HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Brunner, J. R. Articles by Thompson, M. P. Search for Related Content PubMed Articles by Brunner, J. R. Articles by Thompson, M. P.

Characteristics of Several Minor-Protein Fractions Isolated from Bovine Milk¹

Department of Food Science, Michigan State University, East Lansing

ABSTRACT

Four minor-protein fractions were isolated from the same source of skimmilk by methods similar to those reported by Rowland for proteose-peptone, by Aschaffenberg for -proteose, by Jenness for milk component 5, and by Weinstein for the minor-protein fraction. A fifth fraction, the soluble membrane-protein, a constituent of the fat/plasma interfacial layer, was isolated from washed cream.

These fractions were characteristically low in nitrogen (10–14%), high in ash (3–7%) and phosphorus (0.6–1.5%), and contained hexose sugars. Free-boundary electrophoretic patterns demonstrated variable multicomponent systems containing what appeared to be a common major component. Sedimentation velocity diagrams of the skimmilk fractions revealed two apparently common boundaries, whereas the diagrams for soluble membrane-proteins showed more heterogeneity, suggesting that the constituent components differed from those of the skimmilk proteose-peptones.

The proteose-peptone, -proteose, and minor-protein fractions were rennin substrates. Heating (90° C.-30 min.) 1% solutions of milk component 5 concentrate and the soluble membrane-protein, two fractions obtained from raw milk without employing a heat-treatment step in the isolation procedure, produced changes in both the electrophoretic and sedimentation patterns. Further, heated milk component 5 concentrate was more susceptible to the action of rennin than its unheated counterpart. The membrane fraction was unaffected by rennin.

¹ Michigan Agricultural Experiment Station Journal Article No. 2693.

² This article is a part of a dissertation presented to the Faculty of the College of Agriculture in partial fulfillment of the requirements for the degree of Doctor of Philosophy.

³ Present address: Eastern Utilization Research and Development Division, USDA, Philadelphia, Pennsylvania.