Improved heat stability of protein solutions and O/W emulsions upon dry heat treatment of whey protein isolate in the presence of low-methoxyl pectin

The non-covalent and covalent interactions of whey proteins and saccharides: influencing factor and utilization in food

During the application of Whey proteins (WPs), they often have complex interactions with saccharides (Ss), another important biopolymer in food substrate. The texture and sensory qualities of foods containing WPs and Ss are largely influenced by the interactions of WPs-Ss. Moreover, the combination of WPs and Ss is possible to produce many excellent functional properties including emulsifying properties and thermal stability. However, the interactions between WPs-Ss are complex and susceptible to some processing conditions. In addition, with different interaction ways, they can be applied in different fields. Therefore, the non-covalent interaction mechanisms between WPs-Ss are firstly summarized in detail, including electrostatic interaction, hydrogen bond, hydrophobic interaction, van der Waals force. Furthermore, the existence modes of WPs-Ss are introduced, including complex coacervates, soluble complexes, segregation, and co-solubility. The covalent interactions of WPs-Ss in food applications are often formed by Maillard reaction (dry or wet heat reaction) and occasionally through enzyme induction. Then, two common influencing factors, pH and temperature, on non-covalent/covalent bonds are introduced. Finally, the applications of WPs-Ss complexes and conjugations in improving WP stability, delivery system, and emulsification are described. This review can improve our understanding of the interactions between WPs-Ss and further promote their wider application.

Physicochemical and structural characterization of whey protein concentrate-tomato pectin conjugates

BACKGROUND

Protein-pectin conjugates, obtained through a controlled Maillard reaction in blends of precursors, are studied for their contribution to improving the emulsifying and thermal properties of proteins. The objective was to obtain a conjugate between whey protein concentrate (WPC) and non-conventional pectins extracted in acid (acid tomato pectin, ATP) and aqueous medium (water tomato pectin, WTP) from industrialized tomato residues (tomato waste, TW), characterize the conjugates and study their emulsion properties. The Maillard reaction was carried out at 60 °C and 75% relative humidity in blends with 2:1 proportions; 1:1 and 1:2 (m_protein :m_pectin ) for 3, 6 and 12 days. Conjugates were compared concerning treated and untreated WPC.

RESULTS

The WPC-ATP conjugate showed significant increases in color difference (ΔE). The electrophoresis profile of the conjugates showed diffuse bands of molecular weight between 37 and 250 kDa and a reduction in the intensity of bands characteristic of WPC (α-lactalbumin and β-lactoglobulin). Thermal analysis showed an increase in the peak temperature and a reduction in the enthalpy change in protein denaturation, associated with the formation of conjugates. The infrared spectroscopy of the conjugates, in the amide III zone (1300-1100 cm^-1 ), indicated an increase in the relative peak area associated with the unfolding and exhibition of the hydrophobic zones of the WPC fraction. The emulsions formulated with the conjugates showed a significant increase in the emulsifying stability index (ESI) (P < 0.05) concerning the treated and untreated WPC emulsions.

CONCLUSION

The formation of conjugates increased the emulsifying properties and improved the thermal stability of WPC, showing an innovative and alternative food ingredient too. © 2023 Society of Chemical Industry.

The complex of whey protein and pectin: Interactions, functional properties and applications in food colloidal systems - A review

This review describes the mechanism of non-covalent/covalent interaction of whey protein-pectin (WPP) complexes, including electrostatic interaction, steric hindrance, cross-linking and Maillard reaction. The interaction between whey protein and pectin determines the form of the complex in the system, i.e. co-dissolution, precipitation, separation, complex coacervation and compounding. The interaction of WPP is affected by environmental conditions and its own properties, including several factors such as pH, polymer concentration and ratio, temperature, and ionic strength. In addition, the functional properties of WPP complexes are discussed through illustrative examples. The complexes with good emulsification, heat stability, gelling properties and biological activity have promising application prospects. WPP complexes have been widely studied for application in food colloidal systems, including protein beverages, delivery systems for bioactive substances, fat substitutes and food preservation films/coatings. The understanding of the interaction and functional properties of WPP complexes provides theoretical support for the improvement and design of new food colloidal systems.

Pectin-peptide complexes ameliorated physicochemical stabilities and in vitro digestion abilities of β-carotene loaded emulsions

To improve the stabilities of low methoxy pectin (LMP) stabilized O/W emulsions for the delivery of bioactive substances, LMP was firstly modified with soy peptide (SP), corn peptide (CP) and whey protein peptide (WPP), respectively, by using dry-heat method, then the properties of LMP-peptide complexes stabilized O/W emulsions were characterized and the in vitro digestion of emulsions with β-carotene was test to evaluate the potential applications. LMP-peptide complexes were formed by covalent bonds according to FT-IR spectroscopy. Compared to LMP stabilized emulsions, LMP-peptide complexes stabilized emulsions had smaller droplet sizes and higher stabilities in the changed pH value, temperature and ionic strength. Based on the results of in vitro digestion tests, LMP-SP and LMP-WPP obtained by incubating LMP with peptides at 60 °C for 12 h at the weight ratio of 4:1 were more suitable for the preparation of O/W emulsions to deliver camellia oil and β-carotene.

The mechanism of improved thermal stability of protein-enriched O/W emulsions by soy protein particles

Growing interest in nutritional and functional foods has motivated the design of protein-enriched products in the food industry, which, however, is greatly challenged by undesirable aggregation and gelation of proteins induced by heating from the pasteurization process. In this study, we reported the preparation of heat-stable soy protein particles (SPPs) by a simple preheating process (100 °C for 30 min) at pH 6.2 and 0.5% (w/v) protein concentration. As a proof of concept, the thermal stability of high-protein emulsions prepared by SPPs compared to native soy proteins (SPs) was investigated. The results showed that high-protein emulsions stabilized by SPPs exhibited appreciable heat stability, whereas SPs gelled when both samples were tested at an identical concentration (10%, w/v). In addition, the emulsions prepared by SPPs demonstrated lower values of storage modulus and viscosity along with a stable size by heat treatment as well as a more stable coated protein layer, in contrast to those prepared by SPs presenting macroscopic aggregation and an unstable coated protein layer. The results would provide valuable information in terms of the development of heat-stable, high-protein, and well-dispersed food emulsions that may find numerous applications in the food industry.