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6Scientific Notes of Taurida V.Vernadsky National University Series «Biology, chemistry» Vol 25 (64). 2012. No 2. P. 233-236.
UDC 544.54
RADIOLYTIC DESTRUCTION OF OCHRATOXIN IN DAMP BARLEY GRAINS
Mamedov Kh. F.
Institute of the RadiationProblems, National Academy of Sciences, Department of theComplex Researches of the Azerbaijan Republic, Baku, Azerbaijan E-mail: xagani06@mail.ru
The destruction of ochratoxin in damp grains of barley under the influence of ionizing radiation of 60Co has been studied. The possibility of "radiolytic detoxification" of barley has been determined at the various degrees of grains' humidity and at the different values of absorbed dose of ionizing radiation. It is defined that, the doses 10-25 kGy is quite sufficient, also for full sterilization of grains. Keywords: grains, barley, mycotoxin, destruction, ionizing radiation.
INTRODUCTION
The ionizing radiation of 60Co sources have been successfully used for enlarging the shelf life of fruit, vegetables and grains without losses, for improving their properties, for disinfection, pasteurization, sterilization, preservation and conservation of the foodstaff
[1-3].
The carcinogenic properties of natural toxins are not less than such properties of anthropogenic xenobiotics. Pollution of foods by bacterial toxins leads to strong food poisoning [4, 5]. About 300 species of derivative metabolites, i.e. mycotoxins synthesized by more than 350 kinds of microscopic fungus are known. Mycotoxins can penetrate into the deeper layers of food. Low concentration of natural toxins can become the poisoning reason.
Synthesized by fungus Aspergillus and Penicillium the Ochratoxin is characterized by teratogenic properties and doesn't decay at 2500C. Contamination of foods and forages by ochratoxin can be reason of human and animal poisoning.
The aim of this research work is to explore the destruction of ochratoxin in water solution and damp grains of barley under the influence of ionizing radiation of 60Co.
MATERIALS AND METHODS
Microorganisms were investigated by using special nutrient mediums of Hi-Media (India) and Condalab (Spain). The enzyme immunoassay testings, LC-MS and LC-MS/MS methods have been used for estimations of mycotoxins [6, 7].
Absorbed in substances ionizing dose rate of radiation from 60Co sources were 0.33 Gy/s. The studied substances have been irradiated by the doses up to 25 kGy.
RESULTS AND DISCUSSION
The high concentration of ochratoxin (0.25 mg/kg) has been revealed in damp barley grains. Damp grains of barley (5 and 20% humidity) and water solution of ochratoxin have been irradiated by ionizing radiation.
Numerous information about the sterilization, disinfection, disinsection of the products are known [1-3].
The possibility of radiolytic decomposition of various natural toxins synthesized by Aspergillus, i.e. the dependence of ochratoxin's quantity from the absorbed dose has been studied. Decrease of ochratoxin's concentration in water solution and in damp barley grains under the influence of ionizing radiation of 60Co are presented in the Table 1.
Table 1.
Radiolytic destruction of ochratoxin in water solution and damp barley grains
The absorbed dose of 60Co 0 1 2.5 10 25
ionizing radiation, kGy
Ochratoxin in barley (5%
humidity), mg/kg 0.25 0.18 0.12 0.08 0.05
Ochratoxin in barley (20% humidity), mg/kg 0.25 0.15 0.08 0.03 0
Ochratoxin in water
solution, mg/kg 0.25 0.11 0.05 0.01 0
The reduction of Aspergillus fungi under the influence of ionizing radiation of 60Co are shown in the Table 2.
Table 2.
The reduction of Aspergillus fungi under the influence of 60Co radiation
The absorbed dose of ionizing radiation, kGy 0 1 2.5 25
The Aspergillus count in 1 g of barley grains 600 1200 740 0
By comparison of the Table 1 and Table 2, it seems that the rate of ochratoxin's destruction is lower than the rate of microorganism death.
The calculation of radiation-chemical yield of ochratoxin's destruction in water solution and in barley grains are presented below:
- 1 kGy of absorbed dose of ionizing radiationis is equivalent 6.241x1021 eV/kg;
- the concentration of ochratoxin in a water solution decreased from 250 ^g/kg to 110 ^g/kg, i.e. on 140 ^g/kg, during absorption of 1 kGy dose, that is equal to decomposition of 210x1015 molecules in 1 liter or 1 kg of water (the relative molecular weight of ochratoxin is 400);
RADIOLYTIC DESTRUCTION OF OCHRATOXIN.
- decrease of ochratoxin's concentration equal to 70 and 100 ^g/kg during absorption of 1 kGy dose obtained at 5% and 20% humidity of grains, that is equal accordingly to decomposition of 105x1015 and 150x1015 molecules of ochratoxin in 1 kg of barley grains;
- the calculation of ochratoxin's destruction is possible from the above-stated results at absorption by systems 100 eV energy of ionizing radiation. The values of radiation-chemical yields are equal to 210x1015 molecules/kg x 100 eV/6.241x1021 eV/kg = 0.34x10-2 molec./100 eV for water solution, 0.17x10-2 and 0.24x10-2 molec./100 eV for damp grains (accordingly at 5% and 20% degree of humidity).
These values show to high stability of ochratoxin's molecules. The value of radiation-chemical yield of ochratoxin's destruction in a water solution is 2 and 1.4 times more than in barley grains accordingly at 5% and 20% humidity. This fact specified the formation of e-aq at the radiolyse of water solutions and participation of these hydrated electrons in the further destruction of ochratoxin. Radiolysis of water is described by a following equation:
H2O JU e-aq, H, OH, O, H2, H2O2, H+aq, OH-aq.
All free-radical products of water solutions (e-aq, H, OH, O, H+aq, OH-aq) can take part at the destruction of mycotoxin. Insignificantly low quantities of uncarcinogenic compounds (methylcyclopenthan, benzoic aldehydes, small fat acids and spirits) have been elicited at the radiolytic sterilization of barley grains.
Existing methods of detoxification (mechanical, chemical and physical/thermical/) are characterized by many deficiencies [8, 9, 10]. The significant destruction of oxratoxin is observed in studied substances under the influence of ionizing radiation of Co source.
The destructions rate of oxratoxin in water solution and in damp barley grains are too low and the values of radiation-chemical yields of oxratoxin's destructions vary in the range ~ 0.17x10-2 - 0.34x10-2/100 eV. But, absorbed dose of ionizing radiation equal to 10-25 kGy, leads to the decrease of any concentration of oxratoxin to the values lower than permissed concentration of ochratoxin in cereals (0.01 mg/kg). Radiolytic destruction, i.e. "radiolytic detoxification" by absorbed doses equal to 10-25 kGy doesn't hold to any negative changes in organoleptic and chemical properties of barley grains.
CONCLUSION
Absorbed dose of ionizing radiation equal to 10-25 kGy leads to the oxratoxin's destruction in water solution and in polluted barley grains to the values lower than permissed concentration of oxratoxin in cereals.
The method of "radiation detoxification" is more effective than other traditional methods of detoxification. Absorbed dose equal to 10-25 kGy used for "radiation detoxification" are enough also for the full sterilization
References
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10. Duarte S.C. A review on ochratoxin A occurrence and effects of processing of cereal and cereal derived food products / S.C. Duarte, A. Pena, C.M. Lino // Food Microbiol., 2010. - № 27. - P. 187.
Мамедов Х.Ф. Радиолитическое разложение охратоксина во влажных зернах ячменя / Х.Ф. Мамедов // Ученые записки Таврического национального университета им. В.И. Вернадского. Серия «Биология, химия». - 2012. - Т. 25 (64), № 2. - С. 233-236
Изучено разложения охратоксина во влажных зернах ячменя при облучении их ионизирующим излучением 60Со. Установлены возможности «радиолитической детоксикации» ячменя при различных степенях влажности зерен и при разных значениях поглощенной дозы ионизирующего излучения. Определены, что поглощенные дозы, равные 10-25 кГр вполне достаточны также для обеспечения полной стерилизации зерен.
Ключевые слова: зерна, ячмень, микотоксин, разложение, ионизирующее излучение.
Мамедов Х.Ф. Радшл^ичного розкладання охратоксину у вологих зернах ячменю / Х.Ф. Мамедов // Вчеш записки Тавршського национального утверситету iм.В.I. Вернадського. Серiя ,Долопя, ымя" - 2012. - Т. 25 (64), № 2. - С. 233-236.
Вивчено розкладання охратоксину у вологих зернах ячменю при опромшенш !х юшзуючим випромшюванням 60Со. Встановлено можливост «радюлтчного детоксикацп» ячменю при рiзних ступенях вологост зерен i при рiзних значеннях поглинено! дози юшзуючого випромшювання. Визначено, що поглинут дози, рiвнi 10-25 кГр цшком достатш також для забезпечення повно! стерилiзацii' зерен.
Ключовi слова: зерна, ячмшь, мкотоксин, розкладання, юшзуюче випромшювання.
Поступила в редакцию 14.05.2012 г.
