Modellversuche zum Randweichwerden von K?sen

Zusammenfassung In Modellversuchen mit Suspensionen konnte ein eindeutiger Einfluß des p_H-Wertes auf die Löslichkeit des Labcaseins festgestellt werden. Das Kochsalz wirkt auf Labcasein quellungsfördernd; bei gleichzeitiger Säureeinwirkung treten Löslichkeiten bis zu 80% auf. Im optimalen Bereich bei p_H 5 ist die Löslichkeit unabhängig von der Kochsalzkonzentration.Von untergeordneter Bedeutung auf die Löslichkeit des Labcaseins ist der Fettgehalt, die Art und Weise der Labfällung sowie der Einfluß der Vorerhitzung der Milch.Auf Grund dieser Feststellungen wird die Erscheinung des Randweichwerdens von Käsen als ein ungünstiges Zusammentreffen bestimmter Säure- und KochsalzKonzentrationen angesehen.Diese Arbeit stellt einen Auszug aus der Dissertation vonGerharda Schattenfroh dar: Über die Ursachen der Quellung und Lösung des Labeaseins im Käse. Techn. Hochschule München 1957.     

Wärmeenergetische Vorgänge beim Abbinden von Harnstoffharzen

Zusammenfassung Die W?rmet?nung bei der Kondensation von Harnstoffharzen wurde bei Raumtemperatur gemessen. Der erforderliche saure p_H-Bereich wurde einmal durch Zugabe von verschiedenen S?uren in wechselnder Konzentration und zum anderen durch die Ammoniumsalze eben derselben S?uren eingestellt. Es zeigt sich eine Abh?ngigkeit der W?rmet?nung vom p_H-Wert, wobei die Art der verwendeten S?ure keinen sichtbaren Einflu? ausübt. Bei der Anwendung der entsprechenden Ammoniumsalze tritt als Nebenreaktion die Hexamethylentetramin-Bildung auf. Am. Beispiel des Ammoniumchlorids erweist sich, da? die W?rmebilanz bei beiden Arbeitsverfahren übereinstimmend ist, wogegen sich bei den Systemen der Tabelle 5 eine Diskrepanz in der W?rmebilanz ergibt, deren Aufkl?rung den Gegenstand weiterer Untersuchungen bildet.     

Petroleum-free extraction of oil from soybeans with supercritical CO2

Full-fat soyflakes are readily extracted with supercritical carbon dioxide (SC-CO₂) at pressures of 3,000~10,000 psig and 50 C. Under these conditions, SC-CO₂ has the density of a liquid and the diffusivity of a gas. Therefore, equilibrium solubility is readily achieved in a short-path batch extractor which permits high gas flow rates. Soybean oil extracted with SC-CO₂ is lighter in color and contains less iron and about one-tenth the phosphorus of hexane-extracted crude oil from the same beans. The lower phosphorus content is reflected in a chromatographic refining loss of 0.6% compared to 1.9% for hexane crude. Refined oils from hexane and SC-CO₂ extraction had equivalent odor and flavor scores initially and after 4 days' storage at 60 C. Carbon dioxide, an ideal solvent for extraction of food products, is low-cost and readily available from fermentation processes and could free over 20 million gallons of costly hexane per year for essential energy uses.     

Oxidative stability of seed oils extracted with supercritical carbon dioxide 1

Dry-milled corn germ, soybean and cottonseed flakes were extracted (at 70-90 C and 12,000 psi) with supercritical carbon dioxide (SC-CO₂) to yield crude oils. Oxidative stability of the crude oils was determined and compared to similar products obtained by conventional expeller and/or prepress solvent extraction. Under Schall oven storage conditions (60 C), SC-CO₂-extracted oils undergo rapid deterioration and fail to show the normal induction period observed with conventional expeller and solvent-extracted crude oils. The levels of tocopherols found in SC-CO₂-extracted oils are comparable to those obtained by expeller or solvent extraction, while phospholipids present in significant amounts in conventional crude oils are essentially absent from SC-CO₂-processed crudes. The addition of phosphatides to SC-CO₂-extracted crude oils improves oxidative stability, which suggests that both tocopherols and phospholipids are required to stabilize crude oils against autoxidation. Heating of SC-CO₂-extracted crude oils to deodorization temperatures improves oxidative stability. The destruction of fat hydroperoxides under these conditions probably accounts for improved oxidative stability. A combination of heat and the addition of citric acid and phenolic antioxidants resulted in further improvement of oxidative stability. Presented at the American Oil Chemists’ Society Annual Meeting in Philadelphia, PA, in May 1985.     

Die Wahl des optimalen Verfahrens für die Bestimmung des Primärradikalabbruchs aus Geschwindigkeitsdaten

The various plots for estimating the ratio of rate constants characteristic for primary radical termination, k₅/k₁k₂, have been examined systematically. Apart from the special case d ≡ k₃k₆/k₅² = 1 there is no exact linear relationship between the general quantity \documentclass{article}\pagestyle{empty}\begin{document}${\rm Y \equiv (\sqrt {c_S} c_{M}/v_{Br})^{n}}$\end{document} and the general variable \documentclass{article}\pagestyle{empty}\begin{document}${\rm X \equiv (\sqrt {c_S} /c_M)^{s} (v_{Br}/c_M^{2} )^{1 - s}}$\end{document}. In any case, however, Y can he expressed as a power series of X. Therefore the best way to obtain the most favourable linear representation of Y as a function of X is to choose s and n according to the condition that the coefficient of the term quadratic in X has to disappear (n ? 2 s + d = 0) and the coefficient of the X³-term also equals 0 or is at least close to 0. Under these conditions even those data can be represented in an almost perfect linear form which show variations of the quantity \documentclass{article}\pagestyle{empty}\begin{document}$({\rm \sqrt{c_{s}}c_{M}/v_{Br})}$\end{document} by a factor of \documentclass{article}\pagestyle{empty}\begin{document}$\sqrt{2}$\end{document} or more for different initiator concentrations c_s. If additionally allowance is made for the consumption of monomer by the initiation process the desired ratio of rate constants, k_s/k₁k₂, is obtained from the plot of Y vs. X according to the equation The application of this method is illustrated using an example from literature.     

Impact and wear resistance of polymer nanocomposites at low filler content

It is well known that inorganic filler particles enhance the mechanical and tribological properties of polymers. The stiffness, toughness, and wear performance of the composites are extensively determined by the size, shape, volume content, and especially the dispersion homogeneity of the particles. In the present study, various amounts of micro‐ and nano‐scale particles (titanium dioxide TiO₂, 200–400 nm, calcium silicate CaSiO₃, 4–15 μm) were introduced into an epoxy polymer matrix for its reinforcement. The influence of these particles on the impact strength, dynamic mechanical thermal properties, and block‐on‐ring wear behavior was investigated. Using only the nano‐particles, the results demonstrate the best improvement in stiffness, impact strength, and wear resistance of the epoxy at a nano‐particle content of 4 vol% TiO₂. Therefore, this nanocomposite was used to act as a matrix for the CaSiO₃ micro‐particles, in the hope of finding synergistic effects between the micro‐ and the nano‐particles. Results show, in fact, a further improvement of wear resistance and stiffness, whereas the impact strength suffers. Geometrical properties of the particles, the homogeneous dispersion state, energy dissipating fracture mechanisms, and a transition of wear mechanisms mostly contribute to the increase in performance.