Microbial flora during storage of packaged fresh orange juice

ANDRÉS S.C.; GIANNUZZI L.; ZARITZKY N.E.

SCANNING

JOHN WILEY & SONS INC

Lugar: Chicago, Illinois, USA; Año: 1999 vol. 21 p. 147 - 148

0161-0457

The microflora responsible of deterioration of fruits and vegetables ready to eat, include a great number of bacterial and fungic species. The low pH of the fruits and the type of organic acids in the tissues generally inhibit the growth of  microorganisms other than  lactic acid bacteria. The objective of the present work was to analyze, in natural refrigerated orange juice, the effect of the previous washing process of the peel of the fruits, the subsequent packaging of the juice in plastic films of different gaseous permeability (polyethylene and EVA-SARAN-EVA) and the refrigerated storage of the packaged juice, on the microbial flora applying isolation techniques and microscopic observation (Light Microscopy and Environmental Scanning Electron Microscopy). At different storage times, total and psychrotrophic microorganisms, moulds and yeast and tolerant acid microbial counts were done. The final quality of the product was tested using the most probable number (MPN) method for coliform counts. For the samples packaged in ESE the sulfite-reducing Clostridium counts were performed. Isolation of microorganisms was performed and Gram and Blue methylene blue coloration was applied. Microscopic observation was done using Light Microscopy and Envirommental Scanning Electron Microscopy. Isolated yeasts were identified using the method of Kreger-van Rij, and the filamentous molds were identified according to their morphological characteristics. Predominant microorganisms growing in orange juice were molds and yeasts. Identified yeasts were Rhodotorula rubra and Candida quercitrusa. The isolated mold colonies were Cladosporium, Penicillium, Epicoccum, Stemphilium and Dresclera. The evaluation of the sanitary conditions of the different types of juice indicates the safety conditions of the product. Washing the orange peel with a solution of sodium hypochlorite and using simultaneously films with low gaseous permeability allowed to extend the storage life of the juice (time to reach microbial counts of 106 CFU/ml) from 6 to 10 days.