EFFECT OF THERMAL PROCESSING ON TOTAL PHENOLS, MYRICETIN AND QUERCETIN, VITAMIN C AND ANTIOXIDANT ACTIVITY OF SOME VEGETABLES | ||
| Journal of Food and Dairy Sciences | ||
| Article 2, Volume 30, Issue 11, November 2005, Pages 6855-6868 PDF (4.13 M) | ||
| Document Type: Original Article | ||
| DOI: 10.21608/jfds.2005.238018 | ||
| Author | ||
| Sawsan Y. EI-Faham | ||
| Food Technology Dept., National Research Center Dokki, Cairo, Egypt | ||
| Abstract | ||
| The contents of total phenols and some flavonoids, vitamin C and antioxidant activity in freeze dried tissues of onion, cabbage, artichoke and sweet pepper in relation to the effect of two thermal processing treatments i.e. blanching and microwaving were studied. Vegetables were freeze dried after processing (more than the fresh ones) before hydrolyzed and extraction. Total phenols content in edible parts, was higher in sweet pepper but lower in onion. Thermal processing induced lowering effect on total phenols (mg I 100g) in onion, however, the effect by blanching exceeded those resulted from microwaving thermal treatment. Effects on these compounds but towards decrease were observed with microwave treatment in pepper and artichoke but in cabbage was increased. Meanwhile, blanching caused an increase in total phenols of sweet pepper as well as cabbage while in artichoke were slightly affected. The level of myricetin in cabbage exceeded those in onion and not detected in artichoke and pepper. Conceming the level of quercetin, it was obviously shown that sweet pepper the superior followed by artichoke and onion was contained the leowest quantities, however, it was not detected in cabbage leaves. Myriceten was sharply but negatively affected in cabbage leaves to be undetected by blanching and slightly by microwave treatment. On yellow onion tissues, this active material was quietly reduced by blanching and reversely responded by microwave treatment. The quercetin in artichoke as well as sweet pepper increased pronouncedly by blanching and also by microwave treatment but with a lower degree. Sweet pepper fruits characterized by the highest percentages of vitamin C followed by that in the leaves of cabbage and the lowest content was in bulbs of onion. The highest effect of heat treatment was in onion followed by pepper and no response with cabbage tissues. Blanching tissues at boiling water for 5 min. decreased pronouncedly the level of vitamin C by 33.91, 53.85 and 2.70 % for pepper, onion and cabbage, respectively, while exposure to microwave thermal treatment decreased Vitamin C by 53.04 , and 69.23 % in sweet pepper and onion, respectively, while. cabbage tissues did not show any response with this treatment. The antioxidants activity were higher in pepper than the other tested veget.-:bles. This activity raised in all vegetables except pepper by blanching and microwave. | ||
| Keywords | ||
| Total phenols; Myricetin; Quercetin; Vitamin C; Antioxidant activity; Thermal processing; Blanching • Microwave; Onion; Artichoke; Cabbage; Sweet pepper. INTRODUCTION | ||
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