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Factors influencing methyl ketone formation in milk fatLangler, James Edward 02 December 1963 (has links)
Recent studies have shown that when milk fat is heated, a
homologous series containing the n-alkyl members of methyl ketones
with odd numbers of carbon in their chains are produced (48; 44; 38;
and 3). The same series of compounds also is found in evaporated
and dried whole milk and in these products the concentration increases
during storage (70 and 46). It is believed by some investigators
that the methyl ketones play an important role in flavor deterioration
of milk fat and in the aforementioned concentrated products.
At the present time, however, there is disagreement on the factors
influencing methyl ketone production; some workers relate their
formation to autoxidation (25), while there are others who report
that heat and water are essential in the reaction (48; 38 and 3).
Finally, a recent report indicates that anhydrous milk fat will give
rise to methyl ketones when heated in the absence of oxygen (44).
The purpose of this investigation was to study the effect of
various factors on the qualitative and quantitative composition of
methyl ketones in heat treated milk fat. It is anticipated that the
resulting information will contribute to a more thorough understanding
of the reactions leading to ketone production in the fat; hence, to
development of suitable processing measures for prevention of this
type of deterioration in dairy products.
Milk fat was prepared from raw cream two days after milking.
It was washed free from phospholipids, centrifuged at 30,000
x G for 20 minutes and degassed at two to five microns pressure
for one hour. The fat was then heat treated in sealed vials at various
temperatures and time periods under controlled conditions.
The samples were quantitatively analyzed for methyl ketones by
direct conversion of the ketones to 2, 4-dinitrophenylhydrazine
(DNP) derivatives in the intact fat sample. The derivatives were
isolated from the fat, separated and identified by a combination of
column and paper chromatographic methods and by their absorption
spectra.
Methyl ketone formation in heated milk fat was shown to be
non-oxidative. A plateau in ketone production was approached in
the 120°C to 140°C range when the time of heat treatment was 30
minutes. Added water enhanced total methyl ketone production at
140°C but not at 200°C. Air did not hinder ketone production. Maximum ketone production (1.733 mM/kg fat) was noted after three
hours of heat treatment at two to five microns pressure, and 140°C.
Milk fat centrifuged at 30,000 x G for 20 minutes and degassed at two
to five microns pressure for one hour was found to contain 0.27%
water. This quantity of water is sufficient for hydrolysis of β-ketoesters
assuming them as the precursors of the methyl ketones.
Conventional methods of preparing "anhydrous" milk fat were not
adequate for removal of trace amounts of water. When milk fat was
dried over calcium hydride (35) prior to heat treatment, total ketone
formation was significantly reduced indicating that water is a limiting
factor in ketone formation.
A homologus series of n-alkyl methyl ketones (C₃, C₅, C₇,
C₉, C₁₁, C₁₃, C₁₅) was isolated from heat treated samples. The
ketones produced in large amounts were the C₃, C₇, and C₁₅.
When the heat treatment was for three hours or longer the C₄ ketone
was detected and composed approximately 11% of the total. The possible
origin of the C₄, ketone is discussed. The reaction of intact
fat with DNP-hydrazine and the subsequent isolation and identification
of methyl ketones were quantitatively evaluated. / Graduation date: 1964
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A critical evaluation of the accuracy of the gradient balance method for specific gravity determination in milkGhlander, Abdel Moneim, 1935- January 1963 (has links)
No description available.
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A simplified technique for milk protein determination by the dye-binding methodKuboyama, Morio 16 May 1961 (has links)
Graduation date: 1961
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Maximum density of milkMedved, Thomas Milton. January 1956 (has links)
Call number: LD2668 .T4 1956 M43 / Master of Science
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Identification of some compounds contributing to the stale flavor defect of sterilized concentrated milkArnold, Roy Gary 27 July 1965 (has links)
Stale flavor development has been recognized as a defect of
stored dry milk powders for several years. Recently, stale flavor
development has been found to occur upon storage of sterilized concentrated
milk, and is recognized as the principal limiting factor to
commercial utilization of this process (Seibert, 1963).
Some attempts have been made to identify the volatile flavor
components of sterilized concentrated milk (Patel et al, 1963;
Bingham, 1964). The flavor components responsible for the stale
flavor defect as it occurs in sterilized concentrated milk have not
been identified, however.
The purpose of this work was to identify the compounds responsible
for the stale flavor defect of sterilized concentrated milk.
It was felt that this information was essential to an understanding
of the staling phenomenon, which in turn might eventually lead to
correction of the defect.
Commercial samples of sterilized concentrated milk were obtained.
Stale flavor development was hastened in some of the samples
by storing them at 21°C. Subjective flavor panel evaluation of stored
and fresh samples revealed significant differences between the two.
Gas chromatographic analysis of the volatile head space components
by the procedure described by Morgan and Day (1965) revealed
only minor differences between the fresh and stale samples.
It was reasoned, therefore, that the compounds responsible for the
stale flavor defect were primarily of a less volatile nature,
A technique for isolating the higher-boiling flavor components
was developed. This technique consisted of lyophilization of the
sterile concentrated milk, uniform wetting of the lyophilized milk
with water to 10% moisture, solvent extraction of the fat and flavor
components from the moistened milk powder, and reducedtemperature,
reduced-pressure steam distillation of the flavor components
from the extracted fat. The resulting flavor extract was
studied by gas chromatography in conjunction with mass spectrometry
A base-treated pre-column was used in front of the regular gas
chromatography column to remove fatty acid peaks from the chromatograms.
A technique, which consisted of repeatedly trapping (from
several successive chromatograms) particular regions of the effluent
from a non-polar column onto a short section of packed column and
re-chromatographing the trapped components on a polar column, was developed to build up the concentration of flavor components and to
improve the separation of components for mass spectral analysis.
The following compounds were positively identified in the flavor
extract from stale sterile concentrated milk: 2-heptanone, 2-nonan.one,
2-undecanone, 2-tridecanone, benzaldehyde, napthalene, a dichlorobenzene,
L-decalactone, benzothiazole, and o-aminoacetophenone.
Acetophenone was tentatively identified. Of these compounds, 2-
heptanone and the dichlorobenzene were positively identified in the
extract from fresh sterile concentrated milk, and L-decalactone
was thought to be present.
The ketones and L-decalactone undoubtedly make some contribution
to the stale flavor defect (USDA, 1964). The identification
of o-aminoacetophenone in stale sterilized concentrated milk supplements
its identification in stale nonfat dry milk powder (Parks,
Schwartz and Keeney, 1965), and further implicates it as an important
compound in the stale flavor defect. This compound possesses
a characteristic "grape-like" odor. Benzothiazole has not previously
been identified in milk products. It possesses a characteristic
"rubber-like" odor. Its possible significance in the stale flavor
defect will require further study. / Graduation date: 1966
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Gas chromatographic analysis of some lower molecular weight amines in milk and the relationship of these amines to feed [sic] flavorsMehta, Rajen Sumatilal January 2010 (has links)
Digitized by Kansas Correctional Industries
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Phenolphthalein phosphate as a reagent for alkaline phosphatase estimation in milkDe souza, Marciano José, 1936- January 1968 (has links)
No description available.
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Comparison of tests for coliform bacteria in raw milkMoura Fé, José de Anchieta, 1936- January 1969 (has links)
No description available.
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A study of the accuracy of testing milk for butterfat using samples with and without chemical preservativesTaylor, Ralph Ronald, 1932- January 1961 (has links)
No description available.
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Heat induced compounds in milkScanlan, Richard A., 1937- 02 November 1967 (has links)
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 spectrophotometry
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 treatment):
the C₃, ₄, ₅, ₇, ₈, ₉, ₁₀, ₁₁, ₁₃ n-methyl ketones, the C₈, ₁₀, ₁₂
delta-lactones, acetaldehyde, hexanal, benzaldehyde, furfural,
phenylactaldehyde, vanillin, the C₆, ₈, ₁₀ n-alkanoic acids, ethanol,
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:
C₃, ₄, ₅, ₇, ₉ n-methyl ketones, C₁₀, ₁₂ delta-lactones, hexanal,
benzaldehyde, C₆, ₈, ₁₀ 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 38 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 subthreshold
level to above the average flavor threshold. It is suggested
that diacetyl contributes to the "rich", "heated" note in the flavor of
heated milk. / Graduation date: 1968
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