| As the sign matter of royal jelly, the 10-HDA posses bacteriostatic action and bactericidal ability it also exhibits several nutritional healthy biological activities, including anti-cancer, enhancing immune function and so on. Top-fermented wheat beer with living yeasts has not been filtered, which made it bad biological stability. The antimicrobial effect of 10-HDA on G+ beer-spoilage bacteria Lactobacillu brevis and Pediococcus damnosus was determined in our early experiment stage. In the present study, we chose typical G- beer-spoilage bacteria Pectinatus.spp and wild yeasts to detect the effect of 10-HDA on these different beer-spoilage strains, we will develop the 10-HDA to be a natural preservative of top-fermented wheat beer.This study used three organic solutions such as ether, ethyl acetate and ethanol as the extractive solution, and also employed two extractive processions. It used the method of high pressure liquid chromatography to compared the extraction efficiency of 10-HDA. The result of the compare is that using the ethanol shake the royal jelly can receive the highest extractive ratio of 10-HDA.The process of extraction of 10-HDA from royal jelly was optimized through the orthogonal experiments. The optimal conditions included: ethanol concentration 100% ,solid/liquid 1∶6 , extraction time was 60 min,the frequency of the extraction was 1. Under these conditions, the yield of 10-HDA in the extraction was 33.893%, purity was 73.5325%.The antimicrobial effect of 10-HDA on two strains of bacteria and three strains of yeasts was determined by Oxford cup assay and we also determined the minimum inhibitory concentration (MIC) of 10-HDA by double dilution method. Our results showed that 10-HDA could significantly inhibit the Candidamy coderma, Pectinatus cerevisiiphilus, Pectinatus frisingensis in beer. In contrast, no inhibition effect was found while treating top-fermenting yeasts No.303 and Saccharomyces c.diastaticus with 10-HDA. The minimum inhibitory concentration (MIC) of 10-HDA on Candidamy coderma, Pectinatus cerevisiiphilus, Pectinatus frisingensis were as follows: 0.375 mg/mL, 0.625 mg/mL,1.25mg/mL.The 10-HDA was also studied for its antimicrobial stability to temperature, PH and ultraviolet. The results showed that 10-HDA is very stable to ultraviolet. High temperature was not good for the performance of 10-HDA, but it still have antibacterial effects after dealing with 121℃for 30 minutes; PH has obviously effect on 10-HDA, the higher antibacterial activities were showed at lower PH value. The study of the 10-HDA effect on the growth of microorganism for test, found that the 10-HDA not only antiblastic the growth of microorganism for test, but also kill them.The hops in beer with its main components as iso-α-acid could inhibit the activity of beer spoilage bacteria. We detected the hops resistance of tested strains to determine if the performance of antibacterial effects was produced by 10-HDA or cooperated with iso-α-acid. The results showed that iso-α-acid could significantly inhibit the Candidamy coderma at the MIC 62.5mg/L. In contrast, no inhibition effect was found while treating Pectinatus.spp and Saccharomyces c .diastaticus with iso-α-acid.In this study, 10-HDA was added to the top-fermented wheat beer with the bitterness 20.25mg/L. The antimicrobial effect of 10-HDA in this beer was determined by NBB culture medium test and microorganism index. The results showed that the 10-HDA performed good antibacterial effects without conjunction with iso-α-acid.Therefore,it was confirmed that 10-HDA could be developed as a novel antimicrobial agent for top-fermented wheat beer. |
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