Abstract
Lipids are an important group of compounds affecting yeast metabolism
and the physico-chemical properties of beer.In the present study the role of
lipids in brewing was studied in laboratory and pilot scale.The analysis of
total fatty acid content of wort was considered as a good method for
controlling the separation processes during wort production and for evaluating
the quality of finished wort.High concentrations of lipids in wort
accelerated fermentation, but increased the loss of bitter substances and
decreased the foam stability and the filtrability of beer.If the amount of
lipids in wort was too small, the fermentation slowed down and off-flavours
occurred.Amounts of fatty acids recommended on the basis of this work are 50 -
100 mg/l in the copper wort and 10 - 20 mg/l in the finished wort.The
separation of trub was studied at different temperatures and the removal of
trub was most effective at 60 °C.Yeast was enriched with lipids by supplying
fatty acids in the wort or by propagating the yeast aerobically.Unsaturated
fatty acids incorporated into the cells and into the complex lipids of yeast.
They resulted in a reduction of the amount of medium chain length fatty acids
in yeast and in beer, increased the synthesis of saturated acids by yeast and
decreased the level of esters produced in beer fermentation.Unsaturated fatty
acids also decreased the amount of squalene and increased the amount of
sterols in yeast.In aerobically grown yeast cells the amounts of sterols and
palmitoleic and oleic acids were highly increased compared with anaerobic
cells.The greatest difference in the percentage of unsaturated acids between
aerobic and anaerobic cells occurred in sterol esters.Traditional, anaerobic
pitching yeast was replaced with aerobically propagated yeast, which was rich
in sterols and unsaturated fatty acids.A significant reduction in fermentation
time and in ester production was achieved.The advantages of aerobically
propagated yeast are most noticeable when worts of high specific gravity are
fermented.No aeration of wort is required and the risk of oxidation of flavour
compounds is eliminated.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
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Award date | 29 Oct 1983 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-1877-2 |
Publication status | Published - 1983 |
MoE publication type | G5 Doctoral dissertation (article) |