PLANT DIASTASE IN EVIDENCE AS TO THE FORMATION AND STRUCTURE OF STARCH GRANULES

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Abstract
Plant diastases are divided into 2 groups which are differentiated in part by their relative activity in substrates of different pH at higher temps. One (reserve diastase) is typical of flour from mature ungerminated wheat, and of certain other reserve substances. At 60[degree]C its sugar forming activity is much greater at pH 4.5 than at 62. With the other (vegetative diastase) the reverse is true. This latter consists of 2 types, a predominantly sugar forming and a liquefying type. It is generally distributed throughout the vegetable kingdom and is most abundant in parts where vegetation is most active. Liquefying diastase acts rapidly on starch paste and may cause it to become water thin and clear with the production of almost no sugar. Some is active even at the temp. of boiling water. Below temps. of gelatinization it removes the coating from natural uncooked starch and, with that from the potato, so releases the interior that parts of an organized structure are exhibited. These show distinct lines of demarcation from the hilum to the surface. Many starch granules in formation begin with an agglutination of starch substance. This becomes gradually inclosed in a coating which forms around it and which is of a material suitable to protect the enclosed from ready solu- tion. Growth of granules often takes place by including within the coating new masses of starch aggregate. With potato starch the organization into segments appears to take place largely after the coating is formed. Before organization the interior is dissolved by diastase from different sources, leaving much of the coating as a shell. Steps in starch formation and disintegration are illustrated by reproductions of 28 photomicrographs.

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