Whether it’s soda, sparkling water, or the more recent popularity of carbonated coffee, tea, or juice, CO2 is essential for creating those bubbles necessary to ensure a beverage is consistent and safe.
Don Pachuta, PhD, president of Airborne Labs International, Inc., Somerset, N.J., says the quality of CO2 used in beverage applications was historically often overlooked with minimal testing done. This changed radically, however over the last 20 years.
“Robust CO2 quality control not only ensures the desired pleasurable sensory impact of the beverage but also for its freedom from potential ‘health impacting’ harmful effects that can arise from various undesirable impurities in the CO2,” he says.
Moreover, as more “non-traditional” sources of CO2 are explored and employed, the issues of CO2 quality maintenance become more challenging as new potential source-specific impurities must now be carefully studied, and related impurities identified, removed, monitored, and subsequently controlled by appropriate purity standard-setting bodies. These include such as the Compressed Gas Association (CGA), International Society of Beverage Technologists (ISBT), European Industrial Gases Association (EIGA), FDA, and other governmental or international standard-setting groups.
“It must be understood that all CO2 quality assurance processes involves a complex, multistep supply-manufacturing-delivery-storage-beverage manufacturing chain, which starts with the composition of the original feed gas source of CO2 through its final infusion into a beverage product,” Dr. Pachuta says. “For reasonable economics, CO2 supplies need to be produced and stored relatively local to their end users. The key is that many diverse and new non-traditional types of possible localized CO2 sources are continually being evaluated for economic, consistent, and sustainable supply reasons.”
Recent reported shortages of beverage-grade CO2 this last summer in Europe and other areas highlighted the need for a more stable and local CO2 production picture.
Guidelines in Place
The CGA publishes several industry consensus standards on the production, storage, and transfer of CO2. CGA published its first CO2 commodity specification in 1973 and periodically updates it and other CO2 standards and guidelines to address new uses and feed gas sources. These specifications provide limiting characteristics and identify recommended testing methodologies for the analysis of potential contaminants in liquid, gaseous, and solid CO2 for various uses.
ISBT has a set of guidelines that establishes production and feed gas considerations, finished product impurity levels, and analytical method recommendations for beverage-grade bulk CO2.
Larry Hobbs, executive director of ISBT, says the CO2 guidelines established by the organization’s Beverage Gases committee were created by a group of experts that included members of the beverage industry as well as the suppliers and the producers of CO2.
“Their work took several years to complete and the result has been to improve the quality and consistency of CO2 used in the beverage industry,” he says. “As a general practice, suppliers provide certificates of analysis upon delivery for ingredients, including gases such as CO2 to certify that the material meets the standards established in the contract with the customer. These are backed up by a lot of analysis by the shipper as well as whatever internal sampling and testing programs the customer may have.”
Major gas suppliers like Air Liquide and Airgas (which recently merged), Linde and Praxair (which recently merged), and Matheson produce and sell CO2, and all perform quality testing and periodic third-party testing at approved labs.
John Willenbrock, technical manager for CGA, says CO2 is manufactured in accordance with a company’s standard operating procedures that are developed to meet customer expectations and, in the U.S., for compliance with the Food Safety Modernization Act (FSMA) and FDA’s implementing regulations. Interestingly, CO2 is not only an ingredient in beverages but is also classified by the FDA as a drug among other uses. That’s why it’s important the criteria meet the CGA’s standards identified for beverages and also with CO2 standards for other intended uses.
The testing of CO2 has fortunately evolved over the years—both through more capable onsite production and storage testing equipment, and relatively simple offsite process. This involves taking a small, low pressure gasified CO2 sample that can be internationally shipped when needed as a “non-hazardous” gas sample to a qualified CO2 testing laboratory for a comprehensive quality analysis.
This offsite sampling requires the use of sample containers comprised of inert, specially coated (passivated) materials that will not adsorb the critical impurities of interest such as sulfur agents.
Use of state-of-the-art instruments, both onsite and offsite, allows for the testing of all critical CO2 impurities to the very low (parts per million to parts per billion) levels needed to ensure CO2 sensory desirability and consumer safety.
Significance of CO2 Quality
Unlike many commodity gases such as nitrogen, oxygen, and argon that basically come from non-complex “air” as a primary source, Dr. Pachuta explains commercially produced CO2 for beverages typically originates as a byproduct or a “waste” product from more chemically complex sources.
These include natural wells, fermentation of grains and grasses (corn, molasses, sorghum), combustion of many fuels including coal, fuel oils, natural gas, plus natural gas based-synthesis of soil fertilizers (ammonia-sources), chemical processes (neutralization of mineral acids), synthesis of various chemicals (glycols), and quite recently “anaerobic” digestion of various vegetable, animal, and waste stream biomass materials (biogas).
“In all cases, the trick is to accurately determine the identity, levels and risks of all common types and amounts of potentially harmful sensory or health-impact impurities that may be present from a given CO2 source,” Dr. Pachuta says. “This information is used to design effective industrial cleanup processes, which can consistently remove these undesired impurities down to very low, safe, acceptable levels for use in beverages and other food applications.”
Due to the physical properties of CO2 and the strict controls over the supply chain, the chance of contamination problems with the CO2 is pretty low. Containers of CO2 are under pressure. Pressurized product flows out of the container, prohibiting the introduction of contaminants into the container as long as there is product in the container.
“The safety issues are not so much contamination in the supply chain, but more about safe handling and storage given the properties of CO2 itself,” Willenbrock says. “CO2 is produced, stored, and transferred under pressure, which virtually eliminates the chance for contamination. In a closed container, such as a high-pressure cylinder, CO2’s a liquefied gas under pressure. If you overfill the cylinder and the temperature change increases, the pressure can rapidly increase to an extent that the cylinder can rupture, causing extensive injuries to individuals and equipment.”
Storage of CO2 in tanks and cylinders in enclosed areas without adequate ventilation and atmospheric monitoring are concerns. Even small leaks from equipment could lead to an oxygen deficient atmosphere in the area, exposing anyone entering to possible asphyxiation. Even with what may be considered “sufficient oxygen” to sustain life, an environment containing high levels of CO2 can cause personal harm very quickly.
Recent CO2 Trends
With an increasing interest in the use of more economic and non-traditional sustainable sources of commercial CO2, the specific challenges are to design appropriate sampling, analytical methods, test programs, and reasonable purity specification limits that will identify and track the most likely impurity “suspects” present in a feed gas source or produced during the manufacturing process.
Dr. Pachuta says the next step is developing appropriate and routine onsite monitoring and periodic testing programs to assure a CO2 producer can effectively remove these source-based impurities from all CO2 loads destined for beverage and other food uses (dry ice for food preservation).
Uschi Mannl, a manager at Austria-based V&F Analyse- und Messtechnik GmbH, says transport and time in storage could impact the actual gas composition of beverages and no true CO2 assessment can be done. This is why V&F created the CO2Sense mass spectrometer, which can offer continuous real-time monitoring and detects inorganic and organic impurities.
“The rising demand for pure carbon dioxide and the shortage experienced during the summer months of 2018 has opened the door for new feed gas sources for carbon dioxide,” she says. “Depending on the gas source, the degree of contamination may vary, rendering the CO2 non-viable for its use in food and beverage if contamination levels are exceeding industry prescribed limits.”
The Regulatory Landscape
Many international societies of gas quality governance groups—for example, ISBT, CGA, and EIGA—have responded to the changes in CO2 source-based manufacturing and new applications that occurred the last two decades and continue to evolve.
“Associated upgrades of CO2 quality standards were primarily spearheaded and driven by several major beverage manufacturers in the late 1990s who themselves were most severely impacted by major, expensive recalls and brand name damage caused by the unrecognized use of poor quality CO2,” Dr. Pachuta says. “To date, however, food-grade purity regulating bodies have not in our opinion significantly upgraded their traditional purity specifications in response to the many new types and levels of impurities that can come from non-traditional commercial CO2 sources.”
Richard Craig, technical director at CGA, says since FSMA came into play, the facilities that manufacture CO2 for beverage or food need to do so in accordance to the Code of Federal Regulations Title 21, Part 117, which is the Good Manufacturing Practices for foods, including ingredients.
“We are a regulated industry and we take compliance with regulation very seriously,” he says.
Airborne Labs International recommends taking a second look at these medical and food-grade CO2 specification issues. For instance, liquid CO2 is a strong solvent and can leach various plasticizers from transfer hoses that feed storage tanks at restaurants and bars. The hose materials used for liquid CO2 transfers has to be carefully selected and tested for plasticizer leaching, which sometimes is not done.
“Even though filters are many times used, the quality of CO2 stored in special tanks used in most fast food restaurants and bars are not regularly checked for the slow buildup of many, potentially harmful, non-volatile impurities that can accumulate with time,” Dr. Pachuta says. “New, non-traditional, home-based personal ‘carbonated beverage’ manufacturing applications do not require the use of beverage quality-tested CO2 cartridges. This can pose a potential risk that has not been adequately studied or monitored to date.”
Retaining Quality Control
Industry insiders agree that all carbonated beverage manufacturers, including fountain operators, should become familiar with the educational guidelines available from various organizations such as the ISBT.
“We recommend that, when possible, ISBT Purity Grade CO2 be used for their carbonated beverage products. ISBT CO2 purity is higher than food-grade purity levels, but both are acceptable,” Dr. Pachuta comments. “Users of mini-bulk tanks or large storage tanks with only gas phase CO2 removal should periodically test their liquid CO2 for any slow buildup of non-volatile residues.”
Additionally, all CO2 manufacturers should routinely monitor and test their CO2 feed gas sources for any changes in composition as well as routinely monitor the quality of their CO2 throughout the in-process, cleanup, bulk storage, and truck or rail car-filling steps.
Regional CO2 storage and trans-fill depots also need to have some basic and low-cost CO2 purity monitoring systems available that can quickly catch any incoming off-quality CO2 “bad apple” loads in order to prevent any major CO2 quality upsets.
Dr. Pachuta emphasizes that ISBT-recommended onsite monitoring analyzer methods be employed for routine CO2 testing and ISO-17025 accredited gas testing laboratories be used for periodic CO2 feed gas, in-process, and final product CO2 purity testing. He also suggests that beverage manufacturers and fountain operations periodically audit the quality practices of their CO2 suppliers for consistency and require them to periodically verify their CO2 quality by an independent ISO-certified laboratory.
Beverage Industry Growth and Innovation
The beverage packaging and processing industry is experiencing major growth, according to PMMI’s “2018 Beverage Trends in Packaging and Processing” report. The North American beverage industry is expected to grow 4.5% to $45.5 billion in the next 10 years. Despite 70% of respondents believing aluminum cans and bottles are expected to see the greatest innovation in design, container, and graphics enhancements, plastic still accounts for 45% of packaging material usage. Ready-to-drink, non-alcoholic beverages (in glass containers) are expected to grow at about 40% and wine (in plastic containers) is projected to increase 100% by 2028.—FQ&S