Efficient degumming of crude canola oil using ultrafiltration membranes and bio-derived solvents

Abstract

Vegetable oils derived from rapeseed and its genetic variant canola, are conventionally extracted from oilseeds by means of an organic solvent, typically hexane. Concerns regarding the toxicity of hexane have meant safer and more environmentally friendly solvents such as terpenes are becoming attractive. In this research, the degumming of canola oil/terpene mixtures using ultrafiltration is considered as a critical step in such an extraction process. Polysulfone (PSF) and polyethersulfone (PES) membranes were found to be ineffective in this application, as the oil appeared to cause swelling of the membrane structure. This meant that the original flux could not be restored after cleaning. Conversely, a ceramic membrane (MWCO 5 kDa) provided stable behaviour over several cycles of operation when cleaned with pure solvent at high cross velocity at 40 °C. This membrane showed high phospholipid retention (95±2 %), although some oil was also retained (16±3%). Cymene emerged as the most attractive of the three terpenes tested, with higher permeate flux and phospholipid rejection than limonene or pinene. Industrial Relevance: While hexane has been traditionally used for oilseed extraction, toxicity concerns are likely to restrict its industrial use in the future. This article provides information to engineers and food scientists on the use of terpenes as an alternative solvent. In particular, the potential for ultrafiltration to be used in degumming of canola oil/terpene mixture is assessed. Our research shows that polymeric membranes are unlikely to be useful at scale in this application, as they are not readily cleaned for reuse. Conversely, a ceramic membrane of 5 kDa pore size provides the necessary rejection of phospholipids. There is some oil retention, that might require a downstream recovery step. The best results were obtained with cymene, suggesting this is a good target for industrial use.

Membrane technology for vegetable oil processing—Current status and future prospects

“…Bioderived terpene solvents have also been proposed as alternative solvents for vegetable oil extraction and included in the membrane processing studies (Abdellah et al, 2018(Abdellah et al, , 2019(Abdellah et al, , 2020. Among the three terpenes (pinene, limonene, and cymene) tested in the desolventizing experimentations, the best performance of 86% oil rejection with a miscella flux of 5.5 L/m 2 /h was achieved while processing 30% limonene-canola oil miscella (Abdellah et al, 2019).…”

“…In a study with ceramic (alumina) membranes, Abdellah et al. (2020) disclosed that a 5 kDa membrane rejected approximately 95% PL, reducing the residual phosphorus content to <10 mg/kg in the canola oil while exhibiting a miscella flux of 32 kg/m 2 /h. Further, an oil rejection of approximately 15% was reported in the study, which is seldom highlighted by other researchers.…”

“…However, more systematic research efforts are required to demonstrate the prospects of MEUF as a single‐step pretreatment for various types of crude oils. Besides, another challenge observed with the MEUF is the associated undesirable oil rejection (15‐20%), necessitating a diafiltration step for complete oil recovery from the reject stream (Abdellah et al., 2020). Alternatively, it may be prudent to examine whether any acid/alkali treatment of miscella followed by centrifugal separation or MF would be a better proposition.…”

“…Cleaning of polymeric membranes employed in nonaqueous applications has not received adequate attention. Stable degumming performance has been demonstrated in a 5 kDa ceramic membrane over several cycles of operation when cleaned with hexane at a high cross-flow velocity at 40 • C (Abdellah et al, 2020). Some of the polymeric membrane manufacturers also suggest rinsing with pure process solvent at a higher permissible temperature while recommending the users to develop a protocol suiting the specific application (Tyndall T, personal communication, June 27, 2021).…”

Modern Methods of Degumming of Vegetable Oils: An Analytical Review

“…В неполярних розчинах основні поверхнево-активні речовини олійфосфоліпіди, утворюють зворотні міцели із середньою молекулярною масою близько 20000 Da, що є істотно більшим за розміри триацилгліцеринів (900 Da). Тому їх можна розділити ультрафільтрацією із застосуванням відповідних мембран з адекватною селективністю [34]. Для мембранного гідратування використовують полімерні (полівініліденфториди (PVDF), поліетиленсульфони (PES) [33]) та керамічні мембрани [35].…”