not mine by pdst.ie

1. FOOD PRESERVATION
HEAT TREATMENTS
© PDST Home Economics

2. HEAT TREATMENTS
 Fruit and vegetables can be preserved at home
using high temperatures.
 Methods used are:
jam - making, chutney - making and bottling.

3. JAM MAKING
 Jam is cooked fruit
boiled with 65%
sugar.

4. HOW SUGAR
PRESERVES FOOD
 Sugar dissolved in food
forms a solution with a low
water concentration.
 Microbial cells have a high
water concentration and
the cells are enclosed by a
semi-permeable membrane.
 The water is drawn out of
the microbial cells by
osmosis and the cells are
dehydrated and destroyed.

5. PRINCIPLES OF JAM -
MAKING
 High temperatures are used to destroy enzymes
and microbes in the fruit.
 Jam is sealed in pots to prevent re-entry of
microbes.
 65% sugar prevents microbes growing in jam once
opened.
 Pectin, acid and sugar make jam set.

6. WHAT IS NEEDED FOR
GOOD JAM
Fruit
Sugar
Acid
Pectin

7. FRUIT
 Just ripe.
 Good quality.
 Acidic.
 High in pectin.
 If low in acid and pectin,
combine with a fruit high
in these e.g. apples or use
jam sugar.

8. SUGAR Preservative.
 Helps setting.
 Too much causes
crystallisation.
 Too little causes
fermentation and jam
won’t set.
 Jam sugar / Sure-set
sugar is sugar crystals
coated with pectin and
acid.
 Using Jam sugar means
a shorter boiling time
and as it is purer, less
scum is produced.

9. ACID
 Draws out pectin
from cell walls of
fruit.
 Prevents
crystallisation.
 Improves colour and
flavour of jam.
 If there is too little
acid in fruit, add
lemon juice, citric
acid or use jam sugar

10. PECTIN
 Polysaccharide.
 In cell walls of ripe
fruit.
 Fruit with a low
pectin content can be
combined with a high
pectin fruit.
Alternatively, pectin
can be added or jam
sugar can be used.

11. CHARACTERISTICS OF A
GOOD JAM
Clear
Well set
Keeps for a year
Bright colour
Fruity taste

12. EQUIPMENT
 Heavy based stainless steel saucepan or
preserving pan.
 Wooden spoon.
 Sugar thermometer.
 Measuring jug.
 Jam jars.
 Jam pot covers- wax and cellophane.
 Elastic bands and labels.

13. STAGES IN JAM - MAKING
 Weigh fruit and sugar accurately.
 Jars - wash and sterilise in oven- no chips or
cracks.
 Prepare fruit- wash, peel, remove stones & chop.
 Simmer fruit & water according to recipe.
 Add pre-warmed sugar & dissolve.
 Boil rapidly. Test for setting - ( temperature
105ºC , plate/wrinkle test or flake test)
 Skim jam & fill jars to 5mm.
 Cover immediately with waxed discs & cellophane.
 Clean jar & label - name & date.
 Store in a cool, dark, dry, well – ventilated area.

14. CHUTNEY - MAKING
 Chutney is fruit, vegetables or a mixture of both
boiled with sugar, vinegar and spices until the
mixture is thickened.
 Chutney is served with meat, cheese, sandwiches,
salads, burgers or as an accompaniment to curry.

15. PRINCIPLES
 High temperature
used to destroy
enzymes and
microbes.
 Sealing prevents
recontamination.
 Sugar preserves by
dehydrating microbial
cells.
 Vinegar lowers pH
preventing growth of
microbes.

16. MAKING CHUTNEY
 Same equipment as for jam. Plastic – lined, metal
jam pot lids or fabric circles steeped in melted
wax are used instead of cellophane covers. These
prevent evaporation.
 Follow recipe and method carefully.
 Chutney is kept for a few months before eating
to let the flavour mellow.