Study On Solid-state Fermentation Of Pig Bone Extract To Produce Hydrolase And Tastes Characteristics Of Degradation Products

Pig bone is a major by-product in pork process. It is mostly tossed away as a result of poor disposition. Commodity pig bone extract was sandy beige or brown paste, which was produced by natural pork bone process. Pig bone extract had a strong fishy smell and couldn’t easily be absorbed by human, so it needed further processing to enhance flavor and color. There were few reports or research on solid-state fermentation of pork bone extract、the change of hydrolase activities and the flavor of degradation products. In this study, Pig bone extract was used as the main raw material under solid fermentation conditions by Monascus、Aspergillus oryzae and mixed strains of Monascus and Aspergillus oryzae to investigate the change of hydrolase activity and main physicochemical indexes. At the same time, tastes characteristics of degradation products were analysed. The result shows:(1) Pig bone extract as the main raw material, while Wheat bran as support with solid-state fermentation, the addition of pig bone extract was80%, crude enzyme of Monascus was obtained by sequential ammonium sulfate precipitation. Native-SDS-PAGE showed that more than one white band appeared in relevant position of electrophoretogram. That may confirmed that enzyme solution of Monascus had biological activity of protease、amylase、 xylanase. Protease had two bands, molecular weight was about54KD and28KD; amylase had one bands, molecular weight was about85KD and54KD; xylanase had two bands, molecular weight was about35KD and14KD.(2) Protease activity as main standard, single factor and orthogonal tests were used to determine the optimal fermentation process. Monascus solid fermentation conditions were that temperature28℃, pH5.5, water8mL, inoculation10%; Aspergillus oryzae solid fermentation conditions were that temperature30℃, pH7, water8mL, inoculation8%; inoculating Aspergillus oryzae after10days fermentation by Monascus, temperature from28℃turn to30℃, the mixed strains solid fermentation conditions were that water1mL, inoculation10%.(3) Accotding to the optimal fermentation conditons, the change of hydrolase activities were investigated during40day fermention. In the process of fermentation by Monascus, protease、amylase and xylanase activity increased to peak at6th day,10th day,5th day respectively, which were279U/g、169U/g、117U/g respectively. In the process of fermentation by Aspergillus oryzae, protease、amylase and xylanase activity increased to peak at3th(30th) day,6th day,7th day respectively, which were1050U/g(1630U/g)、229U/g、1036U/g respectively. In the process of fermentation by the mixed strains, protease、amylase and xylanase activity increased to peak at35th day,12th day,25th day respectively, which were1466U/g、196U/g、966U/g respectively.(4) Accotding to the optimal fermentation conditons, the change of main physicochemical indexes were investigated during40day fermention, and combined with physical and chemical indicators and taste evaluation to determine optimal fermentation time. In the process of fermentation by Monascus, SDS-PAGE analysis showed that the range of the main protein bands was116KD-45KD, Amino acid nitrogen increased from0.004g/100mL to0.205g/100mL, reducing sugar decreased from240mg/100mL to181mg/100mL, red index increased from1.60to3.35, pH increased from5.50to7.03.The optimal fermentation time was40d. In the process of fermentation by Aspergillus oryzae, SDS-PAGE analysis showed that the range of the main protein bands was116KD-24KD, Amino acid nitrogen increased0.003g/100mL to0.363g/100mL, reducing sugar decreased from240mg/100mL to37mg/100mL, red index increased from1.60to4.16, pH increased from7.00to7.90. The optimal fermentation time was30d. In the process of fermentation by the mixed strains, SDS-PAGE analysis showed that the range of the main protein bands wasl16KD～12KD, Amino acid nitrogen increased from0.004g/100mL to0.396g/100mL, reducing sugar decreased from240mg/100mL to56mg/100mL, red index increased from1.60to5.67, pH increased from7.00to7.82. The optimal fermentation time was35d.(5) Amino acid content was low in Monacus fermentation broth, and GC-MS analysis showed that there could be detected78flavor components, mainly with amine and hydrocarbon compounds. Umami amino acid ratio was low, while bitter amino acids ratio was high in Aspergillus oryzae fermentation broth, and GC-MS analysis showed that there could be detected102flavor components, mainly with hydrocarbon and ketones compounds. Umami amino acids ratio was high in the mixed strains fermentation broth, and GC-MS analysis showed that there could be detected87flavor components, mainly with ketones and acids compounds.