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Edible films including active ingredients can be used as an alternative to preserve food products. Essential oils (EOs) exhibit antimicrobial activity against pathogenic microorganisms but their low water solubility limits the application in foods. To improve water dispersion and protect EOs from degradation, nano-sized emulsions emerge as a viable alternative. Nanoemulsions containing EOs and polysaccharides could be used to form edible films with functional properties. This study was focused on the evaluation of physical, mechanical and antimicrobial properties of alginate-based edible films formed from nanoemulsions of EOs. Nanoemulsions containing thyme (TH-EO), lemongrass (LG-EO) or sage (SG-EO) oil as dispersed phase and sodium alginate solution as continuous phase were prepared. The average droplet size of nanoemulsions was reduced after the microfluidization treatment exhibiting multimodal size distributions. The zeta-potentials of nanoemulsions were between 41 mV and 70 mV depending on the type of EO used. The lowest whiteness index was found in SG-EO nanoemulsions, whereas those containing TH-EO showed the highest value. Films formed from SG-EO nanoemulsions exhibited higher transparency, water vapor resistance and flexibility than films formed from TH-EO or LG-EO. Edible films containing TH-EO were those with the strongest antimicrobial effect against inoculated Escherichia coli, achieving up to 4.71 Log reductions after 12 h. Results obtained in the present work evidence the suitability of using nanoemulsions with active ingredients for the formation of edible films, with different physical and functional properties. (C) 2015 Elsevier Ltd. All rights reserved This research was supported by the Ministerio de Ciencia e Innovación (Spain) throughout projects ALG2009-11475 and ALG2012-35635. Author Acevedo-Fani also thanks to the University of Lleida for the pre-doctoral grant. Author Martín-Belloso acknowledges to the Institució Catalana de Recerca I Estudis Avançats (ICREA) for the Academia 2008 Award.

The use of alginate- (2% w/v) or gellan-based (0.5% w/v) coating formulations on fresh-cut papaya pieces was investigated in order to determine their ability to improve water vapor resistance (WVR), to affect gas exchange and to carry agents that help to maintain the overall quality of the minimally processed fruit. Formulations containing 2% (w/v) glycerol+1% ascorbic acid or 1% glycerol+1% ascorbic acid exhibited slightly improved water barrier properties for both types of coatings, as compared to the uncoated samples. The incorporation of 0.025% (w/w) sunflower oil into the alginate or the gellan-based formulations resulted in a 16% and 66% increase in the WVR of the coated samples, respectively. In general, coatings improved firmness of the fresh-cut product during the period studied. Furthermore, the addition of ascorbic acid as antioxidant in the coatings aided to preserve the natural ascorbic acid content of the fresh-cut papaya, helping to maintain its nutritional quality throughout storage. The gas barrier properties of the formulated coatings were not modified to allow substantial changes on respiratory rate and ethylene production of the coated papayas.

Alginate (2% w/v) and gellan (0.5% w/v)-based edible coatings were formulated to study the effect of glycerol (G) and antibrowning agents (N-acetylcysteine and glutathione) on water vapor resistance (WVR). The ability of the coatings to carry antibrowning agents was investigated following color changes of coated fresh-cut Fuji apples. Selected formulations obtained by a response surface analysis were 1.5% G, 1% N-acetylcysteine and 0.63% G, 1% N-acetylcysteine for alginate and gellan, respectively. The addition of sunflower oil with essential fatty acids (ω3 and ω6) at 0.025%, 0.05%, and 0.125% w/v concentrations was also investigated in an attempt to improve the barrier properties of the alginate and gellan coatings for fresh-cut apples. The WVR increased significantly from 15.70 and 14.60 s/cm to 19.2 and 27.6 s/cm for alginate and gellan coatings with sunflower oil, respectively, in comparison with oil free coatings. The addition of sunflower oil in gellan was more effective than in alginate to increase the WVR of coated apples. Alginate and gellan-based coatings proved to be good carriers for antibrowning agents.