FOOD PRESERVATION BY FREEZING Conventional Methods of Food

FOOD PRESERVATION BY FREEZING Conventional Methods of Food Preservation

Freezing 2 Clarence Birdseye began frozen food industry in 1920 s Research and Developments “Antifreeze” proteins - control size of ice crystals Air impingement – fast cooling Pressure shift – small crystals Time-temperature indicators – monitor temperatures Food Freezing

Freezing Process 3 Three stages Product lowered to freezing Ice crystals form Temperature lowered to storage temperature Microorganism activity is minimal Will grow after thawing Enzyme processes may continue Blanching Food Freezing

Changes in Frozen Foods 4 Formation of crystals Fruits and vegetables cells may be damaged Rapid freezing favors small ice crystals Enzyme Action Blanching Drain well and freeze. Sugar or sugar syrups Food Freezing

Changes in Frozen Food 5 Nonenzymatic Oxidation Usually associated with fat Fat of pork particularly susceptible Desiccation Moisture loss by sublimation Freezer burn Activity of Microorganisms Inactive or minimally active at low temperatures Growth and activity resume after thawing Food Freezing

Freezing Techniques 6 Fruits Vegetables Meat, Fish, Poultry Eggs Prepared Foods Food Freezing

Other Issues 7 Container selection Use and management of freezer Food Freezing

History 8 The frozen food industry was born in the 1920’s Clarence Birdseye produced the first frozen fish Food Freezing

History 9 The industry continued to grow and develop with the growth of such technology as fast-freezing equipment, home freezers, and the microwave oven The 1950’s brought on the TV dinner revolution Food Freezing

The Science of Freezing 10 It preserves food by slowing the action of enzymes rather than destroying them Food Freezing

The Science of Freezing 11 Foods that are free of microorganisms when frozen will remain so, since most microorganisms can’t grow at such a low temperature Food Freezing

FREEZER BURN 12 If protein food is not wrapped properly the cold air will cause the food to toughen, discolour and dry out This is called freezer burn Food Freezing

Freezer Burn 13 Ø Caused by the loss of moisture from food when the food is exposed to air Ø Culprit: Loose packaging, fluctuation in freezer temperature Food Freezing

Freezer Burn 14 If not packaged properly, even foods that do freeze well can experience a damaging effect Foods that are freezer burnt often have a brown or grayish color, look very dry, and have a fuzzy gray or white spots that look like icy mold Food Freezing

Commercial Freezing 15 Rapid Freezing Process – Limited changes in color, texture, size and flavor Also, helps foods resist freezer burn Ice crystals are smaller causing less damage to food cells Food Freezing

Commercial Freezing 16 Freezing in air is the oldest and still the most common method of freezing food, and also the one used in home freezing Indirect-contact freezing is food that is placed on belts or trays. A refrigerant circulates through the wall beside the food and it chills quickly and freezes Food Freezing

17 Commercial Freezing Cont… Immersion freezing food is submerged directly in non-toxic refrigerant to cause quick freezing Most packaging is opaque because many foods lose flavor when exposed to light Food Freezing

Home Freezing 18 Storage containers and wraps used for frozen foods at home must be moisture proof and airtight to maintain quality Food Freezing

Home Freezing 19 Even if it is properly maintained it has a 6 -12 month period before it starts to deteriorate Food Freezing

Home Freezing 20 Foods with high water content, including grapes, pears, salad greens, lose shape and texture when frozen Be sure to label and date all packages!! Food Freezing

Freeze-drying 21 Is a commercial process that combines freezing and drying to preserve foods. First food is frozen; then its treated to remove the solvent from dispersed or dissolved solids. In most food, this means removing the water. Technical name: lyophilisation. Food Freezing

Sublimation 22 During freeze-drying, water in the form of ice is removed through sublimation – occurs on the surface and continues inward. Wet clothes on the line during winter example. By the time the ice at the very center has sublimed, up to 99% of the food’s moisture has been removed. The result is dried food. Food Freezing

Sublimation 23 Flash frozen or frozen very quickly – a special, low-pressure chamber. It is then held at or below freezing temperature. The low temperature keeps the water frozen, and the low pressure speeds the rate at which ice crystals in the food escapes as water vapor. Food Freezing

Using Freeze Dried Foods 24 Foods could be stored for months even years Must be protected in airtight packaging Examples are fruit in cereal and chicken in instant soup Makes foods extremely light – should be reconstituted. Food Freezing

26 Food Freezing

RULES FOR FREEZING 27 Food Freezing

Packaging Food 28 Suitable containers Safety – needs to be non-toxic and provide a sanitary, protected environment Food quality – must provide protection from light, odors Convenience – open easily, resealable, and able to pour easily are a + Expense – lower packaging means lower cost for manufacturers and the result is a lower cost to consumers! Environmentally safe – recyclable containers! Marketing appeal – attractive to the consumer! Food Freezing

Packaging Food 29 Modified-atmosphere packaging Called MAP – This process creates a specific gaseous environment for a food product to lengthen shelf life. Used mainly for ready-to-eat products with extended shelf lives. Bags of lettuce, baby spinach, and baby carrots use this technology in stores! Food Freezing

Packaging Food 30 Aseptic packaging Used for beverages and liquids that have been aseptically treated – extremely high temperatures and contain several layers of material. Containers are not recyclable. Example: Drink boxes! Food Freezing

SUITABLE PACKAGING MATERIALS PROPERTIES Strong. Water proof. Vapour proof. Grease proof. Easy to use. Sealable. EXAMPLES Strong, polythene freezer bags. Aluminium containers. Aluminium foil. Freezer paper. Waxed cartons. Plastic boxes with tight lids.

Packaging Food 32 Edible films/wraps Additional film added to apples - Wax Trends in packaging Edible films “Smart” packaging that tells the consumer a number of things – if the temperature has ever risen enough above the proper temperature the contents of the package may be unsafe to consume “Intelligent” packaging that tells the consumer whether or not the contents are spoiled and may not be safe to eat. Ex. A dot that may change colors Food Freezing

Technology & Logistics: Commercial Refrigeration Systems 33 Food Freezing

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Freezing Equipment – Adapting to Market Demand Industrial Freezing Equipment 35 Food Freezing

Freezing Equipment – Making Production More Profitable 36 Industrial Freezing Equipment Food Freezing

Consolidating the Business with High Quality Equipment

Drip loss 38 Drip loss During freezing, frozen water is removed from the original location in the foodstuff to form ice crystals. During thawing, water may not be reabsorbed in the original region, leading to the formation of drip. Drip loss leads to the loss of nutrients, affects texture and juiciness and modifies the appearance of the product Food Freezing