Graduation date: 1961

Graduation date: 1961

Peas (Pisum sativum) are an important constituent in the diet of many people. Peas may be cooked and eaten as green peas shortly after harvest, stored for short periods in the pods, or, after suitable treatment, stored for long periods before consumption. Many factors influence the yield and quality of frozen peas but maturity requires careful consideration because of the relation of maturity to color, flavor, and texture. The objectives of this thesis were to determine the effect of the maturity stage on the quality of the frozen peas during processing and storage and to correlate the interactions between the sensory evaluation panel with the physical and chemical quality factors measured. Venus pea variety grown under commercial conditions at the Sublimity area east of Salem, Oregon, were used in this study. The trials were randomized, for three stages of maturity with three replications per each stage of maturity. Each of the three maturity stages was harvested; vined; blanched by steaming at 98.8°C (210°F) for 30 sec for the immature peas, 60 sec for the mature peas, and 90 sec for the overmature peas; frozen at -37.2°C (-35°F) for 24 hr in an air blast freezer and stored at -23.3°C (-10°F) for 4 and 8 month. During processing and. storage the following factors were determined: tenderometer value, total solids, alcohol insoluble solids, peroxidase activity, ascorbic acid., total sugars and sensory evaluation. In the sensory evaluation analysis starchiness, sweetness and tenderness intensity, as well as texture, flavor and overall desirability were measured. Analysis of variance and least significant difference were used to compare the effect of pea maturity during processing and storage on the different quality factors measured. Correlation coefficients were used to determine the relationship between these factors. Immature peas had lower tenderometer value than overmature peas. Tenderometer value of peas decreased, during processing. The highest total solids content was observed, in the overmature peas and the lowest total solids content in the immature peas. This behavior was also observed in the alcohol insoluble solids content. Raw peas in the three maturity stages had the same initial peroxidase activity and the significant effect of the maturity level found in the residual peroxidase was affected by the different blanching time applied at each maturity stage. The ascorbic acid content was significantly affected, by the maturity level and was reduced during the blanching treatment. Total soluble sugar content was higher in immature peas and lower in overmature peas. All the sensory evaluation parameters measured were affected by the maturity. In general, the taste panel found higher flavor desirability on the mature peas but when texture and overall desirability were measured immature and mature peas were equally preferred. Significant correlations were found between physical, chemical, and sensory parameters analyzed, some of them are tenderometer value and alcohol insoluble solids; total solids and alcohol insoluble solids; alcohol insoluble solids and overall desirability. / Graduation date: 1981

The effect of round shrimp post-catch age on the frozen shelf-life characteristics of processed cooked meat was evaluated. Refrigerated shrimp, one, three, and five days post-catch, were cooked, mechanically peeled, frozen at -29°C and held for a period of twelve months at -18°C. At three month intervals, samples were subjected to chemical and sensory evaluation. Levels of trimethylamine oxide (TMAO), trimethylamine (TMA), dimethylamine (DMA), formaldehyde (FA), inosine monophosphate (IMP) and hypoxanthine (Hx) were determined. Sensory evaluations included judgements for texture, juiciness, flavor, and overall desirability. The degradation of frozen cooked meat quality was directly related to round shrimp age. Flavor panel scores for meat from one day old shrimp decreased in a linear manner with regard to texture (r= -.933, P .005), juiciness (r= -.795, P .005), flavor (r= -.861, P .005) and overall desirability (r= -.919, P .005). The change in the quality of the meat from three and five day old shrimp with respect to storage time was largely non-linear and after an initial quality reduction during the first three months flavor panel scores were relatively stable. Scores for frozen meat during the first six months were equal, but the more rapid deterioration of meat from one day old shrimp yielded scores inferior to those for meat derived from three and five day old shrimp after twelve months. Initial levels of TMAO, TMA, IMP and Hx in cooked meat reflected the age of round shrimp. Differences in levels were related to chemical decomposition, drip loss and/or bacterial out growth. DMA and FA levels were low and not related to round shrimp age. No Hx was detected in meat from one day old shrimp and only low levels were detected in meat from three and five day old shrimp. TMAO decomposed during storage to yield DMA and FA. TMAO levels decreased in a roughly linear manner. DMA formation was neglegible during the first six months, but increased during the latter six months of storage in a manner inversely related to round shrimp age. The rates of DMA formation did not show a direct inverse proportionality. Formaldehyde was formed during the first three months of storage, but determined levels between three and twelve months were constant, probably reflecting its high reactivity with protein. Determined IMP and Hx levels were relatively constant. Levels of TMA were stable for the first nine months, but decreased during the last three months, concurrent with the rapid formation of DMA. The degree of quality deterioration during storage was closely associated with the decomposition of TMAO. . The regression of TMAO and DMA levels on scores for meat from one day old shrimp yielded significant positive and negative correlations, respectively. Levels in meat from three and five day old shrimp were not correlative with the observed non-linear quality degradation. Initial levels of TMAO, while not correlative with initial panel scores, did correlate with scores after twelve months. The regression of initial TMAO levels in meat from one, three and five day old shrimp on scores yielded significant negative correlations for texture (r= -.936, P [greater than or equal to] .005), juiciness (r= -.825,P [greater than or equal to] .01) and flavor (r= -.752, P [greater than or equal to] .025). Similarly, texture (r= -.910, P [greater than or equal to] .005), juiciness (r= -.815, P [greater than or equal to] .01), flavor (r= -.670, P [greater than or equal to] .05) and overall desirability (r= -.783, P [greater than or equal to] .025) scores correlated in a significant manner with DMA levels determined for meat stored twelve months. The findings of this investigation support the involvement of TMAO and its decomposition products in mediating the frozen shelf-life of Pacific shrimp. / Graduation date: 1978

A quality problem that frequently occurs with frozen green beans is the sloughing of the skin (epidermal tissues) of the cooked, ready-to- serve bean pods. It was found that by giving the beans a pre-blanch (relatively mild heat treatment) prior to the blanch treatment normally used for frozen green beans, on cooking, sloughing was markedly reduced, and furthermore, the bean pods were firmer. As an additional heat treatment was involved, over and above what is now used for commercial packs of frozen green beans, it was of interest to know the extent to which the color of the beans was affected. Also of interest was the effect of storage at 0°F for four months on the color of the beans. The color changes in the dual and single blanched green beans were evaluated by two methods: (1) a physical analysis of the light reflected from the beans (Hunter Color and Color Difference Meter) and, (2) a physical analysis of the light absorbing properties of the pigments extracted from the beans and subsequent calculation of the per cent conversion of chlorophyll to pheophytin. Texture (firmness), as indicated by resistance to shear, was measured by a modified Kramer Shear Press. A mechanical device was used to determine the amount of sloughing of the skins of the bean pods. After a statistical analysis of the data collected in the experiment, the following conclusions were drawn: 1. The firmness of the cooked, dual and single blanched, frozen green beans, as measured by the shear press, was found to be highly significantly negatively correlated with sloughing of the skins. 2. There was no change in lightness or darkness of the color of single or dual blanched beans over storage at 0°F for four months. The Hunter "-a [subscript L]/b [subscript L]" index of color noted a significant change in hue from green towards yellow of the single and dual blanched beans. The conversion of chlorophyll to pheophytin was not significant over storage. 3. The color of those beans receiving the 200°F - 150 second final blanch (single blanch) was the same as the color of those beans receiving the 210°F - 105 second final blanch (single blanch). 4. As the time and temperature of the pre-blanch increased, there was a corresponding increase in the amount of chlorophyll converted to pheophytin, and a change in the visual color of the beans from green towards yellow. The effect of variations of time of preblanch was much greater on the color of the dual blanched beans than the effect of variations of temperature of pre-blanch. 5. As the time and temperature of the pre-blanch increased, the texture (firmness) of the cooked dual blanched beans increased. The 200°F - 150 second final blanch resulted in beans that were firmer than beans receiving the 210°F - 105 second final blanch, 6. A pre-blanch at 170°F for 30 seconds followed by a final blanch at 200°F for 150 seconds was found to result in beans that were similar in color, yet firmer in texture (less sloughing of the skins) than the single blanched beans. / Graduation date: 1963

No description available.

Graduation date: 1960

Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 154-161). Also available via the Internet.

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 193-212).

Thesis (M. Sc.)--Carleton University, 1988. / Also available in electronic format on the Internet.