Solubility mutarotation measurement

When measured at 40° with Lintner s soluble potato starch, the ratio of the dextrinogenic to the saccharogenic activities is approximately 6 to 1 for the amylase of Aspergillus oryzae. This value is given by both crude and purified preparations of the amylase if the measurements are carried out under comparable conditions. This constancy in the ratio of these two activities has led to the conclusion that, like pancreatic amylase, the amylase of Aspergillus oryzae is not accompanied in nature by beta amylase. Reacting mixtures of the amylase of Aspergillus oryzae and starch exhibit alpha mutarotation.72... 

Equations similar to those for mutarotation have been derived, expressing the relationship between the solubility behavior of the two forms of lactose and the equilibrium or rate constants (Hudson 1904). The constants derived by both mutarotation and solubility methods are in agreement. The solubility equations have been used to develop procedures for measuring a- and /3-lactose in dry milk (Roetman 1981). 

With sugars that show simple a,j8-pyranose mutarotations, the proportions of the anomers may be estimated from optical rotations, as described on page 23 and given in Table III. Optical rotation data can be supplemented and confirmed by measurements of solubility and by evaluation of the data as described on page 18. 

A peculiar property of quininone (8) and quinidinone (9) is their easy epimerization which results in a characteristic mutarotation (9). In equilibrated solutions 8 and 9 exist in an approximately 1 1 mixture. The half-life of the equilibration of the dihydro analog of 9 was determined in various solvents 11). It ranged from 24 min in ethanol to 24 hr in cyclohexane as determined by measuring the rate of mutarotation. However, essentially complete conversion of quininone (8) into the less soluble quinidinone (9) can be effected by careful crystallization. 

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