Microwave and Traditional Cooking Methods: Effect of Cooking on Antioxidant Capacity and Phenolic Compounds Content of Seven Vegetables

Abstract

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.

Advanced preservation methods and nutrient retention in fruits and vegetables

“…Total phenolics were retained at only 58% in spinach microwaved at 800 W. 78 Total phenolics content was generally more degraded after boiling than microwaving. Microwaving resulted in higher levels of minerals in spinach as compared to cooking in boiling water for the following: ash, P, K, Ca, Mg, Na, Fe, Zn, Mn, Cu (all but C and Ni, which were same as boiling).…”

“…Picouet et al 65 found that the total phenolics content in apple purée was similar before and after microwaving. Carrot, cauliflower, pea, potato, spinach, Swiss chard and tomato were studied by Natella et al 78 and results were reported on a dry weight basis. Total phenolics were retained at 104-125% in all of the microwaved vegetables except peas (39% loss) and spinach (42% loss).…”

“…71 Microwave cooking at 800 W for 3-8 min did not result in a loss of total phenolics (100% or higher retention), whereas boiling resulted in significant losses. 78 Hot-air and/or microwave vacuum drying of cherry tomato halves resulted in both isomerization of trans to cis lycopene and oxidation of total lycopene, but these changes were reduced at lower temperature and microwave power levels. 74 Highest retention of trans-lycopene occurred when drying occurred at 1 W g −1 and 40 • C.…”

Effects of Various Cooking Methods on Content, Oxygen Radical Absorbance Capacity, and Bioaccessibility of Caffeoylquinic Acids in Ligularia fischeri (Ledeb.) Turcz, Gom-Chi

“…Farah et al, (Farah et al, 2005) reported that the amount of total 3-CQA and 3-CQA lactones from coffee decreased to less than 5.2% and 20%, respectively, of their maximal values at a longer time of roasting. Comparable findings reported that the total phenol content in various vegetables was shown to have a decreasing tendency after boiling (Natella et al, 2010). …”

Analysis of alkaloids (indole alkaloids, isoquinoline alkaloids, tropane alkaloids)

“…The total flavonoid, phenolic content, and antioxidant activity was reduced in cooked green beans at 100-120°C for 10-40 min ( Jiratanan and Liu, 2004). Microwave cooking may retain or decrease the phytochemical content in spinach, cauliflower, and peas as compared to boiling (Natella et al, 2010). Antioxidant activity of spinach, garlic, maize, onion, pepper, and Swiss chard was increased after microwave cooking ( Jim enez-Monreal et al, 2009).…”