A two part study was designed to investigate radiation-induced structural and nutritional changes in food proteins. Model systems composed of 0.1-10% myoglobin, lactalbumin or BSA were used and the effects of propyl gallate, ascorbic acid, air or nitrogen, pH 5, 6 or 7 citrate or phosphate buffer, and addition of glucose and SDS were investigated. We found that 0.02-0.04% propyl gallate (PG), alone or in conjunction with other solutes, inhibited protein aggregation after irradiation to 0.5 and 1.0 megarad and subsequent -20 C storage for 3-6 months. PG alone at 0.04% yielded up to 90% retention of myoglobin after 0.5 megarad and up to 94% retention of lactalbumin after 1.0 megarad as compared to unirradiated controls. BSA appeared more radiation sensitive than other proteins, and use of 0.02% PG yielded retention of only 10% of the original protein after 1.0 megarad. Use of synergists such as glucose or SDS together with PG allowed up to a two-fold increase in protein retention, while use of 0.02% ascorbic acid led to lower retention compared to samples irradiated alone in control buffer. Irradiations at pH 5 and 6 yielded greater protein retention than at pH 7. Isoelectric focusing of myoglobin revealed acidic shifts in protein pI with new bands at pH 4.9-5.2 after irradiation at pH 6 with glucose and PG. A similar acidic shift was seen in focusing lactalbumin, with major new bands forming at pH 3.7-4.0 after irradiation in pH 6 phosphate with 0.04% PG. BSA showed a bipolar pattern of pI shifts after irradiation in pH 6 phosphate. Mice fed irradiated lactalbumin in factorial studies grew slightly faster and ate more than unirradiated controls, while those fed protein irradiated with 0.02% PG showed slightly decreased rates of gain and feed consumption. Amino acid analysis revealed a 35% decrease in lysine, as compared to control, in diets prepared with protein irradiated to 1.0 megarads in 0.05 M phosphate, pH 6 with 0.02% PG. The negative effects of PG on feeding and growth were reduced when protein was irradiated at 22.5% rather than 15% (w/v). Liver to body weight ratios among animals fed protein irradiated with PG were decreased by 18% in contrast to control animals fed identical, though unirradiated, diet. (Abstract shortened with permission of author.)

The effect of gamma irradiation on the emulsifying capacity of turkey light meat was studied in a model system. A change of emulsifying capacity due to the changes of functional capabilities of salt-soluble proteins were studied on the irradiated salt-soluble-protein extract by disc electrophoresis, viscometry, fluorescence spectroscopy and measurement of pH. The formed emulsions were taken for examination of the particle size under the microscope, measurement of the viscosity with a Haake Rotovisco Viscometer, and for the determination of the stability by a method of centrifugation and cooking. Irradiation of turkey meat at doses of 1 or 3 Mrad increased the emulsifying capacity of the tissue but doses of 2 or 4 Mrad decreased capacity relative to an unirradiated control. Irradiation had no effect on the extractability of salt-soluble proteins. The emulsifying capacity of irradiated salt-soluble-protein extract increased significantly ( p≤0.05 ) and viscosity decreased significantly ( p≤0.05 ) with increasing dose of irradiation from 0 to 2 Mrad. Doses of 3 or 4 Mrad failed to produce further significant change in either variable. Irradiation of the salt-soluble-protein extract also resulted in a decrease in particle size of the emulsion; an increase in viscosity of the emulsion; an increase of hydrophobic effect in the salt-soluble-protein molecule; an increase in the electrophoretic mobility of the two main protein fractions on polyacrylamide gel; an increase in pH; and an increase in the stability of emulsions judged on the basis of volume of oil in the supernatant after centrifugation and cooking. / Land and Food Systems, Faculty of / Graduate

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains ix, 59 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Read the abstract in the section 00front of this document. / Thesis (DPhil (Food Science))--University of Pretoria, 2006. / Food Science / unrestricted

The effects of irradiation dose (0, 0.5 and 1.0 kGy), various gas atmospheres and storage temperature (5, 15 and 25$ sp circ$C) on the physical, chemical, microbiological, and organoleptic changes in fresh pork were studied using factorial design experiments. The effects on toxin production by Clostridium botulinum were also investigated using challenge studies. Shelf life could be extended to 21 d when product was packaged in 0% O$ sb2$, irradiated at 1.0 kGy and stored at 5$ sp circ$C compared to 4 d for control samples. While the presence of O$ sb2$ in the package headspace enhanced the antimicrobial effects of low-dose irradiation, it adversely affected the organoleptic qualities of pork. Botulinum toxin was detected after only 2 d in all inoculated treatments stored at 25$ sp circ$C. At 15$ sp circ$C, toxin was produced faster when pork was initially packaged with O$ sb2$ or low levels of CO$ sb2$ (15-30%) as compared to 100% N$ sb2$. Higher levels of CO$ sb2$ (45-75%) delayed toxin production. In most treatments, spoilage preceded toxigenesis. Models were developed relating the above factors to the time until toxin production and to the probability of toxigenesis. Temperature, initial O$ sb2$ and irradiation were all significant factors.

Thesis (Ph.D.)(Food Science)--University of Pretoria, 2005. / Includes summary. Includes bibliographical references.

Thesis (M.S.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xi, 87 p. : ill. Vita. Includes abstract. Includes bibliographical references.

Ph.D. (Chemistry) / Please refer to full text to view abstract

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Doctor of Philosophy / Department of Agricultural Economics / John A. Fox / Mail surveys are used to gather information in order to make inferences about populations. This study examines cost effective methods to maximize response rates to a mail survey. A consumer mail survey was developed and used to study consumer demand for safer foods. In addition, the study will verify if additional responses from follow-up mailings changes econometric analysis results, thus validating follow-up mailing costs. A test was created to maximize response rates and incentives were used in both mailings. An Ordinary Least Square (OLS) model was developed to analyze response rates and mail survey costs while a willingness to pay model and an ordered probit were used for the consumer demand analysis. Results showed that when a consumer survey was sent to a city within the school's state no incentive should be included while if sent to a city outside the school's state an incentive should be included. Moreover, if the outcome from the first mailing resulted in a low response rate a monetary incentive should be included in the follow-up mailing to increase response rates. Results from the consumer willingness to pay for irradiated salad greens showed that consumers are willing to pay higher prices for irradiated salad greens. Furthermore, results showed that there is no statistical difference between the coefficients, in both the willingness to pay and the ordered probit, from the model using additional observations from follow-up mailing and the model that included only observations from the first mailing. Even though coefficients were not statistically different in the ordered probit, significance of the marginal effects for some variables were different between models.