Avaliação da eficácia de revestimentos biopoliméricos de mucilagens de cactáceas incorporados com cultura mista de bactérias láticas para o controle de colletotrichum sp. em abacate

Abstract

Avocado ( Persea americana Mill.) has gained prominence in the global agricultural sector due to its high nutritional value and various health benefits, such as reducing the risk of cardiovascular disease, aiding in weight control, improving digestive and intestinal functions, and potential positive effects on cognition and skin health. However, as a climacteric fruit, it is susceptible to phytopathogens, particularly Colletotrichum sp., the causal agent of anthracnose. Although the disease is commonly controlled with chemical fungicides, the application of these compounds is associated with environmental impacts and the risk of microbial resistance. Alternatively, edible coatings based on natural sources, incorporated with lactic acid bacteria (LAB), emerge as a promising biopreservation strategy. Among the matrices used in coatings, cactus mucilages stand out for being biodegradable materials with high water retention capacity, antioxidant activity, and rheological properties that favor stability and functionality in food systems. Thus, this study aimed to evaluate the application potential of coatings formulated with mucilage from the palm ( Nopalea cochenillifera ) and the cactus ( Pilosocereus pachycladus ) with the addition of a mixed LAB culture for the control of Colletotrichum sp. in avocados. For this purpose, mucilages from different species of cacti were obtained by ethanolic extraction and evaluated for physical and physicochemical parameters. Mucilages and LAB strains (namely: Levilactobacillus brevis 59; Lactiplantibacillus pentosus 129; Lacticaseibacillus paracasei 108; Lactiplantibacillus plantarum 49; Limosilactobacillus fermentum 263; 9–10 log CFU/g), isolated and combined in mixed culture, were used in in vitro antifungal tests against isolates of Colletotrichum siamense . Antifungal activity was evaluated using the well diffusion method and minimum inhibitory concentration (MIC) determination. Formulated coatings were applied to avocados artificially contaminated with Colletotrichum sp., and the percentage reduction in anthracnose lesion diameter (RLDA%) was evaluated during 7 days of storage at 25 ± 1°C. The mucilages evaluated presented physicochemical properties with technological relevance, including acidic pH, low water activity, adequate solubility, and moderate antioxidant activity. They were also able to inhibit the mycelial growth of C. siamense , with results directly proportional to the concentration applied. The LAB exhibited antifungal potential, especially the strains Lactiplantibacillus pentosus 129, Lactiplantibacillus plantarum 49, and Limosilactobacillus fermentum 263, used in the formulation of the mixed culture. The incorporation of the mixed LAB culture into the mucilage coatings resulted in increased antifungal capacity, with RDLA% ranging from 16.9% to 100% in the treated fruits. In particular, the combination of palm mucilage with LAB showed greater stability and functionality throughout storage. The results demonstrated that cactus mucilages, especially when incorporated with BAL mixed culture, showed high potential for application as bioprotective coatings, favoring post-harvest conservation and increasing the shelf life of avocados.