Fermented foods have been used for several years all over the world, due to their unique nutritional characteristics and because fermentation promotes conservation and food security. Moreover, fermented foods and beverages have a strong impact on human gut microbiota. Papaya is the fruit of the Carica papaya plant, traditionally used as a medicinal fruit, but there are also references to the use of the fermented form of this fruit. The main purpose of this review is to provide an improved understanding of fermented papaya nutritional and health applications. A literature search was conducted in the PubMed and Google Scholar databases. Both in vitro and in vivo studies were included. According to the retrieved studies, fermented papaya has proven to be an excellent antioxidant and an excellent nutraceutical adjuvant in combined therapies against several diseases, such as Alzheimer’s disease, allergic reactions, anticancer activity, and anemias. Therefore, it is concluded that fermented papaya has many benefits for human health and can be used as prevention or aid in the treatment of various diseases.

Fermented papaya is recognized as a nutraceutical with a diverse and rich composition. Fermentation of fruit with desirable microorganisms could be a strategy to improve the nutritional quality and profile of the fruit. Despite the popularity of fermented papaya, there is still a lack of knowledge on the effects of various fermentation parameters. The goal of this study was to screen the antioxidant and other properties of the products obtained through a variety of fermentation experiments, as well as the impact of adding Gluconobacter oxydans on their physicochemical properties. The strategies used to produce the fermented papaya extracts were spontaneous fermentation and bioinoculation with G. oxydans. Different fermentation tests were performed to measure pH, total soluble solids, reducing sugars, sodium pyruvate content, total phenolic content (TPC), and ferric reducing antioxidant power (FRAP). There was a decrease in TPC during spontaneous fermentations (five assays). However, it can be observed that in the fermentation assays with G. oxydans, there was an increase in TPC and antioxidant properties. The highest content of TPC was observed on the eighth day of P7 (260.18 ± 0.02 µg gallic acid equivalents mL⁻¹) which was fermented with the bacteria and supplemented with glucose. Therefore, phenolic compounds in fermented papaya were found to increase antioxidant capacity as a result of bioinoculation with G. oxydans.