Pervaporation: The emerging technique for extracting aroma compounds from food systems

Highlights

• Pervaporation meets the requirements for the recovery of aromas.

• PV is able to recover over 70 different aroma solutes.

• The agro-food products are recorded as a potential source of aromas.

• PDMS, PEBA and POMS are the most used organophilic membranes.

Abstract

To date, according to the latest literature inputs, membrane-based technologies have demonstrated to meet the recovery of several high-added-value compounds from agro-food products. Particularly, Pervaporation (PV), as a highly selective membrane technique, has demonstrated its ability in separating specific solutes like aroma compounds, which represent a current research challenge for food, cosmetic and pharmaceutical industries. The goal of this paper is to provide a critical overview of the ongoing development works aimed at extracting aroma compounds and their derivatives from their original sources. The literature data is shown, analyzed and discussed in relation to the separation process, molecule properties, membrane characteristics and key factors affecting the performance of such technology. Particular attention is paid to experimental results reported in the most recent findings. In addition, the generalities of PV, as well as the theoretical aspects and its role in separation, are also provided.

Introduction

Today, there is a growing demand for technological innovation for the manufacturing of flavors and fragrances ingredients aimed to be used in the food, cosmetic and pharmaceutical industries (Brazinha and Crespo, 2014, Castro-Muñoz, 2018). Flavours and fragrances are a widely group of chemicals (comprising more than 22 000 individual molecules), including short-chain alkanes and alkenes (with or without oxygen, nitrogen, or sulfur), alcohols, esters, ketones, and organic acids. It is likely that the terpenes are most abundant category of chemical in nature, which are responsible for characteristic odours in plants, fruits, fungi, and animals (Feron et al., 1996). Typically, these organic compounds are part of the manufacture procedures of many foods, feeds, personal care, perfumery, household products, and beverages (Castro-Muñoz and Fíla, 2018, Lukin et al., 2018), to mention just a few. To satisfy the current demand of such compounds, their production indeed deals via chemical stock, which implies several reaction steps needing expensive chiral educts and (expensive) catalysts. However, there is a current big necessity of replacing such artificial aromas with aromas extracted from natural sources based on the ‘’chemophobia’’ of consumers (Cataldo et al., 2016). At this point, there are two possible ways to naturally produce them, e.g. biosynthesis (through biotechnological approaches) (Chreptowicz et al., 2016) or extract them from natural sources (Saffarionpour and Ottens, 2018). It is likely that the best option is the extraction/recovery from natural agro-food products (e.g. fruits, vegetables, processed foods, extracts, and so on) by means of separation techniques. To date, several recovery techniques have been proposed for such a task, as Fig. 1 depicts.

Primarily, all these techniques need the availability of the compounds in aqueous or solvent systems to perform the separation. However, the recovery is not an easy task according to the reactivity and stability of selected flavor and aroma compounds (see Table 1), indeed, most of these organic compounds may present hydrolysis, oxidation and radical reaction, and thermal degradation (Castro-Muñoz et al., 2016, Kimura et al., 1982, Weerawatanakorn et al., 2015).

Table 1. Structure of some selected reactive aroma and flavor compounds commonly contained in agro-food products.

In particular, the use of some conventional techniques, which may imply the use of solvents (or additional phase/agent) or temperature, reduce their possibility of obtaining high recover rates (Brazinha and Crespo, 2009). As stated previously, the recovery rate depends crucially on their chemical stability. At this point, pervaporation (PV), as a membrane-based technology using a selective barrier for the separation, can be used in principle in absence of temperature (e.g. at room temperature) or some other additional phases to carry out the recovery. PV has emerged as a promising technology for several types of applications, such as assisting chemical reactions (Castro-Muñoz et al., 2018b), separation of azeotropic mixtures (Castro-Muñoz et al., 2018c, Delgado et al., 2009), dehydration of solvents (Castro-Muñoz et al., 2018d, Kudasheva et al., 2015), process intensification (Khudsange and Wasewar, 2017, Ma et al., 2009), and recovery of specific organic solutes (Lukin et al., 2018, Saffarionpour and Ottens, 2018). Thanks to its intrinsic properties, PV is a current tool to improve the currently adopted valorisation protocols, within a sustainable biorefinery strategy, with remarkable improvements of the environmental and economic sustainability of the overall approach (Brazinha et al., 2009, Kujawski, 2000, Santoro et al., 2017). Over the last decades, the implementation of PV process in chemical, food and pharmaceutical applications has increased remarkably, as evidenced by the number of scientific publications in those fields (Fig. 2). When dealing with the recovery of valuable solutes, PV offers several advantages over conventional separation/purification techniques (e.g. distillation, evaporation, adsorption, absorption, solvent extraction), including relatively easy operation, feasible scale-up, reduced number of processing steps and low energy consumption (Lukin et al., 2018). As early mentioned, the non-use of chemical agents or solvents helps to preserve the functional properties of the flavor and aroma compounds, as well as to reduce any risk of product contamination. On the other hand, the main disadvantages of the PV technology deal with the need of purified feed stream and the low permeation fluxes, which may be enhanced by temperature, but compromising the selectivity towards the compounds (Vane, 2005).

Thereby, the aim of this review paper is to provide a critical overview of the ongoing development works aimed at extracting aroma and flavor compounds, as well as their derivatives, from their original sources by means of PV. The literature data are shown, analyzed and discussed in relation to the molecule properties, membrane characteristics and key factors that influence during the performance of such technology. Particular attention is paid to experimental results reported in the most recent findings. In addition, the generalities of PV, as well as the theoretical aspects and its role in separation, are also provided as a key strategy for the recovery of such high-added- value compounds.