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 46-97).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 107-111).

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).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1966. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Minimally processed fruits and vegetables are increasingly demanded by local consumers and for export purposes. However, the marketing potential of these produce is limited because of physiological ageing, biochemical changes and microbiological spoilage that lead to a short shelf life. The use of polymeric packaging films to control microbial and metabolic processes and edible coatings to control the white blush formation respectively, have shown potential in improving the quality of minimally processed carrots. In combination they may form a double barrier to gases and water vapour that could provide an interaction effect to enhance the shelf life of minimally processed carrots. The aim of the study was to determine the effects of the polymeric packaging films of different permeability and edible coatings at different levels of concentration, alone and in combination on the physiological and biochemical, microbiological, and sensory quality of minimally processed carrots. A factorial experiment of 3 polymeric packaging films x 3 levels of edible coating was conducted. The three polymeric packaging films were P-Plus®, an oriented polypropylene which were fully permeable to gases and water vapour (pi, control), semi permeable (p160) and least permeable (p90) to gases only. The semi permeable and least permeable packaging had similar water vapour permeability. The coating was Nature Seal®, a cellulose based, at 0% (control), 7.5% and 15% w/w. Carrots were minimally processed into slices, dipped in the edible coating, then packed in the polymeric films and stored for 12 days at 10°C. Four packs were analysed for each combination treatment on d4, d8 and d12, and dO was taken as reference point. With time, the head space in the semi permeable packaging (p160) showed a decrease to about 11.5-13.6% oxygen and an increase to about 7.5-9.6% carbon dioxide. The least permeable pack (p90) showed an oxygen decrease to about 9.8-7.6% and a carbon dioxide increase to about 12.3-13.5%. This change showed the creation of a modified atmosphere that will decrease the metabolic activities. As the coating concentration increased, a slight increase in carbon dioxide and a slight decrease in oxygen were recorded in the head space of the packs. This change was unexpected as the coating was supposed to be a gas barrier. Thus, this change questioned the gas permeability properties of the edible coating. The polymeric packaging and the coating interacted to give lower oxygen and higher carbon dioxide levels in the head space atmosphere. However, packaging had a more pronounced effect in the creation of the modified atmospheres than the coating. A lower white blush formation and a higher retention of chroma values was recorded on the lower surfaces of the carrot slices than on the upper surfaces (upper surfaces refer to those that were facing the packaging material, the lower surfaces was the opposite side of the upper surfaces). This showed that the relative humidity gradient was probably not the same between the surfaces. The coating effectively controlled the white discolouration and maintained higher chroma values on both surfaces of the carrot discs, but packaging did not affect the colour changes of the upper surfaces. An interaction effect was also observed between the packaging and coating showing a better control of the white blush formation of the lower surfaces of the carrot discs. Yeast and moulds did not prove to be a problem in minimally processed carrots as they were lower than 103 cfu/g carrots throughout the storage period. When the carrots were visibly spoiled, the lactic acid bacteria were over 106 cfu/g and the psychrotrophs were about 107 to 108 cfu/g. Initially, a high growth rate of psychrotrophic bacteria occurred followed by a high growth rate of the lactic acid bacteria. This showed a dynamic relationship between the two microbes. Visible rot was observed by brown discolouration, tissue softening and exudate production. The packaging controlled the microbiological growth and spoilage as compared with the coating that enhanced it. A decrease in pH from d4 to d12 corresponded to an increase in the lactic acid bacteria and visible spoilage. Combination of edible coatings and polymeric packaging films did not show any synergistic or additive effects to enhance the shelf life of minimally processed carrots despite some interactions between these two variables. This was because the polymeric packaging films primarily prevented microbiological growth and spoilage, whereas edible coatings partly controlled white blush formation. White blush formation was the most important shelf life determinant of minimally processed carrots. Research efforts should therefore be focused on overcoming this defect. / Dissertation (MSc (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted

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

No description available.

No description available.

Cryopreservation offers a viable and safe storage method for germplasm in contrast to more traditional germplasm conservation methods, but can be technically difticult and can involve the use of expensive equipment. The present study achieved the production and maintenance of callus and suspensions cultures and somatic embryos of Daucus Carota. L for use in cryopreservation experimentation. (Abbreviation abstract) / Andrew Chakane 2018