Transcript Current Trends in Processing: Preservation of Food with ionizing

CURRENT TRENDS IN PROCESSING:
PRESERVATION OF FOOD WITH IONIZING ENERGY
CHAPTER 21
 Describe chemical and nutrient changes irradiation causes in food products
 Analyze advantages and disadvantages of food irradiation as a preservation method
 Compare reduced oxygen packaging with other packaging an
TERMINOLOGY
 Radiation is the energy
 Irradiation is the process!
 Electromagnetic spectrum ( of radiation)
 Organized scale of electromagnetic radiation:

radio waves, visible light, microwaves, ionizing radiation
 Frequency, wavelength, energy value
 (penetrating power)
LOW WAVE LENGTH, LOW ENERGY
Bacteria and
viruses
Penetrates skin
Microwave ovens
Visible
( sunburn due to
short penetrating
waves)
ELECTROMAGNETIC ENERGY: MICROWAVE ENERGY
(LONG WAVELENGTHS – LOW PENETRATION)
 In food- cause polar molecules to vibrate
 Heat created by intermolecular FRICTION
 Heat then conducted to neighboring molecules
 Microwaves are absorbed up to a depth of 5 to 7.5 cm ( 1 to 1.5 inches)
 Microwaves pass through PAPER, PLASTIC, GLASS
 Reflected by metals
 Attracted to fat, water and sugars
 Cooks unevenly so needs rotated, stirred or rearranged during cooking
MICROWAVE OVENS
https://www.youtube.com/watch?v=XZzdNjm1JzU
invention
https://www.youtube.com/
watch?v=4h1ESUz2H3E
ELECTROMAGNETIC ENERGY: IONIZING RADIATION
( SHORT WAVELENGTHS- HIG PENETRATING POWER)
 Ionizing radiation means:
 A. GAMMA radiation from Cobalt-60 or Cesium-137 source
 B. X-RAY from machine source operated at <10 MeV

( Mega electron volts)- voltages used on food
 C. ELECTRONS from machine source operated as < 10 MeV
 (stream of electrons accelerated to a 99.9% the speed of light)
FOOD IRRADIATION
 “GRAY” Amount of energy absorbed by the food treated with irradiation
 1 GRAY (Gy) = 1 joule of energy per kg of food
 1000 Gy= 1kilogray or 1kGy
 Most countries regulate 10 kGy or less of absorbed energy
DOES IRRADIATION INDUCE RADIOACTIVITY IN FOODS?
 Irradiation uses ionizing energy
 Enough energy to change atoms by “knocking” an electron from the outer orbit which forms ions (ionizing
energy)
 Knock out- breaks the dna from the bacteria
 Not enough energy to penetrate the nucleus and split atoms ( this would cause radioactivity)
 Food can never become radioactive from irradiation USING APPROVED ENERGY SOURCES.
DOES IRRADIATION INDUCE RADIOACTIVITY IN FOODS?
 To become radioactive, food would need to be
exposed to a minimum of 15 MeV of energy
 Energy output: colbalt 60, cesium 137, and e-beam accel.- carefully regulated
 Maximum energy uotputs of 5 or 10 MeV
 Too low to induce radioactivity in foods
THE FOOD IRRADIATION PROCESS
1. Conveyor system moves prepackaged food
in boxes (pallets)
2. Food is carried into a chamber with irradiation
source (eg cobalt 60)
3. Absorbed dose depends on amount of time food
is exposed to the irradiation source.
Dosimeters are placed with the food to measure
The dose received (in kGy)
PRESERVATION EFFECT
 1. Direct effect

Direct hit of ionizing energy upon genetic material of microbial cells

Eg. Break bonds of DNA OF BACTERIA IN THE FOOD

DEPENDS ON DOSE, MICROORGANISM, REPAIR MECHANISM AVAILABLE…..

RANDOM, EXTENSIVE DAMAGE

May cause development of resistant bacteria and microorganisms

If radiation is not hitting on the same place in the dna, then the molecules is less likely to mutate
BASIS FOR FOOD PRESERVATION BY IONIZING RADIATION
 2. Indirect effect

Ionizing energy interacts with water in the food

Absorbed energy will dislodge electrons from water molecules

Ionizing energy  absorbed by food (water) ion pairs and free radicals-reactive

Damage to key proteins and cell membranes

“free-radicals” normal aging process when cells die
FREE RADICALS ….(CONT)
 FR are not unique to “irradiated foods”
 Also produced within our bodies and other living tissues

As part of normal metabolism

Oxidative reactions in foods ( unsaturated fats)

Mechanisms (chemical and enzymatic) within human body for inactivation of free radicals

Antioxidants/supplements prevent free radicals from forming in the body which delays cell death
CHANGES DURING FOOD IRRADIATION?
 Radiolytic products
 Benzene and derivatives
 Also in non-irradiated foods
 Low concentrations after irradiation
 Alkylcyclobutanones (ACBs)
 “unique” radiolytic products
 Most from fatty acids
 Toxic doses found in irradiated foods?......not known yet
WAYS TO MINIMIZE UNDESIRABLE EFFECTS/ CHANGES OF FOOD
IRRADIATION
 Frozen state

Lower production and mobility of free radicals
 Vacuum

Minimize oxidative changes
 Free radical scavengers

React with the free radicals ( affinity for Free Radicals)

Vitamins E , C
 *** Irradiation is not heating the food…..There is no friction
TYPICAL NON-FOOD APPLICATIONS OF IRRADIATION
 Band aids
 Diaper wipes
 Pet treats
 Wound cares
 Cosmetics
 50% of all medical devices
 Baby bottles
 Animal vaccines
 Computer chips
 Contact lenses/ cleaning solutions
TYPICAL FOOD APPLICATIONS (INTERNATIONAL)
DOSE
<1 kGy
Radurization
1-10 kGy
Radicidation
10-50 kGy
Radappertization
Purpose
•
•
•
•
•
Inhibit vegetable sprouting
Kill insects and larva
Slow ripening
Eleviate parasites
Eliminate spoilage causing
microorganisms
Eleminate pathogenic bacteria
(salmonella, E.coli0157:H7
KILLS PATHOGENS
Commercially sterilizes food
Examples
Potatoes
Wheat
Bananas
Pork
Chicken, ground beef, fruit and
vegetables, fresh strawberries
Sterilizes hospital diets,
Space mission foods
SHELF LIFE EXTENSIONS OF STRAWBERRIES
RESISTANCE/ DESTRUCTION OF MICROORGANISMS
BY IONIZING ENERGY
 Concept of Decimal reduction Time ( D-Value) in thermal processing- also applies to radiation
 D10 value =

Dose (kGy) of ionizing energy needed for a 90% decrease ( 1 log reduction) of microorganism population
REQUIRED IRRADIATION DOSE (KILOGRAYS)
FOR A 5D OR 12D PROCESS
Pathogen
D10 values
(kGy)
Dose for a
5D process
Dose for a
12D process
E. Coli 0157:H7
0.24
1.2
2.9
Listeria
Monocytogenes
0.45
2.2
5.4
Salmonella
0.5
3.0
7.2
C. Botulinum spores
3.56
18
>.40
0.45 x 5D=
* Not optimal for C. Botulinum, but okay for other pathogens
.045 x 12D=
RESISTANCE OF ENZYMES TO IONIZING ENERGY
 Most food enzymes are even more resistant than C. botulinum spores
 Will need nearly 200kGy!
 Can we use irradiation to inactivate enzymes?

Not the best…. But may need to blanch before irradiating
IRRADIATED FOOD- LABELING
The Food and Drug Administration (FDA) establishes regulations
for labeling of irradiated foods.
Labels must contain the words
"Treated with Radiation" or
"Treated by Irradiation" and
display the irradiation logo, the Radura.
The petals represent the food, the central circle the radiation source, and the broken circle illustrates the rays from the energy source
Retail Foods
FDA requires labeling of packaged, irradiated food sold at retail stores. Irradiated, whole foods sold in bulk, such as fruits and vegetables, also must display the label.
No label is required for food products that contain irradiated ingredients, such as spices, as long as the entire product has not been irradiated.
Wholesale Foods
Irradiated foods sold at the wholesale level also must be labeled. However, both the shipping container and the invoice or bill of lading must
display the statement,
"Do not irradiate again." FDA has not evaluated products that have been irradiated more than once.
Restaurant Foods
FDA does not require labeling of irradiated food served in restaurants.
WHAT APPLICATIONS ARE CURRENTLY APPROVED IN THE UNITED
STATES ( SEE TEXT)
 Decontamination ( microbial, parasite control) of

Pork

Fresha dnfrozen poultry

Poultry feed

Fresh and frozen red meat

Shell eggs

Animal feed, pet feed, spices

Vegetable seasoning (dried)
 Sterilization of

Meat, frozen packaged- for NASA space missions only