Aims and objectives.
• Aim
– To provide an overview of the major food manufacturing processes.
– Objectives
– Following this lecture you should be able to:
• Explain the role of cooking in food safety.
• Explain the role of refrigeration and freezing in food safety.
• Describe...
Aims and objectives.
• Aim
– To provide an overview of the major food manufacturing processes.
– Objectives
– Following this lecture you should be able to:
• Explain the role of cooking in food safety.
• Explain the role of refrigeration and freezing in food safety.
• Describe the processes involved in pasteurisation and canning.
• Describe catering systems including cook – chill, cook – freeze
Heating- high temp to kill microorganisms to kill pathogens or food spoilage organisms.
Cooking- boiling or cooking in oven.
Pasteurization- a type of this is Ultra high temperature (UHT).
Appertisation- canning – using heat.
Low temperatures to prevent the growth of food microorganisms. Pathogens or spoilage
food microorganism.
Reduce temperature and make environment less optimum for food microorganisms to
grow.
Freeze.
Cook-chill- >
Cook-freeze->
Eliminates potential risk of food pathogens growing.
Cooking.
• Mainly for taste & safety
– Reduce / eliminate vegetative pathogens
• No effect on spores or toxins
• Internal temperatures
– 70°C / 2mins
– Alternative time and temperature combinations:
, • 60°C for 45 minutes
• 80°C for 6 seconds
• Cooking food makes it easier to digest and safer.
• Reduce number of microorganisms in the food that you are going to consume.
• Eliminate vegetative pathogens such as salmonella. And food spoilage organisms.
• Spores can be present in food. And heat that we use in traditional cooking don’t
reach the levels that can eliminate spores.
• Sometimes this is not a problem if things are going to be consumed soon.
• This has a similar effect on toxins aswell, there are certain organsism that produce
toxins that are heat stable. So even if you heat that food afterwards, after it has been
stored inadequately this does not eliminate those toxins and you can become unwell
quickly. And can food poisoning as a result of those toxins.
• Advice from food standards agency is 70 degrees for the tempurtaure for 2 minuites
for the internal temperature. This means that we can eliminate the pathogens that
we are concerned about.
• We can slightly manipulate this by lowering the tempurtaure.
• However, this would mean that it is less effective, and we have to increase the time
that the pathogen is exposed to that tempurtaure.
• If we lower the temperature to 60 degrees, we then have to keep it at this
tempurtaure for 45 degrees.
• On the other hand, if we increase the temperature to 80 degrees, this decreases the
time that you need the tempurature to expose the pathogens to eliminate them.
Only 6 seconds.
• Cooking a joint of meat, although you are going down to lower tempurtaures with
those, we need to make sure that we are getting rid of the important food borne
pathogens in those.
• Decimal reduction time- pathogens and food borne bacteria die in a predictable way.
So we expose them to a certain temperature for a certain amount of time. We can
see this and we can put it on a logarithmic scale. We can see this reduction as a
linear reduction. We can use this information to understand a particular
tempurtaure and how long we need to expose those microorganisms in a particular
environment to achieve a 1-log reduction. So this means a 90% reduction in
microorganisms that are present.
• We do not necessarily know the starting number of microorganisms but we are using
this decimal reduction time and we can understand that at a certain temperature the
amount of time that is required to reduce by 1-log, so if we want to reduce by a
certain number of logs, 90% is one log, 99% is 2 log and 99.3 which is 3 logs. We can
reduce the number to the point where it is safe.
• This is a manipulation where we change the temperature, and we will also need to
change the time. This is so that we achieve the same elimination of pathogens.
Chilling down hot food.
Temperature controlled
Hot holding- above 63°C
Outside of temperature controlled environment
Hot food:
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