Novel thin-layer chromatography-digital image-based analytical methods were developed for the quantitation of ergosterol and chitin content in six food matrices (rice, wheat, maize, sorghum, groundnut, and sunflower), artificially infested with Aspergillus flavus (MTCC 6513)/Fusarium verticillioides (MRC 826). For ergosterol, single-step method, based on liquid/liquid extraction, was followed by thin-layer chromatography (TLC). Chitin was solubilized using lithium chloride (5%) in dimethyl acetamide and converted to chitosan using 5 N NaOH and subsequently complexed with calcofluor white dye. The absorption and emission maxima of chitosan-calcofluor complex were recorded at λ 350/230 and 430 nm, respectively. The sensitivity based on the limit of detection (LOD) was found to be 100 ng both for ergosterol and chitin analysis. Based on ergosterol and chitin analysis, groundnut and maize were found to be suitable substrates for A. flavus (p < 0.013 and p < 0.01), while sorghum followed by groundnut and sunflower were found to be ideal for F. verticillioides (p < 0.01 and p < 0.0001) and rice was established as poor substrate as there was no growth on it up to 12 days of incubation. A strong correlation was found between ergosterol and chitin contents with regression (r2) values of 0.974 and 0.997 in food grains inoculated with A. flavus and F. verticillioides, respectively, during the period of infection. The authenticity of the two methods developed was further confirmed by applying them to commercial food grains and flours. Thus, ergosterol in combination with chitin analysis could be successfully used as an index of fungal contamination employing TLC-digital-based analytical methods.
Food grains Ergosterol Chitin Calcofluor white Fungal contamination TLC
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The authors are thankful to CSIR, New Delhi, for funding the research project, vide sanction No. [38 (1155)/07/EMR-II] and for infrastructural facility provided under DST - PURSE programme at Osmania University.
Compliance with Ethical Standards
Conflict of Interest
Tanuja Kosuri declares that she has no conflict of interest. Sujatha Nayak declares that she has no conflict of interest. Mir Zahoor Gul declares that he has no conflict of interest. Karuna Rupula declares that she has no conflict of interest. Sashidhar Rao Beedu declares that he has no conflict of interest.
This article does not contain any studies with human participants or animals performed by any of the authors.
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