ABSTRACT
This study monitored the influence of milk samples temperature on the measuring accuracy of FT-NIR spectroscopy in milk content analysis. Reference methods were used to determine dry matter, fat, protein, and lactose content in cow's milk. Milk samples were measured in reflectance mode on an integrating sphere with the use of a compression cuvette and a transflectance cuvette, ensuring a beam trajectory length of h = 0.2 mm. The samples were measured at 18, 20, 22, 24, and 40°C, and analyses were performed at 100 scans at a resolution of 8 cm-1. The measurements were influenced by the temperatures of the samples during the evaluation of all analyzed constituents (P < 0.05). Our results confirmed that the accurate determination of milk constituents requires maintaining, during analysis, the temperature conditions of the samples and the conditions for which the spectrophotometer calibration was designed.
Subject(s)
Data Accuracy , Milk/chemistry , Spectroscopy, Near-Infrared/methods , Temperature , Animals , Discriminant Analysis , Lactose/analysis , Milk Proteins/analysis , Triglycerides/analysisABSTRACT
Stems of amaranthus are considered as prospective biofuel in the Czech Republic. The study presents results of water sorption tests of this biomass in the range of 10-30 degrees C and water activity (a(w)) ranging from 0.4 to 0.99. The experimental procedure used was a gravimetric dynamic method. Four sorption models (Chung-Pfost, Halsey, Henderson, Oswin) were evaluated. The modified Henderson's equation was the best model for moisture adsorption and desorption of amaranthus stems. Critical values of equilibrium moisture content, corresponding to the a(w)=0.6, were 11.45% and 13.28%(wb) for water adsorption and desorption respectively, at the temperature of 20 degrees C. Heat of sorption (q(st)) was calculated using the chosen sorption model and Clausius-Clapeyron equation. An exponential function was found to fit the experimental q(st) values of amaranthus stems at moisture contents ranging from 7% to 40%(wb) for adsorption and desorption.
