In the brewing industry, barley malt is often partially replaced with adjuncts (unmalted barley, wheat, rice, sorghum and corn in different forms). It is crucial, however, to preserve constant quality in the beer to meet the expectations of consumers. In this work, how the addition of corn grist (10 and 20%) influences the quality of wort and beer was examined. The following parameters were analysed: wort colour, dimethyl sulphide (DMS) and protein content, non-fermentable extract, extract drop during fermentation, alcohol content and the attenuation level of the beer, together with filtration performance. The samples (all-malt, and adjunct at 10 and 20% corn grist) were industrial worts and the beers produced in a commercial brewery (3000 hL fermentation tanks). The application of 10 and 20% corn grist had an effect on the wort colour, making it slightly lighter (11.1 and 10.5°EBC, respectively) than the reference barley malt wort (12.2°EBC). The free amino nitrogen level, DMS and nonfermentable extract were significantly lower in the worts produced with the adjunct; the alcohol content and attenuation levels were higher in the beers produced with adjunct. The use of corn grist, at the level of up to 20% of total load, appears to affect some of the technological aspects of wort and beer production, but it does not significantly influence the final product characteristics.

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Lactic acid bacteria have long been used in brewing to acidify mash or wort and in the production of traditional sour beer styles (Lambic, Gueuze) using spontaneous fermentation. This approach is time consuming (some sour beers are matured for three years to obtain the appropriate flavour), so many brewers choose a faster approach using mixed cultures (yeast and bacteria). In this study, the influence of the pitching sequence of bacteria and yeast on the fermentation process was evaluated (by rate of fermentation and acidification, attenuation degree and ethanol concentration). The trials were performed using three procedures: (i) the addition of bacteria followed by the yeast; (ii) the addition of the yeast followed by the bacteria and (iii) the simultaneous addition of yeast and bacteria. In each trial the following time intervals were applied: 24, 48 and 72 h. Weight loss of samples and drop in pH were measured daily, and ethanol content, real extract and lactic acid concentration measured at the end of the process. It was shown that the order of addition of yeast and bacteria determines the success of the lactic acid fermentation. The appropriate yield of lactic acid (ca. 6 g/L) and the drop in pH (<3.6) can be achieved by inoculating the bacteria prior to the inoculation of yeast. When yeast was pitched before the bacteria, the lactic acid content was ca. 2 g/L and pH was 3.9–4.2. © 2019 The Institute of Brewing & Distilling

The ionic composition of brewer's wort depends on the raw materials and processing employed. The macroelement content is usually sufficient for yeast, but some of the microelements (mainly zinc) often need to be supplemented to the wort. Wheat malt is used as an adjunct in the production of beer, replacing up to 60% of barley malt. In this study, the effect of replacing barley malt with wheat malt on the concentration of magnesium, manganese, iron and zinc ions in brewer's wort was investigated. The ionic content of both the raw materials and by-products were analysed. Similar amounts of magnesium ions were found in wheat malt and barley malt, whereas, manganese, zinc and iron were more abundant in the wheat malt. Nevertheless, wheat malt did not cause a significant change in ion concentration in the first wort (except for magnesium; its content decreased). The ionic content in the spent grains increased owing to wheat malt addition; the concentration of ions in the wort decreased after wort boiling (Mn 2+ and Fe) or remained unaffected (Mg 2+ and Zn 2+). It was concluded that the ionic composition of the wort depends mainly on the removal rate of ions from the wort during mash filtration and hot trub separation, rather than on the actual amount of ions in the raw materials.

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