Search: Grist fractions

The extract yield in the brewhouse is highly dependent on optimal milling of the malt or other grain. The composition of the brewery grist should therefore be monitored on a regular basis.

The sieve analysis is performed on a sample of brewery grist of a known weight with a shaking device containing a set of sieves (according to DIN ISO 3310-1 specifications or a Pfungstädter plansifter sieving device).

Malt is ground between two horizontally positioned, grooved discs. The lower disc is driven by an electric motor and rotates at approx. 1500 rpm; the upper disc is fixed and therefore does not move. During the milling process, the malt migrates from the center of the discs to the outer edge, where the grist falls through an outlet spout into a grist beaker.

The gap between the discs can be adjusted by turning a socket head screw on a calibrated ring bearing scale markings. The scale on the calibrated ring ranges from 0 to 20, with each scale division corresponding to a gap between the discs of 0.10 mm. Each scale division is subdivided into five smaller divisions; each of the smaller marks is equivalent to 0.02 mm. Two gap adjusting rings ensure reproducible mill settings.

A reliable sampling method for whole hops and hop products is a prerequisite for obtaining suitable material for analysis. The effort involved in collecting the sample depends upon how uniform the hop product is.

Xanthohumol and isoxanthohumol are dissolved with acetonitrile from the sample and following separation, are determined using a Nucleodur C18 column and UV detection.

Inductively coupled plasma optical emission spectroscopy (ICP-OES) is a fast and reliable method for the laboratory analysis of metals. Inductively coupled plasma (ICP), a high frequency field of ionized gas, serves as a medium for atomizing and exciting the substances found in samples. Liquid, dissolved or aerosol samples are injected into the ionized gas stream. In emission spectroscopy, ICP can be used in conjunction with a number of optical and electronic systems either simultaneously or sequentially in multi-element spectrometers. In the plasma, the atoms and ions are excited to a higher energy state bringing about the emission of electromagnetic radiation (light), primarily in the ultraviolet and visible region of the spectrum. Metals ordinarily occur as ions in the temperature range typical for ICP of 6000 to 10000 K; however, non-metals and metalloids are only partially ionized.

ICP-OES operates within a very wide range. This usually encompasses six orders of magnitude in concentrations smaller than μg/l up to g/l, depending upon the element and the concentrations used for the set of analysis data. With ICP-OES, beer and wort can also be analyzed without prior processing of the samples, in contrast to AAS. Methods for determining the following in beer and wort will be described below: Al, B, Ba, Ca, Co, Cu, Fe, K, Mg, Mn, Mo, Na, P, Si, Sr, Sn and Zn.

Volatile aroma compounds are driven out of the sample through steam distillation. The ethanol distillate is adjusted to be alkaline and saturated with NaCl. The extraction of the aroma compounds is performed by shaking out with dichloromethane and the phases separated by centrifuging. The organic phase is further concentrated in a stream of nitrogen gas. An ammonia solution is added to remove the acids, because the acids would co-elute, thus preventing quantification of the target substances.