INFLUENCE OF PACKAGING YEAST POPULATION

Influence of Packaging Yeast Population Processed Orange Slices

Influence of Packaging Yeast Population Processed Orange Slices

Introduction

The yeast population of minimally processed orange slices, packaged both in normal and modified atmosphere and with films of different permeabilities, was studied in order to set up the most suitable packaging conditions. Modified atmosphere resulted in a fermentative association of yeast strains, with the dominance of Saccharomyces cerevisiae strains. In samples packaged in normal atmosphere isolated strains have been mainly identified as Rhodotorula spp.

Discussion

The development of Minimally Processed Fruit (MPF) can allow diversification and promotion of the processed fruit industry, which is very important for the economy of the Mediterranean regions and, particularly, for Sicily, where the production of oranges is very widespread. Oranges on the basis of their morphological and physiological characteristics show good potentiality to be minimally transformed (Pretel et al., 1998). Studies on minimally transformed blond oranges have been done regarding enzymatic peeling and modified atmosphere packaging (Pretel et al., 1998), sensory changes during storage at low temperatures (Rocha et al., 1995; Caggia et al., 2004), shelf-life extension of peeled oranges by citric acid treatment, microbiological stability and development of bitter substances (Pao et al., 1997). Yeasts are common contaminants of fruit and represent a major problem for fruit processing industries, due to the ability to grow at low pH and high sugar content (Deak and Beuchat, 1993; Davenport, 1996). According to several studies the most common yeast contaminants isolated from fresh and processed fruit and from fruit juices and soft drinks are Candida spp., Debaryomyces hansenii, Hansenula spp., Rhodotorula spp., Pichia spp., Dekkera spp., Lodderomyces elongisporus, Hanseniaspora spp., Issatchenkia orientalis, Kloeckera spp., Kluyveromyces marxianus, Pichia anomala, Saccharomyces spp., Torulaspora delbrueckii and Zygosaccharomyces spp. (Gardini and Guerzoni, 1986; Thomas, 1993; Tudor and Board, 1993). In particular, Saccharomyces cerevisiae is considered to be a predominant spoilage species in concentrates, juices, fruit beverages, and in general in processed fruits (Maimer and Busse, 1992). The aim of this work was to investigate the yeast population present in minimally processed orange slices packaged with three films of different permeability under atmospheric condition and modified atmosphere packaging (MAP). Orange fruits from harvests 2003 and 2004 belonging to cultivar Tarocco, cultivated in the experimental field of the “Istituto Sperimentale per l'Agrumicoltura” (Acireale, Catania, Italy), were used. Selected oranges were washed at about 15 °C with a solution containing 200 ppm of Cl2 obtained by dilution (2 ml l-1) of a sodium hypochlorite solution with 10% of available chlorine (Aldrich, Milwaukee, WI, USA); the fruits were then rinsed with distilled water, dried and peeled manually. Then they were sliced along the fruit equatorial diameter by an electric slicer (1 cm thick) and packaged in white CPET (Crystallized Polyethylene Terepthalate) trays. The experimental design considered six different trials: fruits packaged under ordinary atmospheric conditions with three different permeability films (Table 1) and fruits packaged with the lowest permeability film (Film A) under three different modified atmospheres a, ß and ? as shown in Table ...