EFFECT OF A CELLULOSE NANOFIBRIL-BASED COATING ON THE MICROBIOLOGICAL QUALITY AND PHENOLIC COMPOUNDS OF STRAWBERRIES

Strawberry is a highly perishable fruit with a short postharvest shelf life, and edible coatings have emerged as a promising strategy for maintaining fruit quality during storage. This study evaluated the effects of a cassava starch-based edible coating reinforced with 20% cellulose nanofibrils (CNFs) obtained from tucumã peel on the microbiological quality and phenolic profile of strawberries during refrigerated storage. Strawberries were coated by immersion and stored at 2 ± 1 °C and 90 ± 5% relative humidity. Uncoated fruits (control) and fruits coated with cassava starch containing 20% CNFs were evaluated at the beginning (day 0) and after 16 days of storage. Microbiological quality was assessed based on mold and yeast counts, expressed as log CFU/g. Total phenolic content (TPC) was determined using the Fast Blue method, while gallic, caffeic, and o-coumaric acids and catechin were quantified by high-performance liquid chromatography. Data were subjected to analysis of variance considering the effects of treatment, storage time, and their interaction, with significance established at p < 0.05. A significant treatment × storage time interaction was observed for microbial counts. At day 0, no significant differences were observed between treatments; however, after 16 days, uncoated strawberries showed a higher microbial count (4.85 log CFU/g) than coated fruits (4.22 log CFU/g), indicating that the CNF-containing coating limited microbial growth during refrigerated storage. TPC was affected only by treatment, with higher mean values in the control than in coated fruits (500.50 and 429.47 mg/100 g fresh weight, respectively). Caffeic acid showed a similar pattern, with higher concentrations in the control (4.98 mg/100 g) than in the 20% CNF treatment (3.23 mg/100 g), regardless of storage time. Gallic acid was affected only by storage time, increasing from 0.19 to 0.26 mg/100 g, irrespective of treatment. Catechin concentration averaged 4.78 mg/100 g and was not significantly affected by treatment or storage time. A significant treatment × storage time interaction was also observed for o-coumaric acid. Although concentrations were similar between treatments at day 0, after 16 days the control exhibited a higher concentration (0.37 mg/100 g) than the coated treatment (0.24 mg/100 g). The higher concentrations of some phenolic compounds in uncoated fruits may be associated with the activation of defense responses in response to greater fungal development. Overall, the cassava starch-based coating containing 20% CNFs obtained from tucumã peel reduced microbial growth and modified specific components of the phenolic profile during refrigerated storage. These findings highlight the potential of this coating as a sustainable postharvest strategy for extending the storage quality of strawberries.

Acknowledgments: We thank the Coordination for the Improvement of Higher Education Personnel (CAPES) and the National Council for Scientific and Technological Development (CNPq) for their support.