Fungi occurrence can cause economic losses due to the decrease in productivity and quality of grapes. Among the most important fungi for viticulture are Botrytis cinerea and Aspergillus sp., which cause grape rot. Besides the spoilage, an important concern is that some Aspergillus species, such as Aspergillus carbonarius and Aspergillus niger, are capable of producing ochratoxins in grapes (Welke, 2019). A. niger is most commonly isolated in grapes than other black aspergilli, while A. carbonarius produces high levels of this toxin (Nievierowski et al., 2021; Taniwaki et al., 2018; Welke, 2019), both deserve priority investigations among the Aspergillus species used in studies on the control of fungi in grapes. Among ochratoxins, ochratoxin A (OTA) is the most toxic due to its immunosuppressive, genotoxic, neurotoxic, hepatotoxic and nephrotoxic potential (Liu et al., 2022). This mycotoxin is classified as possibly carcinogenic to humans (group 2B) by the International Agency for Research on Cancer (IARC, 1993). Due to its toxicity, the Brazilian (Brasil, 2022) and European Union (European Commission, 2006) agencies established 2 μg/kg as the maximum limit of OTA in wines and grape juices.

Synthetic fungicides are widely used to control the incidence of fungus on grapes. However, these products cause a deleterious environmental impact and toxic effects to occupationally exposed individuals, the population living around agricultural areas and consumers of food containing harmful residues of these agrochemicals. In addition, the emergence of fungi resistant to routinely applied fungicides stimulates the development of new fungal control strategies (El-Baky and Amara, 2021).

The use of natural compounds, such as essential oils or their individual constituents, has been shown to be an alternative to synthetic fungicides (Qi et al., 2023). Carvacrol is the main component of oregano (Origanum spp.) essential oil, which has antiviral, antioxidant, anti-inflammatory, bactericidal and fungicidal action (Souza et al., 2022). This monoterpenoid is approved as a food additive (flavoring) by the US Food and Drug Administration (FDA, 2023) and the European Commission (European Commission, 2012), in addition to being authorized as an additive in animal feed (European Commission, 2023).

Despite the many benefits of carvacrol, some characteristics such as high hydrophobicity and volatility reduce its efficiency. Furthermore, the characteristic odor and taste restrict its application in food (Cacciatore et al., 2020). The encapsulation of carvacrol can overcome these disadvantages by reducing its volatility and flavor perception, in addition to causing its release gradually, ensuring the antimicrobial effect for a longer time.

Synthetic and natural materials have been used as encapsulating agents (Zabot et al., 2022). Synthetic polymethylacrylate polymers, such as Eudragit®, have been widely used in the pharmaceutical industry due to its ability to slowly and gradually release the active ingredient of a drug (Nikam et al., 2023). Chia seeds (Salvia hispanica L.) when in contact with water exude the soluble fiber fraction in the form of mucilage. Chia mucilage is a promising natural material for the food industry due to its emulsifying and stability properties that make it a suitable biopolymer for encapsulation purposes (Antigo et al., 2020). Eudragit® and chia mucilage were used as wall material to produce carvacrol nanocapsules with antibacterial purposes in previous studies (Cacciatore et al., 2020, Cacciatore et al., 2022). Cacciatore et al. (2020) reported that nanoencapsulated carvacrol in Eudragit® reduced the population of Escherichia coli, Listeria monocytogenes, Salmonella spp. and Staphylococcus aureus adhered to stainless steel surface more effectively than carvacrol nanoliposomes prepared with soy phosphatidylcholine. In another approach, encapsulated carvacrol in chia mucilage nanocapsules showed greater activity against Listeria monocytogenes and Salmonella spp. than carvacrol-loaded in flaxseed mucilage nanocapsules and carvacrol solution (unencapsulated carvacrol) (Cacciatore et al., 2022).

In summary, Eudragit® and chia mucilage were chosen as wall material for the carvacrol nanocapsules in this study due to the following reasons: (i) previous promising antibacterial results obtained when these two substances were used to obtain carvacrol nanocapsules (Cacciatore et al., 2020, Cacciatore et al., 2022); (ii) well-established use of Eudragit® as a controlled drug release agent and its safety of oral ingestion (Nikam et al., 2023); and (iii) possibility of comparing the performance of a synthetic wall material and a natural one for the production of nanocapsules with antifungal activity.

Although studies have shown that carvacrol is able to inhibit the in vitro growth of A. flavus (Duan et al., 2024; López-Malo et al., 2002), A. carbonarius (Wang et al., 2018), A. niger (Janatova et al., 2015) and B. cinerea (Zhang et al., 2019; Martínez-Romero et al., 2007), no data on the antifungal potential of this monoterpenoid (in aqueous solution or nanocapsules) against these fungi in grapes has been previously reported. Furthermore, the antifungal activity of carvacrol loaded into nanocapsules of Eudragit® and chia mucilage is unknown.

The objective of this study was to evaluate the potential of carvacrol unencapsulated and loaded in nanocapsules of Eudragit® and chia mucilage to control the growth of fungi important for grape quality (A. flavus, A. carbonarius, A. niger and B. cinerea), as well as to inhibit the synthesis of ochratoxins by A. carbonarius and A. niger. The experiments were conducted in vitro and on grapes with and without damage to their surface. The characterization of the nanocapsules was also carried out to verify their stability and application potential as a novel strategy to mitigate the losses experienced by the grape and derivatives sector.