An investigation of effects of microwave treatment on the structure, enzymatic hydrolysis and nutraceutical properties of Ã-lactoglobulin
Notice bibliographique
Résumé
Whey proteins are used extensively by the food industry in such products as infant formulas and dietetic and health foods owing to the high nutritional value and useful functional properties of these milk-derived proteins. In addition, in recent years, the nutraceutical properties of native or predigested whey proteins have become the focus of much research. Both the functional and nutraceutical properties of whey proteins can be enhanced by exposing them to various non-denaturing physicochemical conditions that modify their native structure. It is within this context that the present investigation of the effects of microwave treatments (MW) on the structure, degree of enzymatic hydrolysis, and nutraceutical properties of beta-lactoglobulin (β-Lg), the predominant whey protein in cow's milk, was undertaken. Microwave treatment of β-Lg in D2O solution under various conditions was monitored by Fourier transform mid infrared (mid-FTIR) spectroscopy. At sub-ambient and ambient temperatures, no microwave-induced changes in the conformation of the protein were detected. Microwave heating of the beta-Lg solutions to temperatures in the range of 40-60 ºC resulted in a marked increase in the rate of hydrogen-deuterium (H-D) exchange by comparison with conventional heating (CH) at the same temperature. At heating temperatures in the range of 70-90 ºC, the microwave-heated solutions exhibited more extensive protein aggregation than conventionally heated solutions. Application of two-dimensional (2D) correlation analysis to the Fourier self-deconvolved FTIR spectra recorded as a function of number of cycles of microwave or conventional heating revealed that the unfolding pathway of β-Lg was different in these two temperature ranges but was not altered by microwave heating as compared to conventional heating. Kinetic analysis of the FTIR data revealed that the accelerated rate of protein unfolding observed in microwave-heated samples is attributable to a lower energy of activation and supported the existence of non-thermal effects of microwaves. Circular dichroism (CD), fluorescence spectroscopy, and 2D 1H NMR spectroscopy were used to confirm and complement the results obtained by FTIR spectroscopy. The effects of microwave and conventional heat treatments at three temperatures (40, 60, and 90 °C) on the enzymatic hydrolysis of β-Lg and on the peptide profiles of the hydrolysates were also investigated. The degree of hydrolysis of β-Lg by pepsin, trypsin and chymotrypsin as well as in a two-stage hydrolysis with pepsin followed by trypsin and chymotrypsin, simulating gastrointestinal conditions, was determined. Microwave-treated samples exhibited more extensive enzymatic hydrolysis than conventionally heated samples under all hydrolysis conditions, with the greatest degree of hydrolysis being found following microwave treatment at 60 °C, and hydrolysates of microwave-treated β-Lg exhibited both enhanced angiotensin-converting enzyme (ACE) inhibition and enhanced antioxidant activity. LC-ESI-MS and MS/MS in conjunction with the use of advanced bioinformatics software were employed in the identification of the peptide profiles of the hydrolysates and revealed the presence of unique peptides in hydrolysates of microwave-treated samples, suggesting that the microwave treatment may have exposed new cleavage sites within the interior of the protein. Overall, the findings of these studies indicate that microwave heat treatments may be an attractive approach to enhance the nutraceutical properties of whey and other proteins.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».