The present work is concerned with the determination of nitrate and nitrite
levels in some fresh vegetables and follow the effect of cooking and freezing in order
to decrease the content of nitrate and nitrite. Fresh vegetables were purshased from 3
governorates during 2000-2001 (cabbage, cauliflower ,carrot, spinach, squash, lettuce
cucumber, green bean, tomato, peppers, parsely, mushroom and potatoes) and the
nitrate and nitrite levels were determined. The results can be summarized as follow:- 1.The fresh vegetable samples (lettuce, spinach and cabbage) have higher nitrate
level ranging (200-1100),(70-980) and (65-820) mg I Kg, respectively, whereas
cauliflower, potatoes carrots and green bean have moderate nitrate level
ranging(53-680), (53-590), (100-501) and (35-280) mg I Kg, respectively, while
cucumber, mushroom, tomato, peppers and parsley have low nitrate level ranging
(18-125), (6-32), (16-42), (8-25) and (35-79) mg I Kg, respectively. 2.The fresh vegetable samples (cauliflower, carrots and spinach) have high nitrite
level ranging (0.0-30), (0.0-33) and (0.4-55) mg/Kg respectively, whereas cabbage,
squash, lettuce, cucumber, green bean, parsely and mushroom have moderate
nitrite level ranging (0.0-0.5), (0.0-0.7), (0.0-3),(0.0-0.5), (0.0-0.5), (0.0-0.7) and
(0.0-0.2) mg/kg, respectively. While tomato and peppers have no nitrite level. 3.The cooking process reduced the nitrate level in vegetables. The reduction was
found in cauliflower (86 - 90%), spinah (77 - 87%), carrots (66 - 81%), cabbage
(60 - 78%) and green bean (58 - 71%). 4.Also, the cooking process reduced the nitrite level in vegetables. The reduction was
found in cabbage (80 - 100%), cauliflower, carrots and spinach (90 - 100%) and
green bean (87 -100%). 5.The nitrate and nitrite levels didn't change in case of cabbage and green bean
during frozen storage for up to 5 weeks, then a trend toward decreased nitrate level
and at the same time, an increase in nitrite level was observed from the nineth
week to eleventh week, whereas, the nitrate and nitrite levels didn't change in case
of cauliflower, carrot and spinach for up to 3 weeks then a trend toward decreased
nitrate level and at the same time, an increase in nitrite level was observed from the
fifth week to the eleventh week. So, the cooking process is important in order to
decrease the nitrate and nitrite contents in vegetables, while it was found that the
freezing process is related to the number of weeks, so it is recommended that the
freezing process didn't exceed 3 weeks in case of cauliflower, carrot and spinach,
and 5 weeks in case of cabbage and green bean due to the decrease in nitrate
content followed by an increase in nitrite content after these periods of freezing.