Soda Pop: Newsletter Challenge (01/15/08)

I know nothing whatsoever about this, but three possibilities immediately present themselves:
i) The market for large bottles is families at home, so the drinks are made less carbonated (or less acidic) to appeal to that market
ii) In order to minimise costs, the large bottles are not made significantly thicker than the small bottles; because of their larger diameter, they cannot withstand as high a pressure as the smaller bottles, so the level of carbonisation has to be reduced.
iii) The larger number of openings of the large bottle results in the soda going "flat" towards the end of the bottle.

As this is a "technical" thread, I'd go with possibility #ii.
BTW, is Roger aspartame junkie, or has he got rotten teeth?

Fyz

Bottles are round and generally the round shape offers the greatest amount of strength. I do not believe strength is at issue here.

On the idea of carbonation though, the pressure inside the smaller bottles and larger bottles will be the same (ie pounds/sq inch or Kg/sq cm). As a result the force per area on the wall of the smaller bottle will be the same as the big ones. Keep in mind too there is more room for the gas to expand into.

Also acidity and sweetness are two entirely different tastes. If you add too much sugar to something, you can not counter it by adding acid. Take for instance, sweet and sour pork. The only way to make the soda less sweet is to put less sugar in it or there is anti-sweeter available that chefs can use in a pinch. But the best way to avoid being over sweet is to be careful not to add too much sugar in the first place.

The thought of using artifical sweeter throws a whole different bend on the question though. I drink artifically sweeted soda all the time and do notice that different batches of soda do taste different, even from the same area.

Another bend on the problem is the water quality used by the bottler can affect the flavor. Coke bottled in Pennsylvania might tast quite different from that of Florida just because of the water.

This question has a lot of possibilities!

I think you are missing the crucial point - the force per area is constant, but the area is greater. The consequence is that the total force is also greater.
For simplicity consider the cylindrical section of the bottle: you will see that the on the sides of the cylinder is pressure*area = pressure*diameter*length; if this is supported by tension in the container, the tension per unit length of the sides must be pressure*diameter/2. This, if the tensile strength of the bottle comes into this, the thickness of the walls will need to be proportional to the linear dimensions of the bottle, as implied in my previous post. (Another way of looking at this is that the pressure a tensile vessel can apply is proportional to the product of the strength and the curvature)

N.B: this is the same reason as the large soap bubble at one end of a tube grew while the small one at the other end collapsed (in the standard high-school experiment).

quick point fyz,

The increased volume of soda in the bottle is not proportional to the surface area of soda in the bottle. I.E.-a 2 or 3 L bottle does not have 2 or 3 times the surface area as a 1L bottle. Also; the void above the soda is not 2 or 3 times greater. To carbonate soda to the same degree as a smaller bottle, the partial pressure of CO₂ above the liquid must be the same for both bottles however. As you have pointed out, that would require a more robust plastic to be used...or...use less carbonation, hence less carbonic acid in solution, hence less tang (acid) taste, hence a sweeter product. Am I close?

First, I have no special knowledge. I think we are saying much the same thing, however.

I think that (for commercial reasons - both transport volume and materials usage) the size of the void will be made as small as is practically viable. The proportion will depend directly on the fill pressure. Similarly, manufacturers will use the smallest amount of material possible for the bottle. From the numbers in the bottle research and blank supplier web sites, I deduce that diffusion through the skin of the bottle is the limiting factor. In this case it is acceptable for large bottles to have thinner walls than small ones - and still have a longer time-constant for loss of pressure. Assuming the limit on initial fill pressure is the pressure at the end of the distribution chain (i.e. after experiencing the most adverse storage), larger bottles can have lower initial pressure - that also allows use of a smaller void (small contribution, but still** helpful).
Cost savings all round (gleefully rubs hands while setting off to bank, then realises that supermarkets have already reduced his price by more than the available cost savings of the larger bottles, so turns back home despondently)

**Fyz

OK we're on the same track. My point is that to have equal carbonation in the larger volume of soda, you would have to exert a proportionally equally larger partial pressure of CO₂ on the surface of the soda in the bottle.(3X larger volume= 3X greater pressure). The void of the bottle is approx the same, and the surface area is close, you would theoretically have to double or triple the surface pressure to accomplish the same level of carbonation. Because that is not safe or practical, the lesser extent of carbonation produces less Carbonic Acid=less acidic (tang), and a sweeter product.

You are using the term 'pressure' in a non-technical sense, which is imprecise and rather confusing. Technically, pressure is defined as "force per unit area" and will be the same for a given concentration - regardless of bottle size. What changes is the total outward force on the 'skin' of the bottle - which is proportional to the surface area.

Henry's law - the solubility of a gas (in g/L) is directly proportional to the partial pressure (in atm) of the gas above the solution. In this case I'll assume that the void is completely CO₂. If the surface area of the solution has not increased to the same magnitude as the volume, would that not mean that the container would have to be under more stress to maintain the same pressure on the liquid? Or am I just not envisioning this case properly?

We are not, I believe, disagreeing as to substance - just that your earlier colloquial use of precisely defined terms such as pressure made it impossible to be absolutely clear what you were saying.

Yes, of course more stress, and also greater tension in the walls of the vessel. But exactly as a result of the same pressure applied over a larger area.

Sorry to be pedantic, but we are trying to use these phenomenological descriptions as foundations.

You being pedantic?? Nooo - that's as crazy as me being sarcastic.

Don't mind me - statics and stresses was always one of those subjects that I had to carefully deconstruct to understand completely. Chemistry on the other hand is my preferred subject

The water quality does not vary. The syrup manufacturers (Coke, Pepsi, etc.) actually perform quality control of the water used for bottling water all over the world. Cocacola requires that the water be treated to match Atlanta, GA--probably to a date from several decades ago. The amount of syrup, water and carbonation is carefully controlled as well.

The larger bottle, being opened more times, will lose more CO2 as the bottle is being consumed. Reduced CO2 means reduced acidity, resulting in decrease of a sour component in the taste. The result is the perception that the drink is "sweeter".

BTW, phosphoric acid is included in most carbonated beverage recipes. This maintains acidity, and helps to tingle the tongue, even though some of the carbonation may be lost.

JBPC

Given the general disagreement with my proposed solution, I took a quick look on the web. The weight of PET used for a 1-litre bottle is moving towards 20-gm, whereas the objective weight for a 4-litre bottle is moving to 40-gm. If the bottles were to be made the same shape, the 4-litre bottle would need to be thinner than the 1-litre bottle. Changing the shapes to allow the thickness to be the same would make for a larger proportional diameter; this would recover the thickness, but not increase the total pressure the bottle could withstand.

From the above it appears that the wall thickness requirement is dominated by the shelf-life of the product - it has to be thick enough to prevent excessive CO2 diffusing through the walls of the container.

If you maintain identical wall thicknesses the proportional rate of loss from a larger container will be lower than from a smaller one, so you can afford a lower initial CO2 fill. That means that it would make economic sense to run the large bottling line at a lower CO2 pressure than the line producing smaller bottles - regardless of whether the bottle will withstand the pressure. The article mentions both pressure testing and CO2 retention, so it would seem that both are likely to be relevant.
My tentative conclusion remains that Roger buys from outlets with high turnover rates, and therefore that he observes something close to the original CO2 fill levels - and the larger bottles are indeed filled to a lower initial CO2 pressure. But I'm not certain whether the reason is primarily that the larger bottles can support less pressure (which is undoubtedly the case) or that the lower proportional diffusion rate allow the suppliers to save money by reducing the CO2 fill pressure.

with twice the resin and twice the volume the larger one has a thicker wall.(because one is a cube function and the other is linear....consider a spherical bottle) This is in keeping with hoop stress theory.

air space is vented with every opening, so gas is lost progressively and this alters the PH and thus the taste. sweet/tart from sugar/acid + flavor of the liquor used. Change the PH and the taste changes. boiled and cooled cola, dead flat or dead tame is very different, so the gas content = big factor

The ratio of linear dimension would be 1:4^0.3333. So the ratio of surface are would be 1:4^0.666667 (=2^1.33333) . With a wall volume ratio of 1:2, the thickness ratio must be 1:1/2^0.333333.

Now do your hoop stress theory - clearly, the bottle is a great deal weaker. If the shapes were mathematically similar, the rate of loss of concentration in a sealed bottle would be unchanged; in fact, the larger bottles are more squat in form, so the walls thickness is more-or-less maintained, and the rate of loss of concentration from the large bottle is reduced.

Fyz

P.S. given item iii of post #1, did you really need to explain the effect of venting?

The reason that they use extra resin per square CM is to provide the added strength for the larger bottle = heavier walls fro the higher hoop stress for what is probably the same line pressure for all sodas, although it is possible that they give a somewhat lower pressure to larger vessels. Thus if you consider a spherical container for 4 liters it would be(assuming 100% fill) versus 1 liter the smaller one will use. These spherical containers are widely used for milk from spherical cows...the ideal theoretical case

1000 Ml

12.4 Cm Diameter

484 surface area

20 grams of resin = .041 gms/CM2

4000 Ml

19.7 diameter

1220 area

40 grams of resin = .032 gms/CM2

it seems as if this 20 grams/40 grams produces a thinner walled bottle. This is counter to the increased hoop stress, thus it may be that larger bottles use more?

A quick search found this.

http://www.visy.com.au/beverage/?id=249

these are PET preforms shipped this way to save space on the line they are expanded into a mold and filled. Note the fact that a one liter uses 40 grams and a 2 liter uses 59 grams. Doubtless the top and bottom masses are a factor here..

more here.

http://www.google.com/search?hl=en&q=%22carbonated+water%22+%2Bpressure+%2Bpet&btnG=Search

I looked at your first reference (the "search" output is not a basis for any discussion). Clearly, the Australians are willing to spend more on the PET for the bottles than the Brits**! I suspect the reason for the difference is that Australians need longer storage times*** and experience more extreme (high) temperatures than the UK, so they need to use thicker walls.
**My reference (repeated here for convenience) gave 20-gm and 40-gm as state-of-the art for 1 and 4 liters respectively.
***To cover the difficulty of access to some regions of the country.

More significantly, I didn't find your 59-gm weight for the two litre bottle. On a like-for-like basis your first reference gives 50.3 to 54.5gm (with the 54.5-gm size usable for larger bottles than 2-litres as well). If we were to keep both shape and wall-thickness constant, the 40-gm at 1-litre would scale to 53.33 gm - so the thickness still does not increase with bottle size.

Hopefully (at last) we have stage1 agreement. Now, what about the implications on the initial C2 concentrations?

Fyz

yes, possibly a hotter climate makes more bangers, so Australians are more conservative. There are also strength grades in PET

There is a tradeoff in PET costs versus bangers and regulations on top.

A search is never intended for a discussion, it is for follow on by those interested.

The one reference I used was included.

In any event, the comment about hoop stress was indicated to show that as the diameter of a container increases there is a concommitant need for thicker/stronger walls for the increased hoop stress.

P.S. I think I wasn't as clear as I might have been that the indication from both the UK and Aus references is that the wall thickness does not increase with bottle volume. I suspect that means that diffusion through the skin of the bottle is the limiting factor in both climates.

Since soda is not normally stored for long periods I doubt diffusion out of CO2 is a major problem compared to bangers. Inwards O2 diffusion is more of a problem.

Pardon? Does PET have special porperties - otherwise the partial pressure of O2 will never exceed 0.2 atmospheres - and (pressure-wise) this will always happen for a period shortly after the first opening - when there is normal air (including the more important N2) and the partial pressure from the CO2 in the fizz have reached medium-term equilibrium. The issue appears to be loss of tang during transport and storage, not the strength of the bottle. Am I missing something?

They purge the air to keep the O2 out during storage, as O2 degrades many bottled products, some more than others. O2 can counter diffuse in against the CO2 unless they coat the inside to limit it. Once it is opened air enters and degradation ensues

I could easily be mistaken, but I had assumed that the O₂ barrier layer contained specific oxygen scavengers, so had a rather smaller effect on CO₂ diffusion. CO₂ diffusion in many materials is also assisted by virtue of it being soluble. That would correspond to the CO₂ having appreciably higher diffusivity through any barrier than oxygen. In any case, we are talking here about soda-pop, whose major constituents are weak acids and sugars (or synthetic sweeteners), and SFIK (I'm not an expert on junk-food chemistry) these are not significantly degraded by dissolved O₂.

Of course, so far as I am concerned, the major effect of oxygenation in at least some of the fluids that I choose to drink is beneficial.

I believe this is one of the possible chemical explanations. While the PET bottle is an excellent barrier to CO2 it is a bit poor for O2. This is why the PET beer bottle has never really made it (but PEN has been proposed instead or to have extra barrier layers), because the O2 will diffuse into the beer and quickly degrade the flavor.

Crystalline PET is indeed a good barrier for CO2. But bottles are made from blown PET, and the level of crystallinity is quite low. Consequently, the CO2 diffusivity is approximately a factor of 20 greater than the usual quoted figures for PET. As a consequence, a 1.5-litre bottle will lose half its charge in about 6-months when stored at 24 ^OC (see here). Based on the weights of PET in the various preforms, larger bottles lose their CO₂ charge rather more slowly than smaller ones, and are not capable of withstanding such high pressures. For a given pressure requirement at the end of shelf life, it is therefore possible (and probably also advisable) to fill the larger bottles to a lower pressure than the smaller ones (even on the assumption that using less CO₂ doesn't of itself reduce costs significantly).

You are proporting that with less CO2 left in soda that it will be sweeter. My experience though is the exact opposite. As the soda gets flatter, it losses the sweetness sensation. I see this in both the naturally and artificially sweetened beverages. The higher the carbonation, the sweeter the soda.

Your (c) is closest to the mark. I suspect that the loss of CO2 from repeated openings causes loss of the acidic "bite" from the carbonic acid. Thus "flat tasting" and sweeter.

You write as if you have privileged knowledge. Please indicate if that is so, or if you just think this easy explanation is the most likely in this case.

No, you have got it wrong. The flatter it is, it will be less sweet.

Apparently perceptions differ. Please see Roger's contribution (#23).

Yes you are right. Look at posting 37 where there is statistical proof to support the idea of perception. I would assume the tests were performed properly (ie double blind technique and all), so we have to dismiss the sweetness due to carbonation idea all together.

pressure needed maintain level of carbonisation is the same in either so why should the wall thickness make a serious difference. also this is probably not the case otherwise people using fizz keepers could inadvertantlyy explade their bottles of soda

Initial carbonisation could be made different to account for worst-case loss of CO2 during storage in the distribution system. If Roger moves to a remote location, he will find all the pop has become too sweet for his tastes.

As a food equipment service guy, I vote for ii, iii and iv. Either less carbonation or loss of carbonation will make the drink taste sweeter. iv is possibly that the large bottles are a different brand. The "..challenge" brand has more sugar and that is why they win their challenge. -- JHF

The C02 or lack of has rthe effect of allowing or disallowing the pure cola from reachin the taste buds. More carbination the less cola syrup from reaching the taste buds as the syrup is replaced by CO2 gas pockets.

The evidence is mixed as to whether CO2 makes the drink taste less sweet or not. What is certain is that the tongue remains wetted, so the cause of any change in perception is not that the bubbles fizzically get in the way of the dissolved sweetener.

Two things are happening in this solution. First; when the bottle is opened, and the pressure of the bottle is released, the CO₂ in solution becomes insoluble to a limit of approximately 600moles/L. The more soda, the more CO₂ is released to the enviroment (i.e.the bottle will last longer), and the sweetness isn't competing with the tang of CO₂. So although the formula for mixing the soda hasn't changed, the concentrations of flavours in a large bottle change after the bottle is opened. Second; some of the CO₂ combines with the H⁺ (soda is acidic-pH~4) to form aldehyde and ketone groups that are responsible for sweetness. Net result is the soda is a little flatter, and tastes sweeter. That is why some people put soda water in scotch (filthy bastards!) - to reduce some of the acids that are leached from the barrels in the vatting process, and "open" the flavours.

Given Roger's high consumption, we have to assume that the bottle spends much more time in storage than in use, so any difference in chemical combination effects must be insignificant.

The difference would be that the larger bottle is opened a larger number of times, so the CO2 has more opportunity to escape and goes flat by the end of the bottle. And surely a regular pop-drinker like Roger would have observed this as a specific change during use, unless the only times he has drunk from large bottles is when visiting households with large bottles and relatively low usage rates.

I still go for limited initial CO2 content to allow use of a thin-walled-bottle.

Fyz

I agree. Since the larger bottle of soda will take longer to drink the "flatness" effect is in play. The carbonated beverage contains dissolved CO2 which creates H2CO3 (carbonic acid). This carbonic acid creates a "tartness" to offset the sweetness created by the sugar content. However, as soon as the bottle opens the CO2 will begin to dissipate from the H20. This is what makes the soda flat. When all of the CO2 is gone there is no carbonic acid left in the beverage thus you are left with an over powering sweet drink of water and sugar/sweeteners. Since he can drink the smaller container faster it minimizes of the "flatness" effect.

Ha! The soda goes slightly flat in the larger containers!!!

Carbonic acid, which gives soda its fizz, tends to reduce the apparent sweetness. As the carbonic acid dissipates the soda tastes sweeter.

Ha! The soda goes slightly flat in the larger containers!!!

Add to this that it takes longer to drink the 2 or 3 liter bottles (as much as 2 to 3 times longer) and you have increased the "flat-eness ratio" with the "longevity factor".

If that is not what Hero meant, I'd appreciate hos clarification.

Fyz

Yes, because there will be significant loss of carbonation 1/2 way thru it.

and other half would be thrown out, making it expensive... dual fail

jstacat

Being a pop drinker myself, I have to agree with the hypothesis that the larger bottle gets flat before the smaller bottle, as it is accurate in its assumption.

When I purchase my weekly ration of pop, nothing changes until the bottle is opened. After the bottle is opened there is less fizz when poured each and every time the bottle is opened. I have learned that you can counteract this by collapsing the bottle as it gets emptied. although this sounds odd it seems to work.

After I pour my glass I squeeze the bottle till the pop gets close to the neck and then cap it off. I am not sure what is going on here but I assume that it has something to do with the lack of airspace left in the bottle, which may be preventing de-carbonization.

Just my take on it and what I do as a prevention.

Yes there would be a difference in taste The soda in the larger bottle would at the same rate of consumption loose carbonation. The carbonation be held in the fluid by pressure. As the area above the fluid increases as we empty the bottle the fluid looses carbonation to it until the pressure builds up. The large the bottle the more of the carbonation the fluid looses. Soda becomes flat and taste sweeter.

I have observed this phenomenon myself. I think that the larger bottles are indeed sweeter because they contain more syrup. I think that they contain more syrup because of the way the soda is consumed. A small bottle of soda will be drunk (drank, drinked???...Ok I'm not an English major) directly from the bottle whereas a large bottle will most likely be poured into a glass over ice. A soda with more syrup will taste better than one with less as it is diluted by the melting ice. Again, this is mere speculation, but that's my 2 cents!

Surely there is an engineer who works for a soda company that could comment? They probably spend their breaks drinking soda...

I agree with dag here, they put more syrup in the larger bottles to compensate for the dilution of the ice which melts fast in soda. If you have ever poured a can or smaller bottle over ice you would notice the difference in taste. The more you open a bottle and close it you lose the carbonization. Once open they never seal again fully. movement and opening a bottle quickly reduces the CO2 content no matter how much you or at any rate you drink it. Coke does become sweeter when it gets flat and tastes horrible when warm. I would think because the carbonization used is causing your taste buds alter the taste you get. If you have ever drank it warm or slightly warm or when flat at different times you will notice that you can taste more of the flavor at these times.

I haven't read any responses, but quite simply, a larger bottle takes more time to consume. Due to this extra time to consume the bottle, it is being handled much more than a small bottle. Any handeling at all will reduce carbonation. It just Loses it's carbonation more than a smaller size bottle would and seems to be much sweeter.

Volume vs cost is not the issue. Someone needs to inform Roger about the effects of drinking too much soda water. The carbonation ruins your bones and the acids have an extremely adverse effect on your throat, stomach, etc. I had a freind that drank 4-16 oz. bottles a day (I won't say what brand) and it ate holes in his throat. In other words, Roger is an idiot!

The larger bottle losses CO2 and acidity making the last of the pop taste sweeter. He needs to buy even larger bottles (like a draft beer keg) and install a CO2 injector so that the pop tastes the same from the first sip to the last.

The flavor question certainly generated an interesting set of responses. All have some level of merit. However, all soda within the same flavor or formulation would have the same volume of carbon dioxide regardless of size. Colas have about 4-4.5 volumes of gas incorporated into the liquid when produced and packaged. That means the gas volume is that multiple of the bottle size. Orange flavors would be down in the 2 range. A non-carbonated product such as tea or water would have nitrogen as the headspace which would not dissolve in the liquid, thus only adding internal pressure so that the bottle would not crush. A larger bottle would have the same amount of carbon dioxide per ml as a smaller one but it would move into the greater and greater headspace volume as it is opened and closed. Thus indeed, the flavor would change and become less acidic and sweeter over time, even the same day if sufficient time passes between swigs.

Do you have references to support your assertion that the gas concentration is maintained the same at the time of bottling? If I was running a bottling plant, and found that I could reduce the initial pressure in the larger bottles and still provide the same standard of product to the end user, I would certainly do whatever would minimise my total costs. However, I will happily bow to superior knowledge.

BTW, if the problem really is solely due to the increased number of openings, Roger has an unusual mode of communication to go with his soda-pop addiction - most people would describe such a situation in terms like "the large bottles go a bit flat before I can finish them".

I think there's no difference in sweetness between the two sizes when the soda is first bottled, but the larger bottle gets sweeter and sweeter as time goes on because sugar is a heavier molecule than the water it is initially dissolved into and it eventually settles towards the bottom. Unlike salts, which, when dissolved into water, form ionic bonds which are relatively strong, sugar forms much weaker covalent bonds, and, over time, the sugar will tend to gravitate to the bottom of the container, making it sweeter than the top of the bottle. One of the effects of the carbonization is that the soda "mixes" itself when the cap is released, so the effect of sitting on the shelve is minimized.

Also, as the pressure of the soda lessens (with less soda in the bottle), one of the forces that keeps the sugar dissolved is removed, and the sugar starts to separate from the water solution.

I have to agree with posts 35, 36 & 37. Carbonation is not the factor here. The more likely answer is the sugar effect mentioned above. All my experience points to a loss of carbonation has no affect or even reduces sweetness.

I also agree there is the same amount per volume of CO2 in either small or large bottle. I am surprised though that we have not heard from somebody who works in bottling, to confirm or deny the CO2 effect.

Oh, by the way, cola tastes much better if it is 40 to 45 degrees F than at 32 degrees F. Especially Cokacola.

Exactly! This is why you should always shake your pop up before you open it. :^))

I think it is all to do with the loss of CO2. I have a device to "pump up the bottle" to help maintain "the fizz", this also has the effect of maintaining the original flavour longer.

Pumping air into the bottle should have no effect on the release of CO2. It's only affected by the Partial Pressure of CO2 in the gas above the liquid and that is unaffected by increasing the pressure of air.

That is not quite correct.
Only the liquid that is in contact with the top surface is affected in any way by the constituents of the gas. Elsewhere, the rate of desorption is controlled purely by the pressure and other local conditions.

What is true is that the equilibrium condition is not strongly affected by the pressure of the other gases.

Let me try this from a different angle than chemistry. It's agreed that the "more sweeter" phenomina is inversely proportional to the amount of CO2 left in the jug. Might it be that the more bubbles there are in the beverage the less surface area of liquid is in contact with the tounge, so the fewer "sweet" receptors are activated?

If this were the case soda (or pop) would appear to be sweeter as the amount of carbination decreased.

Technically, the bubbles themselves are sites where the carbonic acid is decomposing into various ketones and amyl groups. The bubble of carbonate (CO+CO₂+CO_{3^{- )}} would; when pressure is released, be forming a product that is actually "sweeter" to the preception of the tongue than the actual sugars in the liquid.

This research is all well and good, but I've had flat soda and I've had "fresh soda" with full carbonation and I have no doubt the flat soda tasted sweeter. So either I'm an anomaly, or the research you're quoting is missing the forest for the trees.

Who said the bottles were made of plastic???

I read some of the previous posts, skimmed most, and reached the following conclusion. All of you have approached this from the blunt end of the stick. The question is not: "does the bottle lose pressure?", nor "is the carbonation different?", it is "is there really a difference in the taste, or is Roger imagining it?" Roger may well be imagining it, but it is HIS tongue, and if it really tastes sweeter to him, then it IS sweeter to him. I cannot taste it with his tongue, so cannot experience directly what he does. None of the rest of it, no matter how interesting it is, nor how enlightening (and trust me, this thread has been BOTH!) at all matters.

There's no accounting for taste.

Worked in a bottling plant and the same soda pop went into the big and little bottles.

Other plants may have some different formulas, but the computer we set had the same amount of sugar water per ounce of syrup

1. The real for the larger bottle's going flat is that some sneaky person drops a minto into the bottle, thus causing the bottle to rapidly lose its carbonation. :)

2. Historically, it was widely believed that 6-oz bottled cokes tastes better than the 10-oz bottled cokes. CO2 diffusion is hardly an issue, since the diffusion is practically limited to that which can move through the cork under the cap. The bottles were made of heavy glass. Does this date me?

BTW, chill the bottle thoroughly before opening.

Yeah, those little 6 1/2 ouncers were great! Real glass, reusable bottles are a thing of the past. Now, we think of a regular 10 or 12 oz. as too small. By the way, here in Texas the original Dr Peppers made with cane sugar are making a comeback. Almost all soft drinks are now made with corn sucrose.

The issue is not the syrup but the carbonation which is added to the syrup/water mix at the time of bottling. Can you enlighten us on this.

I wonder if it as simple as a larger bottle = larger surface area = more nucleation sites for bubbles to form = more carbonation lost = less acidic/sour taste from carbonic acid = concentration shift to the sugars = sweeter taste.

I think not - Volume/Surface_area increases as linear dimensions - you will more CO2 due to nucleation, but the increase in original volume is greater than proportional to the increase in nucleation - hence the loss in concentration due to this cause should be slower for larger bottles. If it's post-opening leakage we are looking at, the increase in CO2 loss looks to be solely due to increasing the number of openings before the drink is finished.

Ok then, one thing that everyone seems to agree on is that the loss of carbonation is at least partly to blame for the sweeter flavour.

I'll assume that the soda syrup is mixed, combined with carbonated water and then bottled under cold or cool conditions, and then capped. A certain ammount of CO₂ will come out of solution until an equilibrium pressure is reached. In a steel bottle, I would concede that the net pressure on the system will be the same regardless of the bottle size. Considering that the plastic bottle is somewhat elastic, and a larger bottle is more elastic than a smaller bottle, would a larger bottle not increase volume more than a smaller bottle? Or is that also a linear relationship? If it does, a greater volume from expansion would allow more carbonation to escape, and subsequently when the void increases as the soda is consumed, the new equilibriums that are reached when the bottle is recapped would reduce the carbonation faster.

Roger is wrong!

This whole article is about Dan stating the fact that Roger can save money!

Roger may not like the taste and refuse to drink it that way but this does not make Dan wrong.

But Roger could say Yep I would save money on my drinks but not on the ice and the cooler I would have to buy and tote around all day long on the job site, and I would have to hear you bitch because we are not taking enough breaks from work and you keep running out of cigs because you only buy one pack at a time you cheap bastard!!

As for the difference in taste, if Roger was to drink the entire drink at one time he probably would not notice(as pressure will effect taste) as everyone has stated, but as a mountain dew drinker here I know they can be different. I will only drink MD from a can no Plastic bottles at all. If I must drink plastic it will only be pepsi or coke as mountain dew varies way too much in plastic.

They may try to keep the water the same at different plants but if I drink one from South Carolina, I beleive from Cheraw SC. it tastes alot different than from up north somewhere.

Have Fun

Bill Cz

Bill,

Good point, however, it's not about the money, it's about flavor.

Taking your input of reading the question "correctly", one might suppose that, if Dan did actually drink "constantly" (I read this to be in the range of liters per hour)then he should be able to polish off any size bottle without noticing any flavor loss.

Dwight

Over the years Roger's pancrease has began to fail thus he is becoming more aware of sweet item if he consumes 2 litres as opposed to 1 litre his body is not able to cope thus it seem to sweet... again another stupid task with limited info to draw everyone into a useless endless debate.

I thought his horse had diabetes and his mates were gaming him...?

I totally agree. Nobody has worked out the strength of a bottle or the degree of deformation under pressure. For what we know a plastic bottle can withstand terrific pressure with a very limited amount of deformation. I am a Coke drinker and all I can say is that Coke in a 1.5 liter bottle tastes sweeter that the equivalent in 330cc cans. However I have to admit that the very first sip probably tastes the same. As more and more coke is consumed from the liter bottle, part of the fizz goes since more space is available for expansion of the gas inside, and the drink tastes sweeter. On the other hand I have never left a can half empty for any significant amount of time. It may well tast the same.

Another answer that is at best so badly worded as to be impossible to interpret reasonably. Specifically, the surface-area/volume is larger in small bottles than in large, so the surface will have more effect in the smaller bottles, contrary to the apparent implication.

Isn't that pretty much exactly what I posted in #22, 50, and 58???

If you are referring to the "official" answer (as in "and the answer is"), I think you are being overly kind. The authorised version appears to be talking about the time to reach equilibrium, which would be faster for the smaller bottle, rather than slower as implied by the text**. In addition, I for one couldn't see what logical connect that reply was assuming between the rate of reaching equilibrium and the strength of the contents. Even though I found your contribution hard to interpret and incomplete, I didn't think what you wrote was basically nonsense.

*It may be that the reply was just poorly written, and they meant that the larger bottles took longer for the gas content to decay, so thy didn't need to be so heavily gassed in the first instance. But that would interact only indirectly with the proportion of free space (which the manufacturer is free to adjust to an "optimum" in any case)

The answer:

the one liter bottle reaches equilibrium more quickly than the larger bottles due to lower surface area at the soda gas interface and a lower volume of air in the bottom that needs to be brought up to pressure to reach equilibrium.

Various points of mine:

a 2 or 3 L bottle does not have 2 or 3 times the surface area as a 1L bottle. Also; the void above the soda is not 2 or 3 times greater.

Henry's law - the solubility of a gas (in g/L) is directly proportional to the partial pressure (in atm) of the gas above the solution.

I'll assume that the soda syrup is mixed, combined with carbonated water and then bottled under cold or cool conditions, and then capped. A certain ammount of CO₂ will come out of solution until an equilibrium pressure is reached

subsequently when the void increases as the soda is consumed, the new equilibriums that are reached when the bottle is recapped would reduce the carbonation faster.

I guess you're right about incomplete. If I would've strung all those thoughts into one complete post, I think it would have been closer to what I was thinking.

It's still not clear: are you suggesting that adsorption into the surfaces are replenishing the CO2 in the fluid, so the proportinately larger surface area of the small bottle is helping maintain the carbonation? (The plastic surface will not even absorb a monolayer of CO₂; combined with the low solubility of CO₂ in PET, such effects would be minuscule compared with the other things that are going on).

Nothing is being absorbed or adsorbed. The original condition is CO2 gas disolved in water at about 2.5g/liter. At 1atm and 10deg C, that solution is now saturated, and you cannot dissolve any more gas into it. The only way to supersaturate the soda is to increase the partial pressure of the CO2 past 1atm. This is Henry's law and the relationship between pressure and gas dissolution is predictable and linear. Soda is a supersaturated solution of CO2 gas. When the pressure of the system (gas and solution) is lowered -i.e. opening the bottle, the gas begins to come out of solution. So if you put a pressure guage on the bottle, when it gets to the consumer lets say the pressure (of the 50mL void of gas) reads 5 atm - that pressure would support 12.5 g of CO2 in one liter. For argument sake, assume 250mL is removed for drinking and is done so efficiently that the solution has lost very little CO2. When that bottle is closed again, the pressure guage will read 1. The remaining 750mL is still supersaturated to 12.5g/L, so 750mL contains 9.38g, but it will lose about 1.5g from solution to increase the pressure of the now 300mL void to the point that the supersaturated solution is in equalibrium again. But this time the pressure will only read about 3.5 atm. The next time a glass is removed from the bottle, the same thing is happening, except now there is less actual CO2 remaining - 8.75g/LX0.5L=4.38g, and the void is now 550mL. When the pressure guage makes it down to 1atm, there will be 2.5g/L CO2 in solution, and no further gas will leave the solution-the soda is officially flat. I have no idea at what point that the sweet overpowers the acid, but assuming the portion size remains the same, a larger bottle would lose carbonation at the same rate, so more of it would remain when the carbonation vs sweet point is reached.

That is agreeing with some of what I said - albeit going into more detail on overpressure. It's more-or-less the inverse of how I read the "official" response, which I had the impression you were trying to support. Perhaps I was inferring something that wasn't there?

Well to me the loss of carbonation in the larger bottles was an obvious answer (to a chemist), so I never went into any detail on it. I thought the answer revolved around taste, and perception of taste.

Sometimes, these challenges are written so ambiguously, that the obvious answer is the least likely. Take the Obsidian dating challenge - I was searching for something much deeper than the answer I hit on my first google.

I'm still not certain that loss of carbonation after opening is either the proper answer or the official one.

I agree. Further; when a beverage is carbonated - to counteract the loss of carbonation, companies carbonate to a pressure just less than the container can safely stand. At these levels, the disolved CO2 can only make Carbonic acid to a limit. Then it starts to create ketone and amyl groups. These organic compounds are found in artificial apple, banana, grape, and cherry flavourings, and are percieved as sweet by taste buds. Thats why I thought you were on the right track when you were talking about the strength of the container.

That was my initial guess, but I couldn't find confirmation that this actually happened. The secondary bit on diffusion through the bottle leads to a similar conclusion (not only can smaller bottles be more heavily carbonated, but they also need to be if the same concentration is to be achieved at the end of shelf life) - and at least in the end I found support that the diffusion rates really were significant.
So I still believe that small newly-opened plastic bottles that are well inside their shelf-lives are usually heavier-carbonated; the larger number of openings for the bigger bottles also means they will lose a larger proportion of the initial content before you finish them - but that doesn't appear to be what Roger was complaining about (heaven forfend that he drinks the stuff so quickly that multiple openings are not that significant)