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Causes of deterioration

Microorganisms growth, enzymes activity and insects



1. Heating jars of food to temperatures high enough to kill microorganisms and enzymes. Referred to as "Processing". 2. Keeps air out of the jars and as air cools down, it forms an airtight vacuum seal.


Bacteria home-canners should be aware of

Clostridium Botulinum. The bacteria is destroyed at boiling temperatures, but not its spores(which produce deadly toxins). They can grow in a low acid without oxygen type of environment.
1. Processing in a pressure canner (!) at T 240F or 116C
2. Presence of acid. (low acidic foods like meat, poultry, seafood, vegetables, foods in oil (pesto,garlic, flavoured oils or consumed within 3weeks) must be processed at min 116C in a pressure canner
High acid foods: jams, jellies, marmalades, fruits, fruit preserves, pickles
Low acid foods:Meats, poultry, game, seafood, vegetables, stews, soups.



Cementing substance holding the cell walls of fruit together and giving them shape. More concentrated in skin and cores. Fruits high in pectin are good for jams because they rely on natural pectin to gel. Boiled until gel phase is reached (10-45mins).


Commercial pectin

Commercial pectin is used for low pectin foods or to avoid boiling until gel phase. From apple pomace or citrus products, powder or liquid. Final sugar concentration = 60%


Special pectin

For recipes where little sugar is used. Forms gel without sugar, but with divalent ions (Ca). Contains locust bean gum and xanthan gum. Used for low calorie jams/jellies. Artificial sweetener can be used with this. Usually added after cooking if unstable during heated.


Test for pectin gel phase

1. Temperature test: Using a jelly thermometer, when it reaches 4degC after boiling T of water taken beforehand.
2. Plate test: Small amount placed on a cold plate put in the freezer gels
3. Spoon test (jellies): Cold metal spoon is dipped into the jelly and the drops join and drop as a sheet.



Linear sulfated polysaccharide extracted from red edible seaweed from North Atlantic Ocean. Powerful gelling agent (can be used for jams). Requires less sugar than regular pectin, no heat, sets really quickly (less 30mins), results in softer and more spreadable jam. Sold as jam gelling powder.


Carrageenan for food industry

Contains sugar, carrageenan, ascorbic acid, sodium benzoate. Common in ice creams, sherbets, condensed milk, instant soups, cookies, candies. Can stabilize, thicken or gel food.


Instructions with Carrageenan

1L of chopped fruits, 375ml of sugar, let stand for 15mins. Add one package of No Cook Freezer Jam gelling powder and let stand 5mins. Stir for one minute. Pour jams into clean jars with 1-inch (2,5cm) headspace


Freezer jams

Does not require freezing (-18C) because freezing halts microbial growth. Often made with artificial sweeteners (high T=unstable, low T like freezer = stable). Adequate for people who wish to lower the calorie/sugar intake, ppl with diabetes or wanting to lose weight.


Low sugar preserves

Concentrated fruit juices and artificial sweeteners may be used to reduce/modify carbohydrate content. Spices, herbs and flavourings can be used. (put in cheesecloth for easy removal)


Color preservation

Light coloured fruit should be placed in colour protection solution prior to canning and 5-7ml lemon juice/250ml may be add to prevent discoloration.


Long-term storage freezers are at




Slow freezing creates big crystals that puncture cell walls = big loss of juices. To avoid = use fast freezing :
1. Cooling food before freezing in small portion
2. Place food near freezer walls with space around package for air circulation
3. Limiting the amount of food placed in the freezer at once so as not to raise the freezer's temperature


Prevent freezer burn due to dry/cold air,

packaging should be airtight


Thawing is safest in

refrigerator, 10hours per kg


General instructions for successful freezing

1. Select fresh foods
2. Prepare foods quickly but with great care, using color-preservatives solutions for foods that undergo non-enzymatic browning.
3. Blanching helps preserve color, inactivates surface enzyme (slows enzyme activity) of fruits/veggies and enables easy removal of skins. May be cooled with cold water before freezing (stop cooking and prevent big crystals)
4. Package in odorless, tasteless, vapor-proof, moisture proof freezer bags. Prevents drying out and protects from odors. Remaining air in the bag should be removed.
5. Freeze at -18C
6. Thaw food carefully and use immediately after thawing


Why use drying?

Preservation. Reduces volume and weight. Lack of moisture inhibits microbial growth. Record of Methods, quantities and time required = reproductibilty of results


Drying: General Guidelines

1. Good quality, fresh, fully ripe products
2. Wash well and remove any bad spots
3. Slice food thinly (0,5cm or less)
4. Blanching to: prevent discoloration, slow enzyme activity, break skin to permit moisture to escape
5. Spread in single layer
6. If in the oven, monitor food to prevent over drying at edge of pans
7. If in dehydrator with multiple trays, trays should be rotated for even drying
8. Seeds may be easier to remove once partially dried to avoid loss of juices
9. 6-10% moisture may remain in food


Treatment solutions and methods for dried products

Sodium bisulphate solution (using food grade from drug store)
Salt solution
Citric acid or ascorbic acid solution


Storing of dried products

Cool thoroughly before packaging in small packages that can keep at room temperature in a cool, dark, dry place. Mold indicates too much moisture was left.


Dried vegetables and fruits

Vegetables should be soaked for several hours in the refrigerator to rehydrate before cooking, adding salt near the end. Practical for soups and stews. Dried fruits in snacks or baking


Science of fermentation

Known as Zymology. Metabolic process that produces chemical changes in organic substrate. Microorganisms break down molecules in foods, bringing desirable changes.


How canning jar lids are handled during canning process

Wash lids and put them in hot water (not boiling to not melt the glue on the lid)
After the food is inside the jar with a headspace, no air bubbles and stickiness on the jar rims, center lids on jar. Apply screw bands firmly until resistance(fingertip tight) Check jar seals.


How do you know jar has good vacuum seal

There should be no flex when center is pressed. Sealed lids curve downward. Attempt to lift lids off with fingertips.



Is provided and different for every recipe.
To make sure that content does not leak.


Fermentation with oxygen...?

Vinegar, kombucha, tempeh, certain cheese occur with the presence of oxygen but are still considered fermentation by food industry


Benefits of fermentation

Preserve flavor, nutritive value, color.
Predigest food which can make some micronutrients more bioavailable, produce desirable acids and alcohol, and break down toxic compounds to make food safe.


Lactic acid fermented foods

Retain nutrient + deepening flavor profile. Sour foods such as pickled cucumbers, kimchi, yogurt, sauerkraut, sourdough bread.