Nutrient composition and antioxidant activity of selected organically grown vegetables

Mah Liyun, (2012) Nutrient composition and antioxidant activity of selected organically grown vegetables. Universiti Malaysia Sabah. (Unpublished)

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Abstract

The objective of this work was to determine the nutrient composition and antioxidant activity of selected organically grown vegetables. The vegetable samples selected were romaine lettuce (Lactuca sativa L. var. longifolia), Chinese cabbage (Brassica rapa var. chinensis), baby white cabbage (Brassica campestris L. var. chinensis), mustard green (Brassica juncea var. crispifolia), and chayote shoot (Sechium edule). The nutrient compositions analyzed in the study include moisture, ash, protein, fat, total dietary fibre, crude fibre, carbohydrate, and energy content. Besides, the minerals and vitamins content of the vegetables were also determined. Antioxidant activity assays such as 2,2-diphenyl-l-picrylhydrazyl (DPPH), β-carotene bleaching assays, ferric reducing antioxidant power (FRAP), and oxygen radical absorbance capacity (ORAC) assay were carried out in the study. The total phenolic content of the vegetables was determined using Folin-Ciocalteu method. Most of the organically grown vegetables were found to have lower protein and fat content, but with higher dietary fibre and carbohydrate as compared to their conventional counterparts. However, no significant difference (p>0.05) in nutrient compositions was found between these types of vegetables except the energy content. Vitamins were found to be higher in organically grown vegetables as compared to non-organic vegetables. Significant difference (p<0.05) was found in ascorbic acid content between organic and conventional vegetables, but no significant differences (p>0.05) was found in β-carotene and α-tocopherol contents. Macro-minerals and trace elements were found to be higher in most organically grown vegetables as compared to their conventional counterparts. There was no significant difference (p>0.05) in macro-mineral contents among types of vegetables with the exception of Chinese cabbage and chayote shoot. No significant difference (p>0.05) was observed in trace mineral contents in the vegetables. The antioxidant activity of the organically grown vegetables was higher. Organically grown vegetables showed higher phenolic content than those non-organically grown vegetables. The total phenolic content was positively correlated with DPPH (r=0.7, p<0.01) and FRAP assay (r=0.7, p<0.01). The phenolic compounds identified by HPLC were syringic acid, catechin, epicatechin, naringin, quercetin, and kaempferol. The organically grown vegetables exhibited higher content of phenolic compounds than their conventional counterparts with the exception of baby white cabbage and mustard green. In general, organically grown vegetables are the better choice as compared to conventionally grown vegetables due to their higher content of primary and secondary nutrients and were free of health-threatening contaminants.

Item Type:Academic Exercise
Uncontrolled Keywords:nutrient composition, organically grown vegetable, health-threatening contaminant, HPLC
Subjects:T Technology > TX Home economics > Nutrition. Foods and food supply
Divisions:SCHOOL > School of Food Science and Nutrition
ID Code:7765
Deposited By:IR Admin
Deposited On:10 Dec 2013 15:37
Last Modified:10 Dec 2013 15:37

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