The effect of microwave, boiling and pressure cooking on total antioxidant capacity and total phenolics content of seven vegetables were studied. Total phenolics in raw and cooked vegetables were determined by the Folin–Ciocalteu method, whereas the total antioxidant capacity of vegetables extracts was evaluated using the Crocin method. After boiling, four out of seven vegetables (cauliflower, peas, spinach and Swiss chard) showed a significant decrease in their total phenolic content (P < 0.05). No decrease or a smaller decrease was observed for these four vegetables (P < 0.05) after pressure cooking and/or microwaving than after boiling. The total antioxidant capacity of potato and Swiss chard was not significantly affected by cooking procedures, whereas it decreased for spinach and peas, and it increased for tomato and carrots (P < 0.05). In addition, there was a statistically significant correlation between total phenolic content and total antioxidant capacity in cooked and uncooked vegetables, but the strength of the correlation increased when separating carotenoid‐poor from carotenoid‐rich vegetables.
PRACTICAL APPLICATIONS
All guidelines for a healthy nutrition include recommendation for increasing the consumption of fruit and vegetables also because of their phenolic compounds content and antioxidant capacity.
However, all studies correlating antioxidants consumption and health benefits relate food consumption studies with antioxidant capacity of foods, neglecting to consider the chemical composition changes that may occur during cooking. This study provides data in order to better understand the implication on the total antioxidant capacity of foods due to different cooking approaches.
Moderate wine consumption has been shown to lower cardiovascular risk. One of the mechanisms could involve the control of postprandial hyperlipaemia, a well-defined risk factor for atherosclerosis, reasonably by reducing the absorption of lipid oxidised species from the meal. The objective of the present study was to investigate whether wine consumption with the meal is able to reduce the postprandial increase in plasma lipid hydroperoxides and cholesterol oxidation products, in human subjects. In two different study sessions, twelve healthy volunteers consumed the same test meal rich in oxidised and oxidisable lipids (a double cheeseburger), with 300 ml of water (control) or with 300 ml of red wine (wine). The postprandial plasma concentration of cholesterol oxidation products was measured by GC -MS. The control meal induced a significant increase in the plasma concentration of lipid hydroperoxides and of two cholesterol oxidation products, 7-b-hydroxycholesterol and 7-ketocholesterol. The postprandial increase in lipid hydroperoxides and cholesterol oxidation products was fully prevented by wine when consumed with the meal. In conclusion, the present study provides evidence that consumption of wine with the meal could prevent the postprandial increase in plasma cholesterol oxidation products.
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