Novel intervention strategies such as food grade antimicrobials are used to enhance food safety. Nisin is a widely used naturally occurring antimicrobial effective against many pathogenic and spoilage microorganisms. However, its antimicrobial efficacy in food matrices is much reduced because of interactions with food components. Novel delivery systems may overcome this problem by protecting nisin in capsules and releasing it in a controlled manner. The overall goal of this research was to develop delivery systems of nisin to improve its long-term antimicrobial effectiveness. The first objective was to develop a low-cost method to extract nisin from a commercial preparation containing ~2.5% nisin. The best extraction yield was observed at 6 mg solids/mL 50% v/v ethanol. The nisin extract, after adjusting to 70% v/v ethanol, was dissolved with 2% zein (corn prolamins) and different amounts of Tween 20, glycerol, and thymol (another naturally occurring antimicrobial) for spray drying, a practical encapsulation method. Spray-dried capsules were characterized for release profiles of nisin at different pH conditions. Spray drying inlet temperature was first studied at 75 to 120°C, and the greatest sustained release of nisin was observed for capsules produced at 105°C, which was used in rest of this study. The impacts of Tween 20 and glycerol supplemented in spray-drying formulations were studied next. Addition of either 0.05% Tween 20 or glycerol in the spray-drying solution reduced the burst release of nisin at pH 6.0. Capsules with a higher amount of Tween 20 showed more complete release of nisin at pH 8.0, while glycerol had no apparent impact. The most sustained release of nisin at pH 6.0 was observed for capsules produced with both thymol and glycerol. Various capsules were then studied for their ability to inhibit the growth of Listeria monocytogenes at pH 6.0 during incubation at 30°C. Un-encapsulated nisin and thymol showed inhibition only for 12 h, while capsules with nisin and thymol containing either low or medium level of glycerol inhibited L. monocytogenes for >96 h. Our antimicrobial delivery systems, based on food grade ingredients and practical processes, have potential for practical application to enhance microbial safety and extend the shelf-life of foods.

<p dir="ltr">Historically, low-moisture foods were considered to have minimal microbial risks due to their inability to support the growth of microorganisms. However, many high-profile multistate outbreaks and recalls have drawn research and extension attention to low-moisture food safety. Contamination can occur at any stage in the supply chain, making food safety a shared responsibility among all actors from farm to fork. Fostering a positive food safety culture is essential for implementing food safety management systems, ensuring compliance, and driving the adoption of food safety-enhancing technologies, ultimately improving food safety performance across the industry. This dissertation explores the factors and best practices influencing cultural and managerial transformation in food safety and identifies challenges and needs in food safety training, education, and management, among various stakeholders in the low-moisture food industry. Chapters 2 and 3 focus on the California almond industry as a case study. Chapter 2 showcases the evolution of food safety management and culture in the almond industry following two major <i>Salmonella </i>outbreaks in the early 2000s, highlighting the role of repeated outbreaks and proactive industry leadership in driving the changes. It also examines the factors affecting the industry-wide adoption of food safety technologies. Chapter 3 evaluates current food safety training programs in almond processing facilities, detailing key advancements and barriers to effective training. Their user experiences with current food safety materials are also assessed to identify areas for improvement. Chapter 4 expands the assessment to the broader U.S. low-moisture food industry, investigating best practices and barriers in improving food safety culture, and assessing challenges and data gaps in continual food safety improvement. Moving further downstream in the supply chain, Chapter 5 shifts focus to retail food establishments, specifically Asian restaurants, exploring their handling practices of dried wood ear mushrooms, a culturally unique low-moisture food ingredient implicated in a multistate <i>Salmonella</i> outbreak in 2020 and multiple recalls. This chapter also uncovers the unique challenges to behavioral change within this niche audience, such as cultural practices and language barriers. Findings from these studies provide valuable insights into the dynamics and complexities of cultural transformation in the food system. They also inform the development and improvement of culturally tailored training and educational programs, and guide future research directions, continuously strengthening food safety culture and performance in the low-moisture food sector.</p>