The effect of wet heating, dry heating, and washing with acidic butanol on nitrogen solubility profiles, functional properties such as foaming indices and emulsification indices, and other related parameters is investigated in water and 1 M NaCl extracts from dehulled, defatted, and powdered samples of sunflower seeds. The results show that autoclaving at 2 kg/cm2 and roasting at both 100 and 150 "C affect nitrogen solubility of the proteins in water and 1 M NaCl. The foam volume indicates a decrease as a result of acidic butanol treatment, whereas it decreased by 40% in the untreated sample. Foam from samples roasted at 150 "C or autoclaved at 1 and 2 kg/cm2 collapses faster during a period of 120 min as compared to the sample roasted at 100 O C and the control. The emulsification stability was higher in water for all samples as compared to those in sodium chloride solution. The results are explained on the basis of surface properties and physicochemical properties of sunflower seed proteins.

Sunflower seed protein interactions with chlorogenic acid (CGA) result in unfavorable color development. CGA is shown to be more associated with the low molecular weight proteins (LMW). This can alter the properties of the protein, especially the LMW proteins. The sedimentation coefficient of the LMW proteins remained unchanged at 1.8 S. The protein resolved into four peaks on Sephadex G-75 gel nitration. The composition of the second fraction increased from 35% to 53% upon acidic butanol treatment. The last fraction had higher amounts of CGA. The native polyacrylamide gel electrophoresis indicated fast moving bands, but the molecular weights of the three major bands did not change, as seen in SDS-polyacrylamide gel electrophoresis as a result of acidic butanol treatment. The secondary structure of the protein was 19% a-helix, 40% /3-structure, and 41 % aperiodic for the native and 27 % a-helix, 38% /3-structure, and 35% aperiodic for the acidic butanol treated protein. The fluorescence emission maximum indicated a red shift from 330 nm, indicating structural alterations of the proteins.

Proteins in sunflower seeds, heat treated (dry and autoclaved), show changes in physicochemical properties. Changes include the ultraviolet absorption spectrum, specifically at 324 nm due to bound chlorogenic acid. Wet heating under steam pressure at 2 kg/ cm2 causes protein aggregation, as shown by polyacrylamide gel electrophoresis. Sedimentation velocity experiments show that dry heating at 150 °C and wet heating at 2 kg/cm2 increase low molecular weight components (2S) while decreasing the percentage of high molecular weight proteins (US). The gel filtration profiles of proteins from seeds treated at high temperatures (autoclaving at 2 kg/cm2 and dry roasting at 150 °C) also show an increase in the percentage of low molecular weight proteins. Heat-treated total proteins are less susceptible to proteolysis by trypsin and chymotrypsin.

SummaryThe total proteins and helianthinin (11s) from sunflower seeds were chemically modified by acetylation and succinylation. The extent of acetylation of the total proteins and helianthinin were 12%, 51%, 52%, 56% and 12%, 36%, 69%, 71%, respectively, while the extent of succinylation were 8%, 21%, 33%, 49% and lo%, 30%, 44%. 61%. respectively. The extent of modification was monitored by the availability of free lysyl residues in the proteins. The ultraviolet absorption maximum shiftcd to higher wavelengths in total proteins and in helianthinin; there was also an increase in absorbance in the 260 nm wavelength, as a function of increased chemical modification. The sedimentation velocity profile indicated the dissociation of the proteins to low molecular weight fraction (2s) through a 7s component. The dissociation occurred at low modification levels in both total proteins and in helianthinin. There was a gradual red shift and quenching in the fluorescence emission maximum at higher modification levels indicating the denaturation of the proteins as a result of this chemical modification. The change in absorbance as a function of temperature indicates minor changes suggesting that the conformation of the proteins is already altered to significant extents due to the chemical modification. Zusammenfassung