| In this study, these sausages were manufactured with mutton and sheep tail fat obtained from sheep fed in Inner Mongolia and inoculated the strain of Staphylococcus carnosus in combination with acidifying strain of Lactobacillus pentosus and Pediococcus pentosaceus as starter culture and spices for the production. 4 groups fermented sausages manufacture at the same technology and formula were named control group (CO), starter culture group (SC), starter culture and black pepper group ( SC+BP ), starter culture and black pepper and cumin (SC+BP+C), respectively. The aims of this work were to investigate the effects of quality characteristics and formation mechanism of volatile flavor compounds of mutton fermented dry sausages with starter cultures combination and spices during ripening and storage by HPLC, GC, DHS and GC-MS. A further aim was to provide a theory basis in realizing the industrial production of mutton fermented sausages and developing idea commercial starter cultures and new products in the future. The contents and results were as follows.The changes of physico-chemical properties of mutton dry fermented sausages during ripening and storage were analyzed. The results showed that: the pH values of fermented sausages inoculated the starter culture decreased ( p<0.05 ) , dropped to below 5.0 at the end of the fermentation ( 1.5 days ) and were significantly lower than the control; the pH values of all sausages increased slowly and the spice groups increased ( p<0.05 ) during the drying and ripening and kept below 5.3;the Moisture, Aw values of all sausages decreased gradually, and Aw values decreased from 0.88 to 0.85 after ripening; the changes of protein and fat contents were slight(p>0.05).The changes of the FFA (free fat acid) and the FAA (free amino acid) of mutton fermented sausages were studied during ripening and storage. The results showed that: the proteolysis indexes (PI) of the all sausages were percent 14 to 16 and the NPN and TFAA contents increased gradually during processing and enhance sharply during the middle storage. The changes of NPN and TFAA of batch SC+BP+C were significantly higher than the control(p<0.05). The contents of most FAA increased quickly above tenfold at the drying and ripening stage(p<0.05)and Arg, Glu, Leu, Lys, Ala and Val were dominant in concentration. Since the concentrations of most FAA in all sausages were 5-10 times of their corresponding sensory thresholds, the FAA might have make an important contribution to the formation of mutton fermented sausages flavor. The changes of TBARS values in all sausages were 0 mg/kg to 2 mg/kg and were not fat excessive oxidation. In general, the FFA of all the samples showed a significant increase during ripening and storage. Large amount of free fatty acids were accumulated during the storage and oleic acid,palmitic acid and stearic acid were the most abundant free fatty acids in treatment.The oleic acid contents of MUFA were improved dramatically (p<0.05), while the proportion of capric acid and stearic acid decreased during the storage , especially the sausages inoculated starter culture combination and spices were lower than the control (uninoculated). The proportion of MUFA and PUFA in the batch SC+BP and SC+BP+C decreased obviously during storage. These indicated that the MUFA and PUFA were the key fatty acids in lipid oxidation. Temperature had great effect on lipase and microbial enzyme, in this study, the TFFA increased significantly during the storage(p<0.05).A few significant differences were found in counts of microorganism between the three types of sausages and the control. Lactic acid bacteria (LAB) in sausages made with starter cultures combination and spices increased to 108cfu/g ( p<0.05 ) and kept this level in storage period, while the total bacteria counts were significantly lower than in the control and Micrococci-staphylococci were higher than the control ( p<0.05 ) at the middle period of storage. The addition of combined starter cultures and spices improved the quality attributes and shelf-life of mutton fermented dry sausages.The sensory index of all sausages at the end of ripening, earlier storage, middle storage and late storage were evaluated. The relativity of the color, flavor, texture, taste and the quality was evaluated by formula Y=0.08X1-0.147X2+0.222X3+0.836X4 (R2=0.999) and the sensory weight were successively taste > texture > flavor > color, which indicated that taste played an important role. The sensory scores of taste and the quality with combined starter cultures and spices quickly increased at the middle storage and the goaty flavor was lower than the control, which indicated that inoculating starter cultures and spices could decrease the goaty flavor and improve the quality. The correlation of the proteolysis index (B1), TBARS (B2) and the quality were evaluated by formula Y=42.354 B1+0.457 B2 (R2=0.981), the weight coefficient of PI was much larger than of the TBARS, which showed NPN, small peptide and FAA were determinant in the quality of mutton fermented sausages.The volatile flavor compounds in all treated fermented sausages at the end of clyster, end of fermentation, end of ripening, middle stage and late stage were extracted and identified by dynamic headspace sampling (DHS) and purge-trap (P & T) methods and GC/MS system. There were 93, 83, 85 and 90 flavor compounds were detected with capillary column HP-5 from the batch CO, SC, SC+BP and SC+BP+C, respectively. These volatile flavor compounds in mutton fermented sausages could be clustered in the following chemical families: alkanes and alkenes, aromatic hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, nitrogenous compounds, sulphur compounds, furan compounds and terpenoids, which showed different changing rules, especially esters and alkanes (alkenes) were more than the others whose proportions were 16%-22% and 15%-20% respectively.The sorts of volatile flavor in all treated fermented sausages was small at the end of fermentation, but large amount of (S)-Isopropyl lactate / Isoamy lactate ,2,3-Butanedione (cream) and 3-hydroxy-2-butanone (butter) were detected, which were originated from the carbohydrate catabolism. The branched chain alkane, such as 4-methyl-decane, 3-methyl-nonane, 4-methyl-heptane et al. were detected in the SC+BP batch. The key aroma-active compounds were 3-methylbutanal (dark chocolate), hexanal (grass), octanal (green, sweet), methoxy-acetic ethyl ester (sweet), trimethyl-Pyrazine (nut, roast), which were originated from lipid degradation and oxidation, amino acid Strecker reaction and the odor-active compounds contributed to fermented sausages odor together. beta.- Phellandrene (pepper), 3-Carene (pungent) and Caryophyllene (pungent) originated from the black pepper were main flavor in the mutton fermented dry sausages added spices.
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