Barley «Hordeum vulgare L» protein: extraction, chemical composition and flavor interaction
Bibliographic record
Abstract
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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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".