Nitrogen extractability and buffer capacity of defatted linseed (Linum usitatissimum L.) flour

Defatted linseed flour was prepared from cold-pressed seed meal via hexane extraction of the residual oil, followed by removal of the major portion of the hulls through grinding and sieving (sieve size 0.25 mm). The resulting flour had 50% protein on a dry basis compared with 40% contained by the whole seed on an oil-free dry basis. Nitrogen extractability of the defatted flour in water was not influenced by the length of the extraction period but an increased extraction was observed at higher solid:liquid ratios up to the studied limit of 1:40. The smallest amount of nitrogen (20%) was extracted in the pH range 4.0–4.6 and the greatest (80%) at pH 12.0. Addition of NaCl (0.1–1.0 M) broadened the pH range of minimum nitrogen extractability and shifted it towards lower pH region. At higher concentrations (0.6 and 1.0 M) NaCl markedly increased nitrogen extractability in the pH range of 4.0 to 8.0. Precipitation of protein from an extract at pH 10.0 was maximum (77%) at pH 4.1. A higher buffer capacity of the flour was observed in the acidic medium (0.204 mmol HCl g^?1 flour) than in the alkaline medium (0.096 mmol NaOH g^?1 flour).     

Fate of Pigments and Phytate During Isolation of Protein from Defatted Glandless Cottonseed Flour

In sequentially extracting proteins from defatted glandless cottonseed flour with water, salt (5% NaCl) and alkali (0.2% NaOH) solutions, high concentrations of yellow pigments resulted in watersoluble isolate (WSI), while much of the dark-brown pigments and phosphorus were found in alkali-soluble isolate (ASI) and small amounts of pigments in salt-soluble isolate (SSI). The major protein fractions of WSI and SSI contained small amounts of sugar and pigments and no phosphorus, while that of ASI contained high levels of bound sugar, dark-brown pigments and phosphorus. Yellow pigments were preferentially bound to small molecular weight proteins, but dark-brown pigments were bound to large protein molecules.     

Effect of Extraction Conditions on the Extractability of Winged Bean (Psophocarpus tetragonolobus (L) DC) Proteins

Protein extractability from defatted winged bean flour was studied under various conditions of pH (2, 4, 6, 8, 10, 12), temperature (15°, 30°, 45°C) and time (10, 20, 30 min). Results indicated that protein extractability was strongly pH dependent. Maximum protein extract-ability was attained at pH 12 while the minimum extractability occurred at pH 4. Protein extractability was not significantly affected at the various temperature and time combinations; however, when extraction time was extended (at 15 min increments) from 30 min to 120 min, significantly higher (15%) protein was extracted at 30°C after an additional 60 min. Increased solvent-to-flour ratios resulted in increased protein extractability, but increased salt (NaCl and CaCl₂) concentrations (1M) decreased extractability.     

Influence of pH Shift on Functional Properties of Protein Isolated of Tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) Muscles and of Soy Protein Isolate

The physicofunctional and chemical properties of acid-aided protein isolate (AcPi), alkaline-aided protein isolate (AlPi) and soy protein isolate (SPI) prepared from tilapia muscle and defatted soy flour as a function of pH and/or NaCl concentration were investigated. Both acid- and alkali-aided processes lead to significant recoveries (P < 0.05) of proteins with substantial reduction of lipids in AlPi (0.81%) and AcPi (0.96%), the lowest for SPI (0.336%) facilitated by the processing method and sample used. There is greater lipid reduction at alkali pH, effective removal of impurities such as bones and scales, indicated by percentage ash (AcPi, 4.53%; AlPi, 3.75% and SPI, 3.51%). No major difference noted in sodium dodecyl sulphate polyacrylamide gel electrophoresis protein bands (14.4–97.4 kDa) possibly representing partial hydrolysis of myosin. Solubility was the highest at pH 3.0 and 11.0 and the lowest at isoelectric point with foam capacity showing similarity at varying pH. The addition of NaCl improved foam stability, possibly due to the increased solubility and surface activity of the soluble protein. On the whole, AcPi, AlPi and SPI manifested lower solubility and foamability at pH 4.0 and 5.0. AlPi exhibited appreciable levels of solubility, emulsion capacity, oil-holding capacity, viscosity and whiteness, whereas SPI had appreciable water-holding capacity. AcPi, AlPi and SPI have excellent relevance for product development based on their functionality.     

Nitrogen extractability and functional properties of defatted Erythrina variegata flour

Defatted Erythrina variegata flour was prepared from dehusked seed meal by hexane extraction of residual oil. The resulting flour had 403 g kg⁻¹ of protein as compared to 282 g kg⁻¹ in the whole seed-defatted meal. Nitrogen extractability of the defatted flour in water was not much influenced by the length of extraction period above 40 min, but an increased extraction was observed at a higher liquid to solid ratio up to a studied limit of 1:60; the optimal ratio was found to be 1:30. The minimum of 26.9% nitrogen was extracted in the pH range 3.0–4.0 and maximum of 94.8% at pH 12. Addition of sodium chloride (0.1 or 0.5 M) broadened the pH range of minimum nitrogen extractability and shifted it toward a lower pH region. At both concentrations of sodium chloride, a marked increase in nitrogen extractability, in the pH range 3.0–7.0, was observed. Precipitation of protein from an extract of pH 10.0 was maximum (85.3%) at pH 4.75. A higher buffer capacity of the flour was observed in the acidic medium (0.195 mmol HCl g⁻¹ flour) than in alkaline medium (0.093 mmol NaOH g⁻¹). Water absorption and oil absorption values for the whole E. variegata seed flour and the dehusked, defatted flour were 1.81, 1.43 and 1.02, 1.52 kg kg⁻¹, respectively.     

The study of some properties of rapeseed protein with a view to protein concentrate production

Optimum conditions for extraction and precipitation of rapeseed proteins have been defined: 10% NaCl extracts 70% of the total nitrogen (N_t) of a laboratory defatted flour and 0.1 N -NaOH, 89% (but only 62% of the N_t of an industrial oil meal). The maximum precipitation of these proteins occurs at pH 3 (NaCl extract) and pH 6.5 (NaOH extract) with fairly low yields (22 and 51% of protein nitrogen, respectively). The explanation lies in the distinctive behaviour of two protein groups. The first one, composed of high molecular weight proteins, is readily precipitated by HCl; the second one, comprised of basic, low molecular weight proteins of excellent amino-acid composition, is precipitated with great difficulty (trichloroacetic acid). Furthermore, the low protein yields generally reported also originate in important differences in solubility between laboratory defatted flour and industrial meal proteins, probably due to the denaturing action of heat and moisture used in oil-processing.     

Changes of Molecular Forces During Thermo-Gelling of Protein Isolated from PSE-Like Chicken Breast by Various Isoelectric Solubilization/Precipitation Extraction Strategies

Changes in protein intermolecular interactions during thermo-gelling were measured to compare the gelation properties of isoelectric solubilization/precipitation (ISP)-isolated protein extracted (solubilized at 3.5 and 11.0, precipitated at 5.5 and 6.2) from pale, soft, and exudative (PSE)-like chicken breast meat with raw meat paste. The solubility of both in water and salt (0.6 M NaCl) decreased significantly after ISP treatments. Protein profile analysis revealed that precipitation pH showed little influence on protein profile. Under pH 3.5 and pH 11.0 solubility conditions, the recovered protein at pH 6.2 showed significantly higher gel hardness than that at pH 5.5, which can be induced by hydrophobic change. Surface hydrophobicity (SH₀) and hydrophobic interactions at 25 °C presented similar results, indicating that the soluble protein at pH 11.0 exhibited a higher value after precipitation at pH 6.2 than that at pH 5.5, and the hydrophobicity of pH 3.5 isolates was higher than that of the pH 11.0 groups. However, the maximum hydrophobicity upon heating was inconsistent with initial tendencies. Given that the hydrophobic residues were exposed sufficiently during the ISP process, the ISP-treated proteins, particularly the samples extracted at pH 3.5, might be less susceptible to heat-induced exposure. The gelation behavior of the ISP-treated proteins had been modified on the basis of the intermolecular bonds during heating. In conclusion, the precipitation condition demonstrated excellent relevance for product development based on functionality.     

Effects of Acylation of Defatted Cottonseed Flour with Various Acid Anhydrides on Protein Extractability and Functional Properties of Resulting Protein Isolates

Maleylation, succinylation, dimethylglutarylation, and sodium sulfite treatment of cottonseed flour increased protein extraction from the flour in suspension, and precipitated more protein in the extract at pH 4.0, compared to unmodified flour processed through conventional methods. However, acetylation decreased protein extraction and precipitation at this pH. Protein isolates from succinylated, maleylated and dimethylglutarylated flours were highly water-soluble, and did not coagulate by heating. Acetylation decreased heat coagulability of the resulting protein isolate, but did not affect water solubility of the isolate. Treatment of the flour with sodium sulfite markedly increased heat coagulability of the isolate, and decreased its solubility. Oil absorption capacity of the isolate was increased slightly by dimethylglutarylation, but other treatments did not affect the capacity significantly. Sensitivity of proteins in isolates to calcium ions was not affected by acylation or sodium sulfite treatment of the flour.     

Effect of stabilization of rice bran on the extractability and recovery of proteins

The extractability profile of rice bran proteins under different conditions were studied to determine optimal conditions of extraction. Milling and differential sieving of rice bran increased the protein content in fine fraction by 7%. Maximum extractability of protein from defatted rice bran at pH 11.0 was 72%, out of which 70% could be precipitated at isoelectric pH 4.0. Increasing the time of extraction or using sodium chloride, sodium dodecyl sulfate or sodium hexametaphosphate were not effective in extracting more protein. The extraction and precipitation profiles of proteins from acid stabilized rice bran were comparable to untreated rice bran. However, it was very low for heat stabilized and parboiled rice bran. Denaturation of protein due to heat treatment affected the extractability of protein. Protein contents of protein concentrates obtained from untreated rice bran and acid stabilized rice bran were in the range of 71–73% whereas protein concentrates from heat stabilized rice bran and parboiled rice bran had lower protein contents of 39.5 and 54.5%, respectively.     

Negative Roles of Salt in Gelation Properties of Fish Protein Isolate

ABSTRACT: Salt effect on gelling properties of fish protein isolate (FPI) prepared by acid‐ and alkali‐aided extraction was investigated. Acid‐ or alkali‐extracted FPI formed significantly better gel texture with 0% NaCl than with 3% NaCl. Texture properties of acid‐ or alkali‐extracted FPI decreased as NaCl content increased, especially at 2% to 3% salt. Contrarily, salt significantly promoted texture qualities of conventional surimi gels. The effect was highlighted when they were subjected to low temperature setting. The myofibrillar proteins in FPI were not solubilized when NaCl was added, perhaps due to protein aggregation caused by acid or alkali extraction. FPI solubility, however, was not closely related to their texture properties. Cold setting did not promote texture properties of FPI gels as much as conventional surimi gels. Acid‐extracted gels gave the best color properties.     

Solubility and functional properties of sesame seed proteins as influenced by pH and/or salt concentration

The protein content, solubility and functional properties of a total protein isolate prepared from sesame seeds (Kenana 1 cultivar) as a function of pH and/or NaCl concentration were investigated. The protein content of the seed was found to be 47.70%. The minimum protein solubility was at pH 5 and the maximum was at pH 3. The emulsifying capacity, activity and emulsion stability as well as foaming capacity and foam stability were greatly affected by pH levels and salt concentrations. Lower values were observed at acidic pH and high salt concentration. The protein isolate was highly viscous and dispersable at pH 9 with water holding capacity of 2.10 ml H₂O/g protein, oil holding capacity of 1.50 ml oil/g protein and bulk density of 0.71 gm/ml.     

Protein and gossypol extractability from cottonseed flour

The extractability of protein and free-gossypol from fully gossypolised cottonseed flour was investigated. The various parameters studied include (i) effect of pH (ii) effect of salts and (iii) the combined effect of pH and salts. The results indicated that it is possible to obtain a protein isolate free from free-gossypol by alkaline extraction at pH values of 9 and 10. Highest protein extraction (57%), highest protein recovery (96%) and highest protein content of the precipitate (75%) occurred at pH 10. In general, dilute aqueous electrolytes did not accomplish significantly higher extracta-bilities although they resulted in comparatively lower free-gossypol contents in the protein precipitate. However, with 1.0m CaCl2 protein extraction was 75% but both protein recovery (61%) and the protein content of the precipitate (61%) was comparatively low. Extraction in the presence of salts and alkali did not improve protein extractability and gave a protein isolate high in free-gossypol content.     

SOLUBILIZATION AND FUNCTIONAL PROPERTIES OF MOTH BEAN (VIGNA ACONITIFOLIA (Jacq.) Marechal AND HORSE GRAM (MACROTYLOMA UNIFLORUM (Lam.) Verdc. PROTEINS

Horse gram and moth bean seeds contained 23.6% and 21.9% protein (N x 6.25), respectively. Both the legumes are rich sources of iron. The iron contents in horse gram and moth beans were 11.0 and 9.6 mg/100 g, respectively. NaCl at 10% (w/v) and Na₂CO₃ at 0.5% (w/v) were found to be effective in extracting 89% and 80% of moth bean and horse gram proteins from defatted flour The minimum solubility of horse gram proteins from defatted flour was at pH 4.0 whereas proteins from moth bean exhibited minimum solubility at pH 4.5. The water and oil absorption, and foaming capacities in case of horse gram and moth bean flours were 2.0 g/g and 2.2 g/g, 23.0% and 2.0 g/g, 1.6 g/g, 27.6%, respectively.     

Sodium chloride as a preferred protein extractant for pork lean meat

The protein extractability of sodium chloride (NaCl), potassium chloride (KCl) and lithium chloride (LiCl) under a range of molarity with in the physiological pH range (pH 6.0–8.0) was assessed to determine the best protein extractant for pork lean meat. The individual proteins in the extracts were identified by electrophoresis. The highest protein extractabilities at pH 7.0 for NaCl, KCl and LiCl were observed at 1.2, 1.1, and 1.1 M, respectively. There was no significant difference in protein extractability for KCl and LiCl within physiological pH range. NaCl had a significant increase of its protein extractability as pH increased from 6.0 to 6.5 followed by a relatively constant extractability. The NaCl had the highest protein extractability followed by LiCl and KCl. The maximum number of proteins (26 bands) was found at the optimum concentration of each salt. However, resolution and clarity of bands were better in NaCl extracts. The pH variation does not affect the number and the intensity of the bands.     

Extraction of nitrogenous material from winged bean [Psophocarpus tetragonolobus (L.) DC] flour and the preparation and properties of protein isolates

The extractability of nitrogenous material from the seeds of 12 winged bean accessions has been investigated. Little variation in nitrogen content and extractability in water or salt solution was obtained, although decortication considerably reduced the levels of extraction. The effect of three oil extraction procedures on the extractability of nitrogenous material at different pH values is reported. Protein isolates were prepared and simple laboratory tests were used to evaluate their functional properties. The prepared winged bean isolates possessed very low bulk densities and high fat absorption values and the relationship between these factors was investigated further. Winged bean isolates showed high (100%) nitrogen dispersibilities and were able to form heat-stable emulsions. They did not form gels under the conditions used except in the presence of CaCl₂. Isolates prepared from unheated winged bean flour formed stiff but unstable foams. The relationship between the oil extraction procedure and isolate yield, purity and functional properties is discussed.     

Investigation of Faba Bean Protein Recovery and Application to Pilot Scale Processing

Extraction and precipitation conditions were assessed for recovery of protein from dehulled faba bean flour on a laboratory scale. 10°C versus 20°C extraction did not affect solubility of nitrogenous components. However, more were extracted at pH 9 or 10 than at pH 7. Tap water extracted slightly more nitrogenous materials than 0.3M sodium chloride. Study of pH 4.0 to 5.3 for protein precipitation showed a higher yield of protein was obtained at lower pH. However, apparently simultaneous precipitation of nonproteinaceous material caused overall lower protein composition of the isolates from lower pH. Pilot scale processing of dehulled faba bean flour produced an isolate which was 92.5% protein, and represented a yield of 48% of the original protein.     

Functional-Properties of Raw and Heat Processed Brown Bean (Canavalia rosea DC) Flour

The proximate composition and the functional properties of the flour of brown bean (Canalia rosea DC) were investigated. Brown bean flour had 27.1 g/100g dry weight (DW) crude protein and 7.6 g/100g DW ether extractives. The brown bean flour had good water and oil absorption but poor gelation properties. Solubility of the brown bean protein was minimal at pH 4.0 but increased at pH 10. Foaming capacity of the flour could be improved by increasing concentration as well as by adding NaCl and was influenced by pH. Emulsion capacity was dependent on pH and salt concentration. Heat processing generally reduced the foamability and emulsification capacity of the brown bean flour.     

胶束化和碱溶酸沉提取羽扇豆蛋白的物化特性

利用胶束化和碱溶酸沉2 种提取方法从羽扇豆中提取羽扇豆蛋白,并对2 种方法提取羽扇豆蛋白的物化特性进行研究。结果表明：羽扇豆蛋白分子质量主要集中在18～90 kDa之间,是由多种分子质量的蛋白组成。碱溶酸沉提取羽扇豆蛋白的氨基酸总含量（66.2%）显著（P＜0.05）高于胶束化提取羽扇豆蛋白的氨基酸总含量（27.8%）。2 种提取方法提取羽扇豆蛋白的等电点pI接近5.0。胶束化提取羽扇豆蛋白的持水性显著（P＜0.05）高于碱溶液酸沉法提取的羽扇豆蛋白,而持油性无显著差异（P＞0.05）。碱溶酸沉法提取羽扇豆蛋白的起泡性在pH 2.0～6.0之间显著减小,在pH 6.0时起泡性最低,其泡沫稳定性的变化趋势与其起泡性类似。而胶束化提取羽扇豆蛋白的起泡性受pH值的影响不显著（P＞0.05）。胶束化提取的羽扇豆蛋白在pH 4.0时乳化性最小,然后随pH值的升高蛋白乳化活性也随之增加,2 种提取方法所提羽扇豆蛋白在pH 10.0时乳化活性最高。碱溶酸沉法提取的羽扇豆蛋白在pH 4.0时溶解度最小,而随着pH 4.0～10.0的增加,蛋白溶解度迅速增加。而胶束化提取羽扇豆蛋白的溶解度随pH 2.0～10.0的升高也逐渐增大。该研究为羽扇豆蛋白在食品工业中的开发与应用提供一定理论支持。     

PARTICLE SIZE, SALT CONCENTRATION and TEMPERATURE EFFECTS ON NITROGEN EXTRACTION of CHICKPEA (Cicer arietinum) BY RESPONSE SURFACE METHODOLOGY

This study was conducted to evaluate the effect of time, pH, particle size, %NaCl and temperature on total nitrogen (TN) extraction of low commercial grade chickpea ( Cicer arietinum ) grain, in order to find the optimum extraction conditions for further processing. Extraction times used were 30, 60, 90 and 120 min and the nitrogen extraction curve was carried out at a pH range of 2.0 to 11.0. Response surface methodology was used to evaluate the effect of particle size (100, 150 and 200 mesh), salt concentration (0, 0.3 and 0.6% NaCl) and temperature (25, 35 and 45C). No significant time effect was found on nitrogen extractability. However, a great pH effect on nitrogen extraction was observed. Results from the RSM analysis showed that the most adequate conditions for total nitrogen extraction were particle size, 200 mesh; 0.0% NaCl; pH 8.0; temperature, 25C; and time, 30 min. By using the above mentioned parameters a yield over 90% of nitrogen was obtained.     

金鲳鱼加工副产物中碱溶性蛋白的提取及性质测定

为了实现对金鲳鱼加工副产物的高值化利用,本研究采用碱提法,通过单因素及正交试验确定了金鲳鱼加工副产物中碱溶性蛋白提取的最佳工艺,并对碱溶性蛋白的相关性质进行了分析测定。结果表明:碱溶性蛋白的最佳提取工艺条件为:碱提浓度0.3 mol/L、料液比1:8 g/mL、碱提温度50 ℃、碱提时间70 min,碱溶性蛋白提取率达到83.71%;碱溶性蛋白的等电点为4.6,pH9.0时溶解度最大,吸油性为5.5 mL/g,吸水性为1.85 mL/g,乳化性为43.44%,起泡性为75.33%,起泡稳定性为37.5%;氨基酸组成分析表明,其必需氨基酸(除色氨酸外)含量为47.84%,鲜味氨基酸含量为34.23%;SDS-PAGE显示,碱溶性蛋白分子量主要分布在90、70、65、44.3 kDa的4个条带区域。本研究可以为金鲳鱼副产物的深加工提供一定的技术基础。