BLBS102-c40 BLBS102-Simpson March 21, 2012 14:23 Trim: 276mm X 219mm Printer Name: Yet to Come
768 Part 7: Food ProcessingSeparation operations are interphase mass transfer processes
because they involve certain heat, mass, and phase transfers,
as well as chemical reactions among food components. The
engineering properties of the targeted food components via
separation systems include separation modeling, simulations,
optimization control studies, and thermodynamic analyses. The
principles of mass conservation and component transfer amounts
are used to analyze and design industrial processes. Molecular
intuition and a thermodynamic approach constitute powerful
tools for the design of a successful separation process. The fol-
lowing issues of engineering properties are important for process
optimization and simulation.- Chemical equilibration—binary, ternary, and multicom-
ponent systems in solid–liquid contacting operation, - Diffusivity (pressure diffusion, thermal diffusion, gaseous
diffusion) and convection, - Solubility of targeted components under different separa-
tion operating conditions, - Iso-electric points and charge dependence on pH,
- Chemical interaction kinetics (colloid formation and
affinity), - Physical properties of particles of the food material,
- Flux and fouling properties in membrane separation pro-
cesses, - Solvent selection, recycling, and management,
- Nature of solvents, optimum composition of mixed sol-
vents for certain nutrient separations, and solvent residues
in food products are factors to be optimized. - Some solvent treatments such as evaporation, concen-
tration, de-watering, de-coloring, toxicological anal-
yses, waste minimization, recycling, and disposal are
necessary.
SEPARATION SYSTEM DESIGN
Technical Request for a Separation SystemAn important consideration in determining the appropriateness
of a separation technique and system is the actual purity require-
ment for the end products. In design of organic solvent (toxic
chemical)-free separation technologies and systems, there are
several essential technical approach requirements for technol-
ogy advances, such as combination of new techniques available
for system optimization, product design and reasonable sepa-
ration and purification steps, environmentally friendly process,
less air pollution and industrial waste (e.g., energy, greenhouse
gases emission, reduction of waste water production), and eco-
nomic feasibility and raw material selection.Food Quality and Separation SystemThe major issues related to product quality after separations
are the impacts of processing on bioactive compounds and the
nutritional aspects of foods, as well as the quality character-
istics. To meet the food safety regulations, no toxic chemical
solvent residues are permitted in the end food products, e.g.,
“green” food products. Nutrition and health regulations must bemet. Also important are a high stability of nutrients and bioac-
tive components, processes operating at low temperatures to
reduce thermal effects, processes that exclude light to reduce
light induced (UV) irradiation effects, and processes that ex-
clude oxygen to reduce oxygen effects. And the final product
must maintain uniformity and quality consistency, and purity
can meet food grade or pharmaceutical grade requirements.Scaling Up Technology for Industrial
ProductionScaling up of a natural product separation process is by no
means a simple affair. The enormous variations from process
to process necessitate careful attention to details at all stages of
product development. When the technology in a food process
is designed for industrial-scale production, an important area
for consideration is the balance of capital and operating costs
as the scale of the separation operation increases. Scale up of
separation technology also involves optimization with respect to
increasing the efficiency of each stage, giving rise to increasing
demands on the accuracy of the assay system.NEW TECHNOLOGY DEVELOPMENT
Extraction of health-promoting components from plant materi-
als has usually been accomplished by conventional extraction
processes such as solid–liquid extractions employing methanol,
ethanol, acetone, or hexane and also through steam distillation
or evaporation processes to remove solvents from extracts. Cur-
rently, the demand for natural bioactive compounds is increasing
due to their use by the functional food and pharmaceutical in-
dustry. Thus, there has been increasing interest in the use of en-
vironmentally friendly “green” separation technologies able to
provide high quality–high bioactivity extracts while precluding
any toxicity associated with the solvent. Some of the motivations
to employ “green” separation technologies as a viable separation
technique are (a) tightening government regulations on toxic-
chemical solvent residues and pollution control, (b) consumers’
concern over the use of toxic chemical solvents in the process-
ing, and (c) increased demand for higher quality products that
traditional processing techniques cannot meet.
One of the most important considerations in developing new
extraction processes is the safety aspect. In this sense, a variety
of processes involving extractions with supercritical CO 2 fluid
extraction, membrane-based separation, molecular distillation,
and pressured low-polarity water extraction, etc., are generally
recognized as “green” separation technology and are consid-
ered clean and safe processes to meet the requirements (Ib ́anez ̃
et al. 1999, Fernandez Perez et al. 2000, Herrero et al. 2006,
Chang et al. 2008). They have been developed and are regarded
as innovative emerging separation technologies that meet food
quality and safety requirements. These processes can be used
to solve some of the problems associated with conventional or-
ganic solvent-oriented separation processes. Operation parame-
ters and other factors related to the quality of the original plant,
its geographic origin, the harvesting date, its storage, and its
pretreatment process prior to extraction also influence the