Difference between revisions of "Talk:Dimethyl sulfides"

DIMETHYL SULFIDE (DMS)

Table II lists types of beers in order of their perceived threshold of DMS. Those with the lowest thresholds are most likely to have off tastes at excessive DMS levels.

The perceived flavor intensity can be expressed as follows where P is the perceived flavor intensity, C is a concentration of DMS in beer, and T is the taste threshold in beer:2

P = (beer style constant) = ( C/T ) n

The level of DMS in unmalted barley, wheat, rye and corn syrup is negligible.

The amount of DMS in corn grits has been reported to be approximately 0.4 ppb.1

Essential oils of hops contain small levels of DMS but are steam stripped from the boiling wort.5

Some typical levels of DMS and SMM in different varieties of malt are shown in Table IV.4

The level of SMM in malt is responsible for the DMS level in wort. During mashing the SMM, DMS and very soluble DMSO are brought into solution. No SMM is hydrolized to DMS at this time.

TABLE II PERCEIVED THRESHOLD of DMS on VARIOUS BEERS Lagers (lowest):

1. Low adjunct beers with low gravities or diluted flavor.
2. High adjunct beers with corn grits
3. High adjunct beers with other adjuncts
4. Low to medium gravity (1.040-1.048) beers - all malt
5. All malt German or higher gravity, light colored - flavored beers
6. Amber - dark flavorful beers

Ales (highest):

1. British light ales
2. American or British amber or dark ales
3. Stouts or strong flavored beers

TABLE III DMS and SMM LEVELS in TYPICAL MALTED BARLEY KERNEL MALT KERNEL DMS (ppb) SMM (ppb) 1) Husk 0.81 0.67 2) Starchy Endosperm 1.5 1.2 3) Embryo and Scutellum 5.9 2.2 4) Crospire 15.0 14.0

• (Biosynthesis activity 2-4)

TABLE IV REPORTED DMS and SMM LEVELS in DIFFERENT MALT VARIETIES MALT KERNEL DMS (ppb) SMM (ppb) SMM (ppb)

• Larken 12.9 12.0 24.9
  • Proctor, Pale Ale 7.1 3.7 10.8
  • Klages (2 row) 9.2 2.0 11.2
• U.S. Malt: (high modification, low kilning temperature)
  • British Malt: (moderate modification, higher kilning temperature)

An American maltster reported that typical combined DMS/SMM levels in North American brewers malt averaged 10-15 ppb. But during years of high protein levels, for example the '88 drought, levels may approach 20 ppb.

TABLE V SMM LEVELS in MALT vs. DMS in FINISHED LAGER BEER MALT BEER % INCREASE

SMM (ppb) DMS (ppb) (SMM to DMS) 3.2 38.0 1090 4.6 61.0 1200 6.0 78.0 1200 8.4 98.0 1070

TABLE VI REACTIONS CONTRIBUTING TO DMS FORMATION

(CH3)2S-CH2-CH2-CH(NH2)-COOH(CH3)2 + OH >(CH3)2S<(oxidation/reduction)>(CH3)2S=O S-Methyl methionine Dimethyl sulfide Dimethyl Sulfoxide SMM DMS DMSO

Infromation from http://www.abtonline.com