Impact of freeze-drying shelf temperature on the bioactive compounds, physical properties and sensory evaluation of a product based on orange juice

Freeze-drying is a good alternative means of obtaining fruit products, with a significant amount of thermolabile bioactive compounds. Despite the excellent benefits, this method provides the dehydrated product, and its main drawback is its high cost due to the duration of the process. Heat may be applied to the shelf so as to shorten the process time, as long as this does not affect the quality of the product. In this study, the impact of the freeze-drying shelf temperature, 30 and 50 degrees C, on the bioactive compounds of the product obtained from an orange juice formulated with gum Arabic and bamboo fibre has been considered, as has the temperature's effect on the porosity, colour and mechanical properties of the cake and on the flowability and the rehydration capacity of the powder, together with the sensory evaluation of the rehydrated product. The results obtained point to 50 degrees C as being the recommended temperature for the freeze-drying of this product. This temperature shortens the process time by 64%, promotes the vitamin C content with no effect on the total phenols and carotenoids, leads to the cakes having better mechanical properties and does not affect the flowability and the rehydration behaviour of the powdered product.