New approach for the elucidation of the phenomena involved in the operation of vegetable oil extraction presses

In a context where the search for naturalness, the need to reduce the carbon footprint and the development of a decentralized crushing sector are intensifying, mechanical extraction is a technology that is regaining major importance for the industry. The performance of this technique remains far below what is desirable, while the understanding of the main phenomena involved in screw presses remains insufficient. This article, after a brief presentation of the state of the art of this discipline, presents a new model centered on the notions of pressure generation and plasticity. According to this approach, plasticity can account for parameters such as the water and oil content of oilseeds, their temperature, and their possible dehulling. Plasticity in turn would explain both the compressibility of the cake and its ability to resist the thrust of the screws, and consequently to generate pressure or to creep or flow backward depending on the geometry of the screw and the cage. The model must also incorporate the notions of compression velocity, friction, and the complexity of the interactions between these parameters and the impact of the succession of screw segments and cone rings. It has been built on observation and experience and gives an understanding of the need to work simultaneously on the conditioning and geometry of the presses to achieve improved performance in terms of energy, efficiency, and reduction of the temperatures experienced by the proteins and oils

Extended surfactants and their tailored applications for vegetable oils extraction: An overview

The vegetable oil extraction process from seeds and nuts depends on mechanical and solvent (usually n-hexane) extractions. Despite the efficiency of n-hexane, its use is nowadays questioned due to health, environmental, and technological issues. As an alternative to hexane extraction, several greener solvents and extraction techniques have been developed and tested during the last decades. Among these alternatives, the Surfactant-Aqueous Extraction Process (SAEP) appears as a promising method. Initially developed for the petroleum sector, this method was then tested and optimized for vegetable oil extraction. Successful implementations at the laboratory scale led to slightly more than 90% oil yield, mainly by using so-called “extended surfactants”. Compare to conventional surfactants, these surfactants can efficiently solubilize a large amount of vegetable oil in water, despite the structural diversity and the bulkiness of vegetable oil molecules. The present review is devoted to extended surfactant applications to SAEP. This review summarizes and discusses the main findings related to the extended surfactant structures and properties, as well as the main experimental results on the SAEP, and the advantages and the current limitations towards a scaling-up of this promising process.

Purification and Characterization of a Unique Pectin Lyase from Aspergillus giganteus Able to Release Unsaturated Monogalacturonate during Pectin Degradation

A pectin lyase, named PLIII, was purified to homogeneity from the culture filtrate of Aspergillus giganteus grown in submerged culture containing orange peel waste as carbon source. PLIII was able to digest apple pectin and citrus pectins with different degrees of methyl esterification. Interestingly, the PLIII activity was stimulated in the presence of some divalent cations including Pb2+ and was not significantly affected by Hg2+. Like other pectin lyases, PLIII is stimulated by but is not dependent on Ca2+. The main soluble product released during the degradation of pectic substances promoted by the PLIII is compatible with an unsaturated monogalacturonate. PLIII is a unique enzyme able to release unsaturated monogalacturonate as the only soluble product during the degradation of pectic substances; therefore, PLIII was classified as an exo-pectin lyase. To our knowledge, this is the first characterization of an exo-pectin lyase. The PLIII described in this work is potentially useful for ethanol production from pectin-rich biomass, besides other common applications for alkaline pectinases like preparation of textile fibers, coffee and tea fermentation, vegetable oil extraction, and the treatment of pulp in papermaking.