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The following information is provided
courtesy of The Catering Equipment Suppliers Association.
Understanding Microwave Ovens
Microwave
ovens are a hugely important part of every professional kitchen.
As a standard microwave-only oven they can perform essential
functions such as safely re-heating frozen or chilled food,
which is at the heart of many menus in informal dining
restaurants and pubs or in room-service for hotels.
Where they get much more
versatile in when they become a combination microwave oven. The
combination is the addition of convection hot air and a grill.
This transforms a simple re-heating cabinet into a
multi-function cooking oven. Jacket potatoes can be softened
then crisped, pastry dishes can be reheated and crisped, in fact
almost all of the functions of a standard oven can be performed
in the combination microwave oven. The main limitation is of
load capacity and the absence of steam in a standard-size
microwave oven. Although it is possible to buy a combi-oven
which incorporates microwave energy.
A general
rule of thumb is that microwave only is for re-heating,
combination microwave ovens are for reheating and primary
cooking.
There is a
minority view among caterers that all microwave ovens are the
same, the only difference between commercial ovens and domestic
ovens being the power and price. This is completely untrue.
There are clear cooking, construction and food safety
differences between microwave ovens designed for domestic use
and those designed for the professional kitchen.
Domestic
microwave ovens are often low power, which means they will take
far longer to reheat, defrost or cook food than a commercial
oven. While domestic ovens have a power rating from 600 watts to
900 watts, commercial microwave ovens can be up to 2000 watts.
The term watts is a unit of measurement for the heating power of
a microwave oven.
The device
which produces the energy waves which heat food in a microwave
oven is called a magnetron. Domestic microwave ovens usually
just have a single magnetron while commercial microwave ovens
usually have two magnetrons which are built to a higher
specification, making them faster, more efficient and longer
lasting.
A commercial
build microwave oven is built to withstand hard use every day,
while a domestic is designed to be used just a couple of times a
day, which repeated use of a domestic microwave oven can lead to
a loss of power with the associated food safety risks.
Microwave
energy needs to be evenly spread around the oven cavity to
ensure that all parts of the food inside are safely heated.
Where chilled or frozen food is not thoroughly heated, harmful
bacteria within the food is unlikely to be killed, risking food
poisoning. Many domestic microwave ovens use simple turntables
to try to distribute the microwave heat, while commercial
microwave ovens have sophisticated heat mixing systems in the
oven cavity.
The casing
of most domestic microwave ovens is painted mild steel which
will chip, corrode and cause food safety hazards. Most
professional microwave oven have casings made with hard-wearing
stainless steel which is easy to keep clean and will not
corrode. Commercial microwave oven are likely to have far more
sophisticated cooking programmes, often push-button pre-sets, so
staff can reheat properly and easily every time. The oven cavity
size on a commercial microwave is usually based around the
gastronorm system, making it easier to accommodate industry
standard sized food dishes.
Most
commercial microwave ovens have a cavity space of ½ gastronorm,
but they are also available in 2/3 gastronorm and full-size
gastronorm.
Manufacturers group commercial microwaves into four power bands.
Light-duty -
The oven will have a power ranging between 900 watts and 1100
watts. This is suitable for use where demands are light, such as
a café, satellite kitchen or petrol filling station.
Medium-duty
– A power rating of 1100 to 1500 watts, proportionately more
robustly built than a light-duty oven and suitable for
restaurants where the microwave is only in occasional use, busy
cafes, pubs or leisure centres.
Heavy-duty –
Powered from 1500 to 1900 watts and the most popular power range
used in catering. Suitable for busy pubs, hotels, busy
restaurants or staff catering. Built to withstand hard and heavy
use.
Extra
heavy-duty
– these are usually where large quantities of food are needed to
be reheated quickly rather than just individual portions. They
can take up to a full gastronorm tray. While all other power
bands are connected to a 13amp socket, this very heavy duty oven
will need hard wiring into the mains.
While the
general rule is the high the wattage the faster the food will be
heated, much beyond 2000 watts and food risks being burned on
the outside before it is heated on the inside.
Look After It!
Microwaves
oven can become quite dirty with food debris during a service
and a full clean-down every day is essential to maintain food
hygiene. Cleaning materials should only be those recommended by
the manufacturer.
Regular
safety and maintenance checks in accordance with manufacturers’
instructions are vitally important with microwave ovens. Any
slight drop in power output and food will begin to be
incorrectly re-heated, disappointing customers and presenting a
food safety hazard.
Looking
after a microwave oven is not difficult and they are one of the
more reliable pieces of cooking equipment in the kitchen, but
not without some look-after rules. Regular and thorough cleaning
is the No. 1 rule of microwave ovens. The intense heat they put
into food inevitably leads to some food spatter around the oven
cavity.
If this is
not wiped out regularly, but left, it will bake on with the heat
of the microwave energy and give an even greater cleaning
problem.
Kitchen
staff using a microwave oven should be trained to wipe off any
spillage or spattering as soon as the food item has been taken
from the microwave. At the end of shift the microwave needs a
thorough wipe down with a detergent on a non-abrasive cloth,
then sanitising.
Non-abrasive
cloths are very important, as the internal coating on the cavity
of a microwave oven is tough, but not resistant to constant
scratching. If the internal cavity walls become scored or
damaged, then the repair might be so expensive that it will call
to question whether to repair or replace. Both questions would
not arise with careful use.
The exterior
casing of a commercial microwave oven is usually stainless
steel, but there will also be plastic or toughened glass used in
fascia panels and controls. The exterior can withstand a tougher
scrub, but if the oven exterior is regular cleaned at the end of
a shift there should be no need to.
Beyond
regular cleaning and careful cleaning, there is little to go
wrong with a commercial microwave oven. Repairs are usually
caused by operator miss-handling, either rough cleaning or
damage to door hinges and closures through constant slamming. A
microwave oven is like any item of kitchen equipment in that the
door will prematurely break down through slamming abuse. Staff
should be trained to know that a positive push closes the door
of a microwave oven just as effectively as a heavy slam.
It is easy
to think that the simplicity of operation of a microwave oven
means there is not the need for a high maintenance schedule as
there might on kitchen equipment using water and gas.
Professional microwave ovens are relatively low in maintenance
costs, but they must never be excluded from the regular
maintenance cycle. It only takes a service engineer a few
minutes to check for leakage of microwaves through door seals,
but it is a vital part of regular maintenance for staff safety
and efficient operation.
Take care
not to operate the oven with little or no food in it – this will
reduce the life of the magnetron which is the component that
produces the microwave energy.
In brief
Do
Clean
regularly, but gently
Avoid letting food debris burn
Have the oven regularly serviced
Train staff on the fire hazards
Allow for proper rear ventilation
Don’t
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