Chaudhary, Priyanka Revansiddha (2017-05). Postharvest Treatment Effects on Health Promoting Properties and Flavonoid Genes of Grapefruit. Doctoral Dissertation.
Thesis
Certain naturally occurring compounds present in grapefruit have shown several health promoting properties such as anticancer, antioxidant, antimicrobial and cardioprotective. However, the levels of these naturally occurring compounds are influenced by several preharvest and postharvest factors. The primary objective of the current research is to determine the effects of different postharvest treatments on naturally occurring compounds present in grapefruit. In the first and second studies, effect of ethylene degreening on 'Star Ruby' and 'Rio Red' grapefruit natural compounds was investigated. Degreening helped to improve grapefruit color while maintaining the health promoting compounds. Significant influence of ethylene treatment was observed on flavonoids and furocoumarins. The third and fourth study examined the changes in 'Star Ruby' and 'Rio Red' grapefruit under cold storage and with low temperature conditioning treatment. Conditioning the fruits prior to cold storage reduced the incidence of chilling injury and conditioned fruits had similar or higher levels of health promoting compounds compared to fruits stored under cold storage without conditioning. However, results suggest that for short term storage of few weeks, storing fruits at 110C was better for retention of most naturally occurring compounds. The fifth study focused on use of modified atmosphere packaging (MAP) to maintain grapefruit quality and nutritional properties. Two MAP films, micro-perforated (modified oxygen, carbon dioxide and humidity levels) and macro-perforated (modified humidity only), were investigated for their influence on naturally occurring compounds and fruit quality under a prolonged storage period. MAP treatments did not have significant effect on ascorbic acid, limonoids and fruit quality parameters such as total soluble solids, acidity, fruit taste, decay and disorders. Based on our research, use of MAP films is recommended to maintain fruit quality and health promoting compounds. The sixth and seventh studies focused on variation in health promoting compounds, specifically, flavonoid pathway gene expression and volatile compounds present in 'Rio Red' grapefruit during fruit development and maturity. Overall expression of flavonoid pathway genes and related flavonoid content decreased as the fruits developed and matured, with the levels being highest in immature fruits harvested in June. Levels of limonene decreased as the fruits developed from June to April; while, nootkatone levels increased with fruit development and maturity. The eighth study investigated the effect of different ethylene concentrations on flavonoid pathway gene expression and related flavonoids in grapefruit. Significant effect of ethylene concentration was observed on flavonoids and furocoumarins as well as the genes involved in the flavonoid biosynthesis. Overall, significant influence of different postharvest treatments was observed on grapefruit health promoting compounds. We believe that this research will be helpful to the citrus industry to optimize the postharvest treatments in order to maximize their benefits in regards to fruit quality and nutritional value.
ETD Chair
Patil, Bhimanagouda Leonard Pike Inagural University Professor and Interim Head, Food Science and Technology
