Refining of edible oils: a critical appraisal of current and potential technologies

Abstract

Summary The major sources of dietary lipids are edible oils, which include both vegetable and fish oils. Crude oil extracted from vegetable and fish sources contain mono‐, di‐, triacylglycerols along with impurities, which necessitates refining. The main objective of refining is to remove the contaminants that adversely affect the quality of oil, thereby reducing the shelf life and consumer acceptance. However, this refining process needs to be tailored as the composition of crude oil is highly variable, depending upon the plant/fish species, geographical location of the source and method of oil extraction. Recently, extensive efforts have been made to develop refining technology, using either conventional physical/chemical processes or several unconventional processes including biological and membrane processes. The first section of this review gives a brief description of general composition of some commonly used vegetable and fish oils, followed by the review of various refining methods and their effects on the oil constituents. Finally, an effort is made to understand the technological gaps in the existing methods and possible directions of research to overcome the said gaps.

A New Strategy to Refine Crude Indian Sardine Oil

“…Degumming is the initial step in edible oil refining which removes phospholipids and some portion of trace metals and mucilaginous substances 9 . Sardine oil was degummed through an acid degumming process by considering various acids like OPA, LA and AC.…”

“…Chemical refining has many disadvantages such as high-energy demand, nutrient loss, need for large quantities of water and chemicals, and disposal of polluted effluents. Enzymatic treatment employed to refine the crude oil is effective and ecofriendly, but seldom applied for industrial purposes due to cost constraints 9 .…”

“…However, reports on the use of solvent extraction for FFA removal in marine oils are rather scarce. Although membranes could be used in principle, for all the stages of refining of oils, not much work has been reported 9 . Couple of reports are available on solvent extraction coupled with membranes for FFA removal from synthetic mixture of FFA and triglycerides 14 and groundnut oil 15 .With the expectation of preserving the greater part of nutrients, the membrane process carried out at low temperatures and with the elimination of a substantial number of unit operations as compared to conventional processes, appears highly viable, principally due to the total adequateness of this new technology with respect to environmental questions 16 .…”

Lipase mediated synthesis of rutin fatty ester: Study of its process parameters and solvent polarity

“…However, this theory has recently faced challenges, as some studies report inconsistent results. This was attributed to the wide variation in the fatty acid and triglyceride content in bulk oil systems (Vaisali, Charanyaa, Belur, & Regupathi, 2015). Further study of bulk oil revealed colloidal structures with many hydrophilic and hydrophobic regions.…”

Enzymatic lipophilization of epicatechin with free fatty acids and its effect on antioxidative capacity in crude camellia seed oil

“…Crude camellia seed oil also contains plenty of free fatty acids, which must be removed to obtain an oil of acceptable quality. In conventional edible oil‐refining steps, free fatty acids are precipitated as soaps and removed by alkali refining during deacidification . However, the soapstock can hold neutral oil, which leads to losses.…”