Different technologies are currently investigated with the aim of decontaminating fresh-cut produce avoiding physical and chemical changes associated to minimal processing. Pulsed light (PL) is a non-thermal technology and has been demonstrated to be cost effective and feasible for the microbial inactivation of both solid and liquid food products. On the other hand, the use of edible coatings is another alternative investigated to extend the shelf-life of fresh-cut products, they serve as carriers of food additives such as antibrowning and antimicrobial agents, colorants, flavors, nutrients, spices and nutraceuticals.
Spanish scientists evaluated the combined application of PL treatments (12 J/cm2) with gellan-gum (0.5% w/v) edible coating incorporating apple fiber on the quality of fresh-cut 'Golden Delicious' apple stored at 4°C for 14 days.The full study is available online since July 7th 2015 at:
http://www.sciencedirect.com/science/article/pii/S0023643815300190
For the study, apples were washed, rinsed and dried prior to the cutting operations. Subsequently, each fruit was peeled, cored and diced into 1 cm-thick cubes. Apple dices were first dipped for 2 min into a gellan gum film-forming solution, either with or without added apple fiber. The excess of coating solution was allowed to drip off for 1 min before submerging the fruit pieces for 2 min into the cross linking dip containing ascorbic acid and calcium chloride. Control samples were dipped only into the cross linking solution. Ten apple cubes (ca. 60 g) were placed into polypropylene trays, which were wrap-sealed with a polypropylene film. The trays were heat-sealed and stored at 4 ± 1°C during less than 30 min prior to PL-processing.
Results showed that the combined application of coating and PL treatment slowed the microbiological deterioration of fresh-cut apples and maintained the sensory attribute scores above the rejection limits after prolonged storage. Incorporation of fiber in the coating formulation did not curb the sensory acceptability of apple cubes. Results show that the use of a gellan-gum based coating incorporating apple fiber followed by the application of a PL treatment significantly reduced softening and browning of apple pieces through storage.
Scientists explain that PL is an emerging technology which has considerable potential as an alternative to thermal and chemical methods for rapid and effective inactivation of microorganisms on food surfaces, while the application of gellan coatings with PL treatments may be useful to extend the shelf-life of fresh-cut apple.
This study provides new information on the possible benefits and drawbacks of combined application of PL with gellan-gum edible coating. In this regard, scientists point out that the use of edible coatings could act as a limiting factor for the surface decontamination by PL treatments, because the antimicrobial effect of pulsed light on coated fruit cubes was reduced. However, the combination of both treatments has been shown to favor the preservation of the antioxidant value of fresh-cut apples. Moreover, the incorporation of fiber to the coatings was not found to have any negative implication on the quality of fresh-cut apples, thus becoming an interesting alternative for increasing the prebiotic benefits of fresh-cut commodities.
Source: María R Moreira, Barbara Tomadoni, Olga Martín-Belloso, Robert Soliva-Fortuny, 'Preservation of fresh-cut apple quality attributes by pulsed light in combination with gellan gum-based prebiotic edible coatings', December 2015, LWT - Food Science and Technology, Vol. 64 (2), pages 1130-1137
Contacts:
Robert Soliva-Fortuny
Department of Food Technology, University of Lleida e Agrotecnio Center
Lleida, Spain
Email: rsoliva@tecal.udl.cat