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Received: 21 February 2020
Received in revised form: 1 April 2020
Accepted: 4 April 2020
Keywords
haze-active protein, relative molecular weight, haze stability, storage temperature, barley beer, wheat beer
Abstract
The objective of the present work was to investigate the haze-active (HA) protein and its relationship with the turbidity in commercial clear barley beer (BB) and cloudy wheat beer (WB) stored at 0 - 20°C for seven days. It was found that the maximum turbidity occurred at 0 or 5°C in samples, and the turbidity had a significantly negative correlation with temperature. Hence, it was recommended to store BB at 10 or 15°C to avoid the haze formation while WB at 0 or 5°C to promote a stable and high turbidity value. Furthermore, HA protein was extracted by silica, whose relative molecular weight (Mr) was determined by HPSEC and divided into four fractions. Mr of HA protein in BB was higher than that in WB in each fraction. For the correlation of turbidity and different fractions of HA protein, there were similarities between BB and WB. The content of low Mr fractions consisting of fraction II (8.34 - 13.92 kDa) in BB or fraction I&II (< 7 kDa) in WB had positive influences on turbidity, while high Mr portion including fraction III (38.08 - 45.91 kDa) in BB or fraction IV (59.28 kDa) in WB showed negative effects on turbidity.
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Introduction
Beer is one of the most popular drinks all over the world, and the colloidal stability ofbeer has become a critical issue for transportation and warehousing. Generally, the haze formation may be promoted when beer undergoes unavoidable long distance transportation or is exposed to the complex temperature environment (Speers etal., 2003; He etal., 2012). Consequently, it is necessary to identify the correlation between temperature and turbidity of beer, and the influence of different fractions in HA protein to avoid the stability problems during storage.
Haze is an important appearance characteristic reflecting the quality of beer. Therefore, turbidity is very important for brewers, because it is the first visual quality indication of beer to consumers (Iimure et al., 2012). In the market, most BBs are crystal clear with turbidities less than 2 EBC (European Brewery Convention), since haze...