Different postharvest storage conditions of Arbutus unedo L. fruits, and their physicochemical and microbiological characterisation

Abstract

Arbutus unedo L. is a species with great economic impact in rural areas, and its fruits have several food applications and beneficial properties on human health. However, the fruits are highly perishable, and little is known about their characteristics. The present work thus aimed to evaluate the physicochemical and microbiological parameters of Arbutus unedo L. during two consecutive years from four different samples. Microbiological analysis was conducted at different times of preservation (days 0, 4, 11, and 21) and temperatures (room temperature, refrigeration, and freezing). Six fungal strains as representatives of the most prevalent mycobiota in fruits were used for molecular identification. The fruits had aw values of 0.916 ± 0.01 to 0.930 ± 0.01, pH values of 3.81 ± 0.01 to 3.82 ± 0.01, and ºBrix values of 25.02 ± 0.49 to 28.52 ± 1.02. Microbiological analysis revealed that the predominant microbiota in fresh fruits were psychrotrophs (4.07 ± 0.25 log CFU/g), yeasts (3.39 ± 0.18 log CFU/g), mesophiles (3.26 ± 1.20 log CFU/g), and moulds (2.70 ± 0.55 log CFU/g). After a preservation period of 11 days, the microbial loads increased from 66 to 116% at 25 ± 1°C; while at 6.5 ± 1°C, the increase varied from 3 to 53%; except for moulds, for which a decrease was observed. The application of freezing temperature (21 days) showed a small increase for psychrotrophs and yeasts of 1.5 and 2.9%, respectively. The most prevalent moulds identified belonged to Rhizopus stolonifer var. stolonifer, Aspergillus carbonarius, and Penicillium brevicompactum, while yeasts belonged to Aureobasidium sp. and Saccothecium rubi.