Typescript (photocopy). / Digitized by Kansas Correctional Industries

Extended shelf-life cook-chill meals can pose a potential risk of botulism if they are subjected to a temperature abuse. Spores of group II non-proteolytic Clostridium botulinum can survive the mild heat treatment typically given to these products and can grow at refrigeration temperatures. To circumvent this safety issue, existing preservation methods can either affect the sensory properties of these foods or damage their image. Therefore, additional natural preservation hurdles are needed. Thus, the aim of this study was to develop a novel bio-preservation method based on the principle of antibiosis between protective cultures (PCs) and C. botulinum. Consequently, the objectives were to select effective anti-botulinal cultures and study their inhibition pattern in microbiological media and foods, identify the conditions for effective inhibition and the nature of the antibiosis. This research demonstrates for the first time that the bacteriocinogenic protective cultures inoculated at high levels had an anti-botulinal effect in a range of commercial cook-chill products, which supported active growth of non-proteolytic C. botulinum. The protocol for commercial application of the protective cultures was developed. / Doctor of Philosophy (PhD)

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

Initial experiments were conducted to determine the microbial development in blocks of ground beef. In the top layers of the meat, Pseudomonas spp. predominated. Attempts were made, as well, to measure the microenvironmental changes occurring in ground beef using pH, oxygen, and redox potential micro-electrodes. / Some of the extrinsic (relative humidity, O(,2)), as well as intrinsic factors (pH, redox potential, ions, nutrients) affecting microbial development in aerobically stored meats, were examined. The decrease in glucose levels observed during the aerobic storage of longissimus dorsi (l. dorsi) muscle at 4(DEGREES)C, was accompanied by an increase in the activity of glucose dehydrogenase, and by the appearance of gluconate and 2-ketogluconate on the meat surface. / The attachment of various meat spoilage organisms to l. dorsi muscle was studied. Generally, the pseudomonads attached in higher numbers than the other bacteria, but possessed lower attachment strengths. Investigations on the attachment of two competing organisms to l. dorsi muscle demonstrated that limited competition occurs between the organisms. / A model of the microbial ecology of aerobically stored fresh beef was developed, based on existing evidence. / Various chemicals were added to minced or whole meat to evaluate their effectiveness as food preservatives. As a single compound, potassium sorbate appeared to have the greatest potential as a meat preservative. Meats > into solutions of 5.0% potassium sorbate for 1 min had their shelf-life substantially increased as compared with control samples > into water.

The application of pulsed electric fields (PEF) in food processing is a novel technique that requires careful study. In addition, improved understanding of the effect of PEF parameters on both physical and qualitative attributes of agrifood products is a requirement for the application and control of this emerging technology. PEF parameters investigated were pulse widths of 100, 200, and 300 mus, with electric field strengths of 0.75 and 1.5 kV/cm. The amount of pulses used for apples was up to 60, whereas up to 120 pulses were used for potatoes. Initially, apple and potato slices were exposed to various combinations of PEF parameters in order to evaluate the change in their electrical conductivities as an indicator of the disruption of the cell membrane. Subsequently, the impact of PEF on color and texture attributes was studied. In the final set of experiments, PEF was applied as a pre-treatment in order to accelerate the diffusion of moisture in a convective air-drying process at 70°C. / Results regarding the electrical conductivity and the changes in color revealed the similar effect of applying pulses with 100, 200 and 300 mus of duration. Increasing the number of pulses and/or the electric field strength resulted in increased electrical conductivity and discoloration rates of samples. PEF reduced the compressive strength of apple tissues between 21 to 47%. However, the compressive strength of potato tissues did not seem to be affected by the application of PEF. When PEF was applied as a pre-treatment, it caused an increase of up to 30% in the moisture diffusion coefficients of potatoes. In the case of apples, PEF pre-treated samples did not show any increase in drying rates.

The fish processing industry is actively seeking for alternative methods of shelf life preservation and marketability of fresh fish, while at the same time economizing on energy costs. Two methods which fulfill both objectives are modified atmosphere packaging (MAP) and glucose oxidase (GOX)/Glucose dipping solutions. MAP is the packaging of perishable products in an atmosphere other than that of air and is used for the shelf life extension of beef, pork, fruits, vegetables and bakery products. GOX, either alone or in conjunction with MAP has the potential for shelf life extension of fresh fish. / The objectives of this study were to determine the combined effect of glucose oxidase/glucose or gluconic acid dipping solutions and modified atmosphere packaging in conjunction with refrigeration on the shelf life extension of mackerel and cod. / This study has shown that the shelf life of fresh fish can be extended through the combined use of MAP/dipping solutions and refrigeration. This novel process of "dipping" in GOX solution in conjunction with modified atmosphere packaging (MAP) will have a significant effect in the area of fish hygiene and will minimize fish losses incurred through spoilage.

Value-added trout burgers and trout wontons were prepared from minced trout trimmings, oats, dried onion flakes, white pepper, cayenne pepper, garlic powder, soy sauce, spice mix and eggs. The trout burgers were coated with crushed cornflakes and then partially cooked (2 min at 140ºC) or frilly cooked (5 min at 140ºC) in hot oil. Similar fillings were used to prepare trout wontons by wrapping the mixture with Chinese wonton dough and 2 products were made: raw wonton (uncooked) and fried wonton (fried for 8 min at 140ºC). / Storage trials were performed on raw and fried trout wontons (a w 0.98--0.95, pH 6.5), and partially and fully cooked trout burgers (aw 0.97--0.96, pH 6.4). Products were packaged in air and under various modified atmospheres (MAP), and stored at 4 and 12ºC. A microbiological shelf-life of >28 days was possible for the cooked trout burgers and fried wontons stored at 4ºC. In general, the microbiological shelf-life preceded the sensory shelf-life. / Subsequent challenge studies were done to address the safety concerns associated with MAP food. All products were inoculated with 102 CFU/g of Listeria monocytogenes and 102 spores/g of Clostridium botulinum type E spores. Gas packaging with 80% CO2 (balance N2) inhibited the growth of L. monocytogenes in products stored at 4ºC. However, counts of L. monocytogenes increased in all other packaging conditions. In challenge studies with C. botulinum type E, toxin was not detected in any products after 28--60 days.

Graduation date: 1991

No description available.

CAPES / A quitosana é um polímero abundante e oriundo principalmente de crustáceos a qual vem sendo amplamente estudada em vários segmentos inclusive como coberturas comestíveis de frutas. Frutas e hortaliças sofrem com a ação do clima, insetos e injurias do pós colheita; atentos a isto, pesquisadores vem estudando e desenvolvendo coberturas comestíveis que protejam a integridade dos vegetais. As coberturas de quitosana podem ser funcionalizadas com outros compostos que melhorem as suas características bem como a sua resistência pode ser aumentada com o uso de agentes reticulantes. / Chitosan is an abundant polymer and derived mainly on crustaceans which has been widely studied in various segments including as edible fruit toppings. Fruits and vegetables suffer from climate action, insects and injuries of post harvest; aware of this research has been developing and studying edible coatings that protect the integrity of the plants. The chitosan covers can be functionalized with other compounds that improve its characteristics and its strength can be increased by the use of crosslinking agents. / 5000