| Deoxynivalenol?DON?and other mycotoxins produced by Fusarium graminearum are seriously endangering the quality and safety of barley malt,and consequently the beer.The existing detoxification methods in the beer industry have various defects,such as the addition of chemical bacteriostatic agents or sodium hypochlorite,which will bring new pollutants.It is necessary for the beer industry to explore green and pollution-free detoxification methods.In this paper,a F.graminearum strain producing DON and 15ADON from FHB-infected barley was isolated.Meanwhile,four types of essential oils with good inhibitory effects on F.graminearum were screened and their nanoemulsions were prepared,respectively.The stability and antifungal activity of these nanoemulsions were then investigated.Finally,the nanoemulsions with best inhibitory effect were applied in malting progress,the content of mycotoxins and the quality of malt product were monitored.The main findings are as follows:?1?A F.graminearum strain producing DON and 15ADON was isolated from FHB-infected barley,and the inhibitory effect on F.graminearum of 7 plant essential oils was evaluated using the inhibition zone method and determining the Minimum inhibitory concentration?MIC?and Minimum bactericidal concentration?MBC?.The Clove oil,Oregano oil,Cinnamon oil and Litsea Cubeba oil showed higher antifungal activity than others.Among them,Cinnamon oil exhibited the best antifungal effect,with the MIC and MBC of both 250?g·mL-1 for F.graminearum.?2?Four primary emulsions were prepared by high-speed stirring combined with high-pressure homogenization from the selected essential oil,and the preparation process was optimized.The formula of primary emulsions was 1wt%lecithin,8wt%oil phase?Clove oil and Litsea cubeba oil was pure essential oil,Cinnamon oil and Origanum oil were blended with MCT in a 1:1 ratio?and 91wt%of buffer solution.Clove oil emulsion,Cinnamon oil/MCT emulsion,Origanum oil/MCT emulsion and Litsea cubeba oil emulsion all showed unimodal distribution with average particle size of 116.9,168.5,206.0 and 203.9 nm.At the same time,the four primary emulsions displayed good storage stability in 21 days.?3?All primary emulsions could inhibit fungi growth and mycotoxins production.Among them,the F.graminearum biomass levels in barley treated with 1.5 mg·g-1 cinnamon oil/MCT emulsion reduced by 98.9%,the DON and 15ADON levels reduced by 98.8%and 96.6%at the level of 0.3 mg·g-1.Among the four kinds of primary emulsions,the Litsea cubeba oil emulsion had little effect on the germinative energy,which is 96.0%at the level of 1 mg·g-1 during the malting progress.50 g of 80 mg·g-1 Litsea cubeba oil emulsion was added in the third steeping stage.In addition,10 g of the emulsion was supplemented every day during the germination stage.The DON concentration of malt was 640?g·kg-1,which reduced by 26.3%compared with the control group.?4?Chitosan were electrostatically deposited on Litsea cubeba oil emulsions to prepare a secondary emulsion,the mean particle size and zeta potential of which was 454.9 nm and 64.2mV,respectively.The prepared secondary emulsion showed good pH stability in the range of pH 3.0-5.0,and good storage stability at room temperature in 21 days.The addition of chitosan can enhance the antifungal effect of the same concentration of essential oil emulsion,and reduce the inhibitory effect of Litsea cubeba oil on barley germination.?5?Adding 100 g of secondary emulsion with a concentration of 40 mg·g-1 at the third steeping stage,and 10 g of secondary emulsion every day during the germination stage,the germination rate of barley was 87.7%.The ergosterol concentration was 3.13?g·g-1,indicating the fungal biomass was reduced by 68.4%compared with the control group.Consequently,the DON concentration of malt was 690?g·kg-1,which reduced by 20.9%compared with the control group.The content of the malt extract was slightly lower than that of the control group,and the color and turbidity of wort were slightly increased.The filtration speed decreased significantly,and other indicators have no obvious differences. |
PDF Full Text Request