BLBS102-c40 BLBS102-Simpson March 21, 2012 14:23 Trim: 276mm X 219mm Printer Name: Yet to Come
40 Separation Technology in Food Processing 765technologies in the food processing area have undergone an
explosive growth. The competitive nature of the biotechnolo-
gies applied to the pharmaceutical and food industries for cost-
effective manufacturing have provided much impetus for the
development and use of new separation techniques on a large
scale, but at a lower cost. Aside from the conventional separation
techniques such as solvent and water extraction (solid–liquid
contacting extraction or leaching), crystallization, precipitation,
distillation, and liquid–liquid extraction, etc., have already been
incorporated in basic food processing and well established and
commercialized. A number of newer separation techniques as
promising alternative methods for improved application in food
engineering have been implemented on the commercial scale,
including supercritical CO 2 fluid extraction, membrane-based
separation, molecular distillation, and pressured low-polarity
water extraction procedures. These newer techniques have made
impressive advances in obtaining adequate segregations of com-
ponents of interest with maximum speed, minimum effort, and
minimum cost at as large a capacity as possible in production-
scale processes. These techniques have been implemented for the
purification of proteins, characterization of aromas, whey pro-
tein removal from dairy products, extraction of health-benefiting
fish oil, and clarification of beverages including beer, fruit juices,
and wine. The separation processes and technologies for high
value-added products are based on their polarity and molecu-
lar size. Many potential high-value products can be developed
from natural resources by different separation technologies and
processes. Carotenoids, including lycopene,β-carotene, astax-
anthins, and lutein, make up a world market nearing $1 billion
with a growth rate of about 3%. Therefore, efforts to utilize natu-
ral agricultural materials for the production of high value-added
products, especially health-promoting foods and ingredients, are
of great interest to the food and biotechnology industries.MAIN SEPARATION PROCESSES IN FOOD
INDUSTRIAL APPLICATIONSSeparation processes such as extraction, concentration, purifica-
tion, and fractionation of nutrients or bioactive components from
agricultural materials are the main processes used to obtain high-
value end products. All separations rely on exploiting differences
in physical or chemical properties of mixture of components.
Some of the more common properties involved in separation
processes are particles or molecular size and shape, density, sol-
ubility, and electrostatic charge. In some operations, more than
one of these physical and chemical properties is involved. As a
unit operation, the separation process plays a key function in the
whole procedure for value-added food processing. The science
of separation consists of a wide variety of processes, including
mechanical, equilibrium, and chromatographic methods.Mechanical Separation ProcessesCentrifugationThe centrifugation process works to separate immiscible liquids
or solids from liquids by the application of centrifugal force. Acentrifuge is a spinning settling tank. The rapid rotation of the
entire unit replaces gravity by a controllable centrifugal or radial
force. Centrifugal separation is used primarily in solid–liquid or
liquid–liquid separation processes, where the process is based
on density difference between the solid or liquids. Centrifuga-
tion is typically the first step in which the suspended solids
or liquids are separated from the fluid phase. Various designs
of centrifuge are used in the food industry such as removal of
solids from juice, beverage, fermentation broths, or dewatering
of food materials. Most centrifugal processes are carried out on a
batch basis. However, some automatic and continuous centrifuge
equipment and process are applied in the food and biotechnology
industry.FiltrationFiltration is the separation of two phases, solid particles or liquid
droplets, and a continuous phase such as liquid or gas, from a
fluid stream by passing the mixture through a porous medium.
Filtration finds applications through the food and biotechnology
industries. Filtration is employed at various stages in food man-
ufacture, such as the refining of edible oils, clarification of sugar
syrups, fruit juice, vinegar, wine, and beer, as well as yeast re-
covery after fermentation. Filtration is also carried out to clarify
and recover cells from fermentation broths in the biotechnology
area.
Filtration can be classified into conventional and nonconven-
tional filtrations. The conventional filtration process uses filtra-
tion media with coarse selectivity and cannot separate similar
size particles. It usually refers to the separation of solid, im-
miscible particles from liquid streams. Conventional filtration is
typically the first step in which the suspended solids are sepa-
rated from the fluid phase.Membrane SeparationNonconventional filtration processes use membrane separation
technology. This nonconventional filtration has evolved into a
quite sophisticated technique with the advent of membranes
whose pore size and configuration can be controlled to such a
degree that the filtration area is maximized while keeping the
total volume of the unit small. A membrane separation process
is based on differences in the ability to flow through a selective
barrier (membrane) that separate two fluids. It should permit pas-
sage of certain components and retain certain other components
of the mixture. Membrane separation processes are classified as
microfiltration, ultrafiltration, and reverse osmosis according to
the pore size of the membranes.Ion-Exchange and ElectrodialysisIon-exchange and electrodialysis are distinct separation pro-
cesses, but both processes are based on the molecular electro-
static charge.