Corn Germ Protein Research Articles

Biobased lignin-blockers enable efficient production of glucose from lignocelluloses

Enzymatic hydrolysis of cellulose in lignocelluloses exhibits low efficiency due to low cellulose accessibility and adverse lignin effects. By using phenylsulfonic acid pretreatment to improve cellulose accessibility, we have developed several new plant proteins such as corn germ and green rapeseed proteins that extracted from inexpensive defatted meals as lignin-blockers. For pretreated lignocellulosic substrates with high cellulose accessibility, such plant proteins could effectively overcome negative lignin effects and achieve robust cellulose enzymatic conversion (88–97 %) at a low cellulase loading of 5 FPU/g glucan. To reach the same level of cellulose enzymatic conversion, adding corn germ protein could save cellulase loading by 3.6 times as compared to those without lignin-blockers. But these plant proteins showed insignificant promotion effects on substrates with low cellulose accessibility. Overall, this study coupled high cellulose-accessible substrates and efficient lignin-blockers to synergistically improve the profitability of lignocellulosic biorefinery.

Isolasi dan Pemurnian Protein dari Lembaga Jagung (Corn Germ) Menggunakan Metode Presipitasi dan Dialisis

The protein contained in corn germ can be used as a raw material that has the potential to provide many benefits in the food, pharmaceutical, and plastic industries. Corn germ with the highest content of protein is around 12-18.4%. In this study, protein from corn germ was isolated and homogenized using tris buffer HCl at pH 7.2. To obtain the protein fraction, precipitation was carried out (salting-out) using a solution of (NH4)2SO4 with saturation levels of 25%, 50%, and 70% respectively. The purification process was carried out by dialysis for 24 hours. The dialysis produced pure protein with a concentration of 4.161%. Based on the identification of functional groups using an FT-IR spectrophotometer, it was shown that the isolated and purified corn germ protein contained four absorption bands, including amide A (3211.48 cm-1 and 3226.91 cm-1), amide I (1633 cm-1 and 1629.85 cm-1), amide II (1527 cm-1 and 1552.70 cm-1) and amide III (1296.16 cm-1). The four absorption bands correspond to the wavenumbers of corn protein stated in the literature and are estimated to contain albumin, globulin, glutelin, and zein.

Fractionation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity

In Karimi, Azizi, and Ahmadi Gavlighi (2020), the word “Frationation” in the article title was incorrect, it should be “Fractionation” so it reads “Fractionation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity.” This has also been corrected in the online version. REFERENCE Karimi, A., Azizi, M. H., & Ahmadi Gavlighi, H. (2020). Fractionation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity. Food Science Nutrition, 8(5), 2395–2405. 10.1002/fsn3.1529

Frationation of hydrolysate from corn germ protein by ultrafiltration: In vitro antidiabetic and antioxidant activity.

In the present work, defatted corn germ was hydrolyzed by three proteases and further separated by sequential ultrafiltration with different molecular weight cutoff (100, 10, 2 kDa). Corn germ protein hydrolysate (CGPH) and their fractions were investigated for antioxidant activity, α‐glucosidase, α‐amylase, and DPP‐IV inhibitory activity. The degree of hydrolysis (DH) after 2 hr was 17.5%, 11.14%, and 2.05% for alcalase, trypsin, and flavourzyme, respectively. Trypsin hydrolysate showed the highest DPPH and ABTS+ radical scavenging and Fe2+ chelating activity, but a lower α‐glucosidase inhibitory activity. F1 fraction (<2 kDa) exhibited highest radical scavenging and α‐glucosidase inhibitory activity. While F2 fraction (2–10 kDa) showed the higher Fe2+ chelating and α‐amylase inhibitory activity, F1 fraction of flavourzyme showed the highest α‐glucosidase inhibitory and F2 fraction of alcalase and flavourzyme exhibited highest α‐amylase inhibitory activity. Hydrolysate and F1 fraction of alcalase and F2 fraction of trypsin showed the highest DPP‐IV inhibitory activity. RP‐HPLC results showed that trypsin hydrolysate had higher levels of high‐hydrophobic peptides. The amino acid composition of the F1 fractions showed high levels of hydrophobic amino acids. Thus, CGPHs may be used as a potential source of antioxidant and antidiabetic peptides in food industry and pharmaceutical application.

A new continuous system of enzymatic hydrolysis coupled with membrane separation for isolation of peptides with angiotensin I converting enzyme inhibitory capacity from defatted corn germ protein.

In this study, separation of peptides with Angiotensin I converting enzyme (ACE)-inhibitory capacity obtained from ultrasonically pretreated defatted corn germ protein (DCGP) by using a new continuous system of enzymatic hydrolysis coupled with membrane separation (EHC-MS) was investigated. Ultrasonic pretreatment was applied to enhance the enzymatic hydrolysis rate of DCGP, as proved in our previous study. The EHC-MS system was operated in two modes which included the batch system and continuous system with continuous water and substrate feeding and was compared with the EH-offline-MS system. The selection of the membrane was based on the hydrolysate fraction which had the highest activity for inhibition of ACE. The results showed that the 1-3 kDa fraction of DCGP hydrolysates had the lowest IC50 value (0.124 mg mL-1) for inhibition of ACE. The degree of conversion (%) of DCGP and output of peptides per unit of the enzyme were significantly (P < 0.05) increased by 55.3% and 55% in the EHC-MS batch process and 79% and 473% in the EHC-MS continuous operation compared to the EH-offline-MS system. The EHC-MS using continuous water and substrate feeding operation was noted to be the best in terms of a high degree of DCG protein conversion (75.68 ± 1.34) and the output of peptides per unit of the enzyme (78.65 ± 1.13). The results revealed that the EHC-MS method with constant water and substrate feeding could show a better application in peptide production in the food industry.

Effect of multi-frequency counter-current S type ultrasound pretreatment on the enzymatic hydrolysis of defatted corn germ protein: Kinetics and thermodynamics

Abstract In this paper, the impact of ultrasound pretreatment on the kinetics and thermodynamics of defatted corn germ protein (DCGP) enzymatic hydrolysis was evaluated. The enzymatic hydrolysis kinetics and thermodynamics were studied for traditional method and ultrasonic pretreatments with a single-frequency counter-current S type (20 KHz) (SFU) and a multi-frequency counter-current S type (20, 28, 35 and 40 KHz) (MFU). The results showed that the traditional, SFU and MFU pretreated enzymatic hydrolysis of DCGP followed the First-order kinetic model. Again, the SFU and MFU pretreatments enhanced the enzymatic hydrolysis of DCGP. Compared to traditional enzymatic hydrolysis, the reaction rate constant values were increased by 50.0%, 54.7%, 47.8% and 52.3% for SFU pretreated enzymatic hydrolysis, and 58.0%, 58.5, 53.6% and 54.7% for MFU pretreated enzymatic hydrolysis at 20, 30, 40 and 50 oC respectively. Also, the results showed that the SFU and MFU ultrasound pretreatments of DCGP reduced the thermodynamic parameters which included the activation energy (Ea), enthalpy (ΔH), entropies (ΔS) and Gibbs free energy (ΔG) in enzymatic hydrolysis reaction.

Effect of a multi-frequency counter-current S-type ultrasound pretreatment on the defatted corn germ protein: enzymatic hydrolysis, ACE inhibitory activity and structural characterization.

In this work, a defatted corn germ protein (DCGP) was pretreated with single frequency ultrasound at 20 kHz (SFU) and multi-frequency ultrasounds (20, 28, 35 and 40 kHz) (MFU). The microstructures, morphology, amino acid content, degree of hydrolysis, protein hydrolysate concentration and angiotensin-converting enzyme (ACE) inhibitory activity of the DCGP hydrolysate were analyzed. The results showed that both SFU and MFU pretreatments increased the ACE inhibitory activity of the DCGP hydrolysate more than that observed for the traditional method. Also, the SFU pretreatment showed the highest ACE inhibitory activity of 54% in comparison with that of the DCGP hydrolysates obtained via the traditional and MFU pretreatment methods. The results of ultraviolet-visible (UV-Vis) spectroscopy, fluorescence spectroscopy, surface hydrophobicity studies, Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM) confirmed the extent of the changes that occurred in the microstructures and morphology of DCGP pretreated with SFU and MFU. The results also indicated that the hydrophobic amino acid concentration was comparably higher in DCGP pretreated with SFU and MFU than that in the DCG protein isolated via the traditional method.

Factors influencing gelation properties of corn germ proteins.

As a by-product of the oil industry, corn germ meal is mainly applied as a high-protein ingredient in animal feeds, without any application of the specific functional properties of corn germ protein (CGP). Factors influencing the gelation properties of CGP in relation to its dynamic rheology are still unclear owing to limited information. CGP concentrate was recovered by the isoelectric precipitation method, and factors affecting its gelation properties were investigated using a rheometer. A weak gel formed at natural pH with 0.3 mol L-1 NaCl, and the minimum gel-forming concentration was observed at 150 g kg-1 . Higher CGP protein concentrations induced stiffer gels, and linear relationships were found between protein concentration and gel stiffness (G') as well as between protein concentration and gel viscosity (G″). Lower heating and cooling rate promoted the formation of stiffer gels. CGP gelation was both NaCl- and pH-dependent. Sodium tripolyphosphate significantly increased gel stiffness with increasing concentration. No difference in gel elasticity (tanδ) was observed with the inclusion of various concentrations of sodium tripolyphosphate or sodium polyphosphate. Heating and cooling rate, NaCl, protein concentration, pH and phosphates all impact the gel-forming ability of CGP concentrate. Desired gel properties can be obtained through adjustment of these factors. © 2017 Society of Chemical Industry.

Impact of Dry-milled Germ Processing on Aqueous Protein and Oil Extraction

Reduced petroleum cost and public objection to using corn for bioenergy rather than food have challenged grain ethanol producers to come up with new bioprocess and coproducts that can add value but maintain ethanol cost competitiveness. Novel dry and wet milling fractionation processes of corn that could generate higher value coproducts and improve coproduct economics, long-term outlook, and economic stability of corn processing plants have been being recently proposed. Germ Wet Milling™ is such novel aqueous processing method designed to increase germ protein and oil concentration by water soaking and wet fractionation of dry-milled corn germ. The goal of this study was to investigate the sequential oil and protein extraction after Germ Wet Milling and to develop economically viable processes for producing protein concentrates. Corn protein concentrates were prepared after aqueous processing of dry-milled germ using membrane filtration or isoelectric precipitation. The amount of protein recovered was a function of the protein dispersibility index of the starting material, which depended on soak temperature and time. Extracts prepared after Germ Wet Milling™ contained 59.1 to 64.7 % protein (db), while concentrates had 64.9 to 82.4 % protein. The technique used for protein recovery also influenced the mass and protein yield and composition. For all treatments, membrane filtration was a more effective method than isoelectric precipitation for recovering protein from extract. Aqueous enzymatic oil extraction (AEOE) was used to evaluate the oil recovery potential after Germ Wet Milling. The effect of enzyme dosages and/or elimination of the acidic protease on oil extraction from high protein, high protein dispersibility index (PDI) corn germ and high protein, low PDI corn germ were evaluated. AEOE using a combination of cellulases and xylanase (Optimash XL®), an acidic protease (Fermgen®), and a basic protease (Optimase®) resulted in oil recoveries as high as 71.9 % of the initial oil content. A twofold reduction in enzyme dosages was possible with little or no effect on oil recoveries for both types of germ.

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

AbstractThis 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.

Evaluation of corn germ protein as an extender in plywood adhesive

This study was conducted to evaluate the potential of wet-milled corn germ protein as an extender in plywood adhesive. Partially defatted dried corn germ from wet-milling, containing 2.1% (dry basis, db) crude oil and 24.7% (db) crude protein, was ground to 40-mesh particle size to produce the meal. The predominant water- and saline-soluble proteins were extracted from the corn germ meal (CGM) by using 0.1 M NaCl as solvent in a method that used homogenization, centrifugation, dialysis, and freeze-drying. The recovered freeze-dried protein extract (FDPE) was substituted (on protein content basis) for wheat flour in the standard adhesive mix for sprayline coaters. Adhesive containing CGM was also prepared in the same manner. Mixing and adhesion properties of the corn germ-based adhesives were compared with those of the industry standard adhesive. The adhesive containing FDPE showed dispersibility and mixing behaviors, as well as viscosity values that were almost identical to those of the industry standard and superior to those of CGM adhesive. The mean wet tensile strength of the adhesive containing FDPE was notably greater (1.71 MPa) than that of CGM-based adhesive (1.34 MPa) and wheat-based standard adhesive (1.38 MPa), which indicated stronger bonding. The results demonstrated that corn germ protein has the potential to be an alternative protein extender in plywood adhesives for sprayline coaters.

In growing pigs, the true ileal and total tract digestibility of acid hydrolyzed ether extract in extracted corn oil is greater than in intact sources of corn oil or soybean oil1

An experiment was conducted to determine the true ileal digestibility (TID) and the true total tract digestibility (TTTD) of acid-hydrolyzed ether extract (AEE) in extracted corn oil, high-oil corn, distillers dried grains with solubles (DDGS), corn germ, and high protein distillers dried grains (HP DDG) and to compare these values to the TID and TTTD of AEE in full-fat soybeans. Nineteen barrows with an initial BW of 52.2 kg (SD = 3.8) were fitted with a T-cannula in the distal ileum and allotted to a 19 × 11 Youden square design with 19 diets and 11 periods. A basal diet based on cornstarch, casein, sucrose, and corn bran was formulated. Eighteen additional diets were formulated by adding 3 levels of extracted corn oil, high-oil corn, DDGS, corn germ, HP DDG, or full-fat soybeans to the basal diet. The apparent ileal and the apparent total tract digestibility of AEE were calculated for each diet. The endogenous flow of AEE associated with each ingredient and values for TID and TTTD were calculated using the regression procedure. Results indicated that digested AEE in ileal digesta and feces linearly increased as AEE intake increased regardless of ingredient (P < 0.001) and the regression of ileal and fecal AEE output against AEE intake was significant for all ingredients (P < 0.001; r(2) > 0.77). However, the ileal and fecal endogenous losses of AEE were different (P < 0.05) from 0 only for extracted corn oil, HP DDG, and full-fat soybeans. The TID of AEE was greater (P < 0.05) for extracted corn oil (95.4%) than for all other ingredients. The TID of AEE in HP DDG (76.5%) was not different from the TID of AEE in full-fat soybeans (85.2%) but greater (P < 0.05) than high-oil corn, DDGS, and corn germ (53.0, 62.1, and 50.1%, respectively). The TTTD of AEE was greater (P < 0.05) for extracted corn oil (94.3%) than for all other ingredients, and the TTTD in full-fat soybeans (79.7%) was greater (P < 0.05) than the TTTD of AEE in high-oil corn, DDGS, corn germ, and HP DDG (41.4, 51.9, 43.9, and 70.2%, respectively). The TTTD of AEE in HP DDG was also greater (P < 0.05) than in high-oil corn, DDGS, and corn germ. In conclusion, the intact sources of oil originating from high-oil corn, DDGS, corn germ, or HP DDG are much less digestible than extracted corn oil, and with the exception of HP DDG, these sources of corn oil are also less digestible than the intact oil in full fat soybeans.

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

AbstractThis 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.

Effect of the Extent of Enzymatic Hydrolysis on Foaming and Emulsifying Properties of Corn Germ Protein Hydrolysates

The effect of the extent of the enzymatically modified corn germ protein isolates on foaming and emulsifying properties was investigated. The experimental results indicated that enzymatic treatment improved the FC and EA of corn germ protein isolates, but the ESI and FS were decreased. The EA and FC of samples were increased with DH improvement at low DH (&lt;10.4%), and the ESI and FS were decreased when DH was enhanced. The extent of modification should be determined by the intended application of new food ingredient.

Nutritive Value and Functional Properties of Corn Germ Protein Hydrolysates

The nutritional value and functional properties of corn germ protein hydrolysates was investigated. The amino acid profile of hydrolysates showed that there was an increase in the content of essential amino acids, His, Arg, Ile, Val and a decrease in Lys, Phe, Met when compared with the starting material. The low degree of hydrolysis (5.9%, 10.4%) improved the solubility at acid pH, WHC, OHC of corn germ protein isolates, but samples of high degree of hydrolysis (14.1%) was not significantly increased in WHC and OHC.

Aroma Characteristics of Corn Germ Protein Flours

ABSTRACTEight sensory attributes were established to differentiate aroma characteristics among four kinds of corn germ protein flours (CGPF) processed by treatments to improve flavor quality. The projections of sample and conceptual spaces on a two‐dimensional scale reflected aroma differences among samples evaluated by panelists. Volatiles of samples were separated by gas chromatography, and peaks that elicited olfactory responses were recorded as instrumental data. The projections of sample and volatile compound spaces reflected changes of volatiles by treatments. Relationships between sensory and instrumental data were elucidated by superimposing the two spatial maps. In general, treated CGPF samples had less grainy, brown, corn‐like and sweet notes than untreated CGPF samples. However, there were more green, musty and chemical notes in the treated CGPF samples.

Foaming Properties of Selected Plant and Animal Proteins

ABSTRACTThe foaming properties of proteins are important in predicting their fnnctionality in aerated foods. In model aqueous systems, foam expansion (FE) and foam stability (FS) of commercial plant proteins, wheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF), were compared with those of nonfat dried milk (NFDM) and egg white powder (EWP) at 1, 2, 4, 6, and 8% using one‐ and two‐way analyses of variance. The effects of pH 4, 5, 6, 7, and 8 on FE and FS of WGPF were also measured. The highest overall FE and FS were obtained for EWP. Among plant proteins, FE and FS were maximum for CGPF and SF, respectively. FS was lowest for NFDM. Except for SF, FE and FS increased with increasing protein concentration. The FE and FS of WGPF were highest at pH 8, lowest at pH 7, and intermediate at pH 4–6.

Wheat Germ Protein Flour Solubility and Water Retention

ABSTRACTThe effects of pH and temperature on water retention (WR), protein solubility (PS), and total solubility (TS) of defatted wheat germ protein flour (WGPF) were studied in a model system. PS of WGPF was compared with those of corn germ protein flour (CGPF), soy flour (SF), nonfat dried milk (NFDM), and egg white powder (EWP) at 1–8%. WR increased with increase in pH from 4 to 8. Maximum WR occurred at 70°C, and slight variations were observed between 5 and 30°C. PS and TS increased with increases in pH and temperature. PS of proteins was in the order of NFDM &gt; EWP &gt; SF &gt; CGPF=WGPF. The results showed the potential for usage of WGPF in comminuted meats, beef patties, breads, cakes, and cookies.

Functionality of Wheat Germ Protein in Comminuted Meat Products as Compared with Corn Germ and Soy Proteins

ABSTRACTWheat germ protein flour (WGPF), corn germ protein flour (CGPF), and soy flour (SF) were used as additives at a level of 3.5% in comminuted meat products (CMP). Frankfurters with protein additives showed increased water‐holding capacity and batter stability and decreased cooking loss. Improved viscosity and adhesiveness were observed with protein additives when the level of added water was constant. Protein additives also influenced textural and sensory properties of frankfurters. WGPF at a level of 3.5% was found similar to effects of SF and CGPF. WGPF is a potential nonmeat protein additive that can be utilized as an extender in CMP such as frankfurters and bologna.

COMPARATIVE STUDY OF SHELF-LIFE OF FRANKFURTERS CONTAINING PLANT PROTEIN ADDITIVES

Soy flour (SF), soy concentrate (SC), soy isolate (SI) and corn germ protein flour (CGPF) were incorporated in frankfurters. The sensory analysis, chemical, and microbiological tests were conducted to investigate the effect of plant proteins on stability during vacuum-packaged storage. No significant difference in meaty aroma was found between all samples after 45 days storage. Atypical flavor and aroma of all samples, including the all-meat control increased (P < 0.05) after 45 days storage. A tendency was found of increase in atypical aroma and flavor with increase in total volatile nitrogen values and total psychrophiles during storage. Salty flavor increased with storage time in experimental samples, but juiciness decreased. Samples containing SF and SC had higher total volatile nitrogen than SI and CGPF containing samples at 2, 30 and 45 days of storage. No significant differences were found in TBA values between tested samples, except higher TBA values for SI containing samples. There was no significant difference among samples in total psychrophilic counts.