Development and Testing of the Check-valve Spout Adapter

INTRODUCTION Several major changes in sap collection equipment and methods have occurred over the past 10-15 years. The introduction of small spouts, a transition in composition from polyvinyl chloride (PVC) tubing to polyethylene (PE) tubing, and improvements in fittings have occurred. These changes, along with continued modifications in tubing system design, installation, and maintenance as well as alterations in vacuum systems and their operation have led to significant improvements in sap yields for maple producers. The result has been a steady increase in sap yields from those producers adopting this technology and methods to the point where annual yields of 0.3-0.5 gal of syrup equivalent are not uncommon. Because sap flow reductions and stoppage is ultimately due to taphole drying, which is induced by microbial contamination of tapholes (Naghski and Willits 1955), a significant barrier to sustained high sap yields in tubing systems is related to contamination with various microorganisms. In particular, microbial biofilms develop in sap collection tubing systems as they age (King and Morselli 1983, 1985, Legacé et al. 2006). Despite several research studies and the experience of thousands of sugarmakers, no cleaning methods are clearly capable of returning tubing to the level of sanitation of a new, unused system. The maple industry has responded to this challenge most recently by introducing annually replaceable spouts or spout adapters, which provide a very clean spout-tree interface. Research has demonstrated that these adapters can provide some benefit to sugarmakers in terms of increased sap yield (Perkins, Wilmot, and Stowe unpublished), however they still do not provide an adequate barrier against the migration of microorganisms from the spout stubby, dropline, and lateral line back into the taphole. Thus the use of spout adapters, although helpful, does not completely address the problem of microbial induced taphole drying. The use of vacuum in tubing operations greatly exacerbates this problem by creating a fairly substantial negative pressure within the taphole zone. Under such circumstances, when a leak occurs, or the system is shutdown rapidly , or even when some types of releasers dump their contents by admitting air, this negative pressure in the taphole can cause sap to briefly surge backward in the tubing system towards the tree, carrying microbes into the taphole. The more this backflow of sap occurs, the higher the temperature, and the greater the number of microbes reaching the taphole, the stronger the taphole drying response will be. Eventually sap …