Table Of ContentPURDUE UNIVERSITY
THIS IS TO CERTIFY THAT THE THESIS PREPARED UNDER MY SUPERVISION
BY ROBERT EDGERTQN HENZE
e n title d A STUDY OF THE CHEMICAL COMPOSITION OF APPLE
_____________________STORAGE VOLATILES______________________
COMPLIES WITH THE UNIVERSITY REGULATIONS ON GRADUATION THESES
AND IS APPROVED BY ME AS FULFILLING THIS PART OF THE REQUIREMENTS
FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
PffbFBssoR in Charge of Thesis
or School or D epartment
TO THE LIBRARIAN
THIS THESIS IS NOT TO BE REGARDED AS CONFIDENTIAL
GBAD. SCHOOL FORM »
A STUDY OF THE CHEMICAL COMPOSITION OF
APPLE STORAGE VOLATILES
A Thesis
Submitted to the Faculty
of
Purdue University
by
Robert Edgerton Henze
In Partial Fulfillment of the
Requirements for the Degree
of
Doctor of Philosophy
August, 1951
ProQuest Number: 27714281
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ABSTRACT
Apples are known to emit small quantities of organic
vapors during their normal storage life. The accumulation
of these apple emanations in the storage atmosphere
offers a serious source of flavor and odor contaminât ion
for other stored produce. In addition, some of these
volatiles have a detrimental physiological action on the
stored apples themselves. Increased ripening rates and
storage scald are believed to result from an accumulation
of certain of these volatiles in the storage atmosphere.
As a basis for determining the identity of the compounds
responsible for these physiological effects and for develop
ing more efficient methods of storage-air purification,
this study of the chemical composition of apple storage
volatiles was undertaken.
Since the identification of components in a complex
mixture depends upon the isolation of individual compounds,
the major problem encountered in this study was one of
separation. Fractional distillation did not result in the
desired separation of individual components. Prolonged
heating even at reduced pressures produced a marked change
in odor of the apple volatiles. Chromatographic methods of
separation were investigated and found applicable to the
problem, in the course of this investigation a direct
visual method of partition chromatography was developed
for separating and locating individual normal aliphatic
alcohols, to CQ , from a multicomponent mixture • The
alcohols were reacted with an excess of phthalic anhydride
and the resulting hydrogen phthalates chromatographed on
silicic acid. The method is especially useful for mixtures
in which compounds other than alcohols interfere with the
preparation or isolation of the 3,5-dinitrobenzoates♦
Apple storage volatiles extracted from activated
carbon in a commercial apple storage warehouse were analysed
for volatile organic compounds. The neutral fraction which
constituted 98 per cent of the total extract consisted
mainly of esters. The ester fraction on hydrolysis and
subsequent chromatography of the components on silicic acid
columns yielded six alcohol fractions and seven acid fract
ions. Methyl, ethyl, isopropyl, n-butyl and n-hexyl
alcohols were identified; an impure amyl was indicated
present. Propionic, n-butyric, n-caproic and n-caprylic
acids were identified; formic, acetic and impure valeric
were indicated present. The relative distribution of these
acid and alcohol components in the intact esters was not
determined.
The free acid and free alcohol fractions of the total
apple storage volatiles were found to contain essentially
the same compounds as esters. Normal caprylic acid was
found only as an ester component. Two alcohols of higher
molecular weight than hexyl were indicated present as free
alcohols but not as components of esters•
Acetaldehyde, acetone and propionaldéhyde were ident
ified in a sodium bisulfite extract of apple storage vol
atiles. Fifteen other unidentified carbonyl compounds
were separated chromâtographically as their 2,4-dinitro-
phenylhydrazone derivatives and their absorption spectra
determined.
ACKN OT/VIaEDGtEMENT
The writer wishes to express his sincere appreciation
to Dr. F. W. Quackenbush and Dr. G. E. Baker for the
advice and assistance given throughout the course of this
investigat ion•
TABLE OF CONTENTS
Page
I. GENERAL INTRODUCTION................................ 1
II. APPLE STORAGE VOLATILES FROM ACTIVATED CARBON
USED IN A COMMERCIAL APPLE STORAGE................ 7
1. Collection and Extraction of Volatiles..... 7
2. Determination of Physical and Chemical
Properties of Apple Storage Volatiles....... 10
3. Results and Discussion...................... 11
III. THE SEPARATION AND IDENTIFICATION OF FREE ACIDS
IN APPLE STORAGE VOLATILES......................... 13
1. Introduction....................... ... ......15
2. Experimental...................................14
3. Results and Discussion....... 15
IV. THE SEPARATION AND IDENTIFICATION OF FREE
ALCOHOLS IN APPLE STORAGE VOLATILES................ 20
1. Introduction.......... 20
2. Experimental ............*............. 21
3. Results and Discussion...................... 25
V. THE SEPARATION AND IDENTIFICATION OF ALCOHOL
AND ACID COMPONENTS OF ESTERS IN APPLE
STORAGE VOLATILES.................................. 33
1. Introduction...................................33
2. Experimental............ ••• 35
3. Results and Discussion. ............ 36
Page
VI. THE SEPARATION AND IDENTIFICATION OF CARBONYL
COMPOUNDS IN APPLE STORiiCE VOLATILES............... 40
1. Introduction................................ 40
2« Experimental.............................. 40
3. Results and Discussion........................43
VII. GENERAL DISCUSSION.................................. 49
VIII. SUMMARY-............................................. 53
IX. BIBLIOGRAPHY....................................... 55
