Date

2003

Author

Buzrul, Sencer

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Filtered bright and unfiltered hazy lager beer samples were either treated with high hydrostatic pressure (200, 250, 300, 350 MPa for 3, 5 and 10 min at 10°C and 20°C) or conventional heat pasteurization (60°C for 15 min). Treatments did not affect ethanol, extract, fermentation degree, density and pH in comparison with untreated beers. Both treatments produced microbiologically stable products. Bitterness, color, protein sensitivity and chill haze parameters were affected by both the HHP and heat treatment. A storage period of 56 days showed that HHP and heat pasteurization had similar results in terms of pH and color. However, HHP treated samples had lower bitterness and protein sensitivity and higher chill haze values than the heat pasteurized samples which indicates HHP treatment had a positive effect on bitterness and protein sensitivity at the end of the storage period. The microbiological stability of HHP treated beers was comparable with heat-treated beers, and the development of both lactic and acetic acid bacteria was inhibited for 56 days of storage. Unfiltered beer samples had 7. 48, 7.15 and 2.64 log10cfu/ml of total yeasts, total aerobic and lactic acid bacteria counts, respectively. No colony formation of lactic acid bacteria was observed when the samples were pressurized at pressures equal to or higher than 300 MPa at 10°C and 20°C for 5 and 10 min. Total aerobic and total yeasts counts demonstrated more than 6 and 7 log-cycle reduction when pressurized at 350 MPa at 10°C and 20°C for 10 min, respectively. Heat treatment gave similar results in terms of log reductions as HHP.

Subject Keywords

Beer., Beer industry, Hydrostatics

URI

http://etd.lib.metu.edu.tr/upload/1098656/index.pdf
https://hdl.handle.net/11511/13704

Collections

Graduate School of Natural and Applied Sciences, Thesis