A bibliometric study about unconventional food plants

Data on unconventional food plants (UFP's) are still scarce in the literature, however the aim of this study is to identify the papers published on unconventional food plants, which topics have been studied over the years, and which countries stand out for research, through the bibliometric analysis tools. A search was conducted in the Web of Science Core Collection (WoS) database, the dataset of 25 retrieved articles published between 2008, and March 16, 2022 was analyzed using VOSviewer and the Bibliometrix R package. Brazil was the country with the highest number of publications and the ten most cited articles worldwide are all by Brazilians. The co-occurrence map with the keywords generated six main clusters. Despite the benefits studied, there are few papers on UFP's. Bibliographic mapping offers the possibility of obtaining a large amount of bibliographic information, making it more manageable, objective and practical to serve scientific policy makers, institutions and research managers.


Introduction
Scientometrics or bibliometric analysis is a scientific statistical and quantitative evaluation of publications within a defined topic, based on citation index data. It can be used to identify articles of interest, detect research foci, locate the most relevant journals in the area under study, and analyze interrelationships between authors from different institutions and countries (Feng et al., 2021). This method organizes the existing literature, showing its trajectory of publications, as well as traditional and emerging fields of research (Sharifi et al., 2021). Bibliometric studies are necessary for assessing the current state of research, as well as the contributions of researchers and countries in knowledge areas (Giraldo et al., 2019).
Plants that have one or more edible parts, spontaneous growth and without the use of chemical additives, native or exotic, that are not part of everyday food, are called unconventional food plants (UFP's) (Kinupp & Lorenzi, 2014). This definition encompasses most wild and regional food plant species, whose knowledge and consumption is largely in small rural communities, far from large urban centers. Despite their use in small communities as food and medicinal application for several years (Leal et al., 2018), few studies on UFP's are found in the scientific literature.
To date, there are no bibliometric studies on UFP's available. Given the above, the objective of this research is to identify the works published on unconventional food plants, which topics have already been studied over the years and in different countries. Research trends were identified by bibliometrics and quantitative methods that analyze scientific publications were used as an information process. This study can provide strategic directions and justification for the execution of future research.

Data collection
A literature search was performed in the Web of Science Core Collection (WoS) online database updated through March 16, 2022, the search strategy was using the term "unconventional food plants". The search was performed on studies that mentioned the term in any searchable field (default option in WoS). No language or date restrictions were applied. The documents were exported in "full records and cited references" tab format. WoS was used instead of Scopus because of the quality of the data for a bibliometric search due to the standardization of cited references, for example (Zammarchi & Conversano, 2021).

Data analysis and visualization
From the data exported from the Web of Science Core Collection and with the help of the Bibliometrix package version 3.1 in R version 4.1.3 the countries with the highest number of published papers and/or citations were identified (based on the affiliation of the corresponding authors as well as other authors) and the collaboration network of the countries was plotted. The most cited papers, the types of papers, and the categories in which they have been published were also described.
To create the bibliometric maps, the complete citation records were exported from WoS to be treated by the software VOSviewer version 1.6.18. In the co-occurrence map, the assignment of terms to the same cluster depends on their cooccurrence in the title or abstract of the publications. A cluster formed by terms with the same colors represents a research theme in which one or more research topics can be identified. In the annual terms map, the color of a term indicates the average publication year of all publications in which the term occurs (Cecchini et al., 2020). The VOSviewer also provides the option to exclude data by omitting terms deemed not relevant to the analysis. When using this feature of the software, the terms "l." and "diversity" that could be used redundantly (an example: variety) were omitted.

Numerical data of publications on unconventional food plants
A total of 25 documents (21 journal articles, one early access article, two review articles and one early access review article) published from 2008 to March 16, 2022, were identified. Analysis of the search categories performed with the WoS analytical tool showed that the most represented area was "food science technology" (48%), followed by "agronomy" (20%) and "plant sciences" (20%). The annual growth in scientific production was 10.41% and 2021 was the year with the highest number of published papers, with a total of 12 papers ( Figure 1). The ten most cited papers worldwide, are all Brazilian authors (Table 1). Kinupp and De Barros (2008)

evaluated and
identified 69 UFP's species native to the metropolitan region of Porto Alegre, located in the state of Rio Grande do Sul, Brazil.
The authors concluded that several UFP's species showed high values of protein and minerals, but the vast majority of these species remain unknown or underutilized. It is worth mentioning the work done by Dr. Valdely Ferreira Kinupp, who, in addition to having one of the most cited papers, has been working on the identification of UFP's for over ten years and is the author of the book entitled "Plantas Alimentícias Não Convencionais (PANC) no Brasil" coauthored with Professor Harri Lorenzi, published in 2014 by Plantarum, where dozens of unconventional food species were identified, with information on morphological aspects, botanical identification, and general and culinary use of each species. The information provided in this book serves as a guide and reference for future research. Research, Society and Development, v. 12, n. 7, e13512742576, 2023 (CC BY 4.  (Pteridaceae), submitted to different treatments. The authors concluded that the daily intake of C. pteridoides could contribute to mineral supplementation, besides diversifying existing crops and cooperating to sustainable agriculture.
In order to investigate the phytochemical profiles and the in vitro anti-inflammatory and antioxidant activities of the species Hypochaeris chillensis, Emilia fosbergii and Emilia sonchifolia. Peisino et al. (2020) found that all species studied, exhibited promising bioactive compounds capable of neutralizing free radicals, controlling oxidative stress and modulating the inflammatory process. Source: Bibilometrix (2022). Figure 2 represents the collaboration network between the countries. Brazil stands out as the country with the largest number of publications with 24 papers, two in collaboration with Portugal and one paper in collaboration with Serbia. Portugal also published one paper in collaboration with Serbia. Brazil is a country of vast territorial extension and that has a rich diversity of plant species, which has increasingly attracted the interest of researchers, which corroborates with the high number of publications and citations.

Co-occurrence map
The frames represent the terms, the size of the frame is proportional to the number of articles in which the term was retrieved, the thickness of the lines between the frames represents the strength of correlation between two terms. The strongly correlated terms are close to each other and are automatically assigned to the same cluster. A total of 22 terms and six main clusters of strongly related terms were identified by VOSviewer (Figure 3). The yellow cluster contains the main search keyword "unconventional food plants" and is related to the analyses that have been most performed on UFP's chromatographic analyses and techniques employed to evaluate antioxidant capacity.
Chromatographic techniques have a high sensitivity and precision in the identification of compounds, especially phenolic compounds, which may exert antioxidant functions. In vitro tests, such as DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging, is one of the most widely used methodologies to evaluate antioxidant capacity or activity. It is observed that the term "antioxidant activity" (cyan blue cluster) is very close to the term "unconventional food plants" and has a strong link with the term "bioactive properties". Bioactive properties is the definition for non-nutritive substances present in foods, which possess chemical and biological properties whose effects provide benefits to human health (Braicu et al., 2022). From the articles identified, the authors concluded that the UFP's studied have high antioxidant capacity and that the consumption of these vegetables can lead to improvements in the health status of consumers, which justified the proximity of such terms on the map.
The dark blue cluster refers to ethnobotanical studies identified in the search, about the research work on the variety of UFP's present in a given region and how they are used by the population, coupled with the identification studies of phenolic compounds classified as flavonoids. Flavonoids are a group of hydroxylated phenolic compounds recognized as important free radical scavengers (Braicu et al., 2022).
The green cluster is related to the existing biodiversity of UFP's the wide variety of plant species and which, depending on the region are known as "wild edible plants". Chemical composition analyses again identified the presence of bioactive compounds. The consumption of UFP's appears as an alternative to maintain food security, since they are plant species that grow spontaneously, i.e., available to the population without the need for implementation of large planting systems and at high cost; native to the region rescuing and respecting traditional and cultural habits; besides being rich in nutrients that promote the improvement and/or maintenance of the individual's nutritional status.
The purple cluster is represented by the terms "food", "vegetables" and "sustainabillity". Research shows that UFP's can be used for the development of new and healthy food products, as well as promoting a more sustainable food production chain.
The term "neophobia" together with the term "ora-pro-nobis", both present in the red cluster, is justified by the work conducted by Mazon et al. (2020). The authors reported the participants' rejection of the new product made, an ice cream using mucilage from ora-pro-nobis leaves.
Despite the benefits studied, consumption and knowledge about UFP's is still restricted to small rural communities, far from large urban centers. The consumption of leaves and/or flowers of plant species that are not present in our eating routine causes a certain repulsion for these foods. This behavior in rejecting or refusing to eat/experiment new foods is defined as neophobia (Mattavelli & Rizzoli, 2022).

Final Considerations
Through the bibliometric analysis it is possible to state that the scientific interest in unconventional food plants began in 2008, a relatively new area of research, with a large contribution from Brazilian researchers and studies. In addition to species identification, characterization and studies to determine bioactive compounds and antioxidant capacity are the main research topics. Despite the benefits studied, UFP's are still underutilized and poorly disseminated, especially in large urban centers.
In view of the above, there is a need for further studies on such plant species. Topics on nutritional characterization; the medicinal potential use of the plants; whether there is toxicity or any risk in consuming such plant species; what are the best strategies to popularize the consumption of UFP's in large urban centers; the use of UFP's in the formulation of new products.
All these questions serve as directions for future research.