Vacuum Drying Optimization and Simulation as a Preservation Method of Antioxidants in Apple Pomace

Abstract

Vacuum drying optimum conditions and lowest energy consumption were investigated by surface response methodology and process simulation in Aspen Plus. Temperature, time and vacuum pressure effects on moisture, effective diffusivity, polyphenols and antioxidant capacity were evaluated. As a result, temperature was the most significant variable controlling the different responses. Optimum drying conditions were 68.33C, 46.33 kPa (abs) and 4.27 h. Dried apple pomace was obtained with 10% final moisture, 2.44 mg gallic acid equivalent/g as total polyphenolic content and 98.59 μmol Trolox equivalent/g as oxygen radical absorbance capacity. From simulation results, lower energy demand (1.2 kWh/kg of pomace) was obtained compared with other drying methods. Sensitivity analyses showed that apple pomace inlet temperature and apple pomace moisture content impacted energy requirements, whereas pressure and temperature adjustments inside the dryer did not. As a result, vacuum drying might be a feasible alternative to preserve antioxidants in apple pomace. Practical Applications Currently, there is an interest for developing economically feasible processes capable of recovering polyphenols from apple pomace in order to use such compounds in the food industry. Research has been performed regarding the optimization of polyphenols' solvent extraction. Preservation operations such as drying are critical before extraction. Vacuum drying is known as an efficient technique when processing temperature‐sensitive materials such as polyphenols. So far, there is no research available regarding vacuum drying effects in apple pomace polyphenols and antioxidant capacity. Because of this, this paper contributes to fill this gap, so the industry can implement this kind of process in the near future with the minimum negative effects in the polyphenolic and antioxidant capacity available; all this while having an efficient vacuum drying process.

Apple pomace as food fortification ingredient: A systematic review and meta‐analysis

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Apple Pomace as Potential Source of Natural Active Compounds

“…Apple pomace consists of apple peels, leftover flesh, core with seeds, and stems. The moisture content after pressing is about 70-85 % [4][5][6][7] and makes the pomace prone to microbial infestation. This can be used in the field of solid-state fermentation but should be avoided when intended for other applications.…”

“…1 Approximate composition of dried apple pomace. Data provided by studies of different pomace sources [5,6,8,13,14,16,22,26,37,54,56,55] were partly averaged and normalized to 100 %.…”

“…The first factor to influence the extractable number of polyphenols is the drying process. Vacuum drying is generally regarded as a better alternative to oven drying as it preserves higher polyphenol contents [6]. However, this is not the case for anthocyanins and flavanols [8].…”

“…Cutical constituents of apple present in apple pomace. Cutin (2), the triterpenoids ursolic acid (3), oleanolic acid (4), coumaroyl-and cinnamylderivatives of ursolic and oleanolic acid (5), uvaol(6), and erythrodiol(7).…”