The foaming ability (foam capacity and stability) of protein isolates from faba beans (Vicia faba L.) depends closely on the manner of isolation and treatment of the isolates. Unmodified isolates possess a moderate foaming ability with a maximum foam capacity of 210% in alkaline solution (pH 10.0) at concentrations of about 3%. The foam capacity and stability can be improved by treatment with isopropanol or moderate temperature, as well as by denaturing by alkali or by specially heating at 80 degrees C. Thereby modified preparations are formed possessing a foam capacity of more than 400% and a foam stability of 80-100%. High concentrations of protein favour the formation of stable foams. Succinylation improves the foam formation properties of proteins. Maximum values of foam capacity (approximately equal to 400%) are produced at a high degree of succinylation, that is after blocking more than 80% of protein amino groups, in neutral solution, while the foam stability under these conditions decreases. Heating at 80 degrees C, high protein concentrations (10%) and a weak acidic milieu (pH 5.5) favour the formation of stable foams from succinylated proteins.

Functional propertiesas solubility, water and oil adsorption, emulsifying capacity. emulsion activity and stabilityof protein isolates from faba beans, soybeans and sunflower seed depending on the isolation process were determined.Proteins isolated under mild conditions, it means by precipitation using dialysis or dilution of salt extracts with water, show the highest solubility, characterized by a sharp minimum of solubility at a rather narrow range of pH. An incubation of the precipitated proteins at low pH (pH 2) results in a decrease of the solubility on the alcaline and acidic part of the solubility profile.On the contrary to the decreased solubility, the proteins denatured by acid show an increased water adsorption capacity. Depending on the kind of protein and the conditions of preparation these values can reach the manifold ones of the control. Smaller increases of oil adsorption in acid-denatured proteins were found, too.The emulsion activity and stability were not or only slightly influenced, but the emulsifying capacity was strongly decreased by the denaturation procedure. The emulsifying capacity was influenced by the solubility of the protein, but a strong correlation does not exist.The high water adsorption of Promine D can be reached by the other plant proteins after denaturation. The sunflower protein showed the highest emulsifying capacity.Increasing the pH from the isoelectric range to 7 improves all studied functional properties.'

Ein aus Legumin und Vicilin bestehendes Rohglobulinpriiparat aus Ackerbohnen ( Viciafubu L.) dissoziiert nach Succinylierung der Aminogruppen in Untereinheiten, die sedimentationsanalytisch als 2.84-Fraktion erscheinen. Gelelektrophoretisch lassen sich bereits in Modifikaten mit einem Succinylierungsgrad von 37 Y, die assoziierten F'roteine nicht mehr nachweisen, die Proteinmuster hochgradig succinylierter Proben weisen mindestens 6 Zonen auf.Die pH-Liislichkeitsprofle der succinylierten Proteine zeigen eine vom Succinylierungsgrad abhangige Verschiebung des Loslichkeitsminimums nach niedrigeren pH-Werten und eine Herabsetzung der Liislichkeit bei pH-Werten < 4.MiiDig (27Xig) modifizierte Proteine zeigen eine Zunahme der Wasserbindung um 25% und der albindung um 40". Eki stslrker succinylierten Proben sinkt das 6lbindevermogen auf 80 bis 60% des Kontrollwertes. Die Emulgiereigenschaften (Emulgierkapazitat. Emulgieraktivitlt, Emulsionsstabilitat) der Ackerbohnenproteine lassen sich durch Succinylierung wesentlich verbessern.In einer vorangegangenen Mitteilung ist iiber die physikochemischen und funktionellen Eigenschaften succinylierter Caseinproben berichtet worden [2]. Gegenstand der vorliegen: den Arbeit sind analoge Untersuchungen an verschieden stark succinylierten Proben eines Proteinisolates aus Ackerbohnen ( Viciu .fubu L.). Material und Methoden ProteinisolirrungEs wurden Ackerbohnen der Sorte Fribo in kner Schillmiihle geschiilt und gemahlen. Die Proteinextraktion erfolgte durch 2 min Homogenisieren (Ultraturrax -Homogenisator) von 80 g Samenmehl mit 800 mi Wasser bei knem pH-Wert von 8.0-8.5. Aus dem klarzentrifugierten Extrakt wurde die Globulin-Frdktion durch Zugabe von Salzsiiure bei einem pH-Wen von 4,5 isoelektrisch ausgeWllt. Nach mehrmaligem Waschen wurde das Globulin-Praparat gefriergetrocknet.

Succinylation of amino groups of the casein complex results in a spontaneous dissociation of the protein into low-molecular 1.8-S components. Succinylated samples of casein are characterized by a higher electrophoretic mobility of the components in alkaline mediums and by a lower mobility in acidic buffer systems. The anodic migration in alkaline buffer systems increases depending on the degree of modification. This effect is more pronounced for the beta-casein than for the alpha s-casein fraction. In the potentiometric acid-base titration of the modified casein a hysteresis occurs during the back-titration. Increasing with the degree of modification, this effect points to a more or less strong break-up of the structure (entropy production). The solubility minimum of casein is shifted to lower pH values by succinylation. Samples succinylated to 90 or more per cent of the amino groups are insoluble at pH less than 3.5. Succinylated casein shows at a moderate degree of substitution (approximately equal to 40%) a highly increased water adsorption capacity. The oil adsorption capacity of the protein decreases after succinylation. Amongst the modified casein samples those ones with the highest water adsorption show the highest oil adsorption, too. The emulsifying capacity of low (approximately equal to 20%) succinylated casein samples decreases below the value determined for the unmodified protein. At higher modified samples the emulsifying capacity increases as the degree of succinylation increases. The emulsifying activity and emulsion stability of modified samples are lower than that measured for the parent protein. The foaming capacity of the casein is not improved by succinylation.

The reaction of raw globulin preparations from sunflower seed with a 10-30-fold excess of succinic anhydride results in a maximum blockage of 85-92 % of the protein amino groups.The water absorption of the protein increases 2-fold after a 26 % succinylation and nearly 6-fold after an exhaustive modification. The oil absorption decreases after a moderate (42 %) succinylation of the protein and reaches the value of unmodified protein after being exhaustively modified.The emulsifying capacity (EC) is highest in the native unmodified protein. Treatment with acidic aqueous butanol for removing phenolic compounds results in a decrease of EC. The latter increases again after an exhaustive succinylation of butanol-treated protein. A high level of modification ( 8 6 7 %) improves the emulsifying activity and the emulsion stability of the protein. Succinylation increases the foam capacity but does not influence the high foam stability of the protein.A broadening of the solubility minimum and a shift of its position from pH 4.5-5.5 to pH 2.5-4.8 takes place at high levels of chemical modification.Relations are discussed between the dissociation of the protein into the subunits at a high level of substitution ( 2 80 %) determined by gel electrophoresis and the functional properties.