Kuru incirde fumonisin varlığının belirlenmesi

Özet

Besleyici ve sağlıklı bir gıda olan kuru incir dünyada yaygın olarak üretilen meyvelerdendir. Fumonisinler, mısırda yaygın olarak bulunmakta olup Fusarium verticilloides ve F. proliferatum tarafından üretilmektedir. Bu çalışmada Ege Bölgesi'nden 2003 ve 2004 yıllarında 7 farklı yöreden kurutma aşamasından temin edilen kuru incir örneklerinde fumonisin varlığı ELISA yöntemi kullanılarak araştırılmıştır. ELISA yöntemiyle toplam fumonisin tayini ekstraksiyon, katı faz ekstraksiyon kolonuyla temizleme işlemlerinden sonra gerçekleştirilmiştir. İncir örneklerinin %81.8 'inde 0.1 ppm 'in üstünde fumonisin varlığı belirlenmiştir. Çalışmanın ikinci yılında örneklerde birinci yıla göre daha yüksek oranda fumonisin kontaminasyonu belirlenmiştir. Buna karşılık birinci yılda daha yüksek fumonisin düzeyleri belirlenmiştir. Her iki yılda da Örneklerde fumonisin kontaminasyonu en fazla 1.0-5.0 ppm arasındadır. Kurutma aşamasından temin edilen kuru incirlerde ELISA yöntemiyle belirlenen toplam fumonisin değerleri HPLC yöntemi ile karşılaştırılmıştır. ELISA yöntemi ile HPLC yöntemine göre kuru incirde çok daha yüksek fumonisin değerleri elde edilmiştir. Örneklerin tamamında iki yöntemle elde edilen bulgular karşılaştırıldığında regresyon katsayısı 0.869 olarak hesaplanmıştır. HPLC yöntemiyle 1 ppm değerinin altındaki FBj değerleri dikkate alındığında iki yöntem arasında ilişki belirlenmemiştir. 1 ppm 'in üzerindeki değerler için iki yöntem arasında korelasyon belirlenmesine rağmen ELISA yöntemiyle elde edilen fumonisin miktarları HPLC yöntemine göre çok yüksektir. ELISA yöntemiyle 115 örneğin 11 adedinde yanlış pozitif sonuç belirlenmiştir. Elde edilen bulgulara göre kuru incirde fumonisin tayini için ELISA tarama amaçlı olarak kullanılabilecek bir yöntem olup sonuçların HPLC gibi başka bir yöntemle doğrulanması gerektiği düşünülmektedir.

Abstract

Dried fig, very nutritional and a healthy food, is one of the most widely produced fruits in the world. Dried figs can be consumed directly, or as fig paste in production of different desserts and candies. It is an important agricultural product following raisin and dried apricot among Turkish dried fruit exports. Turkey is ranked first in dried fig exporting countries with approximately 52600 tons of dried figs in 2005, equivalent to 52% of world's dried fig exports. Dried figs are produced mainly in the Aegean Region in the western part of Turkey. Environmental conditions in the Aegean Region during ripening, harvesting and drying of figs seem favorable for my-cotoxin production in infected fruits. Harvesting and sun-drying processes and water activity value of fig fruits during drying are also effective on mycotoxin formation.Fumonisins are produced by Fusarium verticilloides and Fusarium proliferatum, fungi that commonly contaminate maize. Fumonisins induce several diseases in animals such as Equine leukonencephalo-malacia in horses, Porcine pulmonary oedema. A relationship between consumption of fumonisin containing maize and incidence of esophageal cancer by humans in certain areas of the world has been determined. With regard to the animal studies and epidemiological studies on humans, fumonisins have been classified as a possible human carcinogen (Group 2B) by IARC. Thin-layer chromatography (TLC) and liquid chromatographic (LC), mass spectroscopic (MS), gas chromatographic and immunochemical methods have been used for fumonisin analysis in foods.In this study, the total fumonisin incidence and levels were determined in the Turkish dried figs, collected from the drying stage in seven different districts located in the Aegean Region in 2003 and 2004. Occurrence of total fumonisin (FB[, FB2, FB3) in dried figs was investigated by Enzyme Linked Immunoassay (ELISA) after extraction with methanol: water and clean up with solid phase extraction cartridge.The results of the two years indicate that fumonisin presence is a potential risk in dried figs. Fumonisins were detected in 94 samples of the 115 naturally dried figs collected from orchards before any treatment. The total fumonisins in dried figs contamina- tion were determined as 78.9% and 86.4 % in 2003 and 2004 samples, respectively. Although the lower contamination incidences were observed in 2003 than in 2004, higher total fumonisin content was determined in the first year of the study. The highest incidences of fumonisin positive samples were obtained within the range 1.0-5.0 ppm for each year. 19.7% and 11.4% of the dried fig samples had fumonisin level exceeding 20 ppm in 2003 and 2004, respectively.ELISA and High Performance Liquid Chromatography (HPLC) methods for the determination of fumonisins in dried figs were compared. Only occurrence of fumonisin B] in dried figs was determined by HPLC. Among the fumonisin derivatives, FBi is the most common one and constitutes about 70-80% of the total fumonisin content of F. verticilloides cultures and naturally contaminated foods. Fumonisin B2 accounts for 15-25% of the total fumonisin while fumonisin Bi accounts for %> 3-8.Correlation between ELISA and HPLC methods was observed for all samples. However, no correlation between methods was recorded for samples below 1 ppm Fumonisin Bi level (obtained by HPLC). Regression coefficient was calculated as 0.820 for samples that contains above 1 ppm fumonisin B/. Although there was a correlation between methods for samples above 1 jug/gr, fumonisin levels obtained by ELISA were much higher than HPLC. False positive results were obtained by ELISA in 11 of 115 dried fig samples. Overestimation of the fumonisin content and false positive results in ELISA assays have been also reported previously. Although solid phase extraction cartridge was used for cleaning in the ELISA assay, higher fumonisin levels than HPLC were observed in dried fig samples because of the solvent effect of methanol. Hence, it was reported that solvent and matrix effect could be decreased by diluting the extract with phosphate buffer or distilled water.It is considered that ELISA assay can be used as a screening method to determine the occurence of fumonisin in dried figs after diluting the extracts. The mycotoxin concentrations in positive samples should be confirmed by a chromatographic methods such as HPLC to eliminate the false positive and false negative results.