During the 2019 maple season the Cornell Maple Program conducted replicated trials on 5/16Ó and 3/16Ó tubing looking at a variety of tubing options for taphole sanitation and tapping. This report will focus on the 5/16Ó results.
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In a normal sap flow event, trees exude sap during the above freezing period and replenish that lost water by ÒsuckingÓ it up from the roots during the below freezing period. If on a tubing system, during this negative pressure period they tend to draw sap back into the tree from the dropline. Sap, once it enters the droplines, is quickly contaminated with microbes. When they are drawn back into the tree, tap hole closure is initiated. The problem is compounded in 3/16- inch tubing because, unlike 5/16-inch tubing, the smaller diameter collection tube remains full of sap. A Cornell study found that up to 12 feet of sap in a 3/16-inch tube can be drawn back into the tree during this recharge time. CV spouts are one proven method of limiting this drawback with 5/16 inch tubing. The question was: will they also be effective with 3/16-inch tubing that is full of sap?
There has been a lot of interest in 3/16″ tubing over the past several years. This article describes research results and possible future directions.
The sugar concentrations and the volume yields of Acer saccharum Marsh. sap from trees with single tapholes both show large variations from year to year and during sap flow seasons. Daily measurements of sugar concentration and volume yield from 29 trees for 18 years show consistent patterns. High sugar concentrations and high volume yields are characteristic of some trees; lower sugar concentrations and smaller volume yields are characteristic of other trees. A regression analysis shows a highly significant relationship between sugar concentration and volume yield in individual trees.
A cost analysis of processing maple sap to syrup for three fuel types, oil-, wood-, and LP gas-fired evaporators, indicates that: (1) fuel, capital, and labor are the major cost components of processing sap to syrup; (2) woodfired evaporators show a slight cost advantage over oil- and LP gas-fired evaporators; however, as the cost of wood approaches $50 per cord, wood as a fuel would no longer have this cost advantage; (3) economies of scale exist in processing maple sap to syrup; (4) in 1977 the total cost of production, including both sap production costs and processing costs, for a medium-size (750) gallons of syrup) operation was $8.36 per gallon of syrup for oil-fired evaporators, $7.97 per gallon of syrup for wood-fired evaporators, and $8.37 per gallon for LP gas-fired evaporators.
More then a decade ago there was a renewed realization that microbial contamination of maple sap collection systems was having a significant detrimental impact on sap yields. Several research studies to investigate ways to improve sap yields from tubing systems were undertaken at both the University of Vermont Proctor Maple Research Center (Underhill, VT) and at the Cornell University Arnot Forest (Van Etten, NY) starting at about the same time and proceeded both as independent and joint projects from 2009-2018. The results of many of these studies have been reported in the past in numerous individual publications and presentations. This article seeks to combine and present this extensive body of work into a single, comprehensive, but concise summary of our results.
A simple colorimetric test detects off-flavour profiles ofmaple syrups inminutes, which are detectable by the naked eye. As flavour profiles are due to complex mixtures of molecules, the test uses nonspecific interactions for analysing the aggregation and color change of Au nanoparticles (AuNPs) induced by the different organic molecules contained in off-flavour maple syrup. The test was optimal with 13 nm citrate-capped AuNPs reacting 1 : 1 with pure maple syrup diluted 10 times. Under these conditions, normal flavour maple syrups did not react and the solution remained red, while off-flavoured maple syrups aggregated the AuNPs and the solution turned blue. Different classes of molecules were then tested to evaluate the types of compounds typically found in maple syrups reacting in the test, showing that sulfur- and amine-containing amino acids and aromatic amines caused aggregation of the AuNPs. The test was validated with 1818 maple syrup samples from the 2018 harvest in Quebec and 98% of the off-flavoured maple syrups were positively identified against the standard taste test. Preliminary tests were performed on site in maple sugar shacks to validate the applicability of the test on the production site.
The current ‘traditional’ tap hole number guidelines involve adding a tap for each 5 inch dbh above 10 inches dbh. ‘Conservative’ guidelines involve placing one tap in trees 12 inch dbh and a second tap in trees more than 18 inches dbh. The reasons behind the traditional guidelines are not stated in the North American Maple Syrup Producers Manual, but the conservative guidelines are suggested when there is concern for tree health. The purpose of this article is discover where these guidelines came from and to re-establish the reasons why they exist.
Sap exudation refers to the process whereby sugar maple trees (Acer saccharum) are capable of generating significant stem pressure in a leafless state, something that occurs to a lesser extent in only a few other related species such as birch and walnut. This exudation pressure is what causes maple sap to flow from a taphole in sufficient quantities to be harvested and processed into syrup. Exudation has been studied for well over 100 years and has been the subject of many scientific studies, but there is as yet no definitive explanation for how such large pressures can be generated in the absence of transpiration (i.e., when no photosynthesis occurs to drive the flow of sap).
A model that calculates the proportions of conductive and nonconductive wood in the tapping zone of a tree over time given user-input values for tree diameter and tapping practices.