engleski

The influence of partial substitution of malt with maize grits and wheat on quality parameters and colloidal sability of lager beer

The aim of this work was to investigate the influence of wheat on quality indicators and colloidal stability of lager beer, considering the new requirements on minimal shell life (MSL). The fraction of added wheat was common for the wheat and maize grits combination used in the production of this beer. The production of beer I (50% malt, 34% maize grits, 16% wheat) and beer II (100% malt) was monitored. The same standard process with two mashes (two mash decoction) was used for both beers. Raw materials, laboratory and industrial worts, freshly bottled beers, and beers in storage at room temperature over a period of 210 days, were analyzed. The composition of raw materials did not deviate beyond the usual ranges. Wheat gives mashes characterized by longer saccharification and lautering times compared to malt and maize grits, and by similar viscosity as malt. Wheat also raises the fraction of high-molecular proteins, and reduces the fraction of assimilating (in addition to formol and a-amino) nitrogen in wort. Worts for beer I had less color intensity, viscosity and turbidity compared to worts for beer II. Consequently, these parameters were also considerably decreased in the resulting beers as compared to beers obtained from pure malt. Analyses of fresh rack beers indicated a great similarity in chemical composition, especially in the proportions of high-, medium-, and low-molecular protein fractions. Considering its portion of grits, wheat is the most significant contributor of high-molecular proteins to beer. Warm-cold and total haze tests showed that, even with comparable absolute shares of major haze precursors (total polyphenols and high-molecular proteins), the malted wheat beers are substantially less resistant to heat-induced haze, in comparison with both the beers from pure malt and the referent, colloidally stabilized beer. The tests of chemically induced haze (tannic acid-TA, gliadin-GI, gelatine-GL, polyphenol oxidase-PO) point to TA as the agent producing the most intense turbidity of fastest onset. Beer I was less resistant to TA-induced haze compared to both beer II and the referent beer. A greater affinity to haze induction by GI was determined for beer II which had a higher content of polyphenols. All three beers contained more haze-active proteins than haze-active polyphenols. The tests of heat-induced haze provide a more accurate information on MSL of beer. The results of monitoring colloidal stability of beer in storage revealed a satisfactory clarity of beer I only during the first three months, reaching the marginal value by the end of the period. At the same time, beer II had an adequate clarity during six months of storage.

unmalted wheat; colloidal stability; mimimum shelf life of beer

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