Characterization of Postharvest Changes in Fruit Quality Traits of Highbush Blueberry (Vaccinium corymbosum L.) Cultivars

Comments 1:In the introduction and methods, the authors state that “This study investigated the dynamic changes in fruit color, texture, and quality attributes of blueberry cultivars during ….” Please specify clearly which quality attributes were measured.

Response 1: In the actual research work, we did observe and describe the qualitative traits of the fruits. However, during the paper writing process, we found that these qualitative traits could not be effectively incorporated into the subsequent comprehensive evaluation, nor was there a suitable method to quantify and assess them. Therefore, we excluded these qualitative traits from the final research analysis, but failed to simultaneously delete their descriptions in the text. In light of this and considering that the study did not actually involve these traits, we have now removed the descriptions of the qualitative traits from the manuscript. Thank you for your reminder.

Comments 2: Lines 11–13: The phrase “(Note: hardness represents firmness and is an indicator in the Brookfield’s texture analyzer)” should be removed; only the round brackets should remain.

Response 2: Agree.We have revised it in Line 11.

Comments 3:Line 19: The abbreviation “ΔE” should either be explained in detail at first mention or replaced with a more descriptive term.

Response 3:Agree.We have revised it in Section 2.3.1 ‘Colorimetric Analysis’.

Comments 4:The rationale for selecting only 10 fruits per cultivar should be clarified. On what basis was this sample size determined, and how does it reflect the variability within each cultivar?

Response 4:Thank you for raising the valuable question regarding the selection of "10 fruits per cultivar per group"—this inquiry indeed provides an important perspective for us to further clarify the rationality of our experimental design.

Selecting 10 fruits per cultivar with 3 replicates in this study was a careful choice based on the practical context of the research and the requirement for data reliability. From the common practice of small berry phenotypic research in horticulture and pomology, a sample size of 10 fruits per group combined with 3 replicates (resulting in a total of 30 independent fruit samples per cultivar) can initially cover the main phenotypic variation range of fruit development within a single cultivar. When combined with subsequent analysis of variance (ANOVA), this design may to a certain extent reduce random errors caused by individual fruit heterogeneity, and basically meet the data representativeness requirements for the core objective of this study, which is "comparing the cold storage adaptability differences among multiple cultivars".

Meanwhile, considering that a relatively large number of cultivars are involved in this study, further increasing the number of fruits per group might lead to a significant rise in sample processing workload. This could not only extend the experimental cycle but also potentially introduce additional systematic errors due to differences in operation batches. Therefore, this design is not the only optimal solution, it achieves a good balance between data rationality and experimental feasibility when considering the research scope, the characteristics of the measured indicators (such as easily quantifiable traits like fruit decay rate and weight loss rate), and the actual operational conditions of our research team, and thus initially provides a basis for supporting the research conclusions.

Comments 5:Line 89: Please use the Microsoft Equation Tool to properly format the formula.

Response 5:We have revised it

Comments 6: The manuscript does not provide information about the growing conditions of the fruits. Furthermore, the fruits were collected from only one growing season, which considerably limits the scientific robustness of the study.

Response 6:Thank you.Firstly, the blueberry fruits tested in this study were cultivated in a standardized solar greenhouse, rather than in open fields or simple plastic greenhouses. The greenhouse was equipped with an intelligent environmental control system and an integrated water and fertilizer drip irrigation system, which enabled precise regulation of temperature and relative humidity. This effectively avoided the interference of natural variables (such as rainfall, extreme temperatures, and uneven soil fertility) on fruit quality in open-field or plastic greenhouse cultivation, ensuring highly consistent growth conditions for all tested fruits. In addition, the author has obtained the harvest quality data of the same cultivars in 2023. A comparison with the 2024 data showed minimal quality differences among cultivars between the two years, which further confirms the stability of fruit quality under solar greenhouse conditions. Secondly, regarding the limitation of "data only coming from one growing season" mentioned by the reviewers, it should be noted that the core objective of this study is to explore the short-term regulatory effect of 4°C refrigerator cold storage on the postharvest quality of blueberries. Although the author has relevant data from other growing seasons, they were not included in the analysis of this paper due to their weak correlation with the 4°C cold storage treatment of the 2024 postharvest fruits. Meanwhile, the author acknowledges that data and treatments from a single growing season cannot fully cover the potential impacts of inter-annual climatic differences (e.g., temperature difference, precipitation) on fruit quality. However, in this study, the limitations of single-season data have been mitigated by maximizing the control of variables in the same growth environment and having all fruits harvested by the same person. Subsequent in-depth studies will further conduct cross-annual verification to systematically analyze the stability of treatment effects. The conclusions drawn in this study are consistent with the established research objectives and scientific question orientation.

Comments 7:The manuscript contains numerous errors, such as missing spaces between text and units in the tables, as well as inconsistent use of upper- and lowercase letters. These issues should be carefully corrected throughout the text.

Response 7:Thank you for your reminder. The formatting issues in the manuscript, such as missing spaces and inconsistent use of uppercase and lowercase letters, have been carefully checked and corrected throughout the entire article.

Comments 8:The description of statistical analysis is insufficient. The authors should clearly indicate which statistical tests were applied to the data.

Response 8:

Thank you. Specific details including the data analysis methods, post hoc test procedures, and relevant parameter settings have been supplemented in Section 2.4 " Statistical Analysis".

Comments 9:The correlation analysis does not provide novel insights. The reported correlations appear to be obvious and do not strengthen the scientific contribution of the study.

Response 9:Thank you. Specific details including the data analysis methods, post hoc test procedures, and relevant parameter settings have been supplemented in Section 2.4 " Statistical Analysis".

Comments 10:The correlation analysis does not provide novel insights. The reported correlations appear to be obvious and do not strengthen the scientific contribution of the study.

The authors report only average values across all cultivars, without presenting results for each cultivar at different storage times. These cultivar-specific data should be included, at least in the appendix.

Response 10: Thank you. 1.Regarding trait correlations among multiple cultivars: This study involves a large number of blueberry cultivars. During the analysis, we found that the correlations between some specific traits were difficult to identify. We attempted to explore the associations through methods such as classification analysis, but no significant results were obtained. In future research, we plan to further increase the sample size or the number of cultivars to more systematically explore the potential correlations between traits.

2.Regarding the method of result presentation: Only the average values of each cultivar are reported in the manuscript, mainly because they can more clearly reflect the overall variation trend and fluctuation characteristics of all cultivars. For the specific results of individual cultivars, only a few core traits were focused on for unified analysis. In addition, for other indicators (some of which are relatively uncommon) measured by the texture analyzer except for hardness, no statistically significant regular results were found among the cultivars. To ensure the rigor of the research conclusions, the data of these indicators were not included in the manuscript.

Comments 11:The manuscript does not adequately discuss the practical and scientific significance of the findings. The authors should elaborate on the relevance and potential applications of their results.

The claim that “Scar size, fruit shape index, and springiness were validated as key predictors of shelf-life hardness dynamics, providing actionable metrics for cultivar selection and postharvest management” requires stronger justification. Please provide evidence or references to support this conclusion.

Response 11: Thank you. We hereby provide a unified response as follows:In this revision, we have supplemented the discussion section of the manuscript with two aspects of content: first, we have conducted more detailed analysis and discussion on the changes in fruit hardness. Second, we have added relevant discussions on the potential reference value of fruit stem scar traits for fruit quality evaluation, aiming to further enrich the depth and completeness of the discussion.

Comments 12:In the conclusions, the statement “Color stability (ΔE < 3.5) was maintained only by ‘Legacy’ throughout the 15 days” is made. However, the manuscript does not clearly present the data supporting this claim. Please indicate where this is shown.

Response 12: The cultivar code of Legacy in the manuscript is 21. As shown in Table 5, this cultivar 21 had a total color difference (ΔE) of less than 3.5 in four storage periods: 0–5 days, 0–10 days, 0–15 days, and 5–10 days, leading to the conclusion that it had the best color stability. In addition, in the principal component analysis results in Section 3.5 PCA, Legacy (cultivar 21) ranked 6th, which also represents a relatively good performance.

Comments 1:The introduction briefly addresses the importance of postharvest quality but lacks deeper context regarding global blueberry trade, consumer preferences, and economic relevance. Authors must expand the background to include market trends and consumer expectations for blueberry shelf-life.

Prior studies are cited, yet there is minimal critical comparison or identification of research gaps that this study intends to fill. A more robust literature review to position the study within existing research and highlight its novelty should be included.

Response 1: The introduction section has been comprehensively revised, with supplementary information including the global trade status of blueberries, consumer preference characteristics, and the latest research progress in blueberry storage added.We have revised it in Section ‘1.Introduction’.

Comments 2: The cultivars listed are not identified as southern or northern highbush types, despite these classifications being referenced later in the manuscript. Explicitly classify each cultivar in Section 2.1 to ensure consistency and aid interpretation.

Response 2: We have made the revisions in Table 1.

Comments 3Lines 29–82 require revision for clarity and readability.

The texture analyzer and colorimeter are redundantly described in multiple sections. Consolidate instrument descriptions and refer back to them where needed to reduce repetition.

Response 3:Thank you. We have made the revisions.

Comments 4:Section 2.2 mentions 10 berries per replicate, while Section 2.3 specifies 5 fruits for texture analysis. Provide a unified statement clarifying replication strategy across all traits to enhance transparency and statistical robustness.

Response 4:We apologize for the oversight and hereby supplement the experimental design details: for each treatment combination of all blueberry cultivars in this study, 3 replicates were set, with 10 fruits included in each replicate. Relevant errors in the manuscript have been corrected.

Comments 5: 2.4.“Office 2021” is vague and lacks specificity. Clearly state which software tools were used (e.g., Excel for data collation, SPSS for ANOVA, Origin for plotting) to support analytical rigor and reproducibility.

Response 5: We have revised it.Thank you. Specific details including the data analysis methods, post-hoc test procedures, and relevant parameter settings have been supplemented in Section 2.4‘Statistical Analysis’

Comments 6: Tables 3 and 4 lack explanations for superscript letters used to denote statistical significance. Include legends beneath each table clarifying the meaning of these annotations.

Response 6:We have made the revisions in Tables 3 and 4.

Comments 7:Table 4, which contains L*, a*, b* values, is currently misplaced. Move Table 4 to Section 3.2 to align data presentation with the discussion on color changes and ΔE calculations, improving narrative flow and reducing cognitive load.

Response 7:We have revised it in Section 3.2‘Color Evaluation During Blueberry Postharvest period’.

Comments 8:Figures 1 and 2 are scientifically valid but suffer from poor readability due to small font sizes and dense layout. Increase font size for axis labels, legends, and statistical annotations and consider separating subplots into individual panels or using clearer color coding. Ensure abbreviations are spelled out or consistently defined in captions.

Response 8:We have made the revisions in the Figures 1 and 2 .

Comments 9:3.5 PCA results are presented in tabular format, which may limit interpretability. Incorporate graphical representations such as biplots or score plots to visually convey sample clustering and variable contributions.

Response 9:Thank you for raising this question. We previously attempted to present the relevant results using biplots or score plots; however, due to the large number of fruit cultivars and the complexity of the measured indicators involved in this study, the generated figures tended to suffer from information overlap and visual clutter, resulting in a suboptimal presentation effect. In contrast, although tables are slightly less intuitive than figures, they can display multi-dimensional data more clearly and neatly, avoiding information interference. Therefore, we ultimately chose to present the results in tabular form.

Comments 10:Some correlations (e.g., scar size vs. hardness) are mentioned but not thoroughly explored.

The discussion lacks connection to commercial priorities such as export viability and consumer satisfaction.

Language is occasionally vague, e.g., “significant changes were observed” without specifying direction or magnitude.

Deepen analysis of observed correlations and relate findings to market-relevant traits (e.g., firmness for transport, color for appeal).

Physiological interpretations should be strengthened with additional references, particularly regarding texture and pigment changes.

Response 10: Thank you very much for your valuable suggestions. Regarding the questions you raised in the discussion, we hereby provide a unified response as follows:

About ‘Language is occasionally vague, e.g., “significant changes were observed” without specifying direction or magnitude.’,The descriptions of inter-group differences in the manuscript have been uniformly revised to "significantly increased" or "significantly decreased".

On the feasibility of blueberry export: At present, China is a major blueberry consumer, with the market mainly focusing on domestic consumption. Relevant research on blueberry import is relatively extensive, so the feasibility of export has not been discussed in this study for the time being.

On consumer satisfaction: The methodological framework of this study is mainly constructed from the research perspectives of growers and researchers. For ordinary consumers, the color of blueberries can serve as a reference for purchase. However, consumers usually do not conduct numerical measurements of indicators such as color and texture after consuming blueberries, but rather make judgments through intuitive feelings. Therefore, the research focus is not on the consumer side, but on meeting the practical needs of growers, sellers, and researchers.

On physiological explanations: This is a direction that this study plans to explore in the future. Since this study only focuses on the phenotypic traits of blueberries and does not determine physiological and biochemical indicators, no discussion on this part has been conducted. In the future, we intend to conduct in-depth research on the relationship between fruit texture, color and blueberry quality as well as storability, and further supplement the mechanism analysis at the physiological and biochemical levels.

Comments 11:The conclusion summarizes findings but does not offer strategic recommendations or acknowledge study limitations.

Authors must include actionable insights for breeders, growers, and distributors and explicitly state limitations (e.g., single location, absence of sensory data) of the research.

Authors should propose targeted future research directions, such as identifying genetic markers for texture retention.

Response 11: Thank you. The conclusion section should supplement insights for industrial stakeholders (including breeders and growers), as well as research limitations and future directions; we have accordingly completed the corresponding supplements and revisions in the conclusion section to address this feedback.

Comments 1:In the key words: The keywords and the title are used in combination in search engines. To increase visibility of your article in different search platforms please replace blueberry with Vaccinium corymbosum L., fruit quality traits with sensory attributes, postharvest with shelf-life, fruit colour with visual quality and fruit texture with rheological properties.

Response 1: Thank you.We have revised it in ‘Keywords’. Thank you for your reminder.

Comments 2: The introduction justifies the research gap however, you may further strengthen the introduction with figures of % postharvest losses in blueberries or losses during shelf period if possible.

Response 2: The introduction section has been comprehensively revised, with supplementary information including the global trade status of blueberries, consumer preference characteristics, and the latest research progress in blueberry storage added.We have revised it in Section 1 Introduction.

Comments 3:Line 61-Please describe the conditions maintained at different greenhouses (temperature/ RH/ light/fertiliser application/ irrigation etc) if they are different or state whether similar conditions were maintained in all greenhouses.

Response 3:Thank you for your valuable comments. All greenhouses in this study are located in the same demonstration park and adopt a standardized cultivation and management model. The technical parameters and operation procedures of environmental regulation (temperature, humidity, light) and water-fertilizer application are completely consistent across all greenhouses, with no inter-greenhouse differences. Therefore, a clear statement[The greenhouses are located within the small berry demonstration area, equipped with integrated water and fertilizer machines, and operated under the same management mode.]is added in the Line 134 to 135, and the bases for relevant core parameters (temperature, humidity, light, and fertilization formula) have been retained. However, contents such as "labor cost saving" and "fertilizer use efficiency improvement" belong to the category of technical benefits, which are irrelevant to the description of experimental conditions and thus not elaborated in detail in the manuscript.

Blueberries have distinct requirements for temperature, light, and humidity across different growth stages, which necessitates precise stage-specific regulation:

1.Temperature

    Dormant Stage (until late November): Maintain a temperature of 0-7.2℃ and implement light-shielding treatment.

    Bud Break Stage: Keep the temperature at 25-28℃ during the day and>7℃ at night; provide full sunlight with a relative humidity of 50-70%.

    Spike Expansion Stage-Flowering Stage: Maintain the temperature at 22–25℃ during the day and ≥8℃ at night; provide full sunlight with a relative humidity ≤50%.

    Fruit Set Stage – Fruit Enlargement Stage: Keep the temperature at 25–27℃ (≤28℃) during the day and 10–13℃ (≤15℃) at night; provide full sunlight.

Fruit Ripening Stage – Harvest Stage: Maintain the temperature at 25–28℃ (≤30℃) during the day and ≤15℃ at night, and increase the temperature difference.

2.Light management is adjusted according to temperature conditions, with natural light used exclusively and no additional light supplement measures applied.

3.Water-Fertilizer Management

The water and fertilizer management for blueberries should be conducted scientifically in conjunction with their growth cycle. From August to September annually, the focus is on applying base fertilizer in autumn, with organic fertilizers such as cattle and sheep manure preferred. This lays a solid foundation for the plants to overwinter and grow in the following year. In daily maintenance, foliar fertilizers are sprayed during key growth stages to supplement nutrients. For water management, the soil should be kept moist, with watering conducted every 5-7 days generally. In case of prolonged drought, additional water should be supplied promptly to ensure sufficient moisture.

Comments 4:Lines 68-69- Please describe how the blueberries were stored under refrigeration (e.g. small cardboard boxes/ trays/ etc).

Response 4 :Blueberries are stored in a refrigerator at 4 °C, packed in small plastic containers of 125 grams.

Comments 5:Line 61 remove the word “cultivated” (or grown- as both have same meaning)

Response 5:We have revised it. 

Comments 6:Line 68 replace “measurement” with measurements

Response 6:We have revised it .

Comments 7:Line 80-81“and for each replicate” was repeated

Response7 :We have revised it.

Comments 8:In the introduction, the significance of this study was justified by relating it to the inability of using storage techniques such as MAP universally due to differences in fruit characteristics of different blueberry cultivars. Therefore, it is better if you could relate the findings to different storage techniques such as MAP, refrigeration etc. E.g. which cluster would be most suitable for MAP etc. If there were any differences in growing conditions (temperature/ RH etc) in different greenhouses, the differences observed in the study could be related to those in addition to varietal differences.

Response 8:Thank you very much for your valuable comments. After discussion within our team, we further clarify that the core of this study focuses on the quality performance of blueberries at the post-harvest and harvest stages, with emphasis on analyzing the quality change pattern under a single conventional low-temperature storage condition (all treatments were conducted at the same refrigeration temperature).

Since storage and transportation technologies such as modified atmosphere packaging (MAP) were not involved in the study design, relevant contents were not elaborated on in the discussion section. We also recognize that "focusing only on a single storage condition" is a limitation of this study. Therefore, we have supplemented this point in the section 5.conclusion and provided an outlook on future research directions.

Comments 9:Line 245-246- Please correct spellings of fruit transverse diameter (r in the word diameter is missing).

Response 9:Thank you .We have revised it in Line.

Comments 1:The authors have adequately addressed the corrections in the manuscript. Nevertheless, the text should be carefully reviewed once more to ensure consistency, for instance in the notation of 'p-value', which should be written with a lowercase 'p' throughout the manuscript.

Response 1: .We have revised it. Thank you for your reminder.

Comments 1:Thank you for the clarifications and revisions. I encourage the authors to consider expanding the discussion of observed correlations and their physiological underpinnings, even if speculative, to enhance the interpretive value. Additionally, while the study is rightly focused on domestic priorities, brief contextualization of traits relevant to broader markets could increase its utility for international stakeholders.

Response 1: Thank you for the valuable comments from the reviewers. We have supplemented in the manuscript the speculation on the observed correlations, as well as the phenotypic traits of different blueberry cultivars and the physiological mechanisms underlying their postharvest phenotypic differences. Meanwhile, we added the trends in blueberry quality grading in the international market to enhance the global reference value of this study. In addition, we have also discussed the above-mentioned speculative correlations.We have revised it in line 363 to 366,425 to 441.