International Congress BIOLOGICAL PRODUCTS - Gruppo di ...

31
PROTEIN CONTENT AND MYCOTOXINS CONTAMINATION IN ORGANIC AND
CONVENTIONAL WHEAT
Pietri A., Bertuzzi T., Barbieri G. and Rossi F.
Istituto di Scienze degli Alimenti e della Nutrizione, Università Cattolica del Sacro Cuore, Facoltà di Agraria,
Piacenza.
Introduction
The importance of organic farming in terms of foods production and consumer confidence is increasing.
Numerous reports show as a growing number of people believe that organic foods are healthier than
conventional ones, particularly for the absence of pesticide residue in organic foods. However cereals from
organic production were sometimes found to have higher mycotoxins content than conventionally produced
foods, probably because if synthetic pesticide are not used there is a lower crop protection towards parasite
fungi. However due to some inconsistent results, a clear trend could not be identified. In respect of the proteins
content, a trend to lower values in organically produced cereals was observed.
Aim of this work was to verify the content of ocratoxin A (OTA), trichothecenes, ergosterol and crude protein in
organic and conventional wheat produced in the area of Piacenza (North Italy).
Materials and methods
Thirty-five samples of wheat (20 organic and 15 conventional) were collected during storage and analyzed for
theirs mycotoxins contamination and crude protein content. OTA was extracted with a mixture of CH3OH:3%
NaHCO3 water solution(50:50) and purified using an immunoaffinity column (Ochraprep). OTA was determined
by reversed-phase HPLC with fluorescence detection (λecc=333 nm e λem=470 nm); a Select-B RP-8 column,
125x4mm (Merck), was employed at room temperature with a mobile phase of acetonitrile:acidified water (2%
CH3COOH)(41:59) at 1.2 ml/min. The detection limit was 0.010 µg/kg.
Deoxynivalenol (DON), 3 and 15-acetyl-deoxynivalenol (3-AcDON and 15-AcDON), nivalenol (NIV), HT-2
and T-2 were determined. These trichothecenes were extracted with acetonitrile:water (84:16) for 90 minutes and
an aliquot (6 ml) of the filtered extract was purified by Mycosep 227 column (Romer Labs). The final extract
was derivatised with N-trimethylsilylimidazole and analysed by GC-MS using an ion trap detector.
Trichothecenes were separated with a RTX-5 capillary column, 30mx0.25mm i.d. (Restek), and quantified by the
selected ion monitoring technique; the detection limit was 2 µg/kg.
Ergosterol analysis was performed according to AFNOR (Norme Francaise, 1991). After extraction with KOH
alcoholic solution, an aliquot (20 ml) of the filtered extract was purified by Extrelut column (Merck). Ergosterol
was determined by HPLC with UV detection (λ=280 nm); a Superspher Si 60 125x4 mm column (Merck) was
employed with a mobile phase of n-hexane:isoamyl alcohol=98:2 at 1.0 ml/min. Detection limit was 0.4 mg/kg.
The N content was determined using the Kjeldahl technique. Statistical analysis of data was performed with the
statistical package SAS, using the PROC UNIVARIATE to verify the normality of data distribution and PROC
GLM and PROC NPAR1WAY for analysis of variance.
Results
The analyzed samples had a low contamination of mycotoxins, OTA levels were always lower than legal
threshold of 3 µg/kg and no significant differences were observed between the two types of wheat. The 45% of
organic samples were contaminated by OTA against a 40% in conventional wheat, however the most
contaminated sample (0.53 µg/kg) was found in conventional cereals.
The only detected trichothecene was DON, confirming the hypothesis that it is the most widespread in cereals.
Only 25% of organic wheat showed a DON contamination (max value = 17.1 µg/kg) while all conventional
samples were contaminated (max value =219.1 µg/kg). The DON content of organically produced wheat was
significant lower than conventionally grown one (2.85 µg/kg vs 99.67 µg/kg; P