Abstract
The effect of osmotic treatments with sucrose solutions (45 and 65%), applying or not vacuum impregnation and calcium lactate (1%) on papaya quality, was studied in order to analyse the viability of this technology to obtain minimally processed papaya. Osmotic dehydration (OD) kinetics was studied on papaya slices. The effect of osmotic treatments on different fruit properties (physicochemical, optical, mechanical, respiration rate, microbiological stability) was analysed. To this aim, papaya slices were osmodehyrated until 20ºBrix were reached in the liquid phase.
Kinetic study revealed that the effective transport property of papaya tissue and process yield increased when diluted osmotic solution was used, and vacuum pulse and calcium were applied. From this point of view, the most recommendable treatments are at atmospheric pressure, by using 45º Brix sucrose, with calcium lactate. Osmotic treatments implied changes in transparency, luminosity and chrome when they are applied with vacuum pulse, but no effect on optical properties were observed due to other factors. To better preserve the product texture, samples must be treated with diluted solutions containing calcium at atmospheric pressure. These aspects made the treatments with 45ºBrix sucrose, containing calcium, at atmospheric pressure recommendable.
Osmotic dehydration provoked changes in the respiration rate of the tissue, depending on process conditions. Pulsed vacuum treatments involved greater limitations on oxygen transport, thus leading to higher values of the respiration ratio, and favouring anaerobic routes. Microbiological growth started 3 days later in osmodehydrated samples, as compared to fresh.