Technology and raw material quality to underpin the Irish fresh-cut fruit industry

The objective of this thesis was to contribute to improving the quality of fresh-cut fruits by identifying how raw material use, processing, packaging and storage might be optimised. Effects of intrinsic and extrinsic factor variables on the quality, microbiology and phytochemical content were determined. Following comprehensive quality evaluations, principal component analysis (PCA) was employed, and the biplots generated were effective in characterising patterns of deterioration and in tracking differences in quality in terms of the rate and extent of change. Ripeness stage/ physiological age, geographical origin, cut size and packaging type had large effects on quality (p<0.05) as did storage temperature and time (p<0.01). There were significant effects of controlled and modified atmospheres on quality (p<0.05), but little effect on microbial growth or phytochemical (total phenolic, total carotenoid, total antioxidant activity) content (p>0.05). In general, product modified atmosphere (PMA) packs displayed a steadier rate of quality loss with more consistent end-product quality. A CA of 5%O2+5%CO2 was best at maintaining fresh-cut pineapple and cantaloupe melon quality, while a CA of 97%N2+3%O2 was best for fresh-cut kiwifruit. Exposure to sub-optimal atmospheres resulted in physiological disorders such as discolouration, loss of firmness and off-odour development. Cut size (p<0.05) and storage time (p<0.01) had large effects on volatile aromatic compounds (VACs). VAC changes involved increased and/or decreased concentrations of existing volatiles rather than the emergence of new compounds. A total of 18, 16 and 20 odour-active compounds were detected and tentatively identified in the headspace of fresh-cut pineapple, cantaloupe melon and kiwifruit respectively. Based on PCA interpretation, the post cutting aroma life of fresh-cut pineapple and kiwifruit was adequate over 7 days for large cut pieces, and limited to less than 7 Days for smaller cut pieces. In contrast, fresh-cut melon aroma was limited to 4 and 7 Days for small and large cut pieces respectively. This was largely due to the presence of fermentative-like off-odours, which were more pronounced for smaller cut pieces. The effects of intrinsic and extrinsic variables on the respiration rate (RCO2) of a number of fresh-cut fruits were determined. In general, the RCO2 increased initially, peaked, and declined gradually to equilibrium within 24h. The high initial rate was highly dependent on fruit type, physiological age and processing (p<0.05). Using data for fresh-cut pineapple, a mathematical model based on exponential decay was developed in order to predict the RCO2 over time. From this, the oxygen and carbon dioxide transmission rates required in package design were estimated and validated. The model parameters were found to be a good fit with experimental data and could be successfully applied to other fresh-cut fruits to aid in product-package compatibility.