PHYSICAL AND CHEMICAL PROCESSES IN MASHING. EFFECT OF PARTICLE SIZE

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Abstract
The relative importance of the various physical and chemical processes as they affect the overall rate of mashing has been studied. With sufficiently small particles the physical processes occur rapidly and the chemical reaction is rate-limiting. With large particles, the rate of the chemical reaction is small compared with the slower processes of diffusion. An idealized model of spherical particles, incorporating diffusion with generation and degeneration of the diffusing species can be used to give an approximately quantitative description of the mashing system. The distribution of saccharide end-products appears to be almost independent of particle size, except for particles small enough to pass through 52 BSS mesh and, even then, the distribution varies only during the initial stages of mashing. Under the conditions employed, the contribution of α-amylase in the hydrolysis of starch appears to be highly significant.