AN ABSTRACT OF THE THESIS OF Richard Anthony Scanlan for the Ph. D.

120 Pages·2011·0.95 MB·English

AN ABSTRACT OF THE THESIS OF
Richard Anthony Scanlan for the Ph. D.
(Degree)
in Food Science presented on /Yo V C tr) p^L r P- ; / f6~7
(Major) (Date)
Title: HEAT INDUCED COMPOUNDS IN MILK
Abstract approved:
Ehr. R. C. Lindsay /^
Dr. E. A. Day ~^
Milk, preheated at 82° C for 30 minutes, was heated to 146° C
for four seconds (UHT-treated) and cooled to 5 " C in a tubular heat
exchanger. Immediately after heat treatment, 20 gallons of heated
milk were vacuum distilled at 30° C in a semi-continuous, reduced
pressure glass apparatus. Twenty gallons of non-heated milk were
distilled in a similar manner to serve as a control. Continuous
liquid-liquid ethyl ether extractions were employed to recover the
compounds from the aqueous distillates.
Gas chromatography, mass spectrometry, infrared spectro-
photometry and odor confirmation were used to characterize the
compounds in the flavor concentrates. A technique for collecting
and transferring packed column gas chromatographic fractions to
capillary columns for mass spectral analysis was developed.
The following compounds were identified in UHT-treated milk
(the underlined compounds appeared to result from the heat treat-
ment): the C3, 4, 5, 7, 8, 9, 10, 11, 13 JJ-™6^1 Atones, the C ^
8> 12
delta-lactones, acetaldehyde, hexanal, benzaldehyde, furfural,
phenylactaldehyde, vanillin, the C, ._ n-alkanoic acids, ethanol,
o,0 o, 1U —
oct-1 -en-3-ol, n-heptanol, 2-butoxyethanol, diacetyl, maltol,
acetophenone, ethyl acetate, benzothiazole, toluene, naphthalene,
a dichlorobenzene, a trichlorobenzene, methyl iodide, benzonitrile
and chloroform.
The following compounds were identified in non-heated milk:
C. . _ n-methyl ketones, C _ delta-lactones, hexanal,
Q n
benzaldehyde, C^ g JQ n-alkanoic acids, ethanol, diacetyl,
ethyl acetate, methyl palmitate, diethyl phthalate, a dichlorobenzene,
a trichlorobenze and methyl iodide.
The concentration of diacetyl in UHT-treated and non-heated
milk was determined by a modified gas entrainment, on-column
trapping GLC technique. The amount of diacetyl in non-heated milk
was 3 ppb while the amount in the UHT-treated was 3 8 ppb. The
diacetyl concentration of UHT-treated milk decreased approximately
40% over 16 days storage at 4° C. The average flavor threshold for
diacetyl in milk was found to be 12 ppb. It seems therefore that the
UHT-treatment increased the diacetyl concentration from a sub-
threshold level to above the average flavor threshold. It is suggested
that diacetyl contributes to the "rich", "heated" note in the flavor of
heated milk.
Heat Induced Compounds in Milk
by
Richard Anthony Scanlan
A THESIS
submitted to
Oregon State University
in partial fulfillment of
the requirements for the
degree of
Doctor of Philosophy
June 1968
APPROVED:
■■^. r — j-^, ~^j^ ..JnTrT—^£^
Assistant Professor of Food Scienp^yand Technology
in charge of major
Professor of Food Science j^S Technology
in charge of major
Head of Department of Foo&^cience and Technology
Dean of Graduate School v
Date thesis is presented /VOV & fog ft -e T X l^^V
?
Typed by Opal Grossnicklaus for Richard Anthony Scanlan
ACKNOWLEDGMENT
I would like to express my gratitude to Drs. R. C. Lindsay
and E. A. Day, who served as co-chairmen of my doctoral com-
mittee, and generously offered suggestions and guidance during the
course of this work.
I would also like to thank the members of my graduate com-
mittee: Dr. M. W. Montgomery, Dr. F. T. Bond and Dr. D. L.
MacDonald; who contributed their time and helpful suggestions.
Thanks to Dr. L. M. Libbey for his assistance in obtaining and
interpreting the mass spectra.
The cooperation of the Cherry-Burrell Corporation, who con-
tributed the laboratory model Spiratherm for this investigation, is
greatly appreciated.
Finally, I want to express my deep appreciation to my wife,
Margaretta, for her patience and encouragement throughout the
course of my graduate career.
TABLE OF CONTENTS
INTRODUCTION 1
REVIEW OF LITERATURE 3
The Flavor of Heated JVUlk 3
Compounds Identified in Heated Milk 5
Ketones 6
Aldehydes 10
Lactones 12
Acids 15
Sulfur Compounds 1 7
Alcohols 19
Nitrogen Compounds 20
Miscellaneous Compounds 20
Nonenzymatic Browning Reactions 26
Compounds Identified in Non-Heated Milk 29
Carbonyl Compounds 29
Acids 30
Lactones 30
Alcohols, Sulfur, Nitrogen, and
Miscellaneous Compounds 30
EXPERIMENTAL 34
Heat Treatment 34
Organoleptic Evaluations 35
Recovery of Compounds 3 6
Distillation 3 6
Extraction 40
Concentration 40
Identification of Compounds 41
Gas Chromatographic Procedures 41
Gas Chromatography Combined with
Rapid-Scan Mass Spectrometry 42
Infrared Spectroscopy 51
Qualitative Determination of Diacetyl 53
Quantitative Determination of Diacetyl 55
Average Flavor Threshold Determinations for Diacetyl 59
RESULTS AND DISCUSSION 60
Organoleptic Evaluations 60
Identification of Compounds 61
TABLE OF CONTENTS (CONTINUED)
Qualitative Determination of Diacetyl 80
Quantitative Determination of Diacetyl 81
Average Flavor Threshold Determination for Diacetyl 87
Origin and Significance of Compounds 89
SUMMARY AND CONCLUSIONS 99
BIBLIOGRAPHY 101
LIST OF FIGURES
Figure Page
1. Heat treated milk score sheet. 3 7
2. Diagram of the steam distillation apparatus. 3 8
3. Top view of the sample inlet system. 49
4. The headspace entrainment assembly used for the 56
analysis of diacetyl.
5. Chromatograms of UHT-treated (A) and non-heated 62
(B) ethereal concentrates using a 20% Apiezon M
column.
6. Infrared spectra of experimental (A) and known (B) 64
decanoic acid in carbon tetrachloride.
7. Infrared spectra of experimental (A) and known (B) 65
decanoic acid in carbon disulfide.
8. Infrared spectra of experimental (A) and known (B) 66
2-undecanone in carbon tetrachloride.
9. Chromatograms of UHT-treated (A) and non-heated 72
(B) ethereal concentrates using a BDS capillary
column.
10. Chromatograms of traps 3U (A) and 3R (B) run on 78
a Carbowax 20 M capillary column.
11. Recorder response obtained with various concentra- 85
tions of diacetyl.
12. Flavor threshold curve for diacetyl in milk. 88
LIST OF TABLES
Table Page
1. Organoleptic evaluations of one and seven day old 60
UHT-treated milk.
2. Relative retention times of compounds from UHT- 63
treated and non-heated ethereal concentrates using a
20% Apiezon M column; gas chromatographs shown in
Figure 5 (Run 1).
3. Relative retention times of compounds from UHT- 66
treated ethereal concentrate using a 2.5% Carbowax
20 M column (Run 2).
4. Relative retention times and mass spectral identifica- 69
tion of compounds from UHT-treated and non-heated
ethereal concentrates using a 20% Apiezon M packed
column (Run 3).
5. Reference and experimental mass spectral data for 70
benzothiazole and trichlorobenzene.
6. Relative retention times and mass spectral identifica- 73
tions of compounds from UHT-treated and non-heated
ethereal concentrates using a BDS capillary column;
gas chromatograph shown in Figure 9 (Run 4).
7. Relative retention times and mass spectral identifica- 74
tions of compounds from UHT-treated and non-heated
ethereal concentrates using a Carbowax 20 M capillary
column (Run 5).
8. Reference and experimental mass spectral data for 75
methyl iodide.
9. Relative retention times and mass spectral identifica- 78
tions for traps 1U through 5U and traps 1R through
5R (Run 6).
10. Reference and experimental mass spectral data for 79
oct-1-en-3-ol and benzonitrile.
LIST OF TABLES (CONTINUED)
Table Page
11. Experimental and reference mass spectral data 81
for diacetyl.
12. Summary of compounds identified in UHT-treated 82
milk.
13. Summary of compounds identified in non-heated 84
milk.
14. Amount of diacetyl in non-heated, forewarmed and 86
UHT-treated milk.
15. Effect of refrigerated storage on the diacetyl content 86
of UHT-treated milk.