Thermal Food Processing

Ohmic Heating for Food Processing 461
Several additional points associated with the fundamentals of ohmic processing
must be addressed. In the particular case of a continuous-flow ohmic heater, the flow
properties of the food components must be fully characterized and related to the
temperature profiles of those components. These phenomena may be considered
from a macroscopic point of view. However, microscopic phenomena also take place.
At this level, disruption of cell membranes, structural changes in food components
(including enzyme inactivation), and mass transfer phenomena must be considered.
Also, novel applications and a deeper knowledge of current applications must
be obtained. Obviously, further research and development work on OH in these
areas are essential.
Research is required in the following areas:
• To elucidate on the relative importance of electric current properties
and the corresponding temperature values on the killing of microbes
and in particular resistant structures (e.g., spores).
• To evaluate the effect of OH on microbial toxins (e.g., mycotoxins).
• To characterize the effect of OH on the nutritive, organoleptic, and
functional properties of foods. This work should be initiated by studying
the effects on individual food components, including water, and
should be extended to whole food products. At this point, it must be
emphasized that each food product requires specific treatments.
• To characterize the flow of the food components when being processed
in an ohmic heater by developing adequate hydrodynamic models.
• To develop methods that will allow for a more precise mapping of
temperatures on foods submitted to OH.
• To develop models that can adequately describe ohmic processing of foods.
• To implement these models so that an adequate control of the rate of
heating can be achieved, thus minimizing the thermal degradation
effects on desirable product attributes but maintaining a safe product.
In terms of process development, the more relevant points to be addressed are:
• Food preservation (with respect to spores and filamentous fungi).
• Food processing — Application of OH to particulate foods (food purees
containing particles, food suspensions, etc.) and foods with a non-
Newtonian rheological behavior.
• Food processing — Integration of OH in existing food industries as an
alternative to conventional preheating, in those cases where higherquality
products and more efficient processing are to be obtained.
• Food thawing and water removal processes (evaporation and dehydration).
• Application to fermentation processes. This includes how electrical
current affects microbial metabolism and membrane and cell wall
transport properties.
• Extraction and purification processes — The possibility of applying an
electrical field to existing processes to increase the yields and purification
of biological macromolecules.