Monday, August 20, 2007
Antioxidant Properties of Vegetables, Spices, Herbs, and Dressings - A Study
Fruits and vegetables contain polyphenols, compounds that reduce oxidative stress and prevent chronic diseases. The antioxidant properties of polyphenols are responsible for their anticancer, antiviral, and anti-inflammatory properties and can prevent capillary fragility and platelet aggregation. The authors report the phenolic, flavonoid, and flavanol content as well as the antioxidant capacity of a number of fresh vegetables, herbs, and spices consumed in Central Italy. The authors also studied these same parameters in cooked vegetables, salads, and common Italian salad dressings.
The authors obtained and tested 27 different types of vegetables, 15 different types of herbs, six spices, and 10 dressings. Phenolic compounds were assayed according to the Folin-Ciocalteu method, and total phenolic content was expressed as caffeic acid equivalents in mg/g fresh vegetable. Flavonoids were determined by the method of Eberhardt et al1 and flavanols according to that of Arnous.2 Antioxidant capacity was measured using the oxygen radical absorbance capacity (ORAC) method. Using a multiple linear regression model, the authors provided significant evidence that ORAC values are strictly dependent on the total phenols (P = 0.048) and flavanols (P = 0.001), and that the contribution to ORAC of the flavonoids is not significant (P = 0.156).
Among the vegetables showing the highest phenolic content were the artichoke, beetroot, cabbage, broccoli, red chicory, red chili, and yellow pepper. The authors report that different cultivars cause vegetables of the same family to possess significant different phenolic, flavanol, and ORAC values.
The authors measured the loss of phenolics and antioxidant capacity in vegetables that need to be cooked. Steamed vegetables retained about 80% of the phenolic and ORAC values of raw vegetables; boiled vegetables retained only 30% of antioxidants. The preferred cooking process for vegetables should be steaming at the mildest temperature and for the least possible time to protect phenolics and vitamins.
Among the aromatic herbs receiving high ORAC values were garden sage, marjoram, rosemary, and garden thyme. Their values are many times greater than those of the vegetables studied. The authors showed that introducing aromatic herbs into salads markedly increases the phenolic and ORAC values of the whole salad. Lemon balm and marjoram at a concentration of 1.5% w/w increased by 150% and 200%, respectively, the antioxidant capacity of a salad portion.
Among the selected spices, cumin revealed the highest ORAC value, although its phenolic and flavonoid content were not the highest. Fresh ginger also made a significant contribution to the antioxidant capacity.
Noting the importance of the use of salad seasonings, the authors state that extra-virgin olive oils, carefully produced using freshly gathered olives at the right degree of maturation, should be the principal condiment for their content of phenolic compounds, which, because of their marked antioxidant capacity, protect the cardiovascular system.The authors stress the importance of educating consumers on the benefits of varying vegetable consumption, choosing those that have the highest antioxidant capacity to promote a healthy diet, and the need to introduce aromatic herbs as a seasoning supplement in the diet of every age group. Results of this analysis provide "a simple and compelling tool for nutrition professionals to guide family vegetable consumption" and "can be used in public health campaigns to stimulate the consumption of vegetables able to provide significant health protection in order to prevent chronic diseases."
SOURCE
The authors obtained and tested 27 different types of vegetables, 15 different types of herbs, six spices, and 10 dressings. Phenolic compounds were assayed according to the Folin-Ciocalteu method, and total phenolic content was expressed as caffeic acid equivalents in mg/g fresh vegetable. Flavonoids were determined by the method of Eberhardt et al1 and flavanols according to that of Arnous.2 Antioxidant capacity was measured using the oxygen radical absorbance capacity (ORAC) method. Using a multiple linear regression model, the authors provided significant evidence that ORAC values are strictly dependent on the total phenols (P = 0.048) and flavanols (P = 0.001), and that the contribution to ORAC of the flavonoids is not significant (P = 0.156).
Among the vegetables showing the highest phenolic content were the artichoke, beetroot, cabbage, broccoli, red chicory, red chili, and yellow pepper. The authors report that different cultivars cause vegetables of the same family to possess significant different phenolic, flavanol, and ORAC values.
The authors measured the loss of phenolics and antioxidant capacity in vegetables that need to be cooked. Steamed vegetables retained about 80% of the phenolic and ORAC values of raw vegetables; boiled vegetables retained only 30% of antioxidants. The preferred cooking process for vegetables should be steaming at the mildest temperature and for the least possible time to protect phenolics and vitamins.
Among the aromatic herbs receiving high ORAC values were garden sage, marjoram, rosemary, and garden thyme. Their values are many times greater than those of the vegetables studied. The authors showed that introducing aromatic herbs into salads markedly increases the phenolic and ORAC values of the whole salad. Lemon balm and marjoram at a concentration of 1.5% w/w increased by 150% and 200%, respectively, the antioxidant capacity of a salad portion.
Among the selected spices, cumin revealed the highest ORAC value, although its phenolic and flavonoid content were not the highest. Fresh ginger also made a significant contribution to the antioxidant capacity.
Noting the importance of the use of salad seasonings, the authors state that extra-virgin olive oils, carefully produced using freshly gathered olives at the right degree of maturation, should be the principal condiment for their content of phenolic compounds, which, because of their marked antioxidant capacity, protect the cardiovascular system.The authors stress the importance of educating consumers on the benefits of varying vegetable consumption, choosing those that have the highest antioxidant capacity to promote a healthy diet, and the need to introduce aromatic herbs as a seasoning supplement in the diet of every age group. Results of this analysis provide "a simple and compelling tool for nutrition professionals to guide family vegetable consumption" and "can be used in public health campaigns to stimulate the consumption of vegetables able to provide significant health protection in order to prevent chronic diseases."
SOURCE
Labels: Anti-oxidant, health food, phenols, salad, study
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