Final Flashcards
1
Q
Food Processing:
A
the conversion of raw animal
and plant tissue into forms that are convenient and
practical to consume.
2
Q
Food Preservation:
A
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.
3
Q
Purposes of Food Processing
A
• 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
4
Q
Processed Foods
A
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.
5
Q
Processing effect on nutritional content
A
• Processing of foods, including the addition of
ingredients, may reduce, increase, or leave
unaffected the nutritional characteristics of
raw agricultural commodities.
6
Q
Processed Foods. Categories
• According to the International Food Information
Council:
A
1) Minimally Processed Foods
2) Foods Processed for Preservation
3) Mixture of Combined Ingredients
4) Ready-to-eat Foods
5) Convenience
7
Q
Minimally Processed Foods
A
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
8
Q
Foods Processed for Preservation
A
• Processed to maintain freshness and nutrients
ü Canned fruits/vegetables
ü Frozen fruits /vegetables
9
Q
Mixture of Combined Ingredients
A
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
10
Q
Ready-to-eat Foods
A
• 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
11
Q
Convenience Foods
A
• Packaged to keep fresh and save time • More “heavily” processed ü Frozen meals ü Frozen Pizza ü Microwaveable dinners
12
Q
Processed Foods. Negative Aspects
A
Controversial additives • GMOs • trans fats • Saturated fats • Added sugar • Sodium • Caloric intake
13
Q
Processed Foods. Positive Aspects
A
Food Safety and Preservation • Removal of anti-nutritional factors • Foods for people with special needs • Fortification and Enrichment • Affordable, Convenient
14
Q
Why is it important to understand Food Processing?
A
• Food processing methods are used to preserve and
create foods.
• If you understand how something functions, you can
improve product quality
15
Q
Food Processing and
Food Chemistry
A
• 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
16
Q
Food Processing and
Food Microbiology
A
• 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
17
Q
Unit Operations in Food Processing
A
• 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
18
Q
Unit Operations examples
A
• Materials handling • Cleaning • Separating • Disintegrating • Pumping • Forming • Mixing v Heat exchange v Evaporation v Drying v Packaging v Non-thermal methods
19
Q
Materials Handling
A
• Handling raw or partially processed materials
• Important considerations related to product
quality
20
Q
Cleaning and Sanitation
A
• The equipment used will vary depending on
what you want to clean
– Water
– Surfaces of foods
– Surfaces of equipment or processing facilities
21
Q
Clean:
A
Remove soil (matter out of place)
22
Q
Sanitize:
A
Reduce microbial contamination to a safe level
23
Q
Disinfect:
A
Kills 100% of vegetative cells, may not kill bacterial spores and viruses
24
Q
• Sterilize:
A
Complete destruction of all forms of life (bacteria, bacterial spores, fungi, viruses)
25
Soils in food processing facilities are composed of
| deposits of
fat, carbohydrates, proteins, and mineral
| deposits
26
• 4 Factors of Cleaning:
– Time
– Action
– Concentration
– Temperature
27
Spray ball cleaning takes a lot of
time and chemical action
28
Rotary wetting cleaning takes a lot of
time and chemical action
29
Boiling out/fill and drain takes a lot of
time, chemical action and temperature
30
Size Reduction
• Reductions of particle size (cutting, grinding, pulping,
chopping, dicing, grating, homogenizing)
• Equipment selection can play a role in product quality
31
Pumping
```
Moving foods from one point to another
• Important characteristics in selecting
pumps:
– Minimize product damage
– Ease of cleaning
```
32
Mixing
All mixers do “work” on a product and can
| affect product quality
33
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
```
34
Process flow diagrams
| • Basic Shapes
– Arrows indicate the Direction of Flow
– Parallelograms indicate Inputs or Outputs
– Diamonds indicate Decision Forks
– Rectangles indicate Processes
35
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
36
• Concentration and Evaporation:
– The partial removal of water from
foods to increase its total solids
content
37
• Drying:
– An extensive approach to moisture
removal in which product moisture
is reduced to a few percent
38
Concentration and Evaporation
| • Methods and Techniques
– Open kettles or pots
– Vacuum evaporator
– Freeze concentration
39
Volatile partitioning
Volatile compounds are compounds that due to their
high vapor pressure and low water solubility enter the
gas phase (air)
40
– 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
41
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)
42
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)
```
43
Factors That Affect Drying
| • Drier
```
– Type of drier
– Temperature
– Humidity
– Pressure (vacuum)
– Air flow
– Air volume
```
44
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
45
Freeze drying
Sublimation of solid ice to vapor under vacuum
46
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
```
47
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
48
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
49
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)
```
50
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.
```
51
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
```
52
• Sulfites
A non-immunological food sensitivity
May cause breathing difficulty within minutes
Other symptoms include sneezing, swelling of the
throat, and hives
53
• 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
54
• 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
55
• 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
56
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
```
57
• Indirect contact heating:
food or package not in direct contact with the heating medium
• Heat exchanger
• Steam-jacketed kettle
58
• 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
```
59
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
60
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
```
61
Contrast Baking with
| Boiling or Steaming
• Maximum possible
temperature is ≈100°C
• No Maillard Browning
• Inactivation of enzymes
62
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.
```
63
The four stages of Frying
1. Initial heating
2. Surface boiling
– Vaporization of water
– Forced convection of oil
3. Falling rate
– Rate of evaporation decreases
– Chemical changes occur in the internal regions
of the food
– Crust thickens
4. Bubble end point
64
Physical and chemical changes
| in the frying oil
* Hydrolysis
* Oxidation
* Polymerization
* Viscosity Increase
* Thickening of oil
* Development of off-flavors
65
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!!
66
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.
```
67
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
```
68
Understanding Microwave Heating
1. 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).
2. Ionic polarization
– Dissociated ions cause heat when they collide
69
• 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
70
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
71
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
```
72
Microbiology and Microwave Heating
• Non-homogeneous heating may lead to survival of
| microorganisms in cold spots
73
• 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…)
74
– Clostridium perfringens (spore former)
can survive heating, multiply, and will
not be killed if the subsequent heat
treatments are inadequate.
75
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…)
```
76
Microwave Heating
| Disadvantages
```
– No crisping or crusting
– No Maillard Browning
– Hot and cold spots
– Large quantities of food
take much longer to heat
```
77
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
```
78
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
79
Blanching enzymes
```
• Inactivation of enzymes to minimize
undesirable changes during
processing or storage
– Poly Phenol Oxidase (PPO)
– Pectinase
– Catalase and Peroxidase
```
80
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
81
Pasteurization
* Process invented Louis Pasteur (XIX century)
* Slows food spoilage, destroys enzymes
* Mild heat treatment (below 100 ˚C)
* Heating – Cooling
82
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
83
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.
84
Vat Pasteurizer
```
Heating every particle
of the food product
• Minimum required
temperature
• Continuously for the
minimum required
time
```
85
Holding tube
```
• Fixed volume
• Unalterable
• Fixed supports
• Achieve “hold”
by design
```
86
Plate pasteurizer
look it up
87
Time and Temperature Relationships- pasteurizer
Vat is lower temp for longer time than HTST
88
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)
```
89
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)
90
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
91
Location of the Cold Point
In the middle for solids and 1/3 from the bottom for liquids
92
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
```
93
Microbial growth curve
Lag phase (flat), log phase (exponential), stationary phase (flat), and death phase (decline)
94
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
```
95
• D-value:
decimal reduction time; the time (at a specified temperature) required to result in a one-log reduction in a bacterial population
96
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
97
Heat Sterilization and Acidity: low acid food
Heat treatment to destroy
Clostridium botulinum;
requires a retort (12D) - pressure cooker
98
Heat Sterilization and Acidity: high acid foods
Heat treatment to inactivate
enzymes; less severe heat
treatment, can be done with
boiling water (5 D)
99
Heat treatment
Time (minutes) required to destroy viable spores of
| Clostridium botulinum in different foods at various pH levels
100
• 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….
101
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)
102
HTST Pasteurization
High temperature, short time. Kills pathogens without destroying vitamins
103
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)
104
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
105
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.
106
• 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.
107
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.
108
Low Acid Foods
```
– Generally all vegetables
– Meats
– Poultry
– Seafood
– Soups
– Mixed canned foods
(low acid + acid)
However, if pH < 4.6 = acidified foods
```
109
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.
```
110
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
```
111
Containers for canning
```
Mason jars
• 4, 8, 16, and 32 oz.
common
• 64 oz. only for juice
• Mayo jars okay
• 2-piece metal lids
```
112
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
```
113
Two Piece Metal Lids
* Always use new lids
* Hand tighten
* Too loose (leaks)
* Too tight (no vacuum)
114
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
115
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
```
116
Testing Seals
* If the seal springs back up it is broken
* Lid should be concave (curved in).
* Flat or bulging: lid is not sealed
117
Spoilage of Canned Foods
• Check for swollen lid or seal breakage.
• When opening look, smell, and listen for anything unusual:
- off smells
- spurting liquid
118
• At low temperature:
```
üMolecular mobility is depressed
üChemical and biological processes
are slowed down
• Low Temperature does not
destroy microorganisms or enzymes !!!
```
119
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
```
120
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
```
121
Food Preservation
| at Low Temperatures: specific temps
• Chilling/ Refrigeration
ü Above freezing point (0 - 8 ˚C)
• Freezing
ü Below freezing point (below -18 ˚C)
122
Methods of Cooling
• Chilling in Air
• Indirect Contact Chilling
• Direct Contact or
Immersion Chilling
123
Chilling in Air
• Still air
- High-velocity air – Wind speeds up to
30-40 mph
• Fluidized bed (Freezing)
124
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
125
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
```
126
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
```
127
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.
128
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).
129
Cooling process
1. Cooling to “freezing point”
2. Supercooling until...
3. NUCLEATION!
4. Heat is released and local
temperature increases
5. Further cooling will cause
more ice to grow on existing
crystals
130
As foods freeze:
– Ice is formed
– Free water becomes unavailable
– Remaining solutes become concentrated
– Freezing point of the unfrozen food is depressed
131
Freezers used in the food industry
* Tunnels
* Plate freezers
* Blast freezers
* Pneumatic conveyors
* Ice cream freezers
132
High-Velocity Air with a Conveyor
look up
133
Blast Chiller/Freezer
look up
134
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.
135
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
136
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
137
Plate Freezers
* Used to freeze food in blocks
* Seafood and Meat products
* Chopped or Sliced Vegetables
138
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)
```
139
• Freezer burn
Evaporation of water from the food surface
140
• 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
141
The Rate of Freezing
• Rapid freezing results in more, homogeneously
dispersed ice nuclei.
• Rapid freezing is essential to preserving food quality
142
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.
143
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)
```
144
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
145
Standard of identity for ice cream
at least 10% milk fat and no more than 100% overrun
146
Equipment Needed for making ice cream
1. Measuring – Weight or Volume
2. Blending Vats
3. Powder Blender
4. Pasteurizer
5. Homogenizer
6. Freezer
7. Aging/Hardening
8. Storage
147
Blending
• Uniform composition
• Agitator speed
• Dry ingredients must be
wetted and dispersed
148
Freezing ice cream
• Temperature
Change
• Air Incorporation
• Water Freezing
149
Batch freezer
üSmall-scale operations
ü10-40 qt barrel size
ü5-15 min/batch
-Scraped surface heat exchanger
150
Continuous freezer
* Scalable, barrel size, number of barrels
* Rapid freezing
* Improved overrun control
151
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
152
Overrun equations
% Overrun = [(V product - V mix) /V mix] x100
| % Overrun = [(W mix - W same V of product)/ W same V of product] x100
153
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!!
154
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)…
155
What is a food additive?
A chemical or other substance that becomes a
part of a food product either added
intentionally or accidentally
156
• Adulteration
(illegal) is the deliberate addition of
cheap ingredients to a food to make it appear to be high
quality
157
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)
158
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
159
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.
160
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
161
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
```
162
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
163
Purposes of Food Additives
```
• Foods are subjected to:
- Temperature changes
- Oxidation
- Spoilage microorganisms
- Humidity
- UV radiation
• Additives are key to maintaining food quality
```
164
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
```
165
• 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)
166
• 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
```
167
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
168
Top ARMS reports
Olestra 18,309* 53.8%
Aspartame 7,335** 21.6%
Sulfiting agents 1,141 3.40%
MSG 905 2.70%
169
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.
170
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.
171
Pulse net
DNA fingerprinting, or patterns of bacteria making
| people sick, to detect thousands of local and multistate outbreaks.
172
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
173
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
174
HACCP
Hazard analysis and critical control point
1. Conduct a hazard analysis
2. Determine the CCPs
3. Establish critical limits
4. Establish monitoring procedures
5. Establish corrective actions
6. Establish verification procedures
7. Establish record-keeping and documentation procedures
* Specific to hazards that are inherent to the food
175
HARPC
Hazard analysis and risk-based preventive control- new approach and more comprehensive, includes allergy reduction and disaster plan, everything must be written
176
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)
