1. Sanitation & Hygiene
Convection systems allow for detailed cleaning of the interior
and exterior of the retherm system. The interior of a convection
retherm system is a fully open cavity. This allows the foodservice
staff to power wash the interior and exterior of the units.
The rack system inside the unit is removable which allows for
hand washing of the complete system. There are no pod heating
elements that have to be removed by the technical services department
before the cleaning process can begin (as in conduction systems).
In a conduction system, if food over heats or boils over, food
will build up behind the food pods. Foodservice staff will not
be able to properly clean behind the pods thus creating a greater
sanitation, hygiene, and compliance risk issue with the foodservice
departments HACCP (Hazard Analysis Critical Control Points)
New conduction systems demand less removal requirements of
the pod heating systems. However, due to the electronics of
the system ( wires from the main panel to the heating pod ),
it is recommended that the pods be removed by maintenance technical
personnel only. This is to guarantee the safety of the individuals
that are properly sanitizing the conduction system.
2. Quality of Food
I encourage you to call people who use conduction or used to
use conduction systems. Ask them what happened to their customer
satisfaction scores after they implemented Convection in place
of the old conduction system they had prior. You will hear some
remarkable results. The entire convection system supports quality
– in everything it does – it reheats all types of
foods (breaded, fish, fries, baked desserts, toast), it does
not result in baked on food onto the dishware, it allows for
all types of dishware, most convection systems use a FLAT TRAY
which is homelike and allows for all foods to be easily moved
about on the tray without obtrusive ridges or holes.
3. Multiple Handling of Foods?
In convection systems, the food is placed cold onto a tray and
placed into a retherm cart where the food is reheated while
the cold food stays cold. When the retherm cycle ends, the food
tray is pulled out and given to the patient. That is the process.
In conduction systems, food is placed on the tray in specific
locations as each system has ‘spots’ to have foods
placed on the tray. The food must be specially plated due to
the conduction heating process. The tray is moved to the conduction
ovens. In some cases, the trays can be inserted into the oven
which will keep the foods cold that are to be cold while the
hot foods reheat…however, some systems require you to
transfer the foods from one hot retherm cart to the tray that
is being held cold. This is done with the use of a ‘shovel’.
This is true food manipulation, which is not the case with convection
single handling flat tray systems.
A common argument against convection retherm
systems is that the noise level emitted during rethermalization
is substantial when compared to conduction based systems. It
is true that convection based systems are noisier than conduction
systems because of the fan inside the convection unit. However,
the convection unit is well insulated and the noise emission
is well within the limits. The noise of a group of retherm units
is no louder than that emitted by one single fan inside a walk-in
5. Heat Distribution
Conduction systems use a pod and heating element system. The
stainless steel or aluminum plate has a heating element inside.
The element is energized from the incoming power supply, for
which the heating element then heats the pod. The pod then heats
the bottom of the entrée plate or soup bowl, which then
heats the food from the bottom to the top.
Convection systems use a heating element and a fan system to
gently distribute hot air through-out the entire cavity. This
allows for the heating of the complete surface area of all items
that are required to be rethermed.. This even distribution allows
for maximum efficiency and guarantees all foods are heated.
There are no ‘hot spots’ and trays are not discolored
at contact points. Today’s healthcare production facilities
require convection based cooking and chill equipment in order
to provide maximum food quality, taste and appearance. If food
is cooked using convection based heat, then it is prudent to
rethermalize it using the same process.
Conduction systems over a ten year period require greater maintenance
attention and costs than convection systems. General replacement
parts on the conduction equipment on average are the heating
pod systems. Estimated replacement value is approximately $
250.00 per pod.
Convection retherm systems require an estimated twenty minutes
of cost time per year for preventative maintenance measures.
During the following years preventative maintenance is estimated
at 30 minutes per retherm unit. General components that may
need to be replaced should the system fail are: fuses, consumable
items, and or warranty components, such as the main contactor
or run capacitors. In the long run, convection systems are easier
and low cost to maintain. You really need to consider life cycle
costs when evaluating convection versus conduction.
7. Worker Safety & Food Product
When rethermalization is completed on a conduction system a
foodservice staff member must check each heated item on every
tray with a sanitized food probe to ensure that each item has
reached the required safe set temperature. There is a labour
and time management cost associated with this process. Staff
must and are required to sanitize their product probe prior
to probing each food item. This is a mandatory requirement to
ensure that a product previously probed for one patient does
to not come in contact with other food items for another patient
that may have allergies. To avoid this process, many foodservices
have adopted a specific process with conduction systems. Staff
place there hands on the under-section of the heating pod to
test to make sure that the heating pods are operating as required.
Staff can complete this procedure without the use of protective
gloves. They do this to ensure that they can accurately test
the pods, and that the pods were working through the complete
retherm process. This procedure can result in burns and bending
injuries, which in turn, can result in lost time and a workers
safety insurance claim. Claims can be estimated to cost the
foodservices department as much as two and half times the individual
claimants salary to the hospital.
In addition the aforementioned, you should review the ergonomics
of a cart system before you make a choice. You may find that
the conduction systems are extremely heavy compared to convection
systems. And, if you find the reverse, then we encourage you
to review the fabrication of the conduction cart as many manufacturers
decrease the durability of a cart to loose weight.
8. Equipment Failure?
Some suggest that when a convection system ‘goes down
or out of service’ the entire set of trays are at risk
of not getting heated. There is no argument to this. The same
can be said for a conduction system as all the trays would be
compromised as well if the cart went down. The real issue is
that when something goes wrong in a conduction system how are
you assured you know ? One pod may not work and how do you know
that it has ‘gone down’. You only truly find out
after the retherm cycle is finished and you find a cold food
tray. In a convection system, if the entire cart goes down,
you will know it and corrective action can be taken immediately.
If the cart goes down for any reason, another cart can be used.
For what it is worth, cart failure that impacts meal service
to a point of complete failure to supply a meal is extremely
rare. In a convection system for example, there is one fan and
one heating coil….not 20 pods and 20 wires.
Speciality china should be utilized when operating a conduction
system. Flat based bottom china provides a better transfer of
the heat from the heating pod to the bottom of the entrée
plate or soup/cereal bowl. In some systems, heat may be transferred
from the heating pod to the patient tray and from the patient
tray to the bottom of the individual china pieces. Single tray
conduction retherm systems have experienced major problems with
tray warping and the break down of the plastic material used
in the composition of the tray. Trays become discolored and
unattractive. Replacement costs are high and ongoing. In some
cases, operators using conduction systems have noted patient
complaints about odors coming from trays and in one case the
odor caused a patient to become extremely ill. The plastic odor
being expelled from the trays was being absorbed by the patient’s
food, the odor was the main contributing factor to the patient
In conduction systems, special china must also be used. Flat-bottomed
china is required so that heat transfer can take place effectively.
Flat china is often heavier than other china and thus the weight
of the cart can become an ergonomic issue to the occupational
health and safety department.
Conduction systems often have ridges on the trays, thus a
flat tray is not possible. The tray (in many cases) must be
inserted into the retherm cart the same exact way each time.
There is no opportunity to reverse the tray, thus one side will
always be exposed to heat. This will discolor the tray over
time and will shorten the usefulness of the tray (i.e. life
Convection allows the foodservice department the ability to
use china, high heat plastic, oven paper and foil based products
from a wide variety of manufactures. Foodservices can also add
a tray mat to increase the appearance of a patient tray to allow
for a home style appearance. Many convection systems have a
tray that does not have to fit a special way and thus the life
expectancy of the tray is much longer.
Menu styles and needs of the hospital’s patients are as
flexible as requirements of the production department’s
recipes. Production equipment for the cook chill kitchen is
based on the operation of convection ovens, convection combination
ovens and convection air Blast Chillers. The standardized method
of operation has been adopted by all cook chill facilities on
or before 1947. Kitchens continue to be designed based on this
principal. It allows the foodservice departments the ability
to produce and store a wide variety of menu items based on the
principal of completing the cook chill chain by utilizing convection
air retherm technology.
When conduction technology is adopted as the principal rethermalization,
special production procedures need to be adopted. Conduction
systems generally place a certain amount of condensation back
into the items to be rethermed. Therefore, produced items need
to be dryer in content to compensate for the weeping that will
occur in a conduction system. Special plating techniques must
also be adopted with conduction technology. Meats will require
gravy underneath them to retard the heating process. If this
procedure is not adopted meat gives the appearance and taste
of a dried out product. Boned items cannot be used (such as
chicken or pork) or care must taken not to allow the bone to
touch the plate. If the bone touches the plate, the heat is
transferred into pours of the bone and is not transferred to
meat of the chicken. Conduction systems cannot rethermalize
crispy items such as Chicken Fingers, Toast, French Fries, melting
cheese on a lasagne. Convection systems can retherm all food
groups and even bake off cookies and other desserts do the patient
receives a fully cooked and warm dessert.
In convection based systems, all forms of foods can be used
and no special plating instructions are truly required to make
sure the food is reheated.