Extraction and Demulsification of Oil From Wheat Germ,Barley Germ,and Rice Bran Using an Aqueous Enzymatic Method

An aqueous enzymatic method was developed to extract oil from wheat germ. Wheat germ pretreatment, effect of various industrial enzymes, pH, wheat germ to water ratio, reaction time and effect of various methods of demulsification, were investigated. Pretreatment at 180 °C in a conventional oven for 4 min reduced the moisture 12.8–2.2 % and significantly increased the oil yield. Adding a combination of protease (Fermgen) and cellulase (Spezyme CP) resulted in a 72 % yield of emulsified oil from wheat germ (both commercial and laboratory milled wheat germ). Using the same oil extraction conditions optimized for wheat germ, yields of 51 and 39 % emulsified oil were obtained from barley germ (laboratory milled), and rice bran, respectively. Three physical demulsification methods (heating, freeze-thawing, and pH adjustment) and enzymatic methods (Protex 6L, Protex 7L, Alcalase, Fermgen, Lysomax and G-zyme 999) were compared. After demulsification with Protex 6L, free oil yields of 63.8 and 59.5 % were obtained with commercial wheat germ and with laboratory milled wheat germ, respectively. Using the same demulsification conditions optimized for wheat germ, yields of 45.7 % emulsified oil and 35 % free oil were obtained for barley germ and rice bran, respectively.     

Using Microwave Heating and Microscopy to Estimate Optimal Corn Germ Oil Yield with a Bench-Scale Press

The increase in ethanol production from corn has prompted development of processes to separate corn germ. The corn germ co-product would be a source of corn oil if a practical oil separation process were also developed. We carried out bench-scale corn-germ-pressing experiments to determine the maximum potential oil recovery which were then used to estimate commercial germ crushing costs. Corn germ was preheated in a microwave oven and oil was then extracted with a bench-scale press. Preheating the germ was necessary to obtain good oil yields. The uniform heating of the microwave oven more closely resembles compressive heating of commercial scale presses than does oven heating. Three different microscopic techniques were used to examine the effects of microwave and conventional-oven heating on corn germ. Microscopy revealed that microwave heating heated oil in the germ more quickly than the other components of the germ. Heating by both methods destroyed lipid body membranes and oil coalesced and pooled. Less oil could be pressed from germ initially containing 3–6% moisture than germ containing 15–20% moisture. Maximum oil recovery of about 65% was obtained for all germs tested when the optimum press temperature and germ feed moisture were used. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.     

Surfactant-Based Oil Extraction of Corn Germ

An aqueous surfactant-based extraction system was developed for the extraction of corn oil from corn germ with anionic extended surfactants. The surfactants used in this study were sodium linear-alkyl polypropoxylated polyethoxylated sulfates (C_12,14–P₁₀–E₂–SO₄Na and C₁₀–P₁₈–E₂–SO₄Na). Interfacial tension, critical microemulsion concentration (CμC), and optimum salinity values of the extended surfactants with corn oil were determined. In the extraction process, the ground corn germ was shaken with predetermined surfactant and salt concentrations at room temperature for 45 min. About 83%, the sum of total free oil and total oil-in-water emulsion, of the corn oil was extracted from the corn germ using a formulation of 0.4% C_12,14–P₁₀–E₂–SO₄Na and 1% NaCl. A solid/liquid ratio of 1/10 performed best for efficient oil recovery. The chemical compositions of the extracted corn oils were found to be similar to that of hexane extracted corn oil.     

Enzymatic Extraction of Wheat Germ Oil

In this study enzymatic extraction of oil from wheat germ (WG) was investigated. Four enzymes (Viscozyme L, Multifect CX 13L, Multifect CX GC and Alcalase 2.4L FG) were screened for their efficacy to release oil from WG. Alcalase 2.4L FG treatment of WG improved oil extraction yield as compared to a control (aqueous extraction without enzyme). Alcalase 2.4L FG, which resulted in significantly higher oil yield than the other three enzymes, was chosen for optimization of the enzymatic oil extraction process by using Response Surface Methodology (RSM). Three processing parameters, liquid/solid ratio, extraction time and enzyme concentration, were investigated as the independent variables. Based on the experimental results, the highest oil yield, 66.5% (w/w), was obtained under the following conditions; liquid/solid ratio 16.5, enzyme concentration 1.1% and extraction time 19.25 h. A cubic model with R ² of 0.91 was developed to describe the enzymatic extraction process. Although the cubic model predicted WG oil extraction yields well within the processing conditions studied in this study it was not effective beyond the experimental range. Further research focusing on high liquid/solid ratio, 16–20, and extraction time in 18–24 h and 0.5–5 h ranges is necessary to improve the model developed in this study.     

A comparison of commercial enzymes for the aqueous enzymatic extraction of corn oil from corn germ

An aqueous enzymatic method was developed to extract corn oil from corn germ. The basic steps in the method involved “churning” the corn germ with various enzymes and buffer for 4 h at 50°C, and an additional 16 h at 65°C, followed by centrifugation and removal of the oil layer from the surface. No hexane or other organic solvents are used in this process. By using oven-dried corn germ samples (6 g) from a commercial corn wet mill, corn oil yields of about 80% were achieved using three different commercial cellulases. A fourfold scale-up of the method (to 24 g of germ) resulted in oil yields of about 90%. Nine other commercial enzymes were evaluated and resulted in significant but lower oil yields. In the absence of enzymes, oil yields of 27 to 37% were achieved. The chemical compositions of hexane-extracted vs. aqueous enzymatic-extracted corn oils were very similar.     

The influence of moisture content and cooking on the screw pressing and prepressing of corn oil from corn germ

Samples of corn germ were obtained from a commercial corn wet mill (factory dried to about 3% moisture) and a commerical corn dry mill (undried, produced in the mill with about 13% moisture). The germ samples (200 g each) were cooked for various times in either a conventional oven at 180°C or a microwave oven at 1500 W. Bench-scale single screw pressing was then performed. With the dry milled corn germ, no oil was obtained from the uncooked germ. A maximal yield of about 5% oil [26% of total oil recovery (TOR), relative to hexane extraction] was obtained by cooking the dry-milled germ for 6.5 min in a conventional oven at 180°C before pressing. A maximal yield of about 7% oil (37% TOR) was obtained by cooking the dry-milled germ for 4.5 min in a microwave oven at 1500 W before pressing. With the wet-milled germ, yields of about 7% oil (18% TOR) were obtained with the uncooked germ and yields increased to a maximum of about 22% oil (56% TOR) by cooking in a conventional oven at 180°C for 5 min or a maximum of about 17% oil (44% TOR) by cooking for 4 min in a microwave oven at 1500 W. These results indicate that microwave and conventional oven cooking are both effective pretreatments before pressing. Microwave preheating resulted in higher oil yields with dry-milled germ, and conventional oven pretreatment resulted in higher oil yields with factory-dried wet-milled corn germ.     

A Comparison of the Levels of Lutein and Zeaxanthin in Corn Germ Oil,Corn Fiber Oil and Corn Kernel Oil

All commercial corn oil is obtained by pressing corn germ and/or extracting the germ with hexane. In the current study, six types of corn oil were prepared by extracting corn germ, corn fiber and ground corn, each with hexane or with ethanol. The levels of lutein, zeaxanthin and other carotenoids were quantitatively analyzed in the six corn oils. The levels of lutein + zeaxanthin in the oil ranged from 2.3 μg/g for hexane-extracted corn germ oil to 220.9 μg/g for ethanol-extracted ground corn oil. These results indicate that a diet that includes 30 g (~2 tbsp) per day of the unrefined corn oil obtained by extracting ground corn with ethanol would provide ~6 mg of lutein + zeaxanthin, the daily dosage that is currently considered to be necessary to slow the progression of age-related macular degeneration. Mention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the U.S. Department of Agriculture.     

Foam Separation of Oil from Enzymatically Treated Wet-Milled Corn Germ Dispersions

More than 9 billion gallons of ethanol were produced in 2008, mostly from dry grind corn fermentation plants. These plants are a potential source of substantial amounts of corn oil, if an economical method of separating it can be developed. In this work, oil was separated from corn germ by aqueous enzymatic extraction (AEE). Batches of wet-milled corn germ in water were preheated in a pressure cooker, ground in a colloid mill, and churned in a vertical column/mixing vessel system, after the addition of enzyme. Nitrogen gas was then bubbled through the column removing an overflowing foam fraction which was subsequently centrifuged to separate free oil. Using a newly commercialized enzyme complex it was found that 80% of the oil could be recovered using a w/w ratio of enzyme solution to germ of 1:80. The low dose and low price of the enzyme complex leads to a cost estimate of AEE of corn oil from germ, similar to the wet-milled germ extracted, cost competitive with expelled oil (with the separation and drying of the foam protein), and feasible for commercialization in a dry grind plant retrofitted to separate germ.     

促进玉米秸秆酶解效率的化学预处理方法比较

分别用八种化学方法对玉米秸秆进行预处理,将预处理后的试样用纤维素酶在最优条件下催化水解,初步比较了不同的化学方法在促进玉米秸秆酶解糖化方面的效果。通过比较各试样酶解后产糖量大小,得到最佳的预处理方案:采用0.176%(m/V)NaOH及0.9%(V/V)H2O2混合液在常温下按固液比1∶50振荡作用24 h,即在纤维素酶用量为50 FPU/g时,产糖量可从0.055 g/g提升到0.333 g/g,提高了83.51%;此时的木质素降解量亦为最大,达到了49.8%,此结果表明木质素的降解有利于纤维素酶敏感性的提高。     

Fatty Acid,Phytosterol, and Polyamine Conjugate Profiles of Edible Oils Extracted from Corn Germ,Corn Fiber,and Corn Kernels

This study compared the profiles of fatty acids, phytosterols, and polyamine conjugates in conventional commercial corn oil extracted from corn germ and in two “new-generation” corn oils: hexane-extracted corn fiber oil and ethanol-extracted corn kernel oil. The fatty acid compositions of all three corn oils were very similar and were unaffected by degumming, refining, bleaching, and deodorization. The levels of total phytosterols in crude corn fiber oil were about tenfold higher than those in commercial corn oil, and their levels in crude corn kernel oil were more than twofold higher than in conventional corn oil. When corn kernel oil was subjected to conventional degumming, refining, bleaching, and deodorization, about half of the phytosterols was removed, whereas when corn fiber oil was subjected to a gentle form of degumming, refining, bleaching, and deodorization, only about 10% of the phytosterols was removed. Finally, when the levels of polyamine conjugates (diferuloylputrescine and p-coumaroyl feruloylputrescine) were examined in these corn oils, they were only detected in the ethanol-extracted crude corn kernel oil, confirming earlier reports that they were not extracted by hexane, and providing new information that they could be removed from ethanol-extracted corn kernel oil by conventional degumming, refining, bleaching, and deodorizing.     

Optimization of the Aqueous Enzymatic Extraction of Wheat Germ Oil Using Response Surface Methodology

A process of aqueous enzymatic extraction of wheat germ was carried out by a multi-enzyme preparation consisting of cellulase, pentosanase, neutrase and fungal amylase (CPNF, 2:1:2:1 w/w/w/w). Hydro-thermal heating (at 112 °C for 60 min) was more effective than oven-drying regarding emulsified oil yield. Wheat germ was ground with a rate of 10,000 rpm for 90 s. The adding level (w/w) of multi-enzyme preparation of CPNF was 1.6%. Response surface methodology was used to obtain the desired data in the process optimization. The optimal set of variables was water to wheat germ ratio (v/wt, mL/g) of 3.46, pH of 5.24, temperature of 48.49 °C and time of 6 h. The emulsified oil yield was 86.74% at the optimal levels of the tested factors. Compared with organic solvent extracted oil, the content of free fatty acid of AEE extracted oil was higher and the color was slightly darker, while the peroxide value was lower and the oxidative stability was higher owing to high content of α-tocopherol. This technique for recovering oil from fresh wheat germ with enzymes is a significant improvement in both oil yield and quality over the traditional organic solvent process.     

Enzymatic pretreatment on rose-hip oil extraction: Hydrolysis and pressing conditions

In a previous report [Zúñiga, M.E., J. Concha, C. Soto, and R. Chamy, Effect of the Rose Hip (Rosa aff. rubiginosa) Oil Extraction Cold-Pressed Process, in Proceedings of the World Conference and Exhibition on Oilseed Processing, and Utilization, edited by R.F. Wilson, AOCS Press, Champaign, 2001, pp. 210–213], the authors showed that an enzymatic pretreatment of rose-hip seeds, prior to oil extraction by cold pressing, improves the oil yield. In this work, we studied the effects of temperature and moisture during the enzymatic hydrolysis stage using two previously selected mixtures of commercial enzymes: (i) Olivex (mainly pectinase) plus Cellubrix (mainly cellulase), and (ii) Finizym (mainly β-glucanase) plus Cellubrix (mainly cellulase) (all from Novozymes A/S, Madrid, Spain). In addition, we evaluated the effect of enzymatic hydrolysis on the oil extraction pressing rate at different operational pressures. Samples hydrolyzed enzymatically by either of the two commercial enzyme mixtures at 45°C and 30–40% moisture showed oil extraction yields up to 60%, an increase of greater than 50%, as compared with control samples in which the enzyme solutions were replaced by water. Both the oil extraction rate and yield by pressing increased when enzymatic pretreatment was applied. The oil extraction yield increased slightly when the operation pressure was elevated; however, when the sample was preheated, the oil extraction yield was greatly increased, especially for enzyme-treated samples. Results confirmed the importance of temperature and moisture as enzymatic hydrolysis parameters that improve rose-hip oil extraction yields in the cold-pressing process. When pressing was carried out after preheating enzymatically treated samples, it was possible to increase the oil extraction yield to 72% compared with the control without preheating, which resulted in a 46% oil yield.     

Effect of Moisture and Heat Treatment of Corn Germ on Oil Quality

The changes in the quality of crude corn oil caused by moisture and two different thermal pretreatments (oven heating and steam heating) of wet‐milled corn germ were evaluated and compared with those of untreated oil. Increasing the moisture content of the corn germ from 8 to 25% before oil extraction increased the acid value (AV) (3.02–4.01 mg KOH g^?1), peroxide value (PV) (0.52–1.05 meq kg^?1), and the red value (7.3–8.7) and decreased the content of total tocopherols by 37% and that of γ‐tocopherols by 31%. Oven heating tended to decrease the AV and PV while steam heating significantly increased the total and individual tocopherol contents (P < 0.05). The different moisture contents and thermal pretreatments of corn germ caused no significant differences in the fatty acid composition and the contents of total and individual phytosterols of the crude oils. The γ‐tocopherol contents were found to be highly correlated with the red values (the corresponding R² reached 0.9977 and 0.9089 for moisture and heat pretreatments, respectively).     

The Composition of Crude Corn Oil Recovered after Fermentation via Centrifugation from a Commercial Dry Grind Ethanol Process

A study was conducted to examine the chemical composition of corn oil obtained after fermentation of corn to make fuel ethanol via centrifugation and compare its composition to that of corn germ oil (commercial corn oil) and experimental corn oils. The levels of free fatty acids in the post fermentation corn oil were high (11–16%), as previously reported. The levels of free phytosterols and hydroxycinnamate steryl esters (similar to oryzanol in rice bran oil) were higher than those of corn germ oil and were comparable to those of ethanol-extracted corn kernel oil. The levels of tocopherols were lower in post-fermentation oil than in either corn germ oil or ethanol extracted corn kernel oil. The levels of lutein and zeaxanthin in post-fermentation were much higher than those in corn germ oil and were comparable to those in ethanol-extracted corn kernel oil. Overall, exposure to all upstream processes of a fuel ethanol plant, including high-temperature liquefaction, saccharification and fermentation appeared to have the most notable effect on tocopherols, but it had little effect on the levels of free phytosterols, hydroxycinnamate steryl esters, lutein and zeaxanthin. It may be desirable to recover these valuable functional lipids prior to using the post-fermentation corn oil for industrial applications such as making biodiesel if a cost-effective recovery process can be developed.     

Composition and economic comparison of germ fractions from modified corn processing technologies

Several new processes for milling corn have been developed recently specifically to isolate germ as a value-added co-product and improve the profitability of dry-grind ethanol production. The present work used modified and conventional corn milling technologies to recover germ fractions from corn kernels using either wet or dry separation processes. This study determined the quality, composition, and yield differences among the corn germ produced and compared these properties with those of the conventional wet- and dry-milled germ. A method for calculating the estimated market value for germ produced by the alternative processing methods is given. There were significant differences in the oil, protein, starch, and ash compositions and in the estimated market values among germ fractions produced by the alternative milling processes. The different germ fractions produced (including the traditional wet-and dry-milled) were found to contain 18–41% oil, 13–21% protein, and 6–21% starch, depending on the milling process used. The estimated value of germ from these processes varied from as low as $0.058/lb ($0.128/kg) to a maximum of $0.114/lb ($0.251/kg), showing that the specific process used to produce the germ will have the major impact on the overall economics of the ethanol process.     

The composition of corn oil obtained by the alcohol extraction of ground corn

All commercial corn oil is obtained by the hexane extraction of corn germ. The chemical composition of commercial corn oil has been well characterized. This study was under-taken to quantitatively evaluate the lipid composition of corn oil obtained by the ethanol extraction of ground, whole corn kernels. When corn oil was obtained by extracting ground corn kernels (ground corn) with polar or nonpolar solvents, the resulting corn oil contained much higher levels of hydroxycinnamate steryl esters (≈0.3%) than those found in commercial hexane-extracted corn (germ) oil (≈0.02%). The levels of valuable tocopherols and tocotrienols were also significantly higher in kernel oil than in traditional corn germ oil. We previously reported that when corn oil was obtained by extracting corn kernels with polar solvents, the oil contained two polyamine conjugates, diferuloylputrescine and p-coumaroyl feruloylputrescine. In the current study, when ground corn was extracted with ethanol, the resulting corn oil contained about 0.5% diferuloylputrescine and about 0.2% p-coumaroyl feruloylputrescine. This is the first study to quantify these unique compounds in corn oil extracted by new techniques. This compositional information is important because this new oil is being considered for human food use.     

Extraction and Functional Properties of Non-Zein Proteins in Corn Germ from Wet-Milling

This study was conducted to evaluate the extractability of wet-milled corn germ protein, characterize the recovered protein and identify its potential applications. Protein was extracted from both wet germ and finished (dried) germ using 0.1 M NaCl as solvent. The method involved homogenization, stirring, centrifugation, dialysis and freeze-drying. Factors evaluated were temperature (40, 50, or 60 °C) and the presence of reducing or denaturing agents. The recovered protein was analyzed for proximate composition and functional properties. Protein recovery was greater from wet germ. For both germ samples, protein recovery was not improved by using higher temperatures; thus, subsequent extractions were done at 40 °C. Addition of 2% SDS and 1% β-mercaptoethanol to the solvent nearly doubled protein yield; but, SDS-PAGE indicated some protein denaturation. The recovered freeze-dried proteins from both germ samples were least soluble at pH 2.0–4.0, but solubility increased at higher pH values. Wet germ protein extract was more soluble than finished germ protein at all pH values; however, the finished germ protein showed much better foaming and emulsifying properties and water-holding capacity.     

A Novel Method for the Production of Biodiesel from the Whole Stillage-Extracted Corn Oil

The extraction of corn oil from whole stillage and condensed distillers’ solubles (CDS) with hexane and its conversion to biodiesel were investigated. The analysis of the extracted oil showed 6–8 wt.% free fatty acid (FFA) in this oil. Acid, base, acid–base, and acid–base catalyzed transesterifications with intermediate neutralization with anion exchange resin were investigated. Experiments were performed with model corn oil substrates which contained 1.0–6.0 wt.% FFA. The effect of catalyst at 0.50–1.25 wt.% was studied at a 1:8 oil/methanol molar ratio. At 6.0 wt.% FFA concentration, the acid-catalyzed scheme was slow and resulted in less than 20% yield after 4 h, while the base-catalyzed was mostly consumed by the FFA and very little conversion was achieved. The acid–base catalyzed scheme succeeded in reducing the FFA content of the oil through the acid-catalyzed stage, and yields in excess of 85% were achieved after the second stage of the reaction with a base catalyst. However, formation of water and soap prevented the separation of product phases. An alternative acid–base catalyzed scheme was examined which made use of a strong anion exchange resin to neutralize the substrate after the initial acid-catalyzed stage. This scheme resulted in the effective removal of the acid catalyst as well as the residual FFA prior to the base-catalyzed stage. The subsequent base-catalyzed stage resulted in yields in excess of 98% for a 7.0 wt.% FFA corn oil and for the corn oil extracted from CDS.     

Enzymatic Epoxidation of Corn Oil by Perstearic Acid

Epoxidized vegetable oils can be used as renewable biodegradable and non-toxic lubricants, polymer stabilizers, and as intermediates. In this study, as a renewable resource, corn oil rich in oleic and linoleic acids, which was epoxidized using hydrogen peroxide as an oxygen donor and stearic acid as an active oxygen carrier in the presence of Novozym 435. The process was optimized for the enzymatic epoxidation of corn oil with an epoxy oxygen group content of 5.8 ± 0.2% and a percentage relative conversion to oxirane of 85.3 ± 2.9% under the following conditions: 35 °C, 28% stearic acid load (relative to the weight of corn oil), 2.7:1 mol ratio of H₂O₂/C=C-bonds, and 10 h. The influence on the enzymatic epoxidation decreased in the order of stearic acid load > reaction temperature ≈ mole ratio of H₂O₂/C=C-bonds >reaction time.     

Preparation of plastic fats with zero <Emphasis Type="Italic">trans</Emphasis> FA from palm oil

A series of plastic fats containing no trans FA and having varying melting or plastic ranges, suitable for use in bakery, margarines, and for cooking purposes as vanaspati, were prepared from palm oil. The process of fractionating palm oil under different conditions by dry and solvent fractionation processes produced stearins of different yields. Melting characteristics of stearin fractions varied depending on the yield and the process. The lower-yield stearins were harder and had a wider plastic range than those of higher yields. The fractions with yields of about 35% had melting profiles similar to those of commercial vanaspati. The plastic range of palm stearins was further improved by blending them with corresponding oleins and with other vegetable oils. The plasticity or solid fat content varied depending on the proportion of stearin. Blends with higher proportions of stearins were harder than those with lower proportions. the melting profiles of some blends, especially those containing 40–60% stearin of about 25% yield and 40–60% corresponding oleins or mahua or rice bran oils, were similar to those of commercial vanaspati and bakery shortenings. These formulations did not contain any trans FA, unlike those of commercial hydrogenated fats. Thus, by fractionation and blending, plastic fats with no trans acids could be prepared for different purposes to replace hydrogenated fats, and palm oil could be utilized to the maximum extent.