Barley «Hordeum vulgare L» protein: extraction, chemical composition and flavor interaction
Notice bibliographique
Résumé
Barley (Hordeum vulgare L.) protein extracts were prepared from defatted barley flour using different techniques.Firstly, two conventional alkaline extraction methods were applied: (i) a simple alkaline extraction using 0.5M NaOH (pH 11.0) to break-open cell walls with subsequent release of the protein, and (ii) a sequential alkaline extraction method where the simple alkaline treatment was followed by an isoelectric precipitation (IEP) step.Secondly, milder enzymatic treatments to minimize protein breakdown during extraction were investigated.These included:(i) a bi-enzymatic method involving starch removal using α-amylases from Bacillus spp.and amyloglucosidase from Aspergillus niger, (ii) a tri-enzymatic sequential method using the former bi-enzymatic treatment followed by digestion with -(1,3)/(1,4)-glucanase from Trichoderma longibrachiatum, and (iii) a tri-enzymatic sequential treatment combining the latter tri-enzymatic digestion followed by IEP.Results of the study showed that both alkaline extraction methods gave similar protein recovery yields regardless of whether or not the IEP step was performed.However, the combination of IEP with alkaline method improved the protein content, increasing from 33.0% to 68.9%, which in both cases comprised mainly low molecular weight fractions.Extracts produced by the bienzymatic treatment had the highest protein content (49.0%) among enzymatic extractions, while those obtained by the tri-enzymatic treatment followed by an IEP step led to the highest protein recovery yield (78.3%), with 35 kDa B-hordeins being the major constitutive proteins of both extracts.Further characterization of the extracted barley proteins indicated that they exhibit pseudoplastic behavior, as revealed by functionality testing, and form stable emulsions.In addition, their highest foaming capacities (FC) and foaming stabilities (FS) were recorded at pH 3.0 and 8.0, respectively.The protein-flavorant interactions between barley proteins and the model flavor compound vanillin (4-hydroxy-3-methoxybenzaldehyde) were assessed by two methods: (i) measurement of the proportion of unbound vanillin upon incubation with barley protein extracts at different temperatures for up to 72 hrs followed by quantification of binding affinity (number of binding sites n; dissociation constant Kd; equilibrium constant K) by Klotz plot, and (ii) characterization of the protein-vanillin complexes by fluorescence spectrophotometry analysis.The interaction III between vanillin and the barley proteins was defined as non-cooperative, as evidenced by the Klotz plot linearity.As well, increased vanillin concentrations paralleled an increase in quenching of the protein-vanillin complex fluorescence, indicating changes in the hydrophobicity sites of proteins upon their complexation with vanillin.The effects of heat-and high pressure-treatments of the proteins on their level of interaction with the flavor compound were also evaluated and compared to those of whey protein isolate (WPI) and pea protein concentrate (PPC) used as controls.Consistent with the results generated from the Klotz analysis, the lowest degree of vanillin binding for control proteins was seen with native whey protein; among barley proteins, the alkaline extract treated with high pressure showed the least interaction.Fluorescence spectroscopy analysis revealed that the interaction of vanillin was weakest with heat-treated pea protein, followed by heat-treated whey protein.Lastly, commercial WPI and PPC were incorporated into a high protein (30%) cookies, formulated with different concentrations of vanillin.Sensory analysis of the cookies was conducted by a panel of 70 untrained panelists targeting three attributes using a 9point hedonic scale for mean intensity scores.Cookies formulated with PPC at a flavor:protein weight ratio (WR) of 0.45 and those formulated with WPI at a WR of 0.74 received the highest scores, while the highest vanillin intensity was perceived at a WR of 0.74 for WPI and 0.59 for PPC.IV
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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) | 0,001 | 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 ».