Effect of heating on onion (Allium cepa L.) antiplatelet activity, pyruvate content and pungency sensory perception

CAVAGNARO, P. F., SANCE M. M., GALMARINI, C. R.

FOOD SCIENCE AND TECHNOLOGY INTERNATIONAL

SAGE

Año: 2007 vol. 13

1082-0132

Onion, in its raw form, is recognized as an antiplatelet agent that may contribute to the prevention of cardiovascular disease. In raw onions, the content of pyruvate, is significantly correlated with antiplatelet activity (AA) and the sensory perception of pungency. However, onion is generally cooked before consumption. Herein, we examined the effect of heating -using different boiling intensities- on the in vitro antiaggregatory activity (IVAA), the pyruvate concentration and the flavor (pungency) of crushed-onion samples. In general, heating was detrimental for onion AA. Boiling for 3 min had no significant effect on platelet aggregation, as compared to raw onion. Heating for > 6 min completely suppressed IVAA, whereas samples boiled for > 20 min had proaggregatory effects. Significant differences in AA were found between the blood donors. Pyruvate content was not reduced after 30 min boiling. Pungency ratings decreased with the intensity of the heat treatment. Strong significant positive correlations were found between IVAA and pungency, but not between pyruvate and the former two variables. Our results suggest that: 1) in order to obtain the maximum health benefits onions should be eaten raw or moderately cooked, 2) extensive heating may result in pro-aggregatory effects, 3) pyruvate is not a good indicator of AA in cooked onions, 4) the decrease in IVAA and pungency during onion cooking may be due to degradation of sulfur compounds (e.g. thiosulfinates) which are, likely, less tolerant than pyruvate to the high temperatures.