Effects Of Concentrate And Pasture Feeding Systems On Flavor And Tenderness Of Yanchi Tan Sheep Meat

Pasture feeding is the traditional feeding system of Yanchi Tan sheep.In recent years,in order to balance the ecology and increase the yield,the feeding of Tan sheep has gradually changed to concentrate feeding,which will inevitably lead to the change of meat quality.Thus,how to maintain the meat quality of Yanchi Tan sheep under the condition of concentrate feeding has become the focus of the industry.This paper aims at the lack of systematic research on the quality difference of lamb fed in concentrate and pasture feeding systems and carried out from the aspects of flavor and tenderness.Twenty eight male Yanchi Tan sheep(weight close to 28.4±2.5 kg)aged 4～5 months were randomly divided into two equal groups,with 14 replicates per group and one sheep per replicate.Each group was raised for 60 days under concentrate(CF)and pasture(PF)feeding systems respectively.After the experiment,all sheep were slaughtered,and longissimus dorsi from Ribs 11 to 13 with uniform meat quality and exercise skeletal muscle biceps femoris were collected for experiment.Experiment 1: Effects of concentrate and pasture feeding systems on the meat quality,flavor precursors and volatile flavor compounds in longissimus dorsi of Yanchi Tan sheepIn the study of longissimus dorsi showed that compared with CF,the p H,redness and shear force of PF were significantly increased(P < 0.05),and the intramuscular fat content was significantly decreased(P < 0.05).The results of sensory bionic evaluation showed that the scores of tenderness,juiciness and flavor intensity of PF were significantly decreased(P < 0.05),the electronic tongue response values of richness and sweetness of were significantly increased(P < 0.05),while the response values of bitterness were significantly decreased(P < 0.05),and the results of electronic nose showed that the lamb of PF contained more sulfur compounds,terpenes and pyrazines.As far as flavor precursors were concerned,PF significantly reduced the relative contents of palmitic acid(c16:0)and oleic acid(c18:1n9c),significantly increased the relative contents of polyunsaturated fatty acids such as linoleic acid(c18:2n6c)and linolenic acid(c18:3n3)(P < 0.05),and significantly decreased the n-6 /n-3 ratio(P < 0.05).The contents of methionine,glutamic acid,glycine,glucose-1-phosphate,flavin adenine dinucleotide,lactic acid and other water-soluble flavor precursors in PF were significantly increased(P < 0.05).A total of 57 volatile compounds were identified by gas chromatography ion mobility spectrometry(GC-IMS).Compared with CF,PF significantly increased the contents of benzaldehyde,γ-butyrolactone and other compounds(P < 0.05).while the contents of trans-2-nonenal,octanal,heptanal and other aldehydes in lamb of CF were significantly decreased(P < 0.05).Experiment 2: Effects of concentrate and pasture feeding systems on muscle fiber characteristics of biceps femoris in Yanchi Tan sheep and its protein degradation during postmortem aging.In the study of biceps femoris showed that,compared with CF,the shearing force,hardness,and cohesiveness of lamb in PF were significantly increased(P < 0.05),while the springiness was significantly decreased(P < 0.05).The density of muscle fiber in PF was significantly lower than that in CF(P < 0.05),the diameter,cross-sectional area and quantity proportion of type I muscle fiber were significantly higher than those in CF(P < 0.05),and the quantity proportion of type II muscle fiber was significantly lower than that in CF(P < 0.05).The microstructure showed that the damage of myofibril structure in PF was significantly lower than that of CF.During postmortem aging,the myofibrillar fragmentation index increased significantly and then tended to be stable.The increase rate of the PF(41.94%)was lower than that of CF(50.97%).The sarcoplasmic protein solubility in PF was significantly lower than CF(P < 0.05).But there was no significant difference in myofibrillar protein solubility between the two group(P > 0.05).The sarcoplasmic protein has great degeneration and higher degradation rate of PF,while the degradation of myofibrillar protein was not obvious,and the amount of small molecular protein was less than that of CF.In conclusion,compared with the CF,the lamb taste of PF was more rich and sweet,the relative content of flavor precursors such as polyunsaturated fatty acids and amino acids was higher,the content of ester volatile flavor compounds increased significantly,the overall flavor changed significantly.Compared with CF,PF decreased the density of biceps femoris muscle fiber,increased the proportion and diameter of type I muscle fiber,decreased the degree of postmortem muscle fiber rupture and protein degradation rate,and significantly changed the tenderness of biceps femoris of Tan sheep.