Characterization of protein extracted from flaked,defatted, whole corn by the sequential extraction process

An investigation was conducted to identify and characterize protein extracted by 45% ethanol:55% 0.1 M NaOH from flaked, defatted, undegermed corn (Zea mays L.) during Sequential Extraction Processing (SEP). This new approach to corn milling, SEP, recycles the ethanol produced from the fermentation of cornstarch to upstream steps of protein extraction and the simultaneous extraction of corn oil and dehydration of the ethanol. About 10% of the protein was extracted by ethanol during counter-current-percolation oil extraction. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and amino acid analysis identified this protein as zein. Nearly 65% of the total protein was recovered by the process in the protein extraction step from soft dent corn (Pioneer 3377), medium-hard dent corn (Pioneer 3732) and high-lysine corn. The freeze-dried solids of the ethanol/alkali extracts from these corn hybrids contained about 80% crude protein (db). The amino acids were present in quantities similar to those in whole corn and markedly higher than those in corn gluten meal. These results indicate that SEP produces high-quality protein suitable for food and industrial uses. Paper presented at the Symposium on Oilseed Processing for Edible Food and Feed Products, 82nd Annual Meeting of the AOCS, May 12–15, 1991. Research Associate, Assistant Professor, and Professor, respectively.     

Functional properties of soybean and lupin protein concentrates produced by ultrafiltration-diafiltration

Ultrafiltration followed by diafiltration (UF-DF) was evaluated for the production of protein products from partially defatted soybean meal or undefatted lupin (Lupinus albus L.2043N) meal. This study determined the effects of UF-DF on functional properties of the extracted proteins and compared the results with those of protein prepared by acid-precipitation (AP). UF-DF produced only protein concentrates (73% crude protein, dry basis, db), while AP produced protein isolates (about 90% crude protein, db). Soybean protein produced by UF-DF showed markedly higher values for solubilities up to pH 7.0, surface hydrophobicity index, emulsion activity index, and foaming capacity than did the AP soybean protein. UF-DF soy protein was also the most heat-stable among all protein samples tested. With lupin proteins, only the surface hydrophobicity and emulsion activity indices were significantly improved by using UF-DF. UF-DF generally had no adverse effects on, and in most cases even improved, the functional properties of soy protein concentrate produced by this method. UF-DF did not produce a comparable improvement in functional properties of lupin proteins as it did for soybean protein.     

Sojaproteinpräparate als Antispritzmittel für Margarine

Soy Protein Preparations as Antispattering Agents for Margarine It was found that soy protein concentrates obtained by successive extraction of ground soybeans with hexane and ethanol or with hexane alone, grinding to a particle size less than 100 μ and subsequent leaching with diluted acids at pH 4.5, are good antispattering agents. If the process is preceded by a debittering treatment of the beans with steam, products having very neutral taste are obtained. Addition of 0.2% of these concentrates to fully deaerated margarine containing 5% milk and 0.15% each of mono- plus diglycerides and lecithin, prevents spattering completely. Half-fat margarine does not spatter inspite of its high water content, if 0.1% of the concentrate is added. A disadvantage is the infection of soy protein concentrates with resistent fungus, which necessitates sterilization of the proteins at 85% C in acidic medium.     

Protein concentrate of African oil palm (Elaesis guineensis, Jacquin), extraction process and functional properties

A study was carried out for the purpose of obtaining and characterizing a protein concentrate obtained from defatted oil palm cake using alkaline extraction, and compare it with a commercial soy meal. The oil palm cake came from a national industry as a subproduct of the oil extraction of the palm kernels. The moisture, protein, fat, crude fiber and ash content of the oil palm was then determined. The optimum conditions for extraction and precipitation of the proteins were selected. These were the following: extraction at pH, 11.4; adding NaOH 0.06 M solvent; a meal/solvent relation of 1:20 g/ml and extraction time, 20 minutes with magnetic agitation, and precipitation at pH 5.3. The protein concentrate obtained contained: 66.50% protein; 0.07% fat, 0.90% crude fiber, and 3.20% ashes. Then the following functional properties were analyzed: solubility, according to the pH; water absorption (250); oil absorption (175); emulsion activity (27.2), and stability (13.6). The author concludes that the protein concentrate has good water and oil absorption when compared to soymeal; the emulsion, however, was found to be unstable to heat.     

Influence of pH and salt concentration on protein solubility,emulsifying and foaming properties of sesame protein concentrate

The effects of pH and NaCl concentration on protein solubility, emulsification, and foamability of sesame protein concentrate from dehulled seeds were investigated. The protein content of the concentrate was 70.7%. Protein solubility, emulsion, and foaming capacities varied with pH and ionic strength. Protein solubility, which was least at pH 4, (2.1%) ranged from 6.6% at pH 2 to 13.1% at pH 10. The solubility increased with increase in ionic strength, ranging from 9.8% at 0.0 M to 16.1% at 1.0 M concentration. The emulsion capacity ranged from 6.2 mL oil/g sample at pH 2 to 19.4 mL oil/g sample at pH 10. The emulsion capacity increased from 11.5 mL oil/g sample at 0.0 M to 20.9 mL oil/g sample at 1.0 M salt concentration. Stability of the emulsion increased with increase in NaCl concentration, ranging from 42% at 0.0 M concentration to 70% at 1.0 M concentration, but 0.5 M NaCl produced the most stable foam after 120 min of whipping while the least stable was at 1.0 M.     

Factors affecting oil extraction/water adsorption in sequential extraction processing of corn

The sequential extraction process (SEP) uses ethanol to extract oil and protein from cracked, flaked, and dried corn, and the dried corn simultaneously dehydrates the ethanol. Value-added co-products are possible, potentially making production of fuel ethanol more economical. The effects of solvent-to-corn (S/C) ratio, corn moisture content (MC), and number of extraction stages on ethanol drying, oil recovery, and protein loss during the simultaneous oil extraction/water adsorption step of SEP were evaluated. Extractions were carried out by using both aqueous ethanol and ethanol/hexane blends at 56°C. The S/C ratios tested were 3∶1, 2∶1 (control), 1.5∶1, and 1∶1 (w/w). More anhydrous ethanol, greater oil yields, and less co-extracted protein were obtained with higher S/C ratios. Less anhydrous ethanol and lower moisture adsorption capacities were obtained when the corn MC was ≥1.12%. Oil yields gradually decreased with drier corn, whereas protein loss increased when corn MC was <1.12%. Reducing the number of extraction stages from seven (original SEP) to five did not affect ethanol drying capability, oil yields, and protein co-extracted with oil. Using ethanol/hexane blends resulted in more anhydrous ethanol, higher oil yields, and less protein co-extracted with oil.     

Functional properties of hydrothermally cooked soy protein products

The effects of hydrothermal cooking on the functional properties of defatted soy flour, aqueous alcohol washed soy protein concentrate, and soy protein isolate were determined in samples that were treated at 154°C by infusing steam under pressure for 11, 19, 30, and 42 s, and then spray dried. Hydrothermal cooking increased the nitrogen solubility index (NSI) of the concentrate from 15 to 56% and altered the solubility profile from a flat profile to one more typical of native soy protein. Hydrothermal cooking also improved foaming and emulsifying properties of the concentrate. For isolate, hydrothermal cooking also improved NSI and foaming and emulsifying properties, although the improvements were less dramatic than with concentrate. NSI and emulsifying properties of the flour were improved by some processing conditions, but foaming properties were not improved by hydrothermal cooking. Dramatically increased protein solubility of concentrate and modestly improved protein solubilities of flour and isolate by hydrothermal cooking, which will also inactivate trypsin inhibitors and microorganisms, have considerable practical significance to protein ingredient manufacturers and those who use these ingredients in foods and industrial products.     

Improved Solubility and Emulsification of Wet-Milled Corn Germ Protein Recovered by Ultrafiltration–Diafiltration

This study evaluated Ultrafiltration–Diafiltration (UFDF) as a means to improve the extractability of wet-milled corn germ protein and determined its effects on the functional properties of the recovered protein product. Wet germ and dried germ proteins were extracted by using 0.1 M NaCl at 50 °C. Major steps in the method were stirring, centrifugation, UFDF and freeze-drying. For dried germ, the UFDF method showed marginal increase in protein extraction efficiency, while that of wet germ remained similar to what we observed for the baseline method (saline extraction with dialysis instead of UFDF). UFDF protein extracts from both germ samples were significantly more soluble than extracts recovered by the baseline method and showed atypical solubility profiles; i.e., the amount of soluble protein was essentially unchanged under acidic, neutral, and alkaline pH. UFDF-dried germ protein was markedly more soluble than UFDF-wet germ protein (80 vs 50 % soluble protein, respectively) between pH 2 and pH 10. Both of these UFDF-germ proteins also had emulsifying capacities and water-holding capacities that were superior to those of proteins extracted by the baseline method, but this favorable effect by UFDF was not observed for emulsion stability, foaming properties, and heat stability.     

Effect of equilibrium oil extraction on the chemical composition and sensory quality of soy flour and concentrates

Previous studies have shown that ambient-temperature equilibrium, hexane extraction of soy flour yielded the same amount of oil as was extracted from soy flakes by conventional high-temperature processing. The oil obtained at ambient temperatures contained less phospholipid than commercial crude oils obtained by traditional processing. In this study, chemical composition, flavor and odor of soy flour obtained after oil extraction by the equilibrium procedure were evaluated before and after toasting. Results were compared with those obtained for commercial untoasted food-grade soy flakes. Chemical and sensory analyses were performed on soy protein concentrates (SPC) prepared from defatted flour, defatted toasted flour and commercial defatted white food-grade flakes. SPC were made by acid and ethanol-extraction methods. Ethanol extraction of soy flour produced SPC with similar protein, lipid and sensory qualities to those obtained from commercial flakes. Acid extraction produced SPC with more lipid than was obtained by ethanol extraction. Toasted soy flour and flakes had similar sensory properties, as did the SPC prepared from them.     

Extraction,Composition and Functional Properties of Pennycress (Thlaspi arvense L.) Press Cake Protein

This study compared two methods for extracting the protein in pennycress (Thlaspi arvense L.) press cake and determined the composition and functional properties of the protein products. Proteins in pennycress press cake were extracted by using the conventional alkali‐solubilization–acid‐precipitation (AP) method or saline‐based (SE) procedure (0.1 M NaCl at 50 °C). The extraction method has a major influence on the purity and functional properties of press cake protein products. AP had a lower protein yield (23 %) but much higher purity (90 % crude protein) compared with SE (45 % yield, 67 % crude protein). AP protein isolate had high foam capacity (120 ml), high foam stability (96 % foam volume retention) and high emulsion stability (24–35 min), and it was resistant to heat denaturation (3 % loss of solubility at pH 2 and pH 10). On the other hand, SE protein concentrate showed remarkably high solubility (>76 %) between pH 2 and 10 and exceptional emulsifying activity (226–412 m²/g protein), but was more susceptible to heat denaturation at pH 7 and pH 10 (65–78 % loss of solubility). These results strongly demonstrate that higher purity pennycress press cake protein can be produced by either saline extraction or acid precipitation and have functional properties that are desirable for non‐food uses.     

共轭亚油酸粉末化微胶囊的制备

研究了喷雾干燥法制备共轭亚油酸微胶囊的工艺参数及配比条件。结果表明,最佳的工艺参数及配比条件为:乳液80℃热处理60 m in,乳化剂蔗糖酯加入量为水液的1%~1.5%,大豆分离蛋白与麦芽糊精质量比为1∶4,壁材中玉米糖浆含量38.5%,固形物含量16.7%,共轭亚油酸理论含量16%左右,进风温度130~150℃,进料流量(2.5~3.5)×150 mL/h,进料温度35℃,进风流量1.1 m3/m in左右,喷嘴压力180 kPa。制备出的共轭亚油酸微胶囊有较好的产品质量。     

Soy protein biopolymers cross-linked with glutaraldehyde

Biopolymers from soy protein isolate (SPI) crosslinked with glutaraldehyde (GA) were prepared. Surface hydrophobicities of SPI-GA biopolymers and SPI were 4.4 and 11.5, respectively. The solubility profile of SPI was slightly higher than that of SPI-GA biopolymers. Foaming capacities of SPI-GA biopolymers (23 mL) were higher than that of SPI (19 mL), but similar to egg white (22 mL). Foaming stabilities of SPI-GA biopolymers (120 min) were significantly higher than those of SPI (40 min) and egg white (98 min). The emulsifying properties of SPI-GA biopolymers were lower than those of SPI and bovine serum albumin (P>0.05). Tensile strength (TS) and elongation at break (ETB) of SPI-GA biopolymer films were significantly higher than those of glycerol-plasticized soy protein films. TS and ETB of SPI-GA biopolymer films increased with increasing GA concentrations. GA treatment intensified yellowness of SPI-GA biopolymer films. SPI-GA biopolymers may have potential use for biodegradable packaging materials.     

Interaction of soy isolate with polysaccharide and its effect on film properties

When soy isolate was mixed with sodium alginate, the two polymers interacted to form electrostatic complexes. They also formed varying degrees of covalent bonding, depending on reaction time and the presence or absence of the reducing agent sodium cyanoborohydride. On the other hand, soy isolate and propyleneglycol alginate (PGA) formed mostly covalent complexes at alkaline pH. The interaction of soy protein with polysaccharide maintained or improved its solubility and emulsifying activity, particularly when covalent bonds were involved. The alkylated complexes also showed better film-making properties. However, protein-PGA films were more readily formed and had greater stability in water than the protein-alginate films.     

Enzymatic modification of soy protein concentrates by fungal and bacterial proteases

Solubility, foaming capacity and foam stability of denatured soy protein concentrate obtained from toasted flour were improved by proteolysis with fungal or bacterial proteases. Emulsifying capacity was unchanged, but emulsion stability decreased; bacterial protease highly improved oil absorption. Also, the bacterial protease was able to solubilize more protein and gave products which foamed more than those obtained with the fungal enzyme. However, the stabilizing properties of the bacterial modified soy protein concentrate at the air/water or oil/water interface were inferior. By limited hydrolysis up to degree of hydrolysis 10% most functional properties were improved without greatly reducing emulsion stability and water absorption.     

Protein solubility characteristics of commercial soy protein products

Solubility characteristics of commerical soy protein products (flours, concentrates, and isolates) were determined under various conditions. From the solubility profiles at various pH values and NaCl concentrations, soy protein isolates can be divided into three groups. One group had high solubility near the pl. Another group had low solubility near the pl, but high solubility at pH 11. The third group had low solubility even at pH 11. Except for the hydrolyzed products, the protein solubilities of the soy protein products at various salt concentrations were very low. Temperature did not significantly affect the protein solubility, although a few products showed more than a 20% increase at temperatures >50°C. Soy protein concentrates and soy protein isolates showed similar solubility profiles. The proteins in all commercial products (except flours) tested were denatured, as evident from the solubility profiles in the presence of salt and the enthalpy values from DSC.     

Effects of Extraction Temperature and Preservation Method on Functionality of Soy Protein

The effects of extraction temperature and preservation method on the functional properties of soy protein isolate (SPI) were determined. Four extraction temperatures (25, 40, 60, and 80 °C) were used to produce SPI and yields of solids and protein contents were determined. Three preservation methods were also tested (spray-drying, freeze-drying, and freezing–thawing) and compared to fresh (undried) samples for each extraction temperature. No differences in yields of solids and protein were observed among SPIs extracted at 25, 40, and 60 °C; however, SPI extracted at 80 °C yielded significantly less solids and protein. Extraction temperature significantly affected SPI functionality. As extraction temperature increased, solubility and emulsification capacity decreased; surface hydrophobicities, emulsification activities and stabilities, and dynamic viscosities increased; and foaming properties improved. Preservation method also significantly affected SPI functionality. Drying method did not affect the denaturation enthalpies of SPIs, but spray-dried SPIs had higher solubilities, surface hydrophobicities, and emulsification stabilities, and lower viscosities, emulsification activities and rates of foaming than freeze-dried SPI exhibited. Emulsification and foaming capacities and foaming stabilities were similar for both methods of drying. There was significant interaction between extraction temperature and preservation method for all functional properties except emulsification capacity.     

Fate of Phytic Acid in Producing Soy Protein Ingredients

Phytic acid (myo-inositol hexaphosphate) is present in soybeans and soy protein products at 1–2% dry matter. Phytate causes poor absorption of essential electrolytes and minerals, and binds to proteins and co-precipitates with isoelectric soy protein isolates. We determined how phytic acid partitioned during different procedures to prepare soy protein ingredients. Procedure and soybean variety significantly affected phytic acid content and recovery. High-sucrose/low-stachyose (HS/LS) soybeans contained significantly (P < 0.05) less phytate than did a typical variety of commodity soybeans (IA2020). In addition, phytate was more readily extracted from the commodity soybeans than from HS/LS soybeans. Among all procedures studied, ethanol-washed soy protein concentrate had the highest phytate contents and yields in the protein products for both soybean varieties (~80 mg/g and 99%, respectively). When protein extraction was carried out at room temperature the protein products had significantly lower phytate yields (60–78%) than when extraction was at 60 °C (80–99%). The protein products obtained from normal soybeans had significantly higher phytate contents than the same products made from HS/LS soybeans. When fractionating soy proteins, the glycinin-rich fraction contained significantly less phytate than the β-conglycinin fraction except for the fractionation procedure performed at room temperature instead of 4 °C.     

Functional properties and protein concentrate of Pigeon pea (Cajanus cajan (I.) Millsp) flour

The objective of this investigation was to study the functional properties of Pigeon pea (Cajanus cajan (L.) Millsp) flour and protein concentrate. The solubility of both samples were superior than 70% at pH above 6.7 and below 3.5. The water and oil absorption were 1.2 and 1.07 ml/g of sample and 0.87 and 1.73 ml/g of flour and protein concentrate samples, respectively. The minimum concentration of flour and protein concentrate needed for gelation was 20% and 12%, respectively. The emulsifying capacity of flour and concentrate was 129.35 g and 191.66 g oil/g of protein and the emulsion stability 87.50 and 97.97%, respectively, after 780 minutes. The foam capacity and stability of flour foam were 36.0% and 18.61, while of the concentrate were 44.70% and 78.97% after 90 minutes. These properties indicate that the flour as well as the concentrate could have application in various food systems.     

Effect of canola meal fermentation and protein extraction method on the functional properties of resulting protein products

The present study investigated the effect of solid-state fermentation (SSF) of cold-pressed (CP) and hexane-extracted (HE) canola meals with Aspergillus niger NRRL 334 and Aspergillus oryzae NRRL 5590 on the functionalities of protein products extracted from them. After SSF, proteins were recovered using alkaline extraction-isoelectric precipitation (AE-IP) or salt extraction-dialysis (SE). SSF of the two meal types reduced the protein content of the extracts produced by AE-IP. There were varied effects to solubility, foaming, and emulsifying properties as a result of SSF under the combined influence of functionality pH, strain, meal type, and protein extraction method. The protein isolate produced from CP meal using SE had increased solubility at pH 7 (from 51.8% to 90.7%) when the meal was fermented with A. oryzae. Both strains resulted in an over twofold increase in the emulsifying activity index (at pH 7) of AE-IP products from CP meal. For both protein extraction methods, the protein products from A. niger fermented HE meal had better foaming capacity (FC) at pH 7 than the controls (non-fermented), but reduced FC at pH 3. Overall, regardless of meal fermentation, the SE products were richer in protein and had higher oil holding capacity (OHC), whereas the water holding capacity (WHC) was higher for AE-IP isolates. SSF of the meals generally improved the O/WHC of the extracted proteins. The findings suggest that canola protein functionality could be effectively modulated by SSF with different microbial strains under various processing conditions to enhance their applicability in the food industry.     

Lupin protein concentrates by extraction with aqueous alcohols

In order to remove the toxic quinolizidine alkaloids and other nonprotein constituents, hexane-defatted flakes of lupin (Lupinus mutabilis) were extracted under various conditions with ethanol, methanol or their aqueous solutions. Lupin protein concentrates containing more than 70% protein and 0.1–0.2% alkaloids were obtained in high yields by consecutive extractions, countercurrent extraction or semicountercurrent extraction of the defatted lupin flakes with either 80% ethanol or 80% methanol.