Physicochemical and functional properties of albumin,globulin and glutelin fractions of green lentil seed

Defatted lentil seed flour proteins were separated into their constituent albumin (ALB), globulin (GLB) and glutelin (GLT) fractions followed by determination of their structural and functional properties. The GLB fraction demonstrated superior solubility (84%–100%) at acidic and alkaline pH values when compared to the lower values for ALB and GLT. Amino acid composition analysis showed lower contents of hydrophobic and sulphur-containing residues for GLB. However, GLB had the highest in vitro protein digestibility, which may be due to lower contents of rigid secondary structure fractions like the β-sheet and β-turns. In contrast, water and oil holding capacities as well as gelling ability were better for GLT and ALB than GLB. The GLT fraction formed very poor emulsions at pH 3 and 5 but emulsification was significantly (p < 0.05) improved (smaller oil droplets) at pH 7 and 9. Foaming capacity was strongest for GLB, especially at pH 5, 7 and 9 where increase in protein concentration had a negative effect on foam formation. Overall, the protein type and pH of the environment had stronger effects on emulsion and foaming properties than the protein concentration.     

Effects of Soy Hull Flour on Soy Proteins Emulsions

Soy hull flour (SHF) was added to a soy protein solution (100 mg/.50 mL D.W.) to determine the effects of the SHF on the characteristics of the soy protein emulsion. A greater amount of oil was emulsified in the presence of SHF at pHs above 4.5. The amount of oil emulsified increased sharply with addition of up to 5g SHF. Emulsion capacity of total protein in the system decreased with addition of SHF. Viscosity increased drastically at alkaline pH at constant level of SHF. Stability increased slowly up to 5g addition then decreased rapidly. Stability was improved with the inclusion of SHF at pHs above 4.5.     

Protein precipitating capacity of phenolics of wild blueberry leaves and fruits

Phenolics (PP) were extracted from blueberry leaves and fruits with 70% (v/v) acetone and 95% (v/v) ethanol. The lyophilized crude PP extract was then fractionated on a Sephadex LH-20 column using first 95% (vv) ethanol as a mobile phase for elution of fraction of phenolics low in tannins then 50% (v/v) acetone to elute fraction rich in condensed tannins. Bovine serum albumin (BSA) was effectively precipitated by crude PP extracts at pH values between 4 and 5. A statistically significant (P < 0.05) linear relationship exists between the amount of PP–protein complex precipitated and the amount of PP added to the reaction mixture. The slope values of these lines indicated the tannin-rich fractions of crude PP extracts to be more effective protein precipitants than the other examined fractions. Based on the amount of gelatin, fetuin and BSA required to inhibit the formation of the dye-labeled BSA-PP complex by 50%, gelatin was 4–15 times more effective as a precipitation inhibitor than unlabeled BSA and fetuin.     

Control of yeast neutral trehalase by distinct polyphosphates and ribonucleic acid

The activity of yeast trehalase when assayed at pH 7 in a crude extract was found to increase 2- to 3-fold upon incubation with 0.1% (v/v) polyethyleneimine or other polycations such as polylysine (0.075-mMol) and calf thymus histones (0.08 mMol). Incubation with 3 mM-Mn2+ and 5 mM-Ca2+ also led to 3- and 1.6-fold increases in trehalase activity, respectively. The activities of 11 other enzymes assayed in the crude yeast extract did not increase after addition of polyethylene imine. At concentrations of polyethyleneimine that maximally stimulated trehalase activity, 97% of the total RNA present in the crude extract, 40% of total protein, and 60% of the polyphosphate (assayed as inorganic phosphate liberated during 7 min incubation at 95 degrees C and pH O) were found to be precipitated. A similar finding was made with trehalase-stimulating concentrations of Mn2+. Activation of trehalase by polyethylene imine rendered this enzyme susceptible to inhibition by a preparation of total yeast RNA, inorganic polyphosphates, and related polyanions. We present further evidence that the removal of a distinct RNA and/or polyphosphate is the basic principle of polyethyleneimine-induced activation of trehalase. A more pronounced stimulation of trehalase activity (4-fold) could be obtained by enzymatic phosphorylation with ATP in the presence of cyclic AMP and Mg2+ as described by van Solingen and van der Plaat (1975) [9].(ABSTRACT TRUNCATED AT 250 WORDS)     

ENZYMATIC DIGESTION OF MUSCLE FROM MENHADEN (BREVOORTIA SPP.) AT DIFFERENT pHs

Solubilization of muscle from South American menhaden, Brevoortia spp., was done with and without added proteolytic enzymes. Pepsin and trypsin were isolated from the stomach and the pyloric caeca of croaker (Micropogonias furnieri) respectively, and used for enzymatic solubilization. Digestion of muscle proteins was carried out at 8C for 20 h with the pH maintained at either 3, 4, 5, 6, 7, 8, 9 or 10. The hydrolytic action was evaluated by measuring the concentration of peptides and proteins solubilized from previously frozen muscle or from lyophilized muscle.
The protein solubility of menhaden muscle was optimum at basic pH; approximately 50–60% of the previously frozen or lyophilized muscle was soluble after incubation without added enzyme at pH 9.0. All of the protein was solubilized from lyophilized menhaden muscle with purified trypsin at pH 10.0. Addition of croaker pepsin to menhaden muscle increased protein solubility by only 10–15%. Digestion of menhaden muscle with both pepsin and trypsin from croaker resulted in a similar increase in protein solubility as obtained by addition of only trypsin.
Similar results were obtained with crude croaker stomach extracts and with purified pepsin, and also with crude pyloric caeca extract and with purified trypsin. Complete solubilization of menhaden muscle with croaker pyloric caeca extract may be an inexpensive way to separate the protein from lipids and prepare a protein isolate from this underutilized specie. Additional work is needed to characterize the functional properties of the menhaden protein extract obtained by digestion of the flesh at alkaline pH with croaker trypsin.     

Antioxidant activity of protein extracts from heat-treated or thermally processed chickpeas and white beans

In this study, antioxidant activities of water-soluble protein extracts from chickpeas and white beans were investigated. The area under the curve (AUC) values of lyophilized crude protein extracts (dialyzed or undialyzed) from thermally processed (121 °C for 20 min) or heat-treated (90 °C for 20 min) chickpeas (73–91 μmol trolox/g) and white beans (39–67 μmol trolox/g) indicated a higher free radical-scavenging capacity and thermostability for chickpea proteins than for white bean proteins. The thermal processing also increased the Fe⁺²-chelating capacity of lyophilized chickpea crude protein extracts 1.8-fold whereas it caused a 2.3-fold reduction in the Fe⁺²-chelating capacity of lyophilized white bean crude protein extracts. Dialysis increased the protein content of lyophilized chickpea extracts 1.5–2-fold but it did not affect the protein content of lyophilized white bean extracts significantly. Ammonium sulfate precipitation was not effective for selective precipitation of antioxidant proteins. However, it improved the free radical-scavenging capacity of lyophilized protein extracts from thermally processed chickpeas and white beans by almost 25% and 100%, respectively. DEAE-cellulose chromatography, indicated the presence of five (A₁–A₅) and three (B₁–B₃) antioxidant protein fractions in heat-treated and thermally processed chickpea protein extracts, respectively, and can be used for the partial purification of antioxidant proteins. The results of this study showed the good potential of chickpea proteins as thermostable natural food antioxidants.     

Role of β-conglycinin and glycinin subunits in the pH-shifting-induced structural and physicochemical changes of soy protein isolate

Soy β-conglycinin (7S) and glycinin (11S) were incubated up to 4 h in acidic (pH 1.5 to 3.5) or alkaline (pH 10 to 12) solutions to induce protein structural unfolding followed by refolding 1 h at pH 7.0, a process known as pH-shifting. The pH-shifting markedly increased (P < 0.05) emulsifying activity of 11S and to a lesser extent 7S; the former also produced more uniform oil droplets. The emulsifying activity improvements were accompanied by a significant rise in protein surface hydrophobicity, slight loss of the secondary structure (circular dichroism), and substantial dissociation of disulfide-linked basic and acidic 11S subunits. The findings suggested that 11S globulins of soy protein isolate (SPI) were more responsive to pH-shifting treatments than were 7S globulins, and the resulting emulsifying activity enhancements of 11S, in parallel with that of SPI, were indicative of its determinant role in the overall emulsifying properties of pH-shifting-treated SPI. PRACTICAL APPLICATION: Extreme alkaline (pH 12) and acidic (pH 1.5) medium treatments can significantly modify the structure and enhance the emulsifying properties of both β-conglycinin and glycinin components of SPI. The functionality improvement by the pH processes is more remarkable for the glycinin protein fraction. Therefore, SPI enriched with glycinin seems to be particularly suitable for extreme acidic or alkaline processes to produce surface-active functional ingredients for food applications.     

Effect of ionic strength and/or pH on Extractability and physico-functional characterization of broad bean (Vicia faba L.) Protein concentrate

Protein extractability studies showed that the protein of broad bean (Vicia faba L.) was extractable at both acidic and basic pH. The percentage of pH-12 extractable protein that was precipitated at pH 4 (isoelectric point) from protein concentrate, dehulled full-fat seed flour and whole seed flour are 62.0%, 61.2% and 71.6%, respectively. Low ionic strength (μ0.4) increased the solubility of the protein in the bean concentrate at acidic pH, while at alkaline pH, increase in ionic strength (0.1–2.0) had an inverse relationship on the concentrate protein solubility. The capacity to form protein-stabilized foam was least (34%) at pH 4 and highest (97%) at pH 12. These were increased to 62% (pH 4) and 139% (pH 12) in medium with ionic strengths of 0.2 and 0.4, respectively. The foam formed was more stable at pH 4 than at the other pHs. Low ionic strength of 0.1 improved water absorption capacity but reduced it at ionic strength of 0.6.     

烟草米根霉致病力及不同渗透压和pH环境下的代谢表型特征分析

为明确温度、叶位和创伤对烟叶霉烂病病原菌米根霉致病力的影响,及不同渗透压和pH环境下病原菌的代谢表型特征,采用穿刺法接种烟草离体叶片,测定了米根霉在不同温度及不同叶位烟叶中的致病力,并在Biolog PM 9和PM 10代谢板中96种渗透压和96种pH环境下培养米根霉,分析了其代谢表型特征.结果表明,米根霉可致病的温度...     

Isolation and characterization of protein isolated from defatted cashew nut shell: Influence of pH and NaCl on solubility and functional properties

This work reports the isolation of protein from defatted cashew nut shell (CNS), with the crude protein product containing 91.07% protein. Under its natural conditions, the solubility of this protein isolate is comparable (74.02%) to that of mustard green meal protein. The solubility of the protein isolate decreases with decreasing pH, with the minimum solubility observed at its isoelectric point (pH 3). The water holding capacity, oil holding capacity, foaming capacity, foam stability, emulsifying capacity and emulsion stability were found to be 2.56 cm³ H₂O/g protein, 4.28 cm³ oil/g protein, 76.88%, 70.98%, 62.0% and 79.0%, respectively. The profiles of these functional properties were determined with varying pH values and NaCl concentrations, and improved properties were observed in the alkaline pH range and in the presence of NaCl. Electrophoretic analysis showed that the high molecular weight protein globulin was the major protein in the protein isolate.     

Factors influencing the production of o/w emulsions stabilized by β-lactoglobulin–pectin membranes

A primary emulsion was prepared by homogenizing 10 wt% corn oil with 90 wt% aqueous β-lactoglobulin solution (0.5 wt% β-lg, pH 3 or 7) using a two-stage high-pressure valve homogenizer. This emulsion was mixed with aqueous pectin (citrus, 59% DE) stock solution (2 wt%, pH 3 or 7) and NaCl solution to yield secondary emulsions with 5 wt% corn oil, 0.225 wt% β-lactoglobulin, 0.2 wt% pectin and 0 or 100 mM NaCl. The final pH of the emulsions was then adjusted (3–8). Primary and secondary emulsions were ultrasonically treated (30 s, 20 kHz, 40% amplitude) to disrupt any flocculated droplets. Secondary emulsions were more stable than primary emulsions at intermediate pHs. Secondary emulsions prepared at pH 7 had smaller particle diameters (0.35 to 6 μm) than those prepared at pH 3 (0.42 to 18 μm) across the whole pH range studied, and also had smaller diameters than the primary emulsions (0.35 to 14 μm). Ultrasound treatment reduced the particle diameter of both primary and secondary emulsions and lowered the rate of creaming. The presence of NaCl screened the charges and thus the electrostatic interaction between biopolymer molecules and primary emulsion droplets. Secondary emulsions were more stable to the presence of 100 mM NaCl at low pHs (3–4) than primary emulsions. This study shows that stable emulsions can be prepared by engineering their interfacial membranes using the electrostatic interaction of natural biopolymers, especially at intermediate pHs where proteins normally fail to function.     

pH-dependent characteristics of gel-like emulsion stabilized by threadfin bream sarcoplasmic proteins

Threadfin bream sarcoplasmic proteins (TBSP) were identified by 2-dimensional polyacrylamide gel electrophoresis and the major proteins were likely be pyruvate kinase, creatine kinase, aldolase, and carbonic anhydrase. Emulsifying and rheological properties of emulsion stabilized by TBSP at pH 3, 7.5, and 12 were investigated. Surface hydrophobicity of TBSP increased with pH. Emulsifying activity index was highest at pH 3 followed by pH 12 and pH 7.5. The mean droplet diameter (d_3,2) was in the order of pH 7.5 > pH 3 > pH 12 at oil volume fraction ranging from 0.1 to 0.5. A decrease of oil volume fraction resulted in a reduction of oil droplet diameter. At oil volume fraction of 0.5, TBSP-stabilized emulsion at pH 7.5 and 12 exhibited gel-like characteristics, while liquid emulsion was observed at pH 3, based on visual observation and dynamic rheological analysis. Storage modulus (G′) values of emulsion at all studied pH values increased with temperature, implying the development of protein gel network upon heating. The gel-like emulsion at pH 12 absorbed more protein and water than at pH 7.5. Protein retention and water holding capacity of emulsion increased with oil volume fraction. Hydrophobic interactions between proteins and oil droplets were likely responsible for the development of a gel-like emulsion.     

Influence of heat processing on functional properties of Australian wattle seed (Acacia victoriae Bentham) extracts

Whole wattle (Acacia victoriae Bentham) seed was extracted with water before or after a soaking/heat treatment regime designed to destroy its protease inhibitors. The yield, composition and physical properties of these extracts were measured and they were then subjected to an analysis of their functional properties, which included emulsion and foam formation and stabilization, solubility at different pH values and gelling ability. Processing of soaked wattle seed at 100 °C for 30 s led to a much reduced extract yield and viscosity at both pH 4 and 7, decreased its water-soluble carbohydrate content but increased its protein content, and solubility under alkaline conditions. Processing of wattle seed before extraction also led to increased emulsion droplet size and reduced emulsion stability, the differences being more pronounced in emulsions formed with 20% oil compared with 50% oil-in-water emulsions. Comparatively, the emulsions formed using extract from non-processed wattle seed were very stable at both 20% and 50% oil levels, especially at pH 7 where the enhanced viscosity of the extract predominated. All extracts had very low foaming capacity, and gelation did not occur in any of the samples even at 10% (w/v) extract concentration.     

Effects of aqueous brewing solution pH on the extraction of the major green tea constituents

The pH of the aqueous brewing solution was maintained at values ranging from 1 to 9 during the green tea extraction and the effects on the tea's extracted constituents were studied. The epistructured catechins were stable under acidic conditions but epimerized or degraded at pH ≥ 6. The extractable solids contained more epistructured catechins at pHs 3–5 but more non-epistructured catechins at pHs 6–7. More tea cream was obtained at pH 1 but the concentration of catechins, caffeine and theanine was low in this fraction. Therefore, to maximize the extraction of the epistructured catechins and to minimize their epimerization and degradation and to maximize the extraction of caffeine and theanine, the results suggest that the pH should be maintained between 3 and 5.3 during the aqueous brewing process.     

Conformational changes and dynamic rheological properties of fish sarcoplasmic proteins treated at various pHs

The conformational changes and rheological properties of soluble sarcoplasmic proteins isolated from striped catfish (Pangasius hypophthalmus), treated at various pHs (2–12), were investigated. Isoelectric point of striped catfish sarcoplasmic proteins was determined to be pH 5. SDS–PAGE of sarcoplasmic proteins treated at various pHs, showed molecular masses ranging from 11 to 97 kDa. Most sarcoplasmic proteins, regardless of treated pHs, showed a molecular mass of 43 kDa. A decrease in total sulfhydryl content was observed when the pH was shifted away from 6, indicating disulfide formation at pH lower and higher than 6. Gradual increases of S₀-ANS and S₀-PRODAN were observed as pH increased from 6 to 12, indicating the unfolding of sarcoplasmic proteins during alkaline extraction. DSC thermograms of sarcoplasmic proteins treated at pH 5–9 exhibited an exothermic transition peak, probably due to disulfide bond formation, and/or hydrophobic interactions, which was highly related to the onset temperature of G′ rising. Gel network formation of sarcoplasmic proteins did not take place at extreme pHs (<4 or >9) where proteins were highly charged while the viscoelastic properties of sarcoplasmic proteins were observed at pH 5.5–9. The highest G′ value at 90 °C was observed at pH 5.5 and 8 (P ? 0.05). The gel point, a temperature at which G′ = G″, increased to higher temperature as pH was shifted away from 7.     

RECOVERY OF PALM CAROTENE FROM PALM OIL AND HYDROLYZED PALM OIL BY ADSORPTION COLUMN CHROMATOGRAPHY

Crude palm oil and crude palm olein were hydrolyzed with lipase from Candida rugosa to produce a free fatty acid (FFA) rich oil. The percentages of FFA produced and carotene degradation after the hydrolysis process were determined. The palm oil and hydrolyzed palm oil were subsequently subjected to column chromatography. Diaion HP-20 adsorbent was used for reverse phase column chromatography at 50C. Isopropanol or ethanol, and n-hexane were used as the first and second eluting solvents, respectively. The objective of hydrolyzing the palm oil was to produce more polar FFA-rich oil in order to enhance the nonpolar carotene bind to the nonpolar HP-20 adsorbent in the column chromatography process. Hydrolyzing palm oil with lipase from Candida rugosa gave 30- and 60-fold, respectively, of FFA in the crude palm oil and crude palm olein in 24 h at 50C. Approximately, 15.56 and 17.48% of carotene degraded in crude palm oil and crude palm olein, respectively. For column chromatography, using isopropanol or ethanol as the first eluting solvent, unhydrolyzed oil and hydrolyzed oil showed the carotene recovery infraction two (carotene-rich fraction) of about 36–37 and 90–96%, respectively. Over 90% of carotene recovery was obtained from     

Muscadine Grape Polyphenoloxidase: Partial Purification by High Pressure Liquid Chromatography and Some Properties

A rapid method of isolating grape polyphenoloxidase (PPO) was developed, using two muscadine cultivars, “Noble” and “Welder”. PPO extracts from acetone powders were partially purified followed by filtration through 0.2μ membrane filter by HPLC. Reactivity of the active fraction per unit protein, increased 10-fold for Noble and 33-fold for Welder cultivars over values for the corresponding crude extracts. Electrophoretic analysis and activity stain showed that the enzyme displayed a single band in Welder and two bands for Noble. Optimum pH for PPO activity in Welder was pH 4.5 while that for Noble was pH 4.5–5.5. The enzyme in the Noble cultivar was relatively more active at alkaline pH. Activites of the enzymes were stable at temperatures up to 30°C for both cultivars.     

Combined effects of NaCl, NaOH, and biocides (monolaurin or lauric acid) on inactivation of Listeria monocytogenes and Pseudomonas spp

This study highlighted combinations of chemical stresses that could decrease or eliminate Listeria monocytogenes and Pseudomonas spp. surviving in food processing plants. Strains of L. monocytogenes, Pseudomonas fragi, and Pseudomonas fluorescens isolated from processing environments (meat and milk) were grown at 20 degrees C up to the early stationary phase. The strains were then subjected to 30 min of physicochemical treatments. These treatments included individual or combined acid (acetic acid), alkaline (NaOH), osmotic (NaCl), and biocides (fatty acids) challenges. Survival of the strains was studied after individual or combined acid (acetic acid), alkaline (NaOH), osmotic (NaCl), and biocides (monolaurin, lauric acid) challenges. Individual pH shocks had lower efficiencies than those used in combinations with other parameters. The treatment pH 5.4 followed by pH 10.5 had a low efficiency against L. monocytogenes. The opposite combination, pH 10.5 followed by pH 5.4, led to a 3-log reduction of the L. monocytogenes population. Pseudomonas spp. strains were much more sensitive than L. monocytogenes, and population reductions of 5 and 8 log (total destruction), respectively, were observed after the same treatments. As for L. monocytogenes, the combination pH 10.5 followed by pH 5.4 is more deleterious than the opposite. Whatever the bacterial species, the most efficient treatments were combinations of alkaline, osmotic, and biocide shocks. For instance, the combination pH 10.5 and 10% NaCl plus biocides showed reductions of 5 to 8 log for both bacteria. The origins of the observed lethal effects are discussed.     

蛋清肽的抗氧化稳定性与功能特性

选用胃蛋白酶水解冻干蛋清制得蛋清肽,测定蛋清肽的抗氧化稳定性及功能特性。研究温度和pH值对蛋清肽抗氧化稳定性的影响以及蛋清肽的乳化性、吸水能力和吸油能力。结果表明：随着蛋清肽质量浓度的增加其清除羟自由基( ·OH)、超氧阴离子自由基(O2－ ·)及DPPH自由基的能力均随之增加;温度与pH值对蛋清肽的抗氧化活性影响较大,在pH12.0条件下存放4h后其抗氧化活性消失;蛋清肽具有较好的乳化能力、乳化稳定性、吸油和吸水能力,这些均有利于其在食品和化妆品行业中的应用。     

Inhibition of proliferation of human carcinoma cell lines by phenolic compounds from a bearberry-leaf crude extract and its fractions

Phenolic compounds were extracted from the leaves of bearberry, a potential functional food ingredient, using 80% (v/v) aqueous ethanol after which the resultant crude extract was applied to a Sephadex LH-20 column. A fraction comprising low-molecular-weight phenolics (LMW fraction) and sugars was eluted from the column with 95% (v/v) ethanol. A tannin fraction was then obtained after switching the mobile phase to acetone/water (1:1, v/v). Phenolic compounds present in the crude extract and its two fractions showed antiproliferative activities in a concentration-dependent manner against five carcinoma cell lines, namely MCF-7 (estrogen receptor-positive breast carcinoma), DU-145 (androgen receptor-negative prostate carcinoma), HT-29 (colon carcinoma), SK-MEL-5 and MDA-MB-435 (melanoma; skin carcinoma). IC₅₀ data revealed that the tannin fraction was best at retarding cell proliferation in the tested cancer cell lines. The greatest inhibition at 1.5 μg fraction/mL assay was observed for the HT-29 colon carcinoma cell line. The proliferation of SK-MEL-5 skin carcinoma cells was also strongly inhibited by both the crude extract and LMW fraction. MDA-MB-435 cells were found to be the least sensitive for the materials tested, particularly for the LMW fraction.