Textural properties of a model aqueous phase in low fat products. Part 1: Alginate, caseinate and starch in isolation, and in starch containing binary mixtures

Summary The effect of increasing additions of calcium on the textural properties of alginate, caseinate and starch dispersions was investigated to provide a baseline for further work on mixtures of these biopolymers. Increasing concentrations of calcium transformed the alginate solutions into gels having a maximum rigidity at 1000 and 300 p.p.m. Ca²⁺ for 2.0 and 0.5% of the polysaccharide, respectively. Gelation was achieved by cooling which unveiled a two stage process of network formation. Caseinate solutions (12%) showed an increased viscosity with a rising Ca²⁺ concentration up to 2250 p.p.m., above which viscosity decreased. Starch (2.5%) exhibited a slight loss in storage modulus (G') with increasing levels of calcium. The texture of the alginate starch mixture was determined by the alginate component (two stage gelation process), but inverted to that of starch at high levels of added Ca²⁺. In the absence of the counterion, casein had an adverse effect on the strength and cohesion of starch networks. At 400 p.p.m. Ca²⁺, the protein forms a continuous liquid like phase which suspends the starch inclusions thus dictating the textural properties of the mixture. Caseinate continues to dominate up to 1200 p.p.m. Ca²⁺, at which point the starchy matrix influences the system once more. Finally at higher levels of the counterion the sample phase inverts back to a starch continuous gel. Part 2 of this work examines the effect of calcium on the remaining preparations in order to facilitate the formulation of improved low fat products.     

Influence of sodium and calcium ions on rheological behaviour of wheat glutenins extracted in alkaline ethanol solution

Wheat glutenins were extracted in alkaline aqueous solution containing 50% (v/v) ethanol and 0.025  m NaOH from the gluten residue after extraction using 70% (v/v) aqueous ethanol. Rheological behaviours of the solutions were investigated as a function of protein concentration and ion strength. Sodium (Na⁺) and calcium (Ca²⁺) ions have different influences on the rheological behaviour of the glutenin solution of 48 mg mL⁻¹. While addition of Na⁺ results in Newtonian fluids with a reduction in apparent viscosity in comparison with the salt-free solution, addition of Ca²⁺ leads to the formation of a viscoelastic network with enhanced shear-thinning. The solutions containing 0.2  m and 0.4  m Ca²⁺ exhibit yielding at low strain rates. The solution containing 0.6  m Ca²⁺ behaves as a pseudoplastic fluid with the appearance of two Newtonian plateaus at low and high strain-rate limits.     

Determination of chloride, nitrate and calcium ions in sugar with ion selective-electrodes

Chloride, nitrate, and calcium ion-selective electrodes were tested and found satisfactory for the determination of the corresponding ions in highly refined white sugar, molasses and other impure sugar samples at different stages of sugar manufacturing or refining. The interferences by Br⁻ and I⁻ ions in Cl⁻ determination were eliminated by oxidation with 3 M HNO₃ and passing air to remove the free Br₂ and I₂ formed. The Cl⁻ concentration was then determined with a chloride-selective electrode against a calibration curve. Chloride should not be determined by ashing sugar, since this causes high losses of Cl⁻. It was found that NO₃⁻ and free Ca²⁺ ions could be determined directly in the sugar solution against corresponding calibration curves. Total calcium was determined after ashing of sugar samples. The ash was dissolved in 0.1 M HCl and passed through an anion exchange resin to remove PO³⁻₄ and SiO₂₋₃ ions, and Ca²⁺ was determined as before. Bound calcium was obtained by subtracting values of free from total calcium. Determination of bound calcium was useful to monitor the process of liming. For comparison, the three ions were also determined with acceptable precision without removing interfering ions using the method of standard addition and Gran's plot. The errors of determination for both direct and standard addition techniques were 3% for Cl⁻ and NO⁻₃ and 1–5% for Ca²⁺.     

INFLUENCE OF SALTS AND pH ON THE FIRMNESS OF COOKED SNAP BEANS IN RELATION TO THE PROPERTIES OF PECTIN

Solute conditions inside cooked bean pods were adjusted by soaking the pods in different solutions. Interactions of Ca⁺⁺ and Na⁺ showed increasing firmness as Ca⁺⁺ concentration was raised and decreasing firmness as Na⁺ was raised. Chelating agents removed Ca⁺⁺ and decreased firmness. Higher pH gave lower firmness except in the presence of excess Ca⁺⁺. The presence of Na⁺ decreased the effect of pH on firmness. Urea decreased firmness when pods had been previously treated with a chelator. The effects of treatments on firmness were related to the behavior of pectin solutions and gels.     

EFFECT OF pH AND CATIONS ON THE THERMALLY INDUCED GELATION OF OVALBUMIN

The gelation of ovalbumin in the presence of salts containing Ca⁺² and Mg⁺² at various pH values was investigated. Characteristics of the gels produced were evaluated using penetration measurements on an Ottawa Texture Measuring System as well as dynamic rheology on a Bohlin VOR rheometer. Gel properties were related to cation binding (equilibrium dialysis) and to changes in protein structure (differential scanning calorimetry). Cation binding generally increased with increasing salt concentration, and Mg⁺² bound to a greater extent than Ca⁺² at the higher levels studied. The impact of this binding on gel structure was dependent on pH and the technique used to evaluate structure. At pH 5 proteins tended to coagulate regardless of the type or amount of salt. At pH 7, the highest rigidity values from penetration measurements were obtained at salt levels of 0.005 M. At pH 9, the salt concentration for maximum rigidity varied with the salt, while the storage moduli (G') from dynamic rheology were highest at the highest salt concentration used. Based on rigidity data, the inclusion of 0.005 M MgSo₄ would give a product with the greatest rigidity over a wide pH range.     

AN ESTEROLYTIC ACTIVITY FROM A WILD EDIBLE MUSHROOM, LYCOPERDON PERLATUM

Lycoperdon perlatum Pers. (Lycoperdaceae, Agaricales, Agaricomycetidae, Agaricomycetes, Basidiomycota, Fungi) was evaluated for its esterolytic potential. Native electrophoresis of the crude extracts showed four bands having Rf values of 0.34, 0.39, 0.52 and 0.59. The esterase showed the highest activity toward a short-chain substrate, p -nitrophenyl acetate. Optimum reaction conditions for L. perlatum crude extract were attained at pH 8.0 and 40C. Esterolytic activity of enzyme extract was stimulated in the presence of Mn^{2 +} , Fe^{2 +} , Ca^{2 +} and Zn^{2 +} in the reaction mixture. The enzyme activity was stimulated by incubation at pH 6.0 but retained 77% of its original activity at its optimum pH after 24 h. Thermal inactivation was displayed after incubation for 20 min at various temperatures above 30C. At 1 mM final concentration, 2-mercaptoethanol, dithiothreitol, ethylenediamine tetraacetic acid and p -methylphenyl sulfonylfluoride inhibited the esterolytic reaction. These results support that the crude L. perlatum extract possesses an esterolytic activity having properties similar to other esterases.

PRACTICAL APPLICATIONS

Esterases catalyzing the cleavage and formation of ester bonds are known α/β-hydrolases (EC 3.1.1.X). Esterases are used for the synthesis of flavor esters for the food industry, modification of triglycerides for fat and oil industry and resolution of racemic mixtures used for the synthesis of fine chemicals for the pharmaceutical industry. Therefore, the search for new enzyme sources is important for the development of new enzymes and applications.     

Physicochemical Properties of Frozen Red Hake (Urophycis chuss) Mince as Affected by Cryoprotective Ingredients

ABSTRACT: Effects of alginate, iota-carrageenan, soy protein concentrate (SPC), sodium tripolyphosphate (STPP), and sorbitol on physicochemical and sensory properties of red hake mince stored at −20 °C for 17 wk were investigated. The addition of 0.4% alginate, 4% sorbitol, and 0.3% STPP kept the mince from hardening and improved its dispersibility during mixing. This is believed to be a result of reduced protein denaturation as evidenced by higher levels of water, salt, SDS-soluble proteins, and higher free sulfhydryl contents than the untreated control mince, which hardened with compact texture and exhibited considerable syneresis. Alginate appears to be responsible for preventing muscle fiber interaction through electrostatic repulsion and chelating Ca²⁺, thus improving dispersibility. Sorbitol and STPP with or without SPC and iota-carrageenan did not improve the dispersibility.     

Influence of Gonadal Stage of Hake (Merluccius Hubbsi Marini) on Biochemical Properties of Myofibrils Stored at 2 to 4 °C

ABSTRACT: The influence of the gonadal stage of hake on the biochemical properties of myofibrils stored at 2 to 4 °C was studied. At 0 time and during storage, both Mg²⁺-Ca²⁺-ATPase activity and Ca²⁺ sensitivity of myofibrils from post-spawned hake were significantly higher (p < 0.01) than those of pre-spawned fish. The profiles of SDS-PAGE gels of unstored and stored myofibrils from pre-spawned hake showed a partially denatured myosin heavy chain. The actin-myosin ratio in myofibrils from pre-spawned hake was significantly lower (p < 0.01) than the ratio in post-spawned hake. Irrespective of the gonadal condition of fish, no changes in the myosin-actin ratio of stored myofibrils were observed.     

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).     

Epidermal tight junction: The master skin barrier regulator

IFSCC Magazine , 12 (2009) (2) 87–91
Tight junctions between adjacent epithelial cells control paracellular permeability of solutes and maintain cell polarity by fencing lipid bilayer components into demarcated apical and basolateral domains. In the present study we investigated the role of epidermal tight junctions in two skin physiological processes, 'formation of the epidermal calcium ion (Ca²⁺) gradient' and 'polarized lamellar body secretion'. The former is based on the fact that the epidermal Ca2+ gradient is closely related to epidermal differentiation and the latter on the knowledge that polarized lamellar body secretion is essential to supply intercellular lipids to the stratum corneum. We hypothesized that tight junctions might form the Ca²⁺ gradient in the epidermis by sealing cell-cell contact at the stratum granulosum and allow the lamellar bodies to be normally secreted toward the stratum corneum by giving granular cells polarity. In our experiments we discovered that tight junctions control not only both intercellular Ca²⁺ permeability and fluorescent ceramide analog (Cer-FL) secretion in cultured normal human keratinocyte cells but also both intercellular calcium distribution and polarized lamellar body secretion in the skin equivalent. Thus, tight junctions should be responsible for linking a series of processes from epidermal differentiation to stratum corneum barrier formation. Our findings suggest that tight junctions should have a crucial role not only in epidermal barrier function but also in both epidermal differentiation and stratum corneum barrier function.
Keywords: Calcium gradient, cell polarity, lamellar body, skin barrier, tight junction
IFSCC Basic Research Award winning paper presented at the 25th IFSCC Congress 2008, Barcelona, Spain     

Technical Approach to Simplify the Purification Method and Characterization of Microbial Transglutaminase Produced from Streptoverticillium ladakanum

In order to fast and economically purify MTGase from Streptoverticillium ladakanum , a stepwise elution method was developed and compared with linear gradient elution method. MTGase was purified to electrophoretical homogeneity by using CM Sepharose CL-6B and Blue Sepharose Fast Flow chromatographies by linear gradient or stepwise methods. The recovery of MTGase by linear gradient and stepwise methods were 68.4% and 81.0%, respectively. The optimal temperature and pH were 40 °C and 5.5, respectively. It was stable at pH 5.0 to 7.0 and had a rate constant (KD) of 6.21 °o 10^-5 min^-1 for thermal inactivation at 45 °C. The purified MTGase was activated by K⁺ Na⁺, Ca²⁺, Mn²⁺, and Mg²⁺, not affected by Fe³⁺, EDTA, but inhibited by Cu²⁺, Zn²⁺, Hg²⁺, Ni²⁺, Co²⁺, Cd²⁺, PCMB, NEM, IAA, and PMSF. A simple stepwise method was developed for the purification of MTGase from S. ladakanum.     

The Green Oat Story: Possible Mechanisms of Green Color Formation in Oat Products during Cooking

ABSTRACT:  Consumers occasionally report greenish colors generated in their oat products when cooking in tap water. Here we have investigated pH and ferrous (Fe²⁺) ion as possible mechanisms for this color change. Steel-cut oat groats can turn brown-green color when cooked in alkaline conditions (pHs 9 to 12). Extraction of this color with methanol, and high-pressure liquid chromatography indicated a direct association of this color with the phenolic acid or avenanthramide content of the oat. The presence of 50 mM NaHCO₃ in water will cause oat/water mixtures to turn alkaline when cooked as CO₂ is driven off, generating OH⁻ ion. Although tap water rarely, if ever, contains so much bicarbonate, bicarbonate is used as a leavening agent in baking applications. Industrial interests using baking soda or alkaline conditions during oat processing should be aware of possible off color generation. We have also found that as little as 10 ppm Fe²⁺ will turn oat products gray-green when cooked. The aleurone stained darker than the starchy endosperm. Other divalent cations, such as Ca²⁺ or Mg²⁺ had no effect on cooked oat color. As much as 50 ppm Fe²⁺ may be found in freshly pumped well water, but Fe²⁺ reacts quickly with oxygen and precipitates as Fe(OH)₃. Thus, some freshly pumped well water may turn oats green when cooked, but if the water is left under atmospheric conditions for several hours, no discoloration will appear in the cooked oats.     

Influence of pH and Salts on Egg White Gelation

ABSTRACT: Egg white is used in food products for various functional properties. These are strongly influenced by pH, ionic strength, type and concentration of salts. Through an experimental design strategy, the aim of this study was to quantify the influence of pH, cations, and anions naturally present in egg white, and of citrate on egg white gelation. Results showed that pH and Fe³⁺ modified the coagulation temperature of egg white and consequently, the gel characteristics. High concentrations of NaCl decreased the water-holding capacity and the microstructure of egg white gels. At pH 7, viscoelastic properties and microstructure of egg white gels were altered by Ca²⁺ and Mg²⁺ addition.     

Purification and Characterization of Escherichia coli Sulfite Reductase and its Application in Surimi Processing

ABSTRACT: The NADPH-sulfite reductase from Escherichia coli was purified to electrophoretic homogeneity by ammonium sulfate fractionation, and DEAE Sephacel and Sephacryl S-300 HR chromatography. The recovery and molecular weight were 31.7% and 119000, while the optimal pH and temperature for the activity were 7.7 and 25°C, respectively. It was strongly inhibited by PCMB, KCN, Hg²⁺, Fe²⁺, Fe³⁺, Ca²⁺, Co²⁺, and Cu²⁺, moderately by NEM, PMSF, IAA, Cd²⁺, Zn²⁺, Mn²⁺, and Ba²⁺. Addition of purified reductase significantly increased the reactive SH and gel strength of surimi prepared from frozen mackerel. The data suggest the high potential of microbial NADPH-sulfite reductase in surimi processing using frozen fish or denatured muscle proteins as raw materials. Keywords: Escherichia coli , sulfite reductase, mackerel, purification, characterization     

Effect of added calcium chloride on the physicochemical and rheological properties of aqueous mixtures of sodium caseinate/sodium alginate and respective oil-in-water emulsions

Changes induced by addition of calcium chloride in particle size distribution and electrokinetic potential were determined in sodium caseinate/sodium alginate mixtures dissolved in water or acetate buffer at ambient temperature. Rheological properties of aqueous mixtures and respective oil-in-water emulsions (30% oil w/w) were evaluated using a low-stress rheometer. Stability and particle diameter of emulsions were measured. Caseinate and alginate solutions were negatively charged and showed negative electrokinetic potential; however values of mixtures were between those of the values for the individual hydrocolloids. When calcium ions were added the electrokinetic potential diminished while the negative charge was preserved. Aqueous mixtures of caseinate and alginate showed average particles size between of those of caseinate or alginate samples. We observed low viscosity values and Newtonian behavior for both caseinate (1 and 2%) and alginate (0.1%). Addition of 5 mM CaCl₂ to alginate solutions induced shear-thinning behavior as well as the development of viscoelasticity. Both the viscosity and the elastic modulus of these polysaccharide solutions were attenuated by the presence of protein or dispersed oil in mixtures or emulsions, respectively. High average particle diameter of emulsions prepared was obtained (close to 10 μm), however, stability of emulsions was possible only with the addition of CaCl₂ to the mixtures, in both water and acetate buffer. In these cases elastic behavior predominated to viscosity in the formation of emulsions, confirming the prevalence of aqueous phase rheology on emulsions.     

Shelf life of several marine fish species of Bangladesh during ice storage

Organoleptic, biochemical and bacteriological aspects of five tropical marine fish such as silver jewfish, Bombay duck, big-eye tuna, Chinese pomfret and ribbon fish stored in ice were studied. Organoleptically all fish were found acceptable for 10–13 days before becoming inedible. Proximate analysis showed that moisture content increased slightly; protein and lipid content decreased gradually and ash had little or no significant change. pH, TVB-N, peroxide and aerobic plate count values increased with increasing storage period but the values were within acceptable range up to 10 days of storage. Changes in myofibrillar ATPase activity and solubility of these fishes showed that Ca²⁺ ATPase in the presence of both 0.1  m and 0.5  m KCl decreased gradually whereas no marked changes were observed in the Mg⁺² ATPase activities in the presence/absence of Ca⁺². Myofibrillar protein solubility of all fish samples also decreased considerably during ice storage. The decrement in Ca²⁺ ATPase activity and solubility indicates denaturation of myofibrillar protein of fish samples during ice storage.     

Influence of some polyvalent organic acids and salts on the colloidal stability of milk

Fifteen polyvalent organic salts and acids increased, some very markedly, the heat stability of milk progressively with increasing concentration; acetate and mesaconic acid had no effect, and maleate caused destabilization. Citrate, oxalate and EDTA markedly reduced the [Ca⁺] in the milk and increased its ethanol stability by shifting the ethanol/pH profile to lower pH values. These additives ≥ 20 mmol/l prevented the coagulation of milk by rennet, but the other additives caused only slight increases in RCT .
Citrate, EDTA and oxalate disrupted casein micelles and would therefore not be suitable additives: however, the other acids and salts did not alter the appearance of the milk and might be recommended as suitable additives to improve the heat stability. In terms of the response to the level of Ca²⁺ and colloidal calcium phosphate in milk, there appeared to be a correlation between ethanol stability and rennet coagulation time.     

Effects of Anions and Cations on Sugar Utilization in Cucumber Juice Fermentation

ABSTRACT: :
The extent of glucose and fructose utilization during cucumber juice fermentation was affected differentially by the addition of 10 to 360 mM of selected anions (chloride, nitrate, sulfate, phosphate, acetate, lactate, and citrate) and cations (Na⁺, K⁺, NH₄⁺, Ca²⁺, Mg²⁺, and Mn²⁺). Inorganic anions generally suppressed utilization of both sugars, particularly at higher concentrations. Acetate and lactate increased utilization of fructose, but not glucose, while citrate increased utilization of both sugars. Of the cations tested, 10-60 mM Mn⁺² significantly (P < 0.05) increased utilization of both sugars, but higher concentrations reduced utilization, as compared with the control. Evidence indicates that brine composition can significantly influence sugar utilization during cucumber fermentation, and may be important in developing controlled fermentation strategies for brined cucumbers.     

PROPERTIES OF CHITIN DEACETYLASE FROM CRUDE EXTRACTS OF MUCOR ROUXII MYCELIUM

The catalytic properties of chitin deacetylase from Mucor rouxii were studied with the aim of using the results for control of the properties of chitosan prepared by enzymatic deacetylation. A crude deacetylase extract from the mycelium of Mucor rouxii exhibited maximal activity at pH 5.8 with both water-soluble and acid-soluble chitosan. The extracellular enzyme of the culture medium exhibited maximal activity at pH 4.8. The deacetylase in the crude extract was stable over the pH range of 4.1–8.9 at 25C, retaining 85–100% of maximal activity at 40C. The extract was most active towards acid-soluble chitosan at 50C and pH 5.8. Chitin deacetylase was stable to 40C when incubated without substrate, with 85% of the activity retained at 50C. Ca²⁺, Mn²⁺, and Zn²⁺ had no effect on activity, while EDTA, Fe²⁺, and Fe³⁺ caused partial inhibition in extracts incubated without substrate for 1 h at 25C and pH 5.8. The deacetylase in the mycelial extract and in the culture medium was slightly activated by Co²⁺. The differences in temperature optima and thermal stability of deacetylase and hydrolytic enzymes can be used for controlling the degree of hydrolysis of chitosan, while the difference in pH stability has been used for prepurification, resulting in 3-fold increase in specific activity of deacetylase .     

ATLANTIC QUEEN CRAB (Chionoecetes opilio), JONAH CRAB (Cancer borealis), AND RED CRAB (Geryon quinquedens). Proximate Composition of Crabmeat from Edible Tissues and Concentrations of Some Major Mineral Constituents in the Ash

The gross composition of the edible tissues of Atlantic Queen crab, Jonah crab and Red crab was determined by standard analytical methods and results compared to those obtained for analysis of edible tissues in other species of crab. In addition, the concentrations of various cationic constituents of the ash (Na⁺, K⁺, Ca⁺⁺ and Mg⁺⁺) and phosphate were estimated in hydrogen peroxide-sulfuric acid digests of meat samples of each of the three Crab species. The nutritive value of crabmeat from these species is discussed in terms of protein content, mineral composition and overall calorific value.