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Title: COMPOST AS A SOIL SUPPLEMENT INCREASES THE LEVEL OF ANTIOXIDANT COMPOUNDS AND OXYGEN RADICAL ABSORBING CAPACITY IN STRAWBERRIES

Author
item Wang, Shiow
item LIN, HSIN-SHAN - TRANS WORLD INSTITUE OF T

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2003
Publication Date: 10/10/2003
Citation: Wang, S.Y., Lin, H. 2003. Compost as a soil supplement increases the level of antioxidant compounds and oxygen radical absorbing capacity in strawberries. Journal of Agricultural and Food Chemistry. 51:6844-6850.

Interpretive Summary: Strawberries are good sources of natural antioxidants. In addition to the usual nutrients such as vitamins and minerals, strawberries are also rich in anthocyanins, flavonoids and phenolic acids. Using compost as a soil supplement enhances vegetative growth, fruit productivity, carbohydrate and organic acid accumulation in strawberry. However, no information is available on the effect of compost as a soil supplement on antioxidant content and free radical scavenging capacity of strawberry fruit. We added compost to the soil to grow strawberry plants and studied its effect on antioxidant capacity of fruit. We found that strawberry fruit from plants grown under compost enrichment conditions had increased phytonutrient content and antioxidant capacity and that the use of compost could reduce the amount of fertilizer required for optimum strawberry plant growth. This research increased our knowledge on the impact of environmental factors on nutritional quality of fruit. This information will be useful to strawberry growers interested in selecting the best conditions for maximizing phytonutrient content and antioxidant capacity in strawberry fruit.

Technical Abstract: Compost as a soil supplement significantly enhanced ascorbic acid (AsA), glutathione (GSH), ratios of AsA/dehydroascorbic acid (DHAsA), and GSH/oxidized glutathione (GSSG) in fruit of two strawberry (Fragaria x ananassa Duch.) cultivars, Allstar and Honeoye. The peroxyl radical, as well as the superoxide radical, hydrogen peroxide, hydroxyl radical and singlet oxygen absorbance capacity in strawberries increased significantly with increasing fertilizer strength and compost use. The planting medium (compost) x fertilizer interaction for phenolics and flavonoids was significant. Fruit from plants grown in full strength fertilizer with 50% soil plus 50% compost and 100% compost yielded fruit with the highest levels of phenolics, flavonol, and anthocyanin content. A positive relationship between antioxidant activities and content of AsA, GSH, ratios of AsA/DHAsA and GSH/GSSG existed in fruit of both strawberry cultivars. Correlation coefficients for the content of antioxidant components versus antioxidant activity ranged from r =0.7706 for hydrogen peroxide versus GSH/GSSH in cv. Allstar to r =0.9832 for superoxide radical versus total flavonoids in cv. Allstar.