Bibliometric Analysis of Current Status of Circular Economy during 2012–2021: Case of Foods

: Food is usually recognized as a limited resource in sustainability, recognized by the United Nations (UN) Sustainable Development Goal (SDG) 2, which aims to achieve zero hunger. It is expected that the circular economy (CE) can improve processes related to food production. The objective of the present study was to apply a bibliometric approach using VOSviewer visualization software as a research tool to analyze the relevant literature from the Scopus database in the ﬁeld of circular economy and its relation to improvements in food issues throughout 2012–2021. A total of 1316 articles were analyzed. Italy was the most productive country with 313 articles, with Wageningen University & Research the organization with the most publications with 39 articles. The top 10 institutions originated from Italy, The Netherlands, France, and Denmark. Sustainability was the most productive journal with 107 articles. Bioresource Technology had the highest average citation frequency (44.68). The study helps initiate investigations to adapt the results obtained and create new strategies for increasing food circular economy efforts.

In terms of a sustainable approach, food manufacturers generate various ecological effects [13][14][15][16][17][18][19][20][21], and it the need for a sustainable process is recognized [22][23][24][25][26][27][28][29][30][31][32], including the production of CO 2 [33]. Approximately 40% of the food destined for human consumption ends up as waste during the manufacturing [34] and consumption process [35]. This loss can be explained by the abundant purchase of food that is stored by people but not consumed on time, which generates the waste food described above. Food manufacturing generates up to 30% of greenhouse gas (GHG) emissions [36]. It is estimated that food manufacturers in the United States generate 39.82 million tons of food waste annually, while the residential sector generates 23.95 million tons of food waste, and restaurants 17.09 million tons [37]. Therefore, the need arises to change how the various processes involved in obtaining food and its consumption are carried out. It must be possible to optimize each process involved in food systems. In this scenario, the circular economy (CE) offers a possibility of making the processes eco-efficient. A CE contributes to closing the cycle of materials and

Materials and Methods
The bibliometric analysis was conducted using the Scopus database, a comprehensive database suitable for analysis [93]. Terms, Boolean operators, and parentheses were used to create the search: "TS = ("circular economy"*) AND (food*))" in TITLE-ABS-KEY. The period was specified as the 2012-2021 period. All data were collected on 31 December 2021, to avoid changes in the number of publications and citations. The type of publication was the journal. In total, 1316 articles in journals were considered for analysis. All the search results were exported in tab-delimited format, which included bibliographical information such as titles, authors, journals, institutions, keywords, publication years, and abstracts for further analysis and visualization using bibliometric analysis software. VOSviewer (version 1.6.17) was utilized to evaluate the status of research and hot spots to enable visual analysis and graphic representation of co-occurrence work clustering of the published literature by country, research institution, keywords, number of citations, etc. [94,95]. Figure 1 shows the research design. This study analyzed the number of publications according to year, significant countries, affiliations, journals, highly cited papers, and keywords; annual variation trends; and the highly cited literature using Microsoft Excel 2019. VOSviewer was used for the analysis of the co-authorship relationship and co-occurrence relationship.
the Scopus database in the field of circular economy and its relation to improvements food issues throughout 2012-2021 to present the current state of research in this field a provide references for further investigation. Current bibliometric analysis has describ the research trends in different fields that previous studies have focused on [91,92].
The paper is structured as follows: Section 2 presents the methodology of bib metric analysis. The results are presented in Section 3. The discussion is shown in Sect 4. Finally, the conclusions are presented in Section 5.

Materials and Methods
The bibliometric analysis was conducted using the Scopus database, a compreh sive database suitable for analysis [93]. Terms, Boolean operators, and parentheses w used to create the search: "TS = ("circular economy"*) AND (food*))" in TITLE-ABS-K The period was specified as the 2012-2021 period. All data were collected on Decem 31, 2021, to avoid changes in the number of publications and citations. The type of pu cation was the journal. In total, 1316 articles in journals were considered for analysis. the search results were exported in tab-delimited format, which included bibliograph information such as titles, authors, journals, institutions, keywords, publication years, a abstracts for further analysis and visualization using bibliometric analysis softwa VOSviewer (version 1.6.17) was utilized to evaluate the status of research and hot sp to enable visual analysis and graphic representation of co-occurrence work clustering the published literature by country, research institution, keywords, number of citatio etc. [94,95]. Figure 1 shows the research design. This study analyzed the number of p lications according to year, significant countries, affiliations, journals, highly cited pap and keywords; annual variation trends; and the highly cited literature using Micros Excel 2019. VOSviewer was used for the analysis of the co-authorship relationship and occurrence relationship.

Growth Trend of Publications
As shown in Figure 2, the number of publications on circular economy and foo indexed in Scopus presented an increasing scenario. The relationship between the ann number of publications and year was fitted with an exponential regression model betw 2017 and 2021 where the increase was notable. The equation is shown to predict the nu ber of articles in the future. The R 2 is the relative predictive power of the exponen model. It can be observed that circular economy and food publications increased nota between 2017 and 2021. It can be predicted that the food circular economy field will b research hotspot for researchers in the coming years. It will be essential to analyze

Growth Trend of Publications
As shown in Figure 2, the number of publications on circular economy and foods indexed in Scopus presented an increasing scenario. The relationship between the annual number of publications and year was fitted with an exponential regression model between 2017 and 2021 where the increase was notable. The equation is shown to predict the number of articles in the future. The R 2 is the relative predictive power of the exponential model. It can be observed that circular economy and food publications increased notably between 2017 and 2021. It can be predicted that the food circular economy field will be a research hotspot for researchers in the coming years. It will be essential to analyze the increase in articles from Scopus. It will be interesting for future studies to confirm the trends using the Web of Science. increase in articles from Scopus. It will be interesting for future studies to confirm the trends using the Web of Science.

Publication Distribution of Countries
The 1316 articles in the Scopus database indicate that 91 countries contributed to the circular economy and food publication records. Table 2 shows the top ten countries

Publication Distribution of Countries
The 1316 articles in the Scopus database indicate that 91 countries contributed to the circular economy and food publication records. Table 2 shows the top ten countries ranked by the number of total publications, total cited frequency, average cited frequency per paper, and the country's h-index [96]. The top 10 countries represented 88.90% of the total number of publications. VOSviewer software was used to visualize the co-operative relationships among the top 10 productive countries and regions from 2012 to 2021, and the results are shown in Figure 3. A circle represents each country, and its size depends on the number of publications produced by that country. The curve connecting the two circles represents a co-operative relationship between the two linked countries. The thicker the curve, the stronger the collaborations between the two countries. The circle's color in the visualization networks is determined by the cluster to which the country belongs. The distance between circles implies the degree of co-operation between countries or regions. As shown in Figure 3, there were close co-operative relations among all countries. Italy showed the most co-operative relations, co-operating with 66 countries. Of all the countries that collaborated, Italy and Spain had the most significant strength of co-operation, which illustrates that the two countries had the closest co-operation.

Publication Distribution of Institutions
In total, 157 institutions were involved in the 1316 publications related to circular economy and foods during 2012-2021. The top 10 most productive institutions in total publication numbers are shown in Table 3. The top 10 institutions originated from four countries-Italy, The Netherlands, France, and Denmark-and accounted for 224 publications (15.68%). Italy, the United Kingdom, Spain, China, and Portugal were the 10 most productive countries. However, only Italy appeared in the top 10 most productive institutions. The Wageningen University & Research reported the highest number of publications, with 39 articles accounting for 2.96% of the total. The total frequency of citations was also the highest, which was 12,832. From the total number of publications, citation frequency, and h-index, the Wageningen University & Research has made outstanding contributions to circular economy and foods. VOSviewer software was used to visualize the co-operative relationships among the research institutions, with 1316 articles published in circular economy and foods.
circles implies the degree of co-operation between countries or regions. As shown in ure 3, there were close co-operative relations among all countries. Italy showed the m co-operative relations, co-operating with 66 countries. Of all the countries that colla rated, Italy and Spain had the most significant strength of co-operation, which illustra that the two countries had the closest co-operation.    Table 4 lists the top 10 most active journals concerning circular economy and food. From 2012 to 2021, 439 articles were published in the top 10 journals in this field, accounting for 33.35% of the total articles. The average impact factor in the past five years was 6.17. Sustainability was the most productive journal, with 107 articles accounting for 8.13% of the total number of articles, and its five-year average impact factor was 3.473. It was followed by the Journal of Cleaner Production and Science of the Total Environment, with 96 and 48 articles, respectively. The articles published in Bioresource Technology had the highest

The Most Highly Cited Articles
The top 10 highly cited publications in circular economy and foods from 2012 to 2021 were analyzed by the total citations and the institutions of origin, and the results are shown in Table 5. Of all the highly cited articles, three were from developing countries (Saudi Arabia, India, and Cyprus), and the rest were from developed countries. The most highly cited article was "Current options for the valorization of food manufacturing waste: A review", published in the Journal of Cleaner Production in 2014, with 514 citations [97]. This article was a review article summarizing the use of food waste from food manufacturing in other industries, such as the pharmaceutical industry, as a potential symbiosis. The second was entitled "Sustainable supply chain management and the transition towards a circular economy: Evidence and some applications", published in Omega in 2017, with 375 citations [98]. This article presented two case studies from different process industries (chemical and food) and compared the performance of traditional and circular production systems. It evaluated direct and indirect emissions, recovered waste, virgin resource use, and carbon maps. It is worth noting that among these top 10 highly cited publications, two articles were reviewed, which indicates that comprehensive reviews of concepts, cases, and factors are starting to be summarized for subsequent research. From the analysis of highly cited literature, cases from various countries are being presented and assessed, such as the case of landscape burning in Australia [99], the development of eco-industrial parks in China [100], the Chinese import ban and its impact in the plastic waste trade [101], and a food waste biorefinery in India [102]. Table 6 shows the more relevant authors of articles focused on circular economy and food, indicating their institutional filiations, countries, and total H-index

Keyword Analysis
A keyword analysis is essential to identify research hotspots and the direction the field is moving. VOSviewer was used to generate a keywords co-occurrence network that shows the connection and weightage of the 100 most high-frequency author keywords in circular economy and foods. It established five co-occurrences, at least for the analysis. As shown in Figure 4, nine clusters were identified. The first cluster comprises 12 items related to industrial processes such as bioenergy, biogas production, composition, critical review, environmental assessment, influence, life cycle assessment (LCA), Malaysia, role, sustainable development, tool, and urban design agriculture.

Keyword Analysis
A keyword analysis is essential to identify research hotspots and the direction the field is moving. VOSviewer was used to generate a keywords co-occurrence network that shows the connection and weightage of the 100 most high-frequency author keywords in circular economy and foods. It established five co-occurrences, at least for the analysis. As shown in Figure 4, nine clusters were identified. The first cluster comprises 12 items related to industrial processes such as bioenergy, biogas production, composition, critical review, environmental assessment, influence, life cycle assessment (LCA), Malaysia, role, sustainable development, tool, and urban design agriculture. The second cluster comprises 11 items related to the type of amino acids and compounds, such as a benefit, food, characterization, coffee ground, design, effect, evaluation, food waste biorefinery, lactic acid, poly, and synthesis. The third cluster comprises 11 terms related to countries and processes such as barrier, challenge, China, economy, European Union, evidence, food supply chain, implementation, Italy, Poland, and transition. The fourth cluster comprises 10 items related to the manufacturing process: agriculture, The second cluster comprises 11 items related to the type of amino acids and compounds, such as a benefit, food, characterization, coffee ground, design, effect, evaluation, food waste biorefinery, lactic acid, poly, and synthesis. The third cluster comprises 11 terms related to countries and processes such as barrier, challenge, China, economy, European Union, evidence, food supply chain, implementation, Italy, Poland, and transition. The fourth cluster comprises 10 items related to the manufacturing process: agriculture, bioactive compound, cheese, circular economy approach, extraction, gain, incorporation, reuse, sewage sludge, and wastewater. The fifth cluster comprises 10 items related to waste management, such as bioconversion, bio waste, feed, food packaging, food waste management, hermetic, insect, larvae, optimization, and protein. The sixth cluster comprises nine items linked to natural resources such as anaerobic digestate, Brazil, cultivation, effectiveness, industrial waste, microalgae, nitrogen, phosphorus, and vegetable. The seventh cluster comprises nine items linked to agriculture, including circular economy strategy, city, comparison, covid, framework, organic fertilizer, organic waste, soil, and waste management. The eighth cluster comprises seven items related to the management of the circular economy model, circular economy perspective, food security, food system, implication, plant, and water. Figure 5 shows a density map of co-occurrence. The keywords of research have changed over time, according to VOSviewer. The usual keywords were reuse and food packaging. The most common keywords are food packaging, food waste, and biowaste. bioactive compound, cheese, circular economy approach, extraction, gain, incorporation, reuse, sewage sludge, and wastewater. The fifth cluster comprises 10 items related to waste management, such as bioconversion, bio waste, feed, food packaging, food waste management, hermetic, insect, larvae, optimization, and protein. The sixth cluster comprises nine items linked to natural resources such as anaerobic digestate, Brazil, cultivation, effectiveness, industrial waste, microalgae, nitrogen, phosphorus, and vegetable. The seventh cluster comprises nine items linked to agriculture, including circular economy strategy, city, comparison, covid, framework, organic fertilizer, organic waste, soil, and waste management. The eighth cluster comprises seven items related to the management of the circular economy model, circular economy perspective, food security, food system, implication, plant, and water. Figure 5 shows a density map of co-occurrence. The keywords of research have changed over time, according to VOSviewer. The usual keywords were reuse and food packaging. The most common keywords are food packaging, food waste, and biowaste.

Discussion
Recent studies have reported novel approaches to processing food waste and promoting a greener environment and circular economy. For instance, Mateus et al. [103] evaluated the combination of pretreatment processes and primary treatments with bentonite impregnated with magnetic nanoparticles to reuse wastewater from the food industry. Leong et al. [104] evaluated a waste biorefinery as a sustainable bio-based circular economy and, therefore, as a means for promoting a greener environment. Cortes et al. [105] evaluated the skipjack tuna (Katsuwonus pelamis) value chain within a canning industry, demonstrating that the multiproduct strategy applied to the canning sector is ecologically viable. Kurniawan et al. [106] reviewed the nutrient content of wastewater that supports plant growth and the performance of constructed wetlands (CA) for nutrient uptake using macrophytes as treatment agents. Another critical review was carried out by O'Connor et al. [107], which examined different slag generation processes in steel plants,

Discussion
Recent studies have reported novel approaches to processing food waste and promoting a greener environment and circular economy. For instance, Mateus et al. [103] evaluated the combination of pretreatment processes and primary treatments with bentonite impregnated with magnetic nanoparticles to reuse wastewater from the food industry. Leong et al. [104] evaluated a waste biorefinery as a sustainable bio-based circular economy and, therefore, as a means for promoting a greener environment. Cortes et al. [105] evaluated the skipjack tuna (Katsuwonus pelamis) value chain within a canning industry, demonstrating that the multiproduct strategy applied to the canning sector is ecologically viable. Kurniawan et al. [106] reviewed the nutrient content of wastewater that supports plant growth and the performance of constructed wetlands (CA) for nutrient uptake using macrophytes as treatment agents. Another critical review was carried out by O'Connor et al. [107], which examined different slag generation processes in steel plants, their physicochemical characteristics related to their beneficial use as a soil amendment, and ecological implications and risk assessment of their use in agricultural soils. Mohammadhosseini et al. [108] determined the potential of using polypropylene-type plastic food trays as low-cost fibers to improve the strength and durability of concrete; they found that the inclusion of these fibers decreased the workability of fresh concrete and the compressive strength. Badgett and Milbrandt [109] proposed cost-benefit models that described the economic favorableness of managing food waste by state: landfill, composting, anaerobic digestion, incineration, and the production of biofuels through hydrothermal liquefaction. Regardless of these novel approaches, there is still a lack of publications focused on some specific topics, such as the case of fast-food restaurants as reported by the European Food Agency [110], GreenBiz [111], and the Environmental Defense Fund [112]. As research in circular economy and foods expands into new fields, it needs not to forget about food insecurity and the presence of residual pesticides in foods and their corresponding waste [2]. In terms of investments, Forbes [98] recognizes that a circular economy can serve as an opportunity for the growth of companies such as bioplastic companies [113], evaluating foreign direct investment [114], impacting the price [115], and using blockchain [116]. Our study has identified the most critical articles on circular economy (CE) and foods during 2012-2021. Since 2017, it has been possible to observe an evident growth in publications addressing the circular economy and its relationship with food. The number of publications on CE and foods is expected to continue increasing. However, not only will the number of publications increase, but various aspects of CE can be addressed to contribute to the improvement in food production and its use, thus contributing to achieving the United Nations Sustainable Development Goal (SDG) 2: zero hunger. The current bibliometric analysis reported that China, along with various European countries, is the main one developing CE and food research. It was recognized that Italian universities play a leading role in CE and food research, so it can be of strategic value to generate collaborative projects with these universities since they have research experience in this field and resources to be optimized for further research. The list of the 10 articles with the most citations offers an excellent guide to formulate new research that can further analyze these topics. Additionally, policymakers should consider these articles to generate implementation proposals with specific funds and research agencies to expand their related priority issues. Knowing the major research trends, further research can be guided to achieve innovative results and publications.
The current study reported a constant growth in the topic, as previously described by Esposito et al. [88], Hamam et al. [89], and Oliviera et al. [90]. Furthermore, it was reported that the journals Sustainability and the Journal of Cleaner Production have the highest number of published research articles. In addition, the top 10 remain the following journals: Science of The Total Environment, Foods, Resources Conservation and Recycling, Molecules, Waste Management, and Energies. On the other hand, it has been recognized that Europe continues to be the region where the most significant amount of research on circular economy and food is carried out [88], as can be seen in Table 2, where 8 of the 10 countries are European. The present study and that reported by Oliveira et al. [90] coincide in reporting that Italy is the country with the highest number of publications on circular economy and food. In the case of institutions, the top 10 are European institutions. Finally, in the case of authors with the most publications on circular economy and foods, 8 out of 10 are European.
The current evidence shows that the circular economy is a topic that is growing very fast, and the focus on food is a very active topic. The information can help recognize authors who are the research leaders in circular economy and foods and can evaluate which trends for new research and the development of foods are based on new technology.
The current study presents some limitations; for instance, it only uses a single database to retrieve the information. Publications outside the Scopus database and citations outside the Scopus-registered journals were neither included nor analyzed, which may have excluded some influential articles. In addition, some of the documents retrieved were weakly related to circular economy and food. Manual screening is difficult, time-consuming, and highly subjective. Therefore, further research should use multiple databases to retrieve publications and use text mining tools to filter results, which would help improve the analysis's accuracy. Overall, these results generated by bibliometric analysis reveal the global research trends in circular economy and food. Thus, this research helps researchers understand the development trends and themes in the circular economy and food and guides future research.

Conclusions
SDG 2 requires a multisectoral effort to contribute sustainably to achieving the zero hunger indicators necessary to optimize product and food consumption. All the bibliometric information reviewed allows us first to know that research in circular economy and food is increasing and that researchers from China and European countries are the ones with the most published articles. At the same time, the institutions of those same countries have the most significant number of publications related to the topic addressed in this research.
The research and development areas identified in this study reveal important information since they help evaluate all global research trends to improve their processes. Knowing the areas also helps initiate investigations to adapt the results obtained in other jurisdictions and to contact the researchers of these studies to understand the results better and to bring to reality the improvements that science disseminates.
The present study has made it possible to show that research in the circular economy and food has an exponential growth, which shows the greater interest of research centers around investigating more about it since food is a dynamic area in which, through technology, the processes of the preparation and management of food waste are improved. Future research must be focused on characterizing the type of research most described in food items. Likewise, it is helpful that an analysis can be generated by geographical area or even by grouping the countries by economic blocs or trade agreements such as the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (CPTTP) or the Organization for Economic Co-operation and Development (OECD).

Data Availability Statement:
The data presented in this study are available on request from the corresponding author.

Conflicts of Interest:
The authors declare no conflict of interest.