Transcript Slide 1

Impact of Food Processing
on Quality
Paul Nesvadba
The Robert Gordon University
Aberdeen, Scotland, UK
CHISA 2004, Prague, 23 August 2004
Robert Gordon University
St Andrew Street, Aberdeen
•Physicist
- Food processing
- Food Physics
EU project EVITHERM
European Virtual Institute for Thermal
Metrology
www.evitherm.org
Food processing
Significant
effect on food properties
hence
Significant
impact on food quality
Food
- becoming a global commodity
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Legislation
Competition
Food
- connection to Health
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Beneficial v. Detrimental (“Elixir of Life”)
“Functional” foods
“Smart” foods
Food Production - Components
Generation of Bio-
Recycling
mass
Human
Products resulting
from Agriculture
Consumption
Livestock
Storage
Process and
transformation
Quality Control
Packaging
Advertising
Storage
Distribution
Waste
Why are most foods processed?
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To increase digestibility, nutritive and
health value
To attract & satisfy the consumers, to
develop the food market
To preserve foods
To maintain or enhance the quality
What is the Food Quality ?
-> “Fitness for purpose”
Hygienic
Chemical
( Ex: No salmonella)
Physical
( Ex: Good texture )
( Ex: No toxin)
FOOD
QUALITY
Sensory ( Ex:
Pleasant flavour)
Energy, Nutrition,
Health Promotion
Consumer
choice
(Ex: Vitamins )
Convenient
(Ex : prepared
meals)
Convenience - Ready Meals
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Convenience
Less time for
preparation
Economical for single
person or small
families
Reduced wastage
Demographic trend
Use of the Internet
How to ensure
Food Quality / Safety?
Quality control from “farm” to “fork”
• HACCP (Hazard Analysis and Critical Control Point)
• Appropriate processing methods
•Traceability and
labels
(Linked to Real-time delivery /
inventory control / management)
Meeting the Requirements
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Safety and preservation
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Pasteurisation, Appertisation and Sterilisation
Screening for physical and chemical
contaminants
Adding chemical conservatives
Modification
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Novelty, “added” properties
Digestibility, Nutritive value
Modifying Food Properties
• Agriculture
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Genetic Modification of
plants
DNA
• Food Processing
Production of bio-molecules
and bio-polymers by modified
genetic organisms;
transformation
• Incorporation of additives
Enhancing nutritive and health benefits
Benefits of ingesting food
Energy
FOOD
DNA /
RNA
Repair
Building of
body
component
during growth
Prevention or
reduction of RNA /
DNA damage –
“anti-mutagens”
What is Preservation ?
• Destruction of micro-organisms
and spores
•Inactivation of enzymes
Salmonella
• Slowing the rate of chemical
reactions such as oxidation
Browning of an apple
due to oxidation
Other reasons for
Food Processing
• Other safety reasons
• Destruction of toxins
• Improving properties
• physico-chemical
• sensory
• aesthetic
How to produce safe foods ?
 Thermal processing
 Diminution of the water activity by
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- Drying and Freezing
- Adding molecules ( e.g: NaCl)
 High pressure
 Ultraviolet light
• Ozone
 Electric pulses
 Incorporation of additives
Thermal processing
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95% of staple foods require cooking
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Processing by heating is “as old as fire”
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Domestic cooking
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Half of the world’s population uses solid fuel
as source of heating for food
Pasteurisation
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First time used by Pasteur in
the 19th century.
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Heating 30 minutes at 63°C or
12 seconds at 72°C
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Destruction of the pathogen,
food deteriorating floras.
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Destruction of deteriorating
enzymes
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Conservation of the nutritious
properties
(vitamins, proteins, flavour...)
Pasteur
Appertisation
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Nicolas Appert invented
it in 1810
In general, Heating
between 110 and 130
degrees during 20min
to an hour, in glass or
aluminium cans
The results are the
same as for
Pasteurisation but the
time of conservation is
longer
Comparison of the protein composition
in Fish flesh
acid amine
Original
Appertised
Isoleucine
5,6
5,6
Leucine
8,0
8,1
Lysine
9,0
9,1
Méthionine
3,1
3,0
Phénylalanine
3,8
3,9
Thréonine
5,1
5,2
Tryptophane
1,1
1,0
Valine
5,3
Sterilisation
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Heating for 3s between
135°C and 150°C
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Long time of conservation
Destruction
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of some
Destruction of all the micro interesting nutritious
properties
organisms and enzymes
Vitamines
Milk without any heat
treatment
Milk after sterilisation
A (mg)
4,04
0,55
D (µg)
21
0,30
C (mg)
132
0,8
B1 (mg)
3,80
0,30
B2 (mg)
16,30
1,48
B6 (mg)
6
0,39
Quality Retention during sterilisation
n = log ( N0 / N )
Time
n=6
n=9
Vitamin B1
destruction
10%
Micro-Organism
Inactivation
3%
Temperature
Modelling of the effect of Heating
Input Data
= contents of:
•Water
•Protein
•Fat carbohydrates
•Minerals
COSTHERM, a computer
program for the prediction
of Thermophysical
properties
-Temperature range :
-40 to 40 degrees
-Accuracy: 10%
•Density
•Initial freezing point
Temperature Model
Output: Specific Heat, Enthalpy,
Thermal Conductivity, Ice fraction
Micro- or kinetic
model
To Refrigerate (4 - 8 C)
Slow down the development of
 micro organisms
 bio-chemical degradation reactions
What happens in a non-packaged product
Modelling microbial growth
To freeze (-18 to -40 C)
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Decrease the
temperature below -18 C
in a few minutes, the
quickest possible.
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Stop food degradation
reactions
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Prevent the development
of micro organisms
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Long time of conservation
Cell damage during
freezing
• high solute concentration
(low aw)
•membrane shrinkage and
damage
•intracellular ice (?)
High pressure
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Covalent bonds are not strongly
affected - vitamins preserved
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Inactivation of enzymes
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Inactivation of micro-organisms
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Some enzymes are modified, “hardened”
Disruption of cell membrane cells - “lysis”
Spores are resistant
Thermodynamic effects
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Pressure shift freezing and thawing
Inactivation of micro-organisms
Inactivation of enzymes
Ionisation
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Creation of ions in the irradiated food,
by an gamma or electron beams
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Maximum dose: 10 kGy
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Destruction of the pathogen, food
deteriorating floras.
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Destruction of deteriorating enzymes
Logo of ionized food
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Conservation of the nutritious
properties (vitamins, proteins, flavour, except
lipids...)
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Consumer resistance
Electric pulses
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Same action high
pressure and
heating
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Disruption of the cell
membrane
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Electroporation
Schematic configurations of the three most
used PEF treatment chambers
Dependence of microbial survival fraction on the A)
electric field and B) treatment time. Curves a correspond
to resistant micro-organisms and curves b to sensitive
micro-organisms S, survival fraction; N, microbial
count; E, electric field; b, kinetic constant; t, time.
Subscripts: 0, initial; c, critical; t, time; e, electric field
Incorporation of additives
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butylated hydroxytoluene (in some potato chips,
salted peanuts, breakfast cereals and many other
things)
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calcium disodium ethylene diamine tetra acetate
(in salad dressings and some drinks)
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sodium L-ascorbate (a form of vitamin C)
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E-numbers
Incorporation of Salt - NaCl
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Ubiquitous
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natural presence and a major additive
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Preservation by lowering Aw
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Possible raising of blood pressure
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Tendency to decrease salt content
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High Pressure Treatments can assist
NaCl Structure
Anti Oxidants
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Diseases
 Cancer
 Cardiovascular
 Neurological
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Antioxidants
 L-ascorbic acid
 Carotenoids
 Flavonoids & other polyphenolic
compounds
Examples of widely used preservatives in the EU
E-Number
Substance / class
Some foodstuffs in which they are used
E 200-203
Sorbic acid and
sorbate compounds
Cheese, wines, dried fruit, fruit sauces,
toppings
E 210-213
Benzoic acid,
and benzoate
Pickled vegetables, low sugar jams and
jellies, candied fruits, semi preserved
fish products, sauces
Sulphur dioxide and
sulphite
Dried fruits, fruit preserves, potato
products, wine
E 220-228
compounds
E 235
Natamycin
Surface treatment of cheese and
sausage
Anti oxidant properties
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Relatively unstable
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Processing or storage can improve
antioxidant activity – e.g. polyphenols at an
intermediate oxidation state can scavenge
radicals more than in non-oxidised state
Additive Free Foods
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Salt – mainly as a flavour enhancer in
western world
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Nitrites
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Phosphates
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Monosodium Glutamate
Packaging
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Most foods are packaged
 Hygiene
 Stability of the product
 Storage container
 Presentation to the consumer
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Discarded packaging
 Waste
 Recycling
Edible packaging
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Film and coatings based on:
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Polysaccharides
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Lipids
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Cocoa butter, waxes
Proteins
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Cellulose, starches, gums
From milk, soya, cereals
Functions
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barrier for moisture, oxygen, fat (b. layers)
volatiles
Can carry antioxidants and antimicrobials
Example of specific packagings
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For the food degraded by
oxidation (Ex: Fruits)
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Packaging with modified
atmosphere:
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Less oxygen
More carbon dioxide
Well defined humidity
•Packaging with controlled
atmosphere ( All the parameters
Modified atmosphere
packaging
are well known and are monitored)
to extend shelf life.
•Vacuum Packaging( No
Oxidation)
Sensors for Food Quality
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Imaging (computer vision)
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Classification, Inspection
Density
Viscosity
Spectroscopic Techniques
Biosensors / Immunosensors
Bio-processing – Added Value
Products
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Functional Foods
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Interface to Pharmaceuticals
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Bio-separation of biomolecules
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Immunoglobulins
Purification of proteins from blood serum
Example - Functional Foods
- Purdue University
• By changing chicken feed supplements
developed
•Eggs that include more of two”good” fats,
•conjugated linoleic acid (CLA) and
•docosahexaenoic acid, a type of omega-3
fatty acid.
Conclusions
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Food processing
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Essential for human well-being and health
Influenced by the state of the society
Driven by
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consumer demand
Understanding of the connection between food,
nutrition and health
New physico-chemical processes
Genetic modification
Thank you for your
attention