Recent Advances and Applications of Imaging and Spectroscopy Technologies for Tea Quality Assessment: A Review

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The goal of this work is to provide a comprehensive overview of imaging and spectroscopy technologies, focusing on non-destructive evaluation of tea quality, while discussing challenges and future research directions.
2. The work is well-structured, with clear sections covering everything from technologies to challenges and future trends. The conclusion summarizes the information, but it could delve deeper into practical applications.
3. The introduction provides a good overview of tea and the technologies, but it could offer more detail on how each technology is applied in evaluating tea quality, making it easier for readers to understand.
4. The work makes a positive contribution to the field, discussing innovative technologies that can improve traditional tea quality evaluation methods and providing a foundation for future research.
5. Although the work is relevant, it could explore the technologies in more depth in the context of tea quality, strengthening its contribution.
6. The second section clearly describes technologies applicable to tea quality evaluation, but it could focus more on immediate practical application and simplify some concepts.
7. The third part is informative and solid, covering data analysis methods, but it could include more practical examples, discuss limitations, and provide a view of future developments.
8. Section 4.1 is well-structured, explaining tea quality evaluation methods with good use of practical studies, but it could better integrate tables and figures into the text and discuss limitations in more detail.
9. Sections 4.1 and 4.2 provide a detailed analysis of analytical technologies like NIR, HSI, and RMN-1H with strong examples, but they lack discussions on practical limitations and integration with the text.
10. The section discusses how technologies can be applied to tea production, but it could be more detailed about the challenges of large-scale implementation and include real-world case studies.
11. The fifth part addresses challenges and future trends, highlighting emerging technologies but could go deeper into the practical implications for the tea industry, especially for small producers.
12. The conclusion summarizes the key points well, but it could delve further into the practical implications and challenges of the discussed technologies.
13. The work is scientifically robust and based on recognized methods, but it could discuss the practical limitations and costs of technologies more thoroughly, leaving a gap in the analysis.

The article has undergone an anti-plagiarism program, and the results are attached in the file.

Comments for author File: Comments.pdf

Author Response

Response to Reviewers:

Reviewer #1:

We would like to thank you for your valuable comments, which will greatly improve the quality of this manuscript, and we also appreciate all the constructive criticism and suggestion. All the criticisms and suggestions provide helpful guidance for my manuscript revising and later paper writing. We revised all the points and summarized them below.

（1）The goal of this work is to provide a comprehensive overview of imaging and spectroscopy technologies, focusing on non-destructive evaluation of tea quality, while discussing challenges and future research directions.

The work is well-structured, with clear sections covering everything from technologies to challenges and future trends. The conclusion summarizes the information, but it could delve deeper into practical applications.

Responses:

We sincerely appreciate your insightful suggestion regarding the need for deeper discussion on practical applications, which provides helpful guidance for revising my manuscript and later paper writing. The core of this review is the technology assessment framework rather than the industrialization report. Therefore, the discussion on practical applications is not in-depth enough. And we have realized the deficiency of this review and definitely recognize the importance of application discussions. We have revised the conclusion section. The modified parts (lines 107 to 109, page 40) are as follows:

“So far, there have been some practical applications of imaging and spectroscopy technology in tea quality assessment, but there are still some technical difficulties in the process of industrialization and implementation.”

 

（2）The introduction provides a good overview of tea and the technologies, but it could offer more detail on how each technology is applied in evaluating tea quality, making it easier for readers to understand.

Responses:

       Thank you for your valuable suggestion, which will greatly make this manuscript clearer and more accessible to readers. This section mainly provides a general introduction to the overall content of the review. We have realized this section about the absence of how each technology is applied in evaluating tea quality and have made some changes to the content. To ensure the conciseness of this section, we decided not to include too many details. We hope this change will address your concerns and improve the veracity and rigor of our manuscript. The revised statement (lines 53 to 63, page 2) is shown below:

       “Among them, high-performance liquid chromatography is used to detect non-volatile substances to achieve the purpose of tea quality inspection. Protein electrophoresis is used to evaluate based on protein properties. Gas chromatography achieves the purpose of assessment by analyzing volatile substances. These chemical and physical approaches are generally reliable. However, they have limitations, including being costly, time-consuming, destructive, and occasionally inaccurate. With the growing demand for rapid, reliable, and non-destructive technologies for evaluating the quality of tea, higher-performance technologies must be developed in the modern agricultural industry to surmount the aforementioned disadvantages. One such method is the electronic nose (e-nose), a non-destructive technology used for analyzing tea quality. Essentially, it simulates the human olfactory system and assesses the quality of tea quickly and objectively by analyzing the volatile organic compounds released by it.”

（3）The work makes a positive contribution to the field, discussing innovative technologies that can improve traditional tea quality evaluation methods and providing a foundation for future research.

Although the work is relevant, it could explore the technologies in more depth in the context of tea quality, strengthening its contribution.

Responses:

Thank you sincerely for your recognition of the value of this article and your valuable opinions. We have recognized the shortcomings of this review, as well as the limitations, applications and challenges of these technologies, ensuring the depth and completeness of the review. We have made some modifications to the content to explain which technology is more suitable for different quality indicators. We also supplemented the contents, such as the limitations of the technologies, which are shown in the responses to other comments. We hope this change will address your concerns and improve the veracity and rigor of our manuscript. The modified part（Lines 326 to 338, pages 8 to 9）is shown as follows.

“Computer vision is often used to extract the external qualities such as color, texture and shape features of tea samples. This technology can capture the changes in quality information that are not easily detected by the human eye. It is commonly used to evaluate the processing stages of time series samples, quantitatively predict pigment substances (chlorophyll, theaflavins, thearubin and theabanthin), and perceive the appearance score in the sensory quality of finished tea. Spectral technology is used to quantitatively perceive the intrinsic substances related to taste in tea samples (catechins, soluble sugars, caffeine, free amino acids, and tea polyphenols). The principle is to generate characteristic absorption in the infrared band by means of the molecular bond vibration of specific functional groups. Although computer vision can obtain the feature information inside the sample, it cannot achieve the digital perception of the shape quality. Compared with computer vision, spectral imaging technology integrates the advantages of spectral technology and machine vision technology, achieving two-dimensional distribution perception of key non-volatile substances.”

 

（4）The second section clearly describes technologies applicable to tea quality evaluation, but it could focus more on immediate practical application and simplify some concepts.

Responses:

       Thank you for your careful review and useful suggestion. The second section is an overview of non-destructive technologies, which lists a series of methods and technologies applied to the quality inspection of tea. It mainly introduces the principles and concepts of these technologies, so that readers can have a clear understanding and mastery of the principles of them, and then better understand the subsequent section on application. We hope that readers can gradually understand the core content that this review intends to convey. And the application part is mainly shown in the fourth part of this review.

 

（5）The third part is informative and solid, covering data analysis methods, but it could include more practical examples, discuss limitations, and provide a view of future developments.

Responses:

This comment precisely points out the drawback of this section. According to your comment, we tried our best to improve the comprehensiveness of this section. The third part is similar to the second part, focusing on the introduction of principles. The following two sections introduce practical examples and provide a view of future developments in detail. We have realized the lack of limitations, and we have modified this section to make the discussion more in-depth and complete. This will definitely enable readers to have a deeper grasp of data processing and analysis methods. The revised content is as follows, which is also in lines 394 to 399, page 10.

“However, in image-based tea quality assessment, both supervised learning methods and unsupervised learning methods have their limitations. Supervised learning methods rely on high-quality labeled data and have weak adaptability to dynamic environments. Compared to supervised learning methods, unsupervised learning methods have a poorer ability to extract complex features. Meanwhile, there are challenges like less predictable outcomes and lower reliability in categorization.”

 

（6）Section 4.1 is well-structured, explaining tea quality evaluation methods with good use of practical studies, but it could better integrate tables and figures into the text and discuss limitations in more detail.

Responses:

This insightful comment is definitely helpful in revising our manuscript. We have realized the lack of discussion on limitations. We took this comment seriously and tried our best to revise the manuscript to make it adequate and comprehensive. We have realized the lack of discussion on limitations, and we have also better integrated the contents of tables and charts into the text. In response to your comment, the modified part (Lines 579 to 584, page 14) is as follows:

“Therefore, the application of the RGB color model based on computer vision to the appearance quality inspection of tea has certain limitations. This technology is highly susceptible to the influence of environmental lighting. At the same time, the color gamut of the RGB model cannot fully cover the entire color range perceived by the human eye. In complex environments, the adaptability of this technology is relatively poor.”

 

（7）Sections 4.1 and 4.2 provide a detailed analysis of analytical technologies like NIR, HSI, and RMN-1H with strong examples, but they lack discussions on practical limitations and integration with the text.

Responses:

Thank you for pointing out the drawback of this review. These two sections mainly introduce the application of external and internal quality inspection of tea, and list the latest research on the assessment of various characteristics of tea. Different studies have their own limitations, which is listed after the corresponding research. We have realized the lack of practical limitations and integration with the text. We have revised these two sections and the modified parts are as follows.

Lines 543 to 547, page 13:

“The acquisition of external features of tea samples is often achieved based on machine vision technology. The practical application of this technology relies on a stable external environment. For example, during the fermentation stage of black tea, due to the high humidity required in the processing link, it will affect the clarity of the imaging by machine vision technology.”

Lines 17 to 21, page 24:

“The internal quality assessment of tea samples is often achieved based on spectroscopy and spectral imaging techniques. The established models usually take spectral features as input information. However, these technologies often acquire feature information in the form of diffuse reflection, and the penetration ability for piled tea leaves is relatively weak. Further optimization is still needed in the direction of software algorithms or hardware equipment.”

 

（8）The section discusses how technologies can be applied to tea production, but it could be more detailed about the challenges of large-scale implementation and include real-world case studies.

Responses:

Thank you for your valuable suggestion, which will make our manuscript more comprehensive and in-depth. The core of this review is the technology assessment framework rather than the industrialization report. Therefore, the part of this review involving real-world case studies is relatively less. The part related to the challenges is elaborated in detail in the fifth section, and we have supplemented the challenges of large-scale implementation in this section. We hope this change will address your concerns and improve the veracity and rigor of our manuscript. The modified part (lines 79 to 85, page 38) is shown as follows:

“Although the application of non-destructive technology in tea quality assessment has broad prospects, its large-scale implementation still faces multiple challenges. Due to the poor universality of the existing models and the lack of unified standards for data formats, large-scale implementation faces obstacles. At the same time, the high investment and maintenance costs of the equipment also need to be taken into consideration. Therefore, to broaden the scope of these imaging and spectroscopy techniques, the technical challenges existing in each imaging and spectroscopy technique should be solved.”

 

（9）The fifth part addresses challenges and future trends, highlighting emerging technologies, but could go deeper into the practical implications for the tea industry, especially for small producers.

Responses:

We have realized the inadequacy of this section and tried our best to make modifications. This suggestion will make this section more in-depth and comprehensive, enabling readers to have a deeper understanding of the tea industry， especially for small producers. I hope you are satisfied with the revised version. The revised statement (lines 23 to 32, page 37) is shown below:

“These technologies can achieve rapid grading and precise prediction of tea, enhancing the efficiency and accuracy of quality inspection. At the same time, it can optimize resource utilization and reduce production costs. For some small businesses, the emergence of portable spectral devices has made real-time field detection possible, eliminating the need to rely on laboratory equipment and lowering the technical threshold. However, there are also some challenges at present. Most of these technologies are not convenient for small businesses. Despite significant technological advantages, small businesses still have to confront problems such as high equipment costs and insufficient technical training.”

 

（10）The conclusion summarizes the key points well, but it could delve further into the practical implications and challenges of the discussed technologies.

Responses:

Thank you for your careful review and useful suggestion. Since the summary needs to be concise and to the point, we mentioned very little about the practical implications and challenges of the discussed technologies. And we have realized the deficiency of this review and definitely recognize the importance of practical implications and challenges of the discussed technologies. We have revised the conclusion section. The modified parts (lines 107 to 118, page 39) are as follows:

“So far, there have been some practical applications of imaging and spectroscopy technology in tea quality assessment, but there are still some technical difficulties in the process of industrialization and implementation. For instance, in tea processing, rolling machines operate in enclosed environments, and especially aroma-developing machines are not only enclosed but also have extremely high internal temperatures, making it difficult for digital information sensing devices to effectively integrate with existing equipment. Furthermore, due to the uneven surface of stacked tea samples, errors are prone to occur during digital information acquisition. Therefore, in future research, we believe that developing flexible digital information devices that can be integrated with closed tea processing equipment, and addressing the errors in digital information collection caused by surface unevenness at the algorithmic level, will be important research directions.”

 

（11）The work is scientifically robust and based on recognized methods, but it could discuss the practical limitations and costs of technologies more thoroughly, leaving a gap in the analysis.

The article has undergone an anti-plagiarism program, and the results are attached in the file.

Responses:

This valuable comment helpfully provides guidance for revising our manuscript and later paper writing. We took this comment seriously and tried our best to revise the manuscript to make it adequate and comprehensive. Regarding the practical limitations and costs of technologies, we have made adjustments to the corresponding contents by referring to the previous suggestions to ensure the comprehensiveness and depth of this review. We hope this change will address your concerns and improve the veracity and rigor of our manuscript. The modified content is displayed in the responses to the previous opinions.

 

Thanks again for your careful read and thoughtful comments on our manuscript, I hope you are satisfied with the revised version. However, if there are any other questions or suggestions, we are willing to revise them again.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The contents of the manuscript do not match. The authors do not describe studies using spectroscopic methods such as UV-Vis or ATR-FTIR. The title promises more than is in the content. The material is too long-winded. At times very general and at other times the degree of detail is enormous. Tea is a cheap product, so extolling the virtues of non-destructive methods makes no sense. We learn about the fact that it will be about non-destructive methods too late. Analyzing, for example, the water content of dried tea takes up to 10 minutes (using a thermobalance) writing that it can be done quickly with optical methods does not convince me. The accuracy of the optical method for inhomogeneous material is subject to large error, so the use of such QC methods is severely limited. If the paper is supposed to be on the topic of “Recent advances and applications of imaging and spectroscopy technologies for tea quality assessment” then I don't agree with such a positioning, because the long analysis time of GC and HPLC is given as an advantage. Unfortunately, these methods (chromatography) have significantly greater advantages than their disadvantages (analysis time), which the authors forgot.

Comments for author File: Comments.pdf

Author Response

Response to Reviewers:

Reviewer #2:

The contents of the manuscript do not match. The authors do not describe studies using spectroscopic methods such as UV-Vis or ATR-FTIR. The title promises more than is in the content. The material is too long-winded. At times very general and at other times the degree of detail is enormous. Tea is a cheap product, so extolling the virtues of non-destructive methods makes no sense. We learn about the fact that it will be about non-destructive methods too late. Analyzing, for example, the water content of dried tea takes up to 10 minutes (using a thermobalance) writing that it can be done quickly with optical methods does not convince me. The accuracy of the optical method for inhomogeneous material is subject to large error, so the use of such QC methods is severely limited. If the paper is supposed to be on the topic of “Recent advances and applications of imaging and spectroscopy technologies for tea quality assessment” then I don't agree with such a positioning, because the long analysis time of GC and HPLC is given as an advantage. Unfortunately, these methods (chromatography) have significantly greater advantages than their disadvantages (analysis time), which the authors forgot.

Responses:

Thank you for your positive feedback and encouragement. We would also like to thank you for your valuable comments, which will greatly improve the quality of this manuscript. All the criticisms and suggestions provide helpful guidance for revising our manuscript and later paper writing. We would like to provide explanations for the suggestions, and the details are as follows. We revised all the points and summarized our responses in the attached file.

Tea is one of the oldest beverages in the world, renowned worldwide for its unique flavor and multiple health benefits. Rich in functional components such as tea polyphenols, amino acids, and caffeine, tea has been proven to possess various health-promoting properties, including antioxidant, anticancer, anti-aging effects, and stimulant effects on the central nervous system. First of all, we would like to explain that tea is an economic crop rather than a cheap one. As we know, some high-quality famous and excellent teas can even be sold at prices exceeding 10,000 yuan. Therefore, it is necessary and meaningful to extol the advantages of non-destructive methods in tea quality inspection. We have learned that some unscrupulous merchants add flavoring to tea to enhance its taste and aroma quality. They also pass off tea from other regions as that from places with geographical indications, such as West Lake Longjing, and sell it at high prices. These behaviors all infringe upon the rights and interests of consumers. Although the content information of volatile and non-volatile substances can be analyzed through other instruments in the experiment, this requires professional scientific researchers to conduct the analysis. Consumers cannot make decisions on the quality of tea they purchase in the first place. Therefore, developing non-destructive testing equipment for tea origin and adulteration specifically for consumers is of great significance for safeguarding their rights and interests.

Secondly, regarding the opinions on the technologies used in this article, we found that during the withering stage of fresh leaves, even though a moisture meter was used for detection, a single measurement still required at least 20 minutes. Besides, if the moisture content of fresh leaves needs to be measured repeatedly, it will lead to excessive wilting. In addition, tea-making masters often judge the processing status based on their own experience, resulting in a relatively low degree of precision in processing. Non-destructive testing technology, which combines the characteristics of rapidity and accuracy, can also digitally represent the experience of tea-making masters, providing better guidance for actual production.

Moreover, as for the suggestions regarding the content of this review, we admit that there are deficiencies in the expression of some parts. However, in order to ensure the comprehensiveness and academic value of the review, we made selection and rejection of the relevant contents during the writing process. Through the selected contents, readers can have a clear and definite understanding of the core conveyed in this review. We tried our best to make this review as detailed and comprehensive as possible to enable readers to understand the latest progress and applications in this field.

Thanks again for your careful read and thoughtful comments on our manuscript, I hope you are satisfied with the revised version. However, if there are any other questions or suggestions, we are willing to revise them again.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Most of my comments have been taken into account for which I thank the authors very much. What I do not find acceptable is the very high degree of phrases taken from other works. Initially it was 20% (that's a lot). Now it is as high as 29% (according to iThenticate). In my opinion, this is unacceptably high. Please rewrite the manuscript so that it is an independent work and not a conglomeration of other works.

Author Response

Response to Reviewers:

Most of my comments have been taken into account for which I thank the authors very much. What I do not find acceptable is the very high degree of phrases taken from other works. Initially it was 20% (that's a lot). Now it is as high as 29% (according to iThenticate). In my opinion, this is unacceptably high. Please rewrite the manuscript so that it is an independent work and not a conglomeration of other works.

Responses:

Thank you for your careful review and useful suggestions, which will greatly make this manuscript more academically valuable. We received the iThenticate Report and carefully adjusted the content of the review based on it. We hope this change will address your concerns and improve the veracity and rigor of our manuscript.