Effect of chemical preservatives and packaging film permeability on microbial growth in refrigerated orange juice

ANDRÉS, SILVINA CECILIA; GIANNUZZI, LEDA; ZARITZKY, NOEMÍ E

Veldhoven, Holanda

Conferencia; Food Microbiology and Food Safety into the Next Millennium, Seventeenth International Conference of the International Commitee on Food Microbiology and Hygiene (ICFMH).; 1999

International Commitee on Food Microbiology and Hygiene (ICFMH), Veldhoven, Holanda.

Soft drinks and fruit preserves sometimes require the addition of chemical preservatives to improve their storage stability. These additives should be used carefully and only when there is a clear need to increase shelf life, prevent spoilage, or minimise the food-poisoning risk. The microflora responsible of deterioration of ready to eat fruits and vegetables 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. Yeasts predominate in spoilage of acid fruit products because of their high acid tolerance and the ability of many of them to grow anaerobically. The objectives of the present work were to analyse the composition of the microbial flora in natural refrigerated orange juice, to model microbial growth, and to determine the effect of  different preservatives (ascorbic acid, citric acid, potassium sorbate or benzoate) on shelf life of the product. Polyethylene bags and EVA-SARAN-EVA (ESE) film was used. pH and titratable acidity, concentration of organic acids in the juice, total, rducing and non reducing sugars, soluble, insoluble and total solids were evaluated. Isolation and identified of microorganisms was performed. Microscopic observation was done using Light Microscopy and ESEM. At different times, total, psychrotrophic, mould and yeast and tolerant acid microbial counts were done. The final quality of the product was tested using the most probable number method for coliform counts. For the samples packaged in ESE the sulfite-reducing Clostridium counts were performed. Gompertz equation was applied to every culture in which microbial growth was detected. When preservatives produced bactericidal effect, a linear model was applied. Inhibition Indices were calculated for each assayed condition. Predominant microorganisms were moulds and yeasts. Washing the orange peel with sodium hypochlorite and using simultaneously films with low gaseous permeability, allowed to extend the storage life of the juice, with safety conditions of the product.