Comparación de dos técnicas de deshidratación de guayaba-pera (Psidium guajava L.) sobre los efectos del contenido de vitamina C y el comportamiento de las propiedades técnico-funcionales de la fibra dietaria

Introduction: "Pear" guava is, nationally, a very important fruit, given its production levels and its nutritional value. Its high humidity content makes this fruit highly perishable, so it requires conservation processes. Dehydration by drying and lyophilization are two techniques currently being used to dehydrate fruits and each one has certain benefits for the product and for its operative costs. Objective. Compare the effects of lyophilization and forced convection drying on the technical and functional properties of the dietary fiber (DF) and on the vitamin C content of the "pear" guava (Psidium guajava L.). Materials and methods. "Pear" guavas at a 6 maturity level, according to the color table, were chosen and dehydrated by means of convection drying, evaluating five different temperatures (30, 40, 50, 60 and 70°C), and also dehydrated by means of lyophilization, evaluating four freezing times (6, 12, 18 and 24 hours). Vitamin C was quantified by the use of the 2-nitroaniline method and the following technical-functional properties of the DF were determined: swelling capacity (SC), water retention capacity (WRC) and lipid adsorption capacity (LAC). Results. The biggest loss of vitamin C took place in the dehydration by drying at 60 and 70 °C and -in a general way- the best results for the behavior of the technical and functional properties were obtained during the dehydration by lyophilization. Conclusion. Despite the fact that some of the properties evaluated had no significant differences in some of the treatments, this study concludes that in the dehydration by lyophilization, which freezing process was performed during six hours, the "pear" guava had higher technical and functional characteristics while the drying treatment at 40 °C and the lyophilization by freezing during 24 hours allowed a better conservation of the vitamin C.