LECTURE 1

Introduction to food processing and preservation

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Food

• What is food

• Where does food come from?

• Food chain

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Primary production

Transportation, storage

Processing

Storage, distribution

Retail

Consumer

Consumption

Food processing• methods and techniques

used to transform raw ingredients into food or

to transform food into other forms for consumption by humans or animals either in the home or by the food processing industry.

.e.g. Takes clean, harvested crops or slaughtered and butchered animal products and uses these to produce attractive, marketable and often long shelf-life food products.

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Food processing

Similar processes are used to produce animal feed.

Extreme examples of food processing include the delicate preparation of deadly fungi fish or preparing spice food for consumption under zero gravity

• it encompasses all steps that food goes through from the time it is harvested to the time it reaches the retailer shops or the final consumers.

e.g. Picking of vegetables or fruits from the garden sorting and washing before they are sent to the market

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Food processing

• Some processing methods convert raw materials into a different form or change the nature of the product as in the manufacture of sugar from sugar cane, oil from sunflower and cheese from milk

• Processing may involve an extremely complex set of techniques and ingredients to create ready to eat convenience foods

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Food preservationProcessing techniques that make the food fit

for consumption. i.e. the process of treating and handling food to stop or slow down Food spoilage, loss of quality, edibility or nutritional value and thus allow for longer food storage.

includes chemical and physical changes such as bruising and browning, infestation by insects or other pests or growth of micro-organisms such as bacteria yeast and moulds.

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Food preservation• Preservation usually involves preventing the

growth of bacteria, fungi (such as yeasts), and other micro-organisms as well as retarding the oxidation of fats which cause rancidity.

• However some methods work by introducing bacteria, or fungi to the food.

• can also include processes which inhibit visual deterioration, such as the enzymatic browning reaction which can occur naturally during food preparation.

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Food preservation• preserved food should retain their

colour and taste. (i.e. colour and taste of food which is present at the time of preservation should not change.) e.g. preserving grapes as raisins.

• should not change texture. But this applies to some of the foods and processing technique/method

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FOOD PROCESSING METHODS

Removal of unwanted outer layers,

Chopping or slicing e.g. carrots

Mincing and macerating meat

Liquefaction, such as to produce fruit juice

Fermentation e.g. in beer breweries

Cooking,

Mixing addition of gas such as air entrainment for bread or gasification of soft drinks

Proofing –activating until light or smooth

Spray drying

Pasteurization

Packaging

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History of food processing

• Prehistorically food processing involves different activities such as slaughtering, fermenting, sun drying, preserving with salt, and various types of cooking (such as roasting, smoking, steaming and oven baking).

e.g. Salt-preservation – warrior and sailors diet

• Evidence for the existence of these methods exists in the writings of the ancient Greek, Chaldean, Egyptian and Roman civilizations as well as archaeological evidence from Europe, North and South America and Asia.

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History of food processing

These tried and tested processing techniques remained essentially the same until the advent of the industrial revolution. Examples of ready-meals also exist from pre industrial revolution times such as the Cornish pasty/humburger and the Haggis/sausages

In the 19th and 20th century modern technology was largely developed to serve military needs.

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History of food processing

• In 1809 Nicolas Appert invented a vacuum bottling technique that would supply food for French troops, and this contributed to the development of tinning and then canningby Peter Durand in 1810.

• Although initially it was expensive and somewhat hazardous due to the lead used in cans, canned goods would later become a useful container for food preservation around the World.

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History of food processing• In 1862, Pasteurization, was discovered by Louis

Pasteur. This was a significant advance in ensuring the micro-biological safety of food.

• In the 20th century, World War II, the space race and the rising consumer society in developed countries (including the United States) contributed to the growth of food processing with such advances as spray drying, juice concentrates, freeze drying and the introduction of artificial sweeteners, colouring agents, and preservatives such as sodium benzoate.

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History of food processing• In the late 20th century products such as dried instant

soups, reconstituted fruits and juices, and self cooking meals

• In Western Europe and North America, the second half of the 20th century witnessed a rise in the pursuit of convenience; food processors especially marketed their products to middle-class working wives and mothers. Frozen foods found their success in sales of juice concentrates and “TV dinners”

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History of food processing• Processors utilized the perceived value of time to appeal

to the post war population, and the same appeal contributes to the success of convenience foods today.

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Benefits of food processing and preservation

• Mass production of food is much cheaper overall than individual production of meals from raw ingredients.

• Reaches areas where the food item is not grown

• Easing marketing, storage and distribution tasks

• Add variety to our meals

• Increasing food consistency (season availability0

• Toxin removal

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Benefits of food processing and preservationmakes many kinds of foods safe to eat by de-

activating spoilage and pathogenic micro-organisms.

Improves the quality of life for people with allergies, diabetics, and other people

can also add extra nutrients such as vitamins

Processed foods are often less susceptible to early spoilage than fresh foods

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Limitations/drawbacks

Can lower the nutritional value of foods, and introduce hazards not encountered with naturally-occurring products

Processed foods often have a higher ratio of calories to other essential nutrients than unprocessed foods, a phenomenon referred to as “empty calories”. So-called junk food, produced to satisfy consumer demand for convenience and low cost, are most often mass produced processed food products.

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Limitations/drawbacksMay cause adverse health effects.-

Preservatives such as nitrites or sulphites.

Failures in hygiene standards in “low-level” manufacturing facilities that produce a widely-distributed basic ingredient can have serious consequences for many final products

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Performance parameters for food processing

• Hygiene e.g. measured by number of micro-organisms per ml finished product

• Energy consumption, measured e.g. by “ton of steam per ton of sugar produced”

• Minimization of waste, measured e.g. by “percentage of peeling loss during the peeling of potatoes

• Labour used, measured e.g. by “number of working hours per ton of finished product”

• Minimization of cleaning stops measured e.g. by number of hours between cleaning stops”

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Trends in modern food processing • Cost reduction

• Health

• Hygiene -application of industry and government endorsed standards to minimize possible risk and hazards e.g in USA- HACCP

• Efficiency:

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Principle of food processing and preservation

The following principles are involved in various methods,

Prevention or delay of microbial decomposition (control of microorganisms)

Prevention or delay of self decomposition of the food (control of enzymes )

Controlling insects, rodents, birds and other physical causes of food deterioration

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Prevention or delay of self decomposition of the food

Controlling enzymes by:-

• Inactivating endogenous enzymes

• Preventing or delaying chemical Reactions in the food

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Prevention or delay of microbial decomposition

• By keeping out microorganisms (Asepsis)

• By removal of microorganisms. This is done by removing air, water (moisture), filtration, lowering or increasing temperature, increasing the concentration of salt or sugar or acid in foods

• By hindering the growth and activity of microorganisms e.g. by low temperature drying, anaerobic conditions or chemicals

• By killing the microorganisms e.g. by heat or radiations

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Growth curve of microbial cultures

Whenever microorganisms are added to a food and conditions are favourable the organisms will begin to multiply and will pass through a succession of phases. When counts of organisms are made periodically and the results are plotted with logarithms of number organisms per millilitres as ordinates and time units as abscissas, a growth curve is obtained as illustrated in the following figure:

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Growth curve of microbial cultures

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Application of microbial growth curve to food preservation

• It is especially important in food preservation to lengthen as much as the lag phase and the phase of positive acceleration. This can be accomplished in different ways.

1. reducing the amount of contamination.

2. By avoiding the addition of actively growing organisms (logarithmic phase).

3. By one or more unfavourable environmental conditions

4. By actual damage to organisms by processing methods such as heating or irradiation.

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