Difference Of Meat Flavor In Sunit Lamb (Concentrated Vs Grazing) And Primary Formation Mechanism

The flavor of the meat includes the aroma and taste.Flavor precursors through chemical reactions(decomposition,oxidation,reduction,etc)produced aroma.Aroma substances include aldehydes,alcohols,acids,ketones,esters,containing nitrogen and sulfur compounds.Taste substances are mainly composed of amino acids,peptides,nucleotides,sugars,acidified acids and salts.Sunit lambs(concentrated vs g razing)with 12 months of age were detected the precursor substances,analysed the effects of feeding methods on sensory score,meat quality and flavor,and explored the formation mechanism of flavor.Further 48 Sunit lambs were divided into 4 groups(grazing,concentrated,lactic acid bacteria,and flaxseed group;adding lactic acid bacteria or flaxseed to the diet),feeding during 90-day trial,to investigate the differences of flavor.There are provide basic data and theoretical basis for better improving meat flavor.The result indicated that:the intramuscular fat(IMF)in grazing lambs was significantly lower than concentrated lambs(P^O.OS),shear force of triceps brachii and longissimus dorsi were significantly lower than concentrated lambs(P<0.05),cooked meat rate of biceps femoris and longissimus dorsi were significantly lower than concentrated(P<0.05),while pH24 value of longissimus dorsi and triceps brachii was significantly higher than concentrated lambs(P<0.05).Mb of triceps brachii and longissimus dorsi in grazing was significantly higher than concentrated(P<0.05),while MMb of longissimus dorsi was significantly lower than concentrated(P<0.05).The sensory score of grazing lamb meat was significantly higher than concentrated(P<0.05),which indicated that grazing meat was more acceptable in terms of color,flavor and taste.Among flavor precursors,reducing sugar and thiamine of longissimus dorsi in grazing lamb were higher than concentrated(P<0.05).As to fatty acids,SFA and MUFA in concentrated lamb meat were higher than grazing,while PUFA was lower than grazing,glutamic(Glu),aspartic(Asp)and Alanine(Ala)of longissimus dorsi in grazing lamb were significantly higher than concentrated(P<0.05),while lysine(Lys)and leucine(Leu)were significantly lower than concentrated(P<0.05).In aroma,aroma fingerprint of grazing was different from concentrated The W1S and W5S response values of Triceps brachii in grazing lamb meat were significantly higher than concentrated(P<0.05).In volatile substances,concentrated lamb had high contents and low species;Among them,hexanal and 2,3-Octanedione in concentrated were significantly higher than grazing(P<0.05),and l-octene-3-ol of longissimus dorsi and triceps brachii were significantly lower than concentrated(P<0.05).As to taste,umami in grazing was significantly higher than concentrated,and bitter of longissimus dorsi and triceps brachii were lower than concentrated.In the nucleotides,IMP and INO of longissimus dorsi and triceps brachii in grazing lambs were higher than concentrated,which improve the umami in meat.Combining aroma and taste,the grazing lamb meat had a better flavor.Aromas were mostly derived from lipid oxidation.The lipid oxidation degree in concentrated lamb meat was higher than grazing(P<0.05),and the antioxidant ability in grazing was better than concentrated.T-AOC and CUPRAC in grazing lamb were higher than concentrated(P<0.05),SOD and CAT of biceps femoris and triceps brachii were significantly higher than concentrated(P<0.05),GSH-Px of biceps femoris and longissimus dorsi in grazing were significantly higher than concentrated(P<0.05),which can inhibit lipid oxidation and improve the flavor of meat.Another way to produce flavor is metabolic deposition.Rumen bacteria(Firmicutes,Proteobacteria and Synergistetes)are involved in the production of metabolites.There were 61 rumen difference metabolites in the two feeding methods.Among them,maltose,phenylalanine,leucine and xanthine in concentrated were significantly higher than grazing(P<0.05),while caproic acid,arachidic acid and alpha-linolenic acid were significantly lower than grazing(P<0.05).In the rumen metabolic pathway,metabolites were mostly involved in pathways for phenylalanine metabolism and synthesis of unsaturated fatty acids.There were 43 difference metabolites in blood.Among them,cholic acid,phenylalanine and isoleucine in concentrated were significantly higher than grazing(P<0.05),while alpha-linolenic acid and oleic acid were significantly lower than grazing(P<0.05).Metabolites were mostly involved in pathways for histidine metabolism,phenylalanine metabolism,linoleic acid metabolism and alpha-linolenic acid metabolism.In the genes that regulate flavor formation,lipid metabolism genes are involved in regulating the production of aroma in meat.The expression of PPAR? and LPL genes of biceps femoris in concentrated lamb was higher than grazing(P<0.05).In the regulation of antioxidant enzymes,SOD,CAT and GSH-Px gene expression level in grazing was higher than concentrated,while LOX gene expression level in concentrated was significantly higher than grazing(P<0.05).In the genes that regulate nucleotide metabolism,the expression levels of AMPD and ADSL genes of Longissimus dorsi in grazing were higher than concentrated.Adding Lactobacillus and flaxseed to the diet to regulate the flavor,it was found that volatile content in concentrated was the highest(P<0.05),and species in grazing and flaxseed group were higher(P<0.05),which indicated that adding Lactobacillus and flaxseed to the diet could contribute to improve the meat aroma.As to taste,umami in grazing group was highest(P<0.05),and bitter in concentrated group was highest(P<0.05),IMP and INO in grazing,flaxseed and Lactobacillus group were higher than concentrated group.As to free amino acids,Glu and Asp in Grazing group were highest(P<0.05),Ala in flaxseed group was highest(P<0.05).Overall,adding Lactobacillus and flaxseed to the diet can improved the taste and meat quality,making flavor close to grazing group.