Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 183-193).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1961. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 53-56).

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [107]-114).

Thesis (M.S.)--University of Wisconsin--Madison. / eContent provider-neutral record in process. Description based on print version record. Bibliography: l. 35-37.

Thesis (M.S.)--University of Wisconsin--Madison, 1962. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaf 84).

Thesis (M.S.)--University of Wisconsin--Madison, 1961. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 30-32).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1961. / Vita. Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 125-129).

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

Deterioration of the flavor of sterilized concentrated milk (SCM) is recognized as the principal limiting factor to commercial acceptance of this product. Although a number of volatile compounds have been identified in SCM, quantitative information on these compounds is lacking. It is therefore difficult to ascertain the significance of these compounds. The purpose of this investigation was to determine the identity of additional flavor compounds of stored SCM and to determine the concentrations of the major flavor compounds. Vacuum steam distillation was utilized to recover volatile flavor compounds from samples of SCM. The distillates were extracted with ethyl ether, and components of the ethereal flavor concentrates were separated by gas-liquid chromatography (GLC). Major components whose identity was unknown were collected from the GLC effluent, and were analyzed by capillary column GLC and mass spectrometry. A system for transferring trapped components directly onto a capillary GLC column was developed. 2-Furfural, which had not previously been identified in SCM, and 2-furfurol, which had not been identified as a component of any stored milk product, were identified in stored SCM. Commercial samples of SCM were placed in controlled storage, and subjected to flavor panel evaluation and a number of quantitative determinations at selected intervals of storage. The concentration of the odd-numbered n-methyl ketones, C₃-C₁₁, and of o-aminoacetophenone were determined by measuring the absorbance of their respective 2, 4-dinitrophenylhydrazone derivatives. The concentration of 2-furfurol was determined by a gas entrainment, on-column trapping GLC technique. Acid degree values were obtained by titration of SCM milk fat. Hydroxymethylfurfural (HMF) values were determined by measuring the absorbance of the HMF thiobarbituric acid reaction product. The methyl ketones and o-aminoacetophenone were found to exceed their flavor threshold concentrations after 13 weeks storage of SCM at 27°C. The concentration of 2-furfurol exceeded its threshold concentration after 26 weeks at 27°C, but not after 13 weeks. Acid degree values increased slowly, but did not reach significant levels through 26 weeks at 27°C. Hydroxymethylfurfural values increased slowly through the first 13 weeks at 27°C storage, followed by a marked increase during the second 13 weeks. Heat degradation of thiamine was studied as a possible source of volatile flavor compounds. Heating of thiamine solutions in phosphate buffer at pH 6.7 resulted in the production of volatile components of potential flavor significance. The identity of these components was studied by gas entrainment, on-column trapping GLC, collection of components, and capillary column GLC in conjunction with mass spectrometry. The system developed for the transfer of trapped components directly onto the capillary GLC column was utilized. Hydrogen sulfide, 2-methyl furan, 2-methyl thiophene and a compound which appeared to be a dihydro-2-methyl thiophene were identified as volatile heat degradation products of thiamine. / Graduation date: 1968