C. LIU (1), G. Luan (1), X. Yin (2), Q. Li (1); (1) Jiangnan University, Wuxi, China; (2) Cargill Malt, Wayzata, MN, U.S.A.

Fermentation
Wednesday, June 4 - 10:00 a.m.-11:45 a.m.
Level 3, Crystal Room

Biogenic amines (BAs) are bioactive nitrogenous organic substances that are produced by amino acid decarboxylation in fermented foods and have been used as an indicator in the evaluation of food freshness and microbial contamination status during fermentation. This study attempts to clarify and quantify the sources of BAs during beer fermentation. The content of 8 BAs in 29 beers, 5 malts, 5 hop pellets, 5 brewing water samples, and fermentation broth samples from 3 fermentors were detected using reversed-phase high-performance liquid chromatography (RP-HPLC) optimized by the uniform design and modified simplex method. At the same time, anaerobic bacteria colony forming units (CFU) in the fermentation broth samples were also observed by the traditional spread plate method. The derivatization reaction was carried out with benzoyl chloride as the derivative reagent at 30°C for 20 min. The Agilent Eclipse XDB-C18 column (250 mm × 4.6 mm i.d.) was chosen as the chromatographic column, and mobile phases were ammonium acetate solution (phase A, 0.01 mol/L) and acetonitrile (phase B) with a flow rate of 0.6 mL/min. The sample was analyzed at 254 nm with a column temperature of 28°C. The results showed that eight BAs in most of beer samples could be detected with a total content of 4.21–10.59 mg/L. The content of histamine, tyramine, and total BAs in beer did not pose health risks for consumers, however. The total content of BAs in barley malts fluctuated between 66.03 and 148.32 mg/kg. Variety and origin were two important factors affecting the BA content of malts. Meanwhile, histamine was not detected in any of the hop pellets, and the total content of BAs in hop pellets changed from 80.72 to 175.08 mg/kg. By contrast, no BAs was detected in brewing water. Considering the very little addition of hops (less than 0.3%) during brewing in China, malts were the main source of BAs from brewing raw materials. Generally, the content of BAs from fermentation stage only accounted for 10% of the total BAs in beer fermentation broth, but it would vary among different fermentors. By comparison, the CFUs of beer fermentation broth were directly proportional to the total content of putrescine, cadaverine, tyramine, and histamine, which illustrated that the content of the four BAs could reflect the contamination status of anaerobic microorganisms. Therefore, with the increasing in concerns about food safety, it will be of great importance in the microbial control of brewing processes (especially for draft beer without a pasteurization process) to monitor changes in BA content.

Chunfeng Liu received a master’s degree in fermentation engineering from Jiangnan University, Wuxi, China. She began employment with Jiangnan University in 2008. She is now working as an assistant teacher in the Lab of Brewing Science & Technology in the School of Biotechnology. Since May 2011, she has functioned as an intermediate experimentalist. At present, she is a Ph.D. on-the-job candidate with a doctoral dissertation on “Biogenic Amines during Brewing Process.”