Influence of Lipids in the Generation of Phenylacetaldehyde in Wort-Related Model Systems

Abstract

The effect of lipids on the formation of the Strecker aldehyde phenylacetaldehyde during wort boiling was studied to determine the role that small changes in the lipid content of the wort have in the production of significant flavor compounds in beer. Wort was treated with 0-2.77 mmol per liter of glucose, linoleic acid, or 2,4-decadienal and heated at 60-98 degrees C for 1 h. After this time, the amount of the Strecker aldehyde phenylacetaldehyde increased in the samples treated with linoleic acid or decadienal but not in the samples treated with glucose. Thus, the amount of phenylacetaldehyde produced in the presence of linoleic acid was 1.1-2.5 times the amount of the Strecker aldehyde produced in the control wort, and this amount increased to 3.6-4.6 times when decadienal was employed. The higher reactivity of decadienal than linoleic acid for this reaction decreased with temperature and was related to the oxidation of linoleic acid that occurred to a higher extent at higher temperatures. The above results suggest that lipids can contribute to the formation of Strecker aldehydes during wort boiling and that changes in the lipid content of the wort will produce significant changes in the formation of Strecker aldehydes in addition to other well-known consequences in beer quality and yeast metabolism. On the other hand, because of the high glucose content in wort, small changes in its content are not expected to affect the amount of Strecker aldehydes produced.

A Review on the Source of Lipids and Their Interactions during Beer Fermentation that Affect Beer Quality

“…The presence of lipids and fatty acids may also interfere with malting properties. For example, phospholipids raise the gelatinization temperature of starch granules which interferes with the malt extraction process [22][23][24]. Therefore, it is plausible to assume brewers may use higher temperatures or increase the heating time to increase the starch extraction process, which also increases the amount of lipids extracted [22][23][24].…”

“…One example of this is the presence of trans-2-nonenal, one of the more commonly recognized flavour compounds derived from lipid oxidation possessing a flavour threshold of 0.1 µg/L [18,22,28,36]. Temperature, sunlight exposure and storage time are the prime factors in the production of stale-flavoured breakdown products [18,24,28]. Moreover, some authors report the contribution of non-oxidised lipids, lipid derived free radicals and lipid oxidation products on the formation of Strecker aldehydes such as benzaldehyde, 2-methylpropanal and methional [18,23,24,28].…”

“…Temperature, sunlight exposure and storage time are the prime factors in the production of stale-flavoured breakdown products [18,24,28]. Moreover, some authors report the contribution of non-oxidised lipids, lipid derived free radicals and lipid oxidation products on the formation of Strecker aldehydes such as benzaldehyde, 2-methylpropanal and methional [18,23,24,28]. The ratio between unsaturated and saturated fatty acids is associated with the gushing phenomenon, with unsaturated fatty acids acting as gushing-suppressors and saturated fatty acids acting as gushing-promoters [18,23,24,28,37,38].…”

Metabolic engineering of Escherichia coli to high efficient synthesis phenylacetic acid from phenylalanine

“…Hence, our study suggests that AldH may be a efficient phenylacetaldehyde dehydrogenase for oxidation of phenylacetaldehyde to PAA. On the other hand, the peak of PAA is relatively low in GC/MS map with a titer of 49.5 ± 1.27 mg/L (Table 3), which means it is possible that phenylpyruvate from glucose is relatively low in expanded shikimate pathway (Gallardo et al 2008). Hence we need to find another way to produce more phenylpyruvate, thus to get higher production of PAA.

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Egg yolk phospholipids: a functional food material to generate deep‐fat frying odorants

“…The small increase in 3-methylbutanal, and a similar trend for the other Strecker aldehydes, is due to the participation of unsaturated lipid-derived compounds in the Strecker degradation. 29 The parallel formation of -aminoketones may also promote the formation of pyrazines. This increase is observed for four of the five pyrazines detected.…”