No description available.

Fresh and fresh-cut tomatoes have been associated with numerous outbreaks of salmonellosis in recent years. While the exact routes of contamination are unknown, high pressure processing (HPP) is being evaluated as a post harvest treatment to eliminate Salmonella enterica from tomatoes. The objectives of the study were to determine the potential for of HPP to reduce S. enterica serovars Newport, Javiana, Braenderup and Anatum (clinical isolates from tomato outbreaks) in tryptic soy broth (TSB) and to determine the effect of HPP to reduce the most pressure resistant S. enterica serovar from fresh diced and whole tomatoes. Five ml portions of broth containing 8 log CFU/ml of one of the four serovars (nalidixic acid resistant) were packaged in sterile stomacher bags and subjected to one of three different pressures (350, 450, or 550 MPa) for 120s. Samples were enumerated by surface plating onto tryptic soy agar supplemented with 50 ppm nalidixic acid (TSAN) and incubated at 35°C for 48 hours. The most pressure resistant S. enterica serovar evaluated was Braenderup. Subjecting the broth culture to 350, 450 and 550 MPa resulted in a 4.53, 5.74 and 7.09 log reduction in S. Braenderup, respectively. Diced tomatoes (150g) and whole red round tomatoes (150g; packaged in 350ml of 1% CaCl2) were inoculated with S. Braenderup, to obtain 6 log CFU/g throughout the sample and subjected to the same pressure treatments as described above. After HPP, diced tomatoes were homogenized for 1 minute and then plated on TSAN. Whole tomatoes were surface sampled, and then homogenized for 1 minute. Surface and homogenate samples were plated on TSAN supplemented with 1% pyruvic acid (TSANP). Significant reductions of S. Braenderup concentrations in diced tomatoes (P < 0.05) were seen after processing at 350 (0.46 CFU/g), 450 (1.44 log CFU/g), and 550 MPa (3.67 log CFU/g). In whole tomatoes, significant reductions (P < 0.05) were also seen at 350 (1.41 log CFU/g), 450 (2.25 log CFU/g) and 550 MPa (3.35 log CFU/g). There were no differences in visual appearance between fresh and HPP diced and whole tomatoes. HPP may be an effective post harvest strategy to reduce low levels of S. enterica contamination in diced tomatoes. / Master of Science in Life Sciences

Master of Science / Food Science Institute / James L. Marsden / Consumers demand for high quality, natural and fresh tasting food, free from preservatives and additives, with a clean label and an extended shelf life has increased. High pressure processing (HPP), also known as high hydrostatic pressure, is a non-thermal food preservation technique that has the potential to meet these demands. It is an opportunity to preserve food, by applying intensive pressure in the range of 300-900 MPa, without adversely affecting organoleptic, textural and nutritional qualities as thermal processing like pasteurization and sterilization may do. In a typical high pressure batch cycle, the food prepackaged in a high-barrier flexible pouch or a plastic container is loaded into a perforated basket that goes into the pressure vessel; the pressure is then increased to the processing target pressure (come-up time); the product is held at the desired pressure for 3 to 10 minutes (pressure holding time); after which the pressure is released in usually few seconds (decompression time) and the product can be unloaded at this point. The pressure is applied uniformly in all directions simultaneously and this is known as isostatic pressure. Pressurization is usually accompanied by a moderate and uniform temperature increase called adiabatic heating. However, the food product usually rapidly returns to its initial temperature at decompression. With the recent shift in consumer lifestyle toward healthy living and healthier food, the consumption of raw fruits and vegetables has increased in popularity. However, as per the Centers of Disease Control and Prevention, fruits and vegetables have recently been associated with multiple foodborne disease outbreaks; the effect of high pressure processing on microbial safety, quality and sensory characteristics of fruits and vegetables has therefore been widely investigated as an alternative to traditional food processing and preservation methods. HPP inactivates microorganisms and quality-deteriorating enzymes and has limited effects on covalent bonds resulting in minimal modifications of food-quality attributes such as color, flavor and nutritional values. However, depending on the fruit or vegetable, high pressure could induce chemical or biochemical reactions that can affect their quality attributes.

The objective of this work was to determine the effect of high pressure processing (HPP) on fresh tomato-associated outbreak isolates of Salmonella enterica in broth and on green mature tomato fruits. Nalidixic acid resistant (to 50 ppm) cultures of Salmonella enterica ser. Newport and Salmonella enterica ser. Braenderup were suspended in tryptic soy broth to a concentration of approximately 8 log CFU/ml and subjected to 350, 450, and 550 MPa for 120 s. Samples were serially diluted in peptone water, and surface plated onto tryptic soy agar supplemented with nalidixic acid (50 ppm; TSAN) and incubated at 35°C for 48 h. Reductions of 5.64, 6.30, and 6.61 log CFU/ml in S. Newport, and reductions of 4.10, 5.22, and 6.35 log CFU/ml in S. Braenderup at 350, 450, and 550 MPa, respectively, were observed. Green tomato fruits inoculated with S. Newport or S. Braenderup to an initial concentration of approximately 6 log CFU/g were sealed in a bag containing 350 ml of 1% CaCl2 and subjected to the same pressure treatments described above. The whole tomato fruits were pummeled in a stomacher and samples were surface plated onto TSAN supplemented with 1% pyruvic acid. Reductions of 1.55, 2.89, and 4.26 log CFU/g for S. Newport and 1.22, 2.26, and 3.77 log CFU/g for S. Braenderup at 350, 450, and 550 MPa, respectively, were observed. Bagged (350 ml 1% CaCl₂) samples of non-inoculated green tomato fruits were subjected to the same conditions described above. HPP treated tomatoes were then subjected to an ethylene gas (125 ppm; 0.7 cc/min) for 5 to 6 days. Pressured tomato fruits did not ripen. Even though HPP effectively reduced populations of S. enterica, it adversely affects the ripening characteristics of green mature tomato fruits. / Master of Science in Life Sciences

No description available.

Juices have been implicated in numerous foodborne outbreaks over the last couple of decades. The FDA requires a 5-log10 reduction in juice products, which is most commonly achieved through pasteurization. However, pasteurization deteriorates some sensorial properties and nutritive value. Coconut water (CW; classified as a juice), is rapidly gaining popularity increasing over 300% since 2005. CW has not been implicated in a microbial outbreak, but is thermally processed to achieve the required 5-log10 CFU/ml reduction, which results in negative organoleptic properties. The objectives of this study are to determine whether E. coli O157:H7, Salmonella enterica serovar Typhimurium, and Listeria monocytogenes can grow in CW, and evaluate the use of High Pressure Processing (HPP) to reduce populations of these bacteria in CW. The three pathogens were inoculated separately into CW and bacterial populations were enumerated over 24 hours. All three bacteria reached at least 8-log10 CFU/ml after 24 hours, which was not significantly different from the control (TSB). CW was then inoculated with each pathogen and processed using HPP (400, 5000, or 600 MPa) for 120 seconds. The D-glucose, D-fructose, sucrose, and phenol oxidase levels in the CW were assessed before and after treatments. Following processing, the pathogens were enumerated from the CW. All three pathogens were reduced by more than 6-log10 CFU/ml following treatments of 500 and 600 MPa, enough to achieve the mandatory 5-log CFu/m reduction. There were no significant changes in the D-glucose, D-fructose, sucrose, and phenol oxidase activity after any of the treatments. / Master of Science in Life Sciences

Encephalitozoon cuniculi is a zoonotic protozoan parasite in the phylum Microspora that has been shown to naturally infect several host species, including humans, rabbits and dogs. Currently, serological diagnosis of infection is made using the immunofluorescense assay (IFA) or enzyme-linked immunosorbent assay (ELISA). Although these methods are sensitive and reliable, there are several drawbacks to both tests. Cross-reactivity between other Encephalitozoon species is common, and specialized equipment is required for IFA and ELISA. Most wildlife species are unable to be tested using these methods, because species-specific antibodies are required. One goal of this work was to develop a new serological test for diagnosing E. cuniculi infection that would be more practical for use in small veterinary and medical clinics. The effectiveness of the agglutination test was examined in CD-1 and C3H/He mice infected with E. cuniculi or one of 2 other Encephalitozoon species. The results indicate that the agglutination test is 86% sensitive and 98% specific for E. cuniculi, with limited cross-reactivity to E. intestinalis. The test is fast and easy to conduct, and requires no specialized equipment or species-specific antibodies. Recent reports of microsporidial DNA in crop irrigation waters suggest that unpasteurized juice products may be contaminated with E. cuniculi. High pressure processing (HPP) is an effective means of eliminating bacteria and extending the shelf life of products while maintaining the sensory features of food and beverages. The effect of HPP on the in vitro infectivity of E. cuniculi spores was examined. Spores were exposed to between 140 and 550 MPa for 1 min, and then spores were loaded onto cell culture flasks or were kept for examination by transmission electron microscopy (TEM). Spores treated with between 200 and 275 MPa showed reduction in infectivity. Following treatment of 345 MPa or more, spores were unable to infect host cells. No morphologic changes were observed in pressure-treated spores using TEM. The effect of disinfectants on in vitro infectivity of E. cuniculi spores was also examined. Spores of E. cuniculi were exposed to several dilutions of commercial bleach, HiTor and Roccal, and 70% ethanol for 10 minutes and then loaded onto Hs68 cells. The results of this study showed that all concentrations of disinfectants tested were lethal to E. cuniculi spores. Encephalitozoon cuniculi spores are more sensitive to disinfectants than are coccidian oocysts and other parasite cysts. / Master of Science

No description available.

Turkey with pale, soft, exudative (PSE)-like condition is one of the growing concerns in the poultry industry as it affects meat quality due to low ultimate pH at 24 h post mortem (pH24). Hence, there is a need for better utilization of PSE-like meat for the preparation of further processed products. In the first two studies, the biochemical, functional, rheological, and textural properties of proteins in turkey breast meat with different pH24 in fresh and frozen conditions were investigated. These studies revealed that low and normal pH meat had similar properties indicating similar extent of protein denaturation, except for lower water holding capacity (WHC) in low pH meat. High pH meat had similar or better functional properties than normal pH meat. In the third study, improvements in WHC, protein solubility, and gel forming ability of low pH meat was achieved by the application of high pressure processing (HPP). / Food Science and Technology

No description available.