Influência do congelamento sobre a estabilidade microbiológica e físico- química de polpas de frutas: Mapfilua (Vangueria infausta) e Maracujá amarelo (Passiflora edulis f. flavicarpa degenerer)

Abstract

The freezing of fruit pulps represents a technological alternative to reduce post-harvest losses, extend shelf life, and ensure greater access to essential nutrients outside the harvest season. Nevertheless, the process may cause changes in product stability, making it important to understand these variations to ensure product quality and safety. The present study evaluated the effect of freezing at −18 °C on the microbiological and physicochemical stability of mapfilua (Vangueria infausta) and yellow passion fruit (Passiflora edulis f. flavicarpa Degenerer) pulps over 90 days, in order to determine the influence of freezing on these parameters. A total of 1200 g of fresh commercial pulp from each fruit was collected and packaged in 150 g containers. Part of the fresh pulps was analyzed as a reference, while the remainder was frozen and stored at −18 °C, being analyzed every 15 days up to 90 days. Microbiological counts (mesophilic aerobic bacteria, molds and yeasts) and physicochemical determinations (pH, titratable acidity, total soluble solids (°Brix), °Brix/Acidity ratio, and vitamin C content) were performed with 2 replicates for microbiology and 3 for physicochemical analysis, after slow thawing at 2 °C for 10 to 15 hours. The results were subjected to ANOVA, Tukey’s test, and regression analysis. Microbiological results indicated a trend of reduced counts over the 90-day period: mesophilic aerobic bacteria ranged approximately from 3.02–2.42 log CFU/g in mapfilua and 2.86–2.01 log CFU/g in passion fruit; molds and yeasts showed similar behavior, ranging from 2.75–2.09 log CFU/g in mapfilua and 2.97–2.43 log CFU/g in passion fruit. Regarding physicochemical parameters, total soluble solids remained stable (11 °Brix in mapfilua and 20 °Brix in passion fruit). The pH ranged from 3.12–3.19 in mapfilua and 2.70–2.78 in passion fruit, while titratable acidity varied between 0.93–1.23 g citric acid/100 g in mapfilua and 2.85–3.32 g citric acid/100 g in passion fruit, reflecting fluctuations in the °Brix/Acidity ratio (11.84–8.95 in mapfilua and 7.02–6.02 in passion fruit). Vitamin C content showed a continuous decrease, dropping from 35.23 to 29.87 mg/100 g in mapfilua and from 29.35 to 25.97 mg/100 g in passion fruit over the 90 days. Freezing at −18 °C for 90 days preserves the microbiological stability of mapfilua and passion fruit pulps and results in physicochemical changes without significantly compromising product characteristics. The variables show distinct trends over the 90-day period, depending on each parameter’s sensitivity to the freezing process and storage time.