Master of Science / Department of Animal Sciences and Industry Food Science / Elizabeth Boyle / Unpasteurized fruit juices have been implicated as the source of foodborne outbreaks due to pathogens such as Salmonella, Escherichia coli O157: H7 and Cryptosporidium parvum. The growth of pathogens can usually be slowed through freezing or largely eliminated through pasteurization. Although pasteurization is often effective in eliminating pathogens, it often yields undesirable flavors that are unlike those of fresh juice. Growing consumer trends towards “healthy” unpasteurized alternatives are fueling the development of alternative processing techniques. Several promising techniques for pathogen reduction in the processing of fruit juices are currently being developed. A new technique that is already being marketed worldwide is hyperbaric processing (HPP) which subjects the fruit juice to a high pressure of up to 1000 MPa. The high-pressure treatment results in up to a 7 log reduction kill in pathogens while preserving the naturally occurring flavor profile, sensory attributes and nutritional benefits. Pulsed electric fields (PEF) and ionizing radiation are also being widely explored as viable techniques to process unpasteurized fruit juices. PEF promises to be a commercially viable energy efficient alternative to pasteurization, adding only $0.03 – $0.05 per liter to final food costs. Although irradiation enjoys support for use in the processing of fruit juice by regulatory agencies, support in public opinion is lacking and hinders its growth as an alternative to pasteurization. Other experimental techniques are also present in the development pipeline. Ultrasonic radiation and high intensity pulsed light radiation are both experimental techniques that are being researched. A particularly exciting alternative is the use of plant-based antimicrobials. Several fruits and spices are known to be natural antimicrobials and are therefore being researched as alternatives to the traditional chemical preservatives.

As Uganda works to transform itself into an industrialized, middle-income country in the coming decades, the country is faced with a number of problematic trends that could hinder this transition. High population growth and urbanization are quickly forcing small towns to deal with issues of limited space and the aesthetic conditions within sanitation systems, while declining soil fertility in surrounding rural areas calls into question the future nutritional security of the growing population. Ecological Sanitation (Eco-San) systems, which are designed to recover nutrients from human excreta, may help to address these trends. Improved sanitation coverage in Uganda is currently estimated to be 34%, with most people using either improved or unimproved pit latrines. Eco-San systems, especially Urine-Diverting Dry Toilets (UDDTs, also referred to as composting toilets), have been promoted in the country, but uptake has been slow. Additionally, while UDDTs generally treat human feces to a greater degree than pit latrines and composting toilets (another type of Eco-San system), concerns have been raised as to the inactivation of environmentally persistent pathogens, such as Ascaris lumbricoides eggs. This research focused on two potential solutions to the issues of effective promotion and Ascaris inactivation, evaluating them in the context of Kalisizo, a small town in southern Uganda. Demonstration facilities have been reported to effectively convince local stakeholders of the benefits and advantages of UDDTs, thereby increasing long-term uptake of the technology in the surrounding community. However, an unresolved question concerns whether these facilities should be installed in household or institutional settings. The initial effects of demonstration facilities constructed at local primary schools in Kalisizo were evaluated by assessing local knowledge and attitudes regarding UDDTs, both before installation and after several months of operation, through focus group discussions and key informant interviews. In general, this promotion strategy proved to be successful. After installation, students exhibited a marked increase in knowledge regarding these facilities and their benefits, and opinions were strongly positive. These changes were seen in users of the facilities as well as non-users, and students expressed clear acceptance of using the products of the toilets to fertilize crops. The introduction of an improved sanitation system at the schools also appears to have sparked other improvements related to sanitation and hygiene. In the future, it is likely that students will be compelling representatives for UDDTs within their households and communities. Regarding the treatment of persistent pathogens, previous work has demonstrated that the elevation of free ammonia levels to levels that can inactivate Ascaris eggs can be achieved through the urea addition. In this research, use of stored urine as an ammonia source for treatment of fecal products from UDDTs in Uganda was investigated. Mixtures of stored urine, fecal products from UDDTs, and wood ash were prepared, and treatment conditions (pH, temperature, ammonia concentration) were compared to the results of previous Ascaris inactivation studies to determine whether this strategy would be a feasible and effective treatment alternative. Results indicated that a volumetric mixture containing two parts stored urine and one part fecal products could provide 4-log1¬0 inactivation of Ascaris eggs after five months of indoor storage or after three months of outdoor storage. This strategy could improve the safety of recovered products while maintaining their agricultural value. Social acceptance of the treatment system appears to be possible with proper education efforts, and a cost comparison showed that this system may be more economically favorable than typical double-vault UDDTs.

The effects of electron beam (e-beam) irradiation and sanitizers in the reduction of Escherichia coli O157:H7 and Salmonella counts and attachment prevention on spinach was studied. Survival of these pathogens in spinach was observed at multiple times and temperatures. Inoculated spinach was examined by confocal microscopy to determine attachment sites and internalization of these pathogens. To determine the effectiveness of sanitizers in reducing pathogen numbers, inoculated spinach was treated with L-lactic acid, peroxyacetic acid, calcium hypochlorite, ozone, and chlorine dioxide. Inoculated spinach was exposed to e-beam irradiation and tested for counts of both pathogens immediately after irradiation treatment to determine bacterial reduction, and at 2 day intervals over 8 days to determine effects of ionizing irradiation on pathogen survival. Respiration rates were measured on spinach exposed to e-beam. The effectiveness of e-beam irradiation on the microbiological and sensory characteristics of spinach was studied. For spinach samples stored at 4�C and 10�C for 8 days, E. coli O157:H7 survived and grew significantly in samples stored at 21�C for 24 h. Confocal microscopy images provided valuable information on the attachment sites and internalization of the pathogens on spinach. The greatest reduction by a chemical sanitizer was 55�C L-lactic acid with a 2.7 log CFU/g reduction for E. coli O157:H7 and 2.3 log CFU/g reduction for Salmonella. Each dose of e-beam irradiation significantly reduced populations of both pathogens. Respiration rates of spinach increased as irradiation treatment doses increased. Total aerobic plate counts were reduced by 2.6 and 3.2 log CFU/g at 0.7 and 1.4 kGy, respectively. Lactic acid bacteria were reduced at both doses but grew slowly over the 35 day period. Yeasts and molds were not reduced in samples exposed to 0.7 kGy whereas 1.4 kGy had significantly reduced counts. Gas compositions for samples receiving 0.7 and 1.4 kGy were significantly different than controls. Irradiation did not affect the objective color or basic taste, aromatic or mouthfeel attributes of spinach. These results suggest that low dose e-beam irradiation may be a viable tool for reducing microbial populations or eliminating E. coli O157:H7 and Salmonella from spinach with minimal product damage.