Summary, Siv REmberg

Institutt for plante- og miljøvitenskap

The scientific work of this thesis was conducted at the Department of Plant- and Environmental Sciences, the Norwegian University of Life Sciences (UMB), during the years 2000-2006. Part of the work was conducted in collaboration with Institute of Nutrition Research, University of Oslo, and Norwegian Food Research Institute (Matforsk AS).

The studies have been parts of two projects; “Bioactive components in fruits and vegetables and modulation of disease-related genes” (NFR132840/300, 2000-2002), and “Bioactive phytochemicals (flavonoids) in fruit and vegetables: storage, processing and rapid sensorbased analytical methods” (NFR146579/140, 2002-2006).

The aim of this work was mainly to investigate the influence of cold storage and storage atmosphere on quality related criteria in Norwegian grown fruits and berries. Fruit and berry cultivars grown at the UMB (59º 40’N) were used in several experiments studying the effects of cultivars and storage conditions on antioxidant activity and other quality related criteria. The quality related components measured in both berries and apples were; soluble solids, titratable acidity, sugar/acid ratio, pH, colour, firmness, L-ascorbic acid (vitamin C), antioxidant activity (Ferric Reducing Ability of Plasma (FRAP) and Oxygen Radical Absorbance Capacity (ORAC) assays) and phenolic compounds (chlorogenic acid, epicatechin, procyanidin B1 and B2, phloridzin, quercetin 3-galactoside and cyanidin 3-galactoside).

Different blueberry cultivars (‘Ama’, ‘Berkeley’, ‘Bluechip’, ‘Bluecrop’, ‘Bluejay’, ‘Bluetta’, ‘Duke’, ‘Earliblue’, ‘Goldtraube’, ‘Hardyblue’, ‘Heerma’, ‘Nui’, ‘Patriot’, ‘Puru’, ‘Putte’, ‘Reka’, ‘Spartan’, ‘Sunrise’ and ‘Toro’), red raspberry cultivars ‘Algonquin’, ‘Frosta’, ‘Glen Ample’, ‘Tambar’, ‘Tea’, ‘Tulameen’ and ‘Veten’) and black currant cultivars (Ben Alder’,’Ben Nevis’, ’Ben Tirran’, ’Ben Tron’, ’Hedda’, ’Håkon’ and ’Kristin’) were analysed for several quality related components. Large variations were observed between species and cultivars. Black currants had the highest antioxidant activity and L-ascorbic acid values. Large variation in antioxidant activity was observed within the blueberry cultivars, and smaller blueberries had higher antioxidant activity than larger fruits.

The blueberry cultivars ‘Bluecrop’, ‘Hardyblue’, ‘Patriot’, ‘Putte’ and ‘Aron’ were stored in normal and controlled atmosphere (10% O2 and 10% CO2) at 1 ºC and 8 ºC. Berries were analyzed for several quality related components both at harvest and after four weeks of storage. All blueberry cultivars showed differences regarding the quality related components measured. At harvest, ‘Putte’, ‘Aron’ and ‘Hardyblue’ had significantly higher antioxidant activity values than ‘Bluecrop’. During the four weeks of storage, the antioxidant activity decreased significantly. Less reduction in antioxidant activity was obtained in blueberries stored at 1 ºC and in normal atmosphere than at 8 ºC and controlled atmosphere.

As an approach towards a non-destructive and simple method to predict antioxidant activity in blueberry cultivars ‘Bluecrop’, ‘Hardyblue’, ‘Patriot’, ‘Putte’ and ‘Aron’), antioxidant activity was measured in berry samples, in addition to physical measurements on scanned images of equatorially cut berries. These results were put together to make a model for an approach to predict antioxidant activity in blueberries without destroying the berries. Four of the five blueberry cultivars fitted the model quite well, and berry weight and/or berry diameter were sufficient to predict the antioxidant activity in spherical fruits. It was also found that berry weight and antioxidant activity was negatively correlated; smaller blueberries had higher antioxidant activity than larger berries.

Antioxidant activity, phenolic compounds and other quality related analyses in the apple cultivars ‘Aroma’ and ‘Summerred’ were measured at harvest, and after ~20 and 17 weeks of storage, respectively. The apples were cold stored in normal and controlled atmosphere (’Aroma’; 1.5-2.5% O2 + 1.5-2.5% CO2, ’Summerred’; 1.0-1.5% O2 + 1.0-1.5% CO2) at 1 ºC for ’Aroma’, and 1 ºC and 5 ºC for ’Summerred’. After storage in cold store in air and controlled atmosphere, apples were stored for an additional week at 20 ºC, simulating shelflife. Both storage atmosphere and temperature had effects on many of the quality related components measured. ‘Summerred’ apples stored at 1 ºC and in controlled atmosphere kept better quality than apples stored at 5 ºC and normal atmosphere, with temperature of more importance than atmosphere. Chlorogenic acid was the dominating phenolic compound in both flesh and skin of ‘Summerred’ apples, and the concentration was affected by both storage temperature and –atmosphere, with highest content in apples stored at 1 ºC and normal atmosphere. The antioxidant activity and sum of flavonoids in ‘Summerred’ apples were not affected by temperature or atmosphere during storage. For ‘Aroma’ apples, the chlorogenic acid content increased, while quercetin 3-galactoside and antioxidant activity, measured as FRAP, decreased significantly during storage. Both antioxidant activity measured as ORAC, and the other phenolic compounds were relatively stable during storage, with no influence of storage atmosphere. All in all, storage at low temperatures and controlled atmosphere gave less reduction in the measured quality related components for ‘Aroma’ and ‘Summerred’, than storage at a higher temperature and normal atmosphere.

Remberg, S. F. 2006. ”Studies of antioxidant activity in fruits and berries. Effects of cultivars and postharvest conditions”. Norwegian University of Life Sciences, Ås, Norway. Doctor of philosophy (PhD) thesis 11, 9ISSN 1503-1667, ISBN 82-575-0705-.



Updated: 01.06.06
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