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Lyophilization, also called freeze-drying, is an important dehydration technique mainly used for pharmaceuticals. Food industry also uses lyophilization when it is important to retain most of the nutritional quality, taste, shape and size of dried products and to extend their shelf life. Vacuum-Induced during freezing cycle (VI) has been used in order to control ice nucleation and, consequently, to reduce the time of primary drying cycle of pharmaceuticals preserving quality properties of the final product. This procedure has not been applied in freeze drying of foods. The present work aims to investigate the effect of VI on the lyophilization drying time, final moisture content, density and reconstitutional properties of mango (Mangifera indica L.) slices (MS) and mango pulp-maltodextrin dispersions (MPM) (30% concentration of total solids). Control samples were run at each freezing rate without using induced vacuum. The lyophilization endpoint was the same for all treatments (constant difference between capacitance and Pirani vacuum gauges). From the experimental results it can be concluded that at the high freezing rate (0.4°C/min) reduced the overall process time up to 30% comparing process time required for the control and VI of the lower freeze rate (0.1°C/min) without affecting the quality characteristics of the dried product, which yields a reduction in costs and energy consumption for MS and MPM freeze drying. Controls and samples treated with VI at freezing rate of 0.4°C/min in MS showed similar results in moisture and density parameters. Furthermore, results from MPM dispersion showed favorable values when VI was applied because dried product with low moisture content and low density was obtained at shorter process time compared with the control. There were not found significant differences between reconstitutional properties (rehydration for MS and solubility for MPM) of freeze dried mango resulting from controls, and VI treatments., {"references":["S. Krzykowski, A. Dziki, D. Polak, R. Rudy, \"Influence of heating\nplates temperature on freeze drying energy requirements and quality of\ndried vegetables,\" TEKA. Comm. Mot. Energ. Agric., vol. 12, no. 2, pp.\n129 – 132, 2012.","L. G. Marques, M. M. Prado, and J. T. Freire, \"Rehydration\ncharacteristics of freeze-dried tropical fruits,\" LWT - Food Sci. Technol.,\nvol. 42, no. 7, pp. 1232–1237, 2009.","R. Geidobler and G. Winter, \"Controlled ice nucleation in the field of\nfreeze - drying: Fundamentals and technology review,\" Eur. J. Pharm.\nBiopharamceutics, vol. 85, no. 2, pp. 214–222, 2013.","C. E. Orrego, \"Congelación,\" in Congelación y liofilización de\nalimentos, Universidad Nacional de Colombia, 2008, pp. 1–21.","M. Kramer, B. Sennhenn, and G. Lee, \"Freeze-drying using vacuuminduced\nsurface freezing,\" J. Pharm. Sci., vol. 91, no. 2, pp. 433–443,\n2002.","J. Liu, T. Viverette, M. Virgin, M. Anderson, and D. Paresh, \"A study of\nthe impact of freezing on the lyophilization of a concentrated\nformulation with a high fill depth.,\" Pharm. Dev. Technol., vol. 10, no.\n2, pp. 261–272, 2005.","I. Oddone, R. Pisano, R. Bullich, and P. Stewart, \"Vacuum-Induced\nNucleation as a Method for Freeze-Drying Cycle Optimization,\" 2014.","K. J. Mothibe, C.-Y. Wang, A. S. Mujumdar, and M. Zhang,\n\"Microwave-Assisted Pulse-Spouted Vacuum Drying of Apple Cubes,\"\nDry. Technol., vol. 32, no. 15, pp. 1762–1768, 2014.","A. M. Ceballos, G. I. Giraldo, and C. E. Orrego, \"Effect of freezing rate\non quality parameters of freeze dried soursop fruit pulp,\" J. Food Eng.,\nvol. 111, no. 2, pp. 360–365, 2012."]}

High moisture content in fruits generates post-harvest problems such as mechanical, biochemical, microbial and physical losses. Dehydration, which is based on the reduction of water activity of the fruit, is a common option for overcoming such losses. However, regular hot air drying could affect negatively the quality properties of the fruit due to the long residence time at high temperature. Power ultrasound (US) application during the convective drying has been used as a novel method able to enhance drying rate and, consequently, to decrease drying time. In the present study, a new approach was tested to evaluate the effect of US on the drying time, the final antioxidant activity (AA) and the total polyphenol content (TPC) of banana slices (BS), mango slices (MS) and guava slices (GS). There were also studied the drying kinetics with nine different models from which water effective diffusivities (Deff) (with or without shrinkage corrections) were calculated. Compared with the corresponding control tests, US assisted drying for fruit slices showed reductions in drying time between 16.23 and 30.19%, 11.34 and 32.73%, and 19.25 and 47.51% for the MS, BS and GS respectively. Considering shrinkage effects, Deff calculated values ranged from 1.67*10-10 to 3.18*10-10 m2/s, 3.96*10-10 and 5.57*10-10 m2/s and 4.61*10-10 to 8.16*10-10 m2/s for the BS, MS and GS samples respectively. Reductions of TPC and AA (as DPPH) were observed compared with the original content in fresh fruit data in all kinds of drying assays., {"references":["FAO, \"The market for organic and fair-trade mangoes and pinneapples,\"\nno. September, pp. 4–9, 2009.","D. C. Restrepo-Sánchez, C. E. Narváez-Cuenca, and L. P. Restrepo-\nSánchez, \"ExtraccióN de compuestos con actividad antioxidante de frutos de guayaba cultivada en vélez-santander, Colombia,\" Quim. Nova,\nvol. 32, no. 6, pp. 1517–1522, 2009.","\"Guayaba, variables internacionales,\" Manual del exportador de frutas,\nhortalizas y tubérculos en Colombia, 2000. (Online). Available:\nhttp://interletras.com/manualcci/Frutas/Guayaba/guayaba02.htm.\n(Accessed: 23-Aug-2015).","F. a N. Fernandes, F. E. Linhares, and S. Rodrigues, \"Ultrasound as pretreatment\nfor drying of pineapple,\" Ultrason. Sonochem., vol. 15, no. 6,\npp. 1049–1054, 2008.","J. Gamboa-Santos, A. Montilla, J. A. Cárcel, M. Villamiel, and J. V.\nGarcia-Perez, \"Air-borne ultrasound application in the convective drying\nof strawberry,\" J. Food Eng., vol. 128, pp. 132–139, 2014.","K. Schössler, H. Jäger, and D. Knorr, \"Effect of continuous and\nintermittent ultrasound on drying time and effective diffusivity during\nconvective drying of apple and red bell pepper,\" J. Food Eng., vol. 108,\nno. 1, pp. 103–110, 2012.","A. S. Mujumdar, Handbook of industrial drying. CRC Press, 2014.","Q. Zhang and J. B. 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Se preparó una serie de películas de quitosano-gelatina variando la relación de los constituyentes, quitosano-gelatina entre 1:2, 1:5 y 1:10, con concentración total de biopolímeros entre 3,0%, 3,5%, 4,0% y pH de 5,5. Se deshidrataron los soportes por crioconcentración (congelaciones descongelaciones sucesivas) y secado convectivo con aire. La inmovilización de lipasa de Candida antarctica se realizó sobre un hidrogel entrecruzado iónicamente con quitosano por atrapamiento y por adsorción; los mejores resultados en cuanto a actividad enzimática y reutilización del soporte se obtuvieron con el método por atrapamiento. Se llevaron a cabo pruebas de caracterización fisicoquímica de los soportes, actividad del sistema biocatalítico y estabilidad. A set of chitosan-gelatin films were prepared by varying the chitosan-gelatin ratio between 1:2, 1:5 and 1:10, with total concentration of biopolymers from 3,0% 3,5%, 4,0 and pH of 5,5. We carried out the dehydration of the supports through cryoconcentration (successive freeze thawing) and convective drying with air. Immobilization of lipase from Candida antarctica was performed on an ionically crosslinked hydrogel with chitosan by entrapment and adsorption, getting the best results in terms of enzymatic activity and reuse of the support with the entrapment method. Tests of physicochemical characterization of the supports, biocatalytic system activity and stability were carried out. Uma serie de filmes de gelatina quitosana foi preparada variando a proporção dos componentes, a quitosana-gelatina entre 01:02, 01:05 e 01:10, com concentração total de biopolímeros de 3,0%, 3,5% 4,0% e pH de 5,5. Realizou-se a desidratação dos suportes por crioconcentração (ciclos sucessivos de descongelamento-congelamento) e secagem por convecção com o ar. A imobilização de lipase de Candida antarctica foi realizada em um hidrogel ionicamente entrecruzado com quitosana por adsorção e atrapamento, obtendo os melhores resultados em termos de atividade enzimática e reutilização do suporte com o método de atrapamento. Foram realizados testes de caracterização físico-química dos suportes, da atividade do sistema biocatalítico e da estabilidade.