4. 1. Introduction
• Cold plasma is a disruptive technology to
many current food-manufacturing processes,
including thermal processing, chlorine wash,
chemical fumigation, etc.
• Success of a technology in the food industry
requires both disrupting the use of an
incumbent and introducing an alternative.
Consumers’ desire
high-quality, nutritious,
“fresh-like” foods with no
artificial preservatives or
chemicals for themselves
Other factors which are driving the interests of
food producers, processors, distributors, and
retailers in exploring and adopting cold plasma
technologies include:
(1) potential extension of product shelf life and
lower consumer food waste;
(2) maximum retention of food quality and lower
food processing and storage losses;
(3) low energy requirement, which is more
“green” than current technology;
(4) low operational and maintenance costs; there is
a need for simple systems with minimal
maintenance and sanitation requirements;
(5) enhanced chemical safety of foods, including
plasma inactivation and the removal of
pesticide and chemical residues; and
(6) green technology and environmental
sustainability
5. 1. Introduction
Strawberries
high-pressure processing (HPP)
pulsed
electric
field
(PEF)
UV light processing
cold
plasma
HPP is not suitable for high
porosity foods, which
includes strawberries
PEF and
ultrasound are
suitable for
liquid foods
“shadowing effect” is a major issue
in various gas mixtures, significantly
reduce bacterial and fungal counts on
strawberries, while retaining quality
parameters such as color, texture, and
sensory attributes, could reduce most
pesticide residues
Most plasma technologies require less
power for their operation, and being in a
gaseous state, they leave no harmful
chemical residues
(Misra et al., 2014a,c; Schnabel et al., 2015).
The three major challenges for widespread use of
atmospheric plasma as a food manufacturing tool
are:
(1) regulatory approval,
(2) designing the plasma source, and
(3) process control.
6. 2. Regulatory Approval
Example
Food regulations in the United States are a patchwork of
rules and regulations that have developed over time. For a
single food, there are numerous government agencies
that have inspection roles.
The FDA has responsibility to ensure the safety of all
foods under the Federal Food
Drug and Cosmetic Act of 1938 (FFDCA) and the Food
Additives Amendment of the
FFDCA in 1958 (FDA, 2015a).
• Each country has food regulations framework and
their own individual process for regulatory review
and approval of new technologies.
• Acceptance of data or conclusions reached from a
regulatory review may significantly differ
between countries
Others
• Federal Food, Drug, and Cosmetic Act
Section 201 (f) defines “food” as
articles used for food or drink for man
or other animals, chewing gum, and
articles used for components of any
such articles (FDA, 2015a).
• FSIS has the primary responsibility for
food safety of meat, poultry, and egg
products under the Meat Product
Inspection Act (1906) (FSIS, 2006a)
• Poultry Product Inspection Act (1957)
(FSIS, 2006b) and Egg Product
Inspection Act (1970) (FSIS, 2006c).
7. There are three main pathways for FDA regulatory review:
(1) Generally Recognized as Safe (GRAS) Self-Affirmation;
(2) Food Contact Notification Petition; and
(3) Food Additives Petition.
FDA’s voluntary GRAS notification program was established in 1997
2. Regulatory Approval
asked for more information
and await further review.
manufacturer to make
a scientific assessment
of food technology or
food process
intervention
manufacturer of a GRAS
designated technology or
process intervention has
the option of going
directly to market or to
notify the FDA of its
GRAS self-determination
and await an FDA
review
Notification to the FDA allows
the FDA to accept the decision
with “no questions,”
8. 2. Regulatory Approval
• an indirect food additive, food contact substances (FCSs) are including packaging, that indirectly or
incidentally contact a food as a result of the manufacturing process, but are not directly added as
ingredients.
• Food contact notification is
required for new use of FCS (not
GRAS)
• But it is GRAS, no need of FCN
(2) intended use, use level (amount of the food
additive proposed for use), and labeling
(cautions, warnings, shelf life, directions for use)
(3) data establishing the intended effect
(physical, nutritional) or other technical
(4) a description of analytical methods to
determine the amount of the food additive in
the food;
(5) safety evaluation;
(6) proposed tolerances for the food
additive;
The information required for submission in a food
additive petition (FAP) review is similar to the FCN and
outlined in 21 CFR 571.1(c).
FAP requires: (1) Name and all pertinent information
concerning the food additive, including chemical identity
and composition of the additive or manufacturing
methods and controls if the chemical identity and
composition are not known;
9. (7) proposed regulation; and
(8) environmental assessment. Some of the data
requested for this review requires involvement
with other government agencies such as the
Occupational Health and Safety Administration
(OSHA) and the Environmental Protection
Agency (EPA)
2. Regulatory Approval
• In the United States, the FDA has designated
ozone as GRAS, so any device claiming
ozone generation does not require FDA
regulatory review or approval. If one
generates reactive gas species other than
ozone, then the question of which path to
proceed for a regulatory review
• single biggest obstacle to the adoption of
plasma technology in the food industry is the
regulatory approval process
10. 3.1 FEATURES AND DESIGN OF THE MACHINE
• most research work concerned with atmospheric
cold plasma treatment of foods seeks to establish
the process conditions for maximum
microbiological decontamination and minimum
damage to the nutritional and sensorial quality of
foods.
• The first one - understanding the chemistry of
atmospheric cold plasmas, particularly air
plasmas.
• A simple air (oxygen, nitrogen, water vapor)
plasma has been documented to produce more
than 75 unique chemical species and involve 500
simultaneous chemical reactions, at four different
time scales (nanosecond, microsecond,
millisecond, and seconds).
• Second, plasma analytics - power
consumption, power density, voltage
gradient, excitation frequency, gas flow,
optical emission spectroscopy
measurement, absorption spectroscopy
measurement, to harmonize the research
efforts across the globe and accelerate
developments in plasma applications for
the food, bio and medical industries.
• Finally, the design of scaled-up plasma
processes and devices should not take
precedence over health and safety issues
of the operators and the work
environment
11. 3.1 FEATURES AND DESIGN OF THE MACHINE
• The first and foremost expectation of the food industry for a cold plasma processing machine
would be the ability it has to bring about the desirable effects in foods - antimicrobial action,
extension of shelf life, and operation at room temperatures.
• If plasma sources with such capabilities can be made commercially, plasma technology will find
broad acceptance.
• Plasmas generated in noble gas or gas mixtures other than air or common gases could prove to
be limited to processing high-value foods or functionalized ingredients.
• In some applications, noble gases have benefits over air.
• An example of this includes the use of argon cold plasma for enhancing the extraction from
oleogeneous plant materials.
• The ability to process continuously at high speed and for several days to months with the least
maintenance and the machine design must be hygienic.
12. 3.1 FEATURES AND DESIGN OF THE MACHINE
• for a high-voltage plasma processing machine,
this may not be true considering the possibility of
arcing, induced/eddy currents in metallic parts.
• In addition, appropriate shielding, insulation and
good grounding is also to be ensured.
• a system needed to monitor the ambient “toxic”
gas levels in the vicinity of the machine, and an
active system to capture or destroy any residual
reactive gas species, eg, using carbon filters.
• it is worth mentioning some of the emerging
organizations involved in the fabrication of cold
plasma systems for applications in the food
industry
• Openair® non equilibrium plasma
technology for surface modification.
• This process is commercially used for
increasing the surface tension on bottle
caps, which allows printing with solvent-
free food-safe inks on high speed lines.
13. 3.2 REFERENCE PLASMA SOURCE
• Sandia National Labs developed the blueprints for
the GEC reference cell (Olthoff and Greenberg,
1995).
• The GEC reference cell is essentially a parallel-
plate, capacitively coupled, RF plasma reactor.
• The development of this standard reference cell
strongly boosted the study of plasma physics of the
etching chemistries and also helped to develop
diagnostics to be used on commercial plasma
systems.
Fig. Photograph of a “standard-configuration”
GEC Cell sustaining a 200 V, 133 Pa argon plasma.
Picture Ref: Olthoff, J. K., & Greenberg, K. E. (1995). The gaseous electronics conference RF reference cell—An
introduction. Journal of research of the National Institute of Standards and Technology, 100(4), 327.
14. 3.2 REFERENCE PLASMA SOURCE
Fig. Schematic cross section diagram of a standard-
configuration Gaseous Electronics Conference RF
Reference Cell. Picture Ref: Olthoff, J. K., & Greenberg, K. E. (1995). The gaseous electronics conference RF reference cell—
An introduction. Journal of research of the National Institute of Standards and Technology, 100(4), 327.
• The main chamber, ports, and manifold are
constructed of conventional stainless-steel ultrahigh
vacuum (UHV) components.
• The top and bottom of the chamber consist of 13 ¼ in
diameter flanges, and the inner chamber diameter is
25.1 cm.
• GEC Cell has two parallel-plate electrodes with a
diameter of 10.2 cm (4 in) and a fixed interelectrode
spacing of 2.54 cm.
• These electrodes are supported by ceramic or Teflon3
insulators that utilize Viton O-rings for vacuum seals.
15. • a movable electrode configuration which allows continuous adjustment of the interelectrode spacing
from 1.27 cm to 6.35 cm.
• Two 8 in ports provide optical access extending beyond the diameter of the electrodes, while four 2 ¾
in ports provide access to the discharge region for pressure gauges, residual gas analyzers, Langmuir
probes, and laser beams.
• Two 6 in ports are also provided, one of which is used for connection to a turbo molecular pump in
order to achieve base pressures near 10^-5 Pa.
• a pressure range of approximately 1 Pa to 133 Pa (approximately 8 mTorr to 1000 mTorr).
• gases: Ar, O2, N2, He, H2, SF6, CF4, C2F6, CHF3, Cl2, NF3, and various mixtures of these gases.
• ceramic insulators are quite expensive and suppliers continue to be difficult to find. Thus many of the
newest GEC Cells have been equipped with Teflon insulators.
3.2 REFERENCE PLASMA SOURCE
16. Fig. Some important variables governing the plasma treatment of food articles
17. Summary
• Cold plasma is disruptive technology and it can reduce bacterial and fungal counts on
strawberries, while retaining quality parameters such as color, texture, and sensory attributes,
could reduce most pesticide residues
• Design of machines need three considerations: chemistry, plasma analytics and design
(hygienic)
• Each country has a framework to approve the technology for the food industry including even
packaging
• Jets, barrier discharges and microwave plasma sources all have potential merit for the treatment
of foods due to wide variety of food products and their unique attributes (e.g, enzyme
inactivation, microbial reductions, pasteurization, sterilization).
• a range for each operational parameter (eg, power density, voltage, current, frequency, etc.)
should also be agreed upon
