion of raw starch. It has been shown that ,&amylase does not digest raw undamaged starch (12, 15), which leaves a-amylase as the most probable agent. However, it also has been hypothesized that a special factor may be responsible for this action (1).Recent reviews comparing the properties of the amylases from various sources (6, 7) indicate a wide variability in the properties of the a-amylases between sources. Classification of the enzymes according to source (such as fungals, bacterials, etc.,) carries the implication that the enzymes not only vary with the class of organism from which they originate but also that those from related organisms are similar. However, though the enzymes froin one class of organism have characteristics enough in common to justify such classification, the a-amylases from related sources do vary (8) and should not be categorically considered alike.Most of the studies that have included a determination of enzymatic attack in raw starch have approached the problem from the point of view of the relative susceptibility of different starches. The wide variation in susceptibility was well known to the early researchers as indicated by Reichert 's (11) extensive review. Recently Booher, Behan and McMeans (2) studied the relative susceptibility of raw starches to digestion in the rat gut. Yamazalri and Ueda (16) determined the relative susceptibility of 14 different starches to attack by the "black koji" amylase. These studies confirm the earlier work showing that the raw cereal starches were the most easily digested and the raw root starches were the most difficult to digest.There has been little evidence presented of the relative abilities of enzymes from various sources t o digest raw starch. If the a-amylase is the component responsible f o r the digestion of raw starch it would seem probable that its action should correlate with the raw starch digesting action of a series of enzyme systems. However, a lack of correlation would not necessarily prove that the a-amylases are not the active agents but may merely indicate another variable in the action of the a-amylases. MATERIALS AND METHODSEnzyme sources. Four distinct classes of enzyme source-7 fungals, 3 bacterials, 3 pancreatics, and 3 malts-were used i n the preliminary survey for this study. With the exception of a n acetone precipitated barley malt preparation these were enzyme concentrates furnished by eight different commercial firms. For further study, one con-*Published with the approval of the Director as Paper No. 622, Journal Series, Nebraska Agricultural Experiment Station.

Activation of α-Amylase by Protein and Detergents1

“…The effect was believed due to the disruption of the granule rather than to an effect on amylase itself. A similar enhancement of amylase degradation of raw starch by the cationic detergent Roccal was reported [17].…”

Cold enzyme hydrolysis of wheat starch granules

“…Based on these results, barley enzyme reaches a high conversion at a much lower activity level, reinforcing the fact that it is the most cost effective enzyme. Sandstedt and Gates (1954) also showed that barley enzyme is more effective on an activity basis than either bacterial or fungal a-amylases for solubilizing corn starch granules…”

“…In that same time period, the barley and fungal enzymes solubilized 75% and 30% of the starch granules, respectively. Sandstedt and Gates (1954) also found that the bacterial enzyme was the most rapid enzyme source for corn starch granules followed by fimgal and barley enzymes.…”

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

“…These include α-amylase, β-amylase, limit dextrinase and α-glucosidase 20,21 . Although α-amylase is able to hydrolyse intact starch granules, the rate of hydrolysis is very slow compared to that of solubilised starch 27,29 . Effective hydrolysis by α-amylase, therefore, occurs only after the starch has been solubilised (or gelatinised).…”