Abstract
In this work, the effect of pulsed electric field (PEF) pre-treatment on the extractability in green solvents (i. e., ethanol–water mixture and propylene glycol) of target aroma and bioactive compounds, such as vanillin from vanilla pods, theobromine and caffeine from cocoa bean shells, linalool from vermouth mixture, and limonene from orange peels, was investigated. The effectiveness of PEF as a cell disintegration technique in a wide range of field strength (1–5 kV/cm) and energy input (1–40 kJ/kg) was confirmed using impedance measurements, and results were used to define the optimal PEF conditions for the pre-treatment of each plant tissue before the subsequent solid–liquid extraction process. The extracted compounds from untreated and PEF-treated samples were analyzed via GC-MS and HPLC-PDA analysis. Results revealed that the maximum cell disintegration index was detected for cocoa bean shells and vanilla pods (Zp = 0.82), followed by vermouth mixture (Zp = 0.77), and orange peels (Zp = 0.55). As a result, PEF pre-treatment significantly enhanced the extraction yield of the target compounds in both solvents, but especially in ethanolic extracts of vanillin (+14%), theobromine (+25%), caffeine (+34%), linalool (+114%), and limonene (+33%), as compared with untreated samples. Moreover, GC-MS and HPLC-PDA analyses revealed no evidence of degradation of individual compounds due to PEF application. The results obtained in this work suggest that the application of PEF treatment before solid–liquid extraction with green solvents could represent a sustainable approach for the recovery of clean labels and natural compounds from aromatic plants and food by-products.
Highlights
Nowadays, the food, pharmaceutical, and cosmetic industries are continuously striving to meet the evolving consumer demands for clean labels and natural compounds with functional and health beneficial properties [1, 2]
Pulsed electric field pre-treatment of orange peels remarkably enhanced the limonene content in the ethanolic extracts as compared with the control extraction, while a slight but not significant (p > 0.05) increase was detected in the case of glycolic extracts (Table 3)
The results of this work demonstrated that the application of pulsed electric field (PEF) pre-treatment of moderate intensity (3–5 kV/cm) and relatively low energy input (15–40 kJ/kg) before solid liquid extraction (SLE) with green solvents, such as ethanol–water mixture and propylene glycol, can represent an environmentally friendly approach to intensify the extractability of valuable intracellular compounds, such as linalool from vermouth mixture, limonene from orange peels, vanillin from vanilla pods, and theobromine and caffeine from cocoa bean shells
Summary
The food, pharmaceutical, and cosmetic industries are continuously striving to meet the evolving consumer demands for clean labels and natural compounds with functional and health beneficial properties (flavorings, colorants, antioxidants) [1, 2] In this line, the plant extracts market is increasingly catching on, and the preferences for natural products are expected to drive its growth during the coming years [3]. Apart from its aroma, vanillin and vanilla extracts have been reported to have beneficial properties, such as antioxidant, anti-mutagenic, hypolipidemic, and anticarcinogen activity [4]. Another widespread valuable flavor compound is linalool, which represents approximately 70% of the terpenoids of a wide variety of herbal scents [5]. Several studies have been published reporting different biological activities of linalool, such as central nervous system depressant effects, as well as analgesic and anti-inflammatory activities [5, 7]
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