Hot Beverage Dispensing
Introduction
The acceptable temperature of an automatically dispensed drink is the result of a number of
factors, both mechanical and sensory. This document describes the basis of those temperatures
and some recommendations for operating hot drink machines.
Consumption
From the experience of satisfying vending machine users' expectations, g, it is accepted that
65ºC is considered by customers to be the minimum acceptable temperature for a hot drink.
However, consumers frequently wish to be able to collect a hot drink, take it to another area
(e.g. their workplace) and drink it over a period of time. In the workplace it is common practice
for consumers to collect a round of drinks from a machine and if a number are being dispensed,
the first will have cooled by a few degrees before the last is vended.
Thus consumers wish to be able to collect the drink sufficiently hot so that it is just sippable
when they get back to their desk. 70ºC is thus the lowest acceptable temperature for a drink to
be vended. Below this it becomes tepid too fast and of unacceptable quality to the consumer.
Similar conclusions were the result of a study at the University of California. A paper (See
reference1) published in the Journal of Sensory Studies records the preferences of some 225
people tasting black coffee and their expectations of the temperature of coffee purchased from
retail premises. The preferred drinking temperature was 72ºC which was also deemed to be the
typical temperature at which a cup of coffee would be provided in a coffee shop.
A recent case in the High Court has also considered the temperature at which coffee is provided.
In this case it was decided that McDonald’s were not negligent in serving coffee at between 75
and 90ºC because they had taken all possible precautions (reference 2) .
Dispensing Process
When drinks are dispensed, water will flow to through the drink preparation system. Cold water
will be delivered into the hot tank to replace the dispensed hot water when a level control point
is reached. The points of entry to and exit from the boiler are usually designed so that the
hottest water leaves the boiler. However, the temperature of the dispensed water may fall if the
frequency of dispensing is fast and the power of the heating element cannot heat the water fast
enough. There is usually a thermostat to set a minimum vending temperature so that the
machine will not vend if the temperature in the tank falls below the set point. This point is
usually around 72ºC.
The hot water generally cools during its passage from the hot tank, through the mixing system
and tubing to the dispense nozzle. The amount of cooling will depend on the nature of the
mixing system and the materials of which it is constructed, length of tubing, and ambient
conditions. Together these can alter the temperature by several degrees.
In practice the temperature of the drink could vary from 85º to 65ºC, the actual figure being
influenced by the type of machine, the rate of vending and the mode of action of the machine
thermostats.
Hot water tank or boiler
Water required for the preparation of hot drinks is heated and stored in a hot water tank. For
instant drinks the water is usually stored at 85º C. For fresh brew tea the temperature can be as
high as 97º C to provide the best conditions for quality infusion of the tea.
In each case the temperature will be controlled by a control device with an operating accuracy,
usually of 2º C. However, this does not mean that the temperature in the tank only varies by
this amount because the heating element does not necessarily switch on the moment the
temperature falls. In practice the range can be º C.
The temperature of the tank is maintained by a heater, usually of about 2.5kw capacity. The
power of the heating element is limited by the power available from the mains supply, with
allowance for other power consumption in the machine.
The tank is usually fitted with an over-temperature thermostat which acts as a fail safe and
switches off the power to the heating element if the water reaches boiling point.
Scalding
The NHS health guidance note (‘Safe’hot water and surface temperatures) provides a chart of
temperature and duration of exposure sufficient to cause burns in thin areas of skin and gives
maximum temperatures for hand washing and bathing water. The maximum temperature for
washbasin hot water, assuming that hands are to be washed under running hot water, is 41º C,
while baths are to be no hotter than 44ºC. It is recommended that the use of uncontrolled hot
water be subject to a risk assessment and that outlets where water temperature is unlimited are
clearly labelled with “very hot water” notices.
Recommendations
Industry experience identified in this document has resulted in a very low incidence of scalding
problems, in relation to the number of drinks vended. Where hot drinks are dispensed, there is
clearly a risk but equally the provision of drinks at a temperature low enough to ensure no risk is
both impractical in terms of machine design and in terms of consumer satisfaction. The case in
the High Court referred to earlier demonstrated that McDonald’s had carried out a thorough risk
assessment, had checked that their staff were trained, that their cups were adequate to carry the
hot liquid and were not prone to tip over. It is recommended that vending companies carry out
appropriate checks.
In order to minimise the risk, it is recommended that
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Warning stickers be applied to equipment alerting consumers to the fact that hot drinks are
hot.
The vending company ensures that the cups provided are sufficiently rigid at the temperature
of vending that they do not easily compress and allow liquid to get on to the hand of the
consumer.
Special vending cup trays, lids or sleeves are provided to consumers where appropriate.
References:
1. Pipatsattayanuwong S., Lee H.E., Lau S. and O’Mahony M.
Journal of Sensory Studies 2001 (16) 517-536
2. Sam Bogle and other v McDonald’s Restaurants Ltd. Before Field J, 25/3/2002