Size methods skimming

Kovacova (1990) describes a method for the batch drying of fruit and vegetable pulp in a fluidized bed in which carrier particles (variously crystalline and caster sugar, dried skim milk, potato and wheat starch, apple powder, semolina or oat flakes), pre-moistened to a solids content of between 55% and 76%, are fed to a preheated fluidized bed and sprayed with the pulp to be dried. A product with a narrow particle size distribution and a uniform pulp content is claimed. Specific foods for which fluidized bed granulation has been used include potato puree (Zelenskaya and Filipenko, 1989) and granulated dried apple (Haida et al, 1994). 

The caseins exist in milk as polydisperse aggregates ranging in size from ca. 40 to 220nm (3), but the size distribution of micelles depends upon the method of measurement. These casein micelles scatter light and are responsible for the whitish, opaque nature of skim milk. The casein micelles are also associated with a colloidal apatite comprised of calcium-phosphate-citrate (CPC) which has a stabilizing influence on the micelle structure. The colloidal CPC is in equilibrium with soluble CPC in the milk serum phase and is solubilized as the pH is reduced. Thus, as the pH is reduced to the isoelectric point of the caseins (4.6), the colloidal CPC solubilizes, and the caseins precipitate (143). This phenomenon should be kept in mind during some of the following discussions. 

Figure 1.19. Possible error sources in the integration of chromatographic peaks. (A) Tangent skimming and perpendicular drop methods to assign peak boundaries for fused peaks (B) the misproportionation of the true peak area between two incompletely separated peaks of different size (C) loss of peak area due to integration with a threshold value set too high and (D) variation of peak area due to differences between the real sloping baseline and the interpolated integrator baseline.

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