[PACKAGING]
by Aaron L. Brody
Activity Today in Active Packaging
A
BreatheWay ®
membranes employ
a unique technology that allows the
membrane patch to physically change in
response to shifts in temperature, becoming
more permeable in warm temperatures and
less so in cold ones. Photo courtesy of Apio Inc.
ctive packaging appeared in the literature of
food packaging as far back as the 1960s—not
that it was much referred to in the early days
under that particular term. During the 1970s, it was
often called smart packaging. Even today,
active and intelligent packaging
concepts are often interchanged even though
those of us in the
disciplines are cognizant of the
profound differences: Intelligent
packaging senses change
and signals; active packaging
senses change and alters its
properties to accommodate
that change.
Throughout the current
decade, we were repeatedly
bombarded by announcements of
active packaging entities that could
enhance food preservation by imparting some
specific functionality to package materials or
structures. These capabilities included retaining
red meat color, controlling moisture in fresh foods,
removing oxygen to retard oxidation, and destroying microorganisms that would spoil or even
introduce toxins into foods. We have been regaled
with discussions of the wonders of ozone, allyl isothiocyanate (AIT), chitosan, silver salts,
anhydrides, cobalt-catalyzed oxidizers, glucose
remains shrouded in a web of hyperbolized claims,
hopes, and mystery. The bottom line is that active
packaging has not approached the expectations of
last year, last decade, or last century. On the other
hand—surprise!—active packaging plays exciting
niche roles in a variety of food packaging and will
quietly expand and grow.
Active Packaging Segments
It is easy enough to list the most interesting and
promising of the contemporary active packaging
technologies.
• Flavor Absorbers are usually activated carbon or cyclodextrins designed to remove trivial
quantities of undesirable odors, but hardly applied
on a commercial basis.
• Flavor emitters include a host of devices
engineered to deliver desirable aromas or scents
when the package is tweaked such as by opening
or twisting closure.
• Ethylene scavengers, which remove gaseous
ethylene vapors from the headspaces of respiring
fruits and vegetables and thus prolong their
chilled shelf lives mostly using the functional
potassium permanganate adsorbed on solids in
sachets in proximity, are usually relatively ineffective but persistent in the market.
• Carbon dioxide scavengers remove excess
carbon dioxide from foods in which it can be damaging as with roasted and ground coffee and some
fruits and vegetables. Calcium oxide reacts with
carbon dioxide to remove it from the atmosphere.
Even in the Internet age, much of the activity in active packaging
remains shrouded in a web of hyperbolized claims, hopes, and mystery.
oxidase, and many more too numerous to enumerate here. Even a new publication on the topic,
Smart Packaging Technologies for Fast Moving
Consumer Goods by Joseph Kerry and Paul Butler
(Wiley, 2008), suffers from being unable to keep up
with the fast-moving and largely unpublished
dynamics of active packaging. Even in the Internet
age, much of the activity in active packaging
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Does any reader recall the in-can carbon dioxide
scavenger sachets in roasted and ground coffee
cans of long ago or recognize the one-way valves
on flexible pouches or plastic or paperboard canisters today? These flutter valves are engineered to
allow the escape of carbon dioxide generated from
roasting or floating among the interstices of the
contained coffee to relieve the pressure.
• Carbon dioxide addition functions by incorporating sodium bicarbonate into the package to
receive water or excess purge from a meat, poultry, or seafood product. Carbon dioxide can be
generated to function as an active antimicrobial
and retard the growth of spoilage microorganisms. The latest in the stream is incorporation
into the tissue pads for plastic trays of poultry.
Coupled with sorbates as a supplementary antimicrobial, carbon dioxide–generating chemicals
in packages extend chilled shelf life by one to
three days, a significant benefit to retail poultry
packers. The supplier of this technology is Paper
Pak Industries (www.paperpakindustries.com).
• Temperature-compensating films include
Intelimer® polymers from Landec (www.Landec.
com), a proprietary polymer technology with side
chains that are capable of expanding with temperature increases to allow greater permeability.
It is perhaps the only pure active package material structure. Intelimer technology can be
provided in a membrane format and thus engineered to allow greater passage of oxygen into
packages of fresh produce susceptible to respiratory anaerobiosis—to prevent oxygen extinction
in a variety of packaging structures (rigid trays,
polypropylene, or polyethylene films, etc.). This
technology is currently employed as BreatheWay®
membranes over openings in fresh produce packaging by Landec subsidiary Apio Inc.
Antimicrobial Package Materials
A flood of natural and other chemicals have been
proposed to counter the growth of spoilage, infectious, and toxin-producing microorganisms that
are ubiquitous in and on foods and their environments. Among the older candidates cited above
are, of course, silver salts, AIT, and almost all
spice and herb extracts. Among the newer entries
are chlorine dioxide, sulfur dioxide, hydrolyzed
water, nisin and related bacteriocins, etc.
With all of these possibilities, what are the
issues that have challenged their commercialization in the United States? Mostly it relates to the
reality that the laboratory-measured functionalities are performed under pristine
conditions—which never occur in food. The most
consequential problem is that microorganisms do
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pg
[PACKAGING]
Activity Today in Active Packaging continued...
UltraZapXtendaPak applies active packaging principles in order to
generate synergistic natural antimicrobial effects in pads used to
help prevent adverse microbiological changes in fresh meat or
poultry products. Photo courtesy of Paper Pak Industries
not conveniently reside on smooth
food surfaces; they are found in deep
recesses of food, not reached by
most of the antimicrobials or their
derivatives. Thus, although these
compounds are effective in vitro,
when it comes to in vivo —whoops!
And even if a safe, wholly functional
system is developed, how effective
can it be to control the entire spectrum of microorganisms extant on or
in food? We can forecast antimicrobial active packaging serving to
complement or extend a base preservation system sooner rather than
later.
Moisture Controllers
Virtually the first commercial active
packaging was silica gel in a porous
sachet or mini-canister placed in a
hermetically sealed pouch or jar to
remove residual water and/or water
vapor. Today, these are hardly
uncommon for hermetically packaged dry drugs with many months or
even years of shelf life. Emerging
from the shadows of laboratories and
pilot plants are a number of enhanced
moisture controllers that carry the
concept into newer contexts.
CSP Technologies (www.
csptechnologies.com) has developed
three-phase polymer technologies in
which a barrier layer and a
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channeled layer are co-extruded into
a canister-shaped structure. Within
the channeled layer are desiccant
particles open to the environmental
gas within the closed container containing dry product. Moisture is
withdrawn from the package interior
before closing, and the dispersed
internal desiccant removes any
residual water vapor. The package
may later be opened by a consumer
to remove one unit of the contents. If
the package is closed tightly by the
consumer, the active desiccant in
the container wall can remove any
moisture that entered during the
brief opening period.
Astute food packaging technologists have extended this multi-phase
plastic concept to food packaging by
incorporation into the plastic package channels of antimicrobials for
the control of Listeria on processed
meat surfaces. In the same manner
as in other contexts, CSP Technologies has incorporated activated
carbon odor controllers, aroma emitters, and persistent oxygen
scavengers.
Shelf life of foods high in water
content such as fresh or processed
meat or bakery goods may be
extended by retarding water loss at
high relative humidities. Moisture
variation from temperature fluctuations in distribution may be
regulated by absorbing or desorbing
moisture to stabilize the amount to
pre-established levels, in effect
functioning as a buffer to supply or
remove. Multisorb Technologies
(www.multisorb.com) has
addressed this issue with sachet
contents engineered for relative
humidities in the 60–90% range.
Oxygen Controllers
Food packaging scientists have
been probing means to remove as
much oxygen as possible from the
interior and exterior of food products and to maintain reduced
oxygen conditions. While reduced
oxygen in past years meant dropping
the levels to a single-digit percentage, that low amount has been
demonstrated to be adverse to sensory quality in a wide variety of food
products such as beer, processed
meats, prepared meals, and dehydrated foods. Thus, the objective
has been to decrease oxygen to as
low as possible and to maintain
those levels applying barrier packaging plus active packaging.
Multisorb Technologies’ and
Mitsubishi Gas Chemical’s classic
ferrous oxide sachets and labels are
the standards but as decreased oxygen levels are sought, both
companies and others have developed more-responsive activities.
Cryovac is incorporating benzyl
acrylate into plastic package films
for processed meats; Grace is incorporating ascorbates into bottle
closures; Bericap has sulfur dioxide
in bottle closure liners; and makers
of polyester beer bottles have layered in scavengers to retard
passage of air through the walls. It is
a rising tide that recognizes that
parts per million of oxygen in the
contained food significantly reduce
shelf life. This has led to systems
that integrate removal and barrier
with active packaging.
Final Thoughts
Any discussion of active packaging
senses increased activity on the
developmental and commercial
scenes: self-heating in new solid
state formats that might actually
function in a controlled manner; widgets that appear in Guinness cans if
not record books; rosemary as the
answer to meat preservation issues;
and micro oxygen to achieve the ultimate goal of total practical control
over biochemical deterioration. So
although active packaging is but a
minor factor in food packaging today,
its continued permeation into our
food packaging is assured to achieve
an objective of much prolonged
quality and nutritional retention. FT
Aaron L. Brody, Ph.D., Contributing
Editor • President and CEO,
Packaging/Brody Inc., Duluth, Ga.,
and Adjunct Professor, University of
Georgia • [email protected]