Graduate Thesis Or Dissertation
 

Effects of refrigeration storage and processing technologies on the bioactive compounds and antioxidant capacities of blackberries ('Marion' and 'Evergreen')

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/cv43p076q

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  • The objective of this project was to investigate the effects of refrigeration storage and processing technologies on the quality and nutraceutical benefit of blackberries. 'Marion' and 'Evergreen', the two major blackberry varieties in Oregon, were evaluated in this study. For refrigeration storage, fresh fruit were packed in clam-shell containers right after harvest and stored at 2.0 ± 0.2 °C and 95 ± 2% relative humidity for 9 or 7 days for 'Marion' and 'Evergreen', respectively. For evaluating processing effect, fresh fruit were individually quick frozen at -23 °C and then subjected to different processing treatments including freeze drying, hot-air drying, canning-in-water, canning-in-20° Brix sucrose syrup, and making into jam. Processed berry products were stored at room temperature at 25 ± 2 °C and 30 ± 2% relative humidity for up to 6 months. Physicochemical properties including pH, titratable acidity (TA), total soluble solids (TSS) and moisture content (MC), bioactive compounds including total phenolics (TPC) and total monomeric anthocyanins (ACY), and antioxidant capacities evaluated as radical scavenging activity (RSA), oxygen radical absorbance capacity (ORAC) and ferric reducing ability of plasma (FRAP) were monitored in fresh blackberries and processed blackberry products right after processing and during storage. Frozen fruit were used as a control for evaluating processing effects. TA reduced by 36.8% and 46.2% in 'Marion' and 'Evergreen', respectively (P<0.05) at the end of refrigeration storage compared to that at day 0. TPC and ACY decreased significantly in both varieties. ORAC declined by 20% and FRAP increased by 18.75%, respectively in 'Evergreen' (P<0.05) while remained stable in 'Marion' during refrigeration storage. Right after processing, TA in all the processed 'Marion' products lost significantly, while TSS increased in dried blackberries and blackberry jams of both varieties. Freeze drying increased TPC by 27% and 21% in 'Marion' and 'Evergreen', respectively (P<0.05), whereas hot-air drying reduced ACY by 56% in 'Marion' and 84% in 'Evergreen' (P<0.05). The content of measured bioactive compounds lost 31% to 70% (P<0.05) in canned products except TPC in 'Marion' canned-in-water. ORAC and FRAP lost 21%-61% in canned 'Marion' (P<0.05). RSA increased in canning-in-water fruit while decreased in canning-in-sucrose syrup for both varieties. Making blackberries to jams resulted in extensive losses of bioactive compounds and antioxidant capacity in both varieties. Over 6–month storage, TA deceased 9% and 12% in 'Marion' and 'Evergreen' jams, respectively (P<0.05). The significant losses of ACY in hot-air dried, canned blackberries and blackberry jams, and RSA in frozen, dried and canned blackberries, ORAC in hot-air dried and canned-in-water blackberries of both varieties were also observed. Two varieties of blackberries varied in physicochemical properties, content of bioactive compounds and antioxidant capacities, with higher values of TA, MC, TPC, ACY, RSA and FRAP observed in 'Marion' than those in 'Evergreen'.
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