34305

Relationship between rice tocopherols content and water absorption in Near InfraRed region

Favoritar este trabalho

Italy accounts for 50% of the European production of rice with about 1,551,272 tons of paddy rice produced on a cultivated area of 235 052 ha (Annual Report , 2013, www.enterisi.it)
The domestic consumption of rice, which consumes about a third of the national production, is oriented towards historical rice varieties used for traditional risotto (such as Carnaroli, Arborio, Baldo and Roma). Italian rice, however, shows a shortage of assessments that enable its enhancement, both in terms of quality and content of health components .
The purpose of this study was to evaluate the content of tocopherols, nutraceutical components, in different rice varieties currently grown and to monitor its content with rapid technique to support genetic improvement actions. As second objective, the influence of tocopherols content on water absorption spectra was investigated using the Aquaphotomics approach to verify its suitability in highlighting the presence of micro-lipo compounds in food matrices.
About 60 flour samples obtained by grinding were analyzed, in duplicate, in reflectance mode in the range of 4000-10000 cm- 1 by a NIRFlex N500 spectrometer (Büchi Italia srl, Italy) with a resolution of 4 cm- 1, each spectrum was the result of 64 scans. The α-, γ- and δ-tocopherols content (Total Tocopherols Content=TTC) of the same samples was measured by HLPC. The calibration models were calculated, after converting the spectra in absorbance, with PLS regression using PLSToolbox (Eigenvector, WA, USA).
The model performances obtained using 4 LV and autoscaling the spectra, were: RMSEC=0.836, RMSECV=0.888 and RMSEP=0.699 and an RPD of 3.47.
The results show good prospects in the use of NIR technology in supporting the genetic improvement programs of Italian rice.
On the basis of these encouraging results, spectra were pre-treated applying MSC and 2nd derivative, and grouped in 4 classes related to the TTC (very low: < 0.5 ppm; low: >0.5 <4.0 ppm; high: >4.0 <6.0 ppm; very high: >6.0 <10 ppm). The corresponding Aquagrams were then built.
Interesting information were found reading the Aquagrams, that showed a quite regular decreasing of water absorption bands in the NIR region from 1300 to 1550 nm in correspondence of an increasing in TTC. TTC concentration higher than 4.0 ppm didn’t seem to have further influence on water NIR response. The explanation of the obtained results was found considering the different chemical nature of water and tocopherols and their low hydrofilicity.
The information provided can support the use of Aquaphotomics as suitable tool in explaining and monitoring the evolution of bio-systems through the study of water absorption pattern.