| China is a major producer and consumer of meat,and fresh meat accounts for about 80%.However,the improper chilling methods and storage temperature could cause the decline of quality and shelf life of fresh meat.Microorganism is an important factor affecting fresh meat quality which was closely related to temperature.This study was aimed to explore the different chilling methods and storage temperatures on the quality and the change of microorganism of fresh lamb meat.It has been reported that cold processing technologies such as very fast chilling,supercooling and superchilling could maintain the quality of fresh meat.To date,the change of microbial composition of fresh meat under different storage conditions has rarely been reported.Therefore,this study was aimed to explore the chilling methods and storage temperature on the quality and microorganism of lamb carcasses and lamb meat.The relationship between quality and microorganism of fresh lamb meat was analyzed under different cold processing methods.In conclusion,this work provides data for the novel technology of the preservation of fresh lamb meat.The specific research results are as follows:(1)The change of freshness and the surface microorganisms of lamb carcasses were explored under different treatments such as conventional chilling(4℃ chilling,1.76℃/h),ultra-fast chilling(-20℃ chilling,12.52℃/h),and very-fast chilling(-35℃ chilling,14.52℃/h).There was no significant difference in L*,a*and b*values of lamb carcasses for conventional,ultra-fast and very-fast chilling during storage period(P>0.05).The pH value showed a trend of decline and the pH value of very-fast chilling was always higher than other treatments.The total volatile base nitrogen(TVB-N)and thiobarbituric acid reactive substance(TBARS)values of very-fast chilling were always lower than other treatments.The total viable counts(TVC)of lamb carcasses of very-fast chilling was always lower than conventional chilling,and there was a significantly difference occurred after 3 day.At the genus level,Psychrotrophic was the dominant bacteria in the three chilling treatments.Macrococcus,Turicibacter and Brevibacterium were positively correlated with TVB-N,and Turicibacter was positively correlated with TBARS.Therefore,Macrococcus,Turicibacter and Brevibacterium were the dominant spoilage bacteria.Based on the 16S rRNA sequencing results,the main metabolic pathways include biosynthesis of amino acids,carbon metabolism,ABC transporters and purine metabolism.(2)The change of quality and microorganisms of lamb were explored under different treatments such as hot boning,conventional chilling(4℃ chilling,1.76℃/h),and very-fast chilling(-35℃ chilling,14.52℃/h).The L*value of lamb meat showed the trend of increase and then decline for hot boning,conventional and very-fast chilling during storage period.There was no significant difference in a*value of lamb meat for hot boning,and the b*values of hot boning and very-fast chilling were not significant during storage period(P>0.05).The pH value of three treatments had no significant difference(P>0.05).The TVB-N and TBARS values showed a trend of increase for the three chilling treatments,and the TVB-N value of very-fast chilling was significantly lower than hot boning treatment.The TVC and Psychrophilic bacteria count of very-fast chilling treatment were significantly lower than conventional chilling treatment(P<0.05).At the genus level,Pseudomonas,Mitochondria and Ralstonia were the dominant spoilage bacteria for the three treatments.Pseudomonas was positively correlated with TVB-N and TBARS(P<0.05).Based on the 16S rRNA sequencing results,the main metabolic pathways include biosynthesis of secondary metabolites,ABC transporters,two-component system,biosynthesis of amino acids,carbon metabolism and purine metabolism.(3)The change of quality and microorganisms of lamb were explored under different treatments such as chilling(4℃),supercooling(-1.5℃),superchilling(-4℃)and sub-freezing(-9℃).There was no significant difference in L*value of lamb for chilling,supercooling,superchilling and sub-freezing.The a*value of lamb for chilling and supercooling had no significant difference(P>0.05)during storage period.The pH value of chilling,superchilling and sub-freezing had no significant difference(P>0.05)with the storage time prolonged.The TVB-N and TBARS of the chilling,supercooling,superchilling and sub-freezing treatments increased with the extension of storage time,and the higher storage temperature was,the rate of growth was higher.The TVB-N and TBARS of chilling treatment exhibited a higher rate of increase compared to other treatments at day 14.The shelf life of chilling and supercooling storage was 14 d and 28 d,respectively.And the shelf life of superchilling and sub-freezing storage was over 70 d.At the genus level,Pseudomonas was identified as the main spoilage bacteria for chilling storage,Pseudomonas and Brochothrix were recognized as the dominant spoilage bacteria for supercooling storage,and the Psychrobacter,Pseudomonas and Ralstonia were proved that they were the dominant spoilage bacteria for superchilling and sub-freezing storage.The Pseudomonas was positively correlated with TVB-N(P<0.05).Therefore,Pseudomonas was the main spoilage bacteria for all treatments.Based on the 16S rRNA sequencing results,carbohydrate metabolism and amino acid metabolism were the main metabolic pathways. |
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