EFFECT OF FOOD PROCESSING ON NUTRIENT CONTENT OF FOOD

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• EFFECT OF FOOD PROCESSING ON NUTRIENT CONTENT OF
  FOOD
• FOOD SPOILAGE
• By
• AYUSHI JAIN
• 2010BT04

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FOOD 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

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AIM

• 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)

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Different Methods Employed

• Various heat processes such as
• Cooking
• Baking
• Frying
• Microwave cooking
• Toasting
• Pasteurisation
• Smoking

• Milling
• Concentration
• Salting
• Blanching
• Addition of preservatives (sulphites, etc)
• Freezing
• Canning
• Irradiation
• Dehydration/drying

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..Continued

• Cutting, trimming and peeling
• Soaking, germination and fermentation
• Controlled atmosphere storage, ripening and waxing

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Effect of Food Processing on Nutrient Content

• Depend on
• Chemical stability of nutrient content
• Extent of processing
• Environmental factors
• Form in which the foods are delivered

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Heat Processing

• Merits
• improves the digestibility of foods, making some
  nutrients more available.
• Demerits
• Malliard reaction(non-enzymatic browning)
• Affects bioavailability of minerals
• Loss of vitamins

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Cooking

• Merits
• 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

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• Demerits
• Leads to most important nutrient losses
• Mineral 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.

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Baking
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Frying
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Microwave 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.

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Pasteurisation

• 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.

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Milling
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Concentration

• The 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.

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Salting

• Results 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.

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Blanching

• The nutrient losses will depend on several
  factors
• the food item
• surface area exposed
• the method used (steam blanching or hot water
  blanching)
• contact time
• amount of agitation

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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.
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Sulphites

• Act as an anti-oxidant and prevent browning
• Increases 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.

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Freezing

• The 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
  -18C to prevent their rapid deterioration. If
  this temperature is not maintained then some
  nutrient losses will occur, which are not
  regained by refreezing.

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Canning

• Nutrient 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.

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Irradiation
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Dehydration

• Losses during the drying process will depend on
• preparation procedures before drying (e.g.
  slicing, blanching)
• drying temperature,
• drying time,
• storage conditions
• Nutrient 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.

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Demerits
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Cutting, trimming and peeling

• . 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.

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Effect of Processing on Nutrient
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How To Minimize Water Input and 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.

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• 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.)

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• 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.

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Food Spoilage

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

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Causes

• Two main causes
• Natural decay in foods
• Contamination by micro-organisms

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Natural decay in Food

• 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.

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• 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.

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• 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.

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Microbial Action

• Mainly due to
• Fungal spoilage(yeasts and moulds)
• Bacterial spoilage

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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.

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• 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 25C and
  30C.
• Extreme heat destroys all yeasts and most are
  destroyed at temperatures above 60C.

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• 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.

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• Moulds grow most readily in most conditions, at
  temperatures between 20C and 40C.
• 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 70C.
• They also like a slightly acid medium and this is
  why they attack citrus and the surface of jams.

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Some examples of fungal spoilage
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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 116C (240F) in a pressure canner.
• Eating spoiled food caused by bacteria can
  cause food poisoning.

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Some examples of bacterial spoilage
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Effect of spoilage on various Food Commodities

• Protein 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.

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• 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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