Benefits of superfine grinding method on antioxidant and antifungal characteristic of Brazilian green propolis extract

Green propolis is found only in Brazil and due to its important biological characteristics, the food industry views it as a rich source of bioactive compounds. However, an extract must be produced for its application, which is difficult considering the rigid characteristics of raw propolis. Superfine grinding, a process capable of reducing particle size, enables the extraction of most bioactive compounds in propolis. This study evaluated the influence of grinding on size characteristics, antioxidant and antifungal properties of Brazilian green propolis for food preservation. The propolis powder was produced through six different types of grinding (different sieves and rpm), and its quality was evaluated by scanning electron microscopy-energy dispersive X-ray spectroscopy. After grinding, extracts and bioactive assays were produced and the total phenolic content, antioxidant and antifungal capacity were determined. The data showed that the grinding process affected all the results of bioactive assays used. Treatment B (sieve 0.08 mm, 12,000 rpm) presented statistically significant values for the bioactivity assays and thus antifungal activity against Rhizopus stolonifer (doses 0-5 %) was tested only for the control (standardized size without superfine grinding) and treatment B. Both treatments showed antifungal activity, but the control provided more effective mycelial growth inhibition (lower dose 1 %). Superfine grinding increased the antioxidant activity, although this behavior was not observed in the antifungal assay. Despite these results, green propolis extracts present important biological effects that indicate their use as food preservatives to extend shelf life of food products.