1.3 Why is it necessary to preserve foods? - PowerPoint Presentation

Slide1

1.3 Why is it necessary to preserve foods? 1.4 Why are additives included in processed food?

Food ProcessingSlide2

What is food processing?‘Food processing means using techniques that changes the original form of the food – for example cooking, refining and adding flavours or colours…’

(

HEIA 2008)Slide3

Why process food? To extend the life of food

Processing can slow down or stop the growth of bacteria, moulds, yeast and the chemical reactions of enzymes that can cause deterioration.

To make the food safe

Foods contain potentially harmful microorganisms, which can cause food poisoning if left to grow.

Processing such as pasteurisation, heat and chilling can reduce microorganism growth. For example, milk is pasteurised .To increase the range of food availableAllow production of a variety of foodFor example, grinding peanuts into peanut butter and canning provides vegetables all year round. Slide4

Why process food? To save time preparing food at home

For example, a tomato based sauce saves the time needed to prepare vegetables and herbs to make the sauce.

To reduce shopping frequency

Stored for a longer period of time; thus, reducing the need to shop weekly.

To reduce the cost of foodOccasionally cheaper than fresh foodSlide5

What is food preservation?‘Food preservation means preparing food in a way that increases resistance to spoilage from decomposition or fermentation.’

(HEIA 2008

)

Food preservation ensures a continuous and plentiful supply of food.

The aim is to: ‘destroy organisms by heat or to maintain conditions that will render them inactive – cold, dryness or the use of chemicals that are unfavourable to the growth of the organisms.’ (Magee 2010)‘Prevent any fresh organisms reaching the food by sealing it immediately after treatment.’ (Magee 2010)Slide6

Food Preservation Techniques

Removal of Moisture

Bacteria

need water to live and most enzyme reactions occur in water.

Moisture is removed from food by:EvaporationDehydrationAdding SaltAdding Sugar Freezing (water is trapped within food cells)Freeze drying (Product is frozen and then water is removed)Slide7

Food Preservation Techniques Heat Treatment

Food can be preserved by heating to high temperatures for set times.

This kills some or all of the micro-organisms and deactivates enzymes

Methods include

:Boiling (100oC)Canning (121oC)

Pasteurising (72

o

C for 15-20seconds)

Ultra High Temperature (132

o

C for 1-3seconds)

Blanching

Heating food with steam or water to inactivate enzymes that may affect colour, flavour, texture or nutritional value. Slide8

Food Preservation Techniques Temperature ReductionFood

can be preserved by storing it below 4

o

CMethods include

:Chilling involves storing food between 0-4oC which slows down growth of micro-organisms.If the temperature is allowed to increase above 4oC microorganisms will multiplyFreezing

involves storing food below -18

o

C

which stops growth of micro-organisms and extends storage

time.Slide9

Food Preservation Techniques Reduced oxygen

Many bacteria are oxygen dependent and so packaging methods that exclude air will extend storage time

.

Methods include

:Controlled atmosphere packaging e.g. salad greensMAP (modified atmosphere packaging) including barrier, vacuum and gas packagingAntioxidants E.g. additives used to prevent oxidation Slide10

Food Preservation Techniques Acid and alcoholDifferent bacteria prefer different acidity levels.

Altering

the

environment to make it more acidic or alkaline will kill most micro-organisms

Methods include:Fermentation e.g. yoghurtPickling in vinegar e.g. pickled onionsNatural fruit juices are more acidicAcidulates

can be addedSlide11

Food Preservation Techniques Food Irradiation

‘During this

procedure the food is exposed to doses of ionising energy, or radiation. At low doses

, irradiation extends a product’s shelf life. At higher doses, this process kills insects, moulds

, bacteria and other potentially harmful micro-organisms.’ (Betterhealth 2012)The food does not become radioactive because it does not contact the energy source and the dose is low

.

This process delays ripening and kills bacteria, parasites and

insects

Any irradiated food must go through a strict safety assessment by FSANZ and must be labelled to show this.Slide12

Preservatives ‘Preservatives are natural or man-made chemicals that are added to foods to stop them from spoiling. We actually 'preserve' fresh foods ourselves every day, by storing foods in the fridge or freezer. Natural preservatives that can be added to foods include salt and sugar.’

Food preservatives work by preventing spoilage of foods by moulds, yeast and bacteria. Preservatives have an acidic nature that makes the organisms unable to grow in the food.

Sulfur

dioxide (220) in dried apricots and sodium nitrate (250) in salamiSlide13

Food Additives‘A food additive is a substance intentionally added to food to achieve one or more technological functions. Colours are added to improve or restore colour. For example, carotene is added to margarine to make it look more like butter.’

Food additives can

:

Improve flavours

Change texturesIncrease nutritional valueSweeten thickenIncrease shelf lifeImprove appearance of foodSlide14

Reasons For Using Food Additives

Additive

Function

Colours

Added to improve or restore colour. For example, Carotene.

Artificial Sweetening Substances

Used to replace sugar in ‘diet’ foods

increase overall sweetness.

For

example, Equal.

Food Acids

Help maintain a constant

acid level in food. For example, citric acid.

Antioxidants

Slow

down oxidation reactions that cause rancidity, colour changes and spoilage.

Vegetable gums and thickeners

Improve and stabilise texture.

Emulsifiers

To prevent fats from clogging together.

Anti-Caking Agents

Prevent products such as salt, icing sugar and milk from sticking together and becoming lumpy.

Mineral Salts

Enhance texture in products that may lose fat and fluids during processing.

Flavour Enhancers

Bring out the flavour of food.

For example, MSG

HEIA 2008, P165Slide15

Food AdditivesFSANZ ensures safe food by developing effective food standards for Australia and New Zealand.

Regulations

state ‘all additives used in food must be listed on the ingredients list on the food label. Food additives must be listed under their functional name followed by the additive’s specific name or code number in brackets.’

(HEIA 2008

)Slide16

Homework – Due Thursday W6

Describe the term ‘Additive’.

Refer to the following ingredients listed on a packet of savoury source:

Identify three food additive groups

represented

in the ingredients listed above.

For each food additive group

identified

suggest one reason for its use in the sauce.

Ingredients

Coconut Milk, Lemon Grass, Chilli, Garlic, Red Capsicum, Spices, Herbs, Vinegar, Vegetable Gum

(415), Saccharine (954), Vitamin - Ascorbic Acid (300), Flavour Enhancer (621), Water Added. Slide17

Homework – Due Thursday W6

State why the following two food additive groups are commonly added to some foods. For each group, give one example of the food in which it is used.

Antioxidants

Emulsifiers

State two legal requirements for identifying food additives on food labels.