Bubble Dynamics in Sparkling Bottled Waters_JFE 2015

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  See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/276164317 Bubble dynamics in various commercialsparkling bottled waters  ARTICLE   in  JOURNAL OF FOOD ENGINEERING · APRIL 2015 Impact Factor: 2.77 · DOI: 10.1016/j.jfoodeng.2015.04.016 READS 117 5 AUTHORS , INCLUDING:Gérard Liger-BelairFrench National Centre for Scientific Resea… 85   PUBLICATIONS   965   CITATIONS   SEE PROFILE Stephane BrunnerDanone 1   PUBLICATION   0   CITATIONS   SEE PROFILE Clara CilindreUniversité de Reims Champagne-Ardenne 36   PUBLICATIONS   395   CITATIONS   SEE PROFILE All in-text references underlined in blue are linked to publications on ResearchGate,letting you access and read them immediately.Available from: Gérard Liger-BelairRetrieved on: 08 February 2016  Bubble dynamics in various commercial sparkling bottled waters Gérard Liger-Belair a, ⇑ , Florine Sternenberg b , Stéphane Brunner b , Bertrand Robillard c , Clara Cilindre a a Equipe Effervescence, Champagne et Applications (GSMA), UMR CNRS 7331, Université de Reims Champagne-Ardenne, BP 1039, 51687 Reims Cedex 2, France b Danone Research, Centre de Recherche Daniel Carasso, RD 128, 91767 Palaiseau, France c Institut Œnologique de Champagne (IOC), ZI de Mardeuil, Route de Cumières, BP 25, 51201 Epernay Cedex, France a r t i c l e i n f o  Article history: Received 3 February 2015Received in revised form 31 March 2015Accepted 19 April 2015Available online 24 April 2015 Keywords: CO 2 Sparkling watersBubble dynamicsMolecular diffusion a b s t r a c t Observationsweremaderelevanttocommonsituationsinvolvingtheserviceofvarioussparklingwaters.Bubble dynamics andprogressive losses of dissolved CO 2  were closely examinedinthree various batchesof carbonated waters holding different levels of CO 2 . During the turbulences of the pouring process, acloud of bubbles appears in the water bulk. Under the action of buoyancy, bubbles progressively reachthe free surface, and the cloud of bubbles finally vanishes. Bubbles also nucleate on the glass wall, wherethey grow by diffusion until buoyancy forces them to detach and rise to the free surface to release theirCO 2 . The three batches of sparkling waters were clearly differentiated with regard to their bubblesdynamics and losses of dissolved CO 2 . Our observations were systematically rationalized and discussedon the basis of mass transfer considerations including molecular diffusion, basic concepts of gas solutionthermodynamic equilibrium, and bubble dynamics.   2015 Elsevier Ltd. All rights reserved. 1. Introduction In the past 15years, the global bottled water market has seen aremarkable growth (Euzen, 2006; Storey, 2010; Rani et al., 2012), thus raising in turn legitimate environmental concerns regardingthe waste management sector (Gleick, 2010). The Forbes magazine even declared that bottled water is expectedto become the largestsegmentof theU.S. liquidrefreshmentbeveragemarketbytheendof this decade (Forbes, 2014). In 2011, the global bottled watermarket has reached 233 billion liters sold all over the world(Rodwan, 2012).Among the global bottled water, the sparkling water segmentrepresents nowadays about 10% of the whole bottled water indus-try. Nevertheless, this percentage may vary a lot from country tocountry. In the UK, it is close to the global average, whereas inGermany, which is the biggest bottled water market in the worldforpremiumwaters,around80%ofthemarketisactuallysparklingwaters (Euzen, 2006). Sparkling waters are often seen as a substi-tute for sweet beverages, and this is particularly true for flavoredsparkling waters (Rani et al., 2012). Suffice to say that the bottled sparklingwater is abooming, but verycompetitivemarket, involv-ingnumerouscompaniesthroughouttheworld, withEuropebeingthe largest producer (75%), followed by the USA (20%) (Bruce,2013).Classificationandlabelingofbottledcarbonatedwatersmustbein conformity with EU regulations (E. Directive 2009/54/EC and2003/40/EC). Commercial bottled carbonated natural mineralwaters fall into three categories: (1) ‘‘naturally carbonated naturalmineral water’’, when the water content of carbon dioxide comingfrom the spring, and in the bottle are the same as at source; (2)‘‘natural mineral water fortified with gas from the spring’’ if thecontent of carbon dioxide comes from the same resource, but itscontent in the bottle is greater than the one established at source;and (3) ‘‘carbonated natural mineral water’’ if carbon dioxide fromansrcinotherthanthegroundwaterresourceis added.Actually, amethod using gas chromatography-isotope ratio mass spectrome-try has been proposed to determine the carbon isotope ratio 13 C/ 12 C of CO 2  (Calderone et al., 2007). This method was success- fully applied to differentiate whether or not gaseous CO 2  in theheadspace of a bottled carbonated water originates from thesource spring or is of industrial srcin.The capacity of CO 2  to get dissolved in water is ruled by thewell-known Henry’s law, which states that the equilibrium con-centration c   of dissolved CO 2  is proportional to the partial pressureof gas phase CO 2  denoted  P  : c  ¼ k H  P   ð 1 Þ with  k H   being the strongly temperature-dependent Henry’s lawconstant of gaseous CO 2  in water (i.e., its solubility) (Carroll andMather, 1992; Diamond and Akinfief, 2003). Under identical condi-tions of temperature, water can therefore hold different levels of  http://dx.doi.org/10.1016/j.jfoodeng.2015.04.0160260-8774/   2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address:  gerard.liger-belair@univ-reims.fr (G. Liger-Belair). Journal of Food Engineering 163 (2015) 60–70 Contents lists available at ScienceDirect  Journal of Food Engineering journal homepage: www.elsevier.com/locate/jfoodeng  dissolvedCO 2 , dependingonthepressureof gas phaseCO 2  foundinthe headspace below the cap or screw cap. In carbonated beverages, the concentration of dissolved CO 2  isindeed a parameter of paramount importance since it is responsi-ble for the very much sought-after fizzy sensation, and bubble for-mation (the so-called  effervescence ). In sparkling waters, andcarbonated beverages in general, homogeneous bubble nucleation( ex nihilo ) is thermodynamically forbidden (Wilt, 1986; Lubetkin,2003). In order to nucleate, bubbles need preexisting gas cavitiesimmersed in the liquid phase, with radii of curvature larger thana critical size. In carbonated beverages typically holding severalgrams per liter of dissolved CO 2 , the critical radius needed to initi-ate bubble nucleation (under standard conditions for pressure andtemperature) is of order of 0.1–0.2 l m (Liger-Belair, 2014). This non-classical heterogeneous bubble nucleation process is referredto as type IV nucleation, following the classification by Joneset al. (1999). The presence of dissolved CO 2  therefore directlyimpacts consumers of sparkling waters, by impacting severalemblematic sensory properties such as (i) the visually appealingfrequency of bubble formation (Liger-Belair et al., 2006), (ii) thegrowth rate of bubbles ascending in the glass (Liger-Belair,2012), and (iii) the very characteristic tingling sensation in mouth.Carbonation, or the perception of dissolved CO 2 , indeed involves atruly very complex multimodal stimulus (Lawless and Heymann,2010). During carbonated beverage tasting, dissolved CO 2  acts onboth trigeminal receptors (Dessirier et al., 2000; Kleeman et al.,2009; Meusel et al., 2010), andgustatoryreceptors, viathe conver-sion of dissolved CO 2  to carbonic acid (Chandrashekar et al., 2009;Dunkel and Hofmann, 2010), in addition to the tactile stimulationof mechanoreceptors in the oral cavity (through bursting bubbles).More recently, Wise et al. (2013) showed that the carbonation bitewas rated equally strong with or without bubbles under normal orhigher atmospheric pressure, respectively. However, a consumerpreference for carbonated water containing smaller bubbles hasbeen previously reported in a thorough study on the nucleationand growth of CO 2  bubbles following depressurisation of a satu-rated carbon dioxide/water solution (Barker et al., 2002).Moreover, it was also clearly reported that high levels of inhaledgaseous CO 2  become irritant in the nasal cavity (Cain andMurphy, 1980; Cometto-Muniz et al., 1987).For all the aforementioned reasons, monitoring accurately thelosses of dissolved CO 2  in a glass poured with sparkling water isof interest for carbonated waters elaborators. In the past 15years,the physics and chemistry behind effervescence has indeed beenwidely investigated in champagne and sparkling wines (for arecent and global overview, see Liger-Belair (2012) and referencestherein). Nevertheless, and to the best of our knowledge, the bub-blingprocessitself andthereleaseof gaseousCO 2  remainedpoorlyexplored in sparkling waters, under standard tasting conditions.The present article reports experimental observations relevantto common situations involving the service of commercial carbon-atednaturalmineralbottledwaters.Bubbledynamicsandprogres-sivelossesof dissolvedCO 2  werecloselyexaminedinthreevariousbatches of naturally carbonated waters holding different levels of CO 2 . Our observations were conducted in real consuming condi-tions, i.e., in a glass and ina plastic goblet. During the pouringpro-cess,acloudofbubblesnucleateandgrowinthewaterbulk.Underthe action of buoyancy, bubbles rise toward the free surface, andthe cloud of bubbles progressively vanishes. Bubbles also nucleateon the glass wall, where they grow by diffusion until buoyancyforces them to detach and rise toward the free surface. Weexplored the above questions with dedicated experiments usedto quantify the bubble dynamics, and the kinetics of gaseous CO 2 discharging from the liquid phase (in real consuming conditions)as describedin Section2. In Section3.1., the lifetimeof the quickly vanishingcloudofbubblesfollowingthepouringstepisexamined.In Section 3.2., the progressive losses of dissolved CO 2  escapingfrom the liquid phase (once it is poured in a plastic goblet) aremeasuredanddiscussed.Finally, inSection3.3., kineticsofbubblesgrowing stuck on the plastic goblet are closely examined. Ourobservations are rationalized and discussed on the basis of masstransfer considerations including molecular diffusion, basic con-cepts of gas solution thermodynamics, and ascending bubbledynamics. 2. Materials and methods  2.1. The three batches of carbonated waters Three batches of various commercial carbonated natural min-eral bottled waters from Poland, and provided by DanoneResearch, were investigated. They are described and referencedas follows: Nomenclature c  L  concentration of dissolved CO 2  in the liquid phase, ing L   1 c  0  concentration of dissolved CO 2  in Henry’s equilibriumwith gas phase CO 2  in the bubble, in g L   1 c  i  initial concentration of dissolved CO 2  in the liquidphase, in g L   1 d  bubble diameter, in m D  diffusion coefficient of dissolved CO 2  in the liquid phase,in m 2 s  1 F  T   total volume flux of gaseous CO 2  escaping the liquidphase, in cm 3 s  1  g   gravity acceleration, in m s  2 h  level of liquid in the glass, in m  J   molar flux of gaseous CO 2  which crosses the bubbleinterface, in mol  1 m  2 s  1 k  growth rate of bubbles growing through molecular dif-fusion in the liquid phase supersaturated with dissolvedCO 2 , in m s  1 k H   Henry’s law constant of dissolved CO 2  in water (i.e., itssolubility), in g L   1 bar  1 m  cumulative mass of CO 2  escaping the liquid phase, in g M   molar mass of CO 2 , =44 g mol  1 n  mole number of gaseous CO 2  in the bubble, in mol P   pressure, in Pa r   bubble radius, in m R  ideal gas constant, =8.31 J K  1 mol  1 t   time, in s T   temperature, in K U   ascending bubble velocity, in m s  1 v  bubble volume, in m 3 V   volume of liquid poured into the glass or plastic goblet,in L  k  thickness of the diffusion boundary layer around thebubble, in m g  dynamic viscosity of water, in Pa s q  density of water, in kg m  3 G. Liger-Belair et al./Journal of Food Engineering 163 (2015) 60–70  61  1. A low carbonated water (labeled LCW);2. A medium carbonated water (labeled MCW); and3. A highly carbonated water (labeled HCW).MCW and HCW are conditioned in 1.5l polyethyleneterephthalate (PET) bottles, whereas LCW is conditioned in0.7l PET bottles. Concentrations of dissolved CO 2  found inwater samples were determined by using carbonic anhydrase(labeled C2522 Carbonic Anhydrase Isozyme II from bovineerythrocytes, and provided from Sigma–Aldrich – US) (Caputiet al., 1970). This method is thoroughly detailed in a previ-ous paper (Liger-Belair et al., 2009). Non-CO 2  gases (O 2  andN 2 ) were also approached through measurements based onthe multiple volume expansion method (MVE) deduced froma typical CarboQC beverage carbonation meter (Anton Paar).Moreover, for each water sample, the dynamic viscosity(denoted  g ) was measured, at 20  C, with an Ubbelhodecapillary viscometer, and with water samples first degassedunder vacuum. Table 1 compiles the pertinent data discussedin this study. Actually, because the level of dissolved gases isthe main cause behind bubble nucleation and growth insparkling beverages (Liger-Belair, 2012), it is worth noting that the very low concentrations of other ‘‘non CO 2 ’’dissolved gases (with regard to the relatively high concentra-tions of dissolved CO 2  in water samples) has absolutely noimpact considering the dynamics of CO 2  bubbles in thesesparkling waters (even with the LCW, which contains twiceas much other non-CO 2  dissolved gases than the two otherswater samples).  2.2. The glasses used and their washing protocol Experiences dealing with the cloud of bubbles following thepouring step were conducted with a series of four «classicalflutes» (180mL – Marianna, Lednické, Slovakia/sold by Arystal),with an open aperture diameter of 4.8cm, and a wall thicknessof 0.8mm. This glass model was chosen since it is perfectlycylindrical (i.e., with low optical distortion), and since it wasspecifically used, during the past few years, for the study of effervescence and foam formation in various standard commer-cial hydroalcoholic beverages supersaturated with dissolvedCO 2  (Liger-Belair, 2012). Nevertheless, as concerns the kinetics of gas discharging from the liquid phase, as well as the kineticsof bubble growth on the glass wall, it did not seem perfectlyadapted (due to a lack of reproducibility). Regarding the kineticsof gas discharging as well as the study of bubble growth on theglass wall, we rather used a simple plastic goblet (200mL in vol-ume), which showed a much more satisfying reproducibilityfrom one pouring to another (with an identical water sample).Before each series of experiments dealing with the cloud of bub-bles following the pouring process, flutes were carefully rinsedusing distilled water and then compressed air-dried.Nevertheless, in case of the plastic goblets, goblets were usedonly once, and replaced before each new experimental dataseries.  2.3. Measuring the lifetime of quickly vanishing clouds of bubbles following pouring  Flutesweresimplyplacedonatable,infrontofacoldbacklight.180±5mL of water are poured into the flute standing vertically.Pouring series were conducted at room temperature (20±1  C).During the pouring step, which lasts approximately 5s, water fallsfromthebottleneck,whichstandsabout1cmabovetheupperpartof the flute, as shown in the time-sequence displayed in Fig. 1.During the pouring process, a cloud of bubbles appears in the liq-uid phase, progressively rise toward the water surface under theaction of buoyancy, and progressively vanishes as bubbles reachthe free surface. Once the flute is filled with water, the lifetimeof the cloud of bubbles is measured by use of a standardchronometer. The cloud of bubbles was clearly identified (by thenaked eye) by use of the cold backlight placed behind the flute,which provides an excellent contrast between bubbles and water.To enable a statistical treatment, six successive pourings weredone (from a single bottle), for each sparkling water sample, tofinally produce one single ‘‘average’’ cloud of bubbles’ lifetime,characteristic of a given water sample (with standard deviationscorresponding to the root-mean-square deviations of the valuesprovided by the six successive data recordings).  2.4. Measuring the kinetics of dissolved CO  2  progressively discharging  from water  100±2mL of sparkling water were poured into a goblet, previ-ously level-marked with 100mL of distilled water. Experimentswere performed at room temperature (20±1  C). Immediatelyafter pouring, the goblet was placed on the chamber base plateofaprecisionweighingbalance(Sartorius–ExtendSeriesED)witha total capacity of 220g and a standard deviation of ±0.001g. TheSartorius balance was interfaced with a laptop PC recording dataevery 5s from the start signal, activated just after the goblet wasplaced on the weighting chamber base plate. The total cumulativemass loss experienced by the goblet poured with water wasrecorded during the first 10min following pouring. Actually, themass loss of the goblet poured with water is the combination of both (i) water evaporation, and (ii) dissolved CO 2  progressivelydesorbing from the supersaturated liquid phase. The mass lossattributed to water evaporation only was simply accessible byrecording the mass loss of a goblet poured with a sample of 100mL of water first degassed under vacuum. Due to likely varia-tions in hygrometric conditions from one day to another, standardevaporation was thus measured with a sample of water firstdegassed under vacuum, just before each series of total mass lossrecordings was done. The cumulative mass loss vs. time attributedonly to CO 2  molecules progressively desorbing from a sparklingwater sample may therefore easily be accessible by subtractingthe data series attributed to evaporation only from the total massloss data series. Generally speaking, in the area of sparkling bever-age, the parameter which characterizes a sample is its dissolvedCO 2  concentration, denoted  c  L , and usually expressed in gL   1 .The progressive loss of dissolved CO 2  concentration after a sampleof water was poured into a goblet, may therefore be accessed byretrieving the following relationship: c  L ð t  Þ¼ c  i  m ð t  Þ V   ð 2 Þ with  c  i  being the initial concentration of dissolved CO 2  in water(given in Table 1),  m ( t  ) being the cumulative mass loss of CO 2  withtime expressed in g, and  V   being the volume of water poured intothe goblet expressed in L (namely 0.1L in the present case). Moreover, from a cumulative mass loss-time curve, the massflux of CO 2  desorbing from the water surface (denoted  F  CO 2 ) is  Table 1 Physicochemical pertinent properties of the three carbonated waters investigated inthis study, namely, dissolved CO 2 , and non-CO 2  gases (O 2  and N 2 ) initially held in theclosed PET bottled waters, as well as their dynamic viscosity. Watersample[CO 2 ]  c  i (gL   1 )Non-CO 2  gases (O 2 /N 2 )(mgL   1 )Viscosity  g (  10  3 Pas)LCW 3.25±0.08 17 0.98±0.01MCW 4.53±0.15 8.5 0.99±0.01HCW 6.87±0.28 9.5 0.99±0.0162  G. Liger-Belair et al./Journal of Food Engineering 163 (2015) 60–70
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