| Dry-fermented meat products become very popular with the consumers due to their distinctive flavor.Some quality defects appeared,such as high salt content,lipid oxidation,biogenic amines,and nitrosamines content exceeding standard value are increasing becoming the focus of consumers' attention.Extensive investigations have been conducted focusing on detection technology and starter cultures in order to illustrate the formation mechanism in inhibiting of biogenic amines in meat products in the past decades.However,studies on the biological regulation mechanism of biogenic amines and nitrosamines in dry-cured meat products during processing have just started.The objective of this study is to investigate the nitrite,summarized the research progress in the production conditions of biogenic amines and nitrosamines in traditional dry-cured bacon,microorganism involved in biogenic amines,nitrosamines accumulation,and their correlation,to explore the mechanism of the plant polyphenols and partial NaCl replacement in controlling the accumulation of biogenic amines and nitrosamines.Our results will provide the theoretical basis for improving the quality of dry-cured meat products.The detailed contents and results are summarized as follows.1.Effects of plant polyphenols and a-tocopherol on lipid oxidation,microbiological,and biogenic amines formation in dry-cured baconsGreen bacon belly pieces were used as the material,and treated with different concentrations of green tea polyphenol(GTP),grape seed extract(GSE)and gingerol and a-tocopherol(100-500 mg/kg)at the salting process.After the curing and drying,the changes of physical and chemical index,microorganism and biogenic amine content were analyzed to explore the inhibition of microorganism and biogenic amines in dry-cured bacons.Six kinds of biogenic amines(putrescine,cadaverine,histamine,tyramine,spermine and phenylethylamine)were detected in dry-cured bacons.Results showed that plant polyphenols and a-tocopherol significantly decreased TVBN and TBARS value(P<0.05).GTP was the most effective(P<0.05)in reducing aerobic plate counts,Enterobacteriaceae,Micrococcaceae,yeast and molds,as well as in inhibiting formation of putrescine,cadaverine,tyramine and histamine.Principal component analysis(PCA)indicated that cadaverine and putrescine were significant positive related with Enterobacteriaceae.Addition 300 mg/kg GTP could significantly(P<0.05)reduced the content of biogenic amines in dry-cured bacon,showing reduction of 38.8%compared to the control.Plant polyphenols could inhibit the formation of biogenic amines.2.Effects of plant polyphenols and a-tocopherol on residual nitrites and N-nitrosamines formation,and their correlation of dry-cured bacon300 mg/kg of GTP,GSE,GTP + GSE(150 mg/kg + 150 mg/kg)and a-tocopherol were rubbed on the surface of the bacons.Their effects on physicochemical parameters,lipid oxidation,residual nitrite,microbiological counts,biogenic amines,and N-nitrosamines were analyzed in bacons during dry-curing and storage.Results showed that residual nitrite reduced significantly,but biogenic amines and nitrosamines contents increased significantly during processing(P<0.05).Plant polyphenols and a-tocopherol significantly decreased TBARS value and residual nitrite content compared with the control(P<0.05)at the end of ripening.Microbial counts,biogenic amines,and N-nitrosodimethylamine(NDMA)contents in dry-cured bacons were significantly affected by plant polyphenols or a-tocopherol(P<0.05),with GTP being the most effective in reducing aerobic plate counts(APC),Enterobacteriaceae,and biogenic amines(putrescine,cadaverine,histamine,tyramine and spermine),as well as in inhibiting the NDMA formation(P<0.05).PCA indicated that there were positive correlations between pH value,biogenic amines(putrescine,cadaverine,histamine,tyramine and spermine),NDMA and APC,as well as a negative correlation between NDMA and nitrite.These findings suggest that plant polyphenols were able to reduce the nitrite residue,prevent nitrosation,and inhibit the NDMA formation.3.Study on regulation mechanism on formation of N-nitrosamines in bacons using plant antioxidantsIn order to obtain the optimum addition of plant antioxidants to reduce the N-nitrosamines content in bacons,three key factors including tea polyphenols concentration,grape seed extract dose and sodium nitrite levels were optimized using the Box-Behnken response surface methodology based on single-factor experiment.The regulation method of N-nitrosamines residues was explored by analyzing the interactive effects of tea polyphenol and grape seed extract on N-nitrosamines residues.Results showed plant antioxidants could significant(P<0.05)reduce Nnitrosamines residues,Tea polyphenol existed a critical value for NDMA residues,which was determined as 308.3 mg/kg at grape seed extract 400 mg/kg,and above which inhibited the NDMA residues was not significant(P>0.05).NDMA residue had significant interactions(P<0.05)with tea polyphenol and grape seed extract.The tea polyphenol critical value increased linearly with grape seed extract concentration.The optimum addition of plant antioxidants were as follows:tea polyphenol 310 mg/kg,grape seed extract 420 mg/kg and sodium nitrite 120 mg/kg.Under the verification experiment,NDMA residue was 0.325?g/kg,which was close to the theoretical values of 0.3395?g/kg.4.Effects of potassium on biogenic amines and N-nitrosamines formation of dry-cured baconBacons were salted with four formulations,including 100%NaCl(?),80%NaCl and 20%KCl(?),60%NaCl and 40%KCl(?),and 40%NaCl and 60%KCl(?).Effects of partial replacement of NaCl by KC1 on physicochemical parameters,total volatile basic nitrogen(TVBN),residual nitrite,biogenic amines,and N-nitrosamines contents were determined in dry-cured bacons during processing and storage.Results showed that there were not significant differences(P>0.05)in moisture,pH,and TVBN content among treatments during processing.In the bacons treated with formulation III and IV,nitrite residues were significantly enhanced compared to the control(P<0.05),while putrescine,cadaverine,tyramine and histamine contents were significantly reduced.After 12-day ripening and during storage,the substitution of NaCl by 60%KC1 significantly increased the NDMA content(P<0.05).PCA showed that there were positive correlations between TVBN,biogenic amines(putrescine,cadaverine,histamine,and tyramine)and NDMA,and negative correlation between NDMA and nitrite.These results indicate that sodium replacement inhibited the accumulation of biogenic amines,enhanced the penetration of nitrite into bacon muscle,and accelerated the formation of nitrosamine.5.Effects of partial replacement of NaCl by KCl and composite antioxidants on profiles of volatile compounds of bacon during dry-cured processingTo investigate the effects of partial replacement of NaCl by KC1 and antioxidants on the whole flavor of bacon during dry-cured processing,the volatile flavor compounds in samples of bacons from different processing stage were analyzed by solid phase microextraction(SPME)-gas chromatography mass spectrometry(GC-MS)combined with electronic nose technology.A total of 60 volatile compounds were identified by GC-MS,which concluded 16 aldehydes,18 alcohols,9 ketones,3 carboxylic acids,5 esters and 9 hydrocarbons.Electronic nose could distinguish the samples of 4 different processing stages well.As dry-cured processing continued,the contents of flavor compounds increased in the final products.At the end of ripening,the substitution of NaCl by 40%KCl significantly increased flavor compounds by lipid-derived volatiles compared with the control(P<0.05),such as straight chain hydrocarbons and total esters.The antioxidant treatments significantly decreased 2-methylbutanal and hexanal content(P<0.05).There were no significant differences in other volatile formation between the control and antioxidant application.These results showed that more than 40%sodium replacement may significantly change profiles of volatiles in dry-cured bacons. |
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