IN order to follow the changes which take place in the pectic constituents of stored apples, a number of preliminary investigations have been found to be necessary. In the first place a method was required by which pectin could be estimated accurately in dilute solution. This having been established, it has become possible to proceed to an investigation of the means by which the various pectic constituents of the fruit can be separately extracted. The present communication, in so far as the extractions are concerned, is confined to an examination of methods for extracting the soluble pectin of fruits. The difficulties which are encountered in the course of this extraction are almost entirely mechanical-difficulties inseparable from the process of washing out this soluble colloidal material from the insoluble colloids of the cell wall with which it is intimately associated. The clearing up of these mechanical difficulties is a necessary preliminary to any further investigation of methods of extraction, for unless suitable methods of washing out are adopted much soluble pectin may remain behind to form a mixture with the pectin dissolved out by subsequent treatment.It has been the general practice hitherto to estimate the pectin content of solutions by precipitating the pectin with alcohol. This method at its best is inconvenient and lacking in accuracy. The pectin obtained is necessarily of variable composition, since pectin probably exists in a number of forms intermediate between neutral pectin and pectic acid. Moreover, as dilution increases precipitation becomes increasingly difficult, until at very low concentrations no precipitate is obtained, even after prolonged standing with a large excess of alcohol. By the method now adopted the difficulty of precipitation is avoided, for calcium pectate can be made to flocculate from solutions of very low concentration, and a product of definite chemical composition is obtained. A comparison of the results of precipitating pectin with alcohol and as calcium pectate is given in the sequel.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.