Influences of Key Components and Surface Modifications on Beer Lacing

Abstract

Beer is one of the most favorable alcoholic beverages and has a large consumption in the world. However, there are fewer beer consumers who perceive the lacing character after drinking. Four different concentrations (25 mg/L, 50 mg/L, 75 mg/L and 100 mg/L) of iso-α-acid and two levels (0.3% and 0.15%, w/w) of protein content were investigated towards lacing property on modified hydrophilic and hydrophobic glassware. Lacing area, lacing index and connectivity of laced foam were measured and two-way ANOVA was conducted to each result. There was no linear correlations found in each factor for every indication, but the statistical analysis showed that there was significant difference (p<0.05) among iso-α-acid concentrations on hydrophilic surface in terms of lacing area, and it is also the same case on both glass surface properties as for lacing index, in addition protein content influenced the value of lacing index on hydrophobic surface as well. Perimeter Maybe perimeter of lacing fragments was calculated to analyze lacing connectivity. It also showed the significant difference (p<0.05) over iso-α-acid concentrations. The interaction effect of protein and iso-α-acid also affect the results significantly. However, the specific interaction between these two factors needs more investigations. Independence of lacing pattern on hydrophilic and hydrophobic glass surface was demonstrated from student t-test according to perimeters. Moreover, the contact angle of each sample on hydrophilic and hydrophobic glass slides was discussed in detail. This thesis provides some new viewpoints for the evaluation of beer from beer lacing property and interesting results obtained in this work are important for comprehensive understanding the nature of foam and lacing connecting to the composition of beer and the glassware surface property.

Popular Abstract

Beer is the best seller among alcoholic beverages in the world. Now summer is coming and who doesn’t love beer?! Statistics showed the amount of beer consumed in 2015 was four times more than other drinks such as spirits, wine and premix. As we know that we can evaluate wine with its lacing on glass. However, there are fewer consumers who know how to evaluate beer by its appearance. A beautiful layer of foam is sitting on top when we pour beer, and the remaining foam sticking or adhering on glass is called “lacing” or “cling” after we drink it to the bottom. People perceive lacing differently. On the one hand, some people possibly think it is an unpleasant visual experience which might the result of dirty glass. On the other hand, some people prefer to have a favorable amount of lacing, especially some professional beer evaluators. it is the foam and/or lacing, which is relative to the quality of beer, some beer consumers appreciate to have a favorable amount of lacing from beer and a professional beer evaluator will evaluate beer taking lacing performance into a count.
Thus, the factors affecting lacing formation are important and need to be investigated, which is the beer composition, ambient temperature, pouring height and angle. And the composition of beer is the key factor among them. Herein, the amount of protein and iso-α-acid contained in the beer together with the surface property of glass were studied over the effect on lacing. Proteins in barley are able to foam. Iso-α-acid is a substance derived from hop flower which adds the typical bitter taste to beer, which helps to promote the stability of foam due to its chemical structure and the interaction with proteins. Glass containers were modified to have water-like and water-hate properties, which will influence the beer foam spreading and thus affect the lacing properties.
Spendrups premium lager (2.8% alcohol by volume) manufactured by Spendrups Bryggeri AB from Sweden was selected and used as protein sources. Iso-α-acid was extracted from hop at lab. A kitchen appliance, cream whipper, was utilized as foam generator which makes homogeneous foam and output volume is controllable. In order to get full glass surface of lacing, once the foam was input into glass container, liquid was drained out by a tube from bottom of container. Three parameters of lacing area, lacing index and connectivity of lacing were examined and used to describe the lacing property, e.g. lacing amount and pattern. Some interesting results were obtained as follows.
(1) Lacing area (%) was analyzed based on pictures of laced foam. Lacing on water-like glass was more sensitive to the concentration of iso-α-acid while they are not proportionally correlated. On water-hate glass, lacing area kept a constant value with less fluctuation, which cannot be distinguished among each composition.
(2) Lacing indices were calculated according to the absorbance of remaining laced foam. Both protein and iso-α-acid concentrations significantly (p<0.05) influenced the value of lacing index on water-hate glass. Interaction effect of protein and iso-α-acid also cannot be negligible.
(3) Perimeter of laced foam was calculated as for connectivity of lacing. Perimeter is the outline of one independent fragment. Therefore the bigger perimeter shows the more independent laced foam other than a big area of connected lacing. It demonstrated the perimeter on water-hate glass was greater than that on the water-like glass. In this way, lacing on water-hate glass was more fractured and independent. While lacing on water-like glass was more intact and continued. It is persuasive to prove the difference in characteristic between lacing generated on water-hate and water-like container.
To conclude, even though these parameters didn’t show a linear correlation with the increasing amount of iso-α-acid, but their effect on lacing is no doubt. Higher protein and iso-α-acid content in beer tend to have more laced foams but the interaction effect between two compounds affect the lacing negatively in most of the cases with highest concentration (100 mg/L) of iso-α-acid. On water-hate glass, lacing pattern is highly dispersed with small fractions, while it is relatively continued and intact on the water-like glass. There are several important parameters regarding to the lacing, herein they need to be further investigated in detail. From the consumer perspective, it is the time starts to talk about your favorite beer with its characteristic lacing!

• author: Wang, Junjing
• supervisor: Yi Lu; Björn Bergenståhl
• organization: Food Technology and Nutrition (M.Sc.)
• course: KLGM01 20171
• year: 2017
• type: H2 - Master's Degree (Two Years)
• subject: Agriculture and Food Sciences; Technology and Engineering
• keywords: image analysis, protein, iso-α-acid, Beer, lacing, hydrophilic and hydrophobic, food technology, livsmedelsteknologi
• language: English
• id: 8921851
• date added to LUP: 2017-08-18 09:23:31
• date last changed: 2017-08-18 09:23:31