IX. PENGAWETAN MAKANAN MENGGUNAKAN RADIASI

IX. PENGAWETAN MAKANAN MENGGUNAKAN RADIASI

Radiasi dapat didefinisikan sebagai pancaran dan perbanyakan energi melalui ruang atau melalui medium bahan. Tipe radiasi yang terutama digunakan dalam

pengawetan

bahan

pangan

adalah

elektromagnetik.

Spektrum

elektromagnetik dapat dilihat pada Gambar 7.1. Berbagai radiasi dibedakan berdasarkan panjang gelombang. Semakin pendek panjang gelombang, semakin merusak mikroorganisme. −

Radiasi ionisasi (Ionizing radiations) −

adalah radiasi yang mempunyai panjang gelombang 2000 A atau kurang.

−

−

mempunyai cukup energi untuk mengionisasikan molekul.

−

membunuh m.o. tanpa kenaikan suhu yang nyata.

Unit Radiasi: −

Roentgen : unit untuk menyebutkan dosis sinar x atau sinar gamma

−

Curie

:

unit

untuk

menyebutkan

kuantitas

dari

substansi

radioaktif. −

Rad

: unit radiasi ekuivalen dengan absorbs! 100 erg/g bahan.

Yang penting bagi pengolahan bahan pangan antara lain : −

Gelombang mikro (microwave)

−

Sinar ultraviolet

−

Sinar X

−

Sinar Gamma

Universitas Gadjah Mada

Gambar 9.1. Bagan spektrum

Karakteristik Radiasi −

Sinar Ultraviolet (UV) −

bersifat bakterisidal

−

panjang gelombang efektif 2.600 A nonionizing

−

diserap oleh protein dan asam nukleat

−

terjadi perubahan fotokimia yang menyebabkan kematian sel (mutasi letal)

− −

kemampuan penetrasi rendah

Sinar beta −

merupakan elektron yang diemisikan dari substansi radioaktif.

−

serupa dengan sinar katoda (diemisikan oleh katoda dalam tabung hampa)

− −

kemampuan penetrasi rendah

Sinar gamma −

merupakan radiasi elektromagnetik yang dipancarkan dari inti yang tereksitasi (Misal: 60Co dan 137Cs)

−

murah

−

kemampuan penetrasinya sangat baik


−

Sinar X −

diperoleh

dari

bombardment

logam

berat

dengan

elektron

berkecepatan

−

−

tinggi di dalam tabung hampa.

−

Sifatnya hampir sama dengan sinar gamma

Gelombang mikro (microwave) −

Terletak antara sinar inframerah dan gelombang radio.

−

Bahan makanan bermuatan elektrik netral ditempatkan

pada

medan elektromagnetik, molekul asimetris yang bermuatan akan berosilasi. −

Gesekan intermolekuler akan menyebabkan panas.

PRINSIP DESTRUKSI MIKROORGANISME −

jenis dan spesies

−

jumlah mikroorganisme

−

komposisi bahan makanan

−

ada tidaknya oksigen

−

kondisi bahan makanan umur mikroorganisme

−

dosis irradiasi untuk berbagai aplikasi dapat dilihat pada Gambar 7.2.

PROSES RADIASI 1. seleksi/sortasi bahan 2. pembersihan bahan 3. pengemasan (proteksi terhadap kontaminasi pasca radiasi) 4. blanching atau perlakuan pemanasan

TERMINOLOGI −

Raddappertization : equivalent dengan sterilisasi komersial dengan radiasi.

−

Radicidation

: equivalent dengan pasteurisasi (reduksi jumlah sel

hidup patogen yang tidak menghasilkan spora) −

Radurization : equivalent dengan pasteurisasi (meningkatkan keeping


quality dengan mengurangi mikrobia pembusuk tertentu)

Gambar 9.3. Dosis iradiasi untuk berbagai proses

APLIKASI RADIASI −

Radiasi Gamma ( Lihat Gambar 9.3.)

−

Electron beams


Gambar 9.3. Tiga teknik dasar proses iradiasi (interaksi elektron, sinar x, dan sinar gamma dalam medium)

PENGARUH IRADIASI TERHADAP BAHAN MAKANAN −

Air mengalami radiolisis 3H2O

------- Æ H + OH + H2O2 + H2

−

Terbentuk radikal bebas

−

Protein dan komponen nitrogen sensitif terhadap iradiasi

−

Iradiasi lemak menghasilkan karbonil dan peroksida menyebabkan ketengikan

−

Vitamin : mengalami kerusakan

−

Metoda untuk memperkecil efek samping bahan makanan yang diiradiasi ionisasi (Lihat label 7.1.)


Tabel 7.1. Metoda untuk mereduksi efek samping makanan yang diradiasi ionisasi

Metoda Mereduksi suhu Mereduksi tekanan oksigen Penambahan scavenger Reduksi dosis

Alasan Imobilisasi radikal bebas Reduksi jumlah radikal bebas Kompetisi dengan radikal bebas Mengurangi radikal bebas

STABILITAS PENYIMPANAN −

Mampu menghasilkan bahan makanan yang shelft-stable

−

Radappertization tidak mampu merusak enzim -> perubahan setelah iradiasi.

−

Radurization : dapat mengalami pembusukan dari mikroorganisme yang tahan.

ONIZING RADIATIONS Radiation with enough energy to cause ejection of electrons from atoms or molecules, thus creating ions.

IRRADIATE Expose to ionizing radiation.

IONIZING RADIATIONS Energies up to 10 mev Wave lengths of < 2000 A° High velocity electrons Cathode rays Beta rays Electromagnetic radiations x-rays y-rays


UNIT OF RADIATION Rad

= absorption of 100 ergs of energy per gram

Krad

= 1.000 rads

Mrad

= 1.000.000 rads

Gray (Gy)

= 100 rads = 1 joule/kg

kGy

= 100.000 rads = 1.000 Gy

RADIATION EFFECTS ON LIFE Direct effect or Target Theory DNA damage Indirect effects Free radical reactions radiolysis 3H2O

H + OH + H2O2 + H2

Free radicals Peroxides

RADIOLYTIC PRODUCTS Product quality Nutrition Safety

TO MINIMIZE Reduce oxygen tension Reduce temperature Add free radical scavengers Distillation Reduce dose

DOSES OF FOOD IRRADIATION Destruction of microorganisms Insect deinfestation Parasite inactivation D


elay fruit ripening Sprout inhibition

USES OF FOOD IRRADIATION •

Greater safety of the food supply is the foremost benefit of irradiating certain foods

•

The destruction of harmful! bacteria and resulting decreased microbial contamination of food items is arbenefit most often stressed by proponents. Its advantage is seen by some consumers.

•

Decreased use of pesticides and fumigants is seen as a very positive advantage to most consumers surveyed.

•

High quality fresh produce with longer shelf life is another advantage. Fruits and vegetables can remain in the field longer for ripening and have a better taste.

•

Longer shelf life will delay sprouting and decay. This is generally not considered important by consumers at this time, but would be important to the grocer now, and perhaps to consumers when they are more familiar with the advantages.

•

Wide product availability would result in more variety of foods available seasonally.

•

Lower cost may become a benefit to consumers as some products become more readily available.

•

Reduction of world hunger by making more food available through less waste from spoilage is also a potential benefit.

MICROBIAL DESTRUCTION

RADAPPERTIZATION : "Commercial sterility" / shelf - stable > 1 Mrad (> 10 kGy): 30-45 kGy 1012 C. botulinum spores : 2.2 - 4.5 Mrad Spices 30 kGy


RADURIZATION : Radiation pasteurization Inactive spoilage organisms Extend shelf-life /improve safety < 1 Mrad (< 10 kGy): 0.75-2.5 kGy Refrigeration

RADICIDATION : Radiation pasteurization to inactive pathogens Cells, not spores or viruses < 1 Mrad (< 10 kGy): 0.75-2.5 kGy Refrigeration

IRRADIATION OF POULTRY MEAT September 21, 1992 Fresh, refrigerated or frozen raw poultry meat 1.5-3.0 kGy To destroy pathogens : Listeria monocytogenes Salmonella Campylobacter FDA approval: May 1990 Technical process vs food additive

THE ISSUES OF CONSUMER CONCERN

Concerns about irradiated food fall into three categories. Food safety issues : Some feel that the safety has not been proven because feeding studies are inconclusive.

There is concern that potentially hazardous free radicals are formed in the food by the process.


Other concerns include the fear that hazardous microorganisms may have selective advantage and signs of spoilage will not be seen.

Nutrient losses will lead to lower quality food.

People may unknowingly be exposed to irradiated foods because of poor labeling.

Irradiation will be used to cover-up a "dirty" food supply, when proper processing and inspection would suffice.

Environmental Issues and the Nuclear Connection : Most of the environmental concerns are associated with concern about radioactivity in general: −

Long-term cancer-causing potential,

−

Potential harm to employees,

−

Potential danger from living near an irradiation facility,

−

Danger form accidents of trucks tranporting materials, and

−

Disposal or storage of spent sources of energy (Cobalt 60 or Cesium-137) is an issue of concern, although a related concern is that the Department of Energy is using food irradiation way to dispose of Cesium-137 waste from other nuclear processes.

Economic Issues : There is concern that irradiation will increase the cost of food.]

SAFETY OF IRRADIATED FOODS

a. unsafe products b. free radicals c. long-term exposure = cancer


Approval by FDA on May 20, 1990 Addressed all concerns Refuted all arguments "No toxic effects below 68 kGy"

Radiolytic products: In many foods Low concentrations

Who JECFI (1980): "Food irradiated to doses not exceeding 10 kGy is wholesome and safe for human consumtion."

WHO (1992) "Irradiation presents

carried

out

under

good

manufacturing

practises

no toxicological hazard and introduces no special

microbiological problems."

USDA Rule supported by: Physicians Other industries

MICROBIAL ALTERATIONS a. Elimination of spoilage competition b. Selection for radiation-resistant microbes c. Development of mutants

Can food become toxic with C. botulinum without visible spoilage?

FDA concluded :

"In chicken irradiated to 3 kGy, natural flora survivors grow faster than C. botulinum."

Vacuum packaging not permitted.


Radiation resistant mutants: Natural mutants Mutants from other food processes Mutations detrimental to microbes

Irradiated food should not be re-irradiated.

WHO: Recommended that re-irradiation be permitted, where needed, at least to a cumulative dose of 10 kGy.

CHEMICAL CHANGES IN IRRADIATED FOODS

a. Reduced eating quality b. Reduced nutritional quality

High doses of irradiation: "wet dog", "wet grain"

45 kGy (sterilized): Nutritional quality similar to heated foods. Cold process.

PDA: "Irradiation at doses used does not have an adverse effect on the level or bioavailability of nutrients in chicken meat"

"No adverse effects on diet"


IS IRRADIATION A SUBTITUTE FOR GMP

NOT!! Follow PPIR Spoiled product cannot be saved Enzymes

RADIACTIVITY AND ENVIRONMENTAL CONCERNS a. Harm to employees b. Danger to people living near facilities c. Truck accidents d. Storage and disposal e. Outlet for waste of nuclear industry f.

Not a new industry

o

Regulated : DOE and NRC

o

Lead-shielded steel containers

o

No release of activity in environment

o

Low levels of radiant energy

o

Double-walled capsules

o

Deep deionized water pool

o

Radiation sensors and alarms

o

Only cobalt-60 used

o

Facilities approved, licenced, inspected, and records kept

o

Workers trained

LABELLING

Green international logo "Treated with radiation" or "Treated by radiation"

"Keep refrigerated" or "Keep frozen"


"Radiation" "Electrically processed" "Preserved by fast electron" "Electronic preservation"

"Salmonella free?"

WILL FOOD GLOW IN THE DARK

NOT!! Food not in contact with radioactive material No induced radioactivity. < 10 mev

WHY USE IRRADIATION? WHY NOT SANITATION AND COOKING? Poultry irradiation only voluntary Sanitation does not eliminate pathogens Cooking effective, but cross-contamination

COST OF IRRADIATED PRODUCTS Estimated cost: 0.86-1.30 cent/lb Estimated health benefits : $ 35-50 million Profitable enough to be used?





IX. PENGAWETAN MAKANAN MENGGUNAKAN RADIASI

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