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CfiCURRENCE Q? A ENTER PRBKCEPLE EN CARROTS

Thesis haw ”10 Degree 0‘ M. S.
MECHIGAN STATE UNEVERSITY

Arleigh Russell Dodson
1957

[I'HESIS
o, 2/

L 1BR A R Y
Michigan State

fi University I

 

 

 

OCCURRENCE OF‘A BIPTER PRINCIPLE IN CARROTS

BY
Arleigh Russell Dodson

AN ABSTRACT

Submitted to the College of Science and Arts
Huchigan State University of.Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE

Department of Chemistry

1957

Approved C ICD’MJ

Arleigh Russell Dodson

Carrots frequently develop a bitter flavor in storage which has
become a serious problem in the canning industry. The purpose of
this investigation was to isolate and identify the compound, or com-
pounds, responsible for bitterness.

A bitter principle of carrots was detected qualitatively by
paper partition chromatography.

A.crystalline, bitter compound, which melts at 77°C. and fluor-
esces in ultraviolet light, was isolated from bitter carrots. The
empirical formula was established as 01431505. Qualitative chemical
analyses indicated the presence of a free phenolic hydroxyl group
which could be methylated with diasomethane, an alkoxyl group, and
an ester linkage. The presence of one methoxyl group was substanti-

ated by quantitative alkoxyl determination. The infrared spectrum

of the bitter compound suggests that the molecule contains a conjugate-

chelate carbonyl; while the ultraviolet spectrwm indicates ortho,

para-substitution on the benzene ring containing the ester carbonyl.

OCCURRENCE OF A BITTER PRINCIPLE IN CARROTS

BY
Arleigh Russell Dodson

A THESIS

Submitted to the College of Science and Arts
Nfichigan State University of Agriculture and
Applied Science in partial fulfillment of
the requirements for the degree of

MASTER OF SCIENCE

Department of Chemistry

1957

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INTRODUCTION . .

HI S TORI CAL O O O O O O 0
EXP ERIJVIENm O O O O O 0
Part 1. Detection .
Part II. Isolation

RESULTS AND DISCUSSION . . .

SU'dJULhY e e

BIBLIOGRAPHY . .

TAbLE OF CONTENTS
and I denti fi ca ti on

C"

10

In

21

23

TABLE

II.

III.

LIST OF TABLES
PAGE
Rf values of the Acetone Extract 0f Bitter Carrots . . . . v

The Infrared Carbonyl Stretching Frequency

OfSeveraICOmpounds.o..............oo1’:

Ultraviolet Absorption Spectra Maxims and

Specific Extinction Coefficients . . . . , , , . . . . . 15

ACKNOWLEDGEMENTS

The author wishes to express his sincere thanks to Messrs. C. D.
Ball, H. M. Sell, and H. N. Fukui for their interest and guidance
throughout the course of this work. Grateful acknowledgement is also
due Mrs. Jean Lagowski and Mrs. Narion Dodson for their assistance

in the preparation of the manuscript.

I N TdODU C TI 0N

INTRODUCTION

Bitterness in carrots is a serious problem in some of our vege—
table-producing states and is annually causing a considerable loss to
the industry. It is hoped that the development of a hybrid will lead
to a variety of consistent quality and uniformity in size, color, and
flavor. At present, size, color, and flavor are serious problems of
the carrot industry. -

Recently a flavor has deve10ped, which appears to be associated
with the storage of carrots prior to processing. It has been esti-
mated that ten percent of the annual carrot crop is lost because of
this off-flavor which has been described as "bitter,” ”quinine-like,"
"soapy bitterness," ”alum—like,” and "spicy and bitter" (1).

Carrots do not have the characteristic, bitter flavor when har-
vested, but the flavor develops in common storage at 40-45°F. or in
cold storage at 32°F. Carrots are the only common, commercial vege-
table which develops bitterness in storage. Other commercial vege-
tables may develop off-flavors, but none of these has been character-
ized as bitter. Bitterness in carrots is a serious storage problem
and primarily concerns the processing industry.

To obtain a better understanding of the factors involved in the
development and control of bitter flavors in carrots, the isolation
and identification of the compound, or compounds, responsible for the

bitter flavor of carrots have been undertaken.

HISTORICAL

HISTORI CAL

There are few reports in the literature concerning the off-
flavors of carrots. Yamaguchi, Howard, and McNelly (1) compared
bitter and non-bitter carrots and noted no great differences in total
sugars, starch, protein, calcium, iron, phosphorus, vitamin C, vita-

min B vitamin Bz, niacin, orlfi? ocarotene; however, bitter carrots

1.
showed a much lower level of 0( ~carotene than non-bitter carrots.
These observations led to the postulation that bitterness may be
caused by metabolic products of the carotenoids; this has not been
confirmed, and no further work has been reported. Newcombe and
Alderman (2) found that carrots grown in muck soils developed a
rancid taste more readily in storage than carrots from upland soils.
"Aster yellows," a virus disease which may infect carrots, causes an
astringent off-flavor (3), but an organoleptic panel can distinguish
easily bitter carrots from carrots infected with the virus (1). At-
kin and Sayre(4,5) described the bitter flavor of carrots and some

of the probable causative factors on the basis of work carried out
during the years 1953 and 1954. However, the growing seasons in
these two years were quite different, and this work can be considered
only as preliminary. The years 1955 and 1956 were very poor growing
seasons in New York, causing Atkin and Sayre to abandon their re-
search (5); the carrots were of poor quality and could not survive a
storage experiment.

Although a bitter compound had not been isolated from the root

of the carrot, Pictet and Court (6) have isolated and identified two
alkaloids, pyrrolidine and daucine, which are present in carrot tops.

Gizycki and Hermann (7), while repeating the work of Pictet and
Court, isolated a compound thought to be a bitter glycoside but which
they were unable to characterize. Reeb (8) isolated a bitter glyco-
side from carrot seeds. Sorm, Zaoral, Arient, Pliva, and Herout (9)
have identified carotol, 0‘ -pinene,/8-pinene, p—cymene, carvone,
geranyl acetate,F -cary0phllene, bergamotene, bisabolene, other
diterpenic hydrocarbons, and daucol in the volatile oil of carrots.
Most of these terpenes have a bitter flavor.

Two empirical methods have been develOped for measuring the
bitterness of carrots, but in neither case has the compound been
isolated or identified. Phillips (10) blended a carrot sample with
acetone (1 m1./g.) for five to ten minutes. The acetone was decanted
and washed with 100 m1. portions of Skellysolve '5"1 until the
Skellysolve layer was colorless; usually three or four portions of
Skellysolve were sufficient. The solvent extracts were combined,
concentrated to 25-40 ml. by evaporation, and chromatographed on a
column of magnesium oxidesCelite (2:1 by weight). .After developing
the column with 500 m1. of Skellysolve «a», the top 3 to 6 mm. of
adsorbent were removed and eluted with spectrograde methanol.2 The
eluate was diluted quantitatively to 50 ml. and its ultraviolet

spectrum determined with a Beckman Spectrophotometer Model DU using

 

1 Skellysolve “B" purchased from Skelly Oil bompany, Chicago,
Illinois.

2 Methanol (Spectro Grade) 8 467 purchased from Listillation
Products Industries, Eastman Organic Chemicals Department, Rochester
3 . 5061/" York.

one centimeter cells and spectrograde methanol as a compensating sol~
vent. Readings were taken at 248 m/x, 268 myu, and 290 mfg. These
data were plotted (wave length (m/A) versus percentage transmittance),
and readings which exhibited a maximum absorption at 268 mt; indi-
cated the bitter substance to be present. The concentration of the
latter compound could be estimated by the length of the vertical

line drawn from the point at 2681m/i to the straight line connecting
the points at 248 ml; and 290 myi.

Sondheimer, Phillips, and Atkin (11) have described also a
quantitative method for determination of bitterness based upon the
characteristic ultraviolet absorption spectrum of bitter carrot
extracts which eliminates the time consuming chromatographic step
of the Phillips method. Thus, carrots were blended for five minutes
to a workable consistency, and a 5 g. sample was weighed into a 60 ml.
ground-glass stoppered bottle containing 40 ml. of spectrograde
Skellysolve "B"1 or spectrograde cyclohexane.2 The bottle was shaken,
the supernatant liquid decanted, and readings were taken at 290 mfi,
265 m/s, and 240 m/u with a Beckman SpectrOphotometer Model DU or
DK2 using one centimeter cells. The spectrophotometric data were

expressed as "height of the 265 m/ipeak" and appear to have been

 

’1 Prepared by the method of H. H. Graff, Purification of Solvents
for Absorption Spectroscopy, Anal. Chem., lg, 556 (1944).

2 Cyclohexane (Spectro Grade) S 702 purchased from Distillation

Products Industries, Eastman Organic Chemicals,
Rochester 3, New York.

calculated by the formula:

I

[A 265 min -(A 290 y + A 240 "1110] ml. solvent

 

7? T

g. sample
where A represents absorbance. Excellent correlation was found be-
tween "height of the 265 mil peak" and the actual bitterness of

carrots as judged by an organoleptic panel.

EXPl-h I MEN TAL

EXPLBIMhNTAL

The experimental work consisted of the deveIOpment of a new
method for detection of the bitter principle and the isolation and
characterization of this principle.

All solvents were C.P. solvents unless otherwise noted. Melting
points were determined on a Fisher-Johns block and were not corrected.

PAhT I. DETECTION

A rapid, qualitative method for the detection of the bitter
principle was developed using paper partition chromatography (12).
Bitter carrots were extracted wdth acetone according to Phillips'
procedure (1C) and the acetone extracts applied to Whatmanlfil filter
paper (2.5 x 25 cm.). All chromatograms were deveIOped by ascending
technique and were not equilibrated. The Rf values were easily de-
tected by their bright, blue-white fluorescence in ultraviolet light.
Table 1 lists the Rf values of the acetone extract of bitter carrots
chromatographed with various solvent systems.

TAbLL 1

Rf VALUES OF THE ACETONE EXTRACT OF bITTLR CARROTS

 

 

 

Solvent Rf Values
Water 0.44
Phenol saturated with water 0.97
Acetic acid (15%) 0.74
Heptanezl-butanolzwater (29:14:57 by volume) 0.58

Ethyl acetatexammonia (25) (1.1 by volume) 0.55

10

To ascertain whether the blue-white,f1uorescing spots were
actually the compound being measured by the method of Phillips, the
spots from the chromatograms were eluted.wdth spectrograde methanol.
The ultraviolet absorption spectrum of the methanol eluate and the
spectrum of the methanol eluate of the Phillips method were identical.
The Skellysolve "B" eluate of the blue-white,fluorescing spot gave
an ultraviolet absorption spectrum identical with the spastrum of
the Skellysolve "B" extract obtained by the procedure of Sondheimer,
32. 213 Therefore, paper partition chromatography and/er ultraviolet
absorption spectra were used for the subsequent isolation and
identification work.

PART II. lSoLALlUN AND IDLNTIFICATICN

Fourteen bushels of bitter carrots from the 1954 carrot crop
were dried in a forced-draft oven for three hours at 60°C. and
ground in a Wiley mill to pass a 2 mm. sieve. Twenty pounds of the
ground material was extracted in a large Soxhlet unit with acetone
for eight hours. The acetone solution was concentrated under re-
duced pressure (water aspirator) until crystals began to separate
from the solution. The colorless crystals were collected by filtra-
tion; concentration was continued to a tarry mass. Further attempts
to isolate additional crystalline material from the tarry mass failed
so the residue was discarded. One hundred milligrams of crystalline
material was obtained which possessed the characteristic flavor of
bitter carrots and which fluoresced brightly with a blue-white glow
in ultraviolet light. Recrystallization from.aqueous methanol gave

colorless platelets, m. p. 77°C. 1h, compound was dried over phos-

11
phorus pentoxide in 13322 at 25°C. The crystalline bitter compound
had the same Rf value in each of the solvent systems listed in
Table I as the acetone extract of bitter carrots prepared according
to Phillips' procedure (10) or the Skellysolve ”B" extract obtained
by the method of Sondheimer, :3 21' (11).

In 1956, using carrots from the 1955 crop and the same isolation
procedure, an additional two hundred milligrams of the crystalline,
bitter compound was obtained. No bitter carrots were available in
1956 because of the poor growing season.

A sample of the bitter compound was fused with sodium and sub-
jected to elemental analysis; halogens, nitrogen, and sulfur were
absent (13). A nitrogen analysis of 0.00% by Dumas' procedure
further substantiated the elemental anslysisl. The results of

qualitative tests (14) on the bitter compound are summarized below.

 

 

Test Result Conclusion
Molisch's Colorless solution No carbohydrate present
Millon's Red solution Aromatic ether or phenol
with unsubstituted ortho-
position

ldebermann's Green solution Aromatic ether or phenol
with unsubstituted para-
position

Azobenzenephenyl- Orange solution No aldehyde or ketone

hydrazine sulfonic present

acid

Sodium cobalti- Yellow solution Phenolic hydroxyl with

nitrite unsubstituted ortho-
position

Starch-iodide Colorless solution No acid present

I The microanalyses were performed by T. L. Rebstock, Department
of Agricultural Chemistry, Michigan State University, East Lansing,

Nil Chi gun.

12

Quantitative analysis showed:1

Carbon 64.03% hydrogen 5.87%
63.84% 5.88%:
Average 63.94% Average 5.88%

These data indicate that the bitter compound contains a large per-
centage of oxygen. Huffman Microanalytical Laboratories, Wheatridge,
Colorado found the molecular weight of the bitter compound to be

268 (Rest camphor method).

The percentage of alkoxyl in the bitter compound was determined
by the volumetric procedure of Vieboch and Brecher (15). The alkoxyl
group was cleaved with hydriodic acid, and the resulting alkyl iodide
(methyl or ethyl) was oxidized by bromine to iodic acid. Treatment
of the iodic acid with excess potassium iodide in acid solution gave

iodine, which was titrated with sodium thiosulfate.

 

 

Weight, VOlume (0.0200 N Blank, Methoxyl,
__mg;_ NiZSZQfi), mlf- m1. %
5.055 7.58 0.15 15.22
5.030 6.73 0.15 13.53
4.534 6.69 0.15 14.92

To determine if further methylation were possible, the bitter
compound was treated with diazomethane (16). Sodium hydroxide was
added to 5 g. nitrosomethylurea, and the evolved diazomethane was col-
lected in peroxide-free ether. The ethereal solution of the disso-
methane was added to 0.2786 g. of the bitter compound dissolved in
10 m1. of methanol. After keeping the reaction mixture at 0°C. for
-——--T—Th;—Eizroanalyses were performed by T. L. Rebstock, Department

Of Agricultural Chemistry, Micnigan State University, East Lansing,
Michigan.

13

six hours and at 25°C. for an additional 12 heurs, fine white needles

(0.1666 g.) separated. Recrystallization from methanol, followed by

drying over phosphorus pentoxide in vacuo at 25°C., gave a compound

which melted at 127-8°C.

The findings of the qualitative and quantitative tests of the

methyl derivative are summarized below.

 

Test Results
Liebermann's Yellow solution
Sodium cobalti- Pink solution
nitrite

Ferric chloride (aq.) Yellow solution
Starch-iodide Colorless solution

Hydroxamic acid Violet-red solution

Quantitative analysilsl
Carbon 64.86%
65.25%

Average 65.06%

Alkoxyl determinations

 

Sample, Volume (0.0102 a
tug. NHZSLOS), Ville
5.707 31.31
5.677 31.43

 

Conclusion

 

Aromatic ether or phenol
with unsubstituted para-
position

No phenolic hydroxyl with
unsubstituted ortho-
position

No phenolic hyoroxyl

ho acid

Ester or lactone

Hydrogen 6.08%
6.35%‘

Average 6.22%

Blank, Methoxyl,
N]. e 0/3
0.39 28.5
0.39 28.8

I The micrcanalyses were performed by T. L. Rebstock, Department
of Agricultural Chemistry, Michigan State University, East Lansing,

M1. Chi. gan.

14

The bitter compound, the methyl derivative, and several model
compounds were subjected to infrared spectral analysis. Infrared
spectra were determined using chloroform solutions of the compounds,
sodium chloride solution cells (CL5 mm.), and a Perkin-Elmer Model
21 Spectrophotometer. Special attention was directed to the carbonyl
stretching frequency range of the infrared spectra, since the presence
of an ester or lactone was indicated by the qualitative tests. The
stretching frequencies associated with the carbonyl group in the
bitter compound, methylated derivative, and several model compounds
are listed in Table II.

TAbLE 11

THE IhffiARtD CARBOhYL STEETCdING FREQUERCY OF SEVERAL COMPOUNDS

 

Compound X}: cm:'
Bitter compound 6.00 1667
Methylated derivative 5.85 _ 1709
Methyl 2-hydroxybenzoate 5.95 1681
Methyl 2-methoxybenzoate 5.80 1724
'p-Methoxyphenyl 2-hydroxybenzoate 5.90 1695
prethoxyphenyl 2-hydroxybenzoate 5.75 1739

 

The ultraviolet absorption spectra of ethanolic (95%) solutions
of the bitter compound, the methyl derivative, and methyl 2-hydroxy-
4-methoxybenzoate were determined in one centimeter cells using a
Beckman SpectrOphotometer Model DK2. Table 111 gives the wave
lengths at which maximum absorption occurs and the specific extinction

coefficients (concentration in g./l.) for the B and C bands of these

three compounds.

TABLE III

15

ULTRAVIOLET ABSORPTION SPECTRA MAXIMA AND SPECIFIC EXTINCTION COEFFICIENTS

 

 

 

B band C band
Compound max, max,
all .Is m,. .2;
hitter compound 266 72.92 507 29.34
Methyl derivative 262 69.41 297 32.21
Methyl 2-hydroxy-4—methoxybenzoate 260 --~- 297 —---

 

The ultraviolet spectrum of the bitter compound determined in

spectrograde Skellysolve "B" exhibited maxima at 265 m}; and 300 mil;

ndnima occured at 240 m/A and 278 mfg.

RESL LTS N D DI SCUSSI 0N

RESULTS AND DISCUSSION

This study was undertaken to isolate and identify the compound,
or compounds, responsible for the bitter flavor of carrots; therefore,
it was necessary to establish that the compound isolated was actually
the bitter substance. Sondheimer, gt :1. reported that the Skellysolve
"B” extract of bitter carrots showed maximum absorption at 265 mt;
while non-bitter carrots did not absorb in this region. Paper
partition chromatography of the bitter carrot extracts gave a fluores-
cent spot with a characteristic Rf value; this spot did not appear
during chrematography of non-bitter carrot extracts. Therefore, it
was concluded that a compound exhibiting maximum absorption at 265 ml;
in Skellysolve "B” and giving a fluorescent spot with a characteristic
Rf value upon paper chromatography was either the compound responsible
for the bitterness in carrots or an "index" compound present in pre-
portion to the bitter principle.

A fluorescent, crystalline, bitter compound was isolated. A
Skellysolve “B" solution of this compound showed maximum absorption
at 265 ml; and gave fluorescent spots at Rf values that are in
agreement with those of Dodson, Fukui, Ball, Carolus, and Sell, hence
the compound isolated is either the bitter principle or an "index“
compound.

The carbon and hydrogen analyses suggest an empirical formula
C1431505 for the bitter compound. The molecular weight, 263, cal-

culated from the empirical formula agrees vdth the experimentally

determined value, 268. Attempts to determine the molecular weight of

18
the methyl derivative by the East method using camphor or exaltone as
solvents failed.1 A molecular weight of 277 has been assumed for the
methyl derivative on the basis of the empirical formula suggested by
carbon and hydrogen analyses.

On the basis of a molecular weight of 277 for the methyl deriva-
tive and the observed molecular weight of 268 for the bitter compound,
the former compound contains 28.6% methoxyl while the latter compound
contains 14.6% methoxyl. An assumption was made that the alkoxyl
determination was for methoxyl, not ethoxyl; this was necessary be-
cause the alkoxyl determination of the bitter compound gave values of
14.56% for methoxyl or 21.3% for ethoxyl. These percentages correspond
to 1.26 methoxyl or 1.27 ethoxyl per molecule. If the postulate is
correct, then the methoxyl content of the bitter compound and its
methyl derivative provides further evidence that one hydroxyl group
of the bitter compound was methylated; thus the bitter compound con-
tains one methoxyl group while two methoxyl groups are present in the
methyl derivative.

Qualitative tests indicated the presence of an ester or lactone
in the bitter compound and its methyl derivative; therefore, the
regions of the infrared spectra of these compounds associated with
the carbonyl group were examined. A four or five-membered lactone
carbonyl absorbs at wave numbers greater than 1770 cm? (5.65/L) (17),
but the bitter compound or its methyl derivative absorb beyond this
region. Thus the bitter compound and its derivative must be either

esters or six-membered lactones.

 

IT Schwarzkopf Microanalytical Laboratory, 56-19 37th Avenue,
Woodside 77, New York.

19

An unconjugated carboxylic ester or six-membered lactone carbonyl
absorbs at 1739 on?! (5.81/4) (17). Enoiizod’B -diketones or w
phenolic hydroxyl groups exhibit the bathochromic shift of the car-
bonyl stretching frequency expected from conjugated chelate systems,
g;g., the carbonyl absorption appears near 1667 cm! (6.09/4). The
infrared spectrum of the bitter compound shows absorption at 1667 cm?
(6.00/4), therefore it may be concluded that the carbonyl group is
located 33:22 to a phenolic hydroxyl group. Methylation of the
phenolic hydroxyl shifts the carbonyl stretching frequency to 1709 oml'
(5.5a/4) suggesting that the carbonyl group is conjugated with a
benzene ring.

If the conjugate-chelate carbonyl is in a six-membered lactone,
the lactone ring must be attached to the paggfposition of the benzene
ring carrying the carboxyl carbonyl or to a group on the 6-position
of the benzene ring. In either case, seven carbons are accounted for;
the remaining eight carbons must be attached to the 6-position of the
benzene ring. Positive Millon and Liebermann tests preclude placement
of sutstituents in the 3 and 5-positions of the benzene ring. Attach-
ment of six carbons in the 6-position is improbable on the basis of
steric factors, hence the possibility of a six-membered lactone has
been eliminated, and the bitter compound must contain an ester
linkage.

Substituted benzoic acids exhibit three absorption bands in the
ultraviolet which have been designated as the A, B, and C bands (16).
The frequency of absorption of A is independent of, B is very depen-
dent upon, and C is somewhat dependent upon the nature and position

of the substituent groups. Since the bitter compound has maxima

 

 

20
corresponding to the B and C bands at 266 ml; and 307 mfg, respective-
ly, in 95% ethanol, and since an ortho hydroxyl group was indicated by
the infrared spectrum, it may be concluded that the bitter compound

has orthp,gpara-substitution on the benzoic acid portion of the molecule.

 

On the basis of elemental analysis and spectral data, the group in the
éggfifpositicn is either an ether or a free hydroxyl group, since an
aliphatic group would cause the least bathochromic shift of the B
band. Methylation of the bitter compound introduced one methoxyl
group ortho to the ester carbonyl, therefore a free hydroxyl group in
the pgzzfposition appears unlikely. 0n the basis of these data it may
be concluded that the Berg-position contains an ether group.

The Bazagpcsition could contain either an aryl or an alkyl other
group; if it is an aryl ether, then the compound is a methyl ester.
If the compound is an aryl ester, then the parafposition of the ben-
zene ring carries a methoxyl group. Either of these partial structures
leaves three hydrogens and one oxygen unassigned. Another possibility
exists, i.e. the ester and the ether may be aliphatic with one being
a methyl group. The possibilities are summarized by the following

partial structural formula:

0 H

R or R' CH3

R O \—/ g-o-R'

R or R. CEHSO

hydrolysis of the ester and identification of the hydrolysis
products should lead to complete elucidation of the structural
formula. At ‘resent the uantit\ of the bitter Wrinci-le which is
p a q J r P

available has restricted further work.

S L‘ Iv’lx'lA RY

SUIr’J‘i‘A RY

Paper partition chromatography was used as a qualitative method
for the detection of a bitter principle of carrots.

A crystalline, bitter compound, m. p. 77°C., was isolated from
carrots and has been assigned the empirical formula Clgdlsos. Quali-
tative chemical analysis indicated the presence of a free phenolic
hydroxyl group which could be methylated with diazomethane, an alkoxyl
group, and an ester linkage; while a quantitative alkoxyl determination
showed that the molecule contains one methoxyl group. Spectral
analyses suggested the presence of a conjugated-chelate carbonyl and
.githg,lp=£=,-substitution on the benzene ring carrying the ester

carbonyl.

l: I £;IJJ. u} MP: iY

1.

2.

3.

4.

6.

10.

ll.

13.

biBLiCGhAPHY

M. Yamaguchi, F. D. Howard, and L. B. Mcfielly, Observations on
Bitterness of California Grown Carrots, Plant Lisease Reptr. .ig,
502 (1955).

B. Newcombe and L. C. Alderman, Factors Influencing Quality of
Eehydrated Carrots, Mich. Agr. hxpt. Sta. Quart. Bull. 32,
5 (1944).

G. E. R. Hervey, W. b. Robinson, and h. T. Schroeder, Carrot
Yelloms Affects Flavor of Processed Produce, Canning Trade 70,
8 (1943). "‘

J. b. Atkin and C. B. Sayre, hhat Makes bitter Carrots 'bitter"?,
Farm Research.gl, 15 (1955).

J. D. Atkin, Bitter Flavor in Carrots 11. Progress Report on
‘ield and Storage Experiments. N. Y. State Agricultural Experiment
Station, Hull. No. 774, March 1956.

A. Pictet and G. Court, Uber einige neue Pflanzenalkaloide, Ber.
deut. chem. Ges.‘ég, 3771 (1907).

F. v. Gizycki and H. Hermanns, Untersuchung des Krautes von Daucus
Carcta L., Arch. Pharm. 284, 8 (1951).

E. Reeb, Daucusin a Bitter Glucoside of the Seeds of Daucus Carota
L., J. pharm. Alsace Lorraine £9, 13 (1923). C.A. 11, 2346 (1923).

F. Sorm, M. Zaoral, J. Arient, J. Pliva, and V. Herout, 0n Terpenes
XXIII. Composition of Oil of Carrot, Collection Czechoslov. Chem.
Commun. lg, 47 (1951).

h. F. Phillips, Beach-Nut Packing Co., N. Y., Private Communication,
(1954).

E. Sondheimer, h. F. Phillips, and J. L. Atkin, sitter Flavor in
Carrots I. A Tentative Spectrophotometric Method for the Estimation
of Bitterness, hood Research 39, 659 (1955).

A. R. Dodson, H. N. Fukui, C. D. Ball, B. L. Carolus, and d. M.
Sell, Occurrence of a Bitter Principle in Carrots, science 124,
9s4 (1956).

R. L. Shriner and R. C. Fuson, The Systematic Identification of
Organic Compounds, John Wiley and Sons, Inc., New York, 3rd
edition, (1948).

17.

18.

25

F. Feigl, Spot Tests Volume II Organic Applications, Blsevier
Publishing Company, New York, (1954).

A. Steyermark, Quantitative Organic Microanalysis, The Blakiston
Company, Nev York, (1951), pp 236-243.

A. Schonberg, Action of Diazomethane on fiydroxy-compounds and
of Diazomethane Derivatives on Phenanthraquinone, J. Chem. Soc,
(1946), 746.

R. S. Rasmussen and R. R. Brattain, Infrared Spectra of some
Carboxylic Acid Derivatives, J. Am. Chem. Soc. 11, 1073 (1949).

C. M. Moser and A. J. Kohlenberg, The Ultraviolet Absorption
Spectra of Some Benzoic Acids with Electron-Repelling Substituents,
J. Chem. soc. (1951) 804.

CHEMISTRY LIBRA
BY
Date Due

 

 

19314110

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Denna-293

 

 

T gaging TRY LIBRARY C _ 2

Dodson,
Occurrence of a bitter principle
in carrots.

CHEMlSTRY manna?
The 81 e

c 2
Dodson, '

Occurrence of a bitter principle
in carroti.

 

 

enamel_xmesm

 

 

 

 

 

 

 

ER

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