Lactic Acid Bacteria Mediated Phenolic Bioactive Modulation From Fruit Systems For Health Benefits

Abstract

Chronic oxidation linked diseases are on a rise and are one of the leading causes of death globally. Epidemiological evidence increasingly points towards consumption of fruits and vegetables as a preventive way to manage early stages of chronic oxidation linked diseases. Oxidation linked diseases are caused by excessive reactive oxygen species (ROS) generated by a disruption in cellular antioxidant homeostasis due to an overload of calories combined with stress, no excerise and a diet low in antioxidants. Phenolic compounds can not only act as antioxidants but also stimulate the activities of antioxidants enzyme through protective pathways which can help modulate cellular protection. The aim of this dissertation was to use probiotic fermentation to enhance the phenolic and antioxidant compounds in fruit systems which can form the basis of functional food design. The potential of these food systems for disease prevention was investigated in eukaryotic systems through understanding the role of critical metabolic pathways involed in prevention of oxidation linked chronic diseases. Based on structure-function rationale, antioxidant, anti-hyperglycemia and anti-hypertensive potential of phenolic compounds in tea and the effect of extraction time and different degrees of fermentation were investigated in in vitro models. Results indicated that the most fermented teas and a longer extraction time had the highest potential. Further these extracts also had higher H. pylori inhibition potential. Probiotic fermentation of fruit juices with L. helveticus was used to mobilize phenolics and improve biological functionality by maintaining a consistent phytochemical profile. Results indicated that total phenolic and antioxidant potential decreased with feremnetation. However α-glucosidase inhibitory activity and H. pylori inhibitory potential increased with fermentation. Investigation into the mechanism of H. pylori inhibition with fermented cherry extracts revealed inhibition of proline dehydrogenase as the likely mode of action. The potential of fermented apple extracts was further investigated as a phytochemical elicitor in eliciting phenolic and antioxidant response in germinating fava bean. The results indicated a stimulation of phenolic and antioxidant response likely through the stimulation of carbon flux through glycolytic pathways. In yeast, fermented apple extracts accelerated cell death in the presence of peroxide stress in pretreatment model whereas it provided protection against oxidative stress and prevented cell death in concurrent model. Chitosan oligosachharide treatment was investigated as a potential replacement of cancer causing diphenylamine treatment for scald reduction in Cortland apples. Although the treatment did not have any effect on scald reduction, it provides better protection in storage by stimulating phenolic and antioxidant response which related to better health relevant functionality.

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