Food Protection Trends - July/August 2018 - 259

vegetables, however, the objectives of pasteurization also
include inactivation of softening enzymes such as pectinases
(14, 17). Spore-forming organisms are not killed by pasteurization temperatures, although spores are prevented from
germination in fermented or acidified vegetables if pH values
remain at or below pH 4.6 (15).
The vegetative pathogenic bacteria of concern in acidified
vegetables include Escherichia coli O157:H7, Salmonella
enterica and Listeria monocytogenes (2). A 5-log reduction
(CFU/ml or g) standard for vegetative pathogens is used for
FDA process filings. FDA process filing forms require loglinear model parameters for thermal processes, D (decimal
log reduction times), F (processing time at a reference
temperature), and z (change in D value with temperature)
values (1, 4). These parameters have been determined for
acidified vegetable products with pH values at or below
4.1 (5), the pH values of most acidified products, and for
products at or below pH 4.6 (4). Products with a pH above
4.6 are considered low-acid foods and were not considered in
these studies. Acidified cucumber juice or acidified cucumber
products were used for these studies, but these studies may
be applicable to a variety of brined acidified vegetables,
because cucumbers have no known antimicrobial properties
that would contribute to acid and heat killing. The use of
cucumber juice or cucumbers in brine for thermal processing
studies can therefore represent a 'worst case' scenario, and
results of studies with cucumber brines have been used to
determine safety for a variety of acidic and acidified food
products (F. Arritt, personal communication).
Tunnel pasteurizers are typically used for thermal
processing of acidified cucumber pickles on a continuous
belt. A hot water bath apparatus may also be used for batch
processing. Sliced, acidified cucumbers are packed into
jars with a cover liquor typically containing acetic acid,
flavored oils, spices, and other ingredients. Glass or plastic
jars are then capped and subjected to heating. The required
time-temperature conditions must be achieved for the
cold spot within the jar (3) to assure safety, and models
for determining if a desired F value has been met in tunnel
pasteurizers have been developed (7). The heat penetration
kinetics for cucumbers and jars have been previously
determined (8, 16, 18). Tunnel pasteurizers typically use
a steam or water spray to sequentially heat and cool jars in
stages, to prevent cracking glass jars as they are transported
through the pasteurizer on a belt.
To reduce the energy costs and use of water associated
with a tunnel pasteurizer, we investigated a hot fill method for
products containing acidified cucumber spears in jars. This
method may reduce overheating the exterior of the jars by
applying heat directly to the vegetable material, as previously
proposed by Morawicki and Schmalko (18). We proposed
that repeated hot fill thermal processes may deliver sufficient
heat to achieve established pasteurization time temperature
treatments for cucumber spear acidified products. Processing

equipment for using the in-jar method with cucumber spears
will likely require only off-the-shelf technology for filling
and handling jars and may offer the advantage of reduced
water and energy use compared with a tunnel pasteurizer.
We report here the brine temperatures, filling regimen, and
holding times needed for a hot fill process to achieve thermal
processing parameters similar with a tunnel pasteurizer
process for cucumber spear products.
MATERIALS AND METHODS
Cucumber spears and jars
Fresh size 3A pickling cucumbers (3.8 cm to 4.4 cm
in diameter) were obtained from a commercial source.
Cucumbers free of obvious physical damage were washed prior
to use, to remove dirt or other debris. Cucumbers were sliced
longitudinally into four sections (spears) and were preheated
to various initial temperatures (20°C, 40°C, and 60°C) in
a water bath (Fig. 1A). Approximately 10 spears were hand
packed into 0.7 liter (24 oz) glass pickle jars obtained from a
commercial manufacturer. Jars were prepared with and without
a 5 cm thick insulation material (Corning "Pink" fiberglass
R-6.7, Owens Corning Insulating Systems, LLC, Toledo OH)
cut to surround the jars and held in place with tape (Fig. 1B).
One large cucumber spear was placed in the center of the jar,
while another large spear was located in the outside perimeter
with geometry as shown (Fig. 2). Smaller spears were tightly
packed in the jar to keep the larger spears in place.
Five holes were drilled on each metal lid pickle jar lid
(obtained from a commercial supplier) to provide access for
four type T thermocouples and a PVC tube (Nalgene, 3.2
mm internal diameter, #8000-0010, Nalge Nunc Intl. Corp.
Rochester, NY). After the lid was closed, two thermocouples
were inserted through the holes to reach approximately the
center of the two larger pickle spears (center and periphery).
The thermocouples were held in place with a silicon putty
(Fig. 1B), and the tubing used to fill and empty the jars was
inserted through a larger hole and extended to the bottom of
the jar. Two additional thermocouples were inserted into the
jars to record the temperature of the brine near the center of
the jar and at the periphery. A reversible peristaltic pump was
used to add and remove the hot brine solution (0.86% NaCl)
through the PVC tube at a flow rate of approximately 0.3
liter/min with 70°C, 80°C or 85°C brine. Experiments used
three repeated fills, for total processing times of 16 min to
45 min as indicated. The average values of pickle jar contents
were 10.0 +/- 0.9 spears, weighing 412.5 +/- 31.5 g, with jar
weights of 351.8 +/- 4.0 g, and brine weight of 268.3 +/- 42.3
g. Spears were made from cucumbers with a diameter value
of approximately 44 mm (size 3A cucumbers), typical of
commercial practice.
Heat transfer modeling
Heat transfer between the pickles and hot brine was
numerically evaluated with commercial software, COMSOL

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