Reproducible Method for 1-Methylcylopropene (1−MCP) Application and Quantitation for Post-Harvest Research
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsSee attached!
Comments for author File: 
Comments.pdf
Author Response
Reviewer #1
Comment 1: Assumptions about 1-MCP Liberation: The study makes an assumption regarding the complete liberation of 1-MCP from the cyclodextrin inclusion complex. It would be beneficial for the authors to either provide empirical evidence supporting this assumption or to outline the potential implications if this assumption does not hold in all conditions.
Response: This aspect has been addressed in the manuscript with the following explanation. Please see lines 222-229.
1-MCP liberation from inclusion complexes has traditionally been accomplished by complete hydration of the powdered complex for research purposes1,2 and as advised by commercial chemical manufacturer AgroFresh 3. However, as mentioned previously, recent research into the release kinetics of 1-MCP from inclusion complexes suggest decreased release due to inclusion complex collapse at relative humidity of greater than 60%4. The method outlined in this report has attempted to improve upon the two aforementioned approaches by incorporating constant agitation via magnetic stir bar and thereby ensuring complete liberation of 1-MCP.
(1) Gamrasni, D.; Ben-Arie, R.; Goldway, M. 1-Methylcyclopropene (1-MCP) Application to Spadona Pears at Different Stages of Ripening to Maximize Fruit Quality after Storage. Postharvest Biol. Technol. 2010, 58 (2), 104–112. https://doi.org/10.1016/J.POSTHARVBIO.2010.05.007.
(2) Gamrasni, D.; Goldway, M.; Stern, Y.; Breitel, D.; Aharoni, A. 1-MCP (1-Methylcyclopropene) Treatment Protocol for Fruit or Vegetables. BIO-PROTOCOL 2017, 7 (10). https://doi.org/10.21769/BIOPROTOC.2278.
(3) U.S. Environmental Protection Agency (EPA). SmartFresh ProTabs Non-PRIA (Pesticide Registration Improvement Act) Labeling Amendment,; 2021.
(4) Ariyanto, H. D.; Yoshii, H. Effect of Stepwise Humidity Change on the Release Rate Constant of 1-Methylcyclopropene (1-MCP)in a Cyclodextrin Inclusion Complex Powder. Food Packag. Shelf Life 2019, 21, 100322. https://doi.org/10.1016/j.fpsl.2019.100322.
Comment 2: Use of Surrogate Standards vs. Mass Spectrometer: The manuscript mentions the necessity of surrogate standards due to challenges in 1-MCP detection by chromatography without a mass spectrometer. While the surrogate solution is innovative, it would be constructive for the authors to compare and contrast this approach with potential outcomes if a mass spectrometer was used. This would provide clarity on the relative advantages and limitations of their chosen method.
Response: The method presented in this study attempts to circumvent the use of costly mass spectrometry equipment in favor of gas chromatography machinery more widely available in post-harvest research laboratories. As is evident from the results, adherence to the outlined methodology and use of surrogate standards has been efficient in the identification of the 1-MCP peak of interest. Should further validation of specific alkene peaks be necessary, the United States Department of Commerce National Institutes of Standards and Technology have published freely accessible electron ionization mass spectra for 1-methylcylopropene, as well as Cis-2-butene (NIST, 2-butene) and 1-butene (NIST, 1-butene). A new figure (Figure 4) has been added to the manuscript along with the references below.
NIST Office of Data and Informatics. (n.d.). 2-butene, (Z). 2-Butene, (Z)-. https://webbook.nist.gov/cgi/inchi/InChI%3D1S/C4H8/c1-3-4-2/h3-4H%2C1-2H3/b4-3-
NIST Office of Data and Informatics. (n.d.-a). 1-butene. 1-Butene. https://webbook.nist.gov/cgi/cbook.cgi?Name=1-butene&Units=SI
Figure: Mass spectra for 1-methylcyclopropene (1-MCP), available for reference through the United States Department of Commerce National Institutes of Standards and Technology.
Reviewer 2 Report
Comments and Suggestions for Authors
The manuscript addresses a very important topic in postharvest processing, considering the numbers of food losses in the world (production, postharvest, distribution). However, authors need to consider some important aspects:
1. The introduction should be completed by including: the definition of climacteric fruits, the main causes of food waste generation, the 1-MCP structure. In addition, when mentioning previous studies please include the 1MCP concentration used and exposure time.
2. How does the development of the method align with the scope of the journal? Since the purpose of the study is to give a reproducible method for its use in postharvest research, the manuscript should be completed by including a study using a climacteric fruit. Otherwise, the development of the method for 1-MCP application and quantification would be outside the scope of the journal: horticulturae.
Author Response
Reviewer #2
Comment 1: The introduction should be completed by including: the definition of climacteric fruits, the main causes of food waste generation, the 1-MCP structure. In addition, when mentioning previous studies please include the 1MCP concentration used and exposure time.
Response: Following information has been added to the introduction.
Main causes of food waste generation: See lines 26-30: In fruits, early ripening, and associated processes such as flesh softening, and starch-to-sugar conversion are major causes of food wastage post-harvest. Crops with high water content, or those susceptible to damage from changes in temperature or humidity such as fresh fruits and vegetables are far more likely to suffer postharvest decay and wastage than grains or tree nuts for example.
Define climacteric fruit: See lines 31-34: Climacteric fruit exhibit a burst in respiration (characterized by CO2 evolution), with an accompanying increase in ethylene synthesis. These fruits continue to ripen through phytohormone-driven positive feedback loops even after they are picked from the mother plant.
1-MCP structure: Please see line 42: One means of combatting food wastage, especially in vulnerable crops such as climacteric fruit, is to delay the onset of ripening. Perhaps the most powerful tool for this effort is the gaseous 4-carbon cyclical alkene 1-methylcyclopropene (1-MCP), which inhibits perception of the “ripening phytohormone” ethylene.
“In addition, when mentioning previous studies please include the 1MCP concentration used and exposure time.” Please see updated Table 1 where the following details have been included.
Pineapple conditions: 0.1 ppm (4.5 nmol l−1) for 18 h at 20°C
Fig conditions: 0, 0.25, 0.5 or 5 µl l−1 1-MCP at 25 °C for 8 h and stored at 20 °C
Jujube conditions: 0.5 ppm of 1-MCP for 24 h at 20 â—¦C
Mango conditions: 1μll−1 1-MCP 24h and stored at 20°C for up to 16days
Apricot conditions: 1000 nl l−1 1-methylcyclopropene (1-MCP) at 20 °C for 20 h
Nectarine conditions: 0°C for 30 days after treatment with 0.1 ppm 1-methylcyclopropene (MCP)
Peach conditions: .5 mL·L–1 1-MCP for 4 hours at 20 °C
Peach conditions 2: 0.9 μL L−1 of 1-methylcyclopropene (1-MCP) for 24 h, at 25 ± 3 °C and 75 ± 5% RH
Comment 2: How does the development of the method align with the scope of the journal? Since the purpose of the study is to give a reproducible method for its use in postharvest research, the manuscript should be completed by including a study using a climacteric fruit. Otherwise, the development of the method for 1-MCP application and quantification would be outside the scope of the journal Horticulturae.
Response: The method addresses a major bottleneck in conducting experiments with 1-MCP due to the lack of reproducible application in research experiments. Therefore, this study is in the scope of the journal. The method describes a novel, cost effective approach to empirically determining 1-MCP concentration. 1-MCP is routinely used in ethylene and ripening related research, and minimizing variability in application will serve as a means of enhancing the quality post-harvest research. This method has been extensively employed in ongoing studies being conducted in our lab. No new or novel data would be generated by incorporating fruit into the headspace because the variable of interest in this study is 1-MCP concentration.
Reviewer 3 Report
Comments and Suggestions for AuthorsThis manuscript provides an alternative method to application and quantification of 1-methylecylopropane (1-MCP). In general, study is novel and provides new insight for the proper application of 1-MCP during post-harvest storage of fresh produce. In my opinion, abstract, introduction, M&M, results and conclusion is presented well and merits the publication in the present form.
Author Response
Reviewer #3
Comment: This manuscript provides an alternative method to application and quantification of 1-methylecylopropane (1-MCP). In general, study is novel and provides new insight for the proper application of 1-MCP during post-harvest storage of fresh produce. In my opinion, abstract, introduction, M&M, results and conclusion is presented well and merits the publication in the present form.
Response: Authors thank reviewer#3 for their constructive comments.
