Food Irradiation Topic 8 PDF

FOOD IRRADIATION ELECTROMAGNETIC SPECTRUM ELECTROMAGNETIC SPECTRUM DEFINITION  Food irradiation: A process whereby food is exposed to a carefully controlled amount of ionizing radiation at a specific time to achieve a certain desirable objectives.  Defined as food additives ...

FOOD IRRADIATION ELECTROMAGNETIC SPECTRUM ELECTROMAGNETIC SPECTRUM DEFINITION  Food irradiation: A process whereby food is exposed to a carefully controlled amount of ionizing radiation at a specific time to achieve a certain desirable objectives.  Defined as food additives  Effective ways for:  Sterilization of packaging material, pathogen destruction (Salmonella sp), prevent spoilage by microorganism, delay ripening, inactivation or control of parasites, insect disinfestation, inhibit sprouting of certain vegetables.  Also known as ‘cold pasteurization’, ionizing radiation or electric pasteurization as it can accomplish the same objective as thermal pasteurization of liquid foods, for example milk, without any substantial increase in product temperature.  Used in more than 40 countries for over 100 food items, including potatoes, onions, cereals, flour, fresh fruit and poultry. ADVANTAGES OF IRRADIATION  Reduceor eliminate disease-causing microorganism  Thenutritional value is essentially unchanged  The food does not become radioctive → irradiation is a safe and effective technology that can prevent many foodborne disease IRRADIATION PROCESS  Theprocess involves exposing the food either packaged or in bulk, to carefully controlled amounts of ionizing radiation for a specific time to achieve certain desirable objectives. MECHANISM OF IRRADIATION  When microbes present in the food are irradiated, the energy from the radiation breaks the bonds in the DNA molecules, causing defects in the genetic instructions.  Unless this damage can be repaired, the organism will die or will be unable to reproduce.  It matters if the food is frozen or fresh, because it takes larger radiation dose to kill microbes in frozen foods. EFFECTIVENESS OF IRRADIATION  The effectiveness of the process depends also on the organism’s sensitivity to irradiation, on the rate at which it can repair damaged DNA, and especially on the amount of DNA in the target organism  EXAMPLE:  Parasitesand insect pests, which have large amounts of DNA, are rapidly killed by an extremely low dose of irradiation.  Ittakes more irradiation to kill bacteria, because they have less DNA.  Viruses are the smallest pathogens that have nucleic acid, and they are, in general, resistant to irradiation at doses approved for foods. → Thus, it prolong the shelf life of fruits and vegetables because it inhibits sprouting and delays ripening. TWO MECHANISMS – MICROBIAL INACTIVATION 1. Direct interaction of the radiation with cell components The primary target of ionizing radiation: chromosal DNA Effect on cell membrane structure Cause microbial inactivation and growth inhibition 2. Indirect action from radiolytic products, such as the water radicals (hydrogen atoms and hydroxyl radicals) TYPES OF RADIATION USED IN FOODS  Gamma rays  Accelerated electron X rays GAMMA RAYS  Generated from spontaneous disintegration of radioisotopes (radionuclide / radio isotopes)  High frequency forms of electromagnetic energy  Is radiation given off by a radioactive substance; In food: cobalt 60 (Co60) and cesium 137 (Cs137)  Half life - Co60 = 5.3 years - Ce137 = 30 years HOW IT WORKS? Radiation is given off by a radioactive substance; cobalt 60 (Co60) and cesium 137 (Cs137) These substances give off high energy photons, called gamma rays, which can penetrate foods to a depth of several feet. These particular substances do not give off neutrons, which means they do not make anything around them radioactive. This technology has been used routinely for more than thirty years to sterilize medical, dental and household products, and it is also used for radiation treatment of cancer. Radioactive substances emit gamma rays all the time. When not in use, the radioactive "source" is stored down in a pool of water which absorbs the radiation harmlessly and completely. To irradiate food or some other product, the source is pulled up out of the water into a chamber with massive concrete walls that keep any rays from escaping. Medical products or foods to be irradiated are brought into the chamber, and are exposed to the rays for a defined period of time. After it is used, the source is returned to the water tank. ADVANTAGES  Up to 95% of its emitted energy is available for use.  Able to penetrate most solid and liquid.  Penetrates deeply (thicker food;>12 inch) = X ray.  Yields substantial uniformity of the dose in the food.  Decays to non radioactive nickel and barium.  Considered to pose low risk to the environment. DISADVANTAGES  Cobalt-60 pencils (stainless steel tubes) require frequent replenishment.  Cannot be turned off. ACCELERATED ELECTRON  Electron gun: convert energy into high energy electron.  Electron accelerator: accelerate the speed of electron to the speed of light.  Amount of energy produced can be adjusted.  Maximum energy: 10MeV (Mega electron Volts) HOW IT WORKS? Electron beams, or e-beams, are produced in a different way. The e-beam is a stream of high energy electrons, propelled out of an electron gun. This electron gun apparatus is a larger version of the device in the back of a TV tube that propels electrons into the TV screen at the front of the tube, making it light up. This electron beam generator can be simply switched on or off. No radioactivity is involved. Some shielding is necessary to protect workers from the electron beam, but not the massive concrete walls required to stop gamma rays. The electrons can penetrate food only to a depth of three centimeters, or a little over an inch, so the food to be treated must be no thicker than that to be treated all the way through. Two opposing beams can treat food that is twice as thick. ADVANTAGES  They can be turned on only as needed and off when not in use.  They do not require replenishment of the source as does cobalt-60  There is no radioactive waste DISADVANTAGES  Shallow depth of penetration (suitable for food less then 5 cm thick – meat patties).  High electric power consumption.  Complex and potentially high maintenance. X RAYS  Generated by colliding electron with metallic target (tungsten, gold or other metals)  Maximum energy: 5 MeV  Better penetrability compared to electron beam.  Disadvantage: the efficiency of conversion from electrons to X rays is generally less than 10%. HOW IT WORKS? The newest technology is X-ray irradiation. This is an outgrowth of e-beam technology, and is still being developed. The X-ray machine is a more powerful version of the machines used in many hospitals and dental offices to take X-ray pictures. To produce the X-rays, a beam of electrons is directed at a thin plate of gold or other metal, producing a stream of X-rays coming out the other side.  Likecobalt gamma rays, X-rays can pass through thick foods, and require heavy shielding for safety.  However,like e-beams, the machine can be switched on and off, and no radioactive substances are involved.  Four commercial X-ray irradiation units have been built in the world since 1996. PENETRATING CAPACITY  Gamma rays and X rays are very penetrating: useful for packed food.  Electron beam: lower penetrating power than gamma rays (penetrating capacity increase with energy); has very limited use for packed food.  UV light: lower penetrating capacity than gamma and electron beam: useful for surface treatment (surface mold in bakery product). MECHANISM OF ACTION OF IRRADIATION 1. Damage to bacterial DNA (break chromosome, prevent cell division so that bacteria cannot reproduce). 2. Destroy or change bacterial cellular membrane structure. 3. Breaks chemical bonds (affect biochemical reactions and physiological processes in plants). 4. Effect on water molecules: cause radiolysis (splitting of water molecules) and induce ionization. 5. Effect on enzymes (protein). DOSE  The quantity of radiation energy absorbed by food after being irradiated.  Unit currently used: Gray (Gy): amount of irradiation energy that 1 kg of food receives.  Radiation levels usually described in the form of kGy (1 kGy:1000)  Old unit: rad (radiation absorbed dose); 1 million rad = 10kGy  Dose permitted varies with the type of food and the objective of irradiation.  Dosimeter: instrument used to measure dose. RADIATION DOSE  Definition:is the quantity of radiation energy absorbed by the food as it passes through the radiation field during processing.  (1 Gy = 100 rads; 1 kGy = 1000 Gy)  Internationalhealth and safety authorities have endorsed the safety of irradiation for all foods up to a dose level of 10,000 Gy (10 kGy).  Interms of energy relationships; 1 Gy = one joule of energy absorbed per kilogram of food being irradiated → Maximum dose = 10 kGy (but > 10 kGy are still safe)  Irradiationis often referred to as a “cold pasteurization” process as it can accomplish the same objective as thermal pasteurization of liquid foods, for example milk, without any substantial increase in product temperature. THE IRRADIATION DOSE APPLIED TO A FOOD PRODUCT DEPENDS UPON:  The composition of the food  The degree of perishability  The potential to harbor harmful microorganisms  The type, amount and growth phase of microorganism  pH and moisture content of food  APPROXIMATE DOSES OF RADIATION NEEDED TO KILL VARIOUS ORGANISMS Organisms Dose (kGy) Higher animals 0.005 to 0.10 Insects 0.01 to 1 Non spore forming bacteria 0.5 to 10 Bacterial spores 10 to 50 Viruses 10 to 200 DOSE RATE (TREATMENT LEVEL) 1. Shelf life extension (Low Dose Application: up to 1 kGy)  Inhibit sprouting in potatoes and onions (=0.3 kGy): ‘trichina safe’  Control pork parasite: >0.5 kGy 2. Pathogen reduction (Medium Dose Application: 1kGy to 10kGy)  Control Salmonella, Shigella, Camphylobacter, Yersinia and E.coli in meat, poultry and fish (up to 2.5 kGy)  Eggs and eggs products: 2 to 5 kGy  Frozen shrimp: 3 kGy  Delay mold growth on strawberries and other fruits: 2 to 3 kGy  Eliminate most spoilage microorganism: 5 kGy 3. Disinfestation and sterilization: (High Dose Application: above 10 kGy)  Kill microorganisms and insects in spices  Commercially sterilize foods, destroying all microorganisms of public health concern  Radurization: 0.5 to 10 kGy  Decrease the number of microbiological  Radicidation: 3 to 10 kGy  Descrease the number of non spore-forming pathogenic bacteria  Radappertization: 25 to 60 kGy  Eliminate bacteria – toxicity. EFFECT OF IRRADIATION ON FOOD QUALITY  Radiation induce the formation of free radicals. As a results:  Induce radiolysis of water molecules.  Amino acid and protein: radiolytic change of amino acid especially sulfur containing amino acid (deamination and decarboxylation results in the formation of NH3, CO2, amines, aldehydes, acids) – off flavor, opening of peptide chain, coagulation, precipitation.  Carbohydrate: depolymerization cause reduce in gelling power of pectin (softening of fruits and vegetables)  Vitamin loss especially thiamine (B1), vitamin A, C, and E (fat soluble vitamin); vitamin E up to 25%, C up to 10% (1kGy).  Accelerate the development of off odor in fat due to auto oxidation (meat exposed to 20 – 60 kGy) oxidative rancidity and off color.  Milk and egg even at low dose develop off flavor  Increase shelf life of food; delay ripening and maturation of fruits and vegetables. THIAMIN RETENTION COMPARISON Meat % in irradiated sample % in canned sample Beef 21 44 Chicken 22 66 Pork 12 57 APPLICATION OF IRRADIATION IN FOOD INDUSTRY  Inhibiting sprouting (potato, onion, garlic, ginger)  Delay ripening/ageing process in plant  Increase juice yield (improvement of rehydration)  Insect disinfestation: insect sterilization (prevent proliferation)  To eliminate the residual risk of a contamination by a virulent E. coli treatment of hamburger patties  Absolute sterilization: food for space program and for immune deficient hospital patients.  Treatment of Salmonella sp in poultry  Tenderizing or ageing of meat  Prevention of surface mold growth of bakery products  Treatment of Trichinella worm in pork  Food Approved use Dose Spices and dry Decontaminate and 30 kGy vegetable seasoning control insect and microorganism Dehydrated enzyme Control insect and 10 kGy preparations microorganism All food Control insect 1 kGy Fresh food Delay maturation 1 kGy Poultry Control disease-causing 3 kGy microorganisms Red meat (lamb, Control spoilage and 4.5 kGy (fresh) beef) disease-causing 7 kGy (frozen) microorganisms ADVANTAGES OF FOOD IRRADIATION  Reduction of postharvest losses.  Reduction of chemical residues in foods (chemical sprout inhibitors such as maleic hydrazide)  Reduction of risks of foodborne illness from bacteria  Reduction of the risk of trichinosis from meat.  More appealing fresh characteristics.  Result in lesser nutritional loss compared to canning. DISADVANTAGES  Possibility of recontamination  Does not protect fruits, grain, spices from reinfestation RADURA LOGO  Theradura logo, as required by regulation to show a food has been treated with ionizing radiation.  Requiredfor retail, finished products or food destined for further processing but not required for minor ingredients.  Treated with irradiation  TYPES OF RADIANT ENERGY http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Types_of_radiation.svg/350px-Types_of_radiation.svg.png  Ionizing radiation  Ultraviolet light  Infrared  Microwave IONIZING RADIATION  Energyhigh enough to dislodge electrons from the atoms or molecules and convert them to electrically charged particles called ions THANK YOU