Neuere Beiträge zur Chemie der Stärkefraktionen. VII. Über die Stabilität der Amylose‐Alkoholkomplexe

The structure of the amylose‐alcohol complexes has not been cleared up in a satisfactory way as the conformation of the glycopyranoside rings constituting the amylose helices, has not been ascertained so far. The various alcohols take place within the interior of the helices, form therefore no stable complexes such as e.g. the J?. The reason for this is most likely the fact that alcohol molecules do not fill out but a small portion of the windings of the helices. The water solubility of the aliphatic alcohols decreases with the increasing number of carbon atoms, while the length of the apolaric portion increasing accordingly. The inclination to form complexes increases consequently. In the case of alcohols with a more enbranched structure, the capacity of forming complexes is poorer. The formation of complexes is an endothermic process, being the result of distinct steps. The alcohol complexes, in contrary to the iodine complexes, can be perfectly hydrolysed by enzymes. Pure beta‐amylase is not capable of decomposing the butanol complex but very slowly, while mixtures containing both alpha‐ and beta‐amylase behave just as if only alpha‐amylase would be present. In the case of decomposition by means of such enzyme mixtures, the value of the reducing power belonging to the complete disappearence of the iodine binding power (the achromia R value) tends with increasing butanol concentration towards the achromia R value, characteristic for the decomposition by means of pure alpha‐amylase. The acid hydrolysis slows down in the presence of alcohols, too. The reason is probably the fact that the amylose‐alcohol complex presents a heterogeneous phase. Amylopectin hydrolyses quicker. This circumstance can become useful for the production of amylose from a paste of high concentration.