chapter  13
38 Pages

Mechanochemically Assisted Extraction

Size of Particles ................................................................................ 362 13.1.2 Improvement of Plant Material Grinding Ef™ciency Using

Preliminary Chemical Treatment ..................................................... 363 13.1.3 Changes in the Structure of Defects and Solid-Phase Reactivity

Enhancement in Extraction Processes ..............................................364 13.1.4 Chemical Reactions of Low-Molecular Intracellular Substances

during Mechanical Treatment ...........................................................366 13.1.5 Hydrothermal (Quasi-Autoclave) Conditions under Mechanical

Treatment of Heterophase Mixtures ................................................. 367 13.2 Structural Features of Biogenic Raw Materials that Are Essential for

Mechanochemical Processes ........................................................................ 368 13.2.1 Structure and Chemical Composition of Some Plant Tissues .......... 369 13.2.2 Disintegration of Plant Raw Material to Particles of about

80 μm in Size .................................................................................... 370 13.2.3 Structure and Chemical Composition of Cell Walls ........................ 371 13.2.4 Disintegration of Plant Raw Material to Particles of about 1 μm

in Size ............................................................................................... 371 13.2.5 Structural Features of Biogenic Unicellular Raw Material

(Example: Yeast Biomass) ................................................................ 372 13.2.6 Destruction of Biogenic Unicellular Raw Materials during

Mechanical Treatment ...................................................................... 373 13.3 Optical and Electron Microscopic Studies of the Activation of Plant

Raw Materials during Intensive Mechanical Treatment .............................. 373 13.4 Mechanochemical Reactions Used for Increasing Ef™ciency of the

Extraction Process ........................................................................................ 375 13.4.1 Depolymerization of Cell Wall Biopolymers ................................... 375

13.4.1.1 Acid Hydrolysis of Polysaccharides in Lignocellulose Raw Materials .................................................................... 376

13.4.1.2 Enzymatic Hydrolysis of the Polysaccharides of Lignocellulose Raw Materials ........................................... 376

13.4.1.3 Factors Determining the Ef™ciency of Using Enzymes .... 377

Traditionally, the major purpose of the mechanical treatment of raw material before extraction is to reduce the size of its particles to optimize the relationship between internal diffusion inside separate particles and external diffusion in the permeable powder layer. The size of particles is important for internal diffusion resistance. With increase in raw material grinding ef™ciency, the total of the particle surface area and the contact area between the raw material and the solvent increases, internal diffusion resistance decreases, the number of destroyed cells of the raw material increases, and the extracting agent better penetrates into the cell. However, hydrodynamic conditions of the extracting agent ªow through a layer of particles worsen substantially with decreases of the particle size, because the external diffusion resistance increases to a higher extent than the internal diffusion resistance decreases. An optimal particle size making minimal the sum of internal and external diffusion resistances should be determined for the each type of raw material and for each condition of extraction. A usual range of the plant raw material particle sizes optimal for water and water-alcohol mixture extraction is 0.33 to 1.0 mm.