Low molecular weight sugars

The combined action of xylanase and mannanase on sprucewood holocellulose increased the hydrolysis of hemicelluloses without any detectable attack of cellulose. At the end of the experiments—i.e., after 48 hr of xylanase incubation followed by 32 hr of combined xylanase-mannanase incubation—about half the hemicelluloses present in the starting material were selectively converted into low-molecular-weight sugars. The amount of mannan removed was two times higher than after 80 hr of incubation with mannanase only. Unexpectedly, the xylan dissolution was scarcely increased by the combined action of the two hemicellulases. 

Most of the mannan in the sprucewood holocellulose was hydrolyzed by the cellulase-mannanase treatments, and only about one-third of the xylan was dissolved and partly hydrolyzed into low-molecular-weight sugars. 

A further mechanism of transcellular transport is via the aqueous pores which exist in many lipid membranes. The pores are of the order of 0.4 nm in diameter, thus very small hydrophilic molecules such as water, urea and low molecular weight sugars can diffuse through these channels and thus be absorbed by epithelial cells. However, most drags are generally much larger (>1 nm in diameter) than the pore size, and this route is therefore of minor importance for drag delivery. 

Ball, G.F.M. 1990. The application of HPLC to the determination of low molecular weight sugars and polyhydric alcohols in foods a review, Food Chem., 35 117-152. 

This is an essential class for the formation of aroma compounds, mainly by caramelization of the low-molecular-weight sugars and by Maillard reaction with the amino acids (see Section 3.1). 

Contrary to low molecular-weight sugars, polysaccharides (celluloses, pectins, starch), do not specially contribute to flavor formation during the roasting of coffee, but they are the most important aromabinding agents in the beverage (Maier, 1976 Maier and Krause, 1977). 

In order to define this accessibility curve clearly it is necessary to use a number of solute molecules which range in size over the whole range of pore sizes anticipated in the swollen structure. We have found the most suitable solutes to be the dextrans marketed by Pharmacia (Uppsala) Ltd. supplemented by a few low molecular weight sugars. Grotte (7) has reviewed evidence to show that these dextrans behave in solution as hydro-dynamic spheres, and that the diameters of these molecules in solution may be calculated from their diffusion coefficients according to the Einstein-Stokes formula ... 

They also demonstrated that the major volatile phenols (phenol, cresols) were produced primarily by pyrolysis of the alcohol extractable and the final tobacco residue. These fractions acconnted for 38% and 44%, respectively, of the total phenols yield. The alcohol extractables included polyphenolic tobacco pigment and low molecular weight sugars, whereas the final tobacco residue contained the polysaccharides celluloses, starch, pectins, and lignin. All these yield the simple phenols on pyrolysis or during tobacco smoking (248, 2043, 3277, 3305, 3453, 3468, 3767). 

---