# Concentrate Apple Juice Industry: Aroma and Pomace Valuation as Food Ingredients
###### Abstract  
Apple concentrate juice industry generates a flavored coproduct (apple aroma) recovered in the evaporation process, which is poorly valuated due to the lack of chemical characterization and standardization. In this study, industry apple aroma was characterized, allowing for the identification of 37 compounds, the majority esters (20), alcohols (7), and aldehydes (4). The storage temperature did not affect its volatile composition. Five key compounds were selected and monitored for 10 months of storage, and also compared with other three productions of another season allowing for observation of the same Aroma Index. Apple pomace was also used to produce a hydrodistillate. Contrary to the apple aroma, apple pomace hydrodistillate was unpleasant, reflected in a different volatile composition. Although no additional aroma fraction could be obtained from this wet byproduct, when dried, apple pomace presented 15 volatile compounds with toasted, caramel, sweet, and green notes. The infusions prepared with the dried apple pomace exhibited 25 volatile compounds with a very pleasant (fruity, apple-like, citrus, and spicy notes) and intense aroma. The addition of sugar changed the volatile profile, providing a less intense flavor, with almond, caramel, and sweet notes. These results show that apple aroma and pomace are high-quality flavoring agents with high potential of valuation as food ingredients. v 20  
higher, with respect to the inflow of raw material. The production of aroma concentrates can be achieved by different technologies, the most common are vapor-liquid separations based on distillation/evaporation or on partial condensation and gas injection-based separations. Other technologies less usual at industrial level are adsorption, supercritical fluid extraction, and pervaporation [2; 4]. The pervaporation uses a dilute apple essence, the aroma concentrates from vapor-liquid separations, to produce concentrated flavor products. The apple aroma can be used in both forms as more dilute or as a concentrated flavor product. Especially in the food and beverage industry, concentrated flavors are in demand due to prolonged shelf life, reduced packaging volume, and lower distribution and storage costs. This demand has triggered its industrial application. However, there are difficulties in the pervaporation concentration process to maintain the original flavor. The enrichment of the compounds differs from their chemical families, being the alcohols that had the lowest enrichment factors. The current concentration pervaporation methods are unable to keep exactly the original flavor after concentration; hence, flavor adjustments are necessary after concentration processes [5]. The obtention of a concentrated apple aroma with the presence of key flavor compounds is essential to restore the original fresh apple flavors to the final product. The vapor-liquid separations continue as the industrial technology most used, possibly to keep the original flavor of the aroma recovered, and its standardization over the processing. Several strategies for the valuation of apple pomace have been proposed. Apple pomace has been used directly for animal feed, as a source of food ingredients [6], for pectin recovery [1], for extraction of phytochemicals [1; 7], bioproduction of high value-added products, such as enzymes, organic acids, and biofuels [8], and the development of new materials as biocomposites and scaffold for tissue engineering [9]. However, for the retentate fewer applications have been proposed, such as bioproduction of citric acid [8; 10], insect diets [8], and as a nutritive medium for production of apple cider and feed formulations for racing pigeons [11]. Despite these different strategies, the perishable nature of these byproducts, due to their high water content and huge amounts of nutrients, makes its valuation difficult; to be profitable, it needs to be integrated into the plant production in order to use the byproducts immediately.