Food Safety of Fruit Beverages

Hi all, I have read though these forums a number of times, but this is my first time posting.  I work for a beverage manufacturing company, and we essentially make fruit nectar's (10% real fruit). I am trying to understand any risks (bacteria, yeast, or mould) that may be missing from our processes.  Any feedback would be greatly appreciated.  The process is as follows: We pasteurize all of our juices at 94 degrees C for 60 seconds, and fill them hot into glass bottles that have a plastisol seal for an airtight fit.  The glass bottles are rinsed with a sanitizer solution prior to filling.  The bottles are then inverted for 2 minutes to achieve sterilization of the head space. The finished product pH ranges from a 3-3.35.  We send samples from each batch to a third party lab for pH verification, and microbe testing.  We constantly get results back stating 0 CFU/ml for bacteria, and 0 CFU/ml for yeast.  The finished product also contains 500 ppm of Potassium Sorbate. What are the risks that one or some of the bottles may get contaminated? Is there any risk? If something were to get contaminated, would it most likely be a one off packaging issue?  I am mostly concerned about molds, but the product does have the Sorbate, and very little oxygen that would allow for growth. Lastly, with our process, the hot fill creates a vacuum which in-turn creates the airtight seal.  Would there be any benefit to purging the bottle prior to filling? Or will the N2 be forced out by the vacuum that forms from the hot fill? I appreciate any and all feedback!

The process and the product is quite robust.  The main concern would be loss of temperature during pasteurization, and hot filling.  Secondary concern is loss of package seal.  Validate the process and verify it regularly and you'll be ok.

I don't see any benefit of N2 unless you wish to extend shelf-life.  You can get flavor degradation over time if you have added flavors which the N2 can help prevent.  But, even that happening would be a low possibility because of the low pH which helps protects against flavor degradation.

The process and the product is quite robust.  The main concern would be loss of temperature during pasteurization, and hot filling.  Secondary concern is loss of package seal.  Validate the process and verify it regularly and you'll be ok.

 

I don't see any benefit of N2 unless you wish to extend shelf-life.  You can get flavor degradation over time if you have added flavors which the N2 can help prevent.  But, even that happening would be a low possibility because of the low pH which helps protects against flavor degradation.

Thanks Ryan.  

That is what I figured, as long as we closely monitor the fill temp (which we do) and the seal is intact there is little to no risk of contamination at all.

As far as the N2, we currently get a 9 month shelf life on our products, but are hoping for 12+.  After 9 months, the flavour of the product fades slightly, hoping that the N2 could help solve this issue.  We include 300ppm of Ascorbic Acid to help with oxidation, but feel as the N2 will help this.

N₂ might help with the oxidation issue - whilst the bottle is under a vacuum, it's a relative vacuum (i.e. lower pressure than atmospheric pressure) rather than absolute. Having the as little O₂ as possible in the small amount of gas in the headspace could theoretically help.

Predicting the magnitude of the difference that it might make is not easy though!

It might be a worthwhile exercise to rent the kit to do the N₂ addition if you can, so you can try it before you have to commit to a purchase. It's still a difficult call though, as you're potentially not going to know if there is a benefit until several months down the line.

If most of the colour comes from the juice element then I'd expect it to also vary between products, as some are naturally relatively robust, whereas others are very inclined to fade/brown fairly quickly. The latter will get the most potential benefit, but you might be fighting a losing battle in some cases. I've seen quite a few juice-based products with a 12 month life in clear glass bottle, some of which are still pretty much ok at that stage (as long as they've not been abused too much), whereas for others it really is probably slightly beyond the point at which they're still at their best, even with fairly careful processing, N₂ addition etc.

Otherwise I agree with Ryan M - the overall combination of product/process looks pretty solid to me, and the pasteurisation/hot fill and sealing stages are the most likely points for potential micro issues; the latter being a potential source of sporadic issues if an occasional cap is either not sealed properly or slightly damaged/deformed.

N₂ might help with the oxidation issue - whilst the bottle is under a vacuum, it's a relative vacuum (i.e. lower pressure than atmospheric pressure) rather than absolute. Having the as little O₂ as possible in the small amount of gas in the headspace could theoretically help.

Predicting the magnitude of the difference that it might make is not easy though!

 

It might be a worthwhile exercise to rent the kit to do the N₂ addition if you can, so you can try it before you have to commit to a purchase. It's still a difficult call though, as you're potentially not going to know if there is a benefit until several months down the line.

 

If most of the colour comes from the juice element then I'd expect it to also vary between products, as some are naturally relatively robust, whereas others are very inclined to fade/brown fairly quickly. The latter will get the most potential benefit, but you might be fighting a losing battle in some cases. I've seen quite a few juice-based products with a 12 month life in clear glass bottle, some of which are still pretty much ok at that stage (as long as they've not been abused too much), whereas for others it really is probably slightly beyond the point at which they're still at their best, even with fairly careful processing, N₂ addition etc.

 

Otherwise I agree with Ryan M - the overall combination of product/process looks pretty solid to me, and the pasteurisation/hot fill and sealing stages are the most likely points for potential micro issues; the latter being a potential source of sporadic issues if an occasional cap is either not sealed properly or slightly damaged/deformed.

Thanks PHruit,

If we were to do some accelerated shelf life testing of bottles that were purged with N2 and bottles that were not, do you believe we could get a fairly accurate representation of the product differences? From my experience, accelerated shelf life testing is typically not the best indicator/most accurate, but may help in this instance.

Pardon my ignorance but what do you mean when you say "abuse" are you talking about things like UV light etc? - Our labels do have a UV protecting film on them, granted the label only covers about 70-75% of the bottle.

Thanks again.

I'm similarly a bit sceptical of accelerated testing for organoleptics. If you've got easy/inexpensive access to it then I'd give it a go, as it's more data than you have now, but I'm not sure it's a real replacement for actual time in bottle.

For "abuse", I'm thinking excessive temperature, light etc. - it might be ambient stable, but that doesn't mean it should reasonably be expected to withstand extended period sitting in direct sunlight in a hot shop window or similar.

I often used to see a spike in organoleptic complaints in October, when seasonal shops and cafes hadn't properly rotated stock and some of the bottles had sat in direct sunlight all summer...

you can carry out some Basic Physical tests at your end like checking temp with Thermometer every half hour at Beverage filling station,Ph checking with hand held Ph meter or Universal Ph paper,Seal integrity,Checking of Vacuum during filling and when Bottle Cools with Vacuum tester/ Vacuum test Gauge for Beverages and Brix Checking with Refractometer,Organoleptic checking,Color
Checking and if possible Acidity as Citric acid by Titration with Standard NaoH both when Batch is Ready after adding All ingredients and when Bottle is filled,Recording the Findings in Log Book/ Sheet with Batch No ,Date and Time.
Any Mistake during Batch preparation like Ommission of Citric acid to keep PH below 4.5 could be Disastrous as you cannot Rectify such Mistakes after Filling the Bottles leading to wastage and economic loss when results arrive from outside lab.