Food Processing and Preservation
Puff drying (method of dehydration)
*heat and vacuuming* -increases the pressure differences between the internal and external environment *vacuuming and steaming* -temperature increase (212 degrees F) and external pressure release examples: puffed wheat and rice cereals
Explain the negative and positive results of dehydration.
*positive* -increase shelf life -reduction in distribution cost due to less weight *negative* -deterioration may occur -enzymatic action can result in color, flavor, and textural changes -enzymatic changes can be control by deactivating enzymes through blanching or by adding sulfur compounds (common with dried soft fruits) -non enzymatic browning may occur; caramelization, Maillard browning
Slow freeze
-extracellular crystallization occurs prior to intracellular crystallization -draws water from the inside of the cell as external solute concentrations -results in cell wall tears and shrinkage, physical damage occurs because of water/ice expansion -generally the type of freezing that occurs in home freezers
What is enhanced when sensory properties are modified?
-flavor -texture -aroma -color -physical state
Disadvantages of severe heat treatment
-food is over cooked -major changes in texture, flavor, and nutritional quality
What is dehydration?
-food preservation achieved through the removal of some amount of water -many methods have been utilized throughout history -eliminates available moisture for microbial growth -not a permanent condition; dehydrated food products exposed to humid environments can support microbial growth
Commercial sterilization
-food product is placed in hermetic container (canned foods) and is heated to a sufficiently high temperature for a sufficient length of time to destroy all microbial and enzyme activity -implies less than absolute destruction of all microorganisms and spores, but any remaining would be incapable of growth in the food under existing conditions (can remains sealed) -severity of treatment can result in substantial changes to nutritive and sensory characteristics
Advantages of preservation
-foods last longer -seasonal foods can be enjoyed during off season -foods can be shipped longer distances -foods can be stocked in retail for extended time periods
Unprocessed food
-foods that are eaten in their raw, natural state -fresh produce from a farmer's market is generally an example of unprocessed
Highly processed foods
-foods that are pre-packaged, ready to eat, require very little post-purchase processing -made from a combination of unprocessed, minimally, and processed food ingredients -designed for consumer convenience and on-the-go life style
Irradiation pasteurization
-foods, such as poultry, red meat, spices, and fruits and vegetables, are subjected to small amounts of gamma rays -this process effectively controls vegetative bacteria and parasitic foodborne pathogens and increases the storage time of foods
Starch syneresis (problems associated with freezing)
-freezing and thawing cycle may produce weeping in pie fillings and puddings -freezing draws water out for crystal formation and its not reabsorbed during the thawing phase
Rapid freeze
-freezing is completed rapidly, intracellular crystallization occurs before moisture migrates outside the cell -less physical damage occurs to cells -industrial or commercial freezing
Radiation
-heat transfer by emission of electromagnetic waves which carry energy away form the emitting objects to the food product -two types of electromagnetic energy: infrared (IR) and radiofrequecy (RF)
Conduction
-heat transfer by means of molecular agitation within a material without any motion of the material as a whole -transfer of heat through a solid material
Convection
-heat transfer by motion of fluid, such as air or water -when the heated fluid is caused to move away from the source of heat, carrying energy with it
Freezing
-holding food products at temperature that crystallize water (less than 0) -allows long-term storage for several months
Milk
-improves the quality of milk and milk products -increases shelf life by destroying undesirable enzymes and spoilage bacteria
Processed food ingredients
-ingredients that radically change the nature of original raw material and are used in preparation or manufacture of highly processed food -may be nutrient-poor and high in calories -examples are flours, oils and fats, sugar, sweeteners, starches
History of pasteurization
-invented by Louis Pasteur in 1864 (French scientist) -discovered that heating beer and wine was enough to kill most of the bacteria that caused spoilage, preventing beverages from turning sour -achieved by eliminating pathogenic microbes and lowering microbial numbers to prolong the quality of the beverage
Secondary processing
-is the conversion of ingredients into edible products -combining ingredients in a particular way to change their properties -ex: baking
Plate freezing
-utilizes conductive heat transfer -packaged food is places between metal plated (plates make full contact with packaged product) -product is brought to 0 degrees F very rapidly -once frozen, products are placed into freeze storage -automated conveyor systems can deposit frozen packages into cases and freezer storage
Cryogenic freezing
-utilizes convective heat transfer -food products are either immersed or sprayed with liquid nitrogen (LIN); LIN is an inert gas, no residue on food -LIN has a boiling point of -320 degrees F -freezing occurs extremely rapidly, much faster than mechanical freezing methods -used for meats, poultry, seafood, fruits, and vegetables
Fortification
adding nutrients about natural levels (adding iodine to salt)
Air blast tunnel freezing
-utilizes convective heat transfer -racks of product are placed in an insulated tunnel or a continuous conveyor passes through the tunnel -extremely cold air is blown through the tunnel -product reaches 0 degrees F very rapidly -product is then placed into freezer storage -freezing may occur pre or post packaging
Minimally processed food
-washing, peeling, slicing, juicing, removing inedible parts, freezing, drying, and fermentation are examples -"light-processing" is a term used when fruits and veggies receive only a washing and/or waxing as their "processing"
Labeling requirements of irradiation
-whole food items must be labeled if they have been treated with radiation -not required for processed foods having irradiated ingredients or restaurant foods
Emulsions (problems associated with freezing)
-will breakdown/separate -subject to dehydration and precipitation
High-temperature-short-time treatment
.-pourable products, such as juices -heated for 3 to 15 seconds to a temperate that destroys harmful microorganisms -after heating, the product is cooled and packaged -most drink boxes and pouches use this pasteurization method as it allows extended unrefrigerated storage while providing a safe product
Cellulose (problems associated with freezing)
becomes tougher through the freezing process
What is food processing?
taking food products through a series of steps to create the final marketable product
What is food preservation?
treatment of food products to prevent the growth of harmful bacteria, fungi, and other micro-organisms, and prevent the oxidation of fats
Freeze drying (method of dehydration)
use sublimation in a freezing and vacuuming to evaporate moisture from the product example: instant coffee, meats, vegetables
Heat transfer
used in food processing; methods include convection, conduction, radiation
Steam pasteurization
uses heat to control or reduce harmful microorganisms in beef
Adding chemicals (chemical food processing)
using chemicals (salt, carbon monoxide, etc.) to control microbe activity and preserve quality factors such as color
Moderately processed foods
usually foods that have undergone processing to increase shelf life or create the food; examples include: -milk churned to butter -olives pressed to make oil -veggies washed/cut and frozen
Odors (refrigeration)
*sources of foodborne odors:* -naturally occurring chemicals in food -Volatile Organic Compounds (VOCs) -product of spoilage is caused by microbial action creates odiferous gasses and vapors *odors can between foods during refrigeration if proper steps aren't taken* -store foods with strong odor separately -utilize appropriate packaging -protect foods prone to accepting odors (butter, milk, mild cheeses)
Temperature (refrigeration)
*temperature is a critical component of refrigerator system* *to0 cold"* -chill injury to fresh fruits and veggies -sugar development in potatoes -increased starch content in sweet corn *too "warm* -spoilage issues *food items must be brought to acceptable temperatures within 4 hours*
Commercial freezing processes
*three methods are used:* -air blast freezing tunnels -plate freezing -cryogenic freezing *all three are methods of rapid freezing techniques*
Infrared waves
*two subdivisions* -near infrared: shorter waves, transmitted deeper into water -far infrared: longer waves, absorbed at surface
Selection of heat treatments
*utilized for a particular food preservation is dependent on several factors* -purpose of treatment -additional preservation steps -physical and chemical properties of food -heat resistance of microorganisms in food
History of canning
-Nicholas Appart credited with the development of the canning methodology -discovery was in response to a challenge issued by Napoleon to provide safe food for his army -Peter Durand received a patent for the thin-plated can in 1810
Irradiation process
-a cold process; does not add heat to food -gamma rays used -form of ionizing electromagnetic energy -energy passes through the food products -sterilizes and preserves the food products -no radioactive residue or other material is left on the food; there is no radioactive contamination when food products are irradiated
Refrigeration
-a food preservation method that relies on cold temperatures -food is held at temperatures below 45 degrees F (below 41 is ideal) -temperature is above freezing -temperatures do no sterilize food -retard microbial growth -spoilage will still occur
Blanching
-a form of mild heat treatment -inactivates enzymes that cause the deterioration of foods during freezing (freezing does not stop enzymatic activity) -using primarily for vegetables and some fruits -product is dipped in boiling water for a short period of time (1-3 minutes), then plunging it into freezing water to stop the cooking process (some microbes are killed bu this is not the primary purpose) -product is then frozen for long-term storage -preserves color and flavor longer during long-term frozen storage
Government approval of irradiation
-approval of use granted by every major government and health agency in the U.S. -consumer health activist remain skeptical of its safety
Positive effects of irradiation
-bacterial effect (reduces overall microbial load) -kills insects (eggs, larvae, and adults) -controls ripening -inhibits sprouting of some vegetables
Pasteurization processes
-based on type of food product and desired results -two types are: *high-temperature-short-time treatment* and *low-temperature-long-time treatment*
What are the categories of processing?
-completely unprocessed -minimally processed -moderately processed -highly processed
Spoilage (refrigeration)
-damage to edible quality of food products -negative impact on food quality -negative growth of microorganisms -increased risk of foodborne illnesses -can occur when temperature requirements are not maintained
Heat treatment effects on food quality
-degrades food quality -select mildest heat treatment required to minimize negative effects on the food or food product while meeting the desired level of preservation needed for the food item
What is the purpose of pasteurization?
-destroy pathogens (microorganisms that cause foodborne diseases) -reduce bacterial count (generally refers to spoilage bacteria) -inactivates enzymes -extends shelf life of food products
Mechanical drying (method of dehydration)
-dried with mechanically heated air in a tunnel, cabinet, or tray blown over product
Freezer burn (problems associated with freezing)
-it is dehydration -occurs because of the sublimation of ice -water (ice crystals) in frozen food vaporizes from the frozen product resulting in desiccation (dehydration) of the product -desiccated areas become much tougher than other areas -can occur in any frozen product but most obvious in frozen meat, poultry, and seafood -freezer burn can be controlled using moisture-proof freeze wraps -containers that have air space surrounding the product can lead to more freezer burn than packaging that doesn't
Severe heat treatment aims to do what?
-kill all bacteria -food will be commercially sterile
Mild heat treatment aims to do what?
-kill pathogens -reduce bacterial count -food is not sterile -inactivate enzymes
Uses of irradiation
-may be used wheat, potatoes, spices, pork, red meat, fruit, poultry, fresh produce
Low acid foods
-may contain heat resistant microorganisms -long term storage requirements: vacuum-sealed and severe heat treatment
Effects of irradiation on food products
-minimal changes to sensory aspects of food -minimal changes to nutritive values of food
Sterilization (AKA retorting)
-most common -preserves or makes food more palatable -destroys all pathogenic and spoilage causing microorganisms and inactivates enzymes using high temperature steam and pressure -all canned foods are sterilized in retorts (large pressure cookers)
Degrees of food processing
-not all foods undergo the same degree of processing -same foods may differ when subjected to different degrees of processing -processing may have beneficial or harmful effects on nutritive properties of food
Controlling factors of dehydration
-numerous factors must be controlled for proper dehydration -environmental conditions (temp. humidity, and pressure) -portion size (not too thick) -storage considerations
Common food processing methods
-numerous processing methods are used to make food products -individual food product may require only one type of processing or multiple types to make the final consumer product -food processing can be physical or chemical -ex: heating, blanching, drying, freezing, adding chemicals
Oxidation (problems associated with freezing)
-oxidative and enzymatic degradation of food products are chemical reaction and aren't eliminated by freezing but may slow down -oxidation of unsaturated fats may lead to an off-flavor -asorbic acid (vitamin C) can be oxidized during freezing -if enzymes are not denatured prior to freezing may result in the browning of fruits and vegetables -blanching prior to freezing can denature enzymes
The problem with freezing
-physical damage due to ice crystal formation -effects of increased solute concentrations associated with progressively removing water to form ice crystals -minimized by initially using rapid freezing methods
Thermal or heat processing (heat preservation)
-physical food processing method -involves heating or cooking to: eliminate pathogens; eliminate or reduce spoilage organisms; extend shelf life of foods; improve palatability of foods -ex: sterilization (canning, boiling, autoclaving); pasteurization; blanching; microwaving
Controlled atmosphere of refrigeration
-produce and meat is often stored in refrigerated, oxygen-reduced atmosphere -atmosphere enriched with carbon dioxide or nitrogen
Recrystallization (problems associated with freezing)
-product quality suffers when product temperatures fluctuate -results in the formation of large ice crystal formation *example: ice cream* -when ice cream melts a little at room temperature it recrystallizes when it's put back into the freezer (slow freezing)
What are types problems with freezing?
-recrystallization -freezer burn -oxidation -colloidal substance changes
Advantages of refrigeration
-retards enzymatic action -controls microbial growth -prevents rancidity caused by oxidation of fatty acids
Preservation methods
-salting -canning -fermenting -pickling -drying -smoking
Disadvantages of mild heat treatment
-short shelf life -another preservation method must be used, such as a refrigeration or freezing
Expected storage time
-shorter: pasteurized foods with refrigeration, freezing, or vacuum packing -longer: canning/commercial sterilization
Irradiation
-the administration of measured doses of energy -irradiation is product-specific (different doses are used for different products
Ultra-pasteurization
-the heating of milk and cream to at least 280 degrees F for at least 2 seconds -because of less stringent packaging, must be refrigerated -shelf life of milk is extended 60 to 90 days -Note: after opening, spoilage times for ultra-pasteurized products are similar to those of conventionally pasteurized products
Why process foods?
-to extend shelf life (preservation) -maintain sensory properties -maintain or improve nutritive properties -ensure safety -make more convenient -gain economic value
Cross-contamination (refrigeration)
-transfer of harmful substances from one product to another -pathogens from improperly placed or enclosed raw products can be transferred to other foods
Physical food processing types
-transformation of "raw" ingredients by physical methods into food products -ex: sterilization, pasteurizing, blanching, frying, refrigeration, freezing, irradiation, evaporation, drying/dehydration, emulsification, homogenization, extrusion, hurdle or combination processing
Pasteurization
-type of mild heat treatment used for milk, liquid eggs, fruit juice, and beer
Ultra-high-temperature pasteurization
-typically involves heating milk or cream 280 to 302 degrees F for 1 to 2 seconds -the milk is then packaged in sterile, hermetically-sealed (airtight) containers and can be stored without refrigeration for up to 90 days -after opening, spoilage times for UHT products are similar to those of conventionally pasteurized products
Types of chemical food processing methods
1. water activity 2. adding chemicals 3. pH control
What are the two types of freezing?
Slow freeze and rapid freeze
pH control (chemical food processing)
changed in pH are used to aid in food preservation and processing
Eggs
degree and type of pasteurization is based on the form they are sold in: liquid whole eggs, dried eggs, whole eggs, in shell
Mild heat treatment
does not provide safe long-term storage by itself but serves as a "pre-treatment" for refrigeration and freezing
Natural or sun drying (method of dehydration)
dried by direct sunlight or hot, dry air
Food processing to maintain/improve properties
ensure important nutrients are maintained or improved for the consumer through enrichment and fortification
Colloidal substance changes (problems associated with freezing)
freezing may result in changes to colloids
Primary processing
is the conversion of raw material into food commodity; ex: milling, butchering
Drum drying (method of dehydration)
liquid product (milk, juices, purees) are dried in rotating steel drums, then scraped off sides
Spray drying (method of dehydration)
liquids are sprayed into a chamber concurrently with hot, dry air examples: eggs, coffee, milk
Advantages of severe heat treatment
long shelf life
Water activity (chemical food processing)
managing water activity in foods to prevent or retard growth of microbes
Advantages of mild heat treatment
minimal damage to flavor, texture, and nutritional quality
What is the main effect of pasteurization?
nutrients and flavor (HTST cause less damage to nutrients and sensory characteristics of foods than LTLT)
Smoking (method of dehydration)
preserves meat by drying and imparts flavor example: jerky, some sausages
Enrichment
restoration of natural nutrients lost during processing steps (adding vitamins to flour)
