Inhibition Effect of Ultrasound on the Formation of Lysinoalanine in Rapeseed Protein Isolates during pH Shift Treatment

Abstract

pH shift is an effective technique for modifying functional properties of food proteins. However, it can increase lysinoalanine (LAL) content under alkali conditions, thus limiting the use of proteins. This study investigated the inhibition effect of ultrasonic parameters on LAL formation in rapeseed protein isolates (RPI) during pH shift treatment (pH-ST). Results showed that the content of LAL decreased by 49.5% and 74.1%, following the use of ultrasound (28 kHz, 40 W/L, 40 °C, and 30 min) under alkali and acidic treatment, respectively. Structural analysis showed that after ultrasonic irradiation, increased sulfhydryl groups and amino acids reduced the dehydroalanine and, thus, decreased LAL content. Particle size, secondary structure, and microstructure (SEM, AFM) analyses showed relative dispersion in protein distribution, reducing intermolecular or intramolecular cross-linking, thereby lowering the LAL content. Thus, ultrasonic-aided pH-ST may be an operational technique toward minimizing LAL formation in RPI.

Impact of ultrasound processing on alternative protein systems: Protein extraction, nutritional effects and associated challenges

“…Moreover, these modifications transform the surface charge of the proteins, making them negatively charged and improving their water solubility [89] . However, high pH may also be detrimental to the quality of proteins, as alkaline extraction can lead to protein denaturation [90] , reduction in protein purity, darkening of colour [91] and formation of undesirable substances, such as lysinoalanine [92] . Few authors have reported the natural pH of around 6.8–7 to be the optimum pH for protein extraction from soy, peanut and the microalgae Arthrospira platensis [88] , [93] , [94] .…”

“… Sources US conditions Effects on nutritional properties and/or allergenicity Reference Kiwifruit proteins US probe Frequency: 20 kHz Power: 400 W Pulse: 50 % duty cycle Time: 0 to 16 min Immunoglobulin E binding capacity of allergen, Act d 2 decreased by 50 % and increased IVPD Wang, Wang [84] Potato proteins US assisted pH shifting treatment Protein dispersion: 20 mg/mL Triple frequencies: 20/28/40 and 20/40/60 kHz Dual frequencies: 20/28, 20/40, 20/60, 28/40, 40/60 kHz Mono frequencies: 20, 28, 40, 60 kHzIncorporation sequence of US: pre, post or online pH shifting (pHS) US time: 0, 2, 5, 10, 20, 30 min Pulse: ON 10 s/OFF 2 s Input energy density: 37.5 kJ/L Temperature: 40 °C Using online US/T40/pHS, the digestibility rate of protein increased during gastric and intestinal digestion Mao, Wu [113] Rapeseed protein isolates US Fixed frequencies: 20, 28, 35, 40, 50, 60 kHz Sweep frequencies: 20 ± 2, 28 ± 2, 35 ± 2, 40 ± 2, 50 ± 2, and 60 ± 2 kHz US times: 10, 20, 30, 40, 50 min US temperature: 25, 30, 35, 40,45 °C Power: 10, 20, 30, 40, 50 W/L Protein solutions:25 mg/mL Stirring of solution for 30 min at 25 °C, and adjusted to pH values (1.5, 2.5, 11.5, 12.5). Then, mixtures were subjected to sonication, then kept for 1 h at 25 °C), pH adjusted to 7 Reduction of lysinoalanine by 49.5 % and 74.1 %, following the use of US (28 kHz, 40 W/L, 40 °C, and 30 min) under alkali and acidic treatment, respectively Li, Zhang [92] Faba bean protein isolate US probe with 8 mm diameter Frequency: 20 kHz Protein dispersions: 10 g/L Relative protein digestibility showed a decrease of 3.6 % over control isolate Martínez-Velasco, Lobato-Calleros [115] Canola protein isolate US bath Frequency: 40 kHz Power: 130 W IVPD of US treated isolated did change significant respect to control Flores-Jiménez, Ulloa [114] …”

Multi-mode S-type ultrasound-assisted protein extraction from walnut dregs and in situ real-time process monitoring

“…The results of the Si-PLS model in different sub-intervals are displayed in Table 4 . The highest Rc value (0.9736) and the lowest RMSECV value (0.446) were found when the spectrum was divided into 21 intervals with the principal components of 9, suggesting that the Si-PLS model under the optimal combinations of intervals [2] , [4] , [9] , [15] was more relevant to the -SH content in the WP extraction process. The corresponding spectral ranges were 946.946–1018.601, 1103.101–1174.448, 1490.646–1561.283, and 1950.876–2020.772 nm ( Fig.…”

“…However, alkali-soluble extraction has some shortfalls, including large solvent consumption, low extraction efficiency, and high energy consumption [8] . Moreover, alkali extraction may cause lysinoalanin formation, resulting in potential toxicity and lower nutritional value in resultant proteins [6] , [9] . Therefore, exploring a green, safe, and cost-effective protein extraction technique is paramount to satisfying the needs for high extraction efficiency and environmental protection.…”

Plant Proteins for Future Foods: A Roadmap

“…By addressing their poor solubility problem and improving their techno-functionality, the combined treatment of pH shifting and sonication was also used to extend the application of plant-based proteins for the encapsulation of bioactive compounds. Most importantly, ultrasound can inhibit the formation of lysinoalanine during pH shifting [149].…”