The Formation Of Heterocyclic Amines And Benzo(a)pyrene In Thermal Field Dried Beef Based On Xylose-Cysteine Reaction Model At 110?

Roasting is one of the main technologies of meat processing.The roasted beef are popular at home and abroad because of their unique flavor,which arose from flavor substances.But under the high temperature heating conditions,heterocyclic amines,benzo(a)pyrene and free radicals also have been produced,and have become the major factor in increasing the incidence rate of various cancers.In this study,the Maillard reactions model systems of xylose-cysteine at 110? was established and determined their optimal ratio through factorial test.The reaction solution of the optimal group was used to prepare thermal field dried beef.This paper tended to compare the effects of thermal field drying technology and traditional roasting technology,reheating and quick-freezing to HCAs,BaP and free radicals of thermal field dried beef and traditional roasted beef.The specific research contents are as follows:1.Effects of dry-curing on the quality of roast beef at 4?The longest back muscle of beef was used as test material and set seven test groups:control group at 4?,1%added salt for dry-curing 4 and 6 h,2.5%added salt for dry-curing 3 and 5 h,4%added salt for dry-curing 2 and 4 h.Water contents?pH value,salt contents,dry-curing loss rate and total number of colonies as physical and chemical indicators,and salty taste,spicy taste,juiciness,off-flavor and comprehensive evaluation as sensory indicators were determined.The results indicated that the water contents of diy-cured beef decreased first and then increased under different salt additions,.The lower the salt addition,the higher the final water contents.The overall change of pH was small and maintained in the acid range of 5.37-5.46.The loss rate,salt contents and total number of colonies increased with the dry-curing time.The more salt added,the greater loss rate,the higher salt contents,the lower colony counts.About the sensory evaluation results,the salty taste,spicy taste,juiciness were moderately,with no off-flavor and satisfying overall evaluation of the test group with 2.5%salt added for dry-curing 3 h,and its all scores were highest in all groups with off-flavor(P<0.05).Therefore,the treatment group with 2.5%salt added for dry-curing was selected as the optimal dry-curing technology of beef at 4?.2.Evaluation of color and flavour characteristics of xylose-cysteine Maillard reaction model system at 110?5 mL of beef broth extract heated for 30 min was used as stock solution.The Maillard reaction model was designed in 6 groups with different amounts of xylose(0.2,0.6 g)and cysteine(0.2,0.6,1.0 g)by factorial experiments.The reaction was performed at pH7,110? for 70 min and determined its OD value,sensory indications(color,roasted aroma,burnt flavor,sulfur pungent flavor and comprehensive evaluation)and electronic response.The multiple linear regression equations between sensory and electronic nose response value are Y1(roasted aroma)=-10.600R1+13.287R5-0.922R8+7.237;Y2(burnt flavor)=-16.807R1+9.904R5-0.173R7+9.996;Y3(sulfur pungent flavor)=-27.021R1+20.130R5-0.222R7+10.3929 and were used to calculate electronic nose prediction score.The results reflected that the group added 0.2 g xylose and 0.2 g cysteine had the highest scores of color,roasted aroma,burnt flavor,sulfur pungent flavor,comprehensive evaluation and electronic nose prediction score.Therefore,the Maillard reaction product generated by the treatment group added 0.2 g xylose and 0.2 g cysteine.was selected as the optimal model.The optimal model were detected 11 types,52 kinds of volatile aromatic substances,mainly included thiazoles,ketones,pyrazines,furans,aldehydes,thiophenes and so on.The typical flavor compounds included 4-methyl-5hydroxyethylthiazole,3,3'-dithiobis(2-methyl)-furan,2-methylpyrazine,3-methyl butyraldehyde.The model also were detected 10 types of HCAs,which contained IQ?8-MeIQx?4,8-DiMeIQx?PhIP?Harman?Norharman?AaC?MeAaC?Trp-P-1 and Trp-P-2,with a total content of 2.660 ng/mL.3.Effects of thermal field drying and preservation on the contents of HCAs and BaP beef products.The longest back muscle of beef was used as test material.The thermal field dried beef and traditional roasted beef were prepared by thermal field drying equipment at 110? for 70 min and electric roasting device at 220? for 15 min,respectively,which were then reheated and quick-frozen.This experiment studied the effects of different processing technologies and different preservation methods on flavor and physical and chemical indexes in beef products.The results reflected that the two technologies have no significant difference on color,roasted taste,juiciness,off-flavor,comprehensive score,a*and b*of beef products.The L*,aw and HCAs types and contents of thermal field dried beef were significantly lower than traditional roasted beef,shear force value and free radical contents were significantly higher than traditional roasted beef.The traditional roasted beef contained IQ?MeIQ?Harman?Norharman?MeAaC and Trp-P-2,with a total content of 24.812 ng/g and total content of free radicals was 3.990×105 spin/g.The thermal field dried beef contained IQ?Harman?Norharman?MeAaC and Trp-P-2,with a total content of 8.773 ng/g and total content of free radicals was 17.731×105 spin/g.The BaP contents in both beef products were not detected.After reheating,the total amounts of HCAs in traditional roasted beef increased by 89.87%(P<0.05),the free radical contents increased by 4.54 times(P<0.05)and BaP was not detected.After quick-freezing,the total amounts of HCAs decreased by 10.90%(P>0.05),free radical contents increased by 0.73 times(P>0.05)and BaP was not detected.After reheating,the total amounts of HCAs in thermal field dried beef increased by 3.28 times(P<0.05),the contents of free radicals increased by 92.49%(P<0.05)and BaP was not detected.After quick-freezing,the total amounts of HCAs increased by 29.39%(P>0.05),the contents of free radicals increased by 10.33%(P>0.05)and no BaP was detected.