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FINAL DRAFT GUIDELINES FOR THE USE OF AIR INJECTION IN MAPLE SYRUP PRODUCTION Prepared on behalf of the International Maple Syrup Institute July 2011 BACKGROUND The use of air injection technology in the
FINAL DRAFT GUIDELINES FOR THE USE OF AIR INJECTION IN MAPLE SYRUP PRODUCTION Prepared on behalf of the International Maple Syrup Institute July 2011 BACKGROUND The use of air injection technology in the maple industry is the forced introduction of air through a series of perforated pipes submerged in the boiling sap in the front and/or back pan of a maple syrup evaporator. Air injection was introduced into the maple industry on a commercial level around the year 2000, becoming popular for its ability to produce lighter-coloured maple syrup. Operational evidence from maple syrup producers of other benefits, such as the reduction or elimination of the use of defoamer and decreased nitre accumulation in the pans, is also noteworthy. Several research and observational studies have been conducted in recent years, investigating the use of air injection technology. No single study can replicate the wide range of conditions possible, so results have been somewhat variable. One thing that both research and operational observations have demonstrated is that a larger proportion of lighter-coloured maple syrup is produced with the use of air injection. In 2009, Centre Acer and UVM Proctor Maple Research Center reviewed research findings relevant to the use of air injection technology for the International Maple Syrup Institute (IMSI). The report concluded that, based on research evidence, maple syrup produced using air injection has physical and chemical properties within the documented norms for pure maple syrup. It is essential, however, that air injection system components be suitable for food use and that proper operational practices be followed, otherwise the potential for contamination exists. Based on the findings and conclusions of the joint report, the IMSI s Board of Directors has endorsed the use of air injection technology for the production of maple syrup, provided the equipment meets current industry standards and proper operation methods are utilized. The IMSI agreed to facilitate development of guidelines for the proper use of air injection technology as none were currently available. IMPLICATIONS OF USE Colour of Maple Syrup Research conducted in Canada and the United States has indicated that maple syrup produced with air injection is generally lighter in colour, particularly early-to-mid season. Maple producers using air injection have also found the maple syrup to be generally lighter in colour. Darker syrups are still made later in the season but may be slightly lighter in colour than they would be otherwise. Based on available research and operational evidence, there is no difference in the stability of the colour in storage over time of maple syrup made with or without air injection. Flavour of Maple Syrup Research at UVM Proctor and Centre Acer has found lower levels of flavour compounds in maple syrup made with air injection when compared to maple syrup made from the same sap without air injection. This is consistent with maple syrup that is made with air injection being generally lighter in colour and expectations that lighter coloured syrups will have milder flavours than darker coloured syrups. There has been some implication of off-flavours being more prevalent but this has been inconsistent and may be related to improper use of the technology or the fact that off-flavours may be more noticeable in lighter-coloured syrup. Maple syrup flavour should always be monitored for quality and appropriateness for colour class, especially when introducing any new technique or equipment into an operation. Effects on Maple Syrup Chemistry The chemistry of maple syrup made with air injection appears to be within the normal range for maple syrup in terms of the parameters evaluated by Centre Acer and UVM Proctor. There could possibly be some change in ph, invert sugars, and other aspects of maple syrup chemistry. Preliminary research has been conducted on a laboratory scale but further study is required before any definite conclusions can be drawn related to the effect of air injection on maple syrup chemistry. Defoamer Use Research studies have not documented any difference in the amount of defoamer required with the use of air injection. Despite this, there are indications from producers in both Canada and the United States that the requirement for defoamer can be reduced, or eliminated entirely in some operations, with the proper use of an air injection system. Some maple producers using air injection have observed that foaming is effectively controlled by the system and if the blowers are shut off at a full boil, the syrup will quickly foam up and over the sides of the pan. Effect on Boiling Process and Nitre Build-Up Research found no difference in the boiling process in terms of sugar sand production or nitre (scale) accumulation on pan surfaces. Research also documented nitre accumulation to be lighter in colour but of the same thickness. However, many producers using air injection have found their pans to be easier to clean and requiring less frequent cleaning. Some maple producers report about a third more syrup can be boiled before changing pans because of reduced nitre build up. Some producers have also found an air injection system to move a large portion of the foamy residue that is formed in the boiling process through the system and out into the filter tank rather than allowing it to remain in and clinging to the sides of the pans. Research has found liquid temperatures to be reduced an average of 7.7 C in evaporator pans with air injection, resulting in a slight reduction in the evaporation rate. Reports from maple producers on the effect of air injection on evaporation rate have been varied. Some producers report no noticeable difference or a slight decrease in evaporation rate while others find evaporation rate to be increased. These differences could be attributable to variations in installation. Producers have observed the steam, particularly in the hood of a flue pan, to be much more intense when an air injection system is operating. Organic Certification Organic certification in the United States permits the use of air injection for maple syrup production but it is currently prohibited by Canadian organic standards. Canadian and Quebec authorities who oversee the organic standards made their decision in 2005 after recommendations from Joel Boutin based on a study he conducted in 2004 that indicated basic properties of maple syrup (chemistry, flavour, and colour) are altered with the use of air injection. More research and gathering of information is necessary to compare maple syrup produced with air injection in a variety of operational settings with that which is produced without air injection to determine if there are significant differences in these attributes when the technology is applied in the field. Discussion of Risk Concern has been expressed that it may be difficult to ensure that producers are taking appropriate precautions to be certain the air that is pumped into the sap is free of odours and contaminants. Appropriate location of air intake and use of filters will prevent contamination, but care does have to be taken, as with any new equipment, to install the system properly to eliminate food safety and quality problems. ***Materials used for air injection systems should be approved for food use and equipment manufacturing guidelines for the maple industry should be followed to ensure safety and quality of the maple syrup.*** CHOOSING AND INSTALLING AN AIR INJECTION SYSTEM An air injection system must be designed and operated properly to function effectively. The wide range in design and application of air injection systems has produced varied results. Some producers have fabricated their own air injection system without sufficient regard to using only materials recommended for food use and ensuring that the quality of syrup is not adversely affected. Advice should be obtained from maple industry specialists and producers experienced in the proper use of the technology when choosing and installing a system. Air injection systems consist of a blower to provide the forced air, filters to make sure the air is clean, air pipes to transfer the air to the evaporator pans, and submerged stainless steel pipes with holes to release the air into the pans. The size of air holes and piping, distance between pipes, and other aspects of construction may vary from one effective air injection system to another. A number of effective installations are possible but it is not known what range of designs will work. Because of this, the following description refers to one configuration that has been found to work well in practice. Blower The blowers used for air injection systems are generally electric bypass motors and are low wattage. Any variety of air distribution motors could be used to pump the air into an air injection system. Depending on the size of blower and the sizes of the pans, one blower unit may be required for each pan that has air injection. For example, an evaporator that is 3 x 12 may require one unit to accommodate the complete evaporator but a 6 x 16 would probably require two units. Air Filters Dust and activated carbon air filters need to be installed as part of the blower unit to filter the air entering the system to prevent contamination. Dust filters are designed to prevent dust and other floating debris from entering the system and the activated carbon filter is to help remove any odours and tastes. There are different efficiencies of both types of filters. Even high efficiency filters will not filter out 100% of contaminants so anything that creates dust or fumes (e.g. paints, fuels, cigarette smoke) should not be permitted in the production area or area of air intake. When choosing a dust filter, avoid household or lower quality air filters. Flat furnace style filters can have an efficiency rating as low as 10%. Better quality industrial air filters are generally rated as MERV 6-14, translating into various efficiencies. A MERV 7-8 would be suitable for an air injection system. A good filter should have a minimum of 15 pleats per foot. Filters for taste and odour removal are generally made of activated carbon. Lower priced and less efficient filters are often made of plain carbon (charcoal). It is good practice to install the filters in series with a dust filter on either side of the carbon filter, in order from ambient air to blower: 1. Dust (particulate) filter for large debris 2. Good quality activated carbon filter 3. Premium quality safety trap filter to capture any escaping activated carbon 4. Blower Filters should be installed securely and checked regularly to ensure that they are clean, in place, not loose in their frame, and functioning properly. Filters should be replaced each season or earlier if evidence of heavy deposits is found. Activated carbon filters in particular have a relatively short service life of about 6 months. They continue to absorb contaminants from the air, even in storage, making them less efficient. Activated carbon is also a good bacteria growth media so it is important to change the filters each season, regardless of appearance and odour. Maple producers are advised to consult with filtration specialists regarding the most appropriate filters to utilize for their air injection system, including cleaning procedures and frequency of cleaning. Placement of Air Intake Air intake should be in a clean, dry place free of dust, mould, odours, or other contaminants. It should not be outside in prevailing winds from barn smells, oil tanks, or exhaust. It should also be kept out of dusty areas such as wood sheds and areas in the sugarhouse prone to steam and mould such as lofts and attics. The air intake should not be located in an area where livestock are housed, milked, or fed. A pump room (if the pump is ventilated outside if necessary) or tank room are often good locations. Noise can be an issue, so if possible the blower should be in a separate room or a good location outside under an eave to minimize noise in the work area. The blower unit should be installed within 50 feet of the evaporator to maintain effective air transfer. Air Transfer Pipes from Blower to Evaporator Pans 1 ½ stainless steel piping works well for the air transfer pipes from the blower to the evaporator. Potable PVC piping is sometimes used but should be avoided, particularly within 10 feet of the evaporator, because steam from the boiling evaporator can cause unacceptable heating and sagging of the pipes if the blower is not turned on or the power source fails. All air transfer pipes should be slightly sloped (at least 1%) to the evaporator to prevent low spots where condensation may collect. Pooling of condensation within the pipe or at the blower could cause problems by providing a potential for contamination or interfering with the functioning of the blower. Submerged Air Pipes ½ stainless steel piping works well for the submerged pipes in the flue and flat pans. The holes should be on the under side of the pipes, approximately 5/64 in diameter and spaced about 2 apart along the full length of the pipes. The 1 ½ air supply pipe should be situated to allow even distribution of air to each section of pan. The ½ submerged air pipes should be secured together to maintain even spacing and provide support. This can be achieved by installing support bars consisting of lengths of ¼ square stainless steel welded across the pipes of each pan section at appropriate intervals. Depending on the length of the pipes, this could be every four feet or close to each end of the section. Flat Syrup Pans The ½ submerged air pipes should be approximately 2 apart, and extend the full length of the pan. The only exception is in the section of pan with the draw off, where the air pipes should end up to 24 short of the draw off so as not to interfere with temperature readings. There should be short stainless steel legs on the pipes to raise them about ½ up off the bottom of the pan to allow space between the air holes and the pan. Flue Pans In the flue pans, the ½ submerged air pipes should run directly above each and every drop flue. The support bars, securing the pipes together, can rest across the flues. The air is forced out from the holes in the bottom of the pipes towards the bottom of the cavity of the drop flues before rapidly rising back up to the surface, resulting in essentially double action from the air bubbles. A variation in some air injection systems consists of the submerged air pipes running along the bottom of each drop flue, possibly with varying results. Additional Considerations There is no information available regarding the appropriate amount of air required for optimal functioning of an air injection system. Many systems have been found to produce relatively lightercoloured maple syrup. However, a system would ideally be set up to provide just enough air to control foaming without the use of defoamer and move any foamy residue through the system. Trial and error will be necessary with each unit to determine the appropriate amount of air required to be effective. The amount of air can be regulated by size of blower, speed control on the blower or valves in the air transfer pipes. Valves may be installed in the 1 ½ air supply pipes for each pan but care should be taken not to restrict air from the blower to the extent that the blower will burn out. The valves may be particularly useful for regulating the amount of air to each pan when one blower is servicing more than one pan. All fittings should be secure. If the air supply pipe pulls apart, air would not get to the pan and a boil over could occur. MAINTENANCE AND CLEANING Any equipment used in the production of a food product, including maple syrup, must be regularly and effectively maintained and cleaned in order to provide a consistently safe and high quality product. Any damaged or defective equipment should be promptly repaired or replaced. The frequency of cleaning will vary depending on the amount of syrup that has been boiled and will change throughout the season. The nitre should be cleaned off the submerged air pipes whenever the pans are cleaned. It is imperative that the utmost care is taken to clean in a manner that will not cause or increase the likelihood of contamination to the maple syrup. Cleaning and Maintenance of Air Injection System It is important to remove nitre from the submerged pipes in the evaporator pans in addition to cleaning the nitre from the pans themselves. It is beneficial if submerged pipes can be easily removed for maintenance and cleaning. The entire unit of pipes in a pan is not heavy but can be awkward to get out easily unless installed as distict sections. Each pan division should have a separate section of air injection pipes that can be connected to the air supply with clamps for easy removal. The ends of the submerged ½ air pipes may be crimped and/or welded but can also be equipped with removable stainless steel plugs at the ends to allow access for cleaning. The air holes will need cleaning periodically as they will clog with nitre, particularly in the flat (syrup) pan. This can be monitored by observing bubbling with the unit on and the evaporator shut off as well as visual inspections to see if the holes are getting clogged. To clean the pipes and unclog holes, the pipes need to be removed from the pan. A scraper, utility tool with a crescent shaped side, or a scrub brush can be used to scrape off nitre. Any holes still clogged can be cleaned out with a drill and bit of the same size as the holes. If an acid wash is being used to clean the pans, it would also completely clean the air injection pipes, including the holes. When cleaning with acid, the air injection system should be working with the air on full flow, enhancing the washing effect with the turbulence. Using the Air Injection System as a Cleaning Aid The air injection system can also be utilized when cleaning the finishing pan. A technique that works well for cleaning the finishing pan when shut down at the end of the day is to: fill the pan with water (RO water if available) turn on the air injection bring the water in the finishing pan to a boil shut off the heat but leave the air injection system on for a couple of hours let the water sit in the pan overnight and then drain in the morning The pan may then just need rinsing or minimal rubbing, depending on how much nitre was initially on the pan. This same technique can be used for cleaning during a day of boiling if the pan requires cleaning but can not be easily replaced with a clean one. Because of time constraints, the process can be sped up by keeping the RO water boiling with the air injection on for a half hour then letting it sit for another half hour with the air injection running before draining, rinsing and doing any scrubbing necessary. Overall, most producers agree that less time is spent cleaning when an air injection system is used in their operation. FUTURE CONSIDERATIONS These guidelines are to provide the basic information to maple producers about air injection systems and their use in maple syrup production. Further research and experimentation would be beneficial to increasing the information available on optimal configurations for air injection systems and any possible implications of use. Sizing of pipes and air holes, spacing of pipes and air holes, amounts of air, and other design characteristics vary from one installation to another. Further information on all aspects of air injection use would help producers to make more informed decisions regarding whether or not they should install a system and how one should be installed to accomplish their objectives. All materials and methods used in an air injection system should be recommended for food use and the equipment should be maintained and cleaned appropriately. Flavour
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