Impact of ultrasound pretreatment on whey protein hydrolysis by vegetable proteases

Synthesis and succinylation of starch nanoparticles by means of a single step using sonochemical energy

In the present research work, esterified nanoparticles with 2-octen-1-ylsuccinic anhydride were synthesized from waxy corn starch, to our knowledge for the first time, in a single step of ultrasonic treatment. First, the ultrasound time to produce non-esterified nanoparticles was studied. The results showed that non-esterified nanoparticles had sizes ranging from 63 to 48 nm, as well as polydispersity indexes (PDI) ranging from 0.458 to 0.224 and ζ-potential values ranging from -16 to -24 mV in ultrasonication times ranging from 20 to 100 min. Succinylated nanoparticles were obtained at 80 min with two degrees of substitution i.e., 0.003 and 0.01, hydrodynamic sizes of 57 and 83 nm, PDI of 0.479 and 0.91, and ζ-potential values of -6.27 and -14.03 mV, respectively. The succinylation of nanoparticles was confirmed by FTIR spectroscopy, and it was possible to elucidate the conversion of amylopectin molecules into amylose blocks. The nanoparticles showed stability during storage in aqueous suspension at 4 °C. By means of the ultrasonic technology, destructuring of the waxy corn starch and, at the same time, the succinylation of the nanoparticles in a total time of 120 min was effectively achieved.

Characterization of heat-stable whey protein: Impact of ultrasound on rheological, thermal, structural and morphological properties

Ultrasound, an emerging non-thermal technique, has potential to modify the functionality of bio-molecules like protein. In the present study, the impact of ultrasound on whey protein (WP) was assessed with functional, rheological, heat coagulation and transition temperature, SDS-PAGE, FTIR spectra, scanning electron microscopy and transmission electron microscopy. The results of this study showed that the raw WP had broad bimodal particle size distribution while after ultrasonication, modified WP exhibited narrower distribution along with smaller particle size (0.683 ± 0.225 μm) compared to untreated WP (2.453 ± 0.717 μm). The solubility of WP also increased after ultrasonication (72.22 ± 0.68% to 79.21 ± 1.08%). During the rheological evaluation, both the samples exhibited Newtonian behaviour but, the modified WP exhibited dramatically higher storage modulus (G') throughout the temperature profile compared to raw WP mainly due to enhanced proteins aggregation during heating which revealed more elastic and stronger gel. The modified WP exhibited significantly higher (about 6-times) heat stability compared to raw WP which signified that after ultrasonication the WP can withstand higher temperature during processing for longer time. The results were also confirmed by higher transition temperature (T_peak) of modified WP (93.32°) compared to untreated WP (81.93 °C). The SDS-PAGE profile of raw and modified WP showed that the ultrasound significantly decreased the bands density of low molecular weight molecules (β-lactoglobulin and α-lactalbumin). FTIR spectra also showed noticeable difference between the secondary structure component of raw and modified WP. Finally, the structural micrographs of raw and modified WP from SEM and TEM analysis also confirmed the adequacy of modification of WP employing non-thermal techniques. The modified WP revealed smaller, regular and more homogenous and ordered structures compared to untreated sample.

Immobilized enzymolysis of corn gluten meal under triple-frequency ultrasound

The single frequency ultrasound mode is difficult to achieve an higher enzymolysis efficiency. The cost of protein enzymatic hydrolysis, using free enzyme is higher because the enzyme cannot be used repeatedly. Therefore, the effects of triple-frequency ultrasound (TFU) treatment on the performance, kinetics, and thermodynamics of immobilized Alcalase enzymolysis of corn gluten meal (CGM) were investigated in this research. The results showed that degree of hydrolysis (DH), peptide concentration, ACE inhibitory activity, and relative enzyme activity were increased by 20.6 %, 34.4 %, 24.1 %, and 25.8 %, respectively, by TFU treatment at the optimum conditions compared to the control. Kinetics and thermodynamic analyses revealed that TFU treatment successfully decreased the apparent constant (KM) by 27.0 % and increased the reaction rate constants (k) by 32.1 –200 % at 303.15–343.15 K. The energy of activation (Ea), enthalpy of activation (ΔH), and entropy of activation (ΔS) were reduced by 17.1 %, 15.2 –15.3 %, and 24.1 –31.8 %, respectively. Immobilized enzymolysis assisted by TFU was proved to be an efficient method to increase the enzymolysis efficiency, enzyme activity, and antihypertensive activity of the peptides through performance and mechanism discussion.