techniques to prevent food spoilage

7/25/2019 Techniques to Prevent Food Spoilage

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Food Biotechnology

Techniques to prevent

food spoilage


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p g

Micro-organism Growth

Reminder that optimal conditionsfor micro-organism growth are:

- warm (usually !-"#o$%

- good food supply- moist


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&ow can we preventfood going 'ad

To some e)tent we can stop or delay thespoilage of food*

Mainly this is done 'y stoppingdecomposers or micro'es getting to the

food or changing the conditions to slow oreliminate micro'e growth*

This is the 'asis of food preservation*


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&ow can we preventfood going 'ad

There are four main ways to preserve food:

Cold treatment:eg deep free+e, refrigeration*

Drying: eg dehydration

Heat treatment:eg sterilisation, &T (ultra

heat treatment%, 'ottling, canning,pasteurisation*

Chemical treatment:eg pic.ling, smo.ing,salting


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$old Treatment

Free+ing does not kill microbes, 'ut itstops them from multiplying and slowstheir action/ the colder it is the slowerthey get*

0s soon as the food thaws the micro'es(previously dormant% start up again andfood 'egins to go 'ad*


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Free+ing

Meat decays particularly quic.ly 'ecause thefree+ing process 'rea.s open the cells and themicro'es can invade quic.er*

1epending on the type of food and the free+ingtemperature food can 'e stored for up to a year*

Most free+ers operate at -2o$ or -34o$

Free+ing food is important these days fortransporting*


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Refrigeration

Refrigerating operates at 5ust a'ove free+ingtemperature*

6t slows 'acterial action down 'ut does notstop it*

Therefore food can only 'e stored in the fridge

for a few days*

Food should 'e defrosted in the fridge* Theoutside defrost 7rst, allowing 'acteria tomultiply while the inner part of the foodcontinues to defrost*


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Refrigeration


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1rying

Micro'es need moisture 8 they go

dormant in 'ad conditions*

9ven if spores land on dried foods

they cannot germinate if there is notmoisture*

1ried food lasts inde7nitely*


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1rytorage

$ommon methods

include Evaporation

Dehydration

Adding salt

Adding sugar

Freezing

Freeze drying

Jam

Anchovies

Water notaccessible

Milk

Fruit

Reducing the water helps toeliminate a avourable

environment or bacteria tomultiply!


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Removing moisture from food is called dehydration

sually it is done 'y having hot air 'lown over it*

Mil., eggs, potato, 7sh can all 'e dehydrated/ assoon as you add water it can 'e eaten*

1ehydrated foods are compact and light and can 'eeasily transported eg space travel, camping etc*

;nce water is added it can go 'ad in the usual wayas micro'es 'ecomes active again

1ehydration


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1ehydration


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&eatTreatment


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Bottling

Fruit can 'epreserved 'y 'ottling*

0 special 5ar with a lidand ru''er rim isused*

The 5ar is 7lled withfruit and syrup*


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Bottling

The 5ar is then heated and allowed to cool*

0s it cools the air inside shrin.s and itcreates a vacuum*

The lid pulls on tightly = the ru''er ringma.es it airtight*


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$anning

Food is place in metalcans

The air is suc.ed out ofthe cans and they arethen sealed

The cans are thenheated under pressureuntil all the micro'es

are .illed*


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ltra &eat Treatment(&T%

&eat is used to .ill 'acteria in mil.

Mil. is heated to a very hightemperature and then it is sealed*

6t can alter the >avor so most peopleprefer pasteurised mil.*

&T mil. can last quite a long time*


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?asteurisation

?asteurisation is named after @ouis ?asteur


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?asteurisation


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$hemical Treatment

0dd a chemical to the food which

.ills 'acteria 'ut is harmless toman*

6ncludes/

- pic.ling- smo.ing- salting


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?ic.ling


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mo.ing

The food is heldover a wood 7re

The smo.econtainssu'stances which

.ill 'acteria aswell as giving thefood a delicious>avor*


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alting

The food is either soa.ed in salt 'rine or salt is ru''edinto it

The salt draws the watermoisture out of the 'acterialcells using osmosis, hence .illing them*

6n hot countries, local people often put fruit or 7sh out inthe sun*

This dries the food and reduces the moisture content andleaves a high concentration of sugar or salt*

This .ills any micro'es present and this is why dried fruitlasts so long*


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alting


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?reservatives

0 speci7c category of food additives*

?rotect consumers when using multi-usecontainers

Concentrated tomato paste

Examples include; salt, sugar, sulphur dioxide,

smoke


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Reduced ;)ygen

Many microorganisms require o)ygen tosurvive*


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Food 6rradiation

@ast resort if no other method of preservationavaila'le*

Food is not radioactive*

6t destroys 'acteria* #arasites& moulds and yeast that spoil ood!

+almonella!


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Food 6rradiation

6s used to

,reat herbs and spices

(nwanted pest in traded ood

Carying doses are used

-ow dose destroys moulds

'igh doses kill bacteria that causeood poisoning

techniques to prevent food spoilage

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