The Quality Assessment of Sour Cherries Dried Using an Innovative Simultaneous Osmotic–Microwave–Vacuum Approach Based on Image Textures, Color Parameters, and Sensory Attributes

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The article deals with the drying of sour cherries using osmotic drying, microwave and vacuum.

 

The paper is interesting and well organized, however, there are opportunities for improvement and observations which are detailed below:

 

In the abstract when the conditions of the experiment are established, there is no mention of the power used and the vacuum, only the concentration of sucrose used is specified.

Could the summary include information regarding the duration of the drying process?

 

In l52 when drying is mentioned, it could be mentioned some disadvantages of traditional drying such as deterioration due to high temperatures and long drying times/energy consumption.

In l57 when talking about the use of microwaves to assist drying processes, it would be good to mention that the use of microwaves involves heat transfer by radiation.

In l63 it could be included that the use of osmotic drying can improve conversion by adding solids.

In l100 if the drying device is a single design, a schematic diagram could be included.

 

In l114 what do you mean by two technological repetitions?

In l118 is it necessary to use sub-index for water activity?

In l136 is the manual brightness criterion not clear?

 

Figure 2 could include some reference to size/scale.

In l153 the observer used is missing.

 

Important in all tables average values are reported, if repetitions were made the values should also include the respective standard deviations?

 

It is striking that in the work, dedicated to drying, there is no mention of aspects such as initial and final humidity, there is no drying curve. There are also no references to energy costs, drying times. 

The discussions could be improved if, in addition to presenting the data, an analysis of these data in context/meaning was made.

The present reviewer considers that the work would be considerably improved if these observations were taken into account.

Author Response

Author's Reply to the Review Report (Reviewer 1)

Comments and Suggestions for Authors

The article deals with the drying of sour cherries using osmotic drying, microwave and vacuum. The paper is interesting and well organized, however, there are opportunities for improvement and observations which are detailed below:

 

Comment 1. In the abstract when the conditions of the experiment are established, there is no mention of the power used and the vacuum, only the concentration of sucrose used is specified.

Response 1. It has been added as ‘microwave-vacuum drying at microwave powers of 100 W for 900 seconds, 300 W for 900 seconds, 250 W for 900 seconds, and 0 W for stabilization for 900 seconds and the pressure of 30±2 hPa.’

 

Comment 2. Could the summary include information regarding the duration of the drying process?

Response 2. It has been included as follows:

‘The simultaneous osmotic-microwave-vacuum drying was carried out in one process lasting an hour and combining osmotic dehydration using 40 °Bx sucrose solution and microwave-vacuum drying at microwave powers of 100 W for 900 seconds, 300 W for 900 seconds, 250 W for 900 seconds, and 0 W for stabilization for 900 seconds’

 

Comment 3. In l52 when drying is mentioned, it could be mentioned some disadvantages of traditional drying such as deterioration due to high temperatures and long drying times/energy consumption.

Response 3. It has been corrected as follows:

 ‘An advantage of vacuum drying is also energy saving [12]. These advantages are important compared with traditional convective drying using hot air. Convective drying, requires high temperatures and relatively long times, which can result in product deterioration in terms of nutrients, color, and shrinkage [4].’

 

Comment 4. In l57 when talking about the use of microwaves to assist drying processes, it would be good to mention that the use of microwaves involves heat transfer by radiation.

Response 4. It has been corrected as follows:

‘Microwave radiation as a non-ionizing radiation energy can alter the structural and functional properties of food ingredients. Microwaves are a fast heating source directly affecting the food material and speeding up drying rate, and physicochemical reactions, as well as producing high-quality dried products [15].‘

 

Comment 5. In l63 it could be included that the use of osmotic drying can improve conversion by adding solids.

Response 5. It has been corrected as follows:

‘Osmotic dehydration can result in an increase in water loss (WL) and solid gain (SG) with an increase in time of osmotic dehydration of frozen sour cherries [16].‘

 

Comment 6. In l100 if the drying device is a single design, a schematic diagram could be included.

Response 6. The photo of Microwave Vacuum Drying System has been added and is presented in Figure 1.

 

Comment 7. In l114 what do you mean by two technological repetitions?

Response 7. It has been corrected as ‘two technological repetitions (two processes of drying)’.

 

Comment 8. In l118 is it necessary to use sub-index for water activity?

Response 8. It has been corrected as ‘water activity (a_w)’.

 

Comment 9. In l136 is the manual brightness criterion not clear?

Response 9. It has been explained as follows:

‘The image segmentation was carried out using a manually determined brightness threshold of 10. The background was characterized by an intensity of 0. Each fruit was lighter from the background and was separated and considered as one ROI.’

 

Comment 10. Figure 2 could include some reference to size/scale.

Response 10. This Figure was created to compare differences in the appearance of images in different color channels of sour cherry samples before and after drying. The geometric parameters including linear dimensions were not considered. Therefore, the information on size/scale is not included.

 

Comment 11. In l153 the observer used is missing.

Response 11. It has been added as follows:

‘For the color measurements, the CIE standard illuminant D65 and the observer 10° were used.’

 

Comment 12. Important in all tables average values are reported, if repetitions were made the values should also include the respective standard deviations?

Response 12. The standard deviations have been added.

 

Comment 13. It is striking that in the work, dedicated to drying, there is no mention of aspects such as initial and final humidity, there is no drying curve. There are also no references to energy costs, drying times. 

Response 13. The information on the initial and final dry matter content has been added as follows:

‘The initial dry matter contents for raw materials were equal to 16.3% for ‘Nefris’, 15.8% for ‘Debreceni Botermo’, and 12.3% for ‘Łutówka’. The final dry matter contents for dried products were 96.8% for ‘Nefris’, 92.1% for ‘Debreceni Botermo’, and 95.0% for ‘Łutówka’.’

The drying times have been mentioned as follows:

‘The procedure was divided into 4 stages, including 3 stages of drying, such as the 1st stage at a microwave power of 100 W for 900 seconds, the 2nd stage at 300 W for 900 seconds, and the 3rd stage at 250 W for 900 seconds, as well as the 4th stage as stabilization for 900 seconds. The whole operation took an hour.’

 

The objective of this study was to determine the influence of an innovative drying procedure combining osmotic dehydration and microwave-vacuum drying in one simultaneous process on the quality of final products. In this study, the properties, such as image textures, color parameters, and sensory attributes of the dried fruit were most important and the authors did not focus on drying curves. However, the second planned article as a continuation of the research will be more detailed and will take into account the influence of osmo-microwave-vacuum drying on the chemical properties of fruit and will include drying curves and energy costs.

 

Comment 14. The discussions could be improved if, in addition to presenting the data, an analysis of these data in context/meaning was made.

Response 14. The discussion has been improved as follows:

‘The own study proved that an innovative approach to osmotic dehydration and microwave-vacuum drying of sour cherries allowed for maintaining a high quality of dried fruit in terms of sensory attributes, image features, and color parameters compared to raw material. The developed osmo-microwave-vacuum drying can be of practical importance for preserving sour cherries without losing their quality. The application of the approach combining image analysis and machine learning provided a quick and objective assessment of the effect of drying on fruit. It can be used in further studies to compare raw material and dried fruit, distinguish cultivars, and classification of dried fruit using machine learning models based on image parameters. In the available literature, for the classification of dried fruits and fruit products, machine learning models were successfully applied, among others, by Przybył et al. [28], Przybył et al. [29], Bisri and Man [30], Baigvand et al. [31], and Raihen and Akter [32].

As reported in previous studies, the application of imaging allowed for the prediction of fruit quality, including sensory attributes and physicochemical properties [33-35]. In view of the results of the above-mentioned studies, future studies can also be supplemented by determining the relationship between image features, sensory attributes, and chemical properties of dried sour cherries and developing predicting models based on image parameters.’

 

Comment 15. The present reviewer considers that the work would be considerably improved if these observations were taken into account.

Response 15. Thank you very much for your valuable comments. Your comments have been considered and the manuscript has been improved.

 

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

I reviewed the manuscript and I found it very well written and interesting. The topic is "evergreen" and I respect the effort of all authors and coauthors. However, I have one suggestion for the improvement of this scientific paper. It is related to the experimental setup. It would be of great interest for all food-drying enthusiasts to have more details in the paper about the experimental setup, i.e. photos of the experimental installation or its schematic at least, and not just the block diagram. What equipment did you use? Characteristics and performance data? Is the installation custom-made or universal? Etc, etc...

Author Response

Author's Reply to the Review Report (Reviewer 2)

Comment. I reviewed the manuscript and I found it very well written and interesting. The topic is "evergreen" and I respect the effort of all authors and coauthors. However, I have one suggestion for the improvement of this scientific paper. It is related to the experimental setup. It would be of great interest for all food-drying enthusiasts to have more details in the paper about the experimental setup, i.e. photos of the experimental installation or its schematic at least, and not just the block diagram. What equipment did you use? Characteristics and performance data? Is the installation custom-made or universal? Etc, etc...

Response. Microwave Vacuum Drying System has been added and is presented in Figure 1.

The following sentences have been included in the manuscript:

‘The drying was performed with the use of a laboratory custom-made microwave-vacuum dryer (Promis-Tech, Wrocław, Poland). Microwave Vacuum Drying System is presented in Figure 1. The drying system comprised a polypropylene drying chamber, motor, microwave generator, control unit, and units for the measurements of temperature and pressure.’

Additionally, a detailed description of the process and drying parameters are included in the manuscript.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This manuscript evaluated the effects of hybrid osmotic dehydration and microwave-vacuum drying on sour cherries through image texture from color channels, the color difference and sensory attributes. The writhing is well, but the novelty of this work is not clear. Imaging analysis for food quality has been studied in numerous application, particularly for those based on color system. The osmotic-microwave-vacuum drying is also reported in many literature regarding fruits and vegetables. The authors need to provide more justification why it is important to assess the quality of dried sour cherries using sensory evaluation along with color only.

 

Major concerns:

1. Why use both three color systems from the images, and the color difference obtained from spectrophotometer? RGB, Lab and HSV only represent color channels, and not that much difference among them compared to that of color vs. other texture information from the images. Also, the color difference can be calculated from the Lab values through image analysis.

2. Why using the drying approach showed in Figure 1? The reasons for choosing this procedures for sour cherries, particularly the processing parameters should be given out in this study.

 

Some minor remarks:

1. A schematic view of the drying equipment is suggested to given out in the materials and methods section.

2. Table 2 & 3 & 4 : the standard deviations are missing.

3. L200-201: How to get the conclusion that “drying had the smallest effect on fruit belonging to the cultivar ‘Nefris’”? The statistic results in Table 2 can not support this statement. 

Comments on the Quality of English Language

The paper reads well, but can be more concisely. 

Author Response

Author's Reply to the Review Report (Reviewer 3)

 

Comments and Suggestions for Authors

Comment 1. This manuscript evaluated the effects of hybrid osmotic dehydration and microwave-vacuum drying on sour cherries through image texture from color channels, the color difference and sensory attributes. The writhing is well, but the novelty of this work is not clear. Imaging analysis for food quality has been studied in numerous application, particularly for those based on color system. The osmotic-microwave-vacuum drying is also reported in many literature regarding fruits and vegetables. The authors need to provide more justification why it is important to assess the quality of dried sour cherries using sensory evaluation along with color only.

Response 1. The sour cherries in their frozen form were dried using an innovative drying technique combining osmotic dehydration and microwave-vacuum drying in one simultaneous process as osmo-microwave-vacuum drying. The process carried out according to the patent PL 236950 B1 with slight modifications was a great novelty for the dehydration of sour cherries. The available literature does not contain information about quality assessment in terms of image textures, color parameters, and sensory attributes of sour cherries of different cultivars dried using a simultaneous osmotic-microwave-vacuum procedure.

The novelty and importance of the research were more emphasized in the manuscript as follows:

‘In the present study, an innovative drying procedure combining osmotic dehydration and microwave-vacuum drying in one process was applied to the dehydration of sour cherries. The objective of this study was to determine the influence of the developed osmo-microwave-vacuum drying on the texture parameters of images in color channels R, G, B, L, a, b, X, Y, and Z, color parameters L*, a*, and b*, the color difference (∆E), and sensory attributes related to appearance, aroma, color, texture, taste, and overall quality. The great novelty of this study was to compare the non-destructively and destructively assessed attributes of raw and osmo-microwave-vacuum dried sour cherries belonging to different cultivars. Furthermore, image textures from individual color channels R, G, B, L, a, b, X, Y, and Z were used for the first time to assess the quality of sour cherry products obtained using osmotic dehydration and microwave-vacuum drying and provided reliable and objective results.’

Moreover, the next planned article as a continuation of the research will be more detailed and will take into account the influence of osmo-microwave-vacuum drying on the chemical properties of fruit.

 

Major concerns:

Comment 1. Why use both three color systems from the images, and the color difference obtained from spectrophotometer? RGB, Lab and HSV only represent color channels, and not that much difference among them compared to that of color vs. other texture information from the images. Also, the color difference can be calculated from the Lab values through image analysis.

Response 1. Image analysis was used to determine image texture parameters. Whereas a spectrophotometer was used to measure color parameters.

The computed texture parameters were extracted from images in color channels L, a, and b belonging to Lab color space, color channels R, G, and B belonging to RGB color space, and X, Y, and Z belonging to XYZ color space. Quantitative textural analysis was important because it could provide diagnostic information about object quality based on numerical data computed from the images. Image texture parameters can specify the changes that are difficult to relate to changes perceived visually. Even if objects are composed of the same color histograms and the same number of pixels, but have a dissimilar color distribution, they can be characterized by different textures.

We agree that the color difference can be calculated from the Lab values through image analysis. However, the application of a spectrophotometer to determine the color parameters was a simpler and quicker procedure. The determination of image parameters required image acquisition and image processing, including image segmentation, regions of interest (ROIs) identification, and image feature extraction.

 

 

Comment 2. Why using the drying approach showed in Figure 1? The reasons for choosing this procedures for sour cherries, particularly the processing parameters should be given out in this study.

Response 2. The parameters of osmo-microwave-vacuum drying have been indicated as follows:

‘A sample of 100 g of frozen sour cherries without pits was placed into a glass jar. Then, 60 g of 40 °Bx sucrose solution prepared using sucrose and tap water was added as an osmotic solution. Sour cherries and a solution were mixed thoroughly before placing the jar into the dryer. Then process combining osmotic dehydration and microwave-vacuum drying was performed simultaneously in one device. The procedure was divided into 4 stages, including 3 stages of drying, such as the 1st stage at a microwave power of 100 W for 900 seconds, the 2nd stage at 300 W for 900 seconds, and the 3rd stage at 250 W for 900 seconds, as well as the 4th stage as stabilization for 900 seconds. The whole operation took an hour. The pressure during the drying was 30±2 hPa and the temperature was below 60°C.’

 

As indicated in the manuscript:

‘The own study proved that an innovative approach to osmotic dehydration and microwave-vacuum drying of sour cherries allowed for maintaining a high quality of dried fruit in terms of sensory attributes, image features, and color parameters com-pared to raw material. The developed osmo-microwave-vacuum drying can be of practical importance for preserving sour cherries without losing their quality.’

‘Innovative simultaneous osmotic-microwave-vacuum allowed for obtaining dried sour cherries with high quality, including acceptable sensory attributes.’

 

Some minor remarks:

Comment 1. A schematic view of the drying equipment is suggested to given out in the materials and methods section.

Response 1. The photo of Microwave Vacuum Drying System has been added and is presented in Figure 1 in 2. Materials and Methods section.

 

Comment 2. Table 2 & 3 & 4 : the standard deviations are missing.

Response 2. The standard deviations have been added.

 

Comment 3. L200-201: How to get the conclusion that “drying had the smallest effect on fruit belonging to the cultivar ‘Nefris’”? The statistic results in Table 2 can not support this statement. 

Response 3. This sentence has been deleted.

Author Response File: Author Response.pdf