January/February 2021 - 13

PRE- PACKAGED SALADS
PRODUCTION LINE
The lettuce journey
WHAT IT TAKES TO KEEP LEAFY
GREENS HEALTHY AND FRESH
FROM FARM TO FORK
By Melanie Epp
Contributing Writer
IT MIGHT NOT SEEM that impressive today, but the fact
that fresh leafy greens are available all across America at
any time of year is pretty darned remarkable. Considering
that California and Arizona produce more than 90% of U.S.
lettuce, if you live anywhere east of
these two states the leafy greens on
your plate have travelled a long way
to get there.
So how is it that they look as if
they were harvested from a nearby
garden just this morning? The short
answer is cooperations and the right
technology: Equilibrium Modified
Atmosphere Packaging or EMAP.
Equilibrium modified atmosphere
odors, and results in product deterioration. On the other
hand, too much carbon dioxide can damage some products.
Nitrogen itself has no effect on the food product.
EMAP works best when the right packaging material is
used and properly sealed to prevent leaks. Permeability
and breathability are important qualities in packaging,
especially for leafy greens.
" If the products are sealed in an airtight package, oxygen
will soon become depleted and undesirable anaerobic
conditions could develop, " Bell explained. " On the other
hand, if the material is too porous, the modified atmosphere
will escape and no benefit will be derived. "
The target is to reach the desired
range by verifying, controlling and
monitoring the environment inside
the package. Correct EMA can extend
shelf life up to 100%, said Bell.
Witt Gas showcased several new
 Sormac's Pulstar washer.
packaging is technology that slows
respiration and extends the shelf life
of fresh produce. Unlike most food products, fresh fruits and
vegetables continue to " breathe " or respire after they have been
harvested. Through this process, produce consumes oxygen,
creating carbon dioxide and water vapor in the process.
The primary purpose of EMAP is to keep packaged products
fresh for as long as possible without harming product quality,
including taste, texture and appearance, said David Bell,
President of Witt Gas Controls. Witt Gas Controls manufactures
equipment for gas mixing and analysis, and leak detection.
" In general, the rate of respiration can be controlled by
having lower levels of oxygen - usually less than 5% - in
the packaging atmosphere, and increased levels of carbon
dioxide, normally around 5-15%, with the balance gas being
nitrogen, " said Bell.
This is not as simple as it sounds. To meet and continue to
control the gas mix in the package, the process exchanges
" air " made up of 79% nitrogen and 21% oxygen. If there's
too little oxygen in the packaging atmosphere, anaerobic
respiration occurs. This process causes unwanted tastes and
pieces of equipment suitable for
modified atmosphere packaging at
Fruit Logistica 2020. Packagers of
leafy greens and other fresh produce
may want to check out Oxybeam, a
new non-destructive gas analyzer that
uses laser technology to determine
the residual oxygen in packaged food. The company also
considers Leak-Master Pro 2 an essential component for
quality assurance. The package leak detector is based on
CO2 technology.
But like Bell said, the success of MAP technology is also
dependent on packaging. Companies like Coveris produce
films suitable for products that require gas flushing, as well
as products that don't.
Work has been done to better understand optimal head
space for leafy greens and how fast different leafy greens
respire, said Eric Duncan, Head of Food Science, Coveris.
Leafy greens respire slower than other produce, which
means they require assistance in reaching the optimum
headspace, explained Duncan. This includes a fine balance
of proper packaging permeability and active gas flushing.
In dark leafy greens like spinach, for instance, natural
respiration leads to yellowing of the leaves, which leads
to food waste. In pale-colored lettuces like iceberg and
Romaine, too much oxygen can cause the greens to turn pink.
PRODUCE PROCESS ING
13
January/February 2021

Table of Contents for the Digital Edition of January/February 2021
