Chemical Composition of Apples Cultivated in Norway

Round 1

Reviewer 1 Report

Manuscript contains interesting data and is quite good prepared, however I have a few comments.

In Methods (2.4. Statistical analyses) authors should provide details related to the PCA analysis. Further, in Results and methods the interpretation/discussion of the results presented in Figure 1 a & b should be added.

Moreover, the authors wrote that ANOVA was conducted, but Tables in the manuscript do not contain its results. Therefore, the results in tables should be supplemented with the letters or symbols that show which mean values are statistically different. Similar information should be taken into account in the discussion part….

Author Response

In Methods (2.4. Statistical analyses) authors should provide details related to the PCA analysis. Added in 2.4: Principal component analyses (PCA) were performed for juices to estimate difference in chemical composition due to cultivar. Further, in Results and methods the interpretation/discussion of the results presented in Figure 1 a & b should be added. More comments to PCA are included in 3.1. Apples. : Significant differences were observed between the samples for the different chemical compounds (Tables 2-4), though we found no difference between groups of old and new cultivars nor on growing location (grouped in Table 1) for the studied composition. Climate and topography for the two growing locations are very different. However, this did not appear to have any effect on the chemical composition of the apple juice.

Moreover, the authors wrote that ANOVA was conducted, but Tables in the manuscript do not contain its results. Therefore, the results in tables should be supplemented with the letters or symbols that show which mean values are statistically different. Similar information should be taken into account in the discussion part….

Tables are updated

Reviewer 2 Report

Comments can be found in the attached manuscript as well.

Introduction:

• Please add hypothesis of the study

Materials and methods:

• Please add some climate information about locations
• mention the year?
• Did you apply any treatment? or you investigated only the effect of cultivar and location?
• Provide more detailed-information about site, managements, treatments and .....for each cultivar. These cultivars were fertilized or not?
• How was the growing condition for each cultivar? That was the same for all of them?
• Did you follow any references? If yes, cite it here
• How did you prepare the sample extractions for this procedure? Please explain it

Results and discussion:

• Please indicate statistical significance of between group mean comparisons by letters. Please do it for all tables (1-4).
• How was fertilization management in your case study?
• Interpret the results with your experiments condition. Why you got these results? What was the main effect on each?

References:

• References numbers: 5, 7, 25, 29 and 40 are too old. Replace them with newer references.

Comments for author File: Comments.pdf

Author Response

Round 2

Reviewer 2 Report

Dear Authors,

Thank you for your efforts to provide more details and improve your manuscript.

• Why did you add mean comparisons by letters only for some of the parameters?  
• Please mention the method  in section 2.4 (how did you do?)
• In tables: letters are not clear for me. Why in some cases, higher numbers got smaller letters? Please check once again all letters.

Author Response

Comments to questions:

• Why did you add mean comparisons by letters only for some of the parameters?  

Mean comparison letters is added for fruit weight.

Comparison letters are not included for percentage distribution of some amino acids as these are numbers calculated from the measured data of FAA. The main effect is expressed by the total amount. The Total polyphenolics (HPLC) – flavanols, hydroxycinnamic acids, dihydrochalcones and flavonols are sums of two or more single components. The main effect is expressed by the total polyphenols.

• Please mention the method  in section 2.4 (how did you do?)

Text in 2.4 changed to:

The results are expressed as mean ± standard deviation (STD) from 2 to 5 independent measurements. Correlation test, one-way analysis of variance (ANOVA) and Principal component analysis (PCA) were performed to find differences between varieties, groups of apple varieties (old and new, sharp and dessert apples) and growing sites in terms of chemical composition in the juice of the various apples. Statistical analyses were performed with Minitab statistical software version 17 (Minitab Ltd., UK).

• In tables: letters are not clear for me. Why in some cases, higher numbers got smaller letters? Please check once again all letters.

To clarify – letters are removed to the measured number - from STD. Folin content Aroma Amorosa 598 mg/L should have letter “c” – mistyping – this is corrected.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript entitled “Apples from Norway and their potential use for cider production” describes the composition of 17 varieties of apples grown in Norway. The authors carefully studied the composition of the fruit and the obtained results can be used to select the cultivars potentially useful for the cider production.

However, in the present form the manuscript presents a low scientific level and should not be published in Foods. According to the reviewer, ciders should be produced from these varieties and only on the basis of their quality, the varieties suitable for the cider production should be selected.

 Minor remarks:

• the statistical significance of the results is lacking (tab. 2-4)
• In Tab. 3 the amino acid abbreviations should be explained (e.g., add below the table)
• “Unfortunately, samples for phloroglucinolysis were lost; that’s why total flavanols data, and also the sum of polyphenols, are not given for this variety. This sample will need to be verified ”- repeat the analysis before submitting the manuscript

Reviewer 2 Report

In general I find the paper well written and presented. Mostly the following remarks are details.

Some places I like to see more references used: In the intro page 1 for the taste categories. Page 2. a ref would be good to the sentense: The protein content of cider apple cultivars is usually rather low.

Page 2: concerning YAN. I believe it is concidered to be alpha amino acids + ammonia. 

Page 2: ... quite stabilised against microbial growth ... should be changed to ... quite stable against microbial .... 

page 2 last sentence should be revised. In addition, the got information .... 

Page 3: The parents of Filippa are unknown. Genotyping does not prove Gravenstein to be one of the parents.

Page 3: section 2.2.1. a few things are unclear. are slices taken from all apples for the iodine test? Which juice samples are used for which analysis (NaF +/-)? 

The end of section 2.3.: ... described Malec et al. change to: ... described by Malec et al. [19]. 

Table 2: what is N (number of replicates) in this table? 3 or? variation of pH? Fruit size it it an average based on the weight of 10 apples or....?

Table 4: The order of the columns should be according to the order it is presented in the text on page 7. fx place TP (Folin) first and not last. The column of Total polyphenols should also be moved.

Adjust the footnotes to the left.

Last line on page 6. The paper 26 is not about apples but asian pear!

It is different factors which are in play concerning the fruit size effect: Is it a small fruited cultivar? then it is genetics. If small due to fruit/leaf ration then it is a matter of source/sink balance. For the sake of a balanced presentation it should also be noted that Mutsu is one of the bigger ones but one of the lowest in nitrogen. It is 'cherry picking' only to mention Torstein (H) which fit to the relationship: small = low in N content. Big ones may also be low as Mutsu illustrates! 

Page 7: section sugar contents: the unit g/L is used for density. In other places kg/m3 is used. It should be g/L in all cases. The paragraph ends with ... by the number of apples in the tree. It is more correct to say .. fruit/leaf ratio.

Page 7: the data on flavonols are not presented/discussed.

Page 8 line 5: seems to more variety. change to seems to be more....

last line i the paragraph.. change to ... cider processes such as... Also ad a reference for the keeving process. 

line 15: change to: .... bitternes and astringency.  

Future aspects:

I think the level of high nitrogen in the cultivars mentioned Aroma Amorosa, Delcorf, Filippa etc is not documented good enough in the study to be cultivar related and cause a statement saying they should be avoided. 

I would have liked to see more focus in the paper discussing the impact of nitrogen status of the tree and how this influence the nitrogen content of the apples. 

It could also be discussed more when a level of YAN is high or to high. In grape wine making a YAN of 150 would be concidered a minimum and not high. It may be high if you want the yeast to stop before the fermentation has run dry, but for a good clean fermentation resulting in a dry wine a higher YAN could be more ideal in terms of fulfilling the needs of the yeast. 

Reviewer 3 Report

The manuscript entitled “Apples from Norway and their potential use for cider production” by Trude Wicklund, Sylvain Guyot and Jean-Michel Le Quéré presents the biochemical composition of 17 apple cultivars grown in Norway.

In my opinion the work is lacking novelty, as there are many similar papers describing the chemical composition of apples depending on cultivar. I do not think it would be possible to draw reliable conclusions about the possibility of using a given apple variety for the production of ciders only on the basis of the results of their chemical composition. Alcoholic fermentation and the production of cider suitable for consumption is a complicated process and depends on many factors that often interact (synergism, antagonism and many more) and it is necessary to maintain a delicate balance between e.g. content of sugars, polyphenols, amino acids, and acidity. Moreover, the presence of the precursors of volatile compounds desirable for cider taste together with the absence of precursors of unwanted compounds is essential. The possibility of good cider producing depends also on the yeast strain that should be properly matched to the apple cultivar. Other aspect is for example the polyphenols content, too high can inhibit yeast activity and stop the fermentation process.

Without actual tests of cider production and basic analyzes of its quality, including organoleptic evaluation, there are no grounds to conclude on the suitability of a given apple cultivar. This means that the evaluated manuscript is only a presentation of the chemical composition and should have a completely different title. And this, in my opinion, is too little to be worth publishing in such a good journal as Foods. Especially since the results have not even been statistically processed. Maybe there are some correlations of chemical composition with old / new cultivar or region…. ?

Other remarks:

The tables provide "average" values, and according to the methodology these are means of 3 repetitions. However, the results are not presented in typical form. Is “STD” a standard deviation? All abbreviations should be explained the first time they appear. Even if yes, standard deviation is missing for majority of the results.

Moreover, the authors declare that one-way analyzes of variance (ANOVA) were performed to the ex-perimental data. Where are the results of the statistical analysis?