Effects of Operating Conditions during Low-Alcohol Beer Production

Article pubs.acs.org/JAFC

Effects of Operating Conditions during Low-Alcohol Beer Production by Osmotic Distillation Giovanni De Francesco,*,† Gary Freeman,‡ Eung Lee,‡ Ombretta Marconi,§ and Giuseppe Perretti† †

Department of Agricultural, Food and Environmental, University of Perugia, Via San Costanzo, 06126, Perugia, Italy Campden BRI, Coopers Hill Road, Nutfield, Surrey, RH1 4HY, United Kingdom § Italian Brewing Research Centre, University of Perugia, Via San Costanzo, 06126, Perugia, Italy ‡

ABSTRACT: Osmotic distillation (OD) is a membrane technology most commonly used for liquid concentration, but recently there has been an increased interest in ethanol removal from alcoholic beverages. The aim of this paper is to investigate the effect of the variation of some operating conditions (temperature, flow rate, type and amount of stripping solution), specifically in regard to the effect on quality and sensory properties of the dealcoholized beers. The results indicated that temperature and flow rate variation showed no significant effect, whereas stripping solution variation had substantial effects mainly in terms of the ethanol removed. A cost appraisal showed that the operating costs were high mainly because of the cost of the stripping water. However, it is important to consider the final stripping solution, which is slightly alcoholic and enriched in flavor. For this reason, it could be reused in the manufacture of beverages, for instance as high gravity beer dilution water. KEYWORDS: Beer, beverages, dealcoholization, low-alcohol beer, osmotic distillation

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INTRODUCTION The production of low-alcoholic beverages (or low-alcohol fermented beverages, typically defined as containing less than 1.2% v/v) is an established option for a food industry looking for alternatives to the soft drink. Low-alcohol beer is still a small percentage of the output of the brewing industry, but recently there is a significant growth of this product, reflecting the global trend for a perceived healthier lifestyle.1,2 The current increasing demand for low-alcohol and alcohol-free beers is attributable to various factors such as health, diet, safety, or prohibition of alcohol consumption caused by labor protection laws. There are also countries (such as Islamic countries) where alcohol consumption is completely prohibited by law.2,3 Lowalcohol and alcohol-free beers are also recommended for specific groups of people such as pregnant women, sporting professionals, people with cardiovascular and hepatic pathologies, and medicated people.4−8 The legal definition of low-alcohol and alcohol-free beer varies from one country to another. For instance, Italian regulations refer to nonalcoholic beer as a product having 3−8 degrees Plato (g of extract/100 g of wort) with an alcoholic content less than 1.2% v/v. In Europe, a nonalcoholic beer or alcohol-free beer will usually have a final alcohol by volume content lower than 0.5% v/v, whereas a low-alcohol beer ethanol content is between 0.5 and 1.2% v/v.9 A large number of factors influence beer characteristics during production of low-alcohol or alcohol-free such as variety of barley and the malting process, temperature and pH during mashing, sparging, variety of hops added, and storage conditions.10 Therefore, the main challenge in the production of low-alcohol and alcoholfree beers is to manufacture a product that resembles as far as possible regular beer, which is very difficult to realize. It is for these reasons that low-alcohol and alcohol-reduced beverages have received increased technological and economic attention.11 © 2014 American Chemical Society

There are two main strategies to produce reduced alcohol beer. First, there are physical methods such as dialysis,12 reverse osmosis,13 vacuum rectification and evaporation, 14 or spinning cone column distillation.15 Second, there are biological methods such as controlled (suppressed) alcohol formation1 and use of special yeasts.16 The most common way to make nonalcoholic beer is arrested fermentation in order to keep the ethanol content very low.17 This method is the most simple and uses the same resources as does a standard beer fermentation. However, it has a drawback related to beer quality, mainly caused by the lack of reduction in concentration of certain wort compounds and by a poor development of important beer flavors. Thus, the final product presents a typical worty flavor and a thin mouthfeel that is very different from standard alcoholic beers.18−20 The physical methods also have advantages and disadvantages. The most important advantages are the possibility of reaching an ethanol content of 0.05% v/v, and some technologies employ low temperature and low pressure during dealcoholization. The most important disadvantages are the high operating costs, loss of volatile compounds, capital expenditure on the specialized process equipment, and a risk of thermal damage to delicate compounds. Relevant organoleptic and sensory characteristics of the nonalcoholic beer include flavor, color, foaming properties, body, viscosity, mouthfeel, and colloidal stability, much the same as for normal beer.11 Beer is a complex alcoholic beverage as it contains many organic compounds that contribute to its taste, aroma, and mouthfeel. However, it must be pointed out that it is well understood that the alcohol has a significant impact on the beer Received: Revised: Accepted: Published: 3279

December March 12, March 12, March 12,

12, 2013 2014 2014 2014

dx.doi.org/10.1021/jf405490x | J. Agric. Food Chem. 2014, 62, 3279−3286

Journal of Agricultural and Food Chemistry

Article

Figure 1. Model of the dealcoholization lab unit used (feed, beer tank; P1 and P2 peristaltic pumps; MC, membrane contactor; CS, cooling system; SS, stripping solution tank; V1−V6; manual valves; T, temperature controllers; P1−P6, pressure gauges.

flavor. Therefore, low-alcohol or alcohol-free beers produced by the technologies applied up to now will at best reach only approximately the high sensory quality of a “normal” beer. Nevertheless, these beers make up distinctive, high-quality products, which have earned significance in the market.21 The sensory quality of beer depends on the complex balance of flavor-active components. In many cases, the dealcoholization could negatively affect the organoleptic quality of beer, leading in some cases to the unacceptability of the product. The low-alcohol and alcohol-free beers are required to meet certain quality conditions regarding their stability and sensory features, which should be comparable to those of normal beers. It is likely that the sensory qualities of the beer will change over the course of the dealcoholization, where a loss of aroma, body, and flavor can be seen.22 A reduced foaming property (especially foam head retention) is another drawback. This issue is also related to the lack of ethanol, which improves foamability and foam stability in the range of 1−3.5% v/v.23 In any case, the addition of glycerol or other sugar alcohols can reinforce the foaming properties of beer.24,25 Principle of Osmotic Distillation. Osmotic distillation (OD) or evaporative pertraction (EP) is a membrane process used for removing ethanol from beverages, especially for wine partial dealcoholization. This membrane technology has been presented as a novel and promising technology to reduce the ethanol content in alcoholic beverages without unacceptably altering the organoleptic properties of the product.26,27 OD uses hydrophobic porous membrane contactors to provide the ethanol transfer from beer to stripping solution (usually water). In this process water and beer flow countercurrently. The mechanism is similar to membrane distillation,28 but in this case, the process is carried out at ambient temperature,26 in

which the partial pressure gradient due to the high relative volatility compared to water is the driving force for ethanol transport. Due to this mechanism the OD has also been defined “isothermal membrane distillation”29 and in some specific cases, such as dealcoholization, the term evaporative pertraction is more precise.30 OD is a form of dialysis, in which a liquid mixture containing a volatile component is contacted with a microporous, non-liquid-wettable membrane whose opposite surface is exposed to a second liquid phase capable of absorbing that component. The most important difference compared to more common liquid−liquid contacting processes (such as reverse osmosis) is the membrane’s composition, which is porous and hydrophobic and typically made of PTFE or polypropylene.31 The most important advantages of the membrane contactors are well-defined and constant interfacial area, high interfacial area in small volumes, small size and weight, no dispersion between phases, no need of phase separation downstream, no need to work with fluids of different densities, no flooding, loading, or foaming, wide range of operating flow-rates, flow-rates can be varied independently, and lower operating temperatures compared to distillation processes. The most important drawbacks are membrane fouling, pressure drop caused by the membrane unit, membrane lifetime, and a high stripping solution volume requirement.32−35 The transport mechanism of ethanol by OD process can be divided into three steps: (i) evaporation of ethanol at the membrane pores on the feed side, (ii) diffusion of ethanol vapor through the membrane pores, and (iii) condensation of ethanol vapor in the stripping solution at the membrane pore exit.36 The aim of this work was to investigate both theoretically and experimentally the effects of the different process parameters. The operating parameters which affect the 3280



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ethanol content, such as flow rate, system temperature, and types of stripping solutions, were investigated. Furthermore, the quality parameters (present gravity, pH, color, turbidity, total soluble nitrogen, CO2) and the losses of volatile compounds of the beer were also monitored.

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Experimental Conditions. The beer feed was maintained at 10, 15, or 20 °C in separate trials, in order to investigate the effect of temperature changing on separation efficiency. During these trials, the stripping water temperature was kept at 10 °C. Similarly, different amounts of stripping solution, 3, 4, 5, or 6 L were employed in separate trials, while the beer volume was 1 L for each trial. Furthermore, the effects of types of stripping solution, i.e. normal pure water and carbonated water, were investigated. Moreover, different flow rates of stripping solution were tested, namely 500 mL min−1 and 1 L min−1. Finally, different beer brands were employed to ascertain the effect of variations in e.g. membrane fouling, different volatile concentrations, etc. Membrane Cleaning. After dealcoholization, the membrane was cleaned by flowing filtered and deionized water in tubeside and in shellside without recycling for 15 min. Subsequently, a 0.5% (w/w) and 30 °C NaOH solution was circulated for 30 min. Finally, the system was rinsed with RO water without recycling for 10 min and then it was dried in both tube and shell side by using nitrogen gas for 20 min according to manufacturer cleaning guidelines.

MATERIALS AND METHODS

Alcoholic beers of five different commercial brands were obtained. The alcoholic beers contained between 3.5% and 5% v/v. The dealcoholization tests were carried out by a small pilot plant equipped with a polypropylene hollow fiber membrane contactor (Liqui-Cel, MiniModule 1.7 × 5.5, Membrana GmbH, Wuppertal, Germany) (Figure 1). The typical membrane surface area was 0.54 m2, with an approximate priming volume of 78 and 53 mL, for shellside and tubeside, respectively. For the first trials the membrane operating parameters were as follows: beer inlet pressure 0.3 bar gauge, beer outlet zero pressure (atmospheric), water inlet pressure 0.3 bar gauge, water outlet zero pressure, beer flow 500 mL min−1, and water flow 500 mL min−1. These parameters were subsequently adjusted in an experimental matrix to ascertain optimum process (below). The ethanol content of the beers and all quality parameters were determined in accordance with Analytica EBC.37 The aromatic profile of the beer and corresponding dealcoholized beer was analyzed by gas chromatography (Perkin-Elmer, Auto System XL, Waltham, MA). The chemical standards (acetaldehyde, npropanol, 2-methyl-1-butanol, 3-methyl-1-butanol, ethyl acetate, isoamyl acetate, ethyl hexanoate, diacetyl) used for the identification and quantification of the volatile compounds of interest were purchased from Sigma-Aldrich (Milwaukee, WI). The internal standard for the determination of aldehydes and vicinal diketones, 2chlorobenzaldehyde (Sigma-Aldrich, Milwaukee, WI), was prepared weekly in a solution of 5% ethanol with a concentration of 10 mg L−1. The internal standard for determination of ethanol, higher alcohols, and esters was 1-butanol (Sigma-Aldrich, Milwaukee, WI), which was prepared weekly in water with a concentration of 60 mg L−1. The gas chromatograph was equipped with an electron capture detector (ECD) for the analysis of vicinal diketones (diacetyl and 2,3pentanedione) and with a flame ionization detector (FID) for the analysis of the other volatile compounds.The separation column was a CP-WAX 57CB wall coated open tubular (WCOT) fused silica column (polyethylene glycol stationary phase, 60 m × 0.25 mm i.d. with 0.4 μm film thickness; Chrompack, Netherlands). Ten mL of the beer samples was added to 500 μL of internal standard 2chlorobenzaldehyde (10 mg L−1) and 1 mL of the internal standard 1-butanol (60 mg L−1) in a 20-mL glass vial, which was heated for 30 min at 60 °C and stirred at 250 rpm for 30 s of every minute in order to allow the volatilization and derivatization of the compounds of interest. The injection was performed by means of a 2.5-mL headspace syringe at 70 °C. The syringe was placed in the sample headspace to draw the volatile compounds and to inject them in the gas chromatograph. The injection volume was 1 mL. The front inlet temperature was 150 °C. The injection was in the splitless mode with the purge valve set at 20 mL min−1. Helium was the carrier gas at a flow rate of 1.1 mL min−1. The oven temperature program used was 34 °C for 2 min, followed by an increase of 45 °C min−1 up to 55 °C, the held for 8 min, then raised to 98 °C at 5 °C min−1, and finally increased to 150 °C at 45 °C min−1. The detector temperature was 200 °C. Experimental Section. A series of experiments was performed to ascertain optimum operation of the process. The feed and stripping solutions were fed into the module by peristaltic pumps. The process temperature was controlled by a water bath fitted with temperature controllers. Six pressure gauges for inlet and outlet were installed for monitoring the pressure of the feed and stripping solutions. During processes, the beer continuously circulated from a sealed container to the dealcoholization apparatus while water flowed counter-currently on the other side of the membrane (Figure 1). Beer ethanol content was monitored throughout the process until the target level was achieved.

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RESULTS AND DISCUSSION Different Stripping Solution Volumes. The effect of the different ratios of stripping solution (deaerated water) to beer

Figure 2. Percent of ethanol removed using different ratios of beer/ stripping solution (% of original amount) after 4 h processing. Values with different superscript letters are statistically different (P < 0.05).

Figure 3. Decrease in ethanol during dealcoholization using different ratios of beer/stripping solution. (B: beer; DW: deaerated water). Values with different superscript letters are statistically different (P < 0.05).

feed in terms of ethanol flow transfer rate (mL min−1) and in terms of percentage of ethanol removed (%) was measured. The different stripping solution volumes (3, 4, 5, and 6 L) noticeably influenced the percentage ethanol removed as shown in Figures 2 and 3. The matrix of experiments also included varying the feed beer temperature. The beer temperature (10 and 20 °C) did not significantly change the ethanol transfer rate and ethanol removed (Figure 3). Furthermore, Figure 3 shows that the process was essentially finished after 2 h; hence, it was 3281



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Table 1. Representative Volatile Compounds (mg L−1) and Loss Percentage (%) of Original and Dealcoholized Beer Using Different Ratios of Beer/Stripping Solutiona AA

EA

EH

IAA

n-prop

2-MB

3-MB

DA

4.94 ab 2.78 a 43 A 10.01 d 2.93 a 70 D 4.46 ab 55 C 5.34 b 46 B 7.61 c 3.80 ab 47 A

18.35 b 5.34 a 70 A 18.31 b 3.64 a 80 B 3.44 a 81 B 3.65 a 80 B 16.80 b 2.67 a 84 B

0.10 0.01 87 0.15 N.D.

1.91 d 0.47 bc 74 A 1.73 d 0.39 ab 77 A 0.29 ab 83 AB 0.25 ab 85 B 0.72 c 0.14 a 80 AB

8.55 f 1.96 b 77 B 7.38 e 1.48 b 79 B 1.17 ab 84 BC 0.93 a 87 C 6.79 e 3.74 44 A

9.61 e 2.24 c 76 AB 6.66 d 1.98 bc 70 A 1.40 abc 79 B 0.52 ab 92 C 5.46 d 0.34 a 93 C

49.53 f 12.85 d 74 A 52.22 g 10.10 c 80 B 9.90 c 81 B 7.75 b 85 C 41.57 e 5.14 a 87 C

0.03 a 0.01 a 27 A 0.02 a 0.02 a

beer brand lager beer brand A B (1 L, 10 °C); DW loss percentage (%) lager beer brand B B (1 L, 10 °C); DW loss percentage (%) B (1 L, 20 °C); DW loss percentage (%) B (1 L, 10 °C); DW loss percentage (%) lager beer brand C B (1 L, 10 °C); DW loss percentage (%)

(3 L, 10 °C)

(4 L, 10 °C) (4 L, 10 °C) (5 L, 10 °C)

(6 L, 10 °C)

N.D. N.D. 0.12 N.D.

0.03 a 0.01 a 27 A 0.01 a 0.07 a

a Acetaldehyde (AA), ethyl acetate (EA), ethyl hexanoate (EH), isoamylacetate (IAA), n-propanol (n-prop), 2-methylbutanol (2-MB), 3methylbutanol (3-MB), diacetyl (DA). B: beer; DW: deaerated water. N.D.: not detectable. Statistical analysis was performed separately. Values in the same column with different letters are statistically different (P < 0.05).

Table 2. Representative Parameters of Original and Dealcoholized Beer Using Different Ratios of Beer/Stripping Solutiona beer brand lager B (1 lager B (1 B (1 B (1 lager B (1

beer (brand A) L, 10 °C); DW beer (brand B) L, 10 °C); DW L, 20 °C); DW L, 10 °C); DW beer (brand C) L, 10 °C); DW

(3 L, 10 °C) (4 L, 10 °C) (4 L, 10 °C) (5 L, 10 °C) (6 L, 10 °C)

OG (°P) 10.73 b 3.86 a 11.25 b 3.81 a 4.21 a 3.89 a 10.94 b 3.22 a

RE (°P) 2.94 2.37 2.36 2.30 2.54 2.77 3.50 2.40

a a a a a a a a

AE (°P) 1.93 2.11 1.86 2.01 2.22 2.55 1.90 2.30

EtOH (% v/v)

a ab a a ab b a ab

4.53 1.06 5.00 0.88 0.93 0.79 4.81 0.51

e d g bc c b f a

pH 4.17 4.15 4.27 4.17 4.24 4.27 4.42 4.30

a a a a a ab b ab

color (EBC) 6.24 6.88 7.13 7.49 7.77 7.64 7.57 7.78

a b b b b b b b

TU (EBC) 0.85 2.54 0.71 1.78 1.07 0.91 0.65 0.92

a b a ab a a a a

TN (mg L−1) 492 518 521 546 535 534 549 569

ab ab b bc bc bc c c

CO2 (g L−1) 5.32 cd 0.3 b 5.57 d 0.19 ab 0.13 ab 0.44 b 5.23 d 0.36 ab

a

Original gravity (OG), real extract (RE), apparent extract (AE), turbidity (TU), total nitrogen (TN). Beer (B); deaerated water (DW). Statistical analysis was performed separately. Values in the same column with different letters are statistically different (P < 0.05).

Figure 4. Percent of ethanol removed using different stripping solutions. Values with different superscript letters are statistically different (P < 0.05).

Figure 5. Decrease in ethanol during dealcoholization using different stripping solutions (B: beer; DW: deaerated water, CW: carbonated water). Values with different superscript letters are statistically different (P < 0.05).

not necessary to run it for 4 h. As well as the ethanol, the increase of the stripping solution quantity caused a diminution of volatile compounds concentration at the end of treatment (Table 1). The quality parameters monitored did not change significantly (Table 2), except for carbon dioxide, which was decreased considerably, and turbidity, which was increased slightly after dealcoholization. Different Stripping Solution. The effect of different kinds of stripping solution was studied in this part of the work. Carbonated water (CW) was compared with normal deaerated water (DW) in order to reduce the loss of carbon dioxide by

the end of the process. If possible, the stripping solution was pure water, which had been previously deoxygenated by boiling and/or flushing with a gas, usually nitrogen. In other words, if the stripping solution is similar to beer from a compositional point of view (especially in the case of carbon dioxide and low oxygen content), the pressure gradient between carbon dioxide in the beer and in the stripping solution would be minimal, preventing its diffusion across the membrane.28 The amount of alcohol removed was the same with both strip solutions (Figure 4). On the contrary, the carbonation initially appeared to restrict ethanol transfer as shown in Figure 5 (mechanism 3282



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Table 3. Representative Volatile Compounds (mg L−1) and Loss Percentage (%) of Original and Dealcoholized Beer Using Different Stripping Solutionsa beer brand

AA

EA

EH

IAA

n-prop

2-MB

3-MB

DA

lager beer brand B B (1 L, 10 °C); DW (5 L, 10 °C) B in tubeside loss percentage (%) lager beer brand D B (1 L, 10 °C); DW (5 L, 10 °C) B in shellside loss percentage (%) B (1 L, 10 °C); CW (5 L, 10 °C) B in shellside loss percentage (%)

10.01 c 3.86 ab 61 B 4.97 b 2.48 a 50 A 2.82 a 43 A

18.31 c 4.43 bc 75 A 13.88 b 3.06 a 77 A 3.79 a 72 A

0.16 0.02

1.74 c 0.15 a 91 B 0.76 b 0.22 a 71 A 0.15 a 80 A

7.38 c 4.28 b 41 A 11.44 a 1.26 a 88 B 1.35 a 88 B

6.66 c 0.47 a 92 A 7.28 c 0.56 b 92 A 0.60 b 91 A

52.23 c 0.22 a 88 A 61.19 d 9.12 b 85 A 8.11 b 86 A

0.02 ab 0.01 a 32 A 0.07 c 0.03 ab 61 A 0.04 b 46 A

0.05 N.D. N.D.

a

N.D.: not detectable. Statistical analysis was performed separately. Values in the same column with different letters are statistically different (P < 0.05).

Table 4. Representative Parameters of Original and Dealcoholized Beer Using Different Stripping Solutionsa beer brand

OG (°P)

lager beer (brand B) B (1 L, 10 °C); DW (5 L, 10 °C) B in tubeside lager beer (brand D) B (1 L, 10 °C); DW (5 L, 10 °C) B in shellside B (1 L, 10 °C); CW (5 L, 10 °C) B in shellside

11.25 b 3.89 a 10.92 b 4.80 a 5.00 a

RE (°P)

AE (°P)

2.36 2.77 3.70 3.54 3.76

1.86 2.55 1.88 3.19 3.45

a a a a a

EtOH (% v/ v)

a ab a b b

5.00 0.79 4.71 0.84 0.79

c a b a a

pH 4.27 4.27 4.02 4.17 4.39

ab ab a ab b

color (EBC)

TU (EBC)

7.13 7.64 7.80 7.34 7.55

0.71 0.91 0.71 1.11 1.21

a a a a a

a ab a b b

TN (mgL−1) 521 534 354 342 346

b b a a a

CO2 (g L−1) 5.57 0.44 4.84 0.38 1.98

d a c a b

a Carbonated water (CW). Statistical analysis was performed separately. Values in the same column with different letters are statistically different (P < 0.05).

water is a viable option to reduce the carbon dioxide loss, allowing a low-alcohol beer with an acceptable carbon dioxide concentration. In these experiments the final carbon dioxide level, even when carbonated water was employed as stripping solution, was low compared to a typical specification for beer, and it would have been necessary to add more before packaging in a commercial process. On the other hand, the employment of stripping solutions with higher concentrations of carbon dioxide may have resolved the problem. Concerning the most important volatile compounds, no significant difference was found when using CW or DW (i.e., similar losses) (Tables 3 and 4). Effect of Stripping Solution Flow Rate. The effects of the stripping solution flow rate on the ethanol decrease are shown in Figure 6. In this case two different flow rates were employed: first 500 mL min−1 for feed and stripping solution, second 500 mL min−1 of feed solution and 1000 mL min−1 of stripping solution. A similar study was performed by Liguori et al. 38 That work showed that when increasing the stripping flow rate from 1.2 to 2.4 mL min−1, a more rapid decrease in ethanol content was observed. In this case no significant effect was observed as shown in Figures 6 and 7. Figure 7 was in agreement with Diban,30 confirming that flow rate has little influence on mass transfer resistance because the transmembrane resistance was the limiting stage in this transport mechanism. The volatile compounds and quality parameters did not change significantly when different stripping solution flow rates were employed (Tables 5 and 6). Feed Solution and Stripping Solution Inversion. In the trials above, the stripping solution flowed in the shellside so that the beer flowed tubeside. In the following trials these operating conditions were inverted so that the beer flowed shellside and stripping solution flowed tubeside. In this dealcoholization trial 83% of ethanol was removed instead of 79% when it was used with beer tubeside (Figures 8 and 9). Thus, the beer shellside and water tubeside could be a better option. More significantly, the ethanol results after 30, 60 and

Figure 6. Percent of ethanol removed using different stripping solution flow rate (mL min−1). Values with different superscript letters are statistically different (P < 0.05).

Figure 7. Decreasing ethanol during dealcoholization using different stripping solution flow rate. Values with different superscript letters are statistically different (P < 0.05).

unknown), but at the end of the process no difference was found. This would be explained by the equilibrium being reached between the beer and stripping solution. In other words, the ethanol concentration became the same in both beer and stripping solution. As expected, low-alcohol beer obtained using CW showed about 2 g L−1 of carbon dioxide, whereas the process with normal deaerated water resulted in about 0.4 g L−1 in each trial. The results showed that the use of carbonated 3283



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Table 5. Representative Volatile Compounds (mg L−1) and Loss Percentage (%) of Original and Dealcoholized Beer Using Different Flow Ratesa beer brand

AA

EA

EH

IAA

n-prop

2-MB

3-MB

DA

lager beer (brand B) flow rate 500 mL min−1 loss percentage (%) flow rate 1000 mL min−1 loss percentage (%)

10.01 b 4.46 a 55 A 4.56 a 54 A

18.31 b 3.44 a 81 A 3.79 a 79 A

0.16 N.D.

1.74 b 0.30 a 83 A 0.27 a 84 A

7.38 b 1.17 a 84 A 1.01 a 86 A

6.66 b 1.41 a 79 A 0.55 a 91 B

52.23 b 9.90 a 81 A 9.20 a 82 A

0.02 a 0.03 a

N.D.

0.03 a

a N.D.: not detectable. Statistical analysis was performed separately. Values on the same column with different letters are statistically different (P < 0.05).

Table 6. Representative Parameters of Original and Dealcoholized Beer Using Different Flow Ratesa

a

beer brand

OG (°P)

RE (°P)

AE (°P)

EtOH (% v/v)

pH

color (EBC)

TU (EBC)

TN (mg L−1)

CO2 (g L−1)

lager beer brand B flow rate 500 mL min−1 flow rate 1000 mL min−1

11.25 b 4.21 a 4.14 a

2.36 a 2.54 a 2.68 a

1.86 q 2.22 ab 2.42 b

5.00 b 0.93 a 0.94 a

4.27 a 4.24 a 4.31 a

7.13 a 7.77 a 7.29 a

0.71 a 1.07 b 1.00 b

521 a 535 b 529 b

5.57 b 0.13 a 0.24 a

Statistical analysis was performed separately. Values on the same column with different letters are statistically different (P < 0.05).

However, as shown in Table 8, for all dealcoholization techniques surveyed substantial losses of volatile compounds occurred, which would have had a significant effect on the flavor. However, OD compared favorably with alternative techniques such as dialysis, vacuum distillation, falling film evaporation, and reverse osmosis (Table 8). Operating Cost Examination. A cost examination was performed in order to appraise OD as an economically viable technique. It was assumed an annual production of 100 000 hL of a low-alcohol beer with the initial ethanol content of 4.5 and a final one of 0.5% v/v. The finished plant cost (pumps, pipes, valves) emerged directly from a request for a quotation by a manufacturer, which is approximately 340 000 €, Thus, considering the plant amortization over 10 years, the annual plant cost is 34 000 €, with a cost of 0.0034 € L−1 of produced beer. The membrane replacement cost, assuming a membrane life of 2 years, is approximately 25 000 € per year. Membrane cost information was obtained from a private company specializing in membrane production. Finally, assuming United Kingdom industrial energy unit cost of 0.09895 € kW h−1, the estimated energy cost was about 0.00021 € L−1 (www.energy. eu). Regarding water cost, supposing a unit water cost in United Kingdom of 1.9 € m−3, the value produced is approximately 0.0114 € L−1, including water required for processing and cleaning. Regarding manpower, this is always an estimate because of a wide variability across the European Member States, where the average labor cost is 23.50 € h−1 (Eurostat, 2013). Although membrane plants have a low requirement for supervision compared to many processes, it is important to take into account membrane maintenance, cleaning, and controlling. It could be right to consider one person per day, in this case the manpower cost would be about 50 000 € year −1. Operating costs, investment, and membrane replacement costs could be problems that inhibit the commercialization. Improved profitability could be reached with a few process improvements such as employing sparkling and flavored water as stripping solution, thereby generating another valuable product stream. The process settings and control was relatively simple, as well as membrane and plant cleaning. A membrane unit setup with the beer on the shellside resulted in the most efficient ethanol removal (Tables 7 and 8, Figures 8 and 9), whereas employing different temperatures and different stripping solution flow

Figure 8. Percent of ethanol removed using different flowsides. Values with different superscript letters are statistically different (P < 0.05).

Figure 9. Decreasing ethanol during dealcoholization using different flowsides (B: beer; DW: deaerated water, CW: carbonated water). Values with different superscript letters are statistically different (P < 0.05).

90 min suggested that the ethanol was being removed more quickly with the beer shellside. Equilibrium may be achieved more quickly, making the process more efficient and costeffective. With regard to the volatile compounds a larger amount of isoamyl and ethyl acetate was lost with beer in tubeside, while other compounds exhibited no significant differences (Table 7). These findings appeared to be similar to the performance of reverse osmosis when applied to dealcoholization in terms of ethanol, n-propanol, and esters removal (Table 8). Osmotic distillation appeared to compare favorably with vacuum distillation, which is a commonly employed dealcoholization technique and also the process with the highest ethanol and volatile compounds removal. 3284



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Table 7. Representative Volatile Compounds (mg L−1) and Loss Percentage (%) of Original and Dealcoholized Beer Using Different Flowsidesa beer brand

AA

EA

EH

IAA

n-prop

2-MB

3-MB

DA

lager beer brand B beer in tubeside loss percentage (%) lager beer brand D beer in shellside loss percentage (%) lager beer brand E beer in shellside loss percentage (%)

10.01 b 4.51 a 54 A 4.97 a 3.49 a 50 A 7.61 ab 3.78 a 50 A

18.31 c 3.99 a 78 B 13.88 b 3.06 a 77 B 16.88 c 4.39 a 73 A

0.16 N.D.

1.74 c 0.21 a 88 B 0.76 b 0.22 a 71 A 0.73 b 0.15 a 79 A

7.38 bc 2.60 ab 64 B 11.44 c 1.26 a 88 C 6.80 b 4.23 ab 37 A

6.66 c 0.51 a 92 A 7.28 c 0.56 a 92 A 5.46 b 0.46 a 91 A

52.23 c 7.02 a 86 A 61.19 d 9.12 a 85 A 41.57 b 6.20 a 85 A

0.02 a 0.02 a 12 A 0.07 b 0.03 a 61 B 0.02 a 0.02 a

0.05 N.D. 0.13 N.D.

a N.D.: not detectable. Statistical analysis was performed separately. Values on the same column with different letters are statistically different (P < 0.05).

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ACKNOWLEDGMENTS We gratefully acknowledge the financial support of the Italian Minister of Agriculture and the Ministry of Education, University and Research.

Table 8. Aroma Compounds Loss Percentage (%) before and after Dealcoholization by Means of Falling Film Evaporation (FFE),39 Dialysis,40 Vacuum Distillation (VD),41 and Reverse Osmosis (RO)42a

a

volatile compound

dialysis

FFE

VD

RO

OD

ethanol (%) acetaldehyde (%) n-propanol (%) iso-butanol (%) isoamyl acetate (%) ethyl acetate (%) total esters (%)

90 31 94 95 95 99 99

89 N.A. 92 95 25 N.A. 94

99 60 100 100 100 100 100

91 N.A. 70 66 89 88 88

87 54 64 92 80 84 85

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N.A.: not analyzed.

rates did not result in improved performance. A significant decrease in the concentration of beer volatile compounds was measured after dealcoholization in all experiments, demonstrating that the volatile compounds loss is directly related to the ethanol percentage removal. This is in accordance with other studies on alcoholic beverages dealcoholization.29,38,43−45 Furthermore, it is crucial to focus on stripping solution, which is slightly alcoholic (in this case in the range of 0.5−1% v/v) and flavored after the dealcoholization of the original beer stream. Therefore, it could be reusable in the brewing process, for instance for high gravity dilution, as brewing liquor into the mashing, sparging, or whirlpool phase, or even as a new innovative product, for example, as flavored water with a small amount of alcohol. In this experimental work some important characteristics of the beer were not analyzed, such as the foam stability and the evaluation of flavor by trained panel, two crucial attributes and often considered weak points of low-alcohol beers. Anyway, this study was primarily proof of feasibility of the OD to produce low-alcohol beer, where the behavior of the membrane about removal of ethanol in response to the variation of process parameters was investigated. However, this data collection will be taken into account in the next step, in order to give more and more information on this method of dealcoholization.

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Effects of Operating Conditions during Low-Alcohol Beer Production

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