Elaboração e aplicação de emulsões com óleos essenciais em morangos (Fragaria × ananassa Duch)

Abstract

Anthracnose and alternariosis are among the major fungal diseases affecting economically important fruits, causing significant losses during production, storage, transportation, and commercialization. Anthracnose is mainly caused by fungi of the genus Colletotrichum, whereas alternariosis is associated with fungi of the genus Alternaria. Both diseases compromise the visual, nutritional, and commercial quality of fruits. Given the increasing concerns regarding the excessive use of synthetic fungicides, the search for natural, effective, and sustainable alternatives for the control of these microorganisms has become necessary. In this context, essential oils stand out due to their bioactive compounds with recognized antimicrobial activity, which may act as natural agents for the control of phytopathogenic fungi. The present study aimed to develop an essential-oil-based emulsion and evaluate its antifungal activity against Colletotrichum gloeosporioides, the main causal agent of anthracnose, and Alternaria alternata, an important fungus associated with the postharvest deterioration of fruits. In vitro antifungal activities of essential oils from clove (Syzygium aromaticum), cinnamon (Cinnamomum cassia), mint (Mentha arvensis), and Sicilian lemon (Citrus limon) were evaluated, as well as an emulsion formulated by combining these essential oils. Physicochemical, microbiological, and visual analyses were also performed, including mass loss, total soluble solids, titratable acidity, pH, color parameters, fungal development, and visual preservation of strawberries.The fruits were subjected to six treatments: untreated control (T1), commercial sanitizer (T2), 0.5% essential-oil emulsion applied by spraying (T3), 1.0% essential-oil emulsion applied by spraying (T4), 0.5% essential-oil emulsion applied by immersion (T5), and 1.0% essential-oil emulsion applied by immersion (T6). Following treatment, the strawberries were stored under refrigeration at temperatures ranging from 3 to 7 °C for up to 13 days.The in vitro results demonstrated that all essential oils exhibited antifungal activity against the evaluated fungi, with cinnamon and clove showing the greatest inhibition zones. The combined essential oils also exhibited antifungal activity, with the largest inhibition zones observed at the 50 µL volume. Microbiological evaluation was performed using the direct fruit-rolling method on Petri plates containing potato dextrose agar (PDA), followed by incubation at 28 °C for seven days. The results demonstrated that treatments containing essential oils showed significant antifungal activity compared with the control, reducing fungal growth. The highest inhibition rates were observed in the spraying treatments, particularly T3 (96.7%) and T4 (95.7%), which were higher than those observed for the commercial sanitizer T2 (85.7%). The immersion treatments also reduced microbial growth, although with lower efficiency.Regarding the physicochemical analyses, the spraying treatments contributed to lower mass loss, greater stability of color parameters, and better preservation of fruit visual quality throughout refrigerated storage. Treatment T4 stood out for reducing mass loss, whereas T3 showed better maintenance of the chromatic characteristics of the strawberries. Visual analyses confirmed a lower incidence of wrinkling, darkening, and fungal growth in fruits treated with emulsions applied by spraying. It is concluded that essential-oil-based emulsions have high potential as a natural and sustainable alternative for the postharvest conservation of strawberries, particularly when applied by spraying. The results indicate that the use of these emulsions may contribute to reducing changes associated with postharvest deterioration, representing a promising alternative to conventional chemical fungicides for the control of diseases associated with anthracnose and alternariosis.