Protein Processing in Food and Bioproduct Manufacturing and Techniques for Analysis - Food and Industrial Bioproducts and Bioprocessing - page 86

Starting material
Material preparation
(e.g., cleaning, dehulling, grinding, communition, etc.)
Fat extraction
(if necessary)
Protein extraction
Centrifugation / filtration
Protein precipitation
Centrifugation / filtration
Protein purification
(if needed)
Protein renaturation
Drying
Protein concentrate / isolate
Figure 3.3 General schematic showing some key unit operations for the wet processing of proteins.
operations used for the wet processing of proteins are presented in Figure 3.3. Deviations to
these operations occur depending on the starting material and the desired end product. The
material preparation step for wet processing will, therefore, vary depending on the source
material.
3.3.1 Dryprocessing
3.3.1.1 Airclassification
Air classification is a milling technique that allows the fractionation of plant grains/seeds
into high starch and high protein flours. The milling process yields flours having particles of
two discrete sizes and densities. Air classification exploits this phenomenon to separate the
light fine fraction (protein) from the heavy coarse fraction (starch).
During air classification, whole or de-hulled seed is ground into very fine flour, and the
flour is subsequently classified in a spiral air stream to separate the starch from the protein.
Repeating the process a few times improves separation efficiency, as protein bodies can
still adhere to the surface of starch granules after the initial run. Agglomerates present in
this initial starch fraction consist of starch granules embedded in a protein matrix, but by
repeated pin milling and air classification, further purification can be obtained (Gueguen
et al ., 1984 ).