HOW TO CLEAN YOUR KEGS TO PRESERVE THE UNIQUE ATTRIBUTES OF YOUR BEER

Transcription

1 HOW TO CLEAN YOUR KEGS TO PRESERVE THE UNIQUE ATTRIBUTES OF YOUR BEER APRIL 2018

2 AUTHORS JOSE MANUEL PICADO GONZÁLEZ is the Manager of the Department of Innovation & New Products. He has a degree in Aeronautical Engineering and a Masters Degree in Quality Assurance and Innovation Management. He started his career at THIELMANN PORTINOX SPAIN SA in 1995 with the objective of implementing the standard ISO Since then, he has been involved in the development of innovative stainless steel containers such as those for LPG storage. His experience, academic training, and continuous learning have given him a strong understanding of materials, quality and innovation. RAQUEL S. MANZANO joined THIELMANN PORTINOX SPAIN SA in With a Degree in Industrial Engineering, she started working in the Department of Quality Management, where she has collaborated to develop and homologate different types of stainless steel containers. Her experience and methodical character led her to manage the Quality Department. Since then she has gone on to join the Department of Innovation & New Products in DR. ANGELA GARCIA-MARAVER joined THIELMANN PORTINOX SPAIN SA in 2015 to become part of the Department of Innovation & New Products. Her professional career has always been linked to R&D&I, with previous experience in the Department of Civil Engineering of the University of Granada, where she was working as a lecturer and researcher. Dr Garcia-Maraver has an International Doctorate Degree in Chemical Engineering, as well as a professional background in research and development in industry and academia. 2

3 TABLE OF CONTENTS STAINLESS STEEL KEGS AS BEER PACKAGING REGULATORY FRAMEWORK WASHING HYGIENIC DESIGN PRINCIPLES 3

4 Properly cleaned kegs are critical to the quality of draft beer. If kegs are not washed under appropriate conditions, organic and inorganic soils such as carbohydrates, proteins, mold colonies and beerstone may accumulate on the inner surfaces of the kegs and on the spears, leading to beer alteration and contamination. In order to avoid this, it is important to control the parameters involved in the washing process and choose kegs that are designed to minimize contamination of the product they contain. STAINLESS STEEL KEGS AS BEER PACKAGING In order to deliver products to consumers in perfect condition, packaging must: (i) prevent breakage (mechanical protection), spoilage (barrier to moisture, gases, light, flavors and aromas), contamination, tampering and theft; and (ii) increase shelf life 1. Selecting the right packaging design and material plays an important role in maintaining product quality and freshness during distribution and storage. In the particular case of beer, its sensitivity to oxygen, heat, age, light and pressure makes it doubly important to select packaging that will guarantee the beer maintains flavor, freshness and quality achieved in the brewery. In this regard, stainless steel kegs present two main benefits: Kegs are designed to transport beer in bulk and dispense by the glass while maintaining its quality and integrity. Their design protects beer from both air and light while enabling easy and rapid dispense. When tapped, the keg valve admits gas to the head space where it applies the pressure needed to push beer up through the spear or down tube and out of the keg through the coupler, while maintaining correct carbonation in the remaining beer 2. The inertness of stainless steel makes it ideal for food and beverage packaging due to the fact that it does not react with food, so both the product and the container remain pristine. Moreover, stainless steel is a very hygienic material, remarkably cleanable and durable. Thanks to these properties, certain grades of stainless steel have become the material of choice for the food and beverage sector, where guaranteeing the quality of the product is imperative 3. Thus, beer storage in stainless steel kegs results in better preservation given that the beer keeps its original physical, chemical and sensory properties for longer periods of time 4. As stainless steel kegs are refillable, they have to be subjected to external and internal washing processes before each use. This means that the kegs have to be resistant to washing processes with all product contact surfaces able to be effectively exposed to washing agents and rinse water without retaining or attracting microbial growth nor retaining washing agent residue

5 REGULATORY FRAMEWORK Kegs should be cleaned according to established industry methods and manufacturing practices in a safe manner. However, there is no defined typical washing for kegs 5, hence keg compatibility should be verified to provide the optimum washing sequence and maintain keg quality 6. There are some general recommendations on food contact materials and surface finishes to be applied to guarantee the hygiene and safety of beer inside kegs: In the USA, all product contact materials used in the keg system should comply with applicable FDA regulations for primary food contact. Stainless steel beer contact surfaces should be made of food safe AISI 304 or AISI 316 stainless steel 7. In Europe, all manufacturers must adopt Good Manufacturing Practice according to EC Regulation 2023/2006 for materials and articles intended to come into contact with food 8. Additionally, all product-contact materials must comply with the Framework Directive EC 1935/2004 on materials and articles intended to come into contact with food, and all product-contact surfaces must comply with Article 2 of the Food Hygiene Regulations EC 852/2004 on the hygiene of foodstuffs 9. A number of best practices have been developed by brewers associations, trade associations, brand owners, container and safety tube manufacturers, that provide recommendations or guidelines for washing keg practices. Some of the most representative associations are listed below: -Brewing, Food and Beverage Industry Suppliers Association (BFBI): -Master Brewers Association of the Americas (MBAA): -Brewers Association for Small and Independent Craft Brewers (BA): -Independent Brewers Association (IBA): 5. NOTE: It is the brewer s responsibility to be familiar with and to maintain compliance with all federal, state, and local statutes and regulations and additionally those of other countries where a brewer chooses to export

6 WASHING Although there is no specific regulation defining the washing process for kegs as beverage packaging 10, two main aspects have to be controlled to guarantee the hygiene of the keg and preserve beer quality: (i) the parameters (volumes, temperatures, velocities, chemicals ) necessary to achieve effective washing and rinsing 11 ; and (ii) the design of the keg, which has to follow certain principles to avoid the contamination of the product stored. WASHING SYSTEM DESCRIPTION Keg washing procedures vary according to valve style, keg type, and product attributes. Consequently, proper keg function requires design alignment between the keg, spear, and wash system vendors. It is recommended that keg and equipment compatibility be verified with the chemical (cleaning agent) supplier to confirm there is no negative package chemical interaction and to understand the temperatures and concentrations that allow their chemicals to perform effectively based on their beer type, water source, and cleaning system. Failure to do so may cause damage to the keg, damage to the equipment, or injury 12. External washing Kegs are washed on the outside before internal cleaning and filling 13. This first stage does not depend on the type of keg. It consists in cleaning the external areas of the keg, either manually or in a tunnel 14, and depends on the detergent used, the mechanical action implemented, the temperature and time parameters 15. (Figure 1). Figure 1A: Manual external washing H 2 O NaOH + H 2 O H 2 O Typical cleaning agents at this stage are water and sodium hydroxide high ph chemical (alkaline/caustic washing) cleaning solutions that will react with organic deposits

7 Figure 1B: Automatic external washing H 2 O NaOH + H 2 O H 2 O The mechanical action is achieved by means of brushes and normal water pressure (~2 bar), combined with hot caustic or detergent solution, followed by a final rinse. This cleaning can also be achieved manually, the main difference is that a combination of sprays and rotating brushes are used to clean the keg 16. Internal washing Despite the fact that cleaning techniques may vary according to the type of keg and the size of the keg fleet, the goal is always the same: sanitary kegs for an unaltered beer. What is key is to establish the parameters such as volume, temperature, and velocity for effective washing and rinsing. Cleaning depends on the combined effects of these parameters, and so if the velocity with which a detergent passes across a surface is increased, this may allow its concentration temperature or contact time to be reduced 17. Proper keg internal washing is conducted by making sure the wash medium comes in contact with the entire internal surface of the keg and its fittings: valves, gaskets, spear/lid. The first stage is a PRESSURE CHECK AND AIR ASSISTED PURGING OF ULLAGES. This first step is crucial in order to: (i) check that the keg is pressurized when received (and thus has not been tampered with); (ii) remove any residual beer and CO 2 and/or N 2 from inside the keg (Figure 2); and (iii) depressurize the keg so it can be manipulated in a safe manner (Figure 3). FIGURE 2. Purging of ullages Optimizing the CO 2 blowout, which can be carried out using a coupler or the pressure relief valve, will help to lower the chemical costs of the later washing steps and improve sustainability. Residual beer + Propellant gas PRESSURIZED AIR

8 FIGURE 3. Depressurization DEPRESSURIZATION DEPRESSURIZATION DEPRESSURIZATION DEPRESSURIZATION Sankey Kegs Corny Kegs Starting Kegs This is due to the fact that the caustic agents (NaOH) that will be used react with CO 2 resulting in sodium bicarbonate (NaHCO 3 ), which foams and makes the cleaning solution hard to rinse 18,19 : 2NaOH + CO 2 à Na 2 CO 3 + H 2 O Na 2 CO 3 + H 2 O + CO 2 à NaHCO 3 Note that this purging is crucial to ensure that there is no pressure inside the keg and that it can be manipulated without risk. Following purging, the inside of the keg can be accessed in different ways, depending on brewery facilities: - Small-breweries without industrial washing lines or keg washers have two options to access the interior surface of the kegs: A) Remove the spear (in the case of Sankey kegs), the lid (in the case of Corny kegs) or both (in the case of Starting kegs) together with all the fittings in order to have access to the inside of the kegs and fully submerge the fittings in a cleaning solution 20. In this case, since the spear/ valve system requires decoupling for interior surface inspection and washing, it is important that the brewer only use the authorized decoupling device 21. This step has to be carried out with no pressure inside the keg, so purging beforehand is critical. B) Use a coupler to force the cleaning agents inside the keg through the spear and/or valves. In this case the wash medium is forced up the inside of the spear tube under pressure and cascades over the outer surface of the valve spear tube and down the internal walls of the keg 22. The sump (dimple) forces the product from the keg during drainage. Dimensional tolerances of the keg design with valve and spear assembly are critical for a complete and effective keg wash. The end of the spear tube should be in the sump, but not so close to the bottom dome as to restrict the flow of rinse water and detergents

9 - Breweries with larger keg fleets have more keg washing options depending on the number of kegs per hour to wash and the degree of automation desired, which can range from manual rinsing machines to fully-automatic washing and filling lines. Once the access to the inside of the keg is achieved, there is a common basic washing process sequence used in breweries worldwide as described below 24,25. It should also be noted that when the internal washing is carried out with assembled kegs, they are always washed upside down. I) WARM WATER PRE-RINSE (Figure 4) using water ranging in temperature from ambient temperature to 50ºC (122ºF) rinse out any remaining residual product on the inner walls of the kegs and the spear (if assembled). This dissolves any collapsed foam and rinses away any residual beer 26. It is then recommended to PURGE the keg with air in order to remove the rinse water and any remaining residual product. FIGURE 4A. PRE-RINSE FIGURE 4B. PURGE Residual product Water Water Air II) HOT ALKALINE WASHING (Figure 5) using water ranging in temperature from 50ºC to 70ºC (122 to 160ºF), to loosen, breakdown and remove proteinaceous materials from the keg walls, the inside and outside of the valve system. Caustic cleaners work best at higher temperatures, although temperatures over 80ºC (175 F) can cause precipitation of soils that then become more difficult to remove

10 The most commonly used alkaline liquid cleaning solutions are comprised of sodium and/ or potassium hydroxide (NaOH and KOH), with extremely high (12-14) ph to hydrolyze (break down) and remove soil. While there are powdered non-caustic alkaline cleaners with lower ph levels that are safer, caustic cleaning solutions are used in breweries because they are relatively inexpensive and recyclable (reusable), and they are effective at removing protein-based soils 28. FIGURE 5A. ALCALINE WASH (Spraying method) FIGURE 5B. ALCALINE WASH (Soaking method) FIGURE 5C. RINSE NaOH solution NaOH solution NaOH solution Residual product Water If the brewery does not have a keg washer to spray and/or soak the washing agents, this step can be effectively carried out by pouring the mixture in to the keg and filling it to full to ensure that the entire interior is cleaned, making sure that the lid, gasket, and valves are completely submerged (if assembled). Then, turn over the keg, shake it, or roll it back and forth 29. This soaking is especially effective in kegs with organic materials difficult to remove, i.e. where kegs have been air dispensed with picnic pumps and the residual product has oxidized and/or mold colonies have formed, or in unfiltered beers with high yeast loading. In these cases, soaking the kegs overnight with 2% v/v caustic solution might be practical 30. Improper concentration of chemicals is one of the most common mistakes in keg washing. If solutions are too weak, the cleaning is not effective; if solutions are too strong, the rinse ability decreases 31. In order to check the correct concentration the chemical salesperson should provide a titration kit to use if you lack a lab equipped for this. Using ph papers will not help determine the proper use concentration, because ph and concentration are two distinct measurements

11 Once the caustic washing step is finished, THE DETERGENT IS DRAINED AND THE CAUSTIC SOLUTION IS RECOVERED. This solution can be recovered to a holding tank where it is reheated, titration monitored and adjusted. It is recommended to PURGE the keg with air in order to remove any remaining residual product. Once the keg is purged, it has to be RINSED WITH HOT WATER ranging in temperature from 50ºC to 70ºC (122 to 160ºF) to be properly effective 32. This stage may be repeated to ensure that the keg is free of caustic. III) ACID WASH (Figure 6) to neutralize the caustic and to prevent calcium precipitants and beer stone from building up on inner surfaces. Depending on the product and water hardness at the facility, a phosphoric acid wash (0.2 to 0.4% v/v at 50º to 70ºC (122 to 158ºF)) may be used after the caustic wash. This step does not have to be carried out after every use of the keg, but should be considered periodically 33 since caustic cleaning solutions do not address calcium and magnesium hard water scale deposits anywhere near as well as acidic cleaning solutions. Acids blends, often containing phosphoric and nitric acid, are commonly used in the brewery to remove beerstone deposits 34, passivate metal (stainless steel), and neutralize caustic cleaners. Unlike alkaline cleaners, however, acids by themselves are not usually very good at removing protein-based soils 35. FIGURE 6A. ACID WASH (Spraying method) FIGURE 6B. ACID WASH (Soaking method) FIGURE 6C. RINSE Acid solution Acid solution Residual product Acid solution Water

12 Beerstone is calcium oxalate (C 2 CaO 4 ), a mineral deposit that forms slowly on a surface that is exposed to beer and is very difficult to remove. If not removed, it will leave an unsanitary surface that can harbor microorganisms and biofilms. It can also give the beer an off taste 36. This particularly occurs in kegs holding unfiltered beer, where yeast deposits may occur. Non-caustic cleaners tend to cost more per pound than caustics do and cannot be normally recycled, but they do not promote beerstone formation as much as caustics. Once the acid washing step is finished, THE ACID SOLUTION IS DRAINED AND CAN BE RECOVERED. Once the keg is purged, it has to be RINSED WITH HOT WATER. This stage may be repeated to ensure that the keg is free of acid. This water is commonly recovered to a holding tank where it is then used as the pre-rinse for the next keg to be washed. It is recommended to PURGE the keg with air in order to remove any remaining residual product. IV) SANITIZATION with steam or chemicals (Figure 7). Some systems use dry saturated steam 37 for sanitizing and some are unable to accommodate it. Those that do not use steam should have some kind of chemical sanitizing setup, such as peracetic acid, because hot water is inadequate to the task 38. Remaining sanitizer FIGURE 7. STEAM / CHEMICAL SANITIZATION Steam / Chemical sanitizer

13 The purpose of sanitizing a keg is to make sure that all surfaces which will later be in contact with beer come in contact with the sanitizer for an appropriate amount of time to let the sanitizer do its job. Regardless of the sanitizer used, this stage consists of: (i) pressurizing the keg full of sanitizer to 10+ psi (if using steam bar (20-32psig), to achieve a minimum sterilizing temperature of ºC ( ºF)); (ii) shaking the keg to make sure that all inner surfaces come in contact with the sanitizer; (iii) maintaining the keg at sterilizing temperature for the required amount of time to achieve complete sterilization of the inner surfaces and valve components; and (iv) placing the tap on the keg and flushing the remaining sanitizer out until the keg is empty. Before filling, the keg should be purged with CO 2 and pressurized. CO 2 is used to drive out any sanitizer and condensate and to reduce the level of dissolved oxygen at the end of the cleaning process. CO 2 remains in the keg when the cleaning process is completed (the keg is pressurized to about 1 bar). After filling, it is recommended to spray alcohol on the top surface of the spear and then cover it with a lid, or to spray the alcohol before using the dispensing coupler at the consumption point. HYGIENIC DESIGN PRINCIPLES The design demands on equipment intended to process or store foods and beverages are stringent 39. Special attention has to be paid to roughness, welding, bend radius and external design. The inside and outside surfaces of kegs and spears must be smooth and free of defects or imperfections that may harbor microbes, inhibit thorough washing, or affect filling and dispensing, including but not limited to: cracks, crevices, pinholes, oxidized (sugared) material, and / or irregular weld ripples 40. Roughness There is a relationship between the roughness of a food-contact surface and the ease with which foods will adhere to it (and also the difficulty of their removal). As a result, a surface which will remain smooth for a long period of time will resist the accumulation of bio-films that can present a hygiene hazard 41. When determining smoothness, it is the roughness that counts: the lower the surface roughness, the better the material is suited to use in environments where hygiene is top priority 42. DIN (Means of packaging:

14 Cylindrical beverage containers) establishes that the roughness (Ra) of the inner surfaces of containers should not exceed 1.6 μm after the final treatment 43. This is also the recommended value by brewers associations such as BA 44. Welding In order to guarantee that there are no heterogeneities on the inner surface of the container where food or drink residue may accumulate, it is important to control the welding techniques and processes. A dead area can be created if the joint itself protrudes inside the container. A lap joint at a weld will create a step between two surfaces. This can retain food which will remain there and deteriorate until it is removed by the cleaning processes. A butt joint, ground smooth after welding, is far superior because it will not allow the accumulation of process soils and its smoother surface is easier to clean. It must, of course, be continuous along the length of the joint 45. In a butt weld the edges of two components are brought together and a weld is laid down such that the weld material penetrates the full thickness of the joint. Examples of butt welds include: (i) the central circumferential weld joining the deep-drawn halves of a two-part container; (ii) the longitudinal weld of the cylindrical shell and the welds between the bottoms and the cylindrical shell of a three-part container; and (iii) the weld which joins the ends of a strip of material to create a tubular chime 46 : - The maximum permissible step between surfaces exposed to beer at any point along the weld run should be 0.4 mm or 25% of the gauge of the components at the point of contact (the thinner in the case of materials of two different gauges), whichever is the lesser. - The weld should penetrate for at least the full depth of the original area of contact of the two component parts at all points along the weld run. Over penetration on the side in contact with beer should be no more than the value defined for misalignment. Inside radius The inside of a stainless steel beer keg is a food zone so, according to the previous points, the surface has to be smooth and easy to clean, and it cannot have any deep or sharp crevices which could harbor bacteria or other organisms 47. Tight bends can trap foods. The larger the radius of a bend the more freely the product will flow and the less hygiene risk there will be. The same applies to the corners of vessels in which product may be stored the larger the radius of the corners, the easier they are to clean. The European Hygienic Engineering & Design Group (EHEDG) recommends that corners of closed equipment (where access for cleaning can be very difficult) have a minimum radius of 3 mm and that minimum slope of the bottom of a tank is 3 from the horizontal

15 External design Keg chimes (skirts) are designed to protect the keg from external contamination. A tank resting on a concrete base will create just such a crevice. Grouting this crevice may initially seal it, but grout can shrink and crack with time, eventually creating crevices that can lead to corrosion. Raising the tank off the floor by mounting it on legs eliminates the crevice 49. This is one of reasons for keg chimes, which consist of skirts all the way round to protect the crevice between the tank and the floor from external agents. Drain holes will be required as agreed between manufacturer and customer. Drain holes between top/bottom skirt and body need to be specified and of an agreed design 50. The bottom rings have draining holes in their upper part in order to ensure that substances accumulated inside the chimes when the keg is upside down are drained. In addition, given that the bottom parts of the skirts (to be in direct contact with the floor) are curled, there are small holes in the curls to drain the substances that may accumulate inside them

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