Processing Food by Heat Can destroy microorganisms Can denature enzymes Can increase shelf life of food with appropriate packaging Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Four Levels of Heat Preservation Blanching Submerging food for short time in boiling water or steam Stops enzyme activity Helps to prevent undesirable flavor, texture, and color changes of the food Used for pretreating fruits (sometimes with a syrup blanch) and vegetables Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Four Levels of Heat Preservation Commercial Sterilization Destroys microorganisms that cause illness, bring about food spoilage, or create toxins Processed in sealed containers Prevents resistant bacterial spores from reproducing and making them inert May produce flavor and texture changes in the food Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Four Levels of Heat Preservation Pasteurization Heating foods just below the boiling point Stops enzyme activity and destroys pathogens Used for foods, such as eggs, fruit juices, milk, and oysters Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Four Levels of Heat Preservation Sterilization Completely destroys all microorganisms Different microbes require varying temperatures and sustained times Wet heat (food is in the presence of water or moisture from steam) must be sustained at a temperature of 250°F for 15 minutes to kill all microbes Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Factors Affecting Processing Method Heat Transfer - extremely important factor in order to maintain the integrity of food product Conduction Foods do not move in the can Food processed as energy from molecular collisions is passed from the outside food layer in the can to the cold point in the center of the can Convection Liquid in the can is heated resulting in currents, which cause the liquid to become less dense, rise to the top, and thus, speeding the transfer of heat energy throughout the can of food Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Factors Affecting Processing Method Food Components Type of microbe in food determines processing method Food size and density can affect the choice of processing method Some ingredients, such as fats, oils, protein, starch, and sugar, protect the microbe from heat, making it important to raise the temperature and increase the processing time Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Factors Affecting Processing Method pH of the Food Low-acid foods have a pH of 4.6 and higher C. botulinum can survive and multiply Can be deadly Must process these foods at higher temperature High-acid foods have a pH between 2.0 and 4.6 Can be processed at lower temperatures than low- acid foods Boiling temperature (212°F) will destroy most microbes Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Factors Affecting Processing Method Time and Temperature Must balance the ability to kill pathogens with the effect of high heat on food quality Thermal death curve – line graph that illustrates how long it will take to kill a microorganism at a certain temperature Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Commercial canning Processes vs. Home canning Processes Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Commercial canning Processes Points to consider Method must kill harmful microorganisms Method must maintain the quality of the food while destroying microorganisms Method must be a reasonable cost including equipment, energy use, packaging, and shipping costs Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Commercial canning Processes Heating food after packaging Retort – huge pressure canners with a large, sealed chamber Agitation retorts – adds movement which stimulates liquids which are heated quicker than food Pouch retorts – pouches replace other containers – processing time is shortened because heat penetrates the pouch quicker Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Commercial canning Processes Heating food after packaging Hydrostatic Cooker and Cooler Filled bottles, cans, and jars more continuously through a U-shaped tube filled with water and steam Temperature and pressure inside the tube change during the processing period Home canning methods Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Commercial canning Processes Heating food before packaging Requires sterile conditions only found in commercial processing Batch Pasteurization Mostly used with liquids, such as milk Heat liquid, fill container, seal, process Aseptic canning Sterilized food is placed in sterilized container Requires careful monitoring Temperatures can go as high as 302°F Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Home canning Processes Packing Methods Cold pack Raw food is packed in jars, filled with a boiling liquid, closed with a lid, and then processed Used for foods that are easily damaged Hot pack Food is heated in a liquid or syrup to 171°F and packed in jars while still hot; then jars are sealed and processed Foods, such as corn, can be packed more tightly if heated prior to packing Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Cold Processing Food Preservation Cold processing methods will not destroy microorganisms in the food. Cold process methods will not denature enzymes. Cold processing slows down the growth of (chemical reaction rate) microorganisms if they are already present in the food, but may grow and multiply when the food is thawed unless the food is carefully handled. Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.

Cold Processing Food Preservation Terminology Blast freezer Cryogenic liquids Freeze drying Freezer burn Humidity Immersion freezing Indirect contact freezing Lyophilization Refrigerant Respiration Sharp freezing Sublimation Syneresis Copyright © Notice: The materials are copyrighted © and trademarked ™ as the property of The Curriculum Center for Family and Consumer Sciences, Texas Tech University.