EBC Units Research Articles

Sensory and Instrumental Flavour Analysis of Wort Brewed with Dark Specialty Malts

In order to explore the flavour produced by dark specialty malts, wort samples were brewed with different malts and evaluated by sensory and instrumental analysis. With increasing wort colour, a trained tasting panel detected more intense bitter and burnt flavours, whereas sweet and husky flavour notes decreased. Conversely, caramel and bread-like flavour attributes had a maximal intensity for the intermediate wort colours. Tasting of 20 EBC worts indicated that the flavour profile was significantly affected not only by malt level and malt colour but also by malt origin. Furthermore, the darkest caramel malt (480 EBC units) was found to contain most Maillard aldehydes as determined by the reaction with thiobarbituric acid. Similarly, other intermediate products of the Maillard reaction such as acetic acid, diacetyl and 2,3-pentanedione were found to arise in a higher concentration in dark caramel malts (220–480 EBC units) than in roasted malt (1200 EBC units). Dynamic headspace GC/MS further revealed that brewing with dark specialty malts considerably increased the level of 3-methylbutanal, its aldol condensation product (2-isopropyl-5-methyl-2-hexenal) and heterocyclic Maillard compounds. In contrast, dark malts drastically reduced the amount of hexanal in wort. By means of HPLC, it was established that only extreme roasting temperatures lead to the thermal degradation of ferulic acid to 4-vinylguaiacol in malt.

Studies on the Effects of Common Process Variables on the Colloidal Stability of Beer

The effect of simple changes in process variables on the colloidal stability of beer was examined. Lager beers were stabilized using silica hydrogel (SHG) at 25–125 g/hl or polyvinylpolypyrrolidone (PVPP) at 10–50 g/hl. The effect of storage time (up to six days) and storage temperature (0 and 4°C), before stabilization and filtration, on the resultant colloidal stability of the beers was examined. The results were used to optimize the stabilization process with respect to sorbent dosage rate and beer storage time. Haze precursors were measured using the standard rapid assays: tannoids, total polyphenols, total flavanols, sensitive proteins, and alcohol-chill haze. Colloidal shelf life was measured as the time taken to reach a total haze of 2 EBC units in weeks at 37°C or months (28 days) at 18°C. Colloidal shelf life was directly proportional to sorbent dosage rate for both SHG and PVPP. The rapid assays were poor predictors of beer shelf life but were effective monitors of the stabilization process. The optimum storage time examined for lager beer before filtration was three days. Increasing the storage temperature from 0 to 4°C could be compensated for, in terms of measured colloidal shelf life, by increased stabilizer dosage rate.

SPECTROPHOTOMETRIC DETERMINATION OF MALT COLOUR

The International Method for the determination of the colour of beer has been tested by members of the Analysis Committee of the European Brewery Convention on samples of wort produced from a laboratory extract of malt using methods EBC 4.4 and EBC 4.4.5. The method, which relies on the spectrophotometric determination of colour at 430 nm, on clarified worts, is recommended as the designated reference method in place of the current visual method using EBC colour discs. The change will take effect from 1st January 1996. It was judged that precision values were dependent on the intensity of the colour of the sample over the range 3.6 to 25.3 EBC units. Repeatability (r 95 ) and Reproducibility (R 95 ) values of r 95 = 0.18Mean - 0.28 and R 95 = 0.13Mean + 0.46 were obtained over this range.

Improved brewing and preservation of pito, a nigerian alcoholic beverage from maize

AbstractA controlled brew of pito was produced and compared with a native brew. The former contained a higher alcohol content than the latter brew and was brighter in colour (13 as against 18.5 EBC units) thus making it more attractive. Of various heat and chemical preservative treatments used to prolong the shelf life of both products, pasteurization at 75°C for 30 min. and treatment with sorbic acid at a concentration of 5% were best able to arrest microbial proliferation in the bottled products during a 4 week storage period.