PRODUCTION AND PROPERTIES OF BIRCH SYRUP (Betula populifolia) R. Kok1, E.R. Norris1, and T. Beveridge2 1Department of Agricultural Engineering, and 2SchoolofFood Science. Macdonald College of McGillUniversity, Ste. Annede Bellevue, Quebec HOA ICO Received 30 November 1976 Kok, R., E.R. Norris, and T. Beveridge. 1978. Production and properties of birchsyrup(Betulapopulifolia). Can. Agric. Eng. 20: 5-9. Sixteen grey birch trees ( B. populifolia) were tapped during 1975; fifty were tapped during 1976. Sapwas collected daily and boiled to a syrup. Thesugar content as well as the volume of thesapproduced byeachtreewas measured every dayduring the 1976 season. Theaverage seasonal sap production during 1975 was 42.8 //tree;during 1976 it was 27.9 //tree.Theaverage sap sugarcontent during 1976 was 0.74% (w/v). Trees tapped suffered noapparentilleffects from thetapping. Average syrup/;Hwas 4.8. The average syrup (50% byweight sugar) viscosity was 15 centipoise. Thesyrup ash content increased during the tapping season from 1.22 to 3.3%. Thedominant wavelength ofthesyrup color was 580 nm; itsexcitation purity was 0.671. The syrup was judged as being acceptable by 59%, of an 82-member taste panel. INTRODUCTION birch), B. papyri/era (white birch) and B. combined and kept for boiling. alleghaniensis (yellow birch) (Marie- The solids content of the daily individual Although maple products and their Victorin 1964; Hosie 1969). For this study, characteristic flavor are today well known, tree sap samples was determined by the grey birch was chosen, since it was similar products obtainable from birch, pipetting 10 ml of sap into a drying dish, abundantly available in the immediate walnut, hickory, ash, basswood and leaving the dish in a drying oven at 75°C for vicinity. The grey birch is characteristically butternut trees (Nearing 1950), once 24 h and weighing. This method of solids one of the first species to reappear after produced in quantity, are all but forgotten; content determination was found to yield forest destruction and often occurs in dense syrup, butter and taffy can be manufactured solid contents within 0.02% (w/v) when stands. Grey birch might therefore not only from the saps of these trees as well as from tested with sucrose solutions over the range be considered as a sugar-producing plant maple sap. The winning of maple sap and its 0.25 - 1.25 % (w/ v). Sucrose has been found but simultaneously as a principal processing have been adequately described to be the major dissolved solid of maple component of an energy plantation wherein in the literature (Nearing 1950; Perrin 1972; syrup (Nearing 1950). sugar could be produced as a secondary Anonymous 1973). In the spring of 1975, the birch sap was product. The Canadian per capita annual concentrated to syrup by boiling in an consumption of maple sugar fell from 1.1 electrically-heated, deep-fat fryer (Torcan to 0.09 kg person between 1947 and 1971 SAP COLLECTION AND PROCESSING Model 210) equipped with a float-operated (Hassan 1973). Canada's annual export Methods automatic shut-off switch. Unconcentrated value of maple products rose from 4.3 to 6.4 Grey birch trees were tapped during the sap was added manually every time the million dollars between 1949 and 1968 spring of 1975 and 1976 in the Morgan liquid level decrease caused the heating (Daviault 1975); thereafter the annual Arboretum of McGill University. During element power to be switched off until 1 /of export value has remained almost constant the 1975 season, 16 trees were tapped on 17 approximately 50% (w/v) sugar was present at 6.5 million dollars during the period 1969 March. Trees of circumference greater than in the boiler. The syrup sugar concentration - 1974(Bolton 1974, 1975). Canadian maple 45 cm at 150 cm height above the ground was monitored with a refractometer (Pocket sugar production, consumption and export were randomly selected. During the 1976 Refractometer, Bellingham and Stanly Ltd., volumes have steadily declined since 1949. season, 50 trees of circumference greater London, U.K.) whose readings were The price of maple sugar has steadily risen than 42 cm were randomly selected and converted to the equivalent of % (w/v) since 1949. tapped on 8 April. In 1976 the trees were sucrose by means of a calibration curve. The Low utilization of equipment (2 or 3 tapped considerably later than in 1975, since electric boiler was found to produce a birch wk, yr) caused by the seasonal nature of sap flow in 1975 started only on 14 April. syrup with a slightly scorched flavor maple sugar production is partly responsible Tap holes 12 mm in diam and 57 mm deep although it imparted no such flavor to maple for the high cost of maple products. To were drilled in each tree trunk 90 cm above syrup during a pre-production test. increase the period of equipment use would the ground level. Tap holes were drilled at a To lower the boiling surface temperature require trees yielding sugar-bearing sap at a slight angle facing downward. Spiles were and yet retain a high rate of heat input, a time other than the productive season of inserted by moderate hammering until a steam-heated boiler was constructed for sap maple trees. This condition is fulfilled by tight fit between the spile and tap hole and boiling during the 1976 season (Fig. 1). The birch trees which start their sap flow during the tree bark was obtained. boiler was completely constructed of 316 the final stage of the maple sugar season. During both the 1975 and the 1976 stainless steel. It was subdivided by The large scale production of birch sap seasons, the sap was collected daily when partitions into five sections, each containing iiom Betual pendula Roth, B. platyphylla possible (on several occasions seasonal a steam coil of '/2-inch diam tubing, 75 cm Sukacv and B. clahurica Pall has been snowstorms prevented collection) at 1400 h. long. The five steam coils were connected in reported by Kalinishenko (1974); 28,000 Daily sap flows were recorded for series by bulkhead unions. Incoming steam tons oV birch sap were produced in the spring individual trees. was saturated and was regulated to remain of 1972 in the Ukraine. The sugar During the 1975 season, the sap of all at 1.7 kPa, thus limiting the maximum concentrations of B. pendula Roth, B. trees were combined and kept for possible surface temperature to 131°C. platyphylla and B. clahurica Pall saps in the subsequent boiling and syrup production. Unconcentrated sap was continuously fed middle of the sap-production season in 1973 No samples of individual tree saps were kept by gravity from a constant head tank to the were 1.2, 1.9 and 1.8%, respectively. during this season. In 1976, the sap of each first compartment. Partially concentrated In Quebec, three species of birch are tree was sampled daily at the time of sap flowed over weirs cut at successively commonly found: B. populifolia (grey collection and the rest of the sap was lower heights in the partitions into CANADIAN AGRICULTURAL ENGINEERING, VOL. 20 NO.l, JUNE 1978 EVAPORATOR CONDENSATE OUT VALVE Figure 1. The steam-heated evaporator. Figure 2. Average daily sap production per tree during the 1975 season. consecutive boiler compartments. A Observations during the 1976 Season stand pipe in the last compartment permitted Tree diameters were normally distributed continuous operation; the lack of adequate (5% significance, chi-square); the average control equipment made the utilization of diameter was 17.4 cm (SD = 2.8 cm). this feature impossible. The incoming sap Sap was obtained from the trees between flow rate was therefore manually adjusted so 8 April and 28 April inclusive (21 days). Not that the final compartment would not all trees commenced and finished sap overflow for up to 6 h of operation. All production simultaneously; during the 21- steam coils were mounted 7.5 cm above the day season, the average production period bottom of the boiler to prevent the syrup for trees was 16 days. By 28 April, sap flow from becoming excessively concentrated had decreased significantly (Fig. 3a) and the when the incoming sap flow rate became birch sap had acquired its characteristic inadequate to utilize the heat supply either unpleasant flavor and odor signalling the as a result of pump failure, line clogging or end of the collection season. Subsequent to exhaustion of sap in the reservoir. A sap the removal of spiles and buckets from the flow rate of approximately 0.20 //min trees, sap continued to be exuded from the usually proved adequate. Upon exhaustion tap holes in some trees for another 3 wk. The of the available sap, partially concentrated average daily sap production per tree is syrup from the first four compartments was shown in Fig. 3a. manually transferred to the last The average total quantity of sap compartment and there concentrated to produced per tree during the collection 50% (w/v) sugar as determined by the period was 27.9 / (SD = 21.0 /). The total refractometer. The syrup was transferred quantity of sap produced per tree was from the boiler to 1-/ bottles and stored in a normally distributed as determined by the refrigerator at 4°C for further analysis. chi-square test (5% significance level). The Fourteen batches of syrup were thus total quantity of sap collected and processed produced, the first batch from the saps was 1,395 /. collected up to and including 14 April, the The average daily sap dissolved solids fourth batch being produced from the contents (henceforth referred to as the sugar combined sap collected on 17 and 18 April content) is shown in Fig.