No abstract

Diglycerides and phytosterol esters are two important functional lipids. Phytosterol esters mixed with dietary diglyceride could not only influence body weight but also prevent or reverse insulin resistance and hyperlipidemia. In this study, a kind of novel "functional oil" rich in both diglycerides and phytosterol esters was prepared with "one-pot" enzymatic transesterification. First, lipase AYS (Candida rugosa) was immobilized on the porous cross-linked polystyrene resin beads (NKA) via hydrophobic interaction. The resulting immobilized AYS showed much better transesterification activity and thermal stability to freeways. On the basis of the excellent biocatalyst prepared, a method for high-efficiency enzymatic esterification of phytosterols with different triglycerides to produce corresponding functional oils rich in both diglycerides and phytosterol esters was developed. Four functional oils rich in both diglycerides and phytosterol esters with conversions >92.1% and controllable fatty acid composition were obtained under the optimized conditions: 80 mmol/L phytosterols, 160 mmol/L triglycerides, and 25 mg/mL AYS@NKA at 180 rpm and 50 °C for 12 h in hexane. The prepared functional oil possessed low acid value (≤1.0 mgKOH/g), peroxide value (≤2.1 mmol/kg), and conjugated diene value (≤1.96 mmol/kg) and high diglyceride and phytosterol ester contents (≥10.4 and ≥20.2%, respectively). All of the characteristics favored the wide application of the functional oil in different fields of functional food.

[431][432][433][434][435][436][437][438]. Accurate in situ determination of soil water content is important in many fields of agricultural, environmental, hydrological, and engineering sciences. As numerous soil water content sensors are available on the market today, the knowledge of their performance will aid users in the selection of appropriate sensors. The objectives of this study were to evaluate five soil water sensors in the laboratory and to determine if laboratory calibration is appropriate for the field. In this study, the performances of five sensors, including the Profile Probe™ (PP), ThetaProbe™, Watermark™, Aqua-Tel™, and Aquaterr™ were compared in the laboratory. The PP and ThetaProbe™ were more accurate than the other soil water sensors, reproducing soil water content using factory recommended parameters. However, when PP was installed on a loamy sand in the field, the same soil that was used for the laboratory evaluation, it overestimated field soil water, especially at depth. Another laboratory experiment showed that soil water content readings from the PP were strongly influenced by soil bulk density. The higher the soil bulk density, the greater was the overestimation of soil water content. Two regression parameters, a 0 and a 1 , which are used to convert the apparent dielectric constant to volumetric water content, were found to increase linearly with the soil bulk density in the range of 1.2 to 1.6 Mg m -3 . Finally, the PP was calibrated in the field and a good calibration function was obtained with an r 2 of 0.87 and RMSE of 2.7%. The values of a 0 and a 1 obtained in the field were different from factory recommended parameters (a 0 = 2.4 versus 1.6 while a 1 = 12.5 versus 8.4) and were independent of soil depth, bulk density, and texture. As such, individual field calibration will be necessary to obtain precise and accurate measurement of soil water content with this instrument. Mesurer avec exactitude la teneur en eau du sol in situ revêt une grande importance dans maints domaines scientifiques liés à l'agriculture, à l'environnement, à l'hydrologie et au génie. Étant donné la multitude de détecteurs actuellement offerts sur le marché, sélectionner le bon s'avérera plus facile si l'on connaît bien leur performance. L'étude devait servir à évaluer cinq détecteurs au laboratoire puis à établir si l'étalonnage effectué au laboratoire concordait avec les relevés obtenus sur le terrain. Dans le cadre du projet, les auteurs ont comparé la performance des détecteurs Profile Probe MC (PP), ThetaProbe MC , Watermark MC , Aqua-Tel MC et Aquaterr MC en laboratoire. Les sondes PP et TheraProbe MC sont les plus précises, car elles mesurent la concentration d'eau à partir de paramètres recommandés par le fabricant. Toutefois, testée sur le terrain dans un sable loameux, la sonde PP surestime la teneur en eau du même sol que celui employé pour l'essai en laboratoire, principalement au niveau de la profondeur. Une autre expérience en laboratoire montre que les relevés de la sonde PP subissent fortem...