© ORCA Education Limited 2005 Preserving Food ^*#{}#*^ SHOW tom, tom.acs, 40, 68 PLAY Acknowledge PLAY Explain SAY Hello | Hi | Good Day, SAY I am Tom. | My name is Tom. | I am the VT character Tom. SAY ^PAUSE=300^ I will provide some extra guidance and information ^PAUSE=300^ during this {prez entation=presentation.} | I will help with some extra information during this {prez entation=presentation.} ^PAUSE=800^ SAY My colleagues may also give some help. | There are other characters who may also be called on to give some guidance. | Some of my colleagues may also help out. ^PAUSE=1300^ PLAY Explain2 SAY Today we will look at how we preserve food. ^PAUSE=1300^ PLAY Blink SAY We will also consider how preserving ^EMPHASIS^changes the food.^PAUSE=1300^ PLAY HandsOnHips SAY In fact some of our best foods, ^PAUSE=300^ like smoked salmon^PAUSE=300^ have their special taste just because of the way they were preserved.^PAUSE=1300^ SAY Before we start just a few technical notes. ^PAUSE=300^ SAY While we are talking ^PAUSE=300^ you can ^EMPHASIS^Suspend us ^PAUSE=300^ or ask us to ^EMPHASIS^Resume ^PAUSE=300^ by right clicking on us and then choosing ^PAUSE=300^ Suspend ^PAUSE=300^ or Resume ^PAUSE=300^ from the menu.^PAUSE=1300^ PLAY Decline SAY If you choose ^EMPHASIS^Hide ^PAUSE=300^ we will stop completely! ^PAUSE=1300^ PLAY Sad SAY ^PAUSE=600^ PLAY Alert SAY Oh yes! ^PAUSE=300^ SAY There are some terms that may be new to you. SAY If you want to see them before the {prez entation=presentation} click on the New Words button. PLAY Point225 SAY ^PAUSE=800^ PLAY Announce2 SAY These keywords in the text are red and underlined, ^PAUSE=300^ if you click on a highlighted word you will see a ^EMPHASIS^short definition PLAY GestureDown SAY at the bottom of the page. ^PAUSE=800^ END New Words © ORCA Education Limited 2005

Scientific Principles Food preservation stops food going bad. It prevents or delays spoilage and stops the growth of harmful micro-organisms such as bacteria, yeasts and moulds. To survive and spread, micro-organisms need warmth, food, moisture and time to grow. Preservation changes the environment of the food and therefore prevents the growth of micro-organisms. Enzymes in food also cause deterioration and must be destroyed. ^*#{}#*^ SHOW tom, tom.acs, 42, 68 PLAY Wave PLAY LookLeft PLAY Surprised SAY There is ^EMPHASIS^definitely a smell of ^EMPHASIS^spoilage around here. ^PAUSE=1300^ PLAY Decline PLAY Explain SAY Micro-organisms are usually associated with food spoilage^PAUSE=300^ but they can ^EMPHASIS^also be beneficial. ^PAUSE=1300^ PLAY Acknowledge SAY Micro-organisms are used safely in the manufacture of ^EMPHASIS^many different foods such as yoghurt, ^PAUSE=300^ cheese, ^PAUSE=200^ wine, ^PAUSE=150^ bread ^PAUSE=100^ and Quorn. ^PAUSE=1300^ PLAY Announce2 SAY Did you know that lactic acid bacteria cultures are used to make cheese and yoghurt as these are not harmful? ^PAUSE=1300^ PLAY Alert SAY Moulds are also injected into cheese to produce blue-veined cheeses^PAUSE=300^ like Danish Blue and Stilton. ^PAUSE=1300^ SAY Then of course yeast is essential in the manufacture of bread and alcoholic drinks. ^PAUSE=1300^ SAY While Quorn is made by using micro-organisms in a fermentation process similar to making yoghurt ^PAUSE=200^ or beer.^PAUSE=1300^ PLAY Think END In what foods do we use micro-organisms? *

Why Preserve? Throughout history people have found ways to preserve food, like smoking or sun-drying this fish. Ideally we would eat food fresh. This is not possible as we need food to last for when it is not available fresh. Preserving food has also improved food safety. Preservation lets us buy or collect food when it is plentiful or cheap and eat it out of season. *

Preservation Methods To preserve food like this fruit we need to remove the conditions micro-organisms need to survive and grow. Our choices are: to use high or low temperatures reduce moisture (dehydration) add chemicals to change the acid/alkaline conditions or remove water remove air to deprive micro-organisms of oxygen and prevent further re-entry by sealing it from the outside world irradiation using new technology. *

Are tinned foods different to fresh foods?* The Use of Heat Most bacteria, yeasts, moulds and enzymes are destroyed by heating to 100ºc. The methods include: Canning and bottling where heat sterilization destroys micro-organisms and enzymes and seals to prevent contamination. Pasteurisation which heats food to 72ºc and destroys many but not all micro-organisms. Ultra heat treatment (UHT) where high temperatures are used to destroy all bacteria e.g milk and fruit juices. ^*#{}#*^ SHOW tom, tom.acs, 42, 68 PLAY Wave PLAY Announce2 SAY Heat is a very popular way to preserve food, ^PAUSE=300^ while canning is one of the most widely used methods. ^PAUSE=1300^ PLAY GestureLeft SAY Food that has been heated then sealed in cans or jars can be kept for several years^PAUSE=300^ but once opened it must be treated as fresh food. ^PAUSE=1300^ PLAY HandsOnHips SAY Where I come from in Western Canada we preserve a ^EMPHASIS^lot of meat and salmon as well as ^EMPHASIS^lovely {Okanargan=Okanagan} peaches. ^PAUSE=1300^ PLAY Point45 SAY These go in bottles ^EMPHASIS^or jars but we always call this canning. ^PAUSE=1300^ PLAY Acknowledge SAY By doing this we catch salmon when they are running in the summer ^PAUSE=300^ and then they last all year. PLAY Decline SAY However, the process ^EMPHASIS^does alter the characteristics of the food. ^PAUSE=1300^ PLAY Surprised SAY Canned salmon is nothing like a fresh Coho straight out of the Pacific! ^PAUSE=1300^ PLAY Explain SAY {Its=It’s} like tinned peas having a completely different taste to fresh. ^PAUSE=1300^ SAY Heat treatment by pasteurisation extends shelf life, makes the food safer to eat and is used for milk, ^PAUSE=200^ cream, ^PAUSE=200^ orange juice^PAUSE=200^ and beer. ^PAUSE=1300^ PLAY Think END Are tinned foods different to fresh foods?*

The Use of Low Temperature Low temperatures remove warmth and moisture that micro-organisms need for growth. Food can be frozen or chilled. Freezing stops the growth of micro-organisms, slows down enzyme activity and removes moisture by changing water to ice crystals. Chilling food slows down the rate at which micro-organisms multiply and also slows down enzyme activity. Many prepared foods are cook-freeze or cook-chill where they are cooked and then frozen or quickly chilled. ^*#{}#*^ SHOW peedy, peedy.acs, 42, 68 PLAY Wave PLAY GetAttention SAY Why do they always use ^EMPHASIS^me when {its=it’s} hot, ^PAUSE=300^ cold ^PAUSE=300^ or dangerous? ^EMPHASIS^ PLAY Decline PLAY Uncertain SAY OK ^PAUSE=300^ frozen food. ^PAUSE=1300^ PLAY Explain SAY Did you know frozen food is sometimes ^EMPHASIS^more nutritious than fresh food. ^PAUSE=300^ Especially if like peas, they are frozen within ^PAUSE=300^ hours of being harvested? ^EMPHASIS^ PLAY DontRecognize SAY Amazing I learn so much do this job! ^PAUSE=1300^ SAY Manufacturers use several methods to freeze food quickly today^PAUSE=300^ such as blast freezing ^PAUSE=300^ or immersion freezing^PAUSE=300^ so that your frozen raspberries are perfect when defrosted! ^PAUSE=1300^ PLAY Alert SAY But ^EMPHASIS^apparently ^PAUSE=300^ some foods need to be frozen ^EMPHASIS^very quickly ^PAUSE=300^ as slow freezing will produce large ice crystals that will break down the cell walls in the food ^PAUSE=300^ and you will end up with a mushy mess. ^PAUSE=1300^ PLAY Suggest SAY ^PAUSE=300^ Strawberries, ^PAUSE=600^ I remember when we first got a freezer it came packed with frozen ^EMPHASIS^food. ^PAUSE=1300^ SAY I went straight for the strawberries, ^PAUSE=300^ big disappointment, ^PAUSE=300^ red mush, ^PAUSE=300^ SAY Missed a chance there I could have invented the Slush Puppy. ^PAUSE=1300^ END

Drying Drying or dehydration removes the moisture micro-organisms need for growth and reproduction. This is a very old method of preservation where fruit, vegetables, fish and meat would be sun-dried or oven dried. Today, mechanical methods used are: spray drying for liquids such as milk hot air beds for drying solid food such as meat and pulses. ^*#{}#*^ SHOW tom, tom.acs, 28, 68 PLAY Wave PLAY Announce2 SAY When you have a cup of instant coffee, ^PAUSE=300^ you may well be drinking a product that has been through the {pro-cess=process} of ^EMPHASIS^accelerated freeze drying. ^PAUSE=1300^ PLAY Explain SAY This method of drying food is very good as there is ^EMPHASIS^little damage to the food product^PAUSE=300^ and reconstitution is also usually good. ^PAUSE=1300^ PLAY Acknowledge SAY They use the same method for mashed potato^PAUSE=300^ and many instant meals. ^PAUSE=1300^ PLAY Explain2 SAY In fact many different foods can be dried including milk, ^PAUSE=300^ fish, ^PAUSE=200^ meat, ^PAUSE=200^ vegetables, ^PAUSE=200^ pulses, ^PAUSE=150^ soups ^PAUSE=150^ and herbs. ^PAUSE=1300^ PLAY Think PLAY HandsOnHips SAY You know the {flavor=flavour} and texture is sometimes changed dramatically, ^PAUSE=300^ for instance, grapes are dried to become raisins and {sultarnas=sultanas,} while dried plums make prunes. ^PAUSE=1300^ PLAY Confused PLAY Explain SAY Dried food is often a concentrated source of nutrients although dried fruits ^PAUSE=300^ and vegetables lose their {vit amin=vitamin} C. ^PAUSE=1300^ END This freeze dryer freezes food quickly then the tiny ice crystals are removed by turning them to steam by heat in a vacuum.

Apart from the use of sugar what other ways is the jam preserved? * Chemical Methods Vinegar, salt, sugar and wood smoke have been used for many centuries as preservatives. Vinegar (acetic acid) is used in pickling, the strong acid solution prevents the growth of micro-organisms. Salt (sodium chloride) is used for meat and fish in a solution (brine) or to coat the food. It reduces the moisture content of the food. Sugar is used in jams, canning and dried fruit. In high concentration (60% for jams) it prevents bacteria from growing. Other chemical methods include the addition of antioxidants, sulphur dioxide and nitrites. ^*#{}#*^ SHOW tom, tom.acs, 54, 68 PLAY Wave PLAY GestureRight SAY When you open a jar of strawberry jam a vacuum seal is broken. ^PAUSE=1300^ PLAY Point45 SAY Sometimes a part of the lid will pop-up to show the vacuum seal has been broken.^PAUSE=1300^ PLAY Explain SAY This is part of the preservation process.^PAUSE=1300^ PLAY Explain2 SAY The jam has been bottled while still hot.^PAUSE=1300^ PLAY Explain3 SAY The heat has sterilized the jam ^PAUSE=200^ killing enzymes and micro-organisms.^PAUSE=1300^ SAY Once the jam is sealed it is safe until opened. ^PAUSE=1300^ PLAY Think END Apart from the use of sugar what other ways is the jam preserved? *

Removal of Air Canning and bottling use air removal to preserve as well as sterilise. Removal of air is also used in: Vacuum packing where all air is removed from the package. Food is kept in anaerobic conditions (no oxygen) delaying the growth of micro-organisms. Modified atmospheric packaging where most of the oxygen is replaced with carbon dioxide and nitrogen. Either method is often used to extend the shelf life of meats, fish, bacon and cheese. ^*#{}#*^ SHOW tom, tom.acs, 49, 68 PLAY Wave PLAY PointRight SAY Crisps and salad vegetables are examples of ^EMPHASIS^modified atmosphere packaging. ^PAUSE=1300^ PLAY Explain2 SAY Vacuum packing and modified atmospheric packing extend the shelf life of food as it delays the growth of micro-organisms. ^PAUSE=1300^ PLAY Explain SAY They are packed in sealed plastic film and must be stored in a cool place. ^PAUSE=1300^ SAY Some foods ^PAUSE=300^ like bacon ^PAUSE=300^ also have chemical preservatives such as sodium nitrite added to them so they can keep longer. ^PAUSE=1300^ PLAY HandsOnHips SAY The food looks, ^PAUSE=300^ smells ^PAUSE=200^ and tastes just like fresh food. ^PAUSE=1300^ PLAY Think END What other example might you often eat that use modified atmospheric packaging. *

Irradiation Irradiation is the process of passing X rays from radioactive or electron beams through food. It prevents spoilage by destroying micro-organisms. The energy similar to ultraviolet light does not make the food radioactive but irradiated food must be clearly labelled. The purpose of irradiation is; stop vegetables from sprouting destroy parasites in meat e.g. pork delay ripening of fruit e.g. mangoes and bananas allow longer storage e.g. shellfish and strawberries destroy insects that may damage cereals, rice, etc. *

Strawberries There are several ways to preserve any one kind of food. Strawberries can be preserved by: canning in sugar syrup or fruit juice jamming freezing chilling irradiation. Some methods will retain the qualities of the fresh strawberry in flavour, texture, colour, appearance and nutritional value, while others will not.*

Changes to Food How would the characteristics and nutritional value of food like this be changed by preservation? Irradiation of the vegetables will lead to loss of vitamins A,C,E and K. If the fruit or maize are canned the texture and appearance will change but the nutritional value will remain. Drying the apple will concentrate flavour, reduce size and weight and may increase sugar or salt content. Jamming will add flavour and energy value to the strawberries. Sterilisation would change the colour and taste of the milk. *

Some words or terms to learn Vocabulary Some words or terms to learn spoilage preservation enzymes irradiation pasteurisation antioxidants shelf life parasites micro-organisms dehydration sterilization UHT cook freeze cook chilled freeze drying pickling vacuum packing modified atmospheric packaging. *

The Task You can enter here a task for your students.

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