FOOD PROCESSING AND PRESERVATION-FULL

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FOOD PROCESSING AND

PRESERVATION - FULL

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HEAD ACHE…?

• EAT FISH!

• Eat plenty of fish -- fish oil helps

prevent headaches. So does ginger,

(3)

HEAVY FEVER ….?

• EAT YOGURT!

• Eat lots of yogurt before pollen season.

• Also-eat honey from your area (local

(4)

TO PREVENT STROKE….. ?

• DRINK TEA!

• Prevent buildup of fatty deposits on artery

walls with regular doses of tea.

• (Actually, tea suppresses my appetite and

keeps the pounds from invading....Green tea is

great for our immune system)!

(5)

INSOMNIA.. (CAN'T SLEEP…?)

• HONEY!

(6)

ASTHMA……. ?

• EAT ONIONS!!!!

• Eating onions helps ease constriction of bronchial

tubes. (When I was young, My mother would make

onion packs to place on our chest, helped the

respiratory ailments and actually made us breathe

better).

(7)

ARTHRITIS… ?

Salmon Fish _{Tuna Fish}

• EAT FISH, TOO!!

• Salmon, tuna, mackerel and sardines actually

prevent arthritis. (Fish has

omega oils, good for our immune system)

Mackerel Fish

(8)

UPSET STOMACH… ?

• BANANAS - GINGER!!!!!

• Bananas will settle an upset stomach.

• Ginger will cure morning sickness and

(9)

BLADDER INFECTION…. ?

• DRINK CRANBERRY JUICE!!!!

• High-acid cranberry juice controls

(10)

BONE PROBLEMS…?

• EAT PINEAPPLE!!!

• Bone fractures and osteoporosis can be

prevented by the manganese in

(11)

MEMORY PROBLEMS…?

• EAT OYSTERS!

• Oysters help improve your mental functioning

by supplying much-needed zinc.

(12)

COLD …?

• EAT GARLIC!

• Clear up that stuffy head with garlic.

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COUGHING….?

• USE RED PEPPERS!!

• A substance similar to that found in the cough

syrups is found in hot red pepper . Use red

(cayenne) pepper with caution-it can irritate your

tummy.

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BREAST CANCER….. ?

• EAT Wheat, bran and cabbage, helps to

(15)

LUNG CANCER….. ?

Try these green fruits & vegetables: •Broccoli (excellent!!) •Kale •Romaine lettuce •Bok choy •Zucchini •Collard greens •Brussel Sprouts •Cucumbers •Cabbage •Artichoke •Okra •Kiwi •Honeydew Melon •Lime

• EAT DARK GREEN VEGGIES AND ORANGE !!!

• A good antidote is beta carotene, a form of Vitamin A found in dark green and orange vegetables.

•Brussel Sprouts •Turnip greens •Spinach

•Asparagus

•Lime

•Green bell pepper •and there are many,

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ULCERS….?

• EAT CABBAGE ALSO!!!

• Cabbage contains chemicals that help heal

both gastric and duodenal ulcers.

(17)

DIARRHEA…..?

• EAT APPLES!

• Grate an apple with its skin, let it turn

brown and eat it to cure this condition .

(Bananas are good for this ailment)

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CLOGGED ARTERIES….?

• EAT AVOCADO!

• Mono unsaturated fat in avocados lowers

(19)

HIGH BLOOD PRESSURE….?

CELERY OLIVES

• EAT CELERY AND OLIVE OIL!!!

• Celery contains a chemical that lowers

pressure too.

• Olive oil has been shown to lower blood

pressure.

(20)

BLOOD SUGAR IMBALANCE……?

• EAT BROCCOLI AND PEANUTS!!!

• The chromium in broccoli and peanuts

(21)

FRUITS:-Kiwi….?

• Tiny but mighty. This is a good source of

potassium, magnesium,

• Vitamin E &fiber. Its Vitamin C content is twice

that of an orange.

(22)

Apple….

• An apple a day keeps the doctor away? Although an

apple has a low Vitamin C content, it has antioxidants

& flavonoids which enhances the activity of Vitamin

C thereby helping to lower the risks of colon cancer,

Heart attack & stroke.

(23)

Strawberry…..

• Protective fruit. Strawberries have the highest total

antioxidant power among major fruits &protects the body from cancer causing, blood vessels clogging free radicals. (Actually, any berry is good for you . .they're high in

anti-oxidants and they actually keep us young ...blueberries are the best and very versatile in the health field ...they get rid of all the free-radicals that invade our bodies)

(24)

Orange….

• Sweetest medicine. Taking 2 - 4 oranges a day

may help keep colds away , lower cholesterol,

prevent & dissolve kidney stones as well as

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Water melon

• Coolest Thirst Quencher. Composed of 92% water, it is also

packed with a giant dose of glutathione which helps boost our immune system. They are also a key source of lycopene - the cancer fighting oxidant. Other Nutrients found in watermelon are Vitamin C &Potassium. (watermelon also has natural

substances [natural SPF sources] that keep our skin healthy, protecting our skin from those darn suv rays)

(26)

Guava

&

Papaya

…

Guava fruit Papaya fruit

• - Top awards for Vitamin C. They are the clear

winners for their high Vitamin C content. Guava is

also rich in fiber which helps prevent constipation.

• Papaya is rich in carotene, this is good for your eyes.

(also good for gas and indigestion)

(27)

Tomatoes…….

• Are very good as a preventative measure

for men, keeps those prostrate problems

from invading their bodies.

(28)

CONSTITUENTS OF FOODS

THERE ARE THREE MAIN GROUPS OF

CONSTITUENTS OF FOODS

• CARBOHYDRATES

• PROTEINS

• FATS and derivatives of these

In addition, there are inorganic and mineral components and a diverse group of organic substances like vitamins, enzymes, emulsifiers, acids, oxidants, antioxidants, pigments and flavors in small proportions.

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The general composition of a food as well

as the way in which the components are

organized give a food its individual

characteristics

For example, whole milk and fresh apples have

about the same water content. But one is a

liquid and the other is a solid because of the way

the components are arranged

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CARBOHYDRATES

• Carbohydrates are organic compounds with the basic structure of Cx (H2O)y

• In foods they are available as sugars (glucose, fructose,

maltose, sucrose, and lactose) , dextrins, starches, celluloses, hemicelluloses, pectins and certain gums

• Simple carbohydrates are called as sugars and they contain 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms

carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms

• Carbohydrates play a major role in biological systems and in foods. They are produced by photo synthesis in plants.

• Carbohydrates can be oxidized to furnish energy

• Glucose in the blood is a ready source of energy

• Fermentation of carbohydrates by yeast and other micro organisms can yield carbon dioxide, alcohol, etc.

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PROPERTIES OF SUGARS

• They are used for their sweetness

• They are readily soluble in water and form syrups

• They form crystals when water is evaporated from their

solutions (this is the way sucrose is recovered from sugar cane juice)

• They supply energy

• They are readily fermented by microorganisms

• They prevent the growth of microorganisms in high concentration. So they are used as preservatives

• They darken in color or caramelize (burnt appearance) on heating. Some combine with proteins to give dark

colors(browning reaction)

• They give body and mouth feel to solutions in addition to sweetness

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PROPERTIES OF STARCHES

• Starches are from plant origin

• They are not sweet

• They are not readily soluble in cold water

• They provide a reserve energy source in plants

and supply energy in nutrition

• They occur in seeds as characteristic starch

granules

• Starch granules may be precooked to produce a

(33)

PROPERTIES OF CELLULOSES AND

HEMICELLULOSES

• They are acting as supporting structures in plant tissues and relatively resistant to breakdown

• They are soluble in cold and hot water and are not digested by man. So they don't yield energy

• Long cellulose chains may be held together in bundles

• Long cellulose chains may be held together in bundles forming fibers as in cotton

• The fiber in food that produces necessary dietary roughage is largely cellulose. The hard parts of coffee beans and nut shells contain celluloses and hemicelluloses

• They can be broken down to glucose units by certain enzymes and microorganisms

(34)

PROPERTIES OF PECTINS AND

CARBOHYDRATE GUMS

• They are sugar derivatives usually present in plants in lesser amounts

• Pectins are made up of chains of repeating units

• Pectins are common in fruits and vegetables and are gumlike

• Pectins are soluble in hot water

• Pectins contribute viscosity to tomato paste and stabilize the fine particles in orange juice from setting out

• Pectins in solution form gels when sugar and acid are added (jelly manufacture)

• Pectins and gums are added to foods as thickeners and stabilizers

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PROTEINS

• Proteins are made by linking individual amino acids in long chains. Amino acids are made up of carbon, hydrogen, oxygen and nitrogen and some may also have sulfur

• Proteins are essential to all life

• They are major constituents of enzymes, antibodies, many hormones and body fluids such as blood, milk and egg white hormones and body fluids such as blood, milk and egg white

• Protein chains can be oriented parallel to one another like the strands of rope as in wool, hair and the fibrous tissue of

chicken or they can be randomly tangled like a bunch of string

• When the organized molecular configuration is of the protein is disorganized we can say the protein is denatured

(36)

FATS AND OILS

• Fats differ from carbohydrates and proteins in that they are not polymers of repeating molecular units

• They do not contribute structural strength to plant and animal tissues

• Fats are smooth and greasy substances that are insoluble in water

water

• Fat is mainly is a fuel source for animal and plant. It contains 2.25 times the calories found in equal dry weight of protein and carbohydrate

• A typical fat molecule consists of glycerol combined with three fatty acids

(37)

• Fats gradually soften on heating. They do not have sharp melting point. Fats can be heated above the boiling point of water, they can brown the surfaces of foods

• When heated further they begin to smoke, then they flash and then they burn. The temperatures are called as smoke, flash and fire

points respectively. This is important in commercial frying operations

• Fats will become rancid when they react with oxygen OR fatty acids are liberated from glycerol by enzymes

• Fat forms emulsions with water and air. Fat globules are suspended in a large amount of water as in milk or cream. Water droplets may be suspended in a large amount of fat as in butter

• Fat is a lubricant in foods. Fat has shortening power of fibrous muscles. Fat tenderizes meat as well as baked goods

• Fats contribute characteristic flavors to foods and in small amounts

(38)

ADDITIONAL FOOD CONSTITUENTS

• Carbohydrates, Proteins and fats are called as major

food constituents

• There are other groups of substances which play in

important role, out of proportion to their relatively

small concentration in foods

• They are

Natural Emulsifiers, Analogs, Organic Acids,

Oxidants and Antioxidants, Enzymes, Pigments and

Colors, Flavors, Vitamins and Minerals, Natural

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NATURAL EMULSIFIERS

• Materials that keep fat globules dispersed in

water OR water droplets dispersed in fat are

emulsifiers

• Lecithins are the example for natural

emulsifiers

• Lecithins are structurally like fats but contain

Phosphoric acid

• Emulsifiers belong to a broader group of

chemicals known as surface active agents

(40)

ANALOGS

• Analogs have the common objective of

mimicking the functional properties such as

flavor, mouthfeel, texture and appearance at

the same time reducing the caloric content of

the food

• The use of fat replacers in ice cream is a good

example of analogs

• Other substitutes for sugar and fat are also

developed

(41)

ORGANIC ACIDS

• Fruits contain natural acids, such as citric acid of oranges and lemons, malic acid of apples and tartaric acid of grapes

• These acids give the fruits tartness[ sharp in taste ] and slowdown the bacterial spoilage

• Foods are deliberately fermented with bacteria to produce acids to improve flavor and quality

acids to improve flavor and quality

• Organic acids have a wide range of textural effects in foods due to their reactions with proteins, starches, gums and other food constituents

• Acids are also important inhibitors of bacterial spoilage in foods

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OXIDANTS AND ANTIOXIDANTS

• Many food constituents are adversely affected by oxygen in the air. Oxygen is an oxidant which causes oxidation of these materials

• Certain metals like copper and iron are strong promoters of oxidation. This is one of the reasons why copper and iron have largely been replaced in food processing equipment by

largely been replaced in food processing equipment by stainless steel

• An antioxident tends to prevent oxidation. Natural

antioxidants present in foods are lecithin, vitamin C and E and certain sulfur containing amino acids. Synthetic chemicals

approved by Govt. are also effectively used as antioxidants in foods

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ENZYMES

• Enzymes are biological catalysts that promote a wide variety of biochemical reactions

• Amylase found in saliva promotes digestion or breakdown of starch in the mouth

• Pepsin found in gastric juice promotes digestion of protein

• Lipase found in liver promotes breakdown of fats

• Even after a plant is harvested or an animal is killed, most of the enzymes continue to promote specific chemical reactions

• Enzymes are large protein molecules

• Enzymes function by lowering the activation energies of specific substrates

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PIGMENTS AND COLORS

• Natural Plant and Animal Pigments are giving the color to foods

• Chlorophyll imparts green color to peas

• Carotene gives the orange color to carrots and corns

• Lycopene contributes the red to tomatoes and watermelons

• Anthocyanins contribute purple to grapes Oxymyoglobin gives the red color to meats

• Oxymyoglobin gives the red color to meats

• The natural pigments are highly susceptible chemical change – Fruit ripening, Meat ageing

• Excess heat alters the color of foods

• The second source of color to food is sugars

• Dark colors are resultant from chemical interactions between sugars and proteins

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FLAVORS

• The occurrence and food flavor changes more

complex than anything

• In coffee alone there are 800 constituents

which contribute to flavor and aroma.

• These organic chemicals are highly sensitive to

air, heat and interaction with one another

• It is important to note that the flavor has a

(46)

VITAMINS AND MINERALS

• Vitamins are organic chemicals

• Vitamin D can be manufactured by human body

• Vitamins are divided into two main groups as fat

soluble – A, D, E & K and water soluble – C & B

• Minerals are also required by human body. The

deficiency may result in weakness in bones and

tooth.

(47)

NATURAL TOXICANTS

• The plants have evolved the ability to form many

compounds which may serve to protect the plant.

Some of these are toxic

• Some species of mushrooms have poisonous

properties

The toxicants occurring naturally in foods are alkaloid

• The toxicants occurring naturally in foods are alkaloid

solanine in potatoes, cyanide in lima beans, safrole in

spices, prussic acid in almonds, oxalic acid in spinach

etc.

• Many harmful substances are also added to food

from industrial contaminants, fertilizers, soil and

water.

(48)

WATER

• Water is present in most natural foods to the extent of 70% of their weight or greater

• Fruits and vegetables may contain 90% to 95%

• Cooked meat still contains 60% of water

• Water greatly affects the texture of foods

• The form of water present in the food decide the physical properties of food. Milk and apple have the same amount of properties of food. Milk and apple have the same amount of water but have different physical structure

• Removing food from water is called as food dehydration

• The removal water is done in foods to reduce weight and to preserve

• Water which can’t be removed by dehydration is called as bound water

(49)

UNIT OPERATIONS IN FOOD

PROCESSING INDUSTRY

• Cleaning • Coating • Concentrating • Controlling • Disintegrating • Forming • Heating/Cooling • Materials handling • Mixing • Packaging • Disintegrating • Drying • Evaporating • Fermentation • Packaging • Pumping

• Separating and others

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• The unit operations may also include

numerous different activities. For

example agitating, beating, blending,

diffusing, dispersing, emulsifying,

homogenizing, etc.

• One of the key elements to food

processing is the proper selection and

combination of unit operations into more

complex integrated processing systems

(53)

MATERIALS HANDLING

• Materials handling includes such varied operations as hand and mechanical harvesting on the farm, refrigerated trucking of perishable produce, box car transporting of live cattle and pneumatic conveying of flour from rail car to bakery storage bins

bins

• Throughout such operations emphasis must be given to

maintaining sanitary conditions, minimizing product losses, maintaining the material quality, minimizing bacterial growth, and timing all transfers & deliveries so as to minimize the

(54)

CLEANING

• Foods by the nature of the way they are grown or produced on farms in open environment requires cleaning before use

• Cleaning ranges from simple removal of dirt from egg shells with an abrasive brush to the complex removal of bacteria from a liquid food by passing it through a micro porous membrane

• Grains must be cleaned of stones before use

• Cleaning can be accomplished with brushes, high velocity air, steam, water, vacuum, magnetic attraction of metal

contaminants, mechanical separation and so on

• Some cleaning methods are dictated by surface

characteristics of the product

• Many types of soil dirt can be cleaned with mild alkaline detergents

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SEPARATING

• Separating can involve separating a solid from a solid OR solid from a liquid OR liquid from a solid

• One of the commonest forms of separating is the hand sorting and grading of individual units as in the case of vegetables

and fruits

• Mechanical and electronic sorting devices are developed to avoid the problems in manual sorting

• Difference in color can be detected by a photo cell and this can be done at enormous speeds

• Light shining through eggs can detect blood spots

• Automatic separation according to size is easily accomplished by passing fruits or vegetables over different size screens and holes

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The skins of fruits and vegetables may be removed

using a lye peeler

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DISINTEGRATING

• Operations which subdivide large pieces of food into smaller parts are classified as disintegrating

• It may involve cutting, grinding, pulping, homogenizing and so on

• Normally dicing [cubing] of vegetables is done in automatic machines

machines

• The cutting of meat is still a time consuming hand-labor operation

• When disintegrating is done by grinding heat is produced and this heat may denature the proteins. To avoid this grinding operations are normally done in frozen form

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A. SLICING EQUIPMENT

(62)

PUMPING

• Moving fluids from one processing step to

another is done by pumping

• There are many kinds of pumps. The choice is

dependent on the character of food to be

moved

• Cam and piston pump, Gear pumps, Lobe

pumps, Screw pumps, Vane pumps and

Shuttle block pumps are normally used for this

purpose

(63)

MIXING

• There are many kinds of mixtures depending on the materials to be mixed

• Mixing solids with solids, solids with liquids and liquids with liquids can be done

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HEATING

• Many foods are heated to destroy microorganisms

• Some are heated to drive away moisture and to develop flavors

• Some are also heated to make them more tender

• Foods are heated by conduction, convection and radiation or a combination of these

a combination of these

• Foods are sensitive to heat

• Prolonged heating causes burned flavors, dark colors and loss of nutritional value

• Foods may be heated or cooked using toasters, direct

injection of steam, direct contact with flame, using electronic energy as in the case of microwave ovens, etc.

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COOLING

• Cooling is the removal of heat energy and this

may be done to the degree of chilling to

refrigerator temperature. Beyond this range

the food is frozen

• Milk is cooled by passing them in thin layers

through heat exchangers

• There are many types of commercial freezers

• Quick freezing is done to preserve the food

quality. Liquid nitrogen at -196 degree celcius

is used for this purpose

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EVAPORATION

• Evaporation is principally used to concentrate

food by removal of water

• It is also used to recover desirable volatiles

and to remove unwanted volatiles

• Grapes and some other fruits are dried in sun

light

• All liquids boil at low temperature under

reduced pressure

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DRYING

• The objective of drying is to remove water with minimum damage to the food

• Evaporators will concentrate foods twofold or threefold but the driers will take food very close to total dryness

• Driers are used to prepare products like milk powder and instant coffee

• Liquid foods are normally subdivided either as a spray or as a

• Liquid foods are normally subdivided either as a spray or as a film and then the moisture is removed quickly with the help of circulating heated air

• Small food pieces such as peas and diced onions can be dried by moving through a long tunnel oven

• Over heating and shrinkage by the removal of moisture will give poor quality to the food and this can be avoided by freeze drying

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FORMING

• Foods are often formed into specific shapes

• Pressure is applied to form the desired

shapes. If necessary heating is also done in

some cases

• Forming is an important operation in making

breakfast cereals. This is done by pressure

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PACKAGING

• Food is packaged for many purposes.

• Some reasons are containment for shipping, dispensing, unitizing in to appropriate sizes, improving the usefulness, protect from microbial contamination, physical dirt, insect invasion, light exposure, flavor pickup, flavor loss, moisture pickup, moisture loss and physical abuse

pickup, moisture loss and physical abuse

• Food is packaged in metal cans, glass & plastic bottles, paper & paper board, wide variety of plastic & metallic films and combinations of these

• Packaging is done by continuous automatic machines at a speed of 1000 units per min

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OVERLAPPING UNIT OPERATIONS

• The division or grouping of the unit operations is not

fixed and perfect. There can be overlapping

• Any total food process will always be a series of unit

operations, performed in a logical sequence

• In modern food processing these operations are so

connected as to commonly permit smooth,

continuous automatically controlled production

• So that the sequence is dependent on the type of the

food, the industry by which it is processed, etc.

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ENERGY CONSERVATION

• All the unit food processing unit operations require

considerable amounts of energy. Thus the energy cost is a significant part in food production

• Care must be taken while designing the unit operations for

optimizing energy use

• Dehydration, concentration, freezing, sterilization and other

• Dehydration, concentration, freezing, sterilization and other operations are being reevaluated in terms of times and temperatures

• There are many methods to conserve energy throughout the

food production. Today it is also common to employ energy conservation specialists for energy auditing and management

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FOOD DETERIORATION AND ITS CONTROL

• All foods undergo varying degrees of deterioration during

storage

• Deterioration include organoleptic desirability, nutritional value, safety and aesthetic appeal

• Foods may change in color, texture, flavour etc

• Food is subjected to physical, chemical and biological

deterioration

• Heat, cold, light, other radiation, oxygen, moisture, dryness, natural food enzymes, micro organisms, macro organisms, industrial contaminants, presence of other foods and time are range of potentially destructive factors

(82)

USEFUL STORAGE LIFE OF PLANT AND

ANIMAL TISSUES

FOOD PRODUCT GENERALISED STORAGE LIFE AT 21O_{C [days]}

Meat 1-2

Fish 1-2

Poultry 1-2

Dried, salted, smoked meat and fish 360 and more

Fruits 1-7

Dried fruits 360 and more Leafy vegetables 1-2

Leafy vegetables 1-2 Root crops 7-20

Dried seeds 360 and more

• Room temperature is much higher than 21 deg c in many

parts of the world

• Similarly slow rate of deterioration will occur in low

temperature, low moisture, high in sugar, high in salt, high in acid etc.

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• It is interesting to note that some most important methods of food preservation have been developed during the time of war

• When Napoleon of France is at war during eighteenth century

the army suffered a lot with spoiled food

• Prizes were offered to develop useful methods for preserving food

• A scientist Nicolas Appert found that food can be preserved

by heating it in a sealed container and Appert was awarded. by heating it in a sealed container and Appert was awarded. This lead to the development of canning food

• The renowned scientist Pasteur invented that the spoilage of food is due to micro-organisms and that can be controlled or killed by heating. This lead to the development of processes like pasteurization and sterilization

• One of the most important aspects of food processing is to

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SHELF LIFE AND DATING OF FOODS

• It is defined as the time that a food takes to decline to an unacceptable level

• The term acceptable varies from person to person. In many

cases the manufacturer will define the minimum acceptable quality[MAQ]

• The shelf life depend on many factors like processing method,

• The shelf life depend on many factors like processing method, packing and storage conditions

• For example one cant exactly tell the shelf life of fresh milk at room temperature. Milk at room temperature have different shelf life than milk stored at refrigeration temperature

• So a dating system is formed in retail packages like Pack date, sell by date etc.

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MAJOR CAUSES OF FOOD DETERIORATION

• Growth and activities of micro organisms [bacteria, yeasts and molds]

• Activities of food enzymes and other chemical reactions within the food itself

• Infestation by insects [parasites and rodents]

• Inappropriate temperature for a given food

• Either the gain or loss of moisture

• Reaction with oxygen

• Exposure to light

• Physical stress or abuse

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BACTERIA, YEASTS AND MOLDS

• There are thousands of species of micro organisms and they

are all associated with one another and food products

• Not all the species are causing the damage. The growth of

some are desirable [production of alcohol, flavor production in some food etc.]

• Micro organisms are capable of spoiling food and found

everywhere [soil, water, air, skins of cattle, feathers of poultry, everywhere [soil, water, air, skins of cattle, feathers of poultry, intestines and cavities of animal body, skins and peels of fruits and vegetables, hulls of grains and the shells of nuts, food processing equipment, hands, skin and clothes of the worker]

• It is to be noted that the micro organisms are not found within the flesh of healthy living animal and juice of plants

• Milk of a healthy cow is sterile but becomes contaminated as it passes through the teat canals

(87)

• Bacteria are single-celled organisms and can be classified into one of three types based on the shape of the cells

• Bacterial spores are far more resistant than yeast and mold

spores

• All bacteria associated with food are small in the order of

micro meter

• Molds are still larger and complex in structure and are in the order of 1 micro meter

• Most yeasts are spherical or ellipsoidal and are larger in the

• Most yeasts are spherical or ellipsoidal and are larger in the order of 20 micro meter

• Bacteria, yeast and mold can attack all food items. Some

ferment sugars, hydrolyze starches and celluloses, hydrolyze fats and produce rancidity, few produce toxins, digest proteins, produce ammonia like odors

• The micro organisms like warm and moist conditions and are

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• Some will grow at freezing point of water and are called as psychrophilic

• The others will grow at temperatures above 82 deg c and are

called as thermophilic

• The spores of many bacteria will survive prolonged exposure

to boiling water and then multiply when the temperature is lowered

• Bacteria will multiply by cell division. One will become two,

• Bacteria will multiply by cell division. One will become two, two will become four and so on. They can double their number in every 30 minutes under favorable conditions

• Food intoxications involve toxic substances produced in food by micro organisms

• The bacteria called C Botulinum produce food toxins in many

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FOOD-BORNE DISEASE

• Food-borne diseases are commonly classified as food infections that are caused by microorganisms or food intoxicants that are produced in foods as by products of microorganisms prior to consumption

• S aureus and C botulinum produce specific food toxins

• Certain molds also produce toxins

• Many bacteria can transmit food-borne infections capable of

• Many bacteria can transmit food-borne infections capable of causing human disease

• Number of viral infections may be contracted by man through contaminated food

• Microorganisms that are causing disease to humans are known as pathogenic or pathogens

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INSECTS, PARASITES AND RODENTS

• Insects are particularly destructive to cereal grains, fruits and vegetables

• When insects eat food the food will be open to

microorganisms and this will cause further damage

• Insect eggs may persist or be laid in food then they multiply

• Commodities containing highly destructive insects are

prohibited from import and export prohibited from import and export

• The important food-borne parasite is the Trichinosis

nematode and Trichinella spiralis. This will penetrate into the intestines of pork

• A worm from food called Genus Anisakis can infect man and

this can survive in refrigeration temperature

• Rodents consume and waste huge volume of food. The urine

poured on the food by rodents is containing several disease producing bacteria

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FOOD ENZYMES

• The enzymes present in food ferment, rancidify and putrefy

• The activity of enzymes may be present in food even after 60 yrs of storage

• In living plant and animals these type enzymatic activities are balanced

• The enzyme pepsin helps digest proteins in food but it will not

• The enzyme pepsin helps digest proteins in food but it will not digest the intestine

• Some of the reaction of the enzymes are highly desirable. For example the ripening of fruits

• The enzymes may be inactivated by heat, chemicals,

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HEAT AND COLD

• Heat and cold can also cause deterioration in foods if they are nor controlled

• The rate of chemical reaction is doubled in every 10 deg C rise

• Excessive heat will denature proteins, breaks emulsions, dries food by removing moisture and destroys vitamins

• Freezing will also denature proteins in milk, the emulsion will

•

be broken and the fat will separate

• In refrigerated storage temperature ie) 4 deg C, some are

weakened or killed and deterioration will follow. This is known as chill injury

• Bananas, lemons and some other foods are to be kept above 10 deg C for retaining maximum quality

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MOISTURE AND DRYNESS

• Excessive moisture pickup and dryness cause deterioration in foods

• Moisture is required for chemical reactions and for

microorganisms

• Loss of moisture particularly affect the texture and

appearance appearance

• Surface moisture resulting from changes in RH can cause

lumping, caking, mottling, crystallization and stickiness

• Very small amount of condensed water is enough for the

growth of microorganisms

• The condensation may also occur from the water of the food.

(98)

OXYGEN

• The 20% of oxygen in the air is quite enough to cause

reactions in many foods

• Vitamins A & C, food colors and flavors are subject to

oxidation

• Oxygen is essential for the growth of microorganisms

• Most of the molds are aerobic. They grow on the surface of

foods foods

• Atmospheric oxygen is removed from the packing of many

foods and other gases like nitrogen and carbon dioxide are filled inside. This is called as modified atmosphere packaging

• Some foods are packed with oxygen scavengers for absorbing

(99)

LIGHT

• Light destroys vitamins A, C and riboflavin

• Light also cause deterioration in many food colors

• Milk in bottles exposed to the sun light changes its flavor. This is due to light induced oxidation and changes in protein

• Surface discolorations of sausages and meat pigments are

different under natural light and under fluorescent lamps

• Sensitive foods are packaged in opaque materials

TIME

• After harvest there is a time when the quality of the food is highest. In many foods the quality is peak in one or two days

• All deteriorative activities progress with time. But this is not applicable to some fermented foods

(100)

PRINCIPLES OF FOOD PRESERVATION

1. Keep the food alive as long as possible. Kill

the animal or plant just before it is to be used

2. After killing the food clean it, cover it and

cool it as quickly as possible. This will

slowdown the deterioration for a short time

3. For long term and practical preservation

inactivating or controlling microorganisms,

enzymes

and

reducing

or

eliminating

(101)

CONTROL OF MICROORGANISMS

• Controlling bacteria, yeasts and molds is done by heat, cold, drying, acid, sugar, salt, smoke, air, chemicals radiation

HEAT

• Most of the micro organisms grow best at the temperature

range of about 16 to 38 deg C

• Most bacteria are killed in the temperature range of 82 to 93

•

deg C

• But many bacterial spores are not destroyed even by boiling

water at 100 deg C for 30 min

• To ensure sterility (total destruction of microorganisms

including spores) a temperature of 121 deg (wet heat) must be maintained for 15 min or longer

(102)

(103)

• There are two standards called sterility and commercial sterility

• Not all the foods require the same amount of heat for

sterilization

• When food are high in acid such as tomatoes and oranges, the killing power of heat is increased. A temperature of 93 deg C for 15 min is enough to gain sterility if sufficient acid is present

• Safe temperatures and times fro different foods are published

• Safe temperatures and times fro different foods are published in standard handbooks

• Many times it is not necessary to kill all the microorganisms. It may be enough to supply heat to destroy disease producing organisms only

• In pasteurization of milk 63 deg C for 30 min is enough to

(104)

COLD

• Psychrotroph type microorganisms will grow down to 0 deg C, the freezing point of water and below

• At temperatures below 10 deg C the growth rate is slow and becomes slower the colder it gets

• When the water is frozen there is no multiplication of microorganisms

• But in some foods all of the water is not frozen at a temperature of -10 deg C or lower

• The slowing of microbial activity is the principle behind the refrigeration and freezing preservation

and freezing preservation

• An important thing is to be noted that an ice cream mix inoculated with typhoid bacteria still remained 600000 live bacteria per millimeter after 1 year of frozen storage

• When the food is taken out of the frozen storage and thawed the microorganisms will begin to grow

• Recent studies show that some disease producing bacteria can grow at refrigeration temperatures of 3.3 deg C

(105)

(106)

DRYING

• Microorganisms in a healthy growing state may contain in excess of 80% water

• If the water is removed from the food, water will also be removed from the bacterial cells and multiplication will stop

• Partial drying is less effective than total drying and is done for several reasons

ACID

• In sufficient strength acid modifies bacterial proteins as in denatures food proteins and hence the microorganisms are sensitive to acid

sensitive to acid

• The acid produced by one organism during fermentation will often will inhibit another type of organism

• Controlled fermentation is a method of preservation

• Acid may be produced in foods by adding acid producing bacterial cultures. In some cases the acids are directly added to foods. Some foods naturally contain rich acids

• As we discussed earlier acid combined with heat is more destructive to microorganisms. The acid concentration is measured in ph values

(107)

(108)

(109)

SUGAR and SALT

• Many fruits are preserved by placing them in a sugar syrup

• Meat products are preserved by placing them in salt brine

• The microorganisms are contained by cell membranes and the

membranes allow water to pass through them

• Active microorganisms contain about 80% of water. When

they are placed in salt or sugar syrup the water from the cells is moved out through the membrane into the syrup. This is is moved out through the membrane into the syrup. This is the process of osmosis

• This cause partial dehydration of cells called as plasmolysis and this prevent cell multiplication

• Quite opposite will happen in placing food in distilled water

• Different organisms have various degrees of tolerance to

(110)

SMOKE

• Smoking of food is used as a meth of preservation in meat and fish

• Smoke contains preservative chemicals like formaldehyde

• Smoke is generally associated with heat and kill some bacteria

• In the presence of smoke dehydration will also occur in foods

• Smoking is also done to improve flavor

ATMOSPHERIC COMPOSITION ATMOSPHERIC COMPOSITION

• The growth of microorganisms require oxygen and air

• It is easy to exclude air from aerobes by wax coating and skin tight plastic films

• But preserving against anaerobe like C Botulinum the

(111)

CHEMICALS

• Many chemicals will kill or inhibit the growth of microorganisms

• Most of the chemicals are producing side effects and are not permitted

• Very few are permitted to be added in low levels in certain foods. They are sodium benzoate, sorbic acid, sodium, calcium propionate, ethyl formate and sulphur dioxide

RADIATION

• Radiation using x-rays, microwaves, ultraviolet light and ionizing

• Radiation using x-rays, microwaves, ultraviolet light and ionizing radiations are used to kill or inhibit microorganisms in foods. This radiation sterile most foods and deactivate enzymes

• For all types of radiation different type doses are required

• Today foods are irradiated with ionizing radiation obtained from radioactive isotopes or electron accelerators

• There will be no significant temperature rise in this irradiation and this method is called cold sterilization

(112)

CONTROL OF ENZYMES AND OTHER FACTORS

• Preservation of foods against deterioration from inherent

food enzymes will be the second important thing

• Just as microorganisms are controlled with heat, cold, drying etc. these are used here to control or inactivate damaging enzymes

• Heat and cold at the time of killing microorganisms also

inactivate the enzymes to some extent inactivate the enzymes to some extent

• It is important to note that some enzymes are more resistant to the effects of heat, cold and other methods of preservation

• Freezing Irradiation may be useful in inhibiting or killing

bacteria. But they are ineffective against enzymes

• Hence specific methods are to be employed for inactivating

(113)

FOOD DEHYDRATION AND CONCENTRATION

• Water is removed from food by a variety of controlled

dehydration processes such as cooking and baking

• Grains in the field dried by exposure to sun [upto 14% of

moisture]

• Centuries ago humans learned the natural sun drying process

to dry fish and thin slices of meat. This will not lower moisture less than 15%

• Food dehydration refers to artificial of dehydration under

controlled conditions and will completely remove moisture [upto 1% - 5%]

• Water is removed from potatoes before frying and cereals

from toasting

• Concentration process is the removal of partial water such as in the manufacture of syrups

(114)

DEHYDRATION

• Preservation is not the only reason for dehydration. Foods

may be dehydrated to reduce weight also

• Orange juice contain only 12% solids. So removal of moisture leaves one eighth of the total weight approximately

• This is useful in making powders of many fruits and other

liquid foods liquid foods

• Some drying processes are chosen to retain the size and

shape of the original food. Freeze-drying is such a method

• Reduced weight will reduce the shipping cost considerably

• Another reason is for production convenience. Instant coffee is a good example for this

(115)

HEAT AND MASS TRANSFER

• Irrespective of the method of dehydration and drying all will involve heat and mass transfer

• These two processes are not always favored by the same

operating conditions. For example pressing food between two hot plates will help to transfer heat but will not help to transfer moisture

• Our process must generally concentrate to remove moisture

as fast as possible

The following considerations are important

Surface area, temperature, air velocity, humidity, atmospheric pressure, vacuum, evaporation temperature, time and temperature.

(116)

(117)

• Figure 1 represents a typical drying curve for virtually any product. Drying occurs in three different periods, or phases, which can be clearly defined. The first phase, or initial period, is where sensible heat is transferred to the product and the contained moisture. This is the heating up of the product from the inlet condition to the process condition, which enables the subsequent processes to take place. In some instances, pre-processing can reduce or eliminate this phase. For example, if the feed material is coming from a reactor or if the feed is preheated by a source of waste energy, the inlet condition of the material will already be at a raised temperature.

• The rate of evaporation increases dramatically during this period with mostly free moisture being removed.

• During the second phase, or constant rate period, free moisture persists on the

• During the second phase, or constant rate period, free moisture persists on the surfaces and the rate of evaporation alters very little as the moisture content reduces. During this period, drying rates are high, and higher inlet air temperatures than in subsequent drying stages can be used without detrimental effect to the product. There is a gradual and relatively small increase in the product temperature during this period.

• Interestingly, a common occurrence is that the time scale of the constant rate period may determine and affect the rate of drying in the next phase.

• The third phase, or falling rate period, is the phase during which migration of moisture from the inner interstices of each particle to the outer surface becomes the limiting factor that reduces the drying rate.

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HEAT PRESERVATION AND PROCESSING

• Cooking, frying, and heating of foods prior to consumption are forms of heat preservation

• Heat processing is done for making food tender, palatable,

free from microorganisms and for deactivation enzymes

• The toxin produced by C Botulinum can be destroyed by

heating to 100 deg C for a period of 10 min

• Simple cooking process will not destroy all microorganisms

DEGREES OF PRESERVATION:

• Sterilization

• Commercial sterilization

• Pasteurization

(164)

• Sterilization refers to 121 deg C of wet heat for 15 min or more

• Commercial sterilization refers to killing pathogens

(165)

(166)

SELECTING HEAT TREATMENTS

The selection of the heat treatment is based on

• Time-temperature combination required to inactivate the most

of the heat resistant pathogens and spoiling microorganisms in a particular food

(167)

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• The D value and z value are used to characterize the heat resistance of a micro-organism and its temperature dependence respectively.

• There are a large number of factors which determine the heat

resistance of microorganisms, but general statements of the effect of a given variable on heat resistance are not always possible.

(171)

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COLD POINT IN FOOD MASSES

• When heat is applied from the outside the food nearest to the

heating surface will reach sterilization temperature sooner then the food near the centre

• The point in a food or inside a heating “can” which is the last to reach the final heating temperature is called as the cold point

• Knowledge about the cold point is important in determining the process time

process time

• Sufficient time must be allowed to bring the cold point of a given food mass to the required temperature in any heating process

• In heating food inside a can the cold point will be located in very centre of the can

• Both conduction and convection heating methods are used to heat food

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