Effect Of Different Ages On Tenderness Of Cherry Valley Ducks Breast During Postmortem Aging

Although fermentation with glutinous rice is an epidemic preservation method in the middle-lower Yangtze River area, it is time consuming, which limitted the large-scale production. In thispaper, a new inoculated fermentation and changes of volatile flavor in different fermentatedChinese herring were reviewed. In addition, volatile flavor components in fermentated Chineseherring with exogenous enzymes were analyzed and discussed. The main researches were asfollows:﹙1﹚Screening and Identification of the dominant microorganisms from traditionalfermented Chinese herringMRS and RBA selective medium was used to isolate the dominant microorganisms fromtraditional fermented fish. The isolated strains were then identified by physiological andbiochemical analysis combined with MIDI identification system and molecular identification.The results showed that: Bacteria count was105CFU/g, the count of strains from MRS and RBAmedium was7.4×104CFU/g and3.0×104CFU/g respectively. The strain from MRS medium wasclassified as Lactobacillus fermentum; Strain from RBA medium was classified as Saccharomycescerevisiae.﹙2﹚Preliminary study of growth properties of the isolated microorganismsUnder different temperature,strains were inoculated on solid medium to observe microbialgrowth; Under different factors (pH, salinity) strains were inoculated into PCA liquid medium toobserve absorbance value; Stab culture method was used to determine the strains aerobic or not.Under certain condition, strains were inoculated into PCA liquid medium then measuredabsorbance value for every2hours. According to the absorbance values microbial growth curvecould obtain.Then according to the microbial growth curve, taking microbial liquid in thelogarithmic growth phase made starter cultures. The results showed that: a) Optimum growingtemperature of Lactobacillus fermentum was between30-40℃; Optimum growing temperature ofSaccharomyces cerevisiae was between30-35℃. b) Optimal pH values of Lactobacillusfermentum and Saccharomyces cerevisiae were at6.0and5.5respectively. c) Optimumconcentration of NaCl is under3%. d) Two strains were facultative anaerobe; Cell growth curves showed that the logarithmic growth phase was14h-18h, therefore, using the microbial liquid grewfor15hours prepared starter culture.﹙3﹚Optimization of parameters for preparing fermentedChinese herringThe isolated strain was inoculated to the Chinese herring for the complex fermentation withglutinous rice. Changes of the protein content, total acidity, total volatile basic nitrogen (TVBN),amino nitrogen, pH of the fish during fermentation were analyzed, the factors which effected thefermentation were investigated by single factor test and the optimal fermentation parameters werethen established by response surface methodology (RSM) and were verified in actual test. Theresults showed that the moisture content、 salinity and pH declined obviously in initialfermentation and were balance in the late; Acid value increased at first and then maintained abalance; TVBN increased in the beginning and then declined; Either too low or too highfermentation temperature was not benefit to the formation of good flavor. Increased inoculationdosage could shorten the fermentation period, while ratio of vinasse could obviously affect the tasteof the product. The optimum parameters were established by RSM as fermenting at20℃, with aratio of vinasse of2.5, and an inoculation dosage of2.28%. Under the optimum parameters,fermented Chinese herring has a good quality: Sensory value was90points, total acid was0.28%and TVBN was24.5mg100g-1.﹙4﹚Analysis flavor of fermented Chinese herringSome different fermented test group were made by adding different strain、ratio of vinasse-fish into Chinese herring. In addition, the effects of enzymes on flavor were studied by addingexogenous enzymes into Chinese herring、fish protein and fish fat (extracted from Chineseherring). Flavor of different fermented Chinese herring was measured by electronic nosesystem and the fermented Chinese herring with enzymes was measured by GC-MS. Theresults showed that: Different strains and different vinnase amount have influence on flavor;Enzymes accelerated protein and fat degradation, resulting in more esters and aldehydes such aspropanoic acid ethyl ester、acetic acid ethenyl ester、benzeneacetic acid ethyl ester、2-methyl-propanoic acid propyl ester and (E,E)-2,4-heptadienal. These volatile components encourageChinese herring more delicious flavor.