Citrus processors are becoming increasingly aware of the importance of pectic substances in frozen citrus juices. Pectic substances are naturally occurring colloidal stabilizers that give citrus juices a viscosity or consistency often termed "body" by the fruit juice industry. When a citrus juice lacks these colloidal pectic substances the suspended cellular material settles rapidly and the juice is clear rather than cloudy. These thin-bodied jnices are commonly termed ((watery."Recently pectic substances became of vital interest to producers of frozen citrus concentrates when the problems of gelation and clarification were found by Rouse (9) to be related to the low-methoxyl pectin content. Gelation and clarification of frozen citrus concentrate are 2 related defects resulting from demethylation of pectin by the enzyme, pectinesterase.The importance of pectic substances to the quality of frozen citrus concentrates made it desirable to develop a rapid method f o r determining the type and quantity of pectic substances in these products. Basic investigational work on pectic substances and laboratory control procedures in concentrating plants have been hampered previously by the tedious nature of standard pectin analyses. The Carre and Haynes ( 3 ) calcium pectate method and the A.O.A.C. (1) pectic acid method are long analyses that require careful attention t o technique. The acetone precipitate method of Hinton (6) and the pectic acid precipitate method of Fellers and Rice (5) are simplified methods that give comparative values for samples within a series, but are not sufficiently accurate for determining the pectic content of citrus juices.Recently pectic substances in citrus have been determined by optical rotation (8) and the pectic substances in cotton have been determined by a colorimetric reaction with carbazole (10). The latter method was applied by Averill (2) to frozen citrus concentrate. Further modification of the colorimetric procedure led t o the development of the following method. The new method is rapid and well suited for routine laboratory analyses.The colorimetric determination of pectic substances is based on Dische's ( 4 ) carbazole-hexuronic acid-sulfuric acid reaction. Depending upon the type of standard, results may be expressed as anhydrogalacturonic acid, pectic acid, o r in terms of a stated pectin o r calcium pectate. It is desirable that the results be reported as anhydrogalact~~roiiic acid, since this is the basic structural unit of the pectin molecule.

No abstract

No abstract

In 1996, the Rail Transit Vehicle Interface Standards Committee was formed as a sponsor committee under IEEE. In IEEE jargon, a sponsor committee is a clearing-house for standards development in a particular subject area. Up to 1996, there was no committee that was actively developing rail transit standards in the electrical arena. This new committee was tasked with the goal of developing standards in an industry that has frequently been keen on customization. Over the last 11 years, the committee has developed 14 standards and has 14 additional standards that are near to completion. The end product will be a suite of standards that cover aspects of railcars, signal systems, overhead contact systems, and traction power substations. While these standards offer the collective advice of the industry, they cannot be blindly implemented. This paper will lay out the scope of the various published standards and provide a roadmap to their use.

Notes 1161 cellent paper on cocarboxylase has appeared. In that paper it was suggested that the use of silver might be avoided.