Maple sap

Ahom, m. maple, -holz, n. maple(wood). -melasse,/. maple sirup, -salt, m. maple sap. -sSure, /, aceric acid, -zucker, m. maple sugar. 

Collecting maple sap and converting it to maple syrup utilize many of the chemical principles found in this chapter. 

The collection of maple sap and its conversion to syrup or sugar illustrate many of the principles covered in this chapter. Moreover, in northern New England, making maple syrup is an interesting way to spend the month of March (Figure A), which separates midwinter from "mud season."... 

The driving force behind the flow of maple sap is by no means obvious. The calculated osmotic pressure of sap, a 2% solution of sucrose (MM = 342 g/mol), is... 

Boiling maple sap. It seems to take forever to boil down maple sap until you reach 101°C. Then the temperature rises repidly to the end point. 104°C. Further careful heating produces maple sugar. 

Assume that 30 L of maple sap yields one kilogram of maple syrup (66% sucrose, C12H22Ou). What is the molality of the sucrose solution after one fourth of the water content of the sap has been removed ... 

Previously, Yu et al (2005) studied the increase of a co-biopolymer of PHBV by Ralstonia eutropha in a continuous stirred tank reactor. It was found that the productivity rate increased when sodium propionate was used as the carbon source. Later, Yezza et al (2007) investigated the use of maple sap as a carbon for PHB production by A. latus. The productivity of PHB reached 2.6 gH h-i. 

Maple Svrup. The typical flavor of maple syrup which originates during the heat concentration of maple sap in the presence of air has also been extensively investigated (70-80). Important sugar-based degradation products present in maple syrup include 3-methylcyclopentane-l,2-dione and 2,5-dimethyl-4-hydroxy-3(2H)-furanone. 

After collection, maple sap must be transformed through some means of concentration into maple syrup. The two major processes utilized are evaporation by heating and reverse osmosis followed by heating. The modem maple evaporator (Fig. 4.2) is typically composed of several... 

Maple sap is a dilute solution of mainly water and sugar, along with trace amounts of other substances, including organic acids, free amino acids, protein, minerals, and phenolic compounds. Although the proportions are somewhat variable, sap is normally composed of 95-99% water and 1-5% sugar. 

TABLE 4.1 Sugar composition (% dry weight) of the solid fraction of maple sap (from Perkins et al., 2006, used with permission)... 

A wide range of free amino acids are found in sterile maple sap (Heiligmann et al., 2006), including glycine, alanine, asparagines, threonine, leucine, isoleucine, valine, and methionine. Morselli and Whalen (1986) examined the change in the distribution of various amino acids over two maple sap seasons. Their results indicated that initially, only a small number (6-7) of amino acids were found in sap, all in relatively low concentration. As the season progressed, the diversity of amino acids increased to 12-15. In addition, the concentration of amino acids present... 

TABLE 4.2 Inorganic (minerals and metals) composition of maple sap... 

Uncontaminated maple sap has the same appearance as water in that it is nearly colorless, with very high light transmission through the visible range (Fig. 4.4). Some absorption is found in sections of the UV and near infrared (NIR) ranges. 

Several organic acids are also found in maple sap (Table 4.3). In general, the total quantity of organic acids starts out low, and rises throughout the sap flow season. Malic acid (concentration 800M5,000 ppb) is by far the most common organic acid, ranging from just over 50-99% of the total acid present. Succinic acid and oxalic acid are also fairly dominant forms. Other acids occur sporadically in low concentration (Dumont, 1994 Mollica and Morselli, 1984). 

A wide range of phenolic compounds, varying in type and concentration, can also be found in maple sap (Dumont, 1994). Most of these appear to be derived from lignin (Kermasha et ah, 1995). They range in concentration in sap up to 0.1 ppm. The most dominant phenols present tend to... 

FIGURE 4.4 Transmission profile of maple sap at 2 °Bx from 190-1100 nm. Sap was collected on March 29, 2006, then stored frozen until analyzed. 

TABLE 4.4 Phenolic compounds in maple sap (after Dumont, 1994)... 

There is an increasing interest in the quantity and composition of phenols in maple sap and syrup, due to the antioxidant, antiradical, and antimutagenic activities of these compounds (Theriault et ah, 2006). 

FIGURE 4.6 Changes in temperature (A), sugar content (B), pH (C), conductivity (D) and light transmittance (E) at different stages of thermal processing from maple sap to syrup. 

Bazinet, L., Gaudreau, H., Lavigne, D., and Martin, N. (2007). Partial demineralization of maple sap by electrodialysis Impact on syrup sensory and physicochemical characteristics.. Sci. Food Agric. 87,1691-1698. 

Cirelli, D., Jagels, R., and Tyree, M. T. (2008). Towards an improved model of maple sap exudation The location and role of osmotic barriers in sugar maple, butternut and white birch. Tree Physiol. 28,1145-1155. 

Edson, H. A. and Jones, C. H. (1912). "Micro-Organisms of Maple Sap." Vermont Agric. Exp. Sta. Bull. 167. University of Vermont and State Agricultural College, Burlington, VT. 

Favreau, D., Sosle, V., and Raghavan, G. S. (2001). Microwave processing of maple sap to maple syrup and maple syrup products. ]. Microw. Power Electromagn. Energy 36, 25-35. 

Taylor, F. H. (1956). "Variation in Sugar Content of Maple Sap." University of Vermont, Agricultural Experiment Station Bulletin 587. 

Tyree, M. T. (1983). Maple sap uptake, exudation and pressure changes correlated with freezing exotherms and thawing endotherms. Plant Physiol. 73, 277-285. 

Caramel is unintentionally generated in burnt carbohydrate foods (rice, oatmeal, cornmeal, etc.) and molasses (Kowkabany et al., 1953) it is the source of maple flavor and color in the concentration of maple sap to maple syrup (Stinson and Willits, 1965). In industrial manufacturing, the intended application is taken into account, because reaction conditions help determine the properties of the pyrolysate, e.g., its tinctorial value, water solubility, and alcohol stability. Tinctorial value refers to the absorbance at 560 nm of a 0.1-wt/vol% solution in a 1-cm cell. Tinctorial strength increases with acidity, temperature, and duration of heating. Caramel manufactured above pH 6.3 is biologically unstable and much below pH 3.1, it is a resin. 

---