WHEAT FLOUR HUMIDITY VARIATION WITH UV-VIS RADIATION DOSE REVEALED BY SPECTRAL AND CHEMOMETRIC STUDIES

The cells’ exposure to UV radiation induces mutations of the cellular components by its action on DNA, protein synthesis and enzymatic activities. Different varieties of wheat flour were treated with UV-B, UV-A, Vis radiation and compared with untreated samples. The IR spectra for these components were recorded with a Bruker FTIR spectrophotometer using an ATR method, at 4 cm-1 resolution. The paper proposes a comparative study of unmaturing flour behavior under UV-Vis and natural radiations in order to observe the physico-chemical changing by FTIR spectroscopy. At small doses of irradiation (up to 2 h) the humidity of the samples decreases and then it significantly increases, most pronounced in Gruia’s case where the humidity is reaching 74.4% of the initial value. Middle infrared spectral studies reveal an inverse weak linear correlation between Amide I region (1650 cm-1) (R-squared value: -0.3168) and an inverse medium linear correlation assigned to area alcohol O-H band at 3290 cm-1 (R-squared value: -0.6064) with the irradiation dose variables. Strong direct linear correlations confirmed by R-squared value: 0.7835 are found between alcohol O-H band at 3290 cm-1 and humidity percentage parameter

Successful fodder yeast production from agro-industrial by products through a statistical optimization approach

International audienceThe present work focused on the fodder yeast production, an attractive source of proteins for the livestock nutrition through the efficient growth of microorganisms on inexpensive waste substrates. Two agricultural by-products, sugar beet pulp and barley husks, rich in simple carbohydrates (88 g/L and 31.77 g/L for sugar beet hydrolysate and barley husks hydrolysate, respectively) were mixed after acid hydrolysis and used as a carbon and energy source for the "fodder yeast" Candida utilis production. Various nutritional requirements affecting the yeast growth were considered and investigated through an experimental design approach. The Response Surface Methodology was applied in order to optimize the medium composition aiming to increase on the one hand the yield on biomass rich in protein content and the substrate bioconversion on the other hand. Statistical analysis of the mathematical models developed for the studied response functions revealed a good correlation between the experimental data and the predicted values. In a medium containing 32-34 g/L reducing sugar, 1.022-1.079 g/L nitrogen and 0.406-0.427 g/L phosphorous, 6.47-6.62 g/L biomass were obtained. Under these conditions the final product protein content was of 50.40-51.55% (w/w) for a substrate consumption yield (expressed as monosaccharides content) of 92.94-95.4% (w/w)