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.     

Nitrogen extractability of sesame (Sesamum indicum L.) seed and the preparation of two protein isolates

Nitrogen extractability from sesame flour in water is greatest using a flour: solvent ratio of 1:40 and an extraction time of 15 min. At pH 4.0-6.5, <10% nitrogen is extracted, whilst >90% is extracted at pH 11.0. In the presence of NaCl (0.5-1.0M) nitrogen extractability is greatest at pH values > pH 4.0. The two sesame protein isolates produced were bland-tasting, light-coloured and contained approximately 95% protein. The alkali isolate (extracted in water at pH 10.0 and precipitated at pH 4.0) was readily solubilised and showed a good protein recovery (60%). The salt isolate (extracted in 1M NaCl at pH 6.0 and precipitated at pH 4.0) was less soluble and showed a lower protein recovery (50%). The sesame products were extracted sequentially using various solvents. Sesame flour proteins were mainly salt-soluble (67%), alkali isolate proteins mainly water-soluble (41%) and alkali-soluble (41%), and salt isolate proteins mainly alkali-soluble (35%). The amino acid composition of the sesame products is described. Oil-expelled cake showed poor nitrogen extractability (53% at pH 11.0 in water) and was, therefore, a poor source for protein isolate production.     

EFFECT OF SEVERAL VARIABLES ON THE EXTRACTABILITY OF SUNFLOWER SEED PROTEINS

SUMMARY— The effect of several variables on the extraction of sunflower seed protein has been investigated. Solubility studies on the meal show that globulin is the main protein component. Albumin, nonprotein nitrogen and insoluble nitrogen are very low. Glutelin comprises about 17% of the total nitrogen. 15 min and a meal to solvent ratio of 1:10 (w/v) were found to extract a maximum amount of protein at pH 7.0. The optimum temperature of extraction is 45°C, although over a temperature range of 26-6°C the extraction remains essentially constant. More protein was extracted by 1.0 M NaCl and 0.75 M CaCl₂ at various pH's than by the higher or the lower concentrations of these salts. Results with several other salts show that concentration as well as pH is very important. Reducing agents do not appear to have any marked effect on the extractability of protein.     

Physicochemical and functional properties of full‐fat and defatted Moringa oleifera kernel flour

Full‐fat and defatted Moringa oleifera kernel flours were analysed for their functional properties. The effect of pH and NaCl concentrations on the functional properties of the flours was investigated following standard procedures. The protein content of full‐fat and defatted flour was 36.18 and 62.76 g/100 g, respectively. The concentrations of other proximate constituents of the defatted flour were higher than those of the full‐fat flour. Nitrogen solubility was lowest at pH of 4.0 and 9.0, respectively, with maximum solubility occurring at pH of 6.0. Defatting increased the water absorption and fat absorption capacities of Moringa oleifera kernel flour. The foaming capacity and foam stability of the defatted flour were 86.0% and 82.0 mL, whereas that of full‐fat flour were 20.6% and 18.5 mL respectively. The defatted flour showed better emulsification (97.2 mL g^?1) than full‐fat flour (66.0 mL g^?1). The least gelation concentration of the defatted and full‐fat flours was 14% and 16% (w/v) respectively. Moringa oleifera kernel flour can be a valuable source of vegetable protein in fortified food products formulation.     

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.     

The extractability of winged bean (Psophocarpus tetragonolobus) seed trypsin inhibitors

The extractability of winged bean (Psophocarpus tetragonolobus) seed trypsin inhibitors by aqueous salt solution varies with pH as well as the ionic strength of the extraction medium. With a high ionic strength extraction medium, the extractability of the seed trypsin inhibitors increases with rising pH. With a low ionic strength extraction medium, however, a region of minimum extractability of trypsin inhibitors was observed at pH 4. At pH above 7, the same maximum amount of trypsin inhibitors (1.47 million inhibitor units (i.u.) per 100 g of seed meal) was extracted with both high and low ionic strength extraction media. The solution characteristics of winged bean seed proteins exhibited similar trends. Ninety-five per cent of the extracted seed trypsin inhibitors could be precipitated from 30–70% saturated ammonium sulphate solutions. The winged bean seed trypsin inhibitors isolated by ammonium sulphate fractionation lost all inhibitory activity when heated at 100°C for 10 min at alkaline pH.     

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.     

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.     

Studies on yield,extracted leaf protein and deproteinised extract of winged bean grown as a biennial crop

The possible use of the long vegetative growing period of the winged bean, when grown as a biennial crop, as a source of extractable leaf protein was investigated in this study. The dry top yield of the crop during this period increased curvilinearly with time and followed the logistic growth law. A linear decrease with age was noted for the total and protein nitrogen extractability of this crop whereas the nitrogen percentage in dry matter of leaves and the extractable leaf protein yield gave a quadratic response. Unfractionated and heat fractionated proteins extracted from the leaves contained 61.9–85.3% protein, 4.6–12.8% fat, 0.2–4.6% ash, 0.5–2.7% crude fibre and 34.2–43.7 mg 100 g^?1 β-carotene on moisture free basis. The deproteinised juice, left after protein extraction, was also found to be ideally suited as a microbial growth medium for protein rich biomass production.     

Functional Properties of Lupin Seed (Lupinus mutabilis) Proteins and Protein Concentrates

Functional and electrophoretic properties of the seed flour and a protein concentrate prepared by alkaline extraction from lupin seeds (Lupinus mutabilis, cultivar H-6) were investigated. SDS-PAGE indicated presence of 13 and 12 subunits in the seed flour proteins and the protein concentrate, respectively. Lupin protein concentrate had good water and oil absorption and gelation properties. Solubility of lupin proteins was minimum at a pH of 4.0 but increased rapidly beyond pH 5.0. Foaming capacity of the protein concentrate could be improved by increasing concentration as well as by adding NaCl and was influenced by pH and incorporation of certain carbohydrates. Emulsion properties of lupin proteins were concentration and pH dependent. Moist heat improved the in vitro digestibility of the seed proteins. The seed flour as well as the protein concentrate did not have detectable trypsin, chymotrypsin, and α-amylase inhibitory activities.     

Nitrogen extraction from defatted rapeseed,with particular reference to United Kingdom commercial rapeseed meal

Nitrogen extraction profiles of rapeseed (RS), post-press cake (PP) and commercial rapeseed meal (RSM), drawn from the same batch, were evaluated; the RS and PP being defatted in the laboratory prior to extraction. The RSM exhibited lower nitrogen extractability, with the profiles less sharply defined, at different conditions of pH and ionic environment than for RS or PP. This was attributed to the heat treatment received at the end of the process during the toasting-desolventisation. The nitrogen extractability of RSM was further investigated using double extraction techniques with different solvents (NaCl, CaCl₂ and water), over a wide range of pH. None of the extraction regimes studied suggested improved practical possibilities for meal protein extraction, compared with single aqueous extraction at high pH. Meal protein extracts however, were found to be comparatively high in crude protein when expressed on a solids basis, a fact which suggests the possibility for additional concentration by ultrafiltration.     

Extractability of African yam bean (Sphenostylis stenocarpa) protein in acid, salt and alkaline aqueous media

Protein extractability from defatted Africa yam been (Sphenostylis stenocarpa) was studied under various conditions: solid/solvent ratio, time, pH, and salt. Extractable protein from S. stenocarpa was strongly dependent on all these factors. Maximum extractable protein was obtained after 2 h extraction time; the solid to solvent ratio in the range of 1:20–1:50 gave maximum protein extractability. The pH corresponding to maximum and minimum extractable proteins were 10 and 5, respectively, but addition of NaCl changed this slightly. Extractable protein of 92%, 88% and 84% were obtained in aqueous concentration of 0.01 MNa₂SO₄, 1.5 MNaCl and 0.01 MNaOH, respectively while other concentrations gave lower extractability. These salt concentrations, i.e. 0.01 MNa₂SO₄ and 1.5 MNaCl gave slightly lower extractable protein under alkaline condition. S. stenocarpa flour has a higher buffer capacity in acid medium than in alkaline medium.     

Isoflavone content in soy germ flours prepared from two drying methods

Isoflavone glucosides and aglucons in various soybean varieties (Chiang Mai‐60, S.J.‐5, Chiang Mai‐2, Srisumrong‐1, and Nakhonsawan‐1) harvested from dry vs. rainy seasons were quantified. Isoflavone contents of all soy germs ranged from 16.5 to 30.6 μmol g^?1. Regardless of varieties, isoflavone contents in germ of seeds from dry season were higher (P < 0.05) than those from rainy season. The Chiang Mai‐60 germ, having the highest isoflavone content (30.6 μmol g^?1), was selected for germ flour production. Freeze‐dried germ flour contained higher isoflavone aglucons (17.72 μmol g^?1 daidzein; 6.48 mg g^?1 glycitein; 4.28 μmol g^?1 genistein) than those (15.07; 5.59; 3.41) of drum‐dried germ flour. However, isoflavone glucoside contents in freeze‐dried germ flour (3.27 μmol g^?1 daidzin; 1.86 μmol g^?1 glycitin; 1.41 μmol g^?1 genistin) were lower than those (5.22; 3.15; 1.89) of drum‐dried germ flour. Total isoflavone contents of drum‐dried and freeze‐dried germ flours were comparable (34.32 vs. 35.02 μmol g^?1) but more than that (30.16 μmol g^?1) of unprocessed germ flour.     

Composition and properties of seeds and pods of the tree legume Prosopis juliflora (DC)

Seeds and whole pods of Prosopis juliflora were analysed for proximate composition, fatty acids, minerals and soluble sugars. Crude protein constituted 35 % and 10 % of the seeds and whole pods, respectively. Nitrogen free extracts (NFE) comprised approximately 45 % of the seeds and whole pods. In the case of the pods, sucrose represented approximately 75 % of the soluble sugars. The lipid of both the seeds and whole pods contained a relatively large proportion of unsaturated fatty acids with linoleic acid as the predominant fatty acid. Levels of the macronutrients Ca, Mg, K and P were relatively low in comparison with cultivated legumes. Alkaline extraction of the seeds and whole pods showed that more than 70 % of the proteins were extractable. Maximum precipitation of the proteins was observed in the pH range 4.0-4.5. Amino acid analysis of the isolated proteins showed relatively high levels of lysine (312mg g^?l N for the seed and 438 mg g^?l N for the pod protein) and adequate levels of valine, leucine, tyrosine and phenylalanine. Methionine was the most limiting amino acid. The in vitro enzymic digestibility of the proteins of Prosopis seed was comparable to that of proteins of other legume seeds.     

Functionality of native and denatured cashew nut kernel protein isolates at isoelectric pH as a function of salt concentration

The reduced solubility of proteins near the isoelectric pH limits their use in food formulations whose pH lies in the range 5.0–6.0 because of poor functionality. In the present study, the effect of salt on the functionality of native and denatured cashew nut kernel protein isolates at the isoelectric pH was investigated. Both isolates showed improvement in their functional properties, but the improvement was greater for the denatured protein isolate. The solubilities of denatured and native protein isolates at the isoelectric pH increased from 26.4 g l^?1 and 64 g l^?1, respectively, without salt to maxima of 363 and 308 g l^?1, respectively, at 0.75 M salt concentration. The water binding capacity of the isolates increased with increase in NaCl concentration from 1.70 ml g^?1 to 1.77, 1.82, 1.92 and 2.2 ml g^?1 for denatured protein isolate and from 1.45 ml g^?1 to 1.65, 1.69, 1.82 and 1.97 ml g^?1 for native protein isolate at 0.25, 0.50, 0.75 and 1.0 M salt concentrations, respectively. When the properties of the isolates in 0.75 M NaCl solutions were compared with those in salt‐free water there were 15% and 116% increases in emulsifying capacity, 40‐fold and 45‐fold increases in emulsifying activity and 4.6‐fold and 40‐fold increases in emulsion stability for native and denatured protein isolates, respectively, whilst the corresponding foaming capacities increased from 4 to 5.5 and 0 to 8.9 ml g^?1 protein. Statistically, no difference in the foaming capacity of either of the isolates was observed above 0.5 M NaCl. The foam stability also exhibited similar behaviour. Copyright © 2004 Society of Chemical Industry     

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.     

Compositional and degradative changes during the manufacture of dry‐cured ‘lacón’

The gross and mineral composition, the main physicochemical parameters, the protein extractability and the proteolytic (nitrogen fractions and free amino acids) and lipolytic (acidity index and free fatty acids) changes were studied throughout the manufacturing process of five batches of dry‐cured ‘lacón’, a traditional Spanish meat product made from the fore‐ham of the pig following a similar technological process to that of dry‐cured ham. The main compositional characteristics of this product are the high NaCl content and the low moisture content at the end of the curing process. The pH remained fairly stable (around 6) throughout the whole process and a fall in a_w was observed, reaching very low (0.767 ± 0.052) final average values. It was noted that 76% of the sarcoplasmic and 83% of the myofibrillar proteins became insoluble during the manufacturing process. The values of the different nitrogen fractions increased in a significant manner during manufacture, reaching low final values that indicate that ‘lacón’ undergoes a low level of proteolysis in comparison with other products manufactured by similar technologies. The high NaCl content and the intense dehydration suffered during the manufacturing process appear to be the principal causes of this reduced protein degradation. In accordance with the limited increase in the α‐amino acidic nitrogen during ripening, the total free amino acid content increased slightly but significantly from average values of 4371 mg kg^?1 dry matter in fresh pieces to average values of 13 020 mg kg^?1 dry matter in pieces at the end of the ripening process. The profile of free amino acids in the final product was similar to that observed by other authors in dry‐cured ham. The acidity of the fat increased by a factor of five. The final average values (49.9 g oleic acid kg^?1) were lower than those determined in dry‐cured ham, which indicates that ‘lacón’ undergoes less lipolysis during the ripening process than dry‐cured ham. C18 : 1, C18 : 2 and C16 were the most intensively released fatty acids during curing. The profile of free fatty acids in the end product was in agreement with that observed by other authors in dry‐cured ham. Copyright © 2003 Society of Chemical Industry     

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.     

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.     

Extraction of nitrogenous constituents from Leguminosae spp. Comparison of solubility characteristics for different species and the effect of processing conditions on protein concentrate yield

Studies were made on the solubility of nitrogen from vetch (Vicia sativa), horse bean (Vicia faba minor), pea (Pisum sativum) and lupin (Lupinus albus) seeds. With a fixed meal:solvent ratio, N-solubility is greatly increased when the pH of dispersion increases, until a pH value between 6.1-7.9 is reached. Using a fixed quantity of alkali (g NaOH kg^?1 seed meal) the pH of the suspension was kept constant. This pH was lowest with lupins and highest with vetch. The same held for solubilisation of nitrogen. For all four species, there seems to be a critical quantity of alkali below which N-solubility is poor, while above it there is little improvement. With a fixed pH of dispersion, increasing meal: solvent ratio from 10 to 50% resulted in a small decrease in N-solubility. For protein concentrate production, alkali solubilised substances were separated from the residual meal by centrifugation. The oven-dried concentrates had protein contents of 63-75%. Total protein and dry matter yield of protein concentrates (both on dry seed meal basis) ranged from 10.9 to 30.9 and from 22.6 to 49.6%, respectively, depending on seed species and conditions of extraction. In all cases yield was higher in concentrates from lupin seeds. The mineral content of protein concentrates was approximately twice that of their raw material, except for sodium.