| Because of its unique color,flavor and texture,fried foods are becoming more and more popular,and many foods have adopted this processing method.Frying process was also adopted by traditional products such as roasted chicken to gain ideal color,and consumption of this kind of products was enormous.Studies have found that while giving unique color and flavor,due to the high processing temperature,many harmful substances,such as heterocyclic amines(HCAs),trans fatty acids(TFAs)as well as some small molecule lipid peroxides and other compounds were produced,which were very harmful to human health.During deep fat frying process,the quality of palm oil also changed,with the deterioration speed accelerated.Therefore,it had major practical significance to study the influence of deep fat frying processing on the content of harmful substances in processed foods,to analysis quality variation of frying oils.In this study,the contents of TFAs in Chinese traditional roast chicken products were determined.Chicken leg meat was chose as the material,palm oil was used as frying oil,to simulate the operation mode of the traditional chickens and study the effects of different processing conditions on the contents of TFAs and HCAs in the chicken legs.The quality changes and TFAs content of palm oil were also determined,and a comparison was also made between the frying oil and the palm oil only heated.The results were as follows:1.Water content of the chicken leg skin dropped dramaticly and the fat content increased after deep fat frying.However,fat content of the different batches in chicken leg skins showed a downward trend and the water content showed a rising trend when palm oil used continuously during deep fat frying.2.Influence of deep fat frying on the contents of TFAs in chicken legs:when palm oil was used to fry chicken leg meat to gain ideal color,C18:1 9t was the main TFA and small amounts of C16:1 9t was found in chicken leg skin,no other type of TFAs was detected.For chicken leg skin,continuous using time of palm oil and frying temperature had no significant influence on the content of C16:1 9t,C18:1 9t increased with the continuous using time of palm oil.For C18:1 9t in chicken leg skin,it showed a rising trend with the increase of continuous using time of palm oil,and there was no significant correlation between the deep fat frying temperature and trans fatty acids overall at the range of 160?200 ?.3.Influence of deep fat frying on the contents of HCAs in chicken legs:Norharman and Harman were the main HCAs in the chicken skin and meat and were detected in all samples.Trp-P-2 and AaC were also detected in the chicken skin at 180 ? and 200 ?.Both continuous using time and temperature had significant influence on the contents of HCAs.4.Study of variation of palm oil quality during flying chicken legs:The acid value of palm oil conformed to the sanitary standards of edible oil during the whole frying period;while carbonyl value reached 54.66 meq/kg at 160? after palm oil was used for 10 h,which exceeded the maximum limit of national standard.It was very near with the maximum limit after palm oil was used for 8 h at 180 ?,and went beyond the maximum limit at 200 ?.Therefore,it was better to choose 160 ? as the frying temperature and a frying time of less than 10 h when palm oil was used to fry to gain ideal color.Compared with the oil only heated without chicken legs,because of the added chicken,the deterioration speed of palm oil quality accelerated,in addition,variation of free fatty acids differs in the frying process. |
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