Stability of Vitamin C Content in Plant and Vegetable Juices under Different Storing Conditions

Round 1

Reviewer 1 Report

The manuscript submitted by Feszterová and collaborators deals with a very interesting topic. However, its structure and writing need to be thoroughly revised. 

The abstract is not explicit regarding the main objectives of the work, as well as the matrices used and the main results obtained. Authors should consult the guidelines for submission, in order to correctly adapt its content.

The introduction is excessively large, confusing, repetitive, and incoherent. The topics are not properly linked, there is no nexus of ideas or line of connection between them. In addition, the last paragraph is too long and should only refer to the main objective of the work developed and how it solves the problem.

Materials and methods are equally confusing. This section should allow the readers of the manuscript to repeat the procedures used. For example, section 2.1.1. seems more like an introduction than a description of the methodology used.

The results should also be revised. No proper statistical treatment is given, and it is really difficult to follow what they intend to convey with the data obtained. 

The authors refer to 141 bibliographical references, which seems to me an exaggeration, most of them being more than 10 years old. 

Based on all these points, I consider that the manuscript does not present sufficient scientific quality for publication in Applied Sciences.

The manuscript is written in a rather confusing way, without proper connection of ideas and themes. Although the English is understandable, the clarity and coherence as well as the flow of the content should be reviewed.

Author Response

Dear Reviewer,

We would like to thank you for your careful reading of our manuscript (ID: applsci-2483139) entitled “New insights into the shelf life of vitamin C in plant and vegetable juices stored under different time, temperature, packaging conditions”. We appreciate your comments and constructive recommendations, which have contributed to the improvement of our manuscript. Here, we present separate answers to your comments. We also send the modified file via the online submission process.

Best Regards,

Małgorzata Kowalska,

Melania Feszterova,

Reviewer’s comments:

The manuscript submitted by Feszterová and collaborators deals with a very interesting topic. However, its structure and writing need to be thoroughly revised.

Response to Reviewer

The abstract is not explicit regarding the main objectives of the work, as well as the matrices used and the main results obtained. Authors should consult the guidelines for submission, in order to correctly adapt its content.

Answer 1: We have modified the Abstract of this paper as follows:

The effect of environmental variables on vitamin C degradation in the analysed plant and vegetable juice samples was investigated. The study focused on samples from chives, dandelion and nettle, as well as tomato, carrot, cucumber, red and white pepper and cabbage. The work aims were to summarise the impact of storage time, temperature, and packaging materials on antioxidants (using vitamin C as an example) in processing plant and vegetable juices. The vitamin C concentration was tested iodometrically at 0 to 21 days intervals. Storage was carried out at different temperatures (4 °C, 23 °C, -18 °C) and in selected two packaging materials (glass and plastic). The analyses showed that low temperatures (t = 4 °C) and storage in glass containers are best for preserving vitamin C content. Storage time influenced the decrease in vitamin C values, with higher losses with longer storage. Plastic containers had a shorter shelf life for vitamin C compared to glass containers. In general, high temperatures during processing and storage have had a negative effect on the preservation of vitamin C. Therefore, storing juices in refrigerator and glass containers intended for food applications to minimise vitamin C degradation is important.

2.The introduction is excessively large, confusing, repetitive, and incoherent. The topics are not properly linked, there is no nexus of ideas or line of connection between them. In addition, the last paragraph is too long and should only refer to the main objective of the work developed and how it solves the problem.

Answer 2: We have modified the Introduction and last paragraph as follows:

Plant and vegetable juices are rich sources of vitamin C and have significant nutritional value of vitamin C for humans [1] because humans are unable to produce vitamin C on their own [2−4]. While synthetic vitamin C is chemically equivalent to vitamin C generated from plants, fruits, and vegetables [5], they also include a variety of micronutrients and phytochemicals that may impact the vitamin’s bioavailability [6]. The therapeutic abilities of plants and vegetables include protection of the body against various diseases [7−10].

Vitamin C has important nutritional benefits for human health [11], e.g., including antioxidant and cellular protection from oxidative damage [12−13], strengthening the immune system [14−15], collagen synthesis for skin and tissue health, and improving iron absorption [16−17].

Abundant sources of vitamin C are peppers, tomatoes and green leafy vegetables [18]. When consuming plant and vegetable juices, pay attention to the freshness and proper storage to minimise vitamin C stratification and degradation [19−21]. For centuries, most vegetables and fruit have been handled, allowing for year-round enjoyment of the products made from the harvest. According to Mieszczakowska-Frąc, Celejewska, and Płocharski [14] found, that fruit and vegetables can be kept fresh for many months thanks to advanced techniques for storage. Storage should be in dark or light-proof containers at the correct temperature, and juices should be consumed as soon as possible after opening to preserve the highest vitamin C content. Even though treatment is an excellent method to extend the duration of storage, it is nevertheless associated with significant degradation of several substances that have positive health effects, such as vitamin C, which rapidly degrades in the treatment process [14].

Packaging and packaging materials in the food industry play an important role in protecting products from damage and spoilage [22−23]. Different types of materials, such as plastic bottles and glass bottles, are used in fruit juice packaging [23]. Packaging characteristics and storage conditions affect the quality of juice products [22,24−25].

Overall, it is important to pay attention to a healthy diet with sufficient vitamin C intake from fresh vegetables and plants to ensure optimal health and the immune system. Consumers are becoming increasingly concerned about the number of vegetables they consume each day due to the development of a healthy diet. Additionally, the desire for pre- or half-prepared meals in today’s fast-paced world contributes to a significant rise in the consumption of vegetables. Many fruit and vegetable varieties are offered for a brief period right after production [14,26]. The key elements that affect vitamin C concentration are the type of container (glass or plastic) and the way in which juices from different plants and vegetables are stored [27−30]. The prevalence of current nutritional trends and customers’ expectations of products with high vitamin content and/or antioxidant value has generated interest in exploring new effective methods of storage. Research has focused on the stability of vitamin C while highlighting the importance of choosing the appropriate packaging material (glass, plastic) for storing high concentrations of vitamin C in stored juices. Plant sources and organic vegetables have a significant impact on customers´ health. It is crucial to comprehend how to keep juices effectively from the perspectives of producers and customers to guarantee that our bodies obtain the appropriate daily dose of vitamin C.

The study investigated the relationships between storage factors and vitamin C concentration in selected juices from plants (chives, dandelion, nettle) and vegetables (tomato, carrot, cucumber, cucumber salad, red and white pepper, white cabbage). The effect of temperature, length of storage and packaging material on the decrease in vitamin C concentration was investigated. Three ordinary storage temperatures and two packaging materials were considered to achieve the highest possible concentration of the vitamin. The findings are of relevance not only to consumers but also to the industry. They are of fundamental importance for these juices and the range of other perishable plants and vegetables, their transport and use.

3. Materials and methods are equally confusing. This section should allow the readers of the manuscript to repeat the procedures used. For example, section 2.1.1. seems more like an introduction than a description of the methodology used.

Answer 3: Based on the above comment, we have modified the text of this paper as follows:

- In section 2.1 Materials, the chemicals used in the iodometric titration have been added.

- The text in subsection 2.1.1 Characteristics of chosen plants and vegetables has been shortened, and the text has been separated into two sections (1. Introduction and 2.2 Methods). A general description of selected plant and vegetable material has been added to section 1. Introduction. We have included specific sections of text that explain the handling of individual plants and vegetables as well as the preparation of their juices, located in section 2.2 Methods (subsection 2.2.1 Preparing plant and vegetable juices).

4. The results should also be revised. No proper statistical treatment is given, and it is really difficult to follow what they intend to convey with the data obtained.

Answer 4: Based on the above comment, we revised  the results and we add an explanation to the data obtained.

The study's findings were reported as a mean and standard deviation. We were able to learn about the results' variability and mean value thanks to this presentation technique. Each statistical analysis was carried out at least three times, ensuring the repeatability and dependability of the outcomes. It was possible to determine whether the outcomes were consistent and representative by repeating statistical data. Our analyses were tailored to the unique characteristics of the research thanks to the method employed to identify the observed results acquired from the various types of plants and vegetable juices. The degree of reliance between the variables that were observed—temperature, storage conditions, and plant and vegetable samples—was assessed using Spearman's correlation coefficient. This correlation coefficient was used to determine whether and to what extent these variables are related.

Generally speaking, our statistical analysis involved presenting the results as mean and standard deviation, repeating the analyses to ensure reliability, using a method to separate the results from various samples of plant and vegetable juices, determining the relationships between variables using Spearman's correlation coefficient, and using statistical software for the analysis.

5. The authors refer to 141 bibliographical references, which seems to me an exaggeration, most of them being more than 10 years old.

Answer 5: We have cut back on the number of bibliographical references based on the afore mentioned feedback, just for the last 10 years.

6.The manuscript is written in a rather confusing way, without proper connection of ideas and themes. Although the English is understandable, the clarity and coherence as well as the flow of the content should be reviewed.

Answer 6: Based on the above comment, we have corrected the text of the paper to integrate the ideas and themes as well as the clarity and flow of the content.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled „New insights into the shelf life of vitamin C in plant and vegetable juices stored under different time, temperature, packaging conditions“ presents the study of vitamin C content in selected plant and vegetable juices, kept under different temperatures, in glass and plastic containers in different times of storage, determined by iodometric titration. The effect of different storing conditions are compared and statistically analyzed. The topic is interesting, and the results could be useful in the juice production industry.

General concept comments:

The manuscript is written extensively, some parts of text are confusing and difficult to understand, and some parts could be shortened. All comments are listed below:

The Title of the manuscript is misleading because the results of the study do not point out the shelf life of the juices (the length of time for which an item remains usable, fit for consumption, or saleable according to dictionary) but rather deal with the content of vitamin C under different storing conditions. The method used and the conclusion of the statistical analysis of the results should be briefly mentioned in Abstract of the manuscript.

The Materials and Methods section should be significantly shortened or rewritten more concisely. In section 2.1. Materials, the chemicals used in iodometric titration should be listed. Description of plants and vegetables in section 2.1.1. is useful but too extensive for this section. My suggestion is to move the general description of the selected plant and vegetable material in Introduction section, and to put the specific parts of the text that explain the handling of each plant or vegetable material in 2.2. Methods section (for example, lines 239 – 244 that describe plant material handling, and lines 249 – 252 that describe juice preparation). Figure 1 also belongs to the Methods section rather than the Materials section. The subtitles in Methods (lines 265 and 277) are not necessary. Some sentences are in excess or unnecessary for this section (for example line 286 – 288, 307 – 309).

Specific comments:

Lines 39 - 40. The meaning of the sentence is unclear. Please rephrase.

Lines 98 – 101. The meaning of the sentence is unclear. Please rephrase.

Line 335 – words “caused by” are in surplus.

Lines 361 – 363. The meaning of the sentence is unclear. Please rephrase.

Lines 400 – 401. The abbreviation MAP isn’t explained, sentence is unclear.

Line 415 – cited concentration of vitamin C seems wrongly written, please check this out.

Line 416 – please clarify the meaning of the phrase “double axial”.

Lines 489 – 491. The sentence is cumbersome and difficult to understand.

Lines 507 – 508. Wrong measurement units on concentration values.

Table 1. In the table footnote, the label should be “mean ± SD”, instead of “SD ± 0.1 or SD ± 0.2”, please check this out. Also, the average values and SD values are usually expressed with equal number of decimal digits.

Lines 541 – 545. The meaning of the sentences is unclear. Please rephrase.

Line 578. “C.” seems left here accidentally, please remove this.

Lines 671 – 672. The meaning of the sentence is unclear. Please rephrase.

Lines 709 – 710. Do these values refer to carrot juice? Please check this out.

Lines 710 – 711. Please check out this statement. In my opinion, the measured values suggest the opposite conclusion.

Figure 4 – both e) and f) graphs have the same y-axis label, please check and correct this.

Line 853. Temperature t₃ should be – 18°C instead of 18°C, please correct this.

Lines 865 – 869. This sentence is correct if comparing absolute values, but in relative values (percents) the decrease of vitamin C concentration is quite similar, maybe this should be pointed out.

Line 914 – highest retention or reduction at – 18°C? Please check this out.

English language needs extensive editing, some parts of text are difficult to understand because of grammar issues. 

Author Response

Dear Reviewer,

We would like to thank you for your careful reading of our manuscript (ID: applsci-2483139) entitled “New insights into the shelf life of vitamin C in plant and vegetable juices stored under different time, temperature, packaging conditions”. We appreciate your comments and constructive recommendations, which have contributed to the improvement of our manuscript. Here, we present separate answers to your comments.

Best Regards,

Małgorzata Kowalska,

Melania Feszterova,

Reviewer’s comments:

The manuscript entitled „New insights into the shelf life of vitamin C in plant and vegetable juices stored under different time, temperature, packaging conditions“ presents the study of vitamin C content in selected plant and vegetable juices, kept under different temperatures, in glass and plastic containers in different times of storage, determined by iodometric titration. The effect of different storing conditions is compared and statistically analysed. The topic is interesting, and the results could be useful in the juice production industry.

Response to Reviewer

1. General concept comments:

The manuscript is written extensively, some parts of text areconfusing and difficult to understand, and some parts could beshortened. All comments are listed below:

The Title of the manuscript is misleading because the results ofthe study do not point out the shelf life of the juices (the length oftime for which an item remains usable, fit for consumption, orsaleable according to dictionary) but rather deal with the contentof vitamin C under different storing conditions. The method usedand the conclusion of the statistical analysis of the results shouldbe briefly mentioned in Abstract of the manuscript.

Answer 1a: We modified the Title of this paper as follows:

„Stability of vitamin C content in plant and vegetable juices under different storage conditions“

Answer 1b: We have modified the Abstract of this paper as follows:

The effect of environmental variables on vitamin C degradation in the analysed plant and vegetable juice samples was investigated. The study focused on samples from chives, dandelion and nettle, as well as tomato, carrot, cucumber, red and white pepper and cabbage. The work aims were to summarise the impact of storage time, temperature, and packaging materials on antioxidants (using vitamin C as an example) in processing plant and vegetable juices. The vitamin C concentration was tested iodometrically at 0 to 21 days intervals. Storage was carried out at different temperatures (4 °C, 23 °C, -18 °C) and in selected two packaging materials (glass and plastic). The analyses showed that low temperatures (t = 4 °C) and storage in glass containers are best for preserving vitamin C content. Storage time influenced the decrease in vitamin C values, with higher losses with longer storage. Plastic containers had a shorter shelf life for vitamin C compared to glass containers. In general, high temperatures during processing and storage have had a negative effect on the preservation of vitamin C. Therefore, storing juices in refrigerator and glass containers intended for food applications to minimise vitamin C degradation is important.

2. The Materials and Methods section should be significantly shortened or rewritten more concisely. In section 2.1. Materials ,the chemicals used in iodometric titration should be listed. Description of plants and vegetables in section 2.1.1. is usefulbut too extensive for this section. My suggestion is to move thegeneral description of the selected plant and vegetable material in Introduction section, and to put the specific parts of the text that explain the handling of each plant or vegetable material in 2.2. Methods section (for example, lines 239 – 244 that describeplant material handling, and lines 249 – 252 that describe juicepreparation). Figure 1 also belongs to the Methods section rather than the

Materials section. The subtitles in Methods (lines 265and 277) are not necessary. Some sentences are in excess or unnecessary for this section (for example line 286 – 288, 307 –309).

Answer 2: We have modified the text of this paper as follows:

- The section 2. Materials and Methods has been significantly shortened and rewritten more concisely.

- In section 2.1. Materials, the chemicals used in iodometric titration have been supplemented.

- The content of section 2.1.1. Characteristics of chosen plants and vegetables, has been significantly shortened and rewritten more concisely.

The following text has been moved to section 1. Introduction:

A regular diet for humans should include plenty of vegetables because they are cheap in fat and calories, and full of carbohydrates and fibre, which means and an important source of several vitamins [5]. Consumers are becoming increasingly concerned about the number of vegetables they consume each day due to the development of a healthy diet. Additionally, the desire for pre- or half-prepared meals in today's fast-paced world contributes to a significant rise in the consumption of vegetables [50]. Many fruit and vegetable varieties are offered for a brief period right after production [14,26]. According to Mieszczakowska-Frąc, Celejewska, and; Płocharski, [14] found, that fruit and vegetables can be kept fresh for many months thanks to advanced techniques for storage. For centuries, most vegetables and fruit have been handled, allowing for year-round enjoyment of the products made from the harvest. Even though treatment is an excellent method to extend the duration of storage, it is nevertheless associated with significant degradation of several substances that have positive health effects, such as vitamin C, which rapidly degrades in process of treatment [14].

Repetitive sentences have been eliminated.

- Text passages that describe how specific plant and vegetable materials are processed have been added in section 2.2 Methods, such as lines 239–244 that describe processing plant material and lines 249–252 that discuss making juice.

- Figure 1 was inserted in 2.2 Methods section.

- In section 2.2 Methods, a few phrases (e.g., lines 286–288, 307–309) and a few subtitles (e.g., lines 265, 277) were omitted.

Specific comments:

Lines 39 - 40. The meaning of the sentence is unclear. Please rephrase.

Answer 3: We appreciate your guidance and your opinion. We have deleted the text because of the older literature.

Lines 98 – 101. The meaning of the sentence is unclear. Please rephrase.

Answer 4: The phrase has been restyled and has been included in the following sentence: The key elements that affect the vitamin C concentration are the type of container (glass or plastic) and the way in which juices from different plants and vegetables are stored.

Line 335 – words “caused by” are in surplus.

Answer 5: The word caused has been deleted and the sentence restructured as follows: The findings considering plant juices (chives, dandelion, and nettle) showed that nettle had the highest concentration of vitamin C (78.50 mg/100 g), followed by dandelion (69.50 mg/100 g) and chives (50.50 mg/100 g) (Figure 3).

Lines 361 – 363. The meaning of the sentence is unclear. Please rephrase.

Answer 6: The sentence has been modified as follows: A significant loss of vitamin C was recorded after 2 days of storage at t2 temperature (23 °C) in both storage materials (glass and plastic) (Figures 3b).

Lines 400 – 401. The abbreviation MAP isn’t explained,sentence is unclear.

Answer 7:  The definition of the abbreviation has been added, and the sentence has been restyled: According to Dermesonluoglu et al. [68], after being kept at temperatures ranging from 2 to 15 ^oC for a length of time, dandelion leaves revealed reductions of 34.85% and 52.80%, respectively, in ascorbic acid concentration.

MAP: modified atmosphere packaging

Line 415 – cited concentration of vitamin C seems wrongly written, please check this out.

Answer 8: We have modified the value  as follows: 10.0 ± 0.75 mg ascorbic acid/100 g of raw.

Line 416 – please clarify the meaning of the phrase “doubleaxial”.

Answer 9: We have modified the sentence as follows: In our research, the content of vitamin C was bigger (69.50 mg/100 g).

Lines 489 – 491. The sentence is cumber some and difficult to understand.

Answer 10: We have modified the sentence as follows: Therefore, as reported by Bhullar and Gruissem [71], it is important to have a comprehensive understanding of maintaining the highest possible vitamin C levels in the resulting crops, as with other micronutrients.

Lines 507 – 508. Wrong measurement units on concentration values.

Answer 11: Table 1 and foot note were corrected.

Lines 541 – 545. The meaning of the sentences is unclear. Please rephrase.

Answer 12: We have modified the sentence as follows: We discovered that red pepper juice, which ranged from 153.50 mg to 134.80 mg/100 mg, was the beverage with the highest concentration of vitamin C. White pepper juice, which ranged from 125.00 mg to 108.20 mg/100 mg, came in second. (Table 1).

Line 578. “C.” seems left here accidentally, please remove this.

Answer 13: The letter C has been deleted

Lines 671 – 672. The meaning of the sentence is unclear. Please rephrase. 

Answer 14: We have modified the sentence as follows: Different factors such as storage time and temperature, packaging material may affect the vitamin C content of vegetable juices.

Lines 709 – 710. Do these values refer to carrot juice? Please check this out.

Answer 15: We have modified the sentence as follows:  The loss of vitamin C in the plastic containers ranged from 36.33% (1^st day) to 49.44% (7^th day). The preservation of vitamin C in carrot juice in glass containers at freezing temperatures was significantly superior to that of plastic containers.

Figure 4 – both e) and f) graphs have the same y-axis label, please check and correct this.

Answer 16:  The graph  has been corrected:

Line 853. Temperature t should be – 18°C instead of 18°C, please correct this.

Answer 17: We have modified the temperature.

Lines 865 – 869. This sentence is correct if comparing absolute values, but in relative values (percents) the decrease of vitamin C concentration is quite similar, maybe this should be pointed out.

Answer 18: We have added the following sentence to the text: The equations demonstrated that red pepper juice had among the greatest contents of vitamin C reduction in glass containers at temperatures from t₁ to t₃ (4.37 mg/100 g, 4.47 mg/100 g, 4.89 mg/100 g), and salad cucumber juice had one of the smallest amounts (0.18 mg/100 g, 0,19 mg/100 g, 0,28 mg/100 g). The above observation is true when comparing absolute values, but the decrease in vitamin C concentration is quite similar in relative values.  

Line 914 – highest retention or reduction at – 18°C? Please check this out.

Answer 19: We have corrected the conjunction in the sentence to read “the highest reduction“.

Author Response File: Author Response.pdf

Reviewer 3 Report

In the article, the authors evaluated the vitamin C content and its stability over time, as a function of storage and packaging temperature, of three samples of plant juices six samples of vegetable juices, distinguishing between plastic containers and containers in glass.

The authors conducted a detailed research evaluating the vitamin C content with iodometric measurement and following its trend as a function of environmental and temporal parameters. However, the article is redundant in the qualitative descriptions of the samples and their properties, descriptions that are repeated in several parts of the article with an excessive use of bibliographic references. In my opinion the writing should be significantly streamlined in redundant and superfluous content before being reconsidered and published.

Author Response

Dear Reviewer,

We would like to thank you for your careful reading of our manuscript (ID: applsci-2483139) entitled “New insights into the shelf life of vitamin C in plant and vegetable juices stored under different time, temperature, packaging conditions”. We appreciate your comments and constructive recommendations, which have contributed to the improvement of our manuscript. Here, we present separate answers to your comments.

Best Regards,

Małgorzata Kowalska,

Melania Feszterova,

Reviewer’s comments:

In the article, the authors evaluated the vitamin C content and its stability over time, as a function of storage and packaging temperature, of three samples of plant juices six samples of vegetable juices, distinguishing between plastic containers and containers in glass. The authors conducted a detailed research evaluating the vitamin C content with iodometric measurement and following its trend as a function of environmental and temporal parameters. However, the article is redundant in the qualitative descriptions of the samples and their properties, descriptions that are repeated in several parts of the article with an excessive use of bibliographic references. In my opinion the writing should be significantly streamlined in redundant and superfluous content. The manuscript submitted by Feszterová and collaborators deals with a very interesting topic. However, its structure and writing need to be thoroughly revised.

Response to Reviewer

Answer: We have modified the paper and corrected the text to integrate the ideas and themes. By editing the text, we have tried to ensure clarity and flow of the content.

We have made the following changes to the text:

- we have shortened the scope concerning the descriptions of the samples and their properties,

- we have reduced the number of bibliographic references used,

- we deleted redundant parts of the text and reorganized the text.

Author Response File: Author Response.pdf