Graduation date: 1961

Graduation date: 1949

Graduation date: 1961

Call number: LD2668 .T4 1958 B87 / Master of Science

Large amounts of plant tissue are used in the production of many canned, frozen and dried foods. Some of this material is unsatisfactory in appearance and texture, despite careful processing from high quality raw materials. In the present study, the changes induced in soft fruits by controlled heating and freezing treatments were of prime concern. Strawberries and tomatoes were canned and frozen in 60° B sucrose syrup, stored for 3-6 months and examined by physical and chemical methods. Measurements of the texture, pectins, hemicelluloses, cellulose, nitrogen, ash and ash constituents, were made on raw, frozen and canned samples. The tissues were sliced, macerated with 0.4 percent sodium hexametaphosphate, and screened. The cell suspensions were dialysed and stored at 35°F, with toluene as a preservative. The cell suspensions were analyzed similarly to the tissue samples, and the reactivity of the cell suspensions with sugars and electrolytes was investigated. The results indicated the following conclusions: 1) No significant difference was found between the effects of canning and freezing on the texture of the fruits, as determined by the Shear Press, although major differences were found between the fresh and processed samples. 2) Drained weights were lower when the fruits were canned than when frozen, especially in the strawberries. 3) Histological changes brought about by the treatments were more marked in the frozen than in the canned fruits. Freezing caused severe breakage of cell walls, plus some cell separation, whereas canning tended to cause more shrinkage of cells without much breakage or separation. Adhesion between cells was increased in the heated packs. Damage to cells increased as cell size increased. The study showed that more emphasis should be placed on selecting varieties of fruits for processing which have a smaller mean cell size, and thicker cell walls. 4) Aqueous suspensions of parenchyma cells were found to be a useful means of studying the several mechanisms involved in textural and drained weight changes. 5) No sorption affinity was found between dialysed, depectinized parenchyma cells and sucrose or glucose. 6) Dialysed cells were negatively charged, highly hydrated, and formed viscous suspensions at low concentrations. 7) The addition of small amounts of cations, particularly H⁺ ion and Al⁺⁺⁺ ion, precipitated cell suspensions, by suppressing the ionization of the carboxyl group or by salt formation. 8) A new hypothesis was proposed which assigned an important role to the acids and other electrolytes of fruits, in governing the textural and drained weight characteristics of such products. It was proposed that the quantity of acids and other electrolytes which become distributed throughout the cell during processing, causes a reduction of cell hydration including a shrinkage of cell walls, which could be partially reversed during subsequent storage. / Graduation date: 1963

Graduation date: 1960

The purpose of this study is to determine the reduced and dehydroascorbic acid of certain frozen fruits prepared with and without ascorbic acid as an antioxidant.

Heat treated orange juice, both pasteurized and concentrate, are being increasingly consumed in the U.S. Orange juice is primarily heat treated to increase its shelf life, by curbing the growth of microorganisms; and to inactivate pectin methylesterase, which demethylates pectin and leads to cloud loss in the juice. However, because of heat processing, orange juice undergoes undesirable flavor changes that decrease its acceptability to consumers. The objectives of this study were to differentiate between fresh frozen and heat treated orange juice employing descriptive analysis, and to determine by Osme, a gas chromatography-olfactometry (GCO) method, odor active volatiles that were either lacking or created in the heat treated juice. The second objective was to determine how changes in the odor-active volatile profile of heat treated orange juice, relates to changes in the aroma and flavor intensities of the samples as assessed by descriptive analysis. Through descriptive analysis, the panel was successful in significantly (p<0.05) separating the fresh, pasteurized, and concentrate samples. Orange, orange peel, sweet, and grassy descriptors were found to be important for fresh aroma and flavor, while cooked, yam, metallic, tamarind, green bean and artificial orange descriptors were higher in heat treated samples. Using Osme, it was possible to separate fresh frozen from heat treated orange juice, on the basis of their aroma profiles. Fresh frozen samples show a higher concentration of peaks tentatively identified as gamma-butyrolactone, citral, nonanal, carvone, perillaldehyde, carvyl propinate, valencene, and other unidentified peaks possessing descriptors such as floral, lime, citrus, pine, bamboo leaf, metallic, and vinyl. Pasteurized samples show a larger concentration of peaks tentatively identified as hexanol, octanol, nerol / carveol, myrcene, 2-octanone, p-cymene, terpenen-4-ol, betacitronellol, and other unidentified peaks with descriptors such as cilantro, vinyl, melon, mushroom, and metallic. Descriptors such as orange, orange peel, sweet, grapefruit, and grassy are more pronounced in the fresh samples and are similar to the odor descriptors of Osme peaks higher in the fresh samples. Descriptors such as cooked, artificial orange, yam, metallic, tamarind, and green bean are higher in the pasteurized samples, and are similar to the odor descriptors of peaks higher in these samples. / Graduation date: 1999

The present study was undertaken to compare the ascorbic acid content of canned and frozen fruits before and after preparation for quantity use.

This investigation was carried out in order to determine whether or not blanching and freezing tends to reduce the incidence of bacteria, particularly those of the coliform group, and also the yeasts and molds.