Carla Brazinha

Sustainable recovery of pure natural vanillin from fermentation media in a single pervaporation step

The recovery of vanillin from aqueous media by organophilic pervaporation is studied and optimised. Vanillin is recovered as a pure solid free of contaminants in a single pervaporation step. Due to the high-boiling point of this compound its transport across the pervaporation membrane is controlled by the desorption step at the downstream surface of the membrane. Under these circumstances, it is concluded that higher fluxes of vanillin may be achieved if the dense top layer of the composite membrane used in this process faces the downstream compartment. This procedure minimises the local drop of the partial pressure of vanillin at the downstream surface of the membrane, avoiding the formation of solid deposits of vanillin at the membrane. A low downstream pressure must be used in order to keep an appropriate driving force for transport. The use of organophilic pervaporation for the direct recovery of natural vanillin from post-fermentation media is demonstrated, at the temperature of fermentation in a solvent-free process, assuring the quantitative recovery of pure vanillin free of other media constituents.

Membrane processing: Natural antioxidants from winemaking by-products

Winemaking by-products are a low-cost and rich source of valuable phenolic compounds with widely recognised health benefits. Membrane separation processes are ideal for recovering these compounds, ensuring high quality of the extracts produced. As a result of the gentle nature of membrane processing, the final products can justify the label ‘natural’, which is essential for most food and cosmetic markets. Carla Brazinha explains.

Selective extraction of natural products with benign solvents and recovery by organophilic pervaporation: fractionation of D-limonene from orange peels

There has been a growing awareness of the need to replace volatile organic compounds (VOCs) by benign solvents aiming to implement more sustainable processes. Accordingly, this work aims at evaluating a new and more friendly process based on the use of benign solvents with different hydrophobicities, namely common alimentary oil, polypropylene glycol and polyethylene glycol, for the selective recovery of natural products, followed by pervaporation. Particularly, the extraction and fractionation of limonene from orange peels was studied and optimised, where a high value product is obtained from a highly abundant material that is mostly disposed. Firstly, the best benign solvents were selected, in order to obtain high yields of extraction, and then pervaporation and vacuum distillation were compared after the extraction process, in order to obtain high yields of global recovery of limonene with the least contaminants possible. The integrated process selected was the extraction of limonene from orange peels using polypropylene glycol 240 (PPG), followed by organophilic pervaporation, providing the selective recovery of limonene free of solvent.

Optimization of Extraction of Bioactive Compounds from Different Types of Grape Pomace Produced at Wineries and Distilleries

UNLABELLED Natural extracts obtained from grape pomace are particularly interesting, due to the substantial variety of valuable compounds present with health benefits, specifically phenolic compounds such as anthocyanins, trans-resveratrol, quercetin, and proanthocyanidins. The production of such extracts has been recognized as a profitable way to valorize grape byproducts, which are low-value and most abundant. First, the effect of the solvent on the extraction of bioactive compounds from grape pomace is studied. The selected solvents are water and ethanol, biocompatible and available in wineries and distilleries. Then, different types of grape pomace obtained along the various stages of current industrial winemaking and distillation processes are analyzed. As a result, the best stage of the winemaking and distillation processes for pomace valorization is identified, corresponding to the grape byproduct with the highest potential as source of bioactive compounds. These studies were performed with Vitis vinifera variety of Tempranillo grapes (same year, same vineyard). PRACTICAL APPLICATION This work optimizes the production of natural extracts from (byproduct) grape pomace with recognized health benefits, to be used as high value nutraceuticals ingredients. The process proposed uses renewable and low-cost resources existent in wineries and distilleries. The select solvent extracting is a mixture of the biocompatible water and ethanol. The selected fermented grape pomace was chosen from different and comparable types of grape pomace obtained at current winemaking and distillation processes, to be used in extraction without any pretreatment.

Fundamentals of pervaporation

Abstract Pervaporation is a membrane separation process that allows for the selective transport of solutes present in liquid mixtures. This process has particularly unique and adequate features to remove volatile compounds present in liquid mixtures at trace levels. This chapter discusses the fundamental aspects of transport phenomena in pervaporation processes by describing the mass transport mechanism involved, commonly explained by the sorption–diffusion model. This chapter also addresses fundamental problems that should be considered when designing a pervaporation process and when defining its operating conditions.

Membranes for ethanol dehydration

Abstract The global economy is completely dependent on energy. As an alternative to fossil fuels, bioethanol is unquestionably the most promising renewable fuel. However, bioethanol requires low contamination values of water (0.3% at maximum) for this application, so the dehydration of bioethanol is mandatory. Among available techniques, pervaporation is preferred owing to its energy-saving, cost-effective, and environmentally friendly qualities. To convert pervaporation in a competitive process for bioethanol dehydration, new membranes need to be developed with high permeability and selectivity combined with good chemical and mechanical stability at high temperatures, at a reasonable cost. Thus, the pursuit for the perfect membrane will continue within the scientific community.