Abstract
Xylem sap obtained from radiata pine sapwood using a supercritical CO2 (scCO2) dewatering process contained a complex mixture of solutes comprising carbohydrates, amino acids, alkanoic and diterpene acids, neutral diterpenoids, β-sitosterol and cyclitols. Sap also contained free phosphoric acid which is known to catalyse the condensation reactions between glutamic and aspartic amino acids and glucose, galactose and fructose to form Maillard products. When heated these Maillard products lead to the formation of melanoidins, which are partly responsible for the formation of kiln brown stain (KBS) when green radiata pine sapwood is kiln dried. The cyclitols, which are major components in sap, have been shown to undergo phosphoric acid-catalysed dehydration reactions under kiln drying conditions to give methoxyl derivatives of hydroquinone, catechol, resorcinol and O-methylphloroglucinol. These reactive phenols are known to exothermally condense with formaldehyde and could also react with other short carbon chain aldehydes generated during kiln drying. The products of these chemical reactions are extended π-orbital aromatic polymers which are darkly-coloured and would be expected to contribute to KBS. This paper describes the chemistry of sap from radiata pine sapwood using scCO2 dewatering and proposes new theory on KBS formation invoking thermal dehydration and retro Diels-Alder chemical reactions of the sap cyclitols.
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.
Research funding: None declared.
Employment or leadership: None declared.
Honorarium: None declared.
References
Anderson, K.B., Collins, M.J., Franich, R.A., Kroese, H.W. (1992) Formation of 7-ketodehydroabietic acid at the radiata pine wood surface, and its effect on wood yellowing. J. Wood Chem. Technol. 12:323–333.10.1080/02773819208545238Search in Google Scholar
Behr, V.C., Hill, S.J., Meder, R., Sandquist, D., Hindmarsh, J.P., Franich, R.A., Newman, R.H. (2014) Carbon-13 NMR chemical-shift imaging study of dewatering of green sapwood by cycling carbon dioxide between the supercritical fluid and gas phases. J. Supercrit. Fluid. 95:535–540.10.1016/j.supflu.2014.08.026Search in Google Scholar
Cranswick, A.M., Rook, D.A., Zabkiewicz, J.A. (1987) Seasonal changes in carbohydrate concentation and composition of different tissue types of Pinus radiata trees. NZ. J. For. Sci. 17:229–245.Search in Google Scholar
Dawson, B.S.W., Pearson, H., Kroese, H.W., Sargent, R. (2015) Effect of specimen dimension and pre-heating temperature on supercritical CO2 dewatering of radiata pine sapwood. Holzforschung 69:421.10.1515/hf-2014-0055Search in Google Scholar
de Kok, P.M.T., Rosing, E.A.E. (1993) Reactivity of peptides in the maillard reaction. In: Thermally Generated Flavors. Chapter 13, Vol. 543. Eds. Parliment, T.H., Morello, M.J., McGorrin, R.J. ACS Symposium series. pp. 158–179.10.1021/bk-1994-0543.ch013Search in Google Scholar
Echavarrıa, A.P., Pagan, J., Ibarz, A. (2012) Melanoidins formed by maillard reaction in food and their biological activity. Food. Eng. Rev. 4:203–223.10.1007/s12393-012-9057-9Search in Google Scholar
Faix, O., Meier, D., Fortmann, I. (1990) Thermal degradation products of wood. Holz. Roh. Werkst. 48:281–285.10.1007/BF02626519Search in Google Scholar
Faix, O., Fortmann, I., Bremer, J., Meier, D. (1991) Thermal degradation products of wood. Holz. Roh. Werkst. 49:299–304.10.1007/BF02663795Search in Google Scholar
Franich, R.A., Goodin, S.J., Wilkins, A.L. (1984) Acetamidofurans, acetamidopyrones, and acetamidoacetaldehyde from pyrolysis of chitin and n-acetylglucosamine. J. Anal. Appl. Pyrol. 7:91–100.10.1016/0165-2370(84)80043-1Search in Google Scholar
Franich, R.A., Gallagher, S., Kroese, H.W. (2013) Wood drying. U.S. Patent 8,578,625. 29.Search in Google Scholar
Franich, R.A., Gallagher, S., Kroese, H. (2014) Dewatering green sapwood using carbon dioxide cycled between supercritical fluid and gas phase. J. Supercrit. Fluid. 89:113–118.10.1016/j.supflu.2014.02.019Search in Google Scholar
Franich, R.A., Meder, R., Falge, M., Fuchs, J., Behr, V.C. (2019) Uncovering supercritical CO2 wood dewatering via interleaved 1H-imaging and 13C-spectroscopy with real-time reconstruction. J. Supercrit. Fluid. 144:56–62.10.1016/j.supflu.2018.10.006Search in Google Scholar
Fullerton, T.J., Franich, R.A. (1983) Lignin analysis by pyrolysis-GC-MS. Characterisation of ethanol lignin pyrolysates and identification of syringyl units in Pinus radiata milled wood lignin. Holzforschung 37:267–269.Search in Google Scholar
Guerrant, G.O., Moss, C.W. (1984) Determination of monosaccharides as aldonitrile, O-methyloxime, alditol, and cyclitol acetate derivatives by gas chromatography. Anal. Chem. 56:633–638.10.1021/ac00268a010Search in Google Scholar
Haslett, A.N. (1994) Drying – the essential difference. NZ Pine Inter. 42–45.Search in Google Scholar
Kallio, H., Ahtonen, S., Rau Lo, J., Linko, R.R. (1985) Identification of the sugars and acids in birch sap. J. Sci. 50.10.1111/j.1365-2621.1985.tb13328.xSearch in Google Scholar
Kreber, B., Haslett, A.N. (1997) Compression-rolling reduces kiln brown stain in radiata pine sapwood. Forest. Prod. J. 47:59–63.Search in Google Scholar
Kreber, B., Fernandez, M., McDonald, A.G. (1998) Migration of kiln brown stain precursors during the drying of radiata pine sapwood. Holzforschung 52:441–446.10.1515/hfsg.1998.52.4.441Search in Google Scholar
Kreber, B., Haslett, A.N., McDonald, A.G. (1999) Kiln brown stain in radiata pine: a short review on cause and methods for prevention. Forest. Prod. J. 49:66–70.Search in Google Scholar
Kreber, B., Stahl, M.R., Haslett, A.N. (2001) Application of a novel de-watering process to control kiln brown stain in radiata pine. Holz. Roh. Werkst. 59:29–34.10.1007/s001070050468Search in Google Scholar
Lohmar, R.L. The Polyols, Part II. The Inositols and Related Compounds. The Carbohydrates: Chemistry, Biochemistry, Physiology. W. Pigman, Academic Press Inc., New York, 1957, pp. 268–298.Search in Google Scholar
McCurdy, M., Pang, S. (2007) Comparison of colour development in sugar-amino acid solutions with colour changes in wood during drying. Asia-Pac. J. Chem. Eng. 2:30–34.10.1002/apj.52Search in Google Scholar
McCurdy, M., Pang, S., Keey, R.B. (2006) Surface colour change in wood during drying above and below fibre saturation point. Maderas. Ciencia y tecnología 8:31–40.10.4067/S0718-221X2006000100004Search in Google Scholar
McDonald, A.G., Fernandez, M., Kreber, B., Laytner, F. (2000) The chemical nature of kiln brown stain in radiata pine. Holzforschung 54:12–22.10.1515/HF.2000.003Search in Google Scholar
McDonald, A.G., Dare, P.H., Gifford, J.S., Steward, D., Riley, S. (2002) Assessment of air emissions from industrial kiln drying of Pinus radiata wood. Holz. Roh. Werkst. 60:181–190.10.1007/s00107-002-0293-1Search in Google Scholar
McHugh, M.A., Krukonis, V.J. Supercritical Fluid Extraction: Principles and Practice. Stoneham, MA, Butterworths, 1986.Search in Google Scholar
Meder, R., Franich, R.A., Callaghan, P.T., Behr, V.C. (2015) A comparative study of dewatering of Pinus radiata sapwood using supercritical CO2 and conventional forced air-drying via in situ magnetic resonance microimaging (MRI). Holzforschung 69:1137–1142.10.1515/hf-2014-0134Search in Google Scholar
Nair, M., Shi, Z., Karwe, M.V., Ho, C.-T., Daun, H. (1993) Collection and characterization of volatile compounds released at the die during twin screw extrusion of corn flour. Thermally generated flavors. T. H. Parliment, M. J. Morello and R. J. McGorrin. Am. Chem. Soc. 334–347.10.1021/bk-1994-0543.ch027Search in Google Scholar
Nakanishi, K. Infrared Absorption Spectroscopy – Practical. San Francisco, CA, Holden-Day. 1962.Search in Google Scholar
Newman, R.H., Franich, R.A., Meder, R., Hill, S.J., Kroese, H.W., Sandquist, D., Hindmarsh, J.P., Schmid, M.W., Fuchs, J., Behr, V.C. (2016) Proton magnetic resonance imaging used to investigate dewatering of green sapwood by cycling carbon dioxide between supercritical fluid and gas phase. J. Superc. Fluid. 111:36–42.10.1016/j.supflu.2016.01.007Search in Google Scholar
Ohara, S., Yasuta, Y., Ohi, H. (2003) Structure elucidation of condensed tannins from barks by pyrolysis/gas chromatography. Holzforschung 57:145–149.10.1515/HF.2003.023Search in Google Scholar
Orman, H.R., Will, G.M. (1960) The nutrient content of Pinus radiata trees. NZ. J. Sci. 3:510–522.Search in Google Scholar
Parrott, A., Hill, S., Raymond, L., Hindmarsh, J. (2015) A magnetic resonance study of the removal of water and secondary metabolites from sapwood using supercritical carbon dioxide. 3rd International Conference on Green Chemistry. La Rochelle, France.Search in Google Scholar
Paterson, A.J. (1975) The water soluble carbohydrates of Pinus radiata: Identification and quantitation. M.Sc., Canterbury, Christchurch, New Zealand.Search in Google Scholar
Ralph, J., Hatfield, R.D. (1991) Pyrolysis-GC-MS characterization of forage materials. J. Agri. Food. Chem. 39:1426–1437.10.1021/jf00008a014Search in Google Scholar
Rizzi, G.P. (1994) The maillard reactions in food. Maillard reactions in chemistry, food and health. T. P. Labuza, G. A. Reineccius, V. Mannier, J. O’Briens and J. Haynes. Roy. Soc. Ch. 151:11–19.10.1533/9781845698393.1.11Search in Google Scholar
Stahl, M., Bentz, M. (2004) High-pressure treatment of wood – combination of mechanical and thermal drying in the I/D process. Chem. Eng. Tech. 27:1216–1221.10.1002/ceat.200406143Search in Google Scholar
Terziev, N. (1995) Migration of low-molecular sugars and nitrogenous compounds in Pinus sylvestris L. during kiln and air drying. Holzforschung 49:565–574.10.1515/hfsg.1995.49.6.565Search in Google Scholar
Walton, J.H., Kepfer, R.J. (1930) Studies on phosphoric acid. II. J. Phys. Chem. 34:543–548.10.1021/j150309a006Search in Google Scholar
Wastney, S., Bates, R., Kreber, B., Haslett, A. (1997) The potential of vacuum drying to control kiln brown stain in radiata pine. Holzforsch. Holzverw. 49:56–58.Search in Google Scholar
Whitford, E.L. (1925) The decomposition of malic acid by sulfuric acid. J. Am. Chem. Soc. 47:953–968.10.1021/ja01681a006Search in Google Scholar
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