kuliah 4 food processing 2011

7/30/2019 Kuliah 4 Food Processing 2011

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Food PreservationThrough Processing

Freezing, Drying, Canning,Fermentation and

Irradiation


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WHY PROCESS FOODS?

1. EXTEND SHELF LIFE

2. MAINTAIN SENSORY PROPERTIES

3. MAINTAIN OR IMPROVE NUTRITIVEPROPERTIES

4. ENSURE SAFETY

5. BOTTOM LINE: $$ (ECONOMICVALUE)


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Moldy oranges

Potato blight

Moldy cheese

Food Spoilage
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The Objective!

Goal for Preserving Food:

Minimize or _____________ theactivity of microorganisms, enzymes,and chemical reactions that cause

food spoilage or foodborne illness

How? By making conditions forchemical/biochemical reactions

_______________, and/or by inhibiting

microbial growth

Enzymatic

browning is

caused by an

oxidase enzyme

in apples,

bananas,avocadoes, and

other foods


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Food Spoilage andFoodborne Illness

(part 2)

Foodborne Illness:

Mostly caused by bacteria

Some microbes cause human illness by

producing toxins, but may not produce foodspoilage

Over 76,000,000 Americans get some form of

foodborne illness every year from intestinal distress to death


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Historical Methods of FoodPreservation

Primitive and tedious methods

DryingSalting

SugaringPickling


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Drying

Used to preserve fruit,vegetables, meats, and fish.

Mainly used in the southwarmer climate.

Causes the loss of many naturalvitamins.


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Pickling

Fermenting

Used to preserve vegetables.Use mild salt and vinegar brine.

Increases the salt content andreduces the vitamin content of thefood.

Oldest form of food preservation.


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Current Technologies in FoodPreservation


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Methods ofFood

Preservation

Canning

Freezing

Drying

Curing/

SmokingFermenting

Pickling

Jams/

Jellies


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PRESERVATION OF FOODS BYLOWERING THE TEMPERATURE

THEORY - LOWERING THE STORAGE

TEMPERATURE OF THE FOODWILL REDUCE OR PREVENT

SPOILAGE BY MICROORGANISMS

AND/OR CHEMICAL REACTIONS.


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NOTE:TECHNOLOGY IS RELATIVELY NEW

ENERGY INTENSIVE

I. REFRIGERATION - Temperaturestypically between 45 - 32 F (7.2 - 0 C).Prefer below 38 F.

THEORY - LOWER TEMPERATURE WILL

REDUCE SPOILAGE.


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ALTER GASES: Controlled atmospherestorage: increase carbon dioxide andlower oxygen to slow respiration oftissues or microorganisms in fruits,vegetables, nuts, meats and eggs.

ISSUE - Spoilage organisms andchemical reactions can occur atrefrigerator temperatures. But at aslower ratee.g. lower shelf life.


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TRADITIONAL REFRIGERATED FOODS

1. Fresh foods (unprocessed), fruits andvegetables, (fresh meats, poultry, fish)

2. Processed foods: doughs, minimally

processed vegetables3. Refrigerated foods containing fruits and

vegetables: entrees, dinners, salads.(Pasteurized dairy products curedmeats)


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WHY DO WE SEE MORE NEWREFRIGERATED FOODS ENTERINGTHE MARKETPLACE THAN OTHERFOODS?

1. Consumer demand for high qualityfoods:

A. Typically less change in the qualityof food product.

B. Convenient - shorter cook times


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Cold:

Most microbial growth slows attemperatures under 50 F. Some bacteria,

called psychrophiles, actually thrive atrelatively low temperatures and willcontinue slow growth. Foods frozen at less

than 14 F usually do not have any freewater, so these foods also benefit fromlow water activity to help protect againstmicrobial growth. Freezing may kill somebut not all of the microorganisms.


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Refrigeration:

some fresh produces can rapidly deteriorate

under unrefrigeration, which affect the EPcost to be greater. Some precuts andconvenience fresh produces such as saladgreens should be delivered at temperature of

approximately 34 F to 36 F.


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Refrigeration

Early time, ice and snow wasused.

Now the most popular method offood preservation.

85% of all foods are refrigerated.Greatly changed our eating

habits.


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Most convenient, easiest, fastestmethod

Low temperatures slow down chemical/biochemical

reactions Inhibit microbial growth

Freezing fruits is sooooo easy! Spread out clean dry berries on a

cookie sheet, put into the freezer;

when theyre frozen, put into afreezer bag

Stone fruits like peaches can bepacked in syrup in Tupperware orplastic bags OR dry-packed aftersprinkling with sugar & freezing inbags or boxes

Freezing


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WHY FREEZE?

1. In general frozen foods are betternutritionally and organoleptically thanother processed foods.

2.

Long shelf life3. Convenient - shorter cook times

DISADVANTAGE:

Energy intensive


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ISSUES W/ FROZEN FOODS

1. Chemical reactions can occur inunfrozen water.

A. Some foods blanched or sulfited

before freezing.B. Vacuum packaging to keep out

oxygen.


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ISSUES W/ FROZEN FOODS (cont.)

2. Undesirable physical changesA. Fruits and vegetables lose crispness

B. Drip loss in meats and colloidal type

foods (starch, emulsions) Freeze product faster

Control temperature fluctuations instorage.

Modify starch, egg systems, etc.


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UNDESIRABLE PHYSICAL CHANGES(cont.)

C. Freezer burn

Package properly

Control temperature fluctuations instorage.

D. Oxidation

Off-flavors Vitamin loss

Browning

E. Recrystallization


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TYPES OF FREEZING:

1. AIR FREEZING - Products frozen byeither "still" or "blast" forced air.

cheapest (investment)

"still" slowest more product changes

"blast" faster, more commonly used

2. INDIRECT CONTACT - Food placed

in direct contact with cooled metalsurface.

relatively faster

more expensive


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TYPES OF FREEZING (cont.):

3. DIRECT CONTACT - Food placed indirect contact w/refrigerant (liquidnitrogen, "green" freon, carbon

dioxide snow) faster

expensive

freeze individual food particles


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SLOW FREEZING VS FAST FREEZING

Slow freezing

Large crystal growth Cell dehydration

Fast freezing

Small crystal growth

Best for quality foods


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Different ways to Freeze

Plate Freezing

Box and plates Birdseye

Scraped surface Ice Cream

Immersion

In safe liquids that remove heat

Cryogenic liquid sprays

Liquid N2, CO2, Freon


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Affect of Freezing on Nutrition

If frozen food is handled properly, mostwater soluble vitamins will remain

available but some degradation will occurover time

The real problems occur when foods gothrough freeze-thaw.

This affects quality characteristics as wellas nutritional value


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Drying

The dehydration of foods

Removing 95%-99% of water from aproduct by means of various process

Processes include: Tunnel Drying vegetables, fruits

Drum Drying potato flakes

Spray Drying coffee

Freeze Drying drinks, instant meals


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DRYING

Probably oldest form of food preservation

Most widely used preservative method

THEORY: REDUCING THE AMOUNT OFFREE WATER WILL PREVENTMICROBIAL AND CHEMICAL SPOILAGE


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DRY FOODS - Aw OF 0.2 TO 0.6

< 0.6 prevents microbial growth

0.2 - 0.3 prevents many chemicalreactions.

INTERMEDIATE MOISTURE FOODS

0.8 to 0.9 Use mold inhibitors


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NUTRIENT CHANGES AND OVERALLQUALITY

1. PROTEINS: Digestibility can be reduced (high

temperatures)

2. LOSS IN VITAMINS Water soluble

Fat soluble

3. FATS: Potential for oxidative rancidity

increases (high temperatures)


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NUTRIENT CHANGES AND OVERALLQUALITY (cont.)

4. CARBOHYDRATES:

Enzymatic and nonenzymatic browning.

Carmelization increases Prevent or reduce color changes:

sulfites

blanching5. SHAPE CHANGES


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STORAGE (KEEP OUT O2 AND LIGHT)

1. Air space (vacuum)

2.

Reduce exposure to light3. Good moisture barrier


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TYPES OF DRYING (cont.)

B. HOT AIR DRYING More efficient/control Lower nutrient loss More expensive

Products: dried vegetables, pasta, somefruits

C. DRUM DRYING More efficient than hot air Lower nutrient loss Cost about equal with air Products: potato pastes & slurries


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D. SPRAY DRYING Low nutrient loss More expensive than drum or air drying Good control/efficiency

Use only for liquids Products: milk, instant tea and coffee

E. PUFF DRYING: PRESSURE DROP

Using heating systems; Air poppers;Extruders.


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G. HOT OIL Good heat transfer Good control Distinctive flavor/aroma

Oil uptake, mouth feel/hand/calories Oxidation, free fatty acid,

and flavor concern Products: potato chips, french fries, onion

rings, some popcorn, doughnuts, somespecialty meats (different countries)


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H. CHEMICAL DRYING Salt Sugars

I. SMOKING: Heat and wood smoke


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Drying

Objective is the eliminate H2O withminimum damage to food by getting heatinto the food and moisture out

Removal of water eliminates multiplicationof bacterial cells

Drying is sometimes done in the presence

of chemicals such as SO2, Ca or Napropionate to control microorganisms

D i


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Drying:

Drying reduces the water activity (Aw) in afood. Since microorganisms contain about

80 percent moisture, drying or dehydratingthe food also dehydrates themicroorganism. Changing the amount ofwater in a food also alters the rate ofenzyme activity and other chemicalreactions.


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Freeze Drying

Advantages

Fresh flavors and textures betterpreserved over drying

Reduced transportation and storagecosts

Refrigeration unnecessary

Nutritive value remains very similar tothe fresh product


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3. COMMERCIAL STERILIZATION

A severe heat treatment that destroyspathogenic and many microorganismsthat could spoil food. Extends shelf life,room temperature stable. (cannedfoods)

4. STERILIZATION - A very severe heattreatment that destroys allmicroorganisms.


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FACTORS INFLUENCING CHOICE OF HEATTREATMENTS

1. Type of food

a. pH

Low acid: 5.0 - 6.8. Meat, dairy, vegetables Medium acid: 4.6 - 5.0. Soups, vegetables Acid: 3.7 - 4.5. Fruits High acid: 2.3 - 3.6.Citrus fruits, berries

In medium & low acid (>4.5 pH) Foods, thecanning process is designed to kill C.Botulinum.


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FACTORS INFLUENCING CHOICE OF HEATTREATMENTS (cont.)

2. Level of contamination

3. Presence of oxygen

4. Heat resistance of organisms orenzymes

5. Heat penetration

characteristics of the food

6. Packaging material

7. Size of container

8. Sensory qualities desired


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DRY BEANS: Must be partly rehydrated beforeblanching can take place. Multiple blanchers or

long water blanchers are used. Where doesthe rest of the water come from to finish thethermal process (example: canned chili). Howlong do you cook the canned dried beans?


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ADEQUACY OF BLANCHING:

Enzyme tests:

Peroxidase

Catalase

LipoxygenasePhysical:

Wilting

Color


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PASTEURIZATION

Used for milk, liquid eggs, fruit juicesand beer.

Destroy pathogens Reduce microbial load (numbers)

Inactivate enzymes

Extend shelf life


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MILK PASTEURIZATION: Based upon T.B.Microorganism; Test for adequacy using

phosphatase (blue color test).

Vat: 145 F (62.8 C) for 30 minutes

HTSH:161 F (71.7 C) for 15 seconds

191F (88.3 C) for 1 second

194 F (90 C) for 0.5 second

UHT: 275-284

F (135 to 140

C) fora few seconds


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CREAM: 150-155 F (65.6-68.3 C) For30 minutes

166-175 F(74.4-79.4 C) For 15seconds

EGG PASTEURIZATION: Based uponkilling and preventing growth ofsalmonella (food-borne illness

microorganism). Liquid eggs heated to 140-144 F

(60-62 C) and held for 3.5-4.0 minutes.Often sugar or salts are added. Why?


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FRUIT JUICE PASTEURIZATION:Newto kill E. Coli 0157:H7 And/or other food-borne illness microorganisms. It alsoreduces microbial load, inactivatesenzymes, and extends shelf life.

BEER PASTEURIZATION:

1. Use of heat before or after bottling

2. Cold pasteurization - sterile filtering:better flavor than heat pasteurization notto be confused with irradiation.


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Pasteurization

Foods heated to a certain temp for acertain amount of time to kill harmful

bacteria Milk most commonly pasteurized food

beer, wine and fruit juices also pasteurized

Milk heated to 63C (145F) for 30minutes


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Canning

The process of sealing a food in an airtightcontainer and destroying all

microorganisms by heating The sterilization temperature is dependant

on pH:pH Temperature

4.6 or greater > 121C

4.5 or lower < 100C


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FOOD ADDITIVES PRESERVATIVES


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FOOD ADDITIVES - PRESERVATIVESTHAT INHIBIT MICROORGANISMS

A. ACID

B. SUGAR AND SALTSC. ANTIMICROBIAL AGENTS


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Chemical Additives sodium nitrate fatty acids

sulfur dioxide sorbic acid

diethyl pyrocarbonate oxidizing agents

benzoates antibiotics antioxidants

F d F i


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Food Fermentation

FERMENTATION


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FERMENTATION

Use of microorganisms to convert foods (rawcommodities) into a more stable form.

Typically the conversion of carbohydratesinto acid or alcohol. Some additionalantimicrobial compounds may be formed.

THEORY: Reduce the pH of the food or producesubstances which make the environment

uninhabitable by other organisms.


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FACTORS THAT INFLUENCEFERMENTATION

1. Type of organism natural or starter

acid, oxygen, temperature,

salt tolerance

2. Source of energy

3. Oxygen availability

4. Temperature

5. pH

6. Aw


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Encourages the growth ofsome bacteria, which

consume part of the food &create __________________

Example: Yogurt, formedwhen bacterial culture isadded to milk

Bacteria eat milk sugars(lactose) & form

_______________ acid

The pH drops, which inhibits thegrowth of other bacteria

Fermenting


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F d F d


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Fermented Foods Foods fermented by

yeast

Malt Beer

Fruit (grapes) Wine

Rice Saki Bread dough Bread

Foods fermented bymold

Soybeans Soy

sauce

Cheese Swiss

cheese

Foods fermented bybacteria

Cucumbers Dillpickles

Cabbage Sauerkraut Cream Sour cream

Milk Yogurt


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Works in 2 ways

Adding organic acids (vinegar)Adding a desirable culture to produce an

organic acid

The goal: Lower acidity of food to

kuliah 4 food processing 2011

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