Final Flashcards
Food Processing:
the conversion of raw animal
and plant tissue into forms that are convenient and
practical to consume.
Food Preservation:
the use of specific thermal
and non-thermal processing techniques to minimize the
number of spoilage microorganisms in foods, making them
safe and giving them an extended shelf-life.
Includes canning, refrigeration, freezing, dehydration, high pressure processing, irradiation, addition of food additives, fermentation, etc.
Purposes of Food Processing
• To improve product quality
– Quality: degree of excellence, the sum of acceptability
characteristics, most of which are subjective
• To formulate or manufacture a food product with
specific characteristics
• To improve product consistency
• To improve food shelf-life (the time it takes a product
to decline to an unacceptable level)
• To improve food safety (freedom from harm)
• To maximize output, or to minimize defects
Processed Foods
Any food other than a raw agricultural
commodity, including any raw agricultural
commodity that has been subject to washing,
cleaning, milling, cutting, chopping, heating, pasteurizing, blanching, cooking, canning, freezing, drying, dehydrating, mixing, packaging, or other procedures that alter the food from its natural state.
Processing effect on nutritional content
• Processing of foods, including the addition of
ingredients, may reduce, increase, or leave
unaffected the nutritional characteristics of
raw agricultural commodities.
Processed Foods. Categories
• According to the International Food Information
Council:
1) Minimally Processed Foods
2) Foods Processed for Preservation
3) Mixture of Combined Ingredients
4) Ready-to-eat Foods
5) Convenience
Minimally Processed Foods
Foods that use little processing • Washed, packaged fruits and vegetables • Often simply pre-prepared for convenience ü Bagged spinach ü Cut vegetables ü Roasted nuts
Foods Processed for Preservation
• Processed to maintain freshness and nutrients
ü Canned fruits/vegetables
ü Frozen fruits /vegetables
Mixture of Combined Ingredients
Use of sweeteners, colors, preservatives and other
additives to improve safety, taste, visual appealing
ü Cake mixes
ü Salad Dressings
üCured meats
üArtificially flavored and colored foods
Ready-to-eat Foods
• Foods that require little preparation • Do not need to be cooked before use ü Breakfast cereals ü Lunch meats ü Carbonated beverages ü Dry cereal, nuts
Convenience Foods
• Packaged to keep fresh and save time • More “heavily” processed ü Frozen meals ü Frozen Pizza ü Microwaveable dinners
Processed Foods. Negative Aspects
Controversial additives • GMOs • trans fats • Saturated fats • Added sugar • Sodium • Caloric intake
Processed Foods. Positive Aspects
Food Safety and Preservation • Removal of anti-nutritional factors • Foods for people with special needs • Fortification and Enrichment • Affordable, Convenient
Why is it important to understand Food Processing?
• Food processing methods are used to preserve and
create foods.
• If you understand how something functions, you can
improve product quality
Food Processing and
Food Chemistry
• Controlling chemical reactions that play a role in
food quality and food spoilage:
ü Breakdown of carbohydrates, proteins, lipids, and pigments
ü Browning reactions
ü Starch gelatinization and retrogradation
ü Emulsification and foam formation
ü Gel formation and viscosity-building
ü Lipid oxidation and rancidity
ü Protein denaturation and coagulation
ü Enzymatic reactions
Food Processing and
Food Microbiology
• Controlling microbial growth in foods that affects food quality and food spoilage: Manipulation of: – pH – aw – Oxidative state – Nutrient content – Biological structure – Naturally-occurring inhibitors – Temperature – Gaseous atmosphere – Relative humidity
Unit Operations in Food Processing
• Unit Operations: Categories of common
operating steps practiced in the food industry
• A basic step in a process
• A process may have many unit operations
to obtain the desired product
Unit Operations examples
• Materials handling • Cleaning • Separating • Disintegrating • Pumping • Forming • Mixing v Heat exchange v Evaporation v Drying v Packaging v Non-thermal methods
Materials Handling
• Handling raw or partially processed materials
• Important considerations related to product
quality
Cleaning and Sanitation
• The equipment used will vary depending on
what you want to clean
– Water
– Surfaces of foods
– Surfaces of equipment or processing facilities
Clean:
Remove soil (matter out of place)
Sanitize:
Reduce microbial contamination to a safe level
Disinfect:
Kills 100% of vegetative cells, may not kill bacterial spores and viruses
• Sterilize:
Complete destruction of all forms of life (bacteria, bacterial spores, fungi, viruses)
Soils in food processing facilities are composed of
deposits of
fat, carbohydrates, proteins, and mineral
deposits
• 4 Factors of Cleaning:
– Time
– Action
– Concentration
– Temperature
Spray ball cleaning takes a lot of
time and chemical action
Rotary wetting cleaning takes a lot of
time and chemical action
Boiling out/fill and drain takes a lot of
time, chemical action and temperature
Size Reduction
• Reductions of particle size (cutting, grinding, pulping,
chopping, dicing, grating, homogenizing)
• Equipment selection can play a role in product quality
Pumping
Moving foods from one point to another • Important characteristics in selecting pumps: – Minimize product damage – Ease of cleaning
Mixing
All mixers do “work” on a product and can
affect product quality
Unit Operations in Food Processing examples
ü Pasteurization ü Sterilization ü Evaporation ü Drying ü Freezing ü Frying ü Baking ü Boiling ü Non-thermal methods
Process flow diagrams
• Basic Shapes
– Arrows indicate the Direction of Flow
– Parallelograms indicate Inputs or Outputs
– Diamonds indicate Decision Forks
– Rectangles indicate Processes
The Removal of Water
• Purposes:
– To slow spoilage (shelf-stable aw <0.6)
– To reduce bulk/weight/volume
– To control texture
– To make new products
• Concentration and Evaporation:
– The partial removal of water from
foods to increase its total solids
content
• Drying:
– An extensive approach to moisture
removal in which product moisture
is reduced to a few percent
Concentration and Evaporation
• Methods and Techniques
– Open kettles or pots
– Vacuum evaporator
– Freeze concentration
Volatile partitioning
Volatile compounds are compounds that due to their
high vapor pressure and low water solubility enter the
gas phase (air)
– Freeze concentration:
concentration of a product at the freezing point by ice crystal formation and separation
• The concentrate retains the flavor, color and aroma
• Crystallization: production of ice crystals
• Separation: separation of the ice crystals
The Drying Process
• Constant Rate Period (BC): straight line
– Water evaporates from the surface
• Critical Moisture Content (C)- where flat line turns into slope
• Falling Rate Period (CD):
– Water must be transported to
the surface (diffusion is rate limiting)
Factors That Affect Drying
• Product
-- Composition (water, sugar, CHO, Aw) – Amount of product – Size; Surface Area/Volume Ratio – Product Porosity – Pre-treatments of product (blanching, heat treatment)
Factors That Affect Drying
• Drier
– Type of drier – Temperature – Humidity – Pressure (vacuum) – Air flow – Air volume
Drying
• Methods and Techniques:
– Sun or Oven Drying (fruits and nuts)
– Forced-Air Drying
– Spray Drying (milk powder, instant coffee, eggs)
– Roller or Drum Drying (potato flakes, fruit juice)
– Tunnel Drying
– Freeze-Drying
Freeze drying
Sublimation of solid ice to vapor under vacuum
Physical Effects on Foods and Drying
Loss of structural water • Loss of water between and within cells – Shrinkage – Cell collapse – Surface cracking • Concentration of solutes • Case hardening – Formation of a hard outer layer that traps water inside the product
Food Chemistry and Drying
• Chemical reactions can occur at high drying temperatures
• Development of flavors and colors
– Caramelization
– Maillard Browning (when reactants can come together)
– Enzymatic Browning (when PPO is not denatured)
• Denaturation of proteins
• Loss of volatiles
Food Microbiology and Drying
High drying temperatures can kill bacterial populations
• Heat from drying is insufficient to kill bacterial
endospores
• aw can be altered to preserve foods
– The pathogen of concern in foods with low water activity is
Staphylococcus aureus
• aw ³ 0.85 for toxin production by S. aureus
• aw ³ 0.83 for growth of S. aureus
• Most spoilage organisms grow slowly in dried foods
Intermediate Moisture Foods (IMF)
IMF processing is used to create foods with : ü Moisture contents of 15-20% ü aw values of 0.6-0.85 • IMF foods do not require refrigeration to prevent microbial growth • Hurdle Technology (• Water removal (partial) • Solute concentration • Addition of sugar • Salt • Acid • Other preservatives)
Raisin Manufacture
• Harvested grapes are spread on paper sheets for 2-3 weeks. • The moisture content in the grapes drops from 80% to 15%. • The raisins are rolled up and equilibrate for several more days.
Manufacture of Golden Raisins
Sulfiting agents (sulfites) are used to inhibit enzymatic browning. • Forms of sulfites: Sulfur dioxide (SO2) Sodium sulfite (Na2SO3) Sodium metabisulfite (NaS2O5) Potassium metabisulfite (KS2O5) Sodium bisulfite (NaHSO3) Potassium bisulfite (KHSO3) • Sulfites can also inhibit Maillard browning
• Sulfites
A non-immunological food sensitivity
May cause breathing difficulty within minutes
Other symptoms include sneezing, swelling of the
throat, and hives
• Conduction:
heat transfer occurs between molecules (direct contact with a solid or a non-moving liquid)
The heat moves from one particle to the other
by direct contact
• The food does not move
• Convection:
heat transfer occurs because of a moving fluid (liquid or gas)
• Convention involves the movement of the mass
being heated
• In natural convection the heated portion
becomes less dense and rises
• Radiation:
heat transfer occurs because of light waves (electromagnetic energy)
Electromagnetic waves have different energies
depending on their wavelength and frequency
• Radiation does not involve direct contact
between the particles exchanging heat
Purposes of Heating
• To increase shelf-life • To kill or control microorganisms (including endospores) • To control or denature enzymes • To drive off moisture or gases • To alter texture (dissolve solutes, gelatinize starch, denature proteins, breakdown structures) • To inactivate toxins • To develop flavors • To develop colors
• Indirect contact heating:
food or package not in direct contact with the heating medium
• Heat exchanger
• Steam-jacketed kettle
• Direct contact heating:
food or package in direct contact with the heating medium • Retort or pressure cooker • Fryer • Direct steam injection or infusion • Broiler, toaster • Grill • Microwave
Baking and Roasting
• Use of heated air to alter the eating quality of
foods
• Essentially the same unit operation
• Baking: Flour based foods or Fruits
• Roasting: Meats, cocoa and coffee beans,
nuts and vegetables
• Heated air temperatures: 110 - 240 ˚C (230 –
450 ˚F)
• Heat is supplied by a combination of
radiation, convection and conduction
Chemical Changes:
Baking in an Oven
– Evolution and expansion of gases – Solid fats melt – Sugars caramelize – Proteins denature and coagulate – Starch gelatinizes – Moisture evaporates – Flavors develop – Browning occurs
Contrast Baking with
Boiling or Steaming
• Maximum possible
temperature is ≈100°C
• No Maillard Browning
• Inactivation of enzymes
Frying
• Frying is a process of immersing food in hot oil. • Simultaneous heat and mass transfer • High Temperature: 175- 190 ˚C (345-375˚F) • Oil provides uniform contact with a heating medium. • Frying is a “dry” heating method. • Frying only heats the surface of a food. • Conduction to heat the internal part of the food.
The four stages of Frying
- Initial heating
- Surface boiling
– Vaporization of water
– Forced convection of oil - Falling rate
– Rate of evaporation decreases
– Chemical changes occur in the internal regions
of the food
– Crust thickens - Bubble end point
Physical and chemical changes
in the frying oil
- Hydrolysis
- Oxidation
- Polymerization
- Viscosity Increase
- Thickening of oil
- Development of off-flavors
Acrylamide formation
Acrylamide is formed from food
components during heat treatment
• Maillard Reaction between amino
acids (e.g. asparagine) and reducing
sugars
• Asparagine: major amino acid in
potatoes and cereals
• Potential carcinogenic
• High frying temperature and long cooking times
• Storing potatoes in the refrigerator can result in
increased acrylamide formation during cooking
• Soaking raw potato slices in water for
15-30 min before frying helps minimize
acrylamide production
• Cook to a golden yellow color not brown!!
Broiling
• A heating element emits infrared energy. • Broiling rapidly heats the surface of the food and results in Maillard Browning. • Broiling only acts on the surface of a food. • Broiling is distance-dependent.
Microwave Heating
Microwave energy produces heat in materials that absorb it • Wavelengths of 0.025 – 0.75 m and frequencies of 20,000 to 400 MHz • Food applications: approved microwave frequencies are 2,450 and 915 MHz
Understanding Microwave Heating
- Molecular friction of polar molecules
– Microwaves are very effective at heating foods
because foods contain water, which is polar.
– Microwaves create a fluctuating electrical field
inside a microwave oven, which changes direction
2.45 billion times per second (2,450 MHz). - Ionic polarization
– Dissociated ions cause heat when they collide
• Dielectric Properties of foods
Loss factor (εl): Ability of foods to dissipate
electrical energy. The higher the loss factor, the
more energy is absorbed by the food
– Dielectric Constant (εll): Rate at which energy
penetrates a food
Microwave Heating: depth
• Microwaves penetrate most foods (or are absorbed) to a
depth of 5-7 cm (2-3 in)
• The outer surface is heated by the microwaves and is
followed by inward conduction
• Foods do not heat up equally fast in a microwave
oven
• Polar molecules absorb more energy than non-polar
components of foods
Factors Affecting Microwave Heating
Food composition – Dissociated ions affect rate of heating – Some food components absorb microwaves more efficiently • Product density, volume, geometry • Frequency of the microwaves, wattage of the microwaves, power setting
Microbiology and Microwave Heating
• Non-homogeneous heating may lead to survival of
microorganisms in cold spots
• Temperature abuse
is common with foods that are re-microwaved (re-heated,
left on counter, stored in the fridge, reheated,
left on counter, stored in the
fridge…)
– Clostridium perfringens (spore former)
can survive heating, multiply, and will
not be killed if the subsequent heat
treatments are inadequate.
Microwave Heating
• Advantages:
– More energy-efficient – No burn-on to the cooking surface – Desirable chemical changes can still occur (protein denaturation, starch gelatinization, melting of fats…)
Microwave Heating
Disadvantages
– No crisping or crusting – No Maillard Browning – Hot and cold spots – Large quantities of food take much longer to heat
Purposes of Heating
• To increase shelf-life • To kill or control microorganisms (including spores) • To control or denature enzymes • To drive off moisture or gases • To alter texture • To inactivate toxins • To develop flavors • To develop colors
Blanching
• The unit operation in which food is heated rapidly
to a pre-set temperature, held for a pre-set time, and
then cooled rapidly to near ambient temperatures
– Typical temperature/time: ~100°C for 2-3 minutes
– Primary purpose: to destroy enzyme activity
– Not intended to be a sole method
of preservation
- Blanching is a pre-treatment
Blanching enzymes
• Inactivation of enzymes to minimize undesirable changes during processing or storage – Poly Phenol Oxidase (PPO) – Pectinase – Catalase and Peroxidase
Other Effects of Blanching
Reduction in microbial numbers on the surface
• Softening of plant tissues to facilitate filling
– Destruction of cell membranes and cell walls
• Chemical changes to pigments
• Removal of air from intercellular
spaces prior to canning
Pasteurization
- Process invented Louis Pasteur (XIX century)
- Slows food spoilage, destroys enzymes
- Mild heat treatment (below 100 ˚C)
- Heating – Cooling
Pasteurization. Legal Definition
• The process of heating every particle of the food
product to the minimum required temperature
(for that specific product) and holding it
continuously for the minimum required time in
equipment that is properly designed and
operated.
– A less severe heat treatment than sterilization
– Primary purpose: destruction of pathogens
Reasons to Pasteurize
instead of using more intense heating
If a more intense heat treatment would negatively affect product
quality.
• If the main purpose is to destroy pathogens.
• If the main spoilage organisms are not very heat-resistant.
• If the surviving organisms can be controlled by additional
processing (refrigeration).
• If the surviving organisms will be killed or outcompeted
during a fermentation.
Vat Pasteurizer
Heating every particle of the food product • Minimum required temperature • Continuously for the minimum required time
Holding tube
• Fixed volume • Unalterable • Fixed supports • Achieve “hold” by design
Plate pasteurizer
look it up
Time and Temperature Relationships- pasteurizer
Vat is lower temp for longer time than HTST
Heat Sterilization: history
• “Appertization” Nicolas Appert (France. 1750 – 1841) • Food Preservation method • Food in glass jars sealed with cork and sealing wax, heated in boiling water • Jars were replaced by cans in 1810 (Peter Durand, England)
Heat Sterilization definition
Heat sterilization: the unit operation in
which foods are heated at a sufficiently high
temperature and for a sufficiently long time
to destroy microbial and enzymatic activity
– Typical temperature: 121ºC (250ºF)
– Length of heat treatment varies (minimum 15
minutes, or could be hours)
Commercial Sterility
• Describes a product that received a heat treatment sufficient
to result in the destruction of all pathogenic and
vegetative spoilage microorganisms, but which may
contain some spores
– It is impossible to create a sterile product.
– It is possible to predict the survival of a
single microorganism in a food product after
a heat treatment.
–12 D
Location of the Cold Point
In the middle for solids and 1/3 from the bottom for liquids
Factors affecting the length
of heat treatment
Equipment • Method of heating • Temperature Product • Physical state (solid/liquid) • Quality attributes desired • Size of product • Intrinsic (pH) • Composition Package • Size/Volume • Amount of product • Packaging material Microorganism • Type (heat resistance) • Size of population
Microbial growth curve
Lag phase (flat), log phase (exponential), stationary phase (flat), and death phase (decline)
Thermal Destruction of Microorganisms
• The destruction of microorganisms occurs logarithmically • D-values are given for specific temperatures, microorganisms and foods. • Commercial Sterilization: D121˚C (D250˚F) • D values for Enzymes, pigments and Vitamins
• D-value:
decimal reduction time; the time (at a specified temperature) required to result in a one-log reduction in a bacterial population
One D-value =
time to reduce a bacterial population by one log
103 –> 102
time to destroy 90% of a bacterial population
1,000 –> 100
Heat Sterilization and Acidity: low acid food
Heat treatment to destroy
Clostridium botulinum;
requires a retort (12D) - pressure cooker
Heat Sterilization and Acidity: high acid foods
Heat treatment to inactivate
enzymes; less severe heat
treatment, can be done with
boiling water (5 D)
Heat treatment
Time (minutes) required to destroy viable spores of
Clostridium botulinum in different foods at various pH levels
• Z-value
temperature change required to change the D value by a factor of 10 (one log cycle)
• The Z-value relates to the thermal resistance of the
microorganisms
• Used to calculate a thermal process of equivalency.
• Thermal Death Time (TDT) on y-axis: 3D, 5D, 12D….
Effect of heat on nutritional and sensory
characteristics of food
• Destruction of Vitamins, aroma compounds and pigments
• Maillard Browning
• Enzymes (PPO, catalase, pectinase) inactivation to minimize
undesirable changes during storage
• Nutritional and sensory characteristics are better retained by
using High Temperatures and Shorter Times (Quick
blanching, HTST, UHT)
HTST Pasteurization
High temperature, short time. Kills pathogens without destroying vitamins
UHT Processing
• Ultra-High Temperature:
ü Liquid products: milk, juices, cream
ü Foods with small particles: baby foods, tomato
products, soups
ü Larger particles: stews
• Temperatures in the range 135-140 °C, for a few
seconds.
• Heat sterilization followed by aseptic filling
• Long shelf life (6 months, without refrigeration)
Canning
• Canning can be a safe and economical way to
preserve quality food at home.
• Canning homegrown food may save you half the cost
of buying commercially canned food
How canning preserves foods
• The high percentage of water in most fresh foods
makes them very perishable.
• They spoil or lose their quality for several reasons:
- Growth of undesirable microorganisms
- Activity of food enzymes,
- Reactions with oxygen,
- Moisture loss.
• Proper canning practices include:
- Carefully selecting and washing fresh food
- Peeling
- Hot packing
- Adding acids (lemon juice or vinegar)
- Using acceptable jars and self-sealing lids
- Processing jars in a boiling-water or pressure
canner for the correct period of time.
Ensuring safe canned foods
• Growth of the bacterium Clostridium botulinum in
canned food may cause botulism
• To germinate and produce toxin, Clostridium
botulinum spores need the following conditions :
- A moist, low-acid food (pH > 4.6)
- A temperature between 40° and 120°F
- Less than 2 percent oxygen.
Low Acid Foods
– Generally all vegetables – Meats – Poultry – Seafood – Soups – Mixed canned foods (low acid + acid) However, if pH < 4.6 = acidified foods
Canning Low Acid Foods
• T ≥ 240 ˚F needed • Only safe way to can low-acid foods is with pressure: – 10 psig = 240 ˚F at sea level. – 15 psig = 250 ˚F at sea level.
High Acid Foods
pH 4.6. or lower • Use boiling water canner • Temperature reaches 200-212ºF • Tomatoes, jams, fruits, BBQ sauce • Some tomatoes have pH values slightly above 4.6 and must be acidified with lemon juice or citric acid
Containers for canning
Mason jars • 4, 8, 16, and 32 oz. common • 64 oz. only for juice • Mayo jars okay • 2-piece metal lids
Raw Pack vs. Hot Pack
Raw pack: add very hot canning liquid into jar after food has been tightly packed in Disadvantages: • Floating food • Air bubbles • Discoloration over time Hot pack: Boil food for 3-5 mins then pour into jars Disadvantage: • Texture loss
Two Piece Metal Lids
- Always use new lids
- Hand tighten
- Too loose (leaks)
- Too tight (no vacuum)
Boiling Water Canner
- Aluminum or porcelain covered steel
- Flat bottom
- Jar rack or bottom rack needed
- Steam canners not recommended
- Start timer once water boils vigorously
Pressure Canner
• Aluminum or steel, lid with gasket • Weighted or dial gauge (check dial gauge annually) • Pressure safety valve • Jar rack • Begin to time when recommended pressure is reached
Testing Seals
- If the seal springs back up it is broken
- Lid should be concave (curved in).
- Flat or bulging: lid is not sealed
Spoilage of Canned Foods
• Check for swollen lid or seal breakage.
• When opening look, smell, and listen for anything unusual:
- off smells
- spurting liquid
• At low temperature:
üMolecular mobility is depressed üChemical and biological processes are slowed down • Low Temperature does not destroy microorganisms or enzymes !!!
Refrigeration, Chilling and Freezing
• Refrigeration retards spoilage • Can not improve the initial quality of food • Not a method of “permanent preservation” • Often combined with other preservation processes
Removal of thermal energy
To prolong product quality • To increase shelf-life • To slow post-harvest or post-slaughter physiological changes • To slow microbial growth • To slow enzyme activity • To make some foods possible
Food Preservation
at Low Temperatures: specific temps
• Chilling/ Refrigeration
ü Above freezing point (0 - 8 ˚C)
• Freezing
ü Below freezing point (below -18 ˚C)
Methods of Cooling
• Chilling in Air
• Indirect Contact Chilling
• Direct Contact or
Immersion Chilling
Chilling in Air
• Still air
- High-velocity air – Wind speeds up to
30-40 mph
• Fluidized bed (Freezing)
Mechanical Refrigeration Cycle
Refrigerant comes in in the back of fridge from the compressor and evaporates due to the heat from the food. The vapor then goes through a condenser that releases heat and it returns to a liquid
Deterioration of Foods During
Refrigerated Storage
• Chill injury of fresh produce • Flavor migration between foods • Nutrient losses • Retrogradation of starch (syneresis) • Oxidative rancidity of lipids • Enzymatic reactions (breakdown of carbohydrate or protein structures, etc.) • Water migration (related to % relative humidity) • Growth of spoilage organisms
Chill (cold) injury
Physiological damage many vegetables suffer as a consequence of their exposure to low (but not freezing) temperatures ü Distinct from freezing injury ü More common in tropical and sub tropical plants ü Poor ripening, pitting, collapse of structure ü Off flavors, rotting
Microbiology and
Low Temperatures
Most spoilage microorganisms and pathogens do not
grow (or grow slowly) at refrigeration temperatures.
• The main spoilage organism of concern at low
temperatures is Pseudomonas.
– Pseudomonas counts can increase by a factor of 10 in 24 hours at 7°C.
– Pseudomonas produces heat-stable proteases and lipases that are a concern in foods.
Freezing point depression
- A colligative property associated with the number of dissolved molecules.
- The freezing point of a liquid is depressed when another compound is added
- A solution has a lower freezing point than a pure solvent (water).
Cooling process
- Cooling to “freezing point”
- Supercooling until…
- NUCLEATION!
- Heat is released and local
temperature increases - Further cooling will cause
more ice to grow on existing
crystals
As foods freeze:
– Ice is formed
– Free water becomes unavailable
– Remaining solutes become concentrated
– Freezing point of the unfrozen food is depressed
Freezers used in the food industry
- Tunnels
- Plate freezers
- Blast freezers
- Pneumatic conveyors
- Ice cream freezers
High-Velocity Air with a Conveyor
look up
Blast Chiller/Freezer
look up
Fluidized Bed Freezing
- IQF: Individually Quick Frozen
- Each individual piece of food is frozen separately from all the others
- Food particles stay separate after they’ve been frozen.
Direct Contact or Immersion
• Direct contact of the food with a cold refrigerant
• Submerging a food or spraying cold liquid onto the food or package
• Allows for intimate contact with the refrigerant
• Cold water spray
• Submerging in ice water or cryogenic fluid (Liquid
Nitrogen, Liquid CO2)
• Storing on ice
Indirect Contact Cooling
The food or the package is in contact with a surface that is cooled by a refrigerant, but the food or package does not contact the refrigerant directly
– Plate heat exchanger
– Tubular heat exchanger
Plate Freezers
- Used to freeze food in blocks
- Seafood and Meat products
- Chopped or Sliced Vegetables
Physical and Chemical Effects of
Freezing on Foods
• Water expands during freezing • Dissolved solutes concentrate – Proteins can denature – Carbohydrates can come out of solution – Acid concentrations increase – Gas pressure increases • Freezer burn • Growth of ice crystals during temperature fluctuations (heat shock)
• Freezer burn
Evaporation of water from the food surface
• Heat shock:
Intermittent thawing and freezing of a product, as often occurs during temperature cycling
– It does not require a total change of ice to liquid
The Rate of Freezing
• Rapid freezing results in more, homogeneously
dispersed ice nuclei.
• Rapid freezing is essential to preserving food quality
Microbiology and Freezing
- Freezer temperatures do not destroy pathogenic or spoilage microorganisms
- When frozen foods are thawed the surface of the food warms enough for microorganisms to grow and multiply.
Stabilizers
• Guar gum • Locust bean gum • Sodium Alginate • Xanthan gum • Gelatin • CarboxyMethylCellulose - Add Viscosity - Control Ice Crystal Size - Limit ice recrystallization during storage - Without them, ice cream would become coarse and icy very quickly (migration of free water and the growth of existing ice crystals)
Emulsifiers
• Egg yolks
• MAG
• DAG
• Polysorbate 80
ü Aid in developing the appropriate fat structure and air
distribution necessary for the smooth eating and good
meltdown characteristics desired in ice cream
Standard of identity for ice cream
at least 10% milk fat and no more than 100% overrun
Equipment Needed for making ice cream
- Measuring – Weight or Volume
- Blending Vats
- Powder Blender
- Pasteurizer
- Homogenizer
- Freezer
- Aging/Hardening
- Storage
Blending
• Uniform composition
• Agitator speed
• Dry ingredients must be
wetted and dispersed
Freezing ice cream
• Temperature
Change
• Air Incorporation
• Water Freezing
Batch freezer
üSmall-scale operations
ü10-40 qt barrel size
ü5-15 min/batch
-Scraped surface heat exchanger
Continuous freezer
- Scalable, barrel size, number of barrels
- Rapid freezing
- Improved overrun control
Overrun
Refers to degree of air added to the mix during ice cream making
• Calculated as the percentage volume increase, mix versus product
• Example: 1 gallon of mix yielding 2 gallons of product is 100% overrun
Overrun equations
% Overrun = [(V product - V mix) /V mix] x100
% Overrun = [(W mix - W same V of product)/ W same V of product] x100
Hardening of ice cream
Ice cream is packaged and placed into a blast freezer (-30° to -40° C) where most of the remainder of the water is frozen.
• Below about -25° C, ice cream is stable for indefinite periods without danger of ice crystal growth
• Ice crystals are formed in our home freezer!!
Food Additives. Definition
any substance, the intended use of which results or may
reasonably be expected to result, directly or indirectly, in its becoming a component of or otherwise affecting the
characteristics of any food (including any substance
intended for use in producing, manufacturing, packing,
processing, preparing, treating, transporting or holding a
food; and including any source of radiation intended for
any such use)…
What is a food additive?
A chemical or other substance that becomes a
part of a food product either added
intentionally or accidentally
• Adulteration
(illegal) is the deliberate addition of
cheap ingredients to a food to make it appear to be high
quality
Food additive approval
• Most food additives are intentional additives and
must receive approval from FDA before they can be
used
• Indirect additives are contaminants (accidentally get
into food)
Food Additives. Requirements
• The safety of a food additive must never be in doubt
• Must do its stated function
• Must not significantly diminish nutritional value
• Not be used to compensate for improper
manufacturing practices or inferior product
characteristics
• Should be detectable by a defined method of analysis
Processing Aids
Defined by FDA (21 CFR) as substances added to a food:
1) during processing but removed before it is packaged in
its finished form
2) during processing and converted into constituents
normally present in the food (do not significantly
increase the amount of the constituents naturally found)
3) for their technical or functional effect in the processing and are present in the finished food at insignificant levels.
Processing Aids Regulation
Regulated by FDA in the same
manner as any other substance added to food
• Are not required to be declared in the ingredients list on
the food label because:
1) They have no technical or functional effect in the
finished food
2) They are either not present or are present at only
insignificant levels in the finished food
Processing Aids examples
Fruit and vegetable washes • Organic acids • Chlorine washes Joining agents and Enzymes • Rennet • Transglutaminase (”meat glue”) Control bacteria in chill water • Chlorine gas • Ozone Strengthening agents • Sodium stearoyl lactylate
Food additive examples
• Any substance used in the production, treatment,
packaging, transportation or storage of food (ingredients)
• Radiation used to destroy microorganisms is also an additive
• Some food additives have been in use for centuries
– Salt
– Herbs and spices
– Sugar
– Vinegar
– MSG
Purposes of Food Additives
• Foods are subjected to: - Temperature changes - Oxidation - Spoilage microorganisms - Humidity - UV radiation • Additives are key to maintaining food quality
Types of Food Additives
• Leavening agents • Lubricants and release agents • Non-nutritive sweeteners • Nutrient supplements • Nutritive sweeteners • Oxidizing and reducing agents • pH control agents • Processing aids • Propellants, aerating agents, and gases • Sequestrants • Solvents and vehicles • Stabilizers and thickeners • Surface-active agents • Surface-finishing agents • Synergists • Texturizers • Anticaking agents and free-flow agents • Antimicrobial agents • Antioxidants • Colors and coloring adjuncts • Curing and pickling agents • Dough strengtheners • Drying agents • Emulsifiers and emulsifier salts • Enzymes • Firming agents • Flavor enhancers • Flavoring agents and adjuvants • Flour treating agents • Formulation aids • Fumigants • Humectants
• Curing agents
– Sodium nitrite (meats)
– Help retain the pink color of cured meats
– Act as preservatives
– Nitrosamines can be formed when nitrites react with
protein breakdown products (potentially toxic)
• Nutritional additives
– Vitamin D is added to milk – Vitamin B and iron to baked products –Enrichment: addition of nutrients loss during processing – Fortification: addition of nutrients, either absent or present in insignificant amounts
Safety- food additives
• Adverse Reaction Monitoring System (ARMS)
– 1985: FDA created a formal system for monitoring
adverse reactions to food additives
– Passive system: reports filed by individuals or by
medical professionals
Top ARMS reports
Olestra 18,309* 53.8%
Aspartame 7,335** 21.6%
Sulfiting agents 1,141 3.40%
MSG 905 2.70%
Disintegrating
Operations which subdivide large pieces of food into smaller units or particles are classified as disintegrating. It may involve cutting, grinding, pulping, homogenizing, and so on.
Oxidative rancidity
is associated with the degradation by oxygen in the air. Via a free radical process, the double bonds of an unsaturated fatty acid can undergo cleavage, releasing volatile aldehydes and ketones. Oxidation primarily occurs with unsaturated fats.
Pulse net
DNA fingerprinting, or patterns of bacteria making
people sick, to detect thousands of local and multistate outbreaks.
FoodNet
infections diagnosed by laboratory testing of
samples from patients 10 state health departments, the U.S. Department of Agriculture’s Food Safety and inspection service, and the FDA
Code of federal regulations verse the food code
Code of federal regulation is federal law and is permanent and consists of 50 titles. The food code is a guideline (not law) based on science
HACCP
Hazard analysis and critical control point
- Conduct a hazard analysis
- Determine the CCPs
- Establish critical limits
- Establish monitoring procedures
- Establish corrective actions
- Establish verification procedures
- Establish record-keeping and documentation procedures
* Specific to hazards that are inherent to the food
HARPC
Hazard analysis and risk-based preventive control- new approach and more comprehensive, includes allergy reduction and disaster plan, everything must be written
Sensory tests and when we use them
Affective (consumer): measure preference of liking (100 people)
Descriptive: quantify differences between samples. Describes various flavor and texture profiles. Done by trained panelist and used to see how much product tastes like it should and is quality (10-15 panelists)
Discrimination: Is there a difference? (paired comparison and duo-trio test, and triangle test). Used to compare product to competitors product (30 people)
