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.     

Ultrasonic spectroscopy study of relaxation and scattering in whey protein solutions

Ultrasonic attenuation spectroscopy was used to investigate the influence of pH on fast chemical reactions and aggregation of whey proteins in aqueous solution. Ultrasonic attenuation spectra (1–100 MHz) of 2.5 wt% aqueous solutions containing either ‘native’ or ‘alkali-denatured’ proteins were measured as a function of pH (2–12). Peaks in the attenuation occurred at pH 2.8 and 11.6 due to proton transfer equilibria, ie  CO₂H ↔  CO₂⁻ + H⁺ and  NH₂ + H⁺ ↔  NH₃⁺ respectively. Attenuation at other pH values was attributed to a hydration relaxation mechanism. Relaxation times for the equilibria were of the order of 10⁻⁸ s. There was an additional attenuation peak at the isoelectric point of the proteins (pH 5) for solutions containing ‘alkali-denatured’ protein, which was due to scattering of ultrasound by aggregated proteins. The particle size distribution of the aggregates could be determined using ultrasonic scattering theory to analyse the attenuation spectra. Ultrasonic spectroscopy is an extremely valuable tool for probing the molecular characteristics of proteins in solution. © 1999 Society of Chemical Industry     

Influence of sucrose on cold gelation of heat‐denatured whey protein isolate

A solution of heat‐denatured whey proteins was prepared by heating 100 g kg⁻¹ whey protein isolate (WPI) at pH 7.0 to 75 °C for 15 min in the absence of salt. Heat treatment caused the globular protein molecules to unfold, but electrostatic repulsion opposed strong protein–protein aggregation and so prevented gel formation. When the heat‐denatured whey protein solution was cooled to room temperature and mixed with 15 mM CaCl₂, it formed a gel. We investigated the influence of the presence of sucrose in the protein solutions prior to CaCl₂ addition on the gelation rate. At relatively low concentrations (0–100 g kg⁻¹), sucrose decreased the gelation rate, presumably because sucrose increased the aqueous phase viscosity. At higher concentrations (100–300 g kg⁻¹), sucrose decreased the gelation rate, probably because sugar competes for the water of hydration and therefore increases the attraction between proteins. These data have important implications for the application of cold‐setting WPI ingredients in sweetened food products such as desserts. © 2000 Society of Chemical Industry     

Antimicrobial Effects of Pressured Carbon Dioxide in a Continuous Flow System

The application of microbubbles of pressured CO₂ greatly increased CO₂ concentration in the solution treated. By treatment at 6 MPa, 35°C and average residence time 15 min, L. brevis was completely inactivated at the level of dissolved CO₂,γ≧ 11 (γ, Kuenen's gas absorption coefficient). E. coli and S. cerevisiae required γ≧ 17, and T. versatilis required γ≧ 21 for complete inactivation. Z. rouxii could be sterilized at 20 MPa and 26. A comparison of the continuous and batch method showed that L. brevis was inactivated completely under pressured CO₂ > 0.16 g/cm³ with the continuous method and >0.9 g/cm³ with the batch method.     

ISOLATION AND GENERAL PROPERTIES OF LECTINS FROM THE BEAN (PHASEOLUS VALGARIS VAR. ROSINHA G2)

A purified lectin was prepared from 0.15 M NaCl extracts of bean (Phaseolus vulgaris var. Rosinha G2) by affinity chromatography on ConA-Sepharose followed by gel chromatography on Sephadex G-200. The haemagglutining material isolated by affinity chromatography (CII-Af) contained at least three active protein bands as shown by polyacrylamide gel electrophoresis. By chromatography on a Sephadex G-200 column, the (CII-Af) fraction gave only a major peak (CII-β) with haemagglutininating activity, which showed a single broad band on gel electrophoresis. Gel isoelectric focusing of the CII-β component gave a single active band in the pH range of 5.5–5.7. The purified lectin was a glycoprotein, containing 8.30% of neutral sugars (as mannose) and 2.12% of hexosamine (as glucosamine) and only trace amounts of sulphur-containing amino acids. The protein had a MW of 136,000 (6.9 S) with a Stokes radius of 43 Å, a calculated diffusion constant (D_20,w) of 5 times 10^?7 cm² s^?1, and a partial specific volume (v) of 0.75 ml.g^?1. From its frictional ratio f/fo = 1.3 and assuming a hydration capacity of 0.3 to 0.4 g of water/g of protein, the axial ratio for the lectin molecule would be in the range of 3–4 if a prolate ellipsoid of revolution is chosen as a model.     

Effect of cyclodextrins on the thermodynamic and kinetic properties of cyanidin-3-O-glucoside

In this study, the effect of α and β-cyclodextrin on cyanidin-3-O-glucoside color was investigated by UV–visible absorption techniques. The equilibrium and kinetic constants of the network of chemical reactions taking place in cyanidin-3-O-glucoside were also studied in water at 25 °C by UV–visible absorption techniques. The results showed that the addition of β-cyclodextrin resulted in the fading of anthocyanin solution, and this fading effect was greater at higher pH. This anti-copigmentation effect is caused by the selective inclusion and stabilization of the anthocyanin colorless forms into the β-cyclodextrin cavity. Oppositely, no changes were observed in the cyanidin-3-O-glucoside absorption spectra with the addition of α-cyclodextrin.Direct pH jump, from thermally equilibrated solutions at pH = 1.0 (flavylium cation, AH⁺), shows three kinetic processes: formation of the base A, hydration reaction to form the hemiketal B and the chalcone cis–trans isomerization (Cc–Ct). The results obtained clearly indicated that the equilibrium and kinetic constants of the network of chemical reactions taking place in cyanidin-3-O-glucoside were affected by the presence of β-cyclodextrin. Molecular inclusion in the β-cyclodextrin cavity resulted in the increase of the isomerization observed rate constant (k_obs) at pH 5.3 and in the increase of the hydration equilibrium constant K_h which is in agreement with the fading of the anthocyanin solution. For the macrocycle α-cyclodextrin, no significant changes were observed on the equilibrium and kinetic constants, which suggests that the inclusion of cyanidin-3-glucoside in the α-cyclodextrin's cavity is not favored.     

Characterising protein,salt and water interactions with combined vibrational spectroscopic techniques

In this paper a combination of NIR spectroscopy and FTIR and Raman microspectroscopy was used to elucidate the effects of different salts (NaCl, KCl and MgSO₄) on structural proteins and their hydration in muscle tissue. Multivariate multi-block technique Consensus Principal Component Analysis enabled integration of different vibrational spectroscopic techniques: macroscopic information obtained by NIR spectroscopy is directly related to microscopic information obtained by FTIR and Raman microspectroscopy. Changes in protein secondary structure observed at different concentrations of salts were linked to changes in protein hydration affinity. The evidence for this was given by connecting the underlying FTIR bands of the amide I region (1700–1600 cm⁻¹) and the water region (3500–3000 cm⁻¹) with water vibrations obtained by NIR spectroscopy. In addition, Raman microspectroscopy demonstrated that different cations affected structures of aromatic amino acid residues differently, which indicates that cation–π interactions play an important role in determination of the final structure of protein molecules.     

HYDRATION KINETICS OF LUPIN (LUPINUS ALBUS) SEEDS

The hydration kinetics of lupin (Lupinus albus) seeds was studied by soaking in water at temperatures of 20, 30, 40 and 50C (±1C) in constant‐temperature water bath for 9 to 12 h. The weight gain due to the hydration process was determined in terms of moisture content (% dry basis). Water absorption rate was high at the early stage of hydration (20–60 min depending on temperature) followed by a decreased rate and finally approaching equilibrium condition. Peleg's equation adequately described the hydration characteristics of lupin seeds under the experimental condition (R² = 0.96 to 0.99). The Peleg rate constant k₁ decreased from 2.537 to 0.241 min/%, while Peleg capacity constant k₂ increased from 0.0036 to 0.0070/% significantly (P < 0.05) with an increase in temperature from 20 to 50C, demonstrating that the water absorption rate increased and water absorption capacity decreased with increase in temperature. The temperature dependence of k₁ and k₂ was described by Arrhenius type equation with R² values of 0.98 and 0.97, respectively, and activation energy of 60.44 kJ/mol. The agreement between experimental and estimated values of the hydration data (R² = 0.97 to 0.99) confirmed that Peleg's equation could be used to describe the hydration characteristics of lupin seeds under the experimental conditions considered.     

The effects of ultrasonic/microwave assisted treatment on the properties of soy protein isolate/titanium dioxide films

Soy protein isolate (SPI, 5.0 g/100 mL,) films embedded with nano-TiO₂ (0, 0.5, 1.0, 1.5 and 2.0 g/100 mL) were prepared by solution casting and modified by ultrasonic/microwave assisted treatment (UMAT). The effects of nano-TiO₂ content and UMAT time on the films' physical properties and structure were investigated. Incorporation of nano-TiO₂ significantly enhanced films' mechanical properties and barrier properties, because of the intermolecular force between nano-TiO₂ and SPI. UMAT time ≤20 min obviously improved films' tensile strength values (15.77 MPa, 245% higher than the control), and reduced water vapor permeability (1.8457 × 10⁻¹¹ g cm⁻¹ s⁻¹ Pa⁻¹, 72.11% lower than the control) and oxygen permeability values (0.8897 × 10⁻⁵ cm³ m⁻² d⁻¹ Pa⁻¹, 57.66% lower than the control). SEM images also revealed a more compact and dense structure of films when UMAT time ≤20 min. Films' water adsorption properties were evaluated. GAB and Henderson models exhibited the best to fit experimental data, thus it was predicted that films (1.5 g nano-TiO₂/100 ml) could be stable at low moisture content (0.27 kg of water/kg dry mass).     

Integral utilisation of barley husk for the production of food additives

A new and effective chemical–biotechnological process for the global utilisation of barley husk (obtained from the spent grains in the brewing process) is reported. With the proposed process the three main components of the lignocellulosic residue (cellulose, hemicellulose and lignin) are utilised. A first treatment with sulfuric acid (pre‐hydrolysis) allowed the solubilisation of hemicelluloses to give xylose and glucose‐containing liquors (suitable to make fermentation media for the continuous lactic acid (LA) production with L. pentosus) and a solid phase containing cellulose and lignin. In this set of experiments, a maximum volumetric productivity (Q_P) = 2.077 g L^?1 h^?1 and product yield (Y_P/S) = 0.62 g g^?1 were obtained for a dilution rate of 0.01 h^?1. The solid residues from pre‐hydrolysis were treated with NaOH in order to increase their cellulase digestibility, and dissolve the lignin content. The cellulose residue was used as substrates for lactic acid production by simultaneous saccharification and fermentation (SSF) in media containing Trichoderma reesei cellulases and Lactobacillus rhamnosus cells using the complete MRS broth or a cheaper medium. In both cases similar LA concentrations and volumetric productivities were achieved (P = 73.4–71.0 g L^?1 and Q_P = 1.28–1.25 g L^?1 h^?1, respectively), where P is LA concentration. The lignin solution obtained after the alkaline treatment was extracted with ethyl acetate in order to obtain the phenolic components. The extract obtained at pH 3 showed three times more antioxidant activity than the one extracted at pH 12.8, with an EC₅₀ of 1.396 g L^?1 for pH 3 and 4.604 g L^?1 for pH 12.8. The best extracts showed twice antioxidant activity than BHT. Copyright © 2007 Society of Chemical Industry     

Inactivation Kinetics of Lactobacillus plantarum by High Pressure Carbon Dioxide

Inactivation kinetics of Lactobacillus plantarum by high pressure CO₂ was investigated to understand the mechanism of microbial inactivation. The inactivation rates increased with pressure, temperature and exposure time, and with decreasing pH of media. Microbial inactivation was governed essentially by penetration of CO₂ into cells and its effectiveness could be improved by the enhanced transfer rate. Microbial reduction of 8 log cycles was observed within 120 min under CO₂ pressure of 70 kg/cm² at 30°C. We hypothesized that the cell death resulted from the lowered intracellular pH and damage to the cell membrane due to penetration of CO₂. Pressurized CO₂ treatment is a potential nonthermal technology for food preservation.     

AN ASSESSMENT OF CHEMICAL SANITIZERS ON THE MICROBIOLOGICAL PROFILE OF AIR IN A MILK PROCESSING PLANT

The efficiency of chemical sanitizing agents to control the microbiota of milk processing areas at a dairy plant was evaluated. Diluted solutions of chlorhexidine digluconate at 1,000 and 2,000 mg.L^?1, pH = 5.2 and 5.3, respectively; peracetic acid, at 45 and 75 mg.L^?1, pH = 4.2 and 3.8; and a quaternary ammonium compound, pH = 9.2 and 9.3, respectively, were pulverized, at ambient temperature (20–25C) in the milk processing areas using spray equipment which produced a consistent fogging. For each 30 m² of processing area, 0.5 L of sanitizer solutions were applied at 9 Kgf.cm^?2 in 10 min. The sanitizer's efficiency was evaluated against mesophilic aerobic bacteria and yeast and molds. The microbial counts (APC) in the processing areas were detected by impaction technique, as proposed by APHA. Analysis were done before sanitizer application (T₀) and after 0.5, 12 and 24 h (T₁, T₂ and T₃), respectively. Activity of 2000 mg.L^?1 of chlorhexidine and 700 mg.L^?1 of quaternary ammonium against yeast and molds was observed. The T₀ number of microorganisms (1.5 and 1.3 log cfu.m^?3) decreased in 0.45 and 0.5 log cycle, respectively. Solutions containing 45 mg.L^?1 of peracetic acid were effective to control mesophilic aerobic microorganisms. The T₀ number of microorganisms (2.1 log cfu.m^?3) decreased in 0.55 log cycle. Residual effects against yeasts and molds were observed for 1000 mg.L^?1 of chlorhexidine digluconate and 75 mg.L^?1 of peracetic acid. Chemical sanitizer applications to control the microbiological quality of the air in milk processing areas is a barrier technology that helps in the production of foods with good microbiological, sensory and organoleptic characteristics.     

Synthesis and Optimization of the Reaction Conditions of Starch Sulfates in Aqueous Solution

Starch sulfate was prepared by chemical modification of potato starch with trisulfonated sodium amine (N(SO₃Na)₃), which was synthesized by reaction of sodium bisulfite and sodium nitrite in aqueous solution. The factors that could affect the degree of substitution (DS) of potato starch were investigated in detail, which included reaction temperature and time of preparing the sulfating agent, reaction temperature and time of synthesizing the starch sulfate, dosage of sulfating agent and potato starch, pH of sulfation reaction medium, and the ratio of liquid volume to starch mass. A starch sulfate with DS of 2.14 was obtained under optimal conditions. FTIR spectra showed the characteristic absorptions of sulfate ester bonds at 1236 cm⁻¹ and 821 cm⁻¹.     

Rheological properties of African yam bean (Sphenostylis stenocarpa Hochst. Ex A. Rich.) calcium proteinate and isoelectric protein isolates

The rheological characterizations of African yam bean (Sphenostylis stenocarpa) protein dispersions were investigated. Isoelectrically precipitated protein-IP_alk and IP_salt isolates obtained from alkaline and salt extractions respectively were more soluble than calcium precipitated proteins (CaP_alk and CaP_salt) at pH 3, 7 and 8. Regression analysis showed that Power law, Casson and Bingham rheological models adequately described rheological behaviors of S. stenocarpa protein dispersion. However, Power law gave the best fit. The flow behavior indices (n), at different ionic strength, pH, and temperature media were less than unity, indicating that S. stenocarpa protein dispersion exhibited pseudoplastic behaviors under the conditions tested. Salt extracted proteins were more pseudoplastic than alkali extracted counterpart with n for salt extracted proteins (IP_salt & CaP_salt) lower than that of alkali extracted protein (CaP_alk & CaP_salt). This is a numerical indication that salt extracted S. stenocarpa proteins were of larger shear-thinning tendency than the alkali extracted proteins. The consistency coefficients, k of isoelectrically precipitated protein (0.305-0.327 Pasⁿ) were significantly (P < 0.05) higher than that of calcium proteinates in the range ranged 0.167-0.180 Pasⁿ. Both isoelectrically precipitated proteins and calcium proteinates exhibited yield stress, however, isoelectrically precipitated S. stenocarpa protein exhibited significantly (P < 0.05) higher yield stress (0.275-0.308 Pa) than the calcium proteinates (0.148-0.165 Pa). The effect of temperature on apparent viscosity of the proteins was evaluated using an Arrhenius-type equation. The activation energies (E_a) obtained were in the range 33-51.2 and 42.6-55.5 Jmol⁻¹ for calcium proteinate and isoelectrically precipitated protein respectively.     

Xanthan gum produced by Xanthomonas campestris from cheese whey: production optimisation and rheological characterisation

BACKGROUND: This aim of this study was the production and rheological characterisation of xanthan gum by Xanthomonas campestris pv. mangiferaeindicae IBSBF 1230 using industrial media and experimental design techniques in a bench bioreactor. RESULTS: The optimised conditions for the production of xanthan starting with 900 mL of cheese whey were 1 g L^?1 magnesium sulphate, 20 g L^?1 potassium phosphate, 28 °C temperature and initial pH 7.2 at 390 rpm agitation and 1.5 vvm aeration, resulting in 36 g L^?1 gum in 72 h. The highest viscosity obtained in the production optimisation study was 1831.34 mPa s at 25 °C with 30 g L^?1 gum. The use of CaCl₂ resulted in the highest solution viscosity under conditions of 25 °C, 1 g L^?1 salt and 46.8 g L^?1 gum, with a value of 1704.53 mPa s. CONCLUSION: In this study, cheese whey, a by‐product of the dairy industry, was used as substrate in the production of xanthan gum, a valuable product in food applications, with optimised high gum production in a bioreactor and a wide range of viscosity values. Copyright © 2009 Society of Chemical Industry     

The contamination of milk with iodine from iodophors used in milking machine sanitation

The retention and release of iodophor-derived iodine from milking machine materials was studied using ¹³¹I-labelled iodophor and small tubes of materials used in the construction of milking machines. After one hour's exposure to this iodophor, plastic retained 56% of the ¹³¹I label, followed by silicone rubber (31%), rubber (18%), steel (2%) and glass (0.5%). Water rinsing after exposure to iodophor reduced these values to 49%, 26%, 14%, 0.5% and 0.3% respectively. When the tubes were exposed to the iodophor and subsequently rinsed with milk, rubber released the largest amount of iodine into milk (0.099 μg I cm^?2), followed by silicone (0.038 μg I cm^?2), plastic (0.010 μg I cm^?2), glass (0.009 μg I cm^?2) and steel (0.002 μg I cm^?2). The contact time of iodophor with a particular material influenced both the amount of iodine adsorbed, and the amount subsequently released into milk. The importance of iodine adsorption and desorption phenomena in contributing iodine to milk was compared to that iodine in milk arising from inadequate drainage of iodophor solution from a milking machine, and found to be comparable in magnitude.     

Assessment of Different Packaging Structures in the Stability of Frozen Fresh Brazilian Toscana Sausage

The aim of this work was to evaluate the effect of different package conditions on the characteristics of Toscana fresh sausage stored for 150?days under freezing. The analyses of lipid oxidation, moisture, pH, acidity, water activity, and counting of psychotrophic microorganisms were carried out along with the storage time for each package (low-density polyethylene with and without vacuum and oxygen permeability of 500?cm³ O₂/m² day atm at 23 ??C; nylon polyester with and without vacuum and permeability of 100?cm³ O₂/m² day atm at 23 ??C; and formal copolymer of ethylene and vinyl alcohol with and without vacuum and oxygen permeability of 5?cm³ O₂/m² day atm at 23 ??C). Results showed that from 60?days of storage, the samples stored using polyethylene without vacuum and nylon 100?cm³ O₂/m² day atm, without vacuum, presented a slight rancidity flavor, statistically different (p?<?0.05) from the other tested ones. After 151?days of storage, a relationship between 2-thiobarbituric acid reactive substances analysis and sensory characteristics could be observed. In this case, the packages without application of vacuum presented higher values in the sensory and oxidative rancidity analyses, configuring flavor of slight to moderate rancidity.     

Sorbic Acid and Potassium Sorbate Permeability of an Edible Methylcellulose-Palmitic Acid Film: Water Activity and pH Effects

The apparent permeability constants for potassium sorbate and sorbic acid through an edible film composed of methylcellulose and palmitic acid (weight ratio 3:1) were evaluated as a function of water activity (a_w) and pH. For films with thickness 55–66 μm, potassium sorbate permeability increased from 2.3 × 10^?10 to 2.0 × 10^?8 (mg/sec cm²)(cm)/(mg/mL) as a_w increased from 0.65 to 0.80. Films were not stable at a_w levels above 0.80. Permeability of the film to sorbic acid at a_w 0.8 decreased from 3.3 × 10^?8 to 9.1 × 10^?10 (mg/sec cm²)(cm)/ (mg/mL) as pH increased from 3 to 7. At pH 3 the undissociated acid was 97.5% and at pH 7 it was 0.4%.     

Low‐ and Medium‐DE Maltodextrins From Waxy Wheat Starch: Preparation and Properties

The goal of the research was to prepare maltodextrins (MD) from waxy wheat starch and waxy corn starch (control). Waxy wheat starches with 0.2% protein, 0.2% lipid and ∼1% amylose were isolated from two flours by mixing a dough, dispersing the dough in excess water, and separating the starch and gluten from the resultant dispersion. The mean recoveries were 72% for the starches and 76% for the gluten fraction with 80% protein. Maltodextrins having low‐dextrose equivalence (DE) 1—2 and mid‐DE 9—10 were prepared by treatment of 15% slurries of waxy wheat starch and waxy corn starch at 95 °C for 5—10 min and 20—50 min, respectively, with a heat‐stable α‐amylase. Denaturing the enzyme and spray‐drying produced MD's with bulk densities of 0.3 g/cm ³. The powdery MD's were subjected to an accelerated‐rancidity development test at 60 °C, and an off‐odor was detected after 2 days storage for the low‐DE MD's from the two waxy wheat starches (WxWS₁‐MD 1.2 and WxWS₂‐MD 1.5), but not for the low‐DE waxy corn maltodextrin (WxCS‐MD 2.2) or a commercial waxy corn MD with DE 1. None of the mid‐DE 9—10 MD's developed off‐odor after 30 days storage at 60 °C. The experimental products WxWS₁‐MD 9.2, WxWS₂‐MD 9.9 and WxCS‐MD 9.1 showed high water‐solubility and gave 1—10% aqueous solutions of high clarity with no clouding upon cooling.     

Physicochemical Properties of Milk Fat Emulsions Stabilized with Bovine Milk Fat Globule Membrane

Milk fat globules (MFG) were reconstituted with milk fat globule membrane (MFGM) and milk fat (MF). Viscosity of the reconstituted MFG was highest at pH 5.0 and 4 min emulsifying, and rose with an increase of MFGM between 40–80 mg/g fat. Adsorbed protein/unit fat increased at acid pH with increase of MFGM. The composition of proteins adsorbed on the surface of MFG was not influenced by factors of reconstitution. The size and specific surface area of globules were influenced by emulsifying time, MFGM and MF concentrations, and pH. The size range of MFG prepared by standard method was 0.9–17 μm in diameter. Median diameter was 5 μm and specific surface area was 15,600 cm²/cm³ of emulsion.