Surface tension and foam stability of commercial calcium and sodium caseinates

The static and dynamic surface tension of sodium and calcium caseinates was compared with their foam behavior. The surface tension behavior of sodium and calcium caseinates was similar but the foaming properties differed. Caseinates presented moderate surface activity lowering the surface tension of water to 40 mN/m. The surface pressure vs. composition data were analyzed using a new surface equation of state and obtained 0.1% (w/v) critical concentration and the molecular surface area; in the case of calcium caseinate was larger compared to sodium caseinate. Caseinates were evaluated at the critical concentration by means of dynamic surface tension to compare their behavior; calcium caseinate took longer time to reach equilibrium conditions. Their foam behavior was transient type with maximum foamability around the critical concentration; sodium caseinate presented better foaming properties than calcium caseinate.     

Application of capillary electrophoresis to the characterization of processed cheeses

Capillary electrophoresis using a hydrophilically coated capillary and a low pH buffer containing urea has been used to characterize processed cheeses. Different electrophoretic patterns were obtained depending on the ingredients used in the blend such as acid casein, rennet casein, sodium and calcium caseinates and skim milk powder. Isoelectric casein, and sodium and calcium caseinates were shown to contain intact non-glycosylated kappa-casein (kappa-CN), while rennet casein contained only trace amounts of kappa-CN and mainly para-kappa-CN. Therefore, the addition of casein or caseinate to processed cheeses has been detected by analysing the intact non-glycosylated kappa-CN. Quantitation of intact non-glycosylated kappa-CN in processed cheeses of known and unknown composition was carried out using a regression curve from standard mixtures of 150-550 g isoelectric casein/kg total rennet casein. This capillary electrophoresis method successfully confirmed the addition of isoelectric casein or caseinate to processed cheeses of known composition. The quantitative determination range was 0.605-3.688 mg kappa-CN/ml. This method cannot be used for measuring additions of rennet casein or any caseinates that have been exposed to chymosin.     

Effect of calcium and sodium caseinates on physical characteristics of soy protein isolate–lipid films

The effect of addition of caseinates to soy protein isolated (SPI) based films containing lipids (33% of oleic acid or 85:15 oleic acid (OA)–beeswax blend (BW)) on water vapour permeability (WVP), mechanical and optical properties was evaluated. SPI–lipids was combined with caseinates (sodium or calcium) in different SPI:caseinate ratios with the aim of improving water vapour barrier, mechanical and optical properties of SPI films containing lipids. Caseinate incorporation to SPI based films provoked an increase of elastic modulus and tensile strength at break, mainly for calcium caseinate. Both caseinates contributed to increase the water vapour barrier properties of soy protein-based films. Caseinates also provoked an increase of transparency of SPI based films and colour softening. The most effective combination was 1:1 sodium caseinate:SPI ratio, when film contains 85:15 oleic acid:beeswax ratio.     

A GC-FID method for analysis of lysinoalanine

Lysinoalanine (LAL) is an unwanted byproduct, which is formed during the processing of protein and protein-containing foods and feeds. A GC method for the quantitative analysis of LAL under conventional chromatographic conditions has been developed. The method was applied to the analysis of pure standard substances, boiled eggs, commercial caseinates, fresh cheese, fresh cheese made from milk supplemented with caseinate, and fresh cheeses adulterated with caseinate after cheese making process. Results demonstrated the reliability of the GC capillary chromatography for the analysis of LAL in protein containing foods. LOD and LOQ of 50 and 152 ppm of LAL in protein, respectively, were achieved. Range of linearity, precision, and accuracy of the method, measured using diaminopimelic acid as internal standard, were satisfactory for quantification purpose. The method might also be suitable for the quantitative analysis of other amino acids such as lysine and arginine. Results also indicated the utility of this methodology for detecting protein quality of egg products and caseinates as well as fresh cheese adulterations.     

Heat-induced changes in the calcium sensitivity of caseins

The calcium sensitivity of Na caseinate prepared from a serum protein-free casein micelle dispersion in synthetic milk ultrafiltrate, containing 4.8%, w/v, lactose and 5 mmol L⁻¹ urea and heated at 130°C for 0–25 min decreased with heating. It is proposed that an increase in the net negative charge of the caseinates, due to heat-induced degradation of lysine and arginine, is responsible for the enhanced calcium stability of heated caseins. The Maillard reaction and urea–protein interactions appear to play an important role in the increased stability of heated caseinate towards calcium. The effect of protein charge on the heat stability of milk protein systems (Na caseinate 2.5%, w/v, protein in milk ultrafiltrate) at 140°C was investigated by chemical modification of the caseinate prior to assessment of heat stability. Heat stability increased with the modification of lysine, arginine and carboxyl residues. The increased heat stability of Na caseinate with modified lysine and arginine residues may be due to an increase in the net negative charge on the caseinate, while the increased stability of caseinate with modified carboxyl residues may be related to a reduction in heat-induced crosslinking of protein.     

Effect of sodium caseinate on the stability of cream liqueurs

The apparent viscosity of cream liqueurs prepared with different commercial sodium caseinates increased on storage at 45°C at rates and to extents that were dependent on which caseinate was used in the cream liqueur preparation. Increases in the apparent viscosity of fat free and fat free, micellar casein and whey protein free liqueurs indicated that differences in the caseinate s per se, rather than differences in interfacial absorption of the caseinates or the inclusion of micellar casein and whey proteins with the cream serum, caused the differences in increases in the apparent viscosity of cream liqueurs on storage at 45°C. No significant correlation was found between the calcium content of the caseinates and increases in the apparent viscosity of the liqueur systems on storage at 45°C. Addition of 2-mercaptoethanol to liqueurs after manufacture caused large increases in apparent viscosity, indicating that sulphydryl interactions may be important. Addition of NaCl to cream liqueurs resulted in an immediate increase in apparent viscosity, and on storage at 45°C for seven days, the liqueurs gelled, developed a high apparent viscosity or underwent phase separation, depending on which caseinate was used in the manufacture of the cream liqueur. Thus changes in the apparent viscosity of cream liqueurs on storage at 45°C are caseinate dependent and the results presented suggest that electrostatic and sulphydryl interactions may be involved in these changes.     

Stability of caseinate solutions in the presence of calcium

The presence of calcium ions in aqueous solutions of bovine caseinate leads to the formation of large aggregates that precipitate after centrifugation. The residual fraction of soluble casein in the supernatant was measured as a function of the calcium concentration and the total caseinate content. It was found to be determined by the calcium concentration independent of the caseinate concentration. The soluble casein was characterized using light scattering and consisted of small aggregates with a radius of about 12 nm containing about 15 casein molecules. The composition of the soluble casein was determined with chromatography and was increasingly poor in α_s1-casein with increasing calcium content. The solubility of calcium caseinate was determined and related to the total calcium ion concentration.     

Quantitative detection of lactic acid bacteria in dried sourdoughs using real-time PCR

A real-time PCR system with 16S rRNA gene-targeted group-specific primers was developed to quantitatively detect lactic acid bacteria (LAB) of the genera Lactobacillus, Leuconostoc, Pediococcus, and Weissella in different types of commercially available dried sourdoughs. Despite a high degree of degradation in the DNA isolated from the doughs, the 341-bp 16S rRNA gene fragment of the sourdough LAB biota could specifically be amplified. For dried sourdoughs, the resulting calculated LAB cell counts were determined to be up to 3.7 × 10⁷ cells/g fresh dough, whereas in non-fermented dough acidifiers, used as a control, the calculated LAB cell counts did not exceed 3.6 × 10⁴ cells/g fresh dough. Moreover, the effect of low pH and/or high lactic acid concentrations prevailing in the doughs on the detectability of LAB cells in spray- and roller-dried sourdoughs by PCR was investigated. Drying of non-acidified sourdoughs still permitted to detect the LAB cells by PCR, whereas drying of acidified doughs reduced the detectable cell counts by approximately 5 (spray dried) and 2 (roller dried) orders of magnitudes. Incubation of acidified doughs for 24 h did not affect the detectability of LAB cells in spray-dried doughs but further reduced the detectable cell counts in roller-dried doughs by additional 2 orders of magnitude.     

Effect of Edible Coating Process and Irradiation Treatment of Strawberry fragaria spp. on Storage-keeping Quality

ABSTRACT: Gamma-irradiation and various edible coatings were tested on fresh strawberries ( Fragaria spp. ) for keeping fruit quality and extending shelf life. Four coatings based on milk protein were evaluated. In 1 experiment, coating formulation based on caseinate and/or strawberries were irradiated using a ⁶⁰Co source. Both gamma-irradiation treatment and edible coating process significantly delayed (p ≤ 0.05) molds growth. Edible coating based on irradiated caseinate was more effective than that of unirradiated caseinate. In a 2nd experiment, 3 irradiated coatings based on calcium caseinate and whey proteins were evaluated. The coating formulation based on 1:1 caseinate-whey was found to be more effective than those based on calcium caseinate. Addition of calcium chloride or a mixture of pectin and agar increased the effectiveness of the coating by delaying molds' apparition.     

Sodium Caseinate from Skim Milk Powder by Extrusion Processing: Physicochemical and Functional Properties

Sodium caseinate produced on a pilot-plant-scale directly from skim milk powder (SMP) with two-step extrusion process was compared to a commercial product and a sodium caseinate prepared from commercial acid casein by extrusion-processing. The products were compared in terms of physicochemical properties and functional properties, as well as microbiological quality. Although differences existed between the caseinates, overall, those produced from SMP by extrusion appeared comparable to commercial caseinate. Results indicate that a good-quality sodium caseinate with the requisite properties normally associated with commercial sodium caseinate could be produced directly from SMP by extrusion-processing.     

Nutritional quality of diacetyl/urea treated caseinates

Diacetyl markedly improves the heat stability of milk, especially in the presence of urea. The present study was undertaken to investigate the effects of severe heat treatments in the presence of diacetyl and urea on the nutritional value of casein.Acid casein solutions (7% w/v protein) at pH 6·6 were heated at 120°C for 20 min in the presence of the following: (1) no additive; (2) 10 mm urea; (3) 1·5 mm diacetyl; (4) 5 mm diacetyl; (5) 1·5 mm diacetyl + 10 mm urea; (6) 5 mm diacetyl + 10 mm urea. All caseinates treated with diacetyl or diacetyl plus urea were visibly browned. When compared with caseinate heated alone, available lysine was reduced by 8%, 9·5%, 8% and 7% in the caseinates treated with 10 mm urea, 1·5 mm diacetyl + 10 mm urea, 5 mm diacetyl and 5 mm diacetyl + 10 mm urea, respectively, while treatment with 1·5 mm diacetyl, 5 mm diacetyl and 5 mm diacetyl + 10 mm urea reduced arginine content by 10%, 15% and 11%, respectively, and tryptophan content by 5%, 8% and 8%, respectively. PER, NPR and available methionine were unaffected by diacetyl and/or urea except for a 9% reduction in PER in caseinate treated with 5 mm diacetyl + 10 mm urea.     

Calcium-Induced Destabilization of Oil-in-Water Emulsions Stabilized by Caseinate or by β-Lactoglobulin

The stability to aggregation of 20% soya oil-in-water emulsions stabilized by 0.3 to 2% sodium caseinate or β-lactoglobulin in the presence of calcium chloride solutions was studied using light scattering and electron microscopy. Stability increased with the amount of protein in the emulsion, and decreased with the concentration of added calcium. Growth of particle size with concentration of Ca²⁺ was more in emulsions containing lower concentrations of protein. Sodium chloride at 50 and 100 mM stabilized both systems to the presence of calcium ions. Microstructure and light scattering showed caseinate emulsions formed clusters even at low concentrations of Ca²⁺ while β-lactoglobulin emulsions formed extensive strands.     

Crystallization and X-ray Diffraction of Crystals Formed in Water-Plasticized Amorphous Spray-dried and Freeze-dried Lactose/Protein Mixtures

ABSTRACT: Effects of proteins (whey protein isolate [WPI], Na-caseinate, and gelatin), drying method, storage relative vapor pressure (RVP), and time on lactose crystallization and crystals formed were investigated using x-ray diffraction (XRD). Crystallization was observed from increasing peak intensities of XRD patterns. Lactose in lactose/protein (5:1,3:1) mixtures crystallized in samples stored at RVP of 44.1% and above in both spray-dried and freeze-dried materials, except in freeze-dried lactose/Na-caseinate and lactose/gelatin mixtures, which showed lactose crystallization at 54.5% RVP and above. The rate of crystallization increased with increasing RVP and storage time. The rate of crystallization in spray-dried materials was higher than in freeze-dried materials, and the crystallization rate decreased with increasing protein content. Lactose crystallized mainly as α-lactose monohydrate in spray-dried lactose/WPI and lactose/gelatin mixtures. Crystals formed in freeze-dried lactose/WPI and lactose/gelatin mixtures were anhydrous β-lactose and α-lactose monohydrate crystals. Lactose crystallized as a-lactose monohydrate in both spray-dried and freeze-dried lactose/Na-caseinate mixtures. Trace amounts of anhydrous β-lactose were present in spray-dried lactose/WPI (5:1) and lactose/gelatin (5:1) mixtures. Peak intensities of XRD patterns for anhydrous β-lactose decreased with increasing protein content and storage time. The crystallization data were successfully modeled using Avrami equation at an RVP of 65.6% and above. These data are important in understanding and predicting storage stability of lactose- and protein-containing food and pharmaceutical materials.     

Influence of Dietary Supplementation with α-Tocopheryl Acetate and Canthaxanthin on Cholesterol Oxidation in ω3 and ω6 Fatty Acid-enriched Spray-dried Eggs

ABSTRACT: The effect of feeding laying hens linseed oil or sunflower oil, with and without α-tocopheryl acetate and/or canthaxanthin, was evaluated on cholesterol oxidation in spray-dried whole egg at various storage periods. Storage of spray-dried eggs at room temperature in the dark resulted in an increase in cholesterol oxidation products from 18.1 μg/g, after spray drying, to 39.3 μg/g, at 12 mo of storage. No differences were found with either dietary oil or canthaxanthin supplementation. However, α-tocopheryl acetate supplementation resulted in a lower formation of cholesterol oxidation products during storage. No synergistic effect between α-tocopherol and canthaxanthin was detected.     

New method for the purification of electrically charged polysaccharides

A new technique for the purification of pectins using protein (sodium caseinate) was developed and that could replace the process of ethanol which is currently used in industries. Commercial pectins were used as a model to verify the feasibility of the process and to define some important parameters. The results indicated that this purification technique is based primarily on the electrostatic interactions between these two polymers. The electrostatic interactions were strongly dependent on pH and salt concentration. The maximum pectin precipitation was obtained at pH 3.5. At this pH, the pectin acquires a negative charge while the protein is positively charged, promoting thus their attractions. Furthermore, the dissociation of the pectin–caseinates complex and the precipitation of caseinate at pH 4.6 were observed in the presence of salt. This method is very specific, suggesting that it could be used to purify some electrically charged polysaccharides.     

Indicators of non-enzymatic browning in the evaluation of heat damage of ingredient proteins used in manufactured infant formulas

Twelve infant formula ingredients of animal origin (caseinates, whey proteins and hydrolysates of casein and of whey proteins) and three of vegetable origin (soybean proteins) were analyzed. Furosine, hydroxymethylfurfural (HMF) and pyrraline were studied as indicators of thermal damage and available lysine as nutritional indicator, determined by HPLC in phase reverse and UV detector. The objectives were to evaluate heat damage to ingredients used in commercial infant formulas by measuring non-enzymatic browning indicators and to determine the nutritional value of these ingredients by available lysine determination. Very high furosine values were detected in whey proteins, ranging from 354 to 1,435 mg/100 g of protein. Lower furosine values were found in the remaining ingredients, ranging from 1.36 mg/100 g in hydrolyzed casein to 60.5 mg/100 g in sodium caseinate. Available lysine content ranged from 1.85 g/100 g of protein in hydrolyzed casein to 7.91 g/100 g in calcium caseinate. HMF was detected in whey protein samples between 0.16 and 2.47 mg/100 g of protein. Pyrraline was only detected in one sample of whey proteins at 41 mg/100 g of protein. Similar ingredients from different manufacturers show varied heat damage and nutritional values     

SURFACE PROPERTIES OF PROTEIN LAYERS ADSORBED FROM MIXTURES OF GELATIN WITH VARIOUS CASEINS

We report surface tensions and surface shear viscosities of protein layers adsorbed from mixtures of gelatin +α_s11-casein, β-casein, k-casein or sodium caseinate. Under conditions where the two protein components carry opposite net charges, the combined experimental data at 25C and neutral pH are consistent with a two-layer model of the mixed protein film. The surface properties of sodium caseinate lie intermediate between those for the two major individual caseins (α_s1 and β).     

Study of commodity properties of food emulsions Part 1. The effect of dispersion medium composition on kinetic stability of O/W emulsions containing proteins,acidic polysaccharides and calcium salts

The effect of concentrations of acidic polysaccharide and calcium ions on the kinetic stability, viscosity and dispersity of protein-containing O/W emulsions is studied. Variation of kinetic stability of the emulsions studied is independent of dispersion composition. In a wide range of calcium acetate concentrations a correlation is observed between kinetic stability and viscosity of emulsions at sodium alginate concentration in the dispersion medium ≤ 0.3%. The transition zone between liquid solution and gel is widened in the presence of sodium caseinate. Maximum kinetic stability is reached at calcium acetate: sodium alginate concentrations of 1.0-1.2 and ～ 6.0, corresponding to optimum conditions for formation of homogeneous crosslinked structures of calcium alginate and calcium caseinate.     

Protein Quality of Cheddar Cheese Compared with Casein and Fabricated Cheese in the Rat

The protein quality of freeze-dried cheddar cheese, spray-dried cheddar cheese, freeze-dried fabricated cheddar cheese (with casein as the main protein source), and sodium caseinate was evaluated in rats using the protein efficiency ratio (PER) assay (AOAC procedures) in two feeding experiments with casein as the control. Biological evaluation of the products showed that PER values for freeze-dried cheddar cheese were significantly higher than casein (3.7 vs 2.5). Freeze-dried cheddar also had a PER value significantly higher than spray-dried cheddar cheese (3.7 vs 3.0). Freeze-dried fabricated cheddar cheese and sodium caseinate had PER values not significantly different from the casein control.     

Effect of dielectric barrier discharge atmospheric cold plasma treatment on structural,thermal and techno-functional characteristics of sodium caseinate

The present work aimed to study the effect of dielectric barrier discharge (DBD) atmospheric cold plasma (CP) on the structure-function relationship of sodium caseinate. The caseinate powder was subjected to CP for 0, 2.5, 5 and 10 min, and its physicochemical, structural, thermal, emulsifying and film-forming properties were investigated. The FTIR spectra revealed a higher β-structures and a diminished-random coil conformation after CP treatment. The DSC profiles confirmed higher glass transition in CP-processed caseinates. The CP-treated caseinates exhibited higher interfacial activity and developed emulsions with smaller particle size and higher physical stability. The SEM images and mechanical analysis of produced caseinate film showed that CP treatment up to 5 min promoted the formation of a more uniform microstructure and reinforced the tensile strength. These findings propose that CP treatment may be efficiently employed to mildly modify caseinate structure and improve its techno-functional properties.Industrial relevanceCold plasma (CP) is an emerging eco-friendly efficient technology, which has gained increasing attention in the food and pharmaceutical industries. It is a potent and outstanding technique for non-thermal microbial decontamination, enzyme deactivation, surface modification, functionalization, and etching of coating materials. The CP may provide opportunities in a targeted modification of the structure and interfacial performance of biopolymers. This work demonstrates the potential of CP for mild modification of the structure, emulsifying and film-forming properties of sodium caseinate powder while maintaining its appearance features. Sodium caseinate treated by plasma can develop an emulsion with significantly higher physical stability and edible film with augmented mechanical strength, opening a wide range of promising applications in food and pharmaceutical industries such as the development of tailor-made protein-based films, coatings, emulsions, and emulsion films.