Low-molecular-weight proteins from sunflower (Helianthus annuus L.) seed: effect of acidic butanol treatment on the physicochemical properties

Abstract

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.

Sunflower proteins: overview of their physicochemical, structural and functional properties

“…Several authors have claimed that, in sunflower products, CGA appears mainly in the form of complexes or bound to proteins. The binding to sunflower proteins has been reported to occur either preferentially with low‐molecular‐weight proteins48–52 or high‐molecular‐weight proteins53 or non‐preferentially 54, 55. Non‐covalent interactions of both caffeic and quinic acids (constituents of CGA) with helianthinin have also been reported 56.…”

“…Several attempts have been made to reduce the presence of phenolic compounds in sunflower protein products. They are mainly based on the following principles: (a) extraction with mixtures of organic solvents and water,9, 10, 41, 51, 52, 67–72 (b) extraction with aqueous solutions of acids, salts or/and reducing agents,53, 55, 66, 73–75 (c) membrane filtration,76 (d) removal by co‐precipitation or complexing pigments and other non‐protein compounds77–79 and (e) combinations thereof 20, 54, 80–84…”

“…Aqueous mixtures (50–60% v/v) of methanol, ethanol and 2‐propanol were shown to give much lower protein losses and higher CGA extractability than propanol or isobutanol 88. Several studies have pointed out the denaturing effect of butanol52, 70, 83 and acetone 72, 89. Ethanol/water mixtures were reported to result in products with low protein solubility71, 82, 90 or a low degree of polyphenol extraction 67, 69.…”

Characterization of Five Sunflower Varieties Cultivated in Brazil

“…Aqueous processing of sunflower seeds prior the oil extraction removes the CGA up to 88% and improves the oil and meal quality (3,9). The dehulling of sunflower seeds is used in industrial processing, aiming to remove the fiber and the wax, to increase the oil yield and to improve the oil and meal qualities (11).…”

Effect of the type and level of hydration of alcoholic solvents on the simultaneous extraction of oil and chlorogenic acids from sunflower seed press cake

“…Regarding the extraction of CA, several studies report that mixtures of organic solvents and water present the best combination for the extraction of these compounds . In general, CAs are obtained from sunflower seed meals that have previously been subjected to defatting using hexane and petroleum ether as solvents .…”