The Physicochemical and Nutritional Value of Fresh and Processed Portulacaria afra (Spekboom) Leaves

Reviewer 1

The contribution of the research is elementary. I suggest that the authors improve the applied analysis to the spekboom products.

We agree that it only covers the basics. However, the information reported has yet to be available. We are doing an improved analysis, but such information will take another two years to be ready for publication. In the meantime, we believe this basic information will be instrumental in stimulating new research on using Spekboom as a new food ingredient.

I suggest that the authors improve the applied analysis to the spekboom products, such as a sensory analysis, an antioxidant capacity analysis of the spekboom products, and/or bioactive compounds analysis.

The sensory analysis was done. It will be published in a separate article as it is a substantial body and work.

There are no figures in the manuscript. I suggest to the authors to include some pictures.

Pictures were added to the manuscript.

In table 1, I suggest to include the percentages of the ingredients for each spekboom product.

Due to the commercial producer’s fears that someone might reproduce their formulation, the percentages of ingredients were not disclosed to the researchers.

Nevertheless, what about the future work in your research? I suggest to state with more accurate your future research related with this study.

Thank you for the suggestion. Future research was added to the last part of the conclusion.

Reviewer 2

1.      Line 24: please add “Portulacaria afra” to Keywords.

It was added to the keywords.

2.      Line 54: will the reduction in coverage area of Portulacaria afra affect its application? Explain please.

Restoration programmes have been very successful. The information was added in lines 60-61.

3.      Line 58-60&65-67: does the open exploitation of Portulacaria afra affect the carbon cycle of the environment as well as life of animals? Explain please.

The plant grows and thrives in huge areas of the Eastern Cape and is prevalent in the Addo Elephant park. However goats can destroy the plant by overgrazing, and many farmers are converting their farms into more sustainable game farms to protect the P. afra against overgrazing. I review manuscript with the full information will be submitted soon to this journal. That will give more information on the conservation of the plant.

4.      Line 112: is the pre-speed 0.00mm/s? Please confirm it.

It is correct. Before the experiment starts (pre-speed), the needle probe is not moving.

5.      Line 112: consistency in the number of decimal places in the data throughout the manuscript.

The decimal places were standardized throughout the manuscript.

6.      Line 116: it is best to present the photo of leaves.

Two photos were added.

7.      Line 142: express the homogenization speed, time, and temperature.

The information was added.

8.      Line 144: is the ratio a mass ratio, or a mass to volume ratio? Please mark it.

It was made clear with both ratios

9.      Line 175-178: the description of the experiment need be more concise and accurate.

The experiment was described in detail.

10.   Line 230: writing errors “Physico-chemical characteristics s of spekboom leaves”.

The errors were corrected.

11.   Line 238-252: in the description of product colour, it should be added to compare with products on the market or products produced by other researchers.

The colour was compared to the fresh leaves and to each other because products made of another fresh product would not be comparable in colour. As far as we know, no published data exist on spekboom products by other researchers.

12.   Line 270: symbol missing.

The mistake was corrected.

13.   Line 274-352: please keep the format of the text consistent.

Thank you for pointing out the mistake, it was corrected.

14.   Line 321: wrong title.

The heading was corrected.

15.   Line 322-352: many other substances are added to the product, and the composition will certainly be very different. So what is the purpose of this part?

The aim of including the processed data with the raw data was to show that some of the nutrients survive the processing, and in fact, with the added ingredients, it remains a nutritious product. Raw and processed data have been compared before in published papers.

16.   Line 331: please keep the format of table title consistent.

Reviewer 3

All the assays are valid for the fresh plant material but I cannot see any relevance in comparing fresh leaves with their highly processed products with this set of assays (Tables 3, 4, 5, and 6). This is a fundamental flaw, and the paper needs extensive revision to remove these data. The fresh plant data can easily be presented with reference to literature values for similar succulents. The Results (and Discussion?) section compares spekboom to nopalitos and green peppers but there is no mention of these in the Materials and Methods section. Were they part of the experiment?

The aim of including the processed data with the raw data was to show that some of the nutrients survive the processing, and in fact, with the added ingredients, it remains a nutritious product. Raw and processed data have been compared before in published papers (de Wit et al., 2020)

The analyses and comparison of nopalitos and green peppers were done and published in 2021

(du Toit et al., 2021).    

de Wit, M., du Toit, A., Osthoff, G., & Hugo, A. (2020). Antioxidant content, capacity and retention in fresh and processed Cactus Pear (Opuntia ficus-indica and O. robusta) fruit peels from different fruit-colored cultivars. Frontiers in Sustainable Food Systems, 4(September), 1–14. https://doi.org/10.3389/fsufs.2020.00133

du Toit, A., Mpemba, O., de Wit, M., Venter, S. L., & Hugo, A. (2021). The effect of size, cultivar and season on the edible qualities of nopalitos from South African cactus pear cultivars. South African Journal of Botany, 142, 459–466. https://doi.org/10.1016/j.sajb.2021.07.025

Additionally, the manuscript requires extensive English editing, both for clarity and logic.

Lines 39-41 for example, link poverty, food insecurity, loss of biodiversity and environmental degradation in a confusing way.

An additional sentence or two on the challenges facing the Eastern Cape rural poor would help here.

 My recommendation for resubmission after major revision means that I won’t list all the errors line by line, but some in the Materials and Methods are as follows:

The manuscript was sent for English editing.

The confusing sentences has been improved.

A section was added to strengthen the argument.

Milliliters should be ml.

The manuscript has been updated according to the suggestion of the reviewer.

Line 92: were the leaves collected from similar parts on all plants, i.e. similar age?

The manuscript has been updated according to the suggestion of the reviewer.

Line 108: Size of the leaves? Length and width

The first test that was conducted on the leaves, was to determine the length, width and weight of each of the ten leaves that made up each sample.

Lines 130-131: ‘at different sections not far from each other.’ This is unclear. Given the average leaf size and the 8 mm diameter measurement aperture of the CR-400 meter was there any measurement area overlap?

As the probe is only 1 mm wide, there was no overlap.

RPM is not very useful when describing centrifugation as the rotor radius is unknown (RCF is better).

The full information concerning the centrifugal process was added.

Lines 155-159: recast this section for clarity.

A full explanation of the viscosity measurement was added.

Line 164: 1:1? 1 part pulp and 1 part...?

A full explanation was added for the determination of the pH.

Lines 168-169: ‘Sodium hydroxide was titrated at a rate of 0.5 mL and gently shaken using a magnetic stirrer.’ Better to write ‘Sodium hydroxide was added in 0.5 mL steps and gently stirred using a magnetic stirrer.’

A full description of the procedure was added.

Line 170: what was the calculation?

The calculation was added.

Line 171: ‘The 2.6 dichlor…’ should be ‘The 2,6-dichlor…’ Nerdy, 2018 isn’t referenced in the correct style.

The word was fixed, and the reference was corrected; thank you.

Lines 198-200: the CP assay needs more details and clearer description.

All the detailed descriptions were added.

Lines 206-208: needs more details.

All the details were added to the descriptions of the methods.

Line 220: ‘small and light in weight’ compared to what?

The manuscript has been updated according to the suggestion of the reviewer.

Reviewer 4

1. Main text - Line no. 50, first instance of appearance of plant name, write full name with authority and family.

The full name was added.

2. At the starting of the sentence the Genus name also has to be mentioned in full (Eg. Line 51 Not as P. It should be Portulacaria). Make the corrections wherever necessary.

The manuscript was updated as required.

3. Maintain uniformity in writing the Scientific name of the plant throughout the article. (Eg. Authors mention full names in line 65 earlier they mentioned P. afra). Please refer to the ICN guideline.

The error was corrected.

4. Mention a reference to substantiate Line 68 to 70 or explain how author concluded the sentence

Four references were added to substantiate the sentence, line 86.

5. Add a small paragraph on traditional uses of P. afra mentioned in scientific articles from south africa or elsewhere if any   6.

The information was added in lines 78 to 88.

6. Ambiguity in sample collection, simplify the paragraph and lines 88 to 91 Why 18 plants were purchased from the market? Whether the leaf samples were collected from the same planted P. afra?

IF yes, is P. afra can grow within 3 months after planting and ready for harvesting as it was a tree?

Eighteen plants were bought and planted to have ample sampling opportunities. We had to see if the plants survived and which plants grew better without signs of disease.

It was explained that the samples were collected from six plants. Thus, one sample consisting of 30 leaves was collected from a specific plant.

Yes, the plants were sufficiently established to collect samples from them.

7. Discussion heading was mission

The results and discussion were presented together under the heading found in line 290.

8. Discussion section was very poorly written  

The manuscript was rewritten and scrutinized to make the discussions more acceptable. Specific recommendations for further improvements would be appreciated.

9. Why only the results were compared with only green pepper and nopalitos, There are number of wild vegetables and fruits have been studied and those can be used for discussion Studies were also conducted on P. afra which were not mentioned in the study E.g. Phytochemical, biological, and in-silico characterization of Portulacaria afra Jacq.: A possible source of natural products for functional food and medicine 

The data was compared to green pepper and nopalitos as those analyses were done in our labs thus we know that the results are comparable. Green pepper is a popular  vegetable that readers can relate to, while nopalitos are an example of wild edible plants.

The paper mentioned was added to the manuscript lines 75-80. The data was not comparable thus it was not discussed in the results and discussion section.

10. Proper justification for study results under each section was not provided   Hence recommend the authors to rewrite the article for fresh submission

The manuscript was rewritten for clarity. Specific recommendations for further improvements would be appreciated.

Reviewer 5

Although I found merit in this study, however, the research content is not comprehensive. It is really bizarre that no figures exist in the manuscript.

Two pictures showing the plant have been added.

There are 8 paragraphs in the section Introduction, it is too many, and this section is suggested to be divided into 4 paragraphs.

We feel that having more paragraphs gives the introduction more of a logical flow and improves the readability of the text.

Furthermore, the authors should introduce more details about this work, as well as the practical significance of the study, in the last paragraph of the section Introduction.

We added the practical significance at the end of the introduction.

Similarly, please adjust the structures of section 2.2, 2.3, 3.1, 3.2 and section Conclusion. Line 321, the section 3.1 should be section 3.3.

The manuscript has been updated according to the suggestion of the reviewer.

In the section 2.3, more experimental details about nutritional value analysis should be provided. Herein, the authors just listed some references and the experimental methods were introduced briefly, it is insufficient.

The full descriptions were added.

Some figures are suggested to be added, in order to improve the readability of this paper.

The data did not lend itself to the use of graphs.

In addition, similar studies in 2022-2023 have been listed below.

https://dx.doi.org/10.13005/bpj/2494

Screening of Phytochemical Profile and Biological Activities in the Leaves, Stems and Roots of South African Portulacaria Afra using Four Extraction Solvents

https://doi.org/10.3390/molecules27082377

Phytochemical Profiling, Antioxidant, Anti-Inflammatory, Thrombolytic, Hemolytic Activity In Vitro and In Silico Potential of Portulacaria afra

doi: 10.34172/jhp.2023.10

A phytochemical screening, antioxidant and antibacterial activity analysis in the leaves, stems and roots of Portulacaria afra

We appreciate the information. It was added to the introduction.