Efficient Recovery of Biologically Active Substances from Currant Pomace—Pre-Drying Effects on Supercritical CO₂ Extracts

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

This manuscript describes the extraction of currant pomaces using supercritical CO2. Currant pomaces were valorised via supercritical CO₂ extraction to assess the impact of drying method (convective vs freeze-drying) and species (black vs red). Blackcurrant showed higher phenolic content, while freeze-dried redcurrant maximized antioxidant activity. Freeze-drying enhanced PUFA and altered tocopherol profiles. Pre-drying emerged as a key factor in tailoring lipid and antioxidant properties, guiding clean-label ingredient design and motivating further scale-up and yield-normalized studies.

 

This manuscript is well-written. But there are several points to be addressed.

 

Introduction should be divided into several paragraphs.

The reason of the difference between ALA and alpha-tocopherol of blackcurrant and redcurrant should be discussed with references.

 

Table6 standard deviation data is missing.

Conclusion is too long and should be restricted to data.

Author Response

Comments 1: Introduction should be divided into several paragraphs.

Response 1: The Introduction section has been divided into several paragraphs according to the reviewer's suggestion.

Comments 2: The reason of the difference between ALA and alpha-tocopherol of blackcurrant and redcurrant should be discussed with references.

Response 2: The reason for the differences between ALA and α-tocopherol contents in blackcurrant and redcurrant has been discussed in section 4 (Discussion), supported by relevant references.

Comments 3: Table6 standard deviation data is missing.

Response 3: Standard deviation values have been added to Table 6, along with the global homogeneous groups.

Comments 4: Conclusion is too long and should be restricted to data.

Response 4: The Conclusion section has been shortened and now focuses on the key data and main findings.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors

The manuscript presents a timely and relevant contribution to the circular bioeconomy by exploring the valorisation of berry pomace using green extraction technologies. The comparative study of pre-drying methods (convective vs. freeze-drying) under fixed supercritical CO₂ (SC-CO₂) conditions is both scientifically sound and industrially meaningful.

The manuscript shows clear strengths, including a well-defined hypothesis, robust experimental design, and the use of validated analytical methods (Folin–Ciocâlteu, DPPH, GC-FID, HPLC-FLD) with proper quality assurance. Statistical analyses are appropriate (Welch test, ANOVA with effect sizes, Holm adjustment), and the discussion effectively links microstructure, extraction efficiency, and functional outcomes. The study also offers practical relevance for clean-label and sustainable product development.

However, the absence of extraction yield and mass balance data limits process interpretation. Minor inconsistencies in reporting (e.g., drying endpoints, particle size, extraction time) and overinterpretation of DPPH results reduce clarity. The lack of tocopherol analysis in extracts also weakens functional conclusions. Overall, the work is promising but needs moderate revisions to enhance rigor, consistency, and interpretative depth.

SPECIFIC COMMENTS

The omission of extraction yield data (“Mass yields were not quantified,” line 169) represents a major limitation.
Without yield normalization, compositional differences may reflect concentration rather than recovery effects.
This issue should be acknowledged explicitly in the Discussion.
If possible, approximate yield data or normalization to dry pomace input should be provided.

Table 3 presents tocopherol means without standard deviations, contradicting the stated triplicate analysis.
Reported moisture contents (4–15%) are not clearly linked to pomace type or drying method.
Standard deviations should be added where missing.
Moisture data should be clarified for each treatment.

Drying duration and kinetics are not reported.
Particle size—an important factor in SC-CO₂ extraction—is omitted.
There is an inconsistency between extraction times stated in the Abstract (180 min) and Methods (120 min).
These parameters should be corrected or acknowledged as methodological limitations.

The claim of “maximised antioxidant performance” for R-6 overstates the significance of DPPH results.
This should be rephrased as “enhanced in vitro radical scavenging capacity.”
Assay limitations should be clearly acknowledged.

Tocopherols were measured only in residues rather than extracts.
This makes the inference about extraction efficiency indirect and potentially misleading.
Residue data should be presented as indicators of retention, not extract enrichment.
Links between residue tocopherol levels and DPPH results should be avoided.

Table 6 shows inconsistent notation for fatty acid data (e.g., “<0.1%” vs. numeric values).
Notation should be standardized (e.g., “<0.10” or “ND”).

The use of effect sizes and Holm corrections in statistical analysis is commendable.
However, table labels for homogeneous groups should specify whether comparisons were within species or across all samples.
This clarification should be added to the table footnotes.

Decision: Major Revision

 

Author Response

Comments 1: The omission of extraction yield data (“Mass yields were not quantified,” line 169) represents a major limitation. Without yield normalization, compositional differences may reflect concentration rather than recovery effects. This issue should be acknowledged explicitly in the Discussion. If possible, approximate yield data or normalization to dry pomace input should be provided.

Response 1: This issue has been explicitly addressed and discussed in the Discussion section.

Comments 2: Table 3 presents tocopherol means without standard deviations, contradicting the stated triplicate analysis. Reported moisture contents (4–15%) are not clearly linked to pomace type or drying method. Standard deviations should be added where missing. Moisture data should be clarified for each treatment.

Response 2: The table description has been revised to clarify the absence of standard deviation values. Moisture contents have been specified for each pomace fraction in Sections 2.2.2 and 2.2.3.

Comments 3: Drying duration and kinetics are not reported. Particle size—an important factor in SC-CO₂ extraction—is omitted. There is an inconsistency between extraction times stated in the Abstract (180 min) and Methods (120 min). These parameters should be corrected or acknowledged as methodological limitations.

Response 3: Drying parameters have been expanded for both drying methods in Sections 2.2.2 and 2.2.3. The sample grinding procedure prior to supercritical extraction has been clarified, and the correct extraction time has been updated consistently throughout the manuscript.

Comments 4: The claim of “maximised antioxidant performance” for R-6 overstates the significance of DPPH results. This should be rephrased as “enhanced in vitro radical scavenging capacity.” Assay limitations should be clearly acknowledged.

Response 4: The statement has been revised accordingly in the relevant sections of the text.

Comments 5: Tocopherols were measured only in residues rather than extracts. This makes the inference about extraction efficiency indirect and potentially misleading. Residue data should be presented as indicators of retention, not extract enrichment. Links between residue tocopherol levels and DPPH results should be avoided.

Response 5: The relevant text in the manuscript has been corrected to accurately reflect the interpretation of tocopherol data.

Comments 6: Table 6 shows inconsistent notation for fatty acid data (e.g., “<0.1%” vs. numeric values). Notation should be standardized (e.g., “<0.10” or “ND”).

Response 6: Fatty acid data and table descriptions have been standardised for consistent notation.

Comments 7: The use of effect sizes and Holm corrections in statistical analysis is commendable. However, table labels for homogeneous groups should specify whether comparisons were within species or across all samples. This clarification should be added to the table footnotes.

Response 7: Table footnotes have been revised to specify whether homogeneous group comparisons were made within species or across all samples.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

only minor English language improvements are needed to enhance readability (e.g., correction of “principal lover” → “principal lever” in the abstract, and a few grammatical refinements in the Results and Discussion sections). These are purely stylistic and do not affect scientific content.

 

Comments on the Quality of English Language

only minor English language improvements are needed to enhance readability (e.g., correction of “principal lover” → “principal lever” in the abstract, and a few grammatical refinements in the Results and Discussion sections). These are purely stylistic and do not affect scientific content.

 

Author Response

Language issues were corrected.