Lactic acid fermentation and phytochemical synergies for food safety and human health applications
Type 2 diabetes, hypertension and Helicobacter pylori -linked ulcer are among the important global health challenges. Healthier food and ingredient design for addressing above health challenges could be combined with traditional drug therapies for disease management. Listeria monocytogenes, Staphylococcus aureus, Vibrio parahaemolyticus and Escherichia coli are food-borne pathogens associated with infectious disease outbreaks. However, the development of antimicrobial resistance and the limited success of relatively narrow spectrum of antimicrobials, results in microbial contamination of food and poses public health and economic challenge.
Therefore, the aim of this dissertation was to develop metabolic strategies for designing milk and soymilk fermented diets and ingredients enriched in phenolic phytochemicals for managing type 2 diabetes, hypertension, ulcer and controlling food-borne pathogens. This was investigated through understanding the in vitro inhibitory potential of hyperglycemia and hypertension linked enzymes as well as critical metabolic pathways contributing to the cellular breakdown of bacterial pathogens.
Based on structure-function rationale, the potential antioxidant, anti-hyperglycemia and anti-hypertention functionality of herb and fruit extracts, fruit enriched dairy and soy yogurts and herb and fruit enriched cheeses were investigated. Results indicated that specific extract profiles had high anti-hyperglycemia and anti-hypertension potential which generally corresponded to total phenolic content and free radical scavenging-linked antioxidant activity. Further it was observed that lactic acid bacterial fermented milk and soymilk have potential for hyperglycemia and hypertension management, which is enhanced with phenolic phytochemical enrichment. However, it was determined that soymilk fermented products had superior potential for hypertension management and further that the anti-hypertension potential of fermented milk depended strongly on the lactic acid produced during fermentation. Furthermore these fermented extracts had potential to inhibit L. monocytogenes, S. aureus , V. parahaemolyticus, and ulcer related H. pylori. Results also indicated that oregano-cranberry synergies with sodium lactate had the best potential for L. monocytogenes inhibition in broth and cooked meat substrate and that this inhibition recovered with the addition of proline. Finally the mode of action of cranberry phenolics and L-lactic acid was investigated in L. monocytogenes and E. coli based on the concept of disruption of critical proline-linked pentose phosphate pathway and the role of this pathway was confirmed.