الفهرس 
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Abstract
The present study was conducted to detect the ractopamine residue in 70 samples of imported frozen meat and liver, 35 samples from each type. Samples were collected from different frozen meat stores in Assiut city.
Statistical analytical results of RAC residues in the examined 35 frozen meat samples showed that the number of samples contained RAC were 14 samples, with minimum value of 0.05 ppb, maximum value of 19.66 ppb, and mean value of 2.6+1.63 ppb.
The data shown that there were 33 samples of imported frozen beef meat were accepted, with percent of 94.3% and the other 2 samples of meat unaccepted and above MRL of RAC which set by National Food Safety Authority NFSA, (2020) and CAC (2017), with percent of 5.7%.
According to US-FDA (2020) guideline which recommended that the maximum residual limit of RAC residue in meat is 3o ppb, so, the obtained results indicated that 100% of the examined imported frozen beef samples were accepted as they were within the permissible limit.
In addition, statistical analytical results of RAC residues in the examined frozen liver samples (35 samples); where the number of samples contained RAC residues were 14 samples, with minimum value of 0.05 ppb, maximum value of 20.95 ppb, and mean value of 3.76+1.81 ppb.
All samples of analyzed imported frozen liver were accepted with percent of 100% and their RAC residues were below MRL according to CAC (2017) and U. S. FDA (2020).
But, there was only one sample of liver above MRL according to National Food Safety Authority (NFSA, 2020), with percent of 3%; meanwhile the remained 34 samples were accepted with percent of 97% and below MRL set by NFSA.
Different cooking methods were applied on samples of meat and liver with known concentration of ractopamine (4 ppb) to detect the effect of heat treatment on RAC residues.
Meat samples were subjected to cook by boiling at 100°C for 120 min, grilling at 200ºC for 15 min, and microwave at 150-180°C for 8 min.
Liver samples were cooked by grilling at 170–200°C/6 min, frying at 230°C for 16 min, and microwave at 205°C for 8 min.
The cooked meat and liver samples were analyzed by RIDASCREEN® Ractopamin kit of ELIZA to detect RAC residue after different methods of heat treatment.
Reduction percent in cooked meat samples were 95.2% in case of boiling, 70.3% in case of grilling, and 100% in microwave cooking method.
Also, in cooked liver samples, reduction percent were 88.4% in case of grilling, 89.8% in case of frying, and 91.2% in microwave cooking method.