Thickness and dielectric constant determination of thin dielectric layers

We derive a method for the determination of the dielectric constant and thickness of a thin dielectric layer, deposited on top of a thick dielectric layer which is in turn present on a metal film. Reflection of p- and s-polarized light from the metal layer yields minima for certain angles of incidence where the light is absorbed by the metal. The thin dielectric layer causes shifts in the angles at which the minima occur, from which the thickness and dielectric constant can be obtained. The model is tested for 3.5 and 14 nm thick photoresist gratings

Effect of extraction pH on heat-induced aggregation, gelation and microstructure of protein isolate from quinoa (Chenopodium quinoa Willd)

The aim of this study was to determine the influence of extraction pH on heat-induced aggregation, gelation and microstructure of suspensions of protein isolates extracted from quinoa (Chenopodium quinoa Willd). Quinoa seed protein was extracted by alkaline treatment at various pH values (pH 8 (E8), 9 (E9), 10 (E10) and 11 (E11)), followed by acid precipitation. The obtained protein isolates were freeze dried. The protein isolates E8 and E9 resulted in a lower protein yield as well as less protein denaturation. These isolates also had a higher protein purity, more protein bands at higher molecular weights, and a higher protein solubility in the pH range of 3-4.5, compared to the isolates E10 and E11. Heating the 10% w/w protein isolate suspensions E8 and E9 led to increased aggregation, and semi-solid gels with a dense microstructure were formed. The isolate suspensions E10 and E11, on the other hand, aggregated less, did not form self-supporting gels and had loose particle arrangements. We conclude that extraction pH plays an important role in determining the functionality of quinoa protein isolates

Capacité de liaison du calcium des orthophosphates et polyphosphates organiques et inorganiques.

The aim of this research was to determine the calcium-binding capacity of inorganic and organic ortho- and polyphosphates. This calcium-binding capacity can be used to influence the stability of, for example, casein micelles in dairy systems. Four phosphates were selected: disodium uridine monophosphate (Na$_2$UMP, organic orthophosphate), disodium hydrogen phosphate (Na$_2$HPO$_4$, inorganic orthophosphate), sodium phytate (SP, organic polyphosphate), and sodium hexametaphosphate (SHMP, inorganic polyphosphate). Concentrations of up to 100 mmol$\cdot$L$^{-1}$ phosphate were added to a 50 mmol$\cdot$L$^{-1}$ CaCl$_2$ solution. The samples were prepared at pH 8.0 and were analyzed before and after sterilization for calcium-ion activity, conductivity, pH, sediment, and turbidity. Both SHMP and SP are strong chelators, as calcium ions bind to these phosphates in the ratio of 3:1 and 6:1, respectively. Calcium ions also strongly bind to Na$_2$HPO$_4$, but in a ratio of 3:2 with insoluble Ca$_3$(PO$_4$)$_2$ complexes as result. The equilibrium position of Na$_2$UMP is not strong towards the chelated complex, and significant levels of free calcium and free phosphate can exist. An equilibrium constant of $0.29 \pm 0.08$ L$\cdot$mol$^{-1}$ was determined for calcium uridine monophosphate (CaUMP) complexes. Both calculation of the equilibrium constant and analysis on the CaUMP precipitate confirmed a reactivity of 1:1 between calcium and Na$_2$UMP. The CaUMP complexes are well soluble at ambient temperature, and insoluble complexes appear after sterilization, because the solubility of CaUMP decreases during heating. Finally, we concluded that the structure of phosphate molecules determines their calcium-binding capacity rather than organic or inorganic origin of phosphates.Le but de cette recherche était de déterminer la capacité de liaison du calcium des orthophosphates et polyphosphates inorganiques et organiques. Cette capacité de liaison du calcium peut être utilisée pour influencer la stabilité des micelles de caséine dans les systèmes laitiers. Quatre phosphates ont été sélectionnés : l'uridine monophosphate disodique (Na$_2$UMP, orthophosphate organique), l'hydrogenophosphate disodique (Na$_2$HPO$_4$, orthophosphate inorganique), le phytate de sodium (SP, polyphosphate organique) et l'hexametaphosphate de sodium (SHMP, polyphosphate inorganique). Des concentrations de phosphate allant jusqu'à 100 mmol$\cdot$L$^{-1}$ ont été ajoutées à une solution contenant 50 mmol$\cdot$L$^{-1}$ de calcium. Les échantillons préparés à pH 8,0 ont été analysés avant et après stérilisation pour l'activité de l'ion calcium, la conductivité, le pH, le sédiment et la turbidité. SHMP et SP sont tous les deux des chélateurs forts, puisque les ions calcium sont liés à ces phosphates dans un ratio 3:1 et 6:1 respectivement. Les ions calcium sont aussi fortement liés au Na$_2$HPO$_4$, mais dans un ratio de 3:2, résultant dans la formation de complexes insolubles de Ca$_3$(PO$_4$)$_2$. Le Na$_2$UMP n'est pas aussi fortement complexé et des taux significatifs de calcium libre et de phosphate libre peuvent exister. Une constante d'équilibre de $0,29 \pm 0,08$ L$\cdot$mol$^{-1}$ a été déterminée pour les complexes d'uridine monophosphate de calcium (CaUMP). Le calcul de la constante d'équilibre et l'analyse du précipité deCaUMPont confirmé l'un et l'autre une réactivité de 1:1 entre le calcium et le Na$_2$UMP. Les complexes CaUMP sont bien solubles à température ambiante mais des complexes insolubles apparaissent après stérilisation parce que la solubilité du CaUMP diminue au cours du chauffage. Finalement, nous pouvons conclure que la structure des molécules de phosphate détermine leur aptitude à lier le calcium plus que l'origine organique ou inorganique des phosphates

Denaturation and in Vitro Gastric Digestion of Heat-Treated Quinoa Protein Isolates Obtained at Various Extraction pH

The aim of this study was to determine the influence of heat processing on denaturation and digestibility properties of protein isolates obtained from sweet quinoa (Chenopodium quinoa Willd) at various extraction pH values (8, 9, 10 and 11). Pretreatment of suspensions of protein isolates at 60, 90 and 120 °C for 30 min led to protein denaturation and aggregation, which was enhanced at higher treatment temperatures. The in vitro gastric digestibility measured during 6 h was lower for protein extracts pre-treated at 90 and 120 °C compared to 60 °C. The digestibility decreased with increasing extraction pH, which could be ascribed to protein aggregation. Protein digestibility of the quinoa protein isolates was higher compared to wholemeal quinoa flour. We conclude that an interactive effect of processing temperature and extraction pH on in vitro gastric digestibility of quinoa protein isolates obtained at various extraction pH is observed. This gives a first indication of how the nutritional value of quinoa protein could be influenced by heat processing, protein extraction conditions and other grain components