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Sản xuất bia nồng độ cao là một kỹ thuật quan điểm để tăng năng lực sản xuất bia mà không có chi phí vốn đáng kể. Tại Việt Nam, sản xuất bia trọng lực cao đã được thực hiện trong một số nhà máy bia, lực hấp dẫn cụ thể wort 16oPlato (Pt). Trong bài báo này, quá trình lên men của wort 16-22oPt đã được kiểm tra.Các kết quả thu được cho thấy lực hấp dẫn cụ thể của wort, còn thời gian lên men và nội dung chất nền còn lại trong bia màu xanh lá cây. | Science Technology Development Vol 10 No.06 - 2007 IMPROVEMENT OF FERMENTATION PERFORMANCE IN HIGH GRAVITY BREWING Le Van Viet Man Pham Quoc Chuong University of Technology VNU-HCM Manuscript received on August 05th 2005 Manuscript received on July 10th 2007 ABSTRACT High gravity brewing is a perspective technique for increasing brewing capacity without significant capital expenditure. In Vietnam high gravity brewing has been carried out in some breweries the specific gravity of wort is up to 16oPlato Pt . In this paper fermentation of the 16-22oPt wort was examined. The obtained results showed that the higher the specific gravity of wort the longer the fermentation time and the higher the residual substrate content in the green beer. The principal reason was due to high ratio of C N content in wort. Then some nitrogen sources were alternatively added to the 22oPt wort. It was showed that the fermentation was significantly accelerated and the alcohol content in the green beer increased. Yeast extract was considered as a suitable nitrogen source for supplementation in high gravity brewing. For the 22 Pt wort the optimal content of supplementing yeast extract is 90mgN litre. 1. INTRODUCTION Many breweries throughout the world are embracing high gravity brewing as part of their production strategy for increasing brewing capacity without significant capital expenditure. It is one of many techniques that are being employed for process intensification of primary fermentation and maturation in brewing Stewart G.G. 2000 . In Vietnam up to now high gravity brewing has been carried out in some breweries such as Saigon brewery Foster Tien giang brewery. The specific gravity of wort is up to 16oPt. Attempts to ferment worts with higher specific gravity have proven to be difficult largely because of yeast viability slow and incomplete fermentation. Some results show that both ethanol toxicity and high osmotic pressure levels have been implicated as the limiting factors Casey .
