Impact of Power Ultrasound on the Quality of Fruits and Vegetables During Dehydration
In the present work, the influence of power ultrasound (US) on the quality of fruits and vegetables during both the pre-treatment and drying has been evaluated. Chemical indicators such as pectinmethyl esterase and peroxidase enzymes, vitamin C, carbohydrates, proteins, polyphenols and 2-furoylmethylamino acids (indicators of the early stages of Maillard reaction) have been studied. Fruits and Vegetables Dehydration

During blanching, similar leaching losses and enzyme inactivation were found in low temperature and prolonged conventional treatments and in US processes, but with a significant reduction in the time for the latter.
Finally, application of US in drying of carrots and strawberries originated significant reductions in processing time, while providing high quality end-products. The quality was higher as compared to marketed products and superior or equivalent to samples obtained under similar conditions in a prototype convective dryer, and, in the case of some indicators, similar to that of freeze-dried samples.
To ensure that the constituents of foods exert a beneficial health effect, it is necessary the evaluation and authentication of the benefit of the compound and the knowledge of the changes that can take place during the processing of food and its subsequent storage. In this sense, it is important to apply processes that maintain nutritional and organoleptic properties and bioactivity.
As raw materials, carrots and strawberries were selected because of their high consumption and healthy and nutritious properties due to high content in bioactive constituents. In order to evaluate the quality and bioactivity of these dehydrated products, different quality indicators were selected: polyphenol oxidase (POD), pectinmethylesterase (PME), vitamins, compounds of the initial stages of Maillard reaction (MR) (2-furoylmethyl
amino acids, 2-FM-AA), polyphenols, carbohydrates, proteins, rehydration, microstructure and sensory properties.
According to the results found, in general, it can be considered, that samples of carrot and strawberry dehydrated under the effect of the US showed a higher quality than the commercial samples. Depending on the indicators used, the quality was equivalent to the samples dried by convection in similar conditions and even, in some aspects, tofreeze-dried samples.