Functional Properties of Tilapia Collagen, a Systematic Review Propriedades Funcionais Colágeno de Tilapia, Revisão Sistemática Propiedades funcionales colágeno de tilapia, una revisión sistemática

This systematic review aimed to list the functional properties attributed to collagen obtained from tilapia in scientific studies. The results showed that the antioxidant property is related to the form in which the collagen is presented and the method of antioxidant activity evaluation. It was observed a greater antioxidant activity in the collagen hydrolysate extract obtained from the skin, which plays an important role in the skin chronological aging and in the inhibitory capacity of the photoaging. The functional properties of tilapia collagen hydrolysate should be the object of future analysis in order to complement this research, before integrating them into the list of food or ingredients applicable to the food industry. método de evaluación de la actividad antioxidante. Se observó una mayor actividad antioxidante en el extracto de colágeno hidrolizado obtenido de la piel, que juega un papel importante en el envejecimiento cronológico de la piel y en la capacidad inhibidora del fotoenvejecimiento. Las propiedades funcionales del hidrolizado de colágeno de tilapia deberían ser objeto de análisis futuros para complementar esta investigación, antes de integrarlas en la lista de alimentos o ingredientes aplicables a la industria alimentaria.

There are several organisms from which collagen can be obtained, for example fish.
Fish has a significant economic importance because of its high availability, small risk of disease transmission, no religious barrier and toxicity, and the high yielding collagen in the extraction process (Senaratne, Park & Kim, 2006, Krishnamoorthi et al., 2017. In fact, tilapia (Oreochromis sp.) is a fish which has been widely studied for isolation and extraction of collagen.
Tilapia is a large genus of oreochromine cichlids and is widely distributed in tropical and subtropical regions, such as Israel, southeastern Asia, and America (Ramos, Vidotto-Magnoni & Carvalho, 2008). It is largely cultivated due to its fast reproduction and growth rate, excellent adequacy to the production systems, and high palatability (Bordignon, 2010, Fitzsimmons, 2000.
Due to its importance in the fishing process and to the costumers, this systematic review aimed to list the function properties attributed to the collagen obtained from tilapia in scientific studies.

Methods
This research followed the principles of a systematic review where the following criteria were considered: definition of the guiding question; the search for evidence in different databases; delimitation of the research period; and the inclusion and exclusion criteria (MENEZES, 2011).

Criteria for the selection of articles
The guiding question, the databases and the research period.

Inclusion and exclusion criteria
Original articles, published in English and Portuguese, using quantitative instruments were selected. When searching for articles, the following terms in English were used: "collagenoftilapiaandfood" and "collagenotilapiaandfoodandfunctional", and Boolean operator "and" to refine the data.
As inclusion criteria of the research, full articles were used, published in the last six years (from 2014 to 2019) and that reported some functionality to the Tilapia collagen. And as exclusion criteria, articles that did not mention in the title, abstract or text the subject addressed in this review and the duplicates were removed from the research.
These criteria were identified in the following research stages: Stage 1: Titles and abstracts were reviewed in order to determine eligibility.
Duplicated results and studies that did not meet the inclusion criteria were removed.
Stage 2: Selected studies were fully reviewed. Studies assessing the functional activity of tilapia collagen were selected.
The studies that met all the inclusion criteria discussing the proposed topic were selected and analyzed through a classification protocol created for this study. The following aspects were registered: authors, country, objective, and results.

Results and discussion
The search for articles that characterize the functional properties of Tilapia collagen is essential for making decisions related to innovation and helping to map the gaps for the scientific and technological development of this product. According to the criteria established in this study, in the last six years, a total of 387 publications were found, as shown in Figure   1.
The separate search of the term "tilapia collagen and food" retrieved 242 papers. 220 were retrieved using Science Direct and 22 using PubMed. Of these, seven papers met the inclusion criteria and were used in this review. The search of the term "tilapia collagen and food and functional" resulted in 145 studies. 141 were found using Science Direct and 4 using PubMed. Of these, three papers were selected for this review. No articles were found using EMBASE, MEDLINE, LILACS, Web of Science, and SCIELO databases. Therefore, ten studies in total were identified as eligible for inclusion in this systematic review (Figure 1).  Table 1.  Research, Society and Development, v. 9, n. 12, e2069129219, 2020 (CC BY 4. Research, Society and Development, v. 9, n. 12, e2069129219, 2020 (CC BY 4.0) | ISSN 2525-3409 | DOI: http://dx.doi.org/10.33448/rsd-v9i12.9219