EFFECT OF FOOD PROCESSING ON NUTRIENT CONTENT OF FOOD

&FOOD SPOILAGE

By:AYUSHI JAIN2010BT04

FOOD PROCESSINGFOOD PROCESSING

“Set of methods and techniques used to transform raw ingredients into food or to transform food into other forms for consumption by humans or animals”

AIMAIM

To make food safe (microbiologically, chemically).

To provide products of the highest quality (flavour, colour, texture)

To make food into forms that are convenient (ease of use)

Different Methods Different Methods Employed:Employed:

Various heat processes such as:

CookingBakingFryingMicrowave cookingToastingPasteurisationSmoking

MillingConcentrationSaltingBlanchingAddition of

preservatives (sulphites, etc)

FreezingCanningIrradiationDehydration/drying

……..Continued..ContinuedCutting,

trimming and peeling

Soaking, germination and fermentation

Controlled atmosphere storage, ripening and waxing

Effect of Food Processing on Effect of Food Processing on Nutrient Content:Nutrient Content:Depend on:Chemical stability of nutrient

contentExtent of processingEnvironmental factorsForm in which the foods are

delivered

Heat ProcessingHeat Processing::Merits:improves the digestibility of foods,

making some nutrients more available.

Demerits:Malliard reaction(non-enzymatic

browning)Affects bioavailability of mineralsLoss of vitamins

CookingCookingMerits:• Provides desired texture, flavor and

palatability to food.• Starchy foods such as potatoes, corn,

beans, and lentils are made more digestible.

• Destroys substances that would otherwise interfere with the digestibility of the protein.

• Decreases toxic effect of raw food and increases availability of vitamin content.

• Ensures that food is free from harmful levels of micro-organisms

Demerits:Leads to most important nutrient lossesMineral loss- leaching out in cooking

water(especially Zn and Cu loss, about 10-27%)

The largest vitamin loss during cooking is usually due to destruction of vitamin C, and to a lesser extent vitamin B-1 and the other water-soluble vitamins.

BakingBaking

FryingFrying

Microwave CookingMicrowave Cooking• Much quicker than conventional cooking• Thiamine-better retained• Niacin and Riboflavin are relatively stable.• Mineral composition is minimally affected.Toasting• A loss of about 10 to 30 per cent of the

vitamin B-1 present in bread occurs on toasting.

PasteurisationPasteurisation• Nutrient losses are generally small.• HTST and UHT result in greater nutrient retention

for those nutrients affected by the pasteurisation treatment( thiamine, vit C, vit B12)

Smoking• Usually follows salting or curing.• Reduces the oxidative changes that take place in

fats, proteins and vitamins- acts as an antioxidant.

• Causes nutrient loss due to the associated heat, flow of gases and interaction of the smoke components with proteins.

MillingMilling

ConcentrationConcentrationThe nutrient changes that occur

during concentration will depend on :

the contents of the mixture and the temperature at which the

process takes place.There is a decreased water

content and corresponding increase in other nutrients.

SaltingSaltingResults in liquid exuding from the

flesh, taking with it some of the water-soluble proteins, vitamins and minerals.

Some proteins are also denatured by the salt.

BlanchingBlanchingThe nutrient losses will depend on

several factors:the food item surface area exposedthe method used (steam blanching or hot

water blanching)contact timeamount of agitation

Losses of Nutrients during Blanching

NOTE: When blanching fruits or vegetables the addition of sodium bicarbonate(or other alkali) to the blanching water for preserving the colour should be considered carefully, as while preserving the colour, it also has the effect of softening the texture of the vegetable and increasing destruction of vitamin C and thiamine.

SulphitesSulphitesAct as an anti-oxidant and prevent

browningIncreases the loss of thiamine. Use of sulphite on meat is restricted in

some countries and there is also a limit to the amount that is used in the preservation of fruits and seafood, as this may result in allergic reactions in some consumers.

FreezingFreezingThe major nutrient losses that occur in

frozen foods are not due to freezing as such but due to the blanching that occurs before freezing, and then during subsequent thawing and cooking.

It is important that frozen foods are stored at -18°C to prevent their rapid deterioration. If this temperature is not maintained then some nutrient losses will occur, which are not regained by refreezing.

CanningCanningNutrient losses occur from destruction

during heating and storage stages.Water-soluble vitamins and minerals,

may dissolve in the water in the can, but they are lost only if this liquid is not consumed.

We can reduce losses of vitamins during storage by storing the cans in a cool place.

IrradiationIrradiation

DehydrationDehydrationLosses during the drying process will depend on: • preparation procedures before drying (e.g.

slicing, blanching)• drying temperature, • drying time, • storage conditionsNutrient losses during drying can be decreased

by :• drying at a low temperature and shortening

drying time. • After drying ensure that foods are stored under

dry conditions and at low oxygen levels.

Demerits:

Cutting, trimming and Cutting, trimming and peelingpeeling

. Discarding the outer leaves of vegetables such as cabbage, spinach and lettuce and peeling fruits and vegetables such as apples, peaches, pears, potatoes and carrots, lead to a disproportionate loss of many vitamins- as vitamins and minerals are presesnt just beneath the skin.

Effect of Processing on Effect of Processing on NutrientNutrient

How To Minimize Water Input How To Minimize Water Input and Outputand Output

Choose fresh foods that are not over-ripe, bruised, cut or scraped.

Store foods in a cool, dark place.Unless the peel or outer layer is unpalatable,

damaged or contaminated, cook the food whole.If it is necessary to slice the raw food. then try to

keep the pieces as large as possible.When boiling, add the raw food to the boiling

water rather than to cold water.Use the smallest amount of water possible; it is

not necessary to cover the food. Steaming is a way of cooking with a minimum amount of water.

If possible use the cooking water for gravies, sauces or soups as it is a source of water-soluble vitamins and elements (minerals).

Cook for the minimum time necessary to make the food palatable and safe. Once cooked, eat as soon as possible. Do not keep the food warm for long periods.

Do not use baking soda to help keep the green colour of vegetables, as this increases loss of vitamin C.

Do not use copper utensils. (Copper helps to destroy vitamin C.)

Scope of Food Processing

Food and crop processing largest industry in most countries.

The small-scale food processing sector: - is a major source of employment,

- adds value to crops by processing,- is a major source of food in the diet,- in some cases, by export, earns valuable foreign exchange,- provides opportunities for import substitution,- benefits a large number of poor people, such as farmers, packaging suppliers and vendors.

Food SpoilageFood Spoilage

Loss or damage of original nutritional value, texture and flavour of the food making it harmful to people and unsuitable to eat.

Causes:Causes:Two main causes:

Natural decay in foodsContamination by micro-organisms

Natural decay in FoodNatural decay in Fooda) Moisture Loss: mostly occurs in fruit and vegetables

which contain large amounts of water. vegetable or fruit shrinks in size,

becomes limp and its skin becomes wrinkled and leathery

occurs in other foods like meat, fish, cheese, due to evaporation of water from the surface.

b) Enzyme action:Enzymes are sensitive to heat. active in temperatures found in a kitchen,

very slightly active at very low temperatures such as those found in the freezer

activity of these enzymes stops when they are heated above 70 oC.

Some enzymes remain inactive until the food is harvested or slaughtered. Once activated, such enzymes speed up the process of decay by breaking down the tissues and components of the food in the various ways such as oxidation, browning and ripening.

Oxidation : when food comes into contact with oxygen) the enzymes cause the destruction of certain nutrients e.g. vitamin c, thiamine and carotene.

Browning: Enzymes cause browning in certain foods the moment they are exposed to air

Ripening: Enzymes are involved in the process that causes ripening in certain foods such as fruits and vegetables.

Microbial ActionMicrobial Action Mainly due to:

Fungal spoilage(yeasts and moulds) Bacterial spoilage

Fungal Spoilage:Fungal Spoilage: YEAST : microscopic single celled plants, found in the

air and soil, and on the surface of fruit. there are two types of yeasts : true yeast

and false yeast. True yeast  metabolizes sugar producing

alcohol and carbon dioxide gas. This is known as fermentation.

 False yeast grows as a dry film on a food surface, such as on pickle brine. False yeast occurs in foods that have a high sugar or high acid environment.

Some can grow without the presence of oxygen : can cause food spoilage in syrups, fruits, fruits juices and jam especially as they can survive without air.

Yeast grow best at temperatures between 25°C and 30°C.

Extreme heat destroys all yeasts and most are destroyed at temperatures above 60°C.

MOULDS:Grow in filaments forming a tough mass

which is visible as `mould growth'. Moulds form spores which, when dry, float through the air to find suitable conditions where they can start the growth cycle again.

Mould can cause illness, especially if the person is allergic to molds.

Usually though, the main symptoms from eating mouldy food will be nausea or vomiting from the bad taste and smell of the mouldy food.

Moulds grow most readily in most conditions, at temperatures between 20°C and 40°C.

They grow on a variety of foods, particularly meat, cheese, fruit and bread, especially if the food is stored in damp conditions.

Moulds may remain active at the low temperatures of a refrigerator but they are destroyed by heat above 70°C.

They also like a slightly acid medium and this is why they attack citrus and the surface of jams.

Some examples of fungal Some examples of fungal spoilage:spoilage:

Bacterial Spoilage:Bacterial Spoilage: may grow under a wide variety of conditions. They can be divided into: spore-

forming and non spore-forming. Bacteria generally prefer low acid foods like

vegetables and meat. In order to destroy bacteria spores in a

relatively short period of time, low acid foods must be processed for the appropriate length of time at 116°C (240°F) in a pressure canner.

Eating spoiled food caused by bacteria can cause food poisoning.

Some examples of bacterial Some examples of bacterial spoilagespoilage

Effect of spoilage on various Effect of spoilage on various Food CommoditiesFood CommoditiesProtein food Undergo putrefaction. This is the situation

where protein foods rot, and produce very bad smell

Fats and oils Undergo rancidity. This is the condition

where food containing fats and oils begin to smell and tasted bad when they are old.

Carbohydrates Cooked cereals become marshy and

slimy when affected by micro-organisms. This condition is known as serenasis.

Flour products smell and taste unpleasant when they are spoilt. They are described as being stale.

Fruits and vegetables They rot, ferment and decay.

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