الفهرس 
Materials and mithodsOnly 14 pages are availabe for public view
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Abstract
Nitrates are present naturally in soil, water and plant materials as a
consequence of nitrogen fixation . In addition, the wide use of nitrogenbased
fertilizer in agriculture contributes to the total nitrate present in the
soil and water. Nitrate is therefore likely to be present in most things we
eat or drink.
The determination of nitrate and nitrite in foodstuffs has become
increasingly important because of concern over excessive human dietary
intake of these species. The toxicity of nitrite, especially in relation to
nitrosamine production, has been well stablished. and whilest nitrate not
very toxic, their ready to conversion into nitrite means that levels of nitrate must be carfully monitored.
Subsequently, this investigation was designed to demonstrate the
followin points : * Effect of location of market on the nitrite, nitrate and nitrosamine compounds of some selected fresh vegetables, fruits, meat and meat
products as well as some types of fish and baby foods. * Effect of storage conditions (at room temperature, refrigeration and
freezing) on N(h and NOJ levels of some vegetables.
* Effect of cooking on N02 and N03 concentration of some selected
vegetables.
* Effect of soaking in N~ and NOJ solutions with different
concentrations for different time on the N~ and N03 residues of old and
young beef meats. Effect of different cooking methods (boiling in water, frying and grilling) on the NCh and N03 residues of meats. * Evaluation of ascorbic acid and ec-tocopherol as inhibitors ofNnitrosamine
formation in cured meats.
The obtained results could be summarized as follow : 1. Nitrite2 nitrate and N-nitrosamine compounds in foods as affected by
location of market: A. Data indicated that, leafy vegetables had the highest N03 content comparing with fruit vegetables, pulses and tuber vegetables.
However, some root crops such as beet roots and radish roots
contained substantial levels of NOJ. Nitrite concentrations in
most vegetables under investigation are low of little concern,
provided vegetables consumed within the normal shelf life. B. Soybean was found to contain a higher amounts ofN~ and N03 being 7.55 and 9.87 ppm, respectively compared with mung beans
However, NDMA was only the nitrosamine compound detected in
both types of legumes, and mung beans was found to contain a
levels (0.16 ppm) compared with soybean (0.54 ppm).C. Data indicated also that strawberry contained a higher levels of
N(h , N03 and NDEA compared with banana and orange.D. Five samples of baby foods were analyzed for N(h,N03 and
N-nitrosamine compounds. Results showed that samples contain
rice had a higher concentrations of N02, N03 and NDMA followed by samples contained meats, wheat, vegetables and
apples. E. Veal meat had the lowest levels of N~ compared with other
types of meats. However, beefmeat contained higher concentrations
ofN03, while Buffalo and Lamb meats were found to contain the lowest levels. The highest levels of total nitrosaminecompounds were observed in Veal meat (116.89ppm) followed by Lamb meat (88.00 ppm) and Buffalo meat (34.93 ppm). F. Luncheon meat had the highest levels ofNOz (112.78 ppm)
followed by Bastirma (75.13 ppm), Sausage (34.45 ppm)
and Frankfurter (22.26 ppm). While, the highest values of N03 were found in Bastirma (131.89 ppm) and the lowest
levels were in Frankfurters (12.29 ppm). On the othet hand,
Bastirma had the highest levels of total N - nitrosamine
compounds (395.43 ppm), while Luncheon meat and Frankfurters were found to contain a moderate contents of
total N-nitrosamine compounds.
G. Data revealed that Karmout fish contained a higher NCh
(3.49 ppm) followed by Bolti (2.44 ppm), Denis (2.09ppm)
and Bayad (2.00 ppm) compared with other types offish.
However, Macaroni, Baury , Denis , Bayad and Karmout
contained a higher levels of N03 , it ranged from
(10.21 ppm) in Macaroni to (14.94 ppm) in Karmout. Data
indicated also the highest levels of total N-nitrosamine
compounds was observed in Macaroni fish (157.02 ppm) followed by Baury ~Bolti, and Sardin. Moreover ~the lowest
levels were found in Denis (0.48 ppm).
H. Generally ~ the location of market makedly affect the NOl.,
N03 and N-nitrosamine content in previous studied samples.
2.Inhibition of nitrite and nitrate in vegetables : * Effect of Storage:
The storage of fresh vegetables at room temperature, under
cooling and frozen state reduced the nitrate and increased the
nitrite contents of most vegetables under investigation.
* Effect of cooking:
Cooking process reduced the total NOl content between (8.07 %) in green beans to (99.50 %) in carrots. It could be
noticed also NO] contents of raw vegetables reduced signi -
ficantly in all tested vegetables as affected by cooking. The
greatest reduction were found in leafy vegetables such as cabbage (77.64 %), spinach (90.04 %) and jew’s mallow
(94.76 %), followed by green beans (73.76 %), carrots (71.27 %), squash (62.54 %), potatoes (60.54 %), okra
(52.78 %) and peas (33.32 %).
3.Effect of soaking on the N02 and NO] residues in meats : Soaking of yuong and old beef meats in N02 and NO] solutions with different concentrations ranging from 50 to 500 ppm for 30 min and 24 hr caused an increases in N02 and N03 contents, 4. Inhibition of N~” NO) and N-nitrosamine compounds in cured meats : * Effect of cooking :
The effect of different cooking methods (boiling in water, frying and
grilling) was carried out using the previous soaked samples in No” and
NO) which contain a higher levels of NOz and NOJ . Data indicated that
NOz and NO), reduced with different levels as affected by cooking
methods. The higher reduction in NOz and NO] was noticed in old and
young beef meats as affected by grilling * Effect of oc:-tocopheroland ascorbic acid : The obtained results indicated that the reduction rate of Nnitrosamine formation in dry and brine-cured beef and buffalo meats
increased gradually as the levels of oc:-tocopherol or ascorbic acid
increased. The higher reduction was observed in buffalo meats than beef
meats. Moreover, ascorbic acid had a higher effect on the N-nitrosamine
formation than oc:-tocopherol.
* Effect of cooking on N-nitrosamin formation in oc-tocopherol and
ascorbic acid - treated meats:
Samples of old and young meats (beef and buffalo) treated by octocopherol
and ascorbic acid with different levels either in dry or brine
curing were cooked using different methods (boiling in water, frying and
grilling). Results showed that all different methods of cooking reduced
No” and N-nitrosamine formation with different levels and the reduction
rate was higher in old meats than young meats. from the afformentioned results, it could be conclded that octocopherol
and ascorbic acid could be used as an inhibitors of Nnitrosamineformation
in cured meats. In view of the above mentioned results regarding the risk to human health posed by N-nitrosamine compounds it is prodent to attempt to
reduce exposure. Examples of the ways in which this might be achieved
are : * By reducing the use of N~ to minimumlevel necessary to prevent
growth of Clostridium botulinum.
* Ensuring that the N02 is distributed as evenly as possible. * Avoiding the use of concentrated curing preparations in which N-nitrosamines can be formed before used. * Adding oc - tocopherol or ascorbic acid as an inhibitors of Nnitrosamine formation.