Study On Terpenoids In Strong Flavor Baijiu Production And The Effect Of Actinomycets On Them

As flavour and health are the future trends in Baijiu brewing,it is important to investigate the sources of trace components and health factors in Baijiu in order to improve the quality of Baijiu.Terpenoids are not only an important health factor in Baijiu,but also play an important role in improving the quality of Baijiu by providing a more elegant and delicate flavour in the body.In this paper,we used headspace solid-phase microextraction-gas chromatography-mass spectrometry(HS-SPME-GC-MS)to trace the terpenoids in the brewing process of Strongflavor Baijiu,including raw materials,Jiuqu,cellar mud,fermented grains and base Baijiu.Four different strains of actinomycetes from different sources were subjected to different substrates and different modes of pure grain fermentation,in order to explore the production of terpenoids by actinomycetes and their characteristics in the production of terpenoids by different fermentation methods using different raw materials,which provide a reference value for identifying the sources of terpenoids in Baijiu and regulating the content of terpenoids in Baijiu.The main findings of the study are as follows.(1)The terpenoids produced in the volatile state as well as after acid and enzymatic hydrolysis were tested in nine brewing raw materials and a total of 33 terpenoids were detected in the three states of the grain at a total concentration of 2121.42 μg/kg.(2)The terpenoids involved in the brewing process were tested,including Jiuqu in different time periods,cellar mud of the different cellars,fermented grains of the different nodes and base Baijiu.Nine compounds in base Baijiu are considered,four of which are brought in by grain,three are brought in by Daqu,and two are converted by other substances due to high temperature during steaming.(3)Four species of actinomycetes Streptomyces violascens(SPQ1),S.sampsonii(SPS1),S.thermophilus(SPG1)and S.griseus(SPH1),screened from Daqu,cellar mud,fermented grains and air,were subjected to solid and liquid fermentation with five brewing ingredients as substrates.In liquid fermentation,SPQ1 produced the highest content of terpenoids and SPG1 produced the greatest variety of terpenoids.SPS1,SPQ1 and SPH1 showed good production of β-eucalyptol when using sorghum for liquid fermentation.At 28 d of solid-state fermentation,SPS1 produced the highest amount of terpenoids and SPG1 produced the greatest variety of terpenoids.Sorghum produced the most terpenoids when solid-state fermentation was carried out using all five raw materials.The products of solidstate fermentation by the four Streptomyces strains showed the most prominent increase inβ-eucalyptol,and SPS1 and SPQ1 also showed a good capacity to produce B-cedrene.(4)Solid state laboratory simulated fermentations were carried out with SPS1 and SPQ1,respectively.The results showed a corresponding increase in terpenoid content with increasing inoculum of the bacterium relative to the blank experiment.75.5% increase in terpenoid content was observed for SPS1 inoculum reaching 5% and 17.45% increase for SPQ1 inoculum reaching 5% relative to the blank group.