The role of beta-carotene degradations in the development of off-flavors in milk and milk products has not been established. The purpose of this investigation was to study the oxidation of beta-carotene and to identify volatile compounds arising from autoxidizing beta-carotene. Pure cyrstalline beta-carotene, mixed with Celite to accelerate oxidation, was oxidized at 50°C by molecular oxygen in two different systems. The peroxide value and loss of beta-carotene were measured after controlled oxidation periods. In one system the maximum peroxide value, 295 milliequivalents per 1,000 grams, occurred after three hours of oxidation. In the other system the maximum peroxide value, 586 milliequivalents per 1,000 grams, was observed after six hours of oxidation. Approximately 80 percent of the beta-carotene was decomposed within the first ten hours of oxidation. Volatile compounds from autoxidizing beta-carotene were collected by a cold-trap gas-entrainment technique. The collected compounds were subjected to gas-liquid chromatography and rapidscan mass spectrometry, and the following compounds were identified: n-pentane, ethyl ether, acetaldehyde, acetone, propanal, methyl vinyl ketone, toluene, isobutanal, 2-octanone and acetic acid. Compounds tentatively identified included diacetyl, 3-methyl- 2-pentanone, 4-methyl-3-pentan-2-one, 2-methylfuran, 1,3,3-trimethylcyclohexene, rnethyl formate, butanone, 2-methyl-2-heptenal, 1, 3-dimethyl-2-ethylcyclohexane, 2-ethyl-2-hexenal, 2-formyl-3, 3- dimethylcyclohexene, 1, 1, 3-trimethyl-2-n-propylcyclohexane, 2- methyl-3-nonene and 3, 5, 5-trimethyl-4-(4'-butyl-3'-en-2'-onyl) cyclohexa-1, 3-diene. A fraction possessing a strong "nutty" aroma was tentatively identified as 2-methyl-2-heptenal. The volatile compounds identified can be predicted as degradation products of beta-carotene oxidation. / Graduation date: 1967

Thesis (Ph. D.)--University of Wisconsin--Madison, 1951. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 103-115).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (M.S.)--University of Wisconsin--Madison, 1984. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 127-131).

No description available.

Typescript, etc. / Digitized by Kansas State University Libraries

Call number: LD2668 .T4 1952 G73 / Master of Science

Call number: LD2668 .T4 1961 A47

published_or_final_version / abstract / Biological Sciences / Doctoral / Doctor of Philosophy

Carrots were cooked to the just tender stage in a saucepan and in a pressure saucepan for appropriate lengths of time to make them approximately equal in tenderness as determined by a panel of judges and the Kramer Shear Press. A third lot of carrots was cooked in a pressure saucepan for approximately twice as long to represent overcooked carrots. Judges and the Hunter Color Meter indicated that the carrots cooked in the saucepan were more typically red-orange and bright and the carrots overcooked in the pressure saucepan were more yellow and dull. Pigments extracted from the carrots from the three cooking treatments were chromatographed on a magnesia column and the principle fractions, α-carotene and β-carotene, eluted. The β-carotene was rechromatographed on an alumina column to separate it into all-trans-β-carotene and neo-β-carotene B. In absolute amounts, carrots cooked in the saucepan had the highest concentration of all-trans-β-carotene and the highest total of all-trans-β-carotene, neo-β-carotene B and α-carotene, followed by those carrots cooked in the pressure saucepan for 50 seconds, with those cooked in the pressure saucepan for two minutes being lowest in both all-trans-β-carotene and total carotenes. However, when the a-carotene, the neo-pcarotene B and the all-trans-β-carotene were considered as percentages of the total, the percentage of α-carotene remained constant in the three treatments. Carrots cooked in the pressure saucepan for two minutes had a lower percentage of all-trans-β-carotene and a higher percentage of neo-β-carotene B than did carrots from the other two treatments. Thus, longer cooking in the pressure saucepan caused greater conversion of the more vivid all-trans-β-carotene to the paler cis-isomer, neo-β-carotene B. This isomerization plus loss of total pigment accounts for the differences in color of the cooked carrots from the three treatments. / Graduation date: 1964