Modelling of Batch Lactic Acid Fermentation in the Presence of Anionic Clay

U radu je provedena šaržna fermentacija mlijeka inokuliranog mliječno-kiselim bakterijama u statičnoj kulturi, te u ultrazvučnoj kupelji provedena uz dodatak hidrotalcita (gline). Ispitan je utjecaj temperature (t=38-43 °C), omjera gline i mlijeka (R=1-7,5 g/L) te ultrazvuka (ν=0 i 35 kHz) na dinamiku procesa. Odabran je matematički model koji opisuje kinetiku fermentacije i procijenjuje parametre prema eksperimentalno dobivenim podacima, a odnos je između eksperimentalnih i simuliranih podataka bio dobar. Stoga je zaključeno da se model može primijeniti za predviđanje dinamike šaržne mliječno-kisele fermentacije prema vrijednostima varijabli dobivenih u ovom eksperimentu. Provedena je statistička analiza pomoću 23 faktorskog plana, da bi se primjenom eksperimentalnog i regresijskog modela utvrdio utjecaj faktora t, R i ν na kinetiku fermentacije.Batch fermentation of milk inoculated with lactic acid bacteria was conducted in the presence of hydrotalcite-type anionic clay under static and ultrasonic conditions. An experimental study of the effect of fermentation temperature (t=38–43 °C), clay/milk ratio (R=1–7.5 g/L) and ultrasonic field (ν=0 and 35 kHz) on process dynamics was performed. A mathematical model was selected to describe the fermentation process kinetics and its parameters were estimated based on experimental data. A good agreement between the experimental and simulated results was achieved. Consequently, the model can be employed to predict the dynamics of batch lactic acid fermentation with values of process variables in the studied ranges. A statistical analysis of the data based on a 23 factorial experiment was performed in order to express experimental and model-regressed process responses depending on t, R and ν factors

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