Oil from oilseeds can be extracted by mechanical extraction (pressing), aqueous extraction, or by extraction with organic solvents. Although solvent extraction is the most efficient method, organic solvents are a potential hazard to the life and health for workers as well as to the environment, when solvent vapors are released and act as air pollutant with a high ozone forming potential. Pressing is safer, environmentally friendly, and it preserves valuable natural components in the resulting oils. The problems associated with pressing are the high energy consumption and the lower yield on oil extraction, because the applied mechanical force does not completely destroy the structural cell components storing the oil. In seed cells, the oil is contained in the form of lipid bodies (oleosomes) that are surrounded by a phospholipid monolayer with a protein layer on the surface. These lipid bodies are further protected by the seed cell walls consisting mainly of polysaccharides such as pectins, hemicelluloses and cellulose, but also of glycoproteins. The use of hydrolases to degrade these barriers is a promising pretreatment strategy to support mechanical extraction and improve the oil yield. It is advisable to use a combination of enzymes different activities when considering the multicompartment and multicomponent structure of oilseed cells. This article gives an overview on the microstructure and composition of oilseed cells, reviews enzymes capable to destroy oil containing cell compartments, and summarizes the main parameters of enzymatic treatment procedures, such as the composition of the enzyme cocktail, the amount of enzyme and water used, temperature, pH, and the duration. Finally, it analyzes the efficiency of proteolytic, cellulolytic, and pectolytic enzyme pretreatment to increase the yield of mechanically extracted oil from various types of vegetable raw materials with the main focus on oilseeds.
The pretreatment of pumpkin seeds with proteolytic, cellulolytic and pectolytic enzymes and their effect on cell structure and oil yield was studied. Pumkin seed samples were treated with pepsin, papain, Viscozyme L, cellulase or pectinase. The evaluation of cell integrity by immediate hexane extraction (shaking method) showed that all samples treated with different enzymes had a higher oil yield, ranging from 33.2 to 34.1 % of seed weight, than the control samples (32.1 %). The number of disrupted cells was also higher than the control (64.4%), ranging from 67.6 to 69.5 %. The highest percentage of disrupted cells, 71.0 and 71.1 %, was found in samples treated with pepsin+Viscozyme L+pectinase and pepsin+cellulase+pectinase mixtures, respectively. To study the effect of enzymatic pretreatment on the microstructure of pumkin seeds, ultramicrotome slices of pumpkin seeds were treated with individual enzymes and enzyme mixtures. The highest percentage of cell destruction was observed in samples treated with Viscozyme L and the mixture of pepsin+Viscozyme L+pectinase. The yield of pressed oil from pumpkin seeds pretreated with the pepsin+Viscozyme L+pectinase mixture was 7.0 % higher than that of control samples. The quality parameters, chemical composition and antioxidant activity of pressed oils were investigated and the enzymatic pretreatment did not significantly affect the free fatty acid content, peroxide value, fatty acid composition, or phytosterol profiles. The antioxidant activity expressed as DPPH° radical scavenging effect of the enzymatically pretreated pressed oil was 2.7 % higher than that of the sample not pretreated with enzymes.
The influence of parameters of pumpkin seeds pretreatment with enzyme preparations of proteolytic and cellulolytic activity on the yield of press oil, its composition and quality parameters were studied in this work. The enzyme preparation PENICILOPEPSIN (Enzym Biotech, Ukraine) with proteolytic activity and CELLULAD (Enzym Biotech, Ukraine) with cellulolytic, hemicellulase and xylanase activity were used for pretreatment. Enzymatic treatment of seeds was carried out with a mixture of these preparations at a ratio of 7:3 for 2 h at a pH 5.2 and 48—54°C. The following parameters of enzymatic pretreatment were studied: the amount of the enzyme mixture, which varied from 0.3% to 2.4% of the weight of the seeds and the amount of moisture added together with the enzymes — from 15% to 50%. It was established that the rational parameters of the enzymatic treatment of pumpkin seeds are the mass of the enzyme mixture of 0.6% and the amount of moisture added with enzymes — 35% of the seed mass. Under such technological parameters, the yield of press pumpkin oil was 65.6%, which is almost 6% higher than in the control sample. The acid and anisidine value of the control oil sample and the oil extracted after the enzymatic treatment of the seeds did not differ significantly. However, the content of peroxide compounds in the oil extracted after enzymatic treatment of seeds was lower. The total antioxidant activity of the oil, determined by the reaction of the 2,2-diphenyl-1- picrylhydrazyl radicals quenching within 30 min, was higher in the oil samples after seed pretreatment at the maximum tested moisture (50%). The obtained results indicate that the enzymatic pretreatment of pumpkin seeds with proteolytic and cellulolytic enzyme preparations is a promising method of oil yield increasing.
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