Ultrasound-assisted macroporous resin treatment improves the color and functional properties of sunflower meal protein.

Sunflower meal protein (SMP) has been considered as a high-quality source of plant protein. However, because the chlorogenic acid (CA) contained in sunflower seed meal was prone to oxidation reactions under traditional alkali extraction conditions, the extracted protein has a dark color and some poor functional properties. To this end, this study used ultrasound-assisted macroporous resin treatment to extract SMP. The improvement effects and potential mechanisms of ultrasonic-assisted macroporous resin treatment with different powers (100, 300, and 500 W) on the color and functional properties of SMP were studied. The results showed that compared with untreated sunflower meal protein (USMP), the lightness value (L*), solubility, emulsification, and gel elasticity were significantly enhanced when treated with 100 W and 300 W ultrasonic-assisted macroporous resin. However, when the ultrasonic power was increased to 500 W, the L* value, solubility, emulsification, and gel elasticity decreased instead, indicating that lower power (100 W and 300 W) ultrasonic-assisted macroporous resin treatment significantly improved the color and functional properties of SMP. Further research found that ultrasound-assisted macroporous resin treatment changed the secondary and tertiary structures of SMP, transformed ß-sheet into α-helix and ß-turn through rearrangement, and significantly improved surface hydrophobicity. It shows that ultrasonic-assisted macroporous resin treatment expands the SMP structure and exposes hydrophobic groups, thereby improving the color and functional properties of SMP. This study provides a potential strategy for extracting SMP with light color and good functional properties. It also provides a theoretical basis for the wide application of SMP in food processing.

Structural characterization of calcium-binding sunflower seed and peanut peptides and enhanced calcium transport by calcium complexes in Caco-2 cells.

BACKGROUND: Peptide-Ca complexes can promote Ca absorption. The present study aimed to determine the transport mechanism and structural characteristics of sunflower seed and peanut peptides with high Ca binding capacity with respect to developing third-generation Ca supplements and functional food ingredients. RESULTS: High Ca-binding fractions of 1-3 kDa sunflower seed peptide (SSP4 ) and ≥ 10 kDa peanut peptide (PP1 ) had higher amount of Ca transported than CaCl2 and two hydrolyzed proteins in Caco-2 cells. SSP4 and PP1 were separated by Ca ion metal chelate affinity chromatography, and high Ca-binding fractions were observed for SSP4 -P2 and PP1 -P2 . The amino acid sequences of SSP4 -P2 and PP1 -P2 were characterized by high-performance liquid chromatography-electrospray ionization-time of flight mass spectrometry. Seven and eight peptides were identified from SSP4 -P2 and PP1 -P2 , respectively. These peptides had molecular weights ranging from 1500 Da to 2500 Da and a large number of characteristic amino acid sequences, such as EEEQQQ, EQ-QQQ-QQ, QQ-QQQQQ, E-EEE, EE-EEQ, RR, Q-QQ-QQQ, EE-EQ-EE-Q, QQ-QQQQ, and Q-QQQQ, where 'E' is glutamic acid and 'Q' is glutamine. CONCLUSION: SSP4 and PP1 can promote Ca transport in Caco-2 cells without affecting cell permeability. The amino acid sequences of SSP4 -P2 and PP1 -P2 with high Ca-binding abilities contain characteristic sequences, such as continuous glutamic acid and glutamine, and have low molecular weights. © 2020 Society of Chemical Industry.