Considerations for achieving shelf-stability in ready-to-drink (RTD) beverages including spirit-based cocktails, wine-mix cocktails, seltzer, hard kombucha, and other trending formulations
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As established by several beverage industry reports, ready-to-drink (RTD) beverages are one of the fastest growing market segments over the past 5 years. At Scott Laboratories, we have seen this growth reflected in the number of our clients starting to produce RTD beverages.
The RTD segment is extremely diverse when it comes to beverage composition, package, and production setup. However, we’ve noticed similar challenges across the board when it comes to achieving shelf-stability.
We know shelf-stability is not a sexy term, in fact one could call it boring and complicated. That being said, having a shelf-stable product – one that does not re-ferment in package or develop unwanted aromas, hazes, or precipitates – is absolutely critical to maintaining product quality and protecting your brand’s reputation and profitability. Furthermore, shelf-stability is often more complicated in RTD beverages than in traditional beverages like beer, spirits, and wine.
In this article we’ll cover some of the important considerations for keeping your product in good shape on the shelf.
WHY IS STABILIZATION SO COMPLICATED IN RTDs?
Unknown Territory
Many producers making RTDs are existing breweries, distilleries, etc… and RTDs can present new stabilization challenges compared to beer, spirits, and other traditional beverages.
Many RTD beverages have additions of flavoring, concentrates, juices, fruits, wine, ciders, etc. Some of these products are prone to oxidative damage which can manifest as browning, loss of aroma, development of bruised apple/honey character. Some of these can also cause “colloidal instability” which can result in filtration challenges, hazes, and precipitates.
Refermentation
Many RTD beverages contain residual sugar the additions mentioned above (flavoring, concentrates, juices, fruits, wine, ciders, etc). Even if these products are aseptic, their residual sugar can be consumed by spoilage yeast and bacteria picked up before or during packaging and result in refermentation on the shelf.
While residual sugar is the primary reason for refermentation, many organic acids present in fruits (and even ethanol itself!) can be metabolized by certain spoilage organisms. Therefore, it’s common to see additional anti- microbial measures employed in RTDs for extra insurance on the shelf.
Co-packing
Many RTD beverages are packaged at co-packing facilities. This can mean that the producer is removed from the stabilization and packaging process, which is the final critical control point for the product. Finding a knowledgeable co-packer with the right capabilities to stabilize your specific product is critical, especially if you personally don’t have the expertise.
WHAT STABILIZATION OPTIONS ARE OUT THERE?
There are several methods available for addressing microbial stability. We can broadly categorize these methods into two categories – ones that leave the product susceptible to microbial contamination downstream, and ones
that do not. For this reason, RTDs often employ a combination of both – the first to reduce the initial microbial load and the second to ensure stability in the final package on the shelf.
The table below outlines pros and cons of many common methods used in RTD cocktails:
| Method: | Pros: | Cons: | Susceptible Downstream? |
|---|---|---|---|
| Filtration | • Microbial reduction • Clarity • Many technologies/grades available | • Product is susceptible to microcontamination downstream of filter | Yes |
| Sulfur Dioxide (SO2) | • Inexpensive, • Antimicrobial plus antioxidant properties | • Needs to be labeled • Consumer aversion • Potential reaction with aluminum cans that results in defects (H2S) • Efficacy is pH dependent | Yes* *depending on beverage pH and amount of SO2 |
| Flash Pasteurization | • Small footprint • Effective reduction in microbial load | • Product is susceptible to microcontamination downstream of flash pasteurization | Yes |
| Tunnel Pasteurization | • Eliminates microbial risk in the final package | • High capital costs • Large footprint • High energy costs • Potential sensory impact | No |
| Persistent Preservatives (sorbates, benzoates) | • Easy application • Inexpensive • Eliminates microbial risk in the final package | • Needs to be labeled • Consumer aversion • Potential sensory impact | No |
| Velcorin | • Effective microbial elimination • Easily incorporated into existing process • No sensory impact • Does not need to be labeled | • Not approved for all beverage categories • pH dependent • Cannot handle extremely high microbial loads (>500 CFU/mL) | No |
EXAMPLE SETUPS:
In this section we’ll explain the stabilization setups for a few real-world RTD products we frequently see:
Off-dry or Fruited Cider:
Crossflow + SO2 + Velcorin
Consumers often expect a certain level of clarity in cider, so crossflow filtration is a great first step in the process to reduce solids and reduce some of the microbial load. Cider, like wine and fruit juice, is prone to oxidation, so sulfur dioxide (SO2) is employed as an antioxidant. If the cider had no residual sugar and were going into a glass bottle, SO2 may also provide adequate antimicrobial protection. However, SO2 levels must be kept low in cans (under the threshold required for antimicrobial protection) to avoid the development of sulfur off-odors. Therefore, Velcorin at packaging is a great choice for inactivating any remaining organisms and preventing refermentation.
Hard Kombucha:
Flash Pasteurization (after final blending) + Velcorin (at packaging)
Kombucha can be quite difficult to filter, and consumers often tolerate some level of haze and particulate matter so filtration may not be necessary. To achieve microbial stability, a two-pronged approach can be used – flash pasteurization prior to packaging and Velcorin at packaging. The initial flash pasteurization does the heavy lifting of reducing microbial load though it cannot continue to protect the beverage AFTER treatment. Therefore, Velcorin at packaging can kill any organisms the beverage may have picked up after flash pasteurization or during packaging.
Why not just use Velcorin? Kombucha has a high microbial load that Velcorin may not be able to handle on its own.
Spirits-based Cocktail:
Velcorin
Sprits-based cocktails can be one of the simpler RTDs to stabilize, depending on formulation. Spirits, due to alcohol content, are quite resistant to microbial issues. In these RTDs, the additions of filtered water and aseptic flavorings do not significantly increase the microbial load of the product. However, the product is at risk of picking up spoilage organisms during processing/packaging that could consume residual sugar. So, Velcorin at packaging provides appropriate insurance against any issues on the shelf.
EVERY BEVERAGE HAS ITS OWN PATH TO STABILIZATION
At Scott Laboratories, we often say that every beverage has its own path to stabilization. The beverage formulation, raw materials, pH, package, and production setup all play a role in determining the most appropriate stabilization process. While it can be boring and complicated, its our area of expertise. For more information on anything mentioned in this article or to chat with a specialist about your specific beverage, please visit scottlab.com or contact us by clicking the link below.