Root cause of bottled water having a plastic smell?

Hi everyone! 

I was hoping someone might be able to help me. We produce still bottled mineral water and have lately been experiencing some issues with the smell of the product. This is a little out of my depth, as the issue lies with the PET bottles and not with the water itself. 

We use water from an underground aquifer, which is then undergoes reverse osmosis treatment, and then bottled. However recently we have found that the bottled water has an extreme plastic smell when opened - often so strong that it overpowers the taste as well, making one think the water tastes like plastic. 

We blow mold our own bottles at our facility. The bottles are used on the First In First Out rotation system - but for every fresh batch of bottled water produced we experience the plastic smell. 

I am no expert in packaging and have researched it a bit, but it seems to me that mostly the issue arises when bottled water has been standing for quite some time (mostly when exposed to direct sunlight) and not very soon after bottling as in our case. We taste our water after approximately one or two days on the floor (no exposure to sunlight). 

Are there any packaging experts or others who might be able to assist as to why this could be occurring? Could it have something to do with the temperatures at which the bottles are produced? Could the fact that the water has undergone revere osmosis have something to do with it? 

This is definitely not a sweet smell as would be caused due to Acetaldehyde formation - we have had this before and resolved the issue. 

I would really appreciate any assistance! 

thank you, Anna :)

Hi everyone! 

 

I was hoping someone might be able to help me. We produce still bottled mineral water and have lately been experiencing some issues with the smell of the product. This is a little out of my depth, as the issue lies with the PET bottles and not with the water itself. 

 

We use water from an underground aquifer, which is then undergoes reverse osmosis treatment, and then bottled. However recently we have found that the bottled water has an extreme plastic smell when opened - often so strong that it overpowers the taste as well, making one think the water tastes like plastic. 

We blow mold our own bottles at our facility. The bottles are used on the First In First Out rotation system - but for every fresh batch of bottled water produced we experience the plastic smell. 

 

I am no expert in packaging and have researched it a bit, but it seems to me that mostly the issue arises when bottled water has been standing for quite some time (mostly when exposed to direct sunlight) and not very soon after bottling as in our case. We taste our water after approximately one or two days on the floor (no exposure to sunlight). 

 

Are there any packaging experts or others who might be able to assist as to why this could be occurring? Could it have something to do with the temperatures at which the bottles are produced? Could the fact that the water has undergone revere osmosis have something to do with it? 

 

This is definitely not a sweet smell as would be caused due to Acetaldehyde formation - we have had this before and resolved the issue. 

 

I would really appreciate any assistance! 

 

thank you, Anna :)

Hi Anna,

Do you mean that every test shows the defect ?

How about the bottle smell before filling ?

Recycled Plastic Pellets ?

If all odour tests are defective (!) / there have been no changes in bottle manufacture/ water process and input water-pre bottling water smells OK,  I would try using an alternative source of plastic to compare result. + try any older remaining plastic raw material from time before problem occurred

Might be worthwhile  checking your supplier of the plastic preforms  to see if they have changed any supplier/plastic type. Otherwise storage temp of the preforms?? Just an idea.

Regards

Kathy

Hi Anna,

The root cause might be high values for AA.

AA is formed by thermal degradation of PET resin.  The amount of AA generated is dependent on the molding process conditions and the thermal stability of the PET resin.  In certain applications, the AA content in preforms must be kept to a minimum to avoid changing product flavor and therefore must be measured periodically by a gas chromatograph in ppm or µg/l.

POSSIBLE CAUSES

• Excessive melt degradation causing increased AA formation on the preforms.
• Inlet resin pellet temperature too low causing excess shear heat during plasticizing.

There is always a recommended AA values depending on the size of the preform/ bottle. Confirm with the supplier the AA values for the preforms and whether they are in compliance with the requirement of the preforms sizes.

Regards,

Maurice.

Go to the supplier of the PET resin/pellets first and request assistance, formulation of the resin could be the main reason.

Another issue that could be the culprit - what is the medium that you are using for the RO system, how often is it serviced and where it is located?

Might be worthwhile  checking your supplier of the plastic preforms  to see if they have changed any supplier/plastic type. Otherwise storage temp of the preforms?? Just an idea.

 

Regards

Kathy

HI Kathy! Thank you! I have tried researching the optimum storage temperature for plastic pellets as well as the preforms but could not find much. Do you perhaps have any suggestions? We receive pellets, then make our own preforms. The temperatures in the storage areas can reach about 40 degrees Celsius. Is this too hot when stored for longer periods of time? 

Hi Anna,

The root cause might be high values for AA.

 

AA is formed by thermal degradation of PET resin.  The amount of AA generated is dependent on the molding process conditions and the thermal stability of the PET resin.  In certain applications, the AA content in preforms must be kept to a minimum to avoid changing product flavor and therefore must be measured periodically by a gas chromatograph in ppm or µg/l.

POSSIBLE CAUSES

• Excessive melt degradation causing increased AA formation on the preforms.
• Inlet resin pellet temperature too low causing excess shear heat during plasticizing.

There is always a recommended AA values depending on the size of the preform/ bottle. Confirm with the supplier the AA values for the preforms and whether they are in compliance with the requirement of the preforms sizes.

 

Regards,

 

Maurice.

Hi Maurice! Thank you! We make our own preforms from the pellets. So I can't contact the supplier regarding the AA values for the preforms. We have had an AA problem in the past - however this was a sweet, fruit like smell. Whereas the smell we are currently struggling with is a strong plastic smell. I will have a chat with the supplier to see whether they might have changed anything in the pellets they supply us. Thank you!

Go to the supplier of the PET resin/pellets first and request assistance, formulation of the resin could be the main reason.

 

Another issue that could be the culprit - what is the medium that you are using for the RO system, how often is it serviced and where it is located?

Hi! Thank you! We run our water through activated carbon filters, and then into the RO system (located on our premesis) which makes use of nano filters. The system is serviced every two months, with certain filters being replaced monthly. 

Hi Anna

It seems that a storage temp of  below 40 deg C is recommended for the plastic pellets - not sure about preforms but I would imagine around the same.

Regards

Kathy

Or you may be familiar with 8-Nonenal that can be present in either your resin for caps and/or the bottle itself. The 8-nonenal is normally associated with plastic taste.

Also, while it may not be your PET bottle itself, does it come with laminate? The 8-nonenal may also come from the flexible packaging. Since Normally, PET does not act as functional barrier for chemical migration and if the laminate also does not have the plastic barrier, 8-Nonenal may migrate to your water.

Suggest that you check each of the material for its presence and start from there. Making the water stand (in bottle) in elevated temperatures may facilitate faster chemical migration.

Do you also conduct sensory of water before packing? If yes, then it may not be the cause.

Or you may be familiar with 8-Nonenal that can be present in either your resin for caps and/or the bottle itself. The 8-nonenal is normally associated with plastic taste.

 

Also, while it may not be your PET bottle itself, does it come with laminate? The 8-nonenal may also come from the flexible packaging. Since Normally, PET does not act as functional barrier for chemical migration and if the laminate also does not have the plastic barrier, 8-Nonenal may migrate to your water.

 

Suggest that you check each of the material for its presence and start from there. Making the water stand (in bottle) in elevated temperatures may facilitate faster chemical migration.

 

Do you also conduct sensory of water before packing? If yes, then it may not be the cause.

Thank you so much - I have read up on 8-nonenal. Is this present in the pellets? Does it produce the smell only when exposed to certain conditions e.g. high storage temperatures, or does the plastic smell depend on the amount of 8-nonenal present in the pellets? Sorry for all the questions, I am struggling to get a lot online. 

Cap a few empty bottles and let them sit in a warm location for a few days.  Then open the bottle and see if you detect a plastic smell.

Or cover emply bottles with aluminum foil instead of the cap and do the same thing.  If you detect a plastic smell, then it likely is coming from the bottles and not the caps.

There can be small chain molecules in the plastics that are migrating into the water.

Cap a few empty bottles and let them sit in a warm location for a few days.  Then open the bottle and see if you detect a plastic smell.

 

Or cover emply bottles with aluminum foil instead of the cap and do the same thing.  If you detect a plastic smell, then it likely is coming from the bottles and not the caps.

 

There can be small chain molecules in the plastics that are migrating into the water.

Thank you! I will definitely give this a try! 

.

Thank you! I will definitely give this a try! 

Hi Anna,

Were you able to find a solution to your plastic smell issue? I am currently investigating something similar to what you describe and would love to know what you discovered in your process. Was it the 8-nonenal?

Thanks