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.

Characterization and Demulsification of the Oil-Rich Emulsion from the Aqueous Extraction Process of Almond Flour

The aqueous extraction process (AEP) allows the concurrent extraction of oil and protein from almond flour without the use of harsh solvents. However, the majority of the oil extracted in the AEP is present in an emulsion that needs to be demulsified for subsequent industrial utilization. The effects of scaling-up the AEP of almond flour from 0.7 to 7 L and the efficiency of enzymatic and chemical approaches to demulsify the cream were evaluated. The AEP was carried out at pH 9.0, solids-to-liquid ratio of 1:10, and constant stirring of 120 rpm at 50 °C. Oil extraction yields of 61.9% and protein extraction yields of 66.6% were achieved. At optimum conditions, enzymatic and chemical demulsification strategies led to a sevenfold increase (from 8 to 66%) in the oil recovery compared with the control. However, enzymatic demulsification resulted in significant changes in the physicochemical properties of the cream protein and faster demulsification (29% reduction in the incubation time and a small reduction in the demulsification temperature from 55 to 50 °C) compared with the chemical approach. Reduced cream stability after enzymatic demulsification could be attributed to the hydrolysis of the amandin α-unit and reduced protein hydrophobicity. Moreover, the fatty acid composition of the AEP oil obtained from both demulsification strategies was similar to the hexane extracted oil.

Effects of Processing Conditions on the Simultaneous Extraction and Distribution of Oil and Protein from Almond Flour

The enzyme-assisted aqueous extraction process (EAEP) is an environmentally friendly strategy that simultaneously extracts oil and protein from several food matrices. The aim of this study was to investigate the effects of pH (6.5–9.5), temperature (45–55 °C), solids-to-liquid ratio (SLR) (1:12–1:8), and amount of enzyme (0.5–1.0%) on the extraction and separation of oil and protein from almond flour using a fractional factorial design. Oil and protein extraction yields from 61 to 75% and 64 to 79% were achieved, respectively. Experimental conditions resulting in higher extractability were subsequently replicated for validation of the observed effects. Oil and protein extraction yields of 75 and 72% were achieved under optimized extraction conditions (pH 9.0, 50 °C, 1:10 SLR, 0.5% (w/w) of enzyme, 60 min). Although the use of enzyme during the extraction did not lead to significant increase in extraction yields, it did impact the extracted protein functionality. The use of enzyme and alkaline pH (9.0) during the extraction resulted in the production of more soluble peptides at low pH (5.0), highlighting possible uses of the EAEP skim protein in food applications involving acidic pH. The implications of the use of enzyme during the extraction regarding the de-emulsification of the EAEP cream warrant further investigation.

Aqueous and Enzymatic Extraction of Oil and Protein from Almond Cake: A Comparative Study

The almond cake is a protein- and oil-rich by-product of the mechanical expression of almond oil that has the potential to be used as a source of valuable proteins and lipids for food applications. The objectives of this study were to evaluate the individual and combined effects of solids-to-liquid ratio (SLR), reaction time, and enzyme use on oil and protein extraction yields from almond cake. A central composite rotatable design was employed to maximize the overall extractability and distribution of extracted components among the fractions generated by the aqueous (AEP) and enzyme-assisted aqueous extraction process (EAEP). Simultaneous extraction of oil and protein by the AEP was favored by the use of low SLR (1:12.82) and longer reaction times (2 h), where extraction yields of 48.2% and 70% were achieved, respectively. Increased use of enzyme (0.85%) in the EAEP resulted in higher oil (50%) and protein (75%) extraction yields in a shorter reaction time (1 h), compared with the AEP at the same reaction time (41.6% oil and 70% protein extraction). Overall, extraction conditions that favored oil and protein extraction also favored oil yield in the cream and protein yield in the skim. However, increased oil yield in the skim was observed at conditions where higher oil extraction was achieved. In addition to improving oil and protein extractability, the use of enzyme during the extraction resulted in the production of skim fractions with smaller and more soluble peptides at low pH (5.0), highlighting possible uses of the EAEP skim in food applications involving acidic pH. The implications of the use of enzyme during the extraction regarding the de-emulsification of the EAEP cream warrant further investigation.