Emerging Green Technologies for Processing Oil-seeds
Author: Vipin Chandra Kalia

Introduction

The major crops as the source of edible oil are mustard, groundnut, castorseed, safflower, linseed, nigerseed, soybean and sesamum. The demand for edible oils is increasing globally. Interestingly, the difference between demand and supply is around 75%. The most obvious answers to overcome this problem are: (i) increase production by increasing land usage, and/or (ii) efficient extraction processes. The likely hood of increased availability of land for oilseed crop production is very low. However, efficiency of the extraction process can be achieved. Hence, the focus is on the latter option. The most prevalent processes for oil recovery are: (i) hydraulic pressing, (ii) expeller pressing, and (iii) solvent extraction. Among these methods used for oil extraction, solvent extraction is easy and instant but is limited by the high solvent cost and adds to environmental hazards. The use of n-hexane as a solvent leads to air pollution, and toxicity.


Green Technologies for Edible oil extraction

Green technologies use green solvents as alternatives to hexane, which is not an eco-friendly solvent. The green solvents can be obtained from: (i) water and CO2 combination, (ii) terpenes from agricultural materials like citrus peels, tree oils, pine forests, Schisandra chinensis Baill fruit, soy bean flakes, and (iii) petroleum products.

Enzyme based oil-seed processing are emerging as the most eco-friendly techniques. These enzymatic treatment processes enhance the efficiency of extraction by allowing higher oil recovery and maintaining higher nutritive value. Aqueous Enzymatic Extraction uses water as a medium for oil extraction. Emulsified oil in water is de-emulsified by either changing the temperature or by using enzymes.

The major enzymes used on oilseeds are amylases, proteases and cellulases. For cellulases, the best source is Trichoderma viridi, and for extracting hemicelluases – Aspergilus niger and A. fumigatus can be used. Bacillus spp. are a good source for obtaining proteases. In comparison to using enzymes individually, better oil yields have been reported with mixtures of enzymes. These are used at 0.1 to 3% (w/w) and operate at room temperature to 70 ˚C and enable 86-96% of oil extraction from rapeseed, soyabean, coconut, Avocado, sunflower, peanut. A few other examples are as follows: (i) Palm fruit treated with Pectinase, cellulase, tannase resulted in 35.9% oil yield, (ii) Pea nut oil yields were 13 to 42% with Alcalase, Protizyme or Viscozyme L, (iii) Multifect CX13L and Neutral led to 9.5 and 20% oil from Canola seeds and Soybean flakes, respectively, (iv) mixture of Pectinase, cellulase and B-glucanase produced 43.8% oil from Rapeseed slurry, (v) Neutrase and Termamyl produced 12.8% oil from Moringa oleifera seeds, (vi) pomegranate seed-oil by treating with cellulase and Peclyve V.

Oil extraction for experimental purposes is done by various methods such as soxhlet, sonication, microwave, Accelerated Solvent Extraction, Super Critical Fluid Extraction, etc. These processes require 15-500 mL of solvent and may take up to 48 h to complete. A modified cold percolation method, which takes 2-3 minutes to complete was demonstrated with: i) mustard, ii) sunflower, iii) groundnut and (iv) Safflower seeds. It needed only 1 g of seeds and the 50 mL of solvent (Diethyl ether) used could be easily recovered and reused.

Unique selling points

The major advantages of the enzyme based processes are: (i) eco-friendly, simple, inexpensive, etc., (ii) the need to degumming is eliminated, (iii) separates out phospholipids from oil, (iv) helps in refining the free fatty acids, (v) reduced burden on environment (less BOD and COD), and vi) eliminates toxins and anti-nutritional factors.

References:

1. Goula AM, Papatheodorou A, Karasavva S, Kaderides K (2017) Ultrasound-assisted aqueous enzymatic extraction of oil from pomegranate seeds. Waste and Biomass Valor. doi: 10.1007/s12649-016-9740-9
2. Kalia VC, Lal S, Rashmi (2002) Modified cold percolation method for extracting oil from oil seeds. J Sci Ind Res 61(8):630-634.
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About Author / Additional Info:
Researcher in Microbial Biotechnology and Genomics at CSIR-IGIB, Delhi.