Lawrence A. Johnson

Use of branched-chain esters to reduce the crystallization temperature of biodiesel

To reduce the tendency of biodiesel to crystallize at low temperatures, branched-chain alcohols were used to esterify various fats and oils, and the crystallization properties of the branched esters were compared with those of methyl esters by using differential scanning calorimetry (DSC), cloud point, and pour point. Compared with the methyl esters that are commonly used in biodiesel, branched-chain esters greatly reduced the crystallization onset temperature (TCO) of neat esters and their corresponding ester diesel fuel blends. Isopropyl and 2-butyl esters of normal (∼10 wt% palmitate) soybean oil (SBO) crystallized 7–11 and 12–14°C lower, respectively, than the corresponding methyl esters. The benefit of the branched-chain esters in lowering TCO increased when the esters were blended with diesel fuel. Esters made from a low-palmitate (3.8%) SBO crystallized 5–6°C lower than those of normal SBO. Isopropyl esters of lard and tallow had TCO values similar to that of methyl esters of SBO. DSC provided an accurate means of monitoring crystallization, and the DSC results correlated with cloud and pour point measurements.

Fuel properties and emissions of soybean oil esters as diesel fuel

The effects of using blends of methyl and isopropyl esters of soybean oil with No. 2 diesel fuel were studied at several steady-state operating conditions in a four-cylinder turbocharged diesel engine. Fuel blends that contained 20, 50, and 70% methyl soyate and 20 and 50% isopropyl soyate were tested. Fuel properties, such as cetane number, also were investigated. Both methyl and isopropyl esters provided significant reductions in particulate emissions compared with No. 2 diesel fuel. A blend of 50% methyl ester and 50% No. 2 diesel fuel provided a reduction of 37% in the carbon portion of the particulates and 25% in the total particulates. The 50% blend of isopropyl ester and 50% No. 2 diesel fuel gave a 55% reduction in carbon and a 28% reduction in total particulate emissions. Emissions of carbon monoxide and unburned hydrocarbons also were reduced significantly. Oxides of nitrogen increased by 12%.

Reducing the Crystallization Temperature of Biodiesel by Winterizing Methyl Soyate

Methyl soyate, made from typical soybean varieties, has a crystallization onset temperature (Tco) of 3.7°C and, as a biodiesel fuel, is prone to crystallization of its high-melting saturated methyl esters at cold operating temperatures. Removal of saturated esters by winterization was assessed as a means of reducing theTco of methyl soyate. Winterizing neat methyl esters of typical soybean oil produced aTco of −7.1°C, but this was not an efficient way of removing saturated methyl esters because of the low yield (26%) of the separated liquid fraction. However, aTco of −6.5°C with 86% yield was obtained by winterizing the neat methyl esters of a low-palmitate soybean oil; aTco of −5.8°C with 77% yield was obtained by winterizing methyl esters of normal soybean oil diluted with hexane.

Isolation of Amaranth Starch by Diluted Alkaline-Protease Treatment

ABSTRACT Starch was isolated from Amaranthus cruentus seeds by different alkaline treatments and combinations of low alkaline steeping and protease treatments. For low alkaline-protease treatments, amaranth seeds were steeped in a NaOH solution (0.05%, pH 12) for 22 hr to loosen the protein matrix and ground. The pH of the ground slurry was adjusted to 7.5 and subjected to a protease (from Aspergillus sojae) treatment. The slurry was incubated with 1 or 0.5% of the protease (based on total amount of seeds) for 2 hr at 37°C and 50 rpm. The starch was then isolated by screening and centrifugation. This method produced starch with a low protein content (≤0.2%) and a high recovery (≈80%). Amaranth starch isolated by alkaline treatments were also studied by using various concentrations of NaOH steeping solutions and with or without alkaline solution during grinding and washing. The properties of amaranth starch isolated by alkaline and low alkaline-protease treatments were analyzed and compared. The properties...

Demulsification of oil-rich emulsion from enzyme-assisted aqueous extraction of extruded soybean flakes.

Extraction of soybean oil from flaked and extruded soybeans using enzyme-assisted aqueous extraction processing (EAEP) is a promising alternative to conventional hexane extraction. The efficiencies of four proteases releasing oil from extruded material were compared. Protex 51FP, Protex 6L and Protex 7L each extracted 90% of the total oil available while Protex 50FP gave similar extraction yield as the control (without enzyme treatment). During EAEP, however, a stable emulsion forms that must be broken in order to recover free soybean oil. The potential of various proteases and phospholipases to destabilize the emulsion was determined. Two enzymes, a phospholipase A2 (LysoMax) and a protease (Protex 51FP) were selected to determine the effect of enzyme concentration on demulsification. Although at a 2% concentration (w/w, enzyme/(cream+free oil)), each enzyme tested was effective in totally destabilizing the cream; the protease released significantly more free oil than did the phospholipase at concentrations less than 2%. At 0.2% concentration, 88 and 48% of free oil were obtained with the protease and phospholipase, respectively. Reducing the pH of the cream also destabilized the cream with maximum demulsification at the isoelectric point of soy proteins. These results provide destabilization strategies for the oil-rich emulsion formed during aqueous extraction processing of extruded flakes and significantly contribute to the development of this environmentally-friendly technology.

Factors affecting emulsion stability and quality of oil recovered from enzyme-assisted aqueous extraction of soybeans

The objectives of the present study were to assess how the stability of the emulsion recovered from aqueous extraction processing of soybeans was affected by characteristics of the starting material and extraction and demulsification conditions. Adding endopeptidase Protex 6L during enzyme-assisted aqueous extraction processing (EAEP) of extruded soybean flakes was vital to obtaining emulsions that were easily demulsified with enzymes. Adding salt (up to 1.5 mM NaCl or MgCl(2)) during extraction and storing extruded flakes before extraction at 4 and 30 degrees C for up to 3 months did not affect the stabilities of emulsions recovered from EAEP of soy flour, flakes and extruded flakes. After demulsification, highest free oil yield was obtained with EAEP of extruded flakes, followed by flour and then flakes. The same protease used for the extraction step was used to demulsify the EAEP cream emulsion from extruded full-fat soy flakes at concentrations ranging from 0.03% to 2.50% w/w, incubation times ranging from 2 to 90 min, and temperatures of 25, 50 or 65 degrees C. Highest free oil recoveries were achieved at high enzyme concentrations, mild temperatures, and short incubation times. Both the nature of enzyme (i.e., protease and phospholipase), added alone or as a cocktail, concentration of enzymes (0.5% vs. 2.5%) and incubation time (1 vs. 3 h), use during the extraction step, and nature of enzyme added for demulsifying affected free oil yield. The free oil recovered from EAEP of extruded flakes contained less phosphorus compared with conventional hexane-extracted oil. The present study identified conditions rendering the emulsion less stable, which is critical to increasing free oil yield recovered during EAEP of soybeans, an environmentally friendly alternative processing method to hexane extraction.

Effect of Low-Shear Extrusion on Corn Fermentation and Oil Partition

To study oil distribution in fermentation liquid and solids for the purpose of recovering oil from corn stillage by centrifugation, a low-shear single-screw extruder was used to treat corn for dry-grind ethanol fermentation. Five different treatments for corn were used, and their effects on ethanol fermentation, oil distribution, and oil extractability were studied. Extruded corn with different particles sizes had similar ethanol yields (33% based on corn) because the starch was equally gelatinized by extrusion. Pretreatment with larger particle size before extrusion tended to have higher free oil than pretreatment with smaller particle sizes, but the effect was not dramatic, which indicates that manipulating particle size has limited effect on oil distribution in the liquid. Autoclaved flaked corn had lower ethanol yield because autoclaving at 28% moisture did not fully gelatinize the starch. Addition of protease and cellulase significantly increased the ethanol yield by at least 4%. A significant amount of bound oil became more extractable after enzyme treatment. Such oil can be effectively extracted into liquid phase by using a surfactant. In general, oil tended to be strongly associated with the solids in the thin stillage. By enzymatic treatment, 70% oil distribution was achieved in the thin stillage, compared to the conventional fermentation, where only 50% oil goes into the liquid. It was also demonstrated that mass loss after fermentation can be used to accurately quantify ethanol yield.

Comparison of laboratory and pilot-plant corn wet-milling procedures

ABSTRACT One waxy and three regular yellow dent corn hybrids were wet milled by using two scales of laboratory procedures (modified 100-g and 1-kg) and a pilot-plant procedure (10-kg). The modified 100-g and 1-kg laboratory procedures gave similar yields of wet-milling fractions. Starch yields and recoveries were significantly lower for the pilot-plant procedure, whereas gluten and fiber yields were greater because of their high contents of unrecovered starch. Protein contents of the starches obtained by all three procedures were within commercially acceptable limits (<0.50% db for normal dent corn and <0.30% for waxy corn). Rankings for starch yields and starch recoveries for the four hybrids, having very different physical and compositional properties, were the same for all three procedures. The harder the grain, the lower the yield and recovery of starch. Least significant differences (P < 0.05) for starch yield were 0.8% for the modified 100-g procedure, 1.2% for the 1-kg procedure, and 2.0% for the p...

Functional properties of protein extracted from flaked, defatted, whole corn by ethanol/alkali during sequential extraction processing

Functional properties (solubility, foaming capacity and stability, emulsifying capacity, emulsion stability, heat coagulability, heat gelation and film formation) of protein extracted by 45% ethanol/55% 0.1 M NaOH from flaked, defatted, undergermed corn during the Sequential Extraction Process (SEP) were evaluated and compared with those of a laboratory-prepared soy protein concentrate. SEP is a new approach to corn fractionation that recycles the ethanol produced from the fermentation of cornstarch to unstream steps of protein extraction and the simultaneous extraction of corn oil and dehydration of the ethanol. Freeze-dried corn protein extracts contained at least 80% crude protein (dry basis), which is indicative of protein concentrates. SEP protein concentrates had solubilities in water of greater than 80% at pH values of 7 or above and were significantly more soluble than the soy protein concentrate at pH above 3. SEP corn proteins also showed better heat stabilities and greater emulsifying capacities and emulsion stabilities. Dilute dispersions (0.1%) of corn protein produced substantial but less stable foams. Corn proteins produced films similar to zein and soy protein films but were unable to form heat-induced gels. These results indicate that SEP produces a protein concentrate with functional properties suitable for food and industrial uses.

Factors affecting yield and composition of zein extracted from commercial corn gluten meal

ABSTRACT Twelve corn gluten meal samples obtained from six wet-milling plants were processed into zein. Zein was extracted using 88% aqueous isopropyl alcohol at pH 12.5, followed by chilling. Protein recovery ranged from 21.3 to 32.0%, and protein purity ranged from 82.1 to 87.6%. Protein recovery increased as the protein purity increased (r = 0.76) (P < 0.01). One of the major factors influencing extraction yield was protein composition; especially α-zein content, which ranged from 53.4 to 64% of the total protein in the corn gluten meal samples. The intensity of red color of the corn gluten meal was negatively correlated with protein recovery and zein purity (r = -0.66 and -0.72, respectively) (P < 0.02).