Gluconolactone Research Articles

Phase Model Interpretation of the Structural Properties of Two Molecular Soy Protein Fractions

The structural properties of mixtures of two molecular soy fractions, 11S (glycinin) and 2S, were investigated in the presence of glucono-delta-lactone (GDL) during an isothermal run at 25 degrees C for 1500 min. Analytical methodology included small-deformation dynamic oscillation, visual observations, scanning electron microscopy, and blending-law modeling. The aim of the work was to identify the state of phase separation and the pattern of solvent distribution between the two constituent polymers. It was found that the high molecular weight distribution of 11S supported rapid kinetics of structure formation, with this continuous matrix being concentrated and, hence, further reinforced in the presence of small additions of 2S. Blending-law modeling suggested that 2S was able to retain disproportionate volumes of solvent within its phase. A consequence of such property was that high additions of 2S leading to equal concentrations of the two molecular fractions in the blend resulted in a catastrophic drop in the values of the overall network strength. This behavior is rather unexpected for the structural properties of a phase-separated system, and it has been rationalized on the basis of the high water-holding capacity of the small molecular weight fraction. 2S entraps in its phase the polymeric segments of glycinin, which are then unable to become structural knots of a cohesive three-dimensional morphology observed in single 11S preparations.

Lubricating jelly helps improve image clarity of inclusions entombed in amber and copal

While photographing fossils entombed in amber and copal, I began using lubricating jelly on the specimens as a temporary “mounting” medium to cover the area of photographic interest. Copal is partially polymerized resin (Santiago-Blay & Lambert 2007). Th e product I purchased (using personal funds, approximately USD 4.50 in a local supermarket chain, price for these products ranges approximately from USD 3–14) is described as an “alcohol-free” ... “clear” ... “greaseless, water-soluble, non-irritating lubricant for general needs”. Th ese products are commonly used in medical procedures and for sexual activities. Once the jelly is carefully placed on the specimen, minimizing the presence of air bubbles, a clean cover slip is placed gently on top of the jelly blob. Th e refractive index of amber or copal matches that of the jelly thus reducing scratches and lensing eff ects of rounded pieces. Th e improvement on image clarity is often obvious (Figs. 1–2). Removal of the jelly from the specimen is easily accomplished with lukewarm water and a towel. Lubricating jelly, a non-sterile product, has “chlorhexinidine, gluconate and methylparaben as preservatives, in a vehicle containing glucono delta lactone, glycerin, hydroxyethylcellulose, sodium hydroxide, and purifi ed water” and did not appear to damage the specimens. Th e jelly’s greater viscosity than that of glycerin, a compound commonly used to improve imaging, increases the possibilities of good imaging, particularly when specimens are located in areas diffi cult to photograph. Amongst several high viscosity translucent materials I used during the summer 2007 to improve image clarity, lubricating jelly performed the best. Acknowlegments. I thank Scott Whittaker (Electron Microscope Laboratory, Natural Museum of Natural History Washington, District of Columbia 20560 USA) for numerous discussions on improving the photographic quality of biological inclusions in amber and copal. Anonymous reviewers off ered suggestions to this manuscript. I am grateful to several colleagues who tested this method successfully for research and did not consider this subject matter “too personal”.

Acid Gelation Properties of Heated Skim Milk as a Result of Enzymatically Induced Changes in the Micelle/Serum Distribution of the Whey Protein/κ-Casein Aggregates

Changes in the acid gelation properties of skim milk as a result of variations in the micelle/serum distribution of the heat-induced whey protein/kappa-casein aggregates, induced by the combination of heat treatment and limited renneting, were investigated. No dramatic change in the zeta potential or the isoelectric point of the casein micelles was suggested, whether the aggregates were all attached to the casein micelle or not. Fluorescence intensity measurement using 8-anilino-1-naphthalenesulfonic acid (ANS) showed that the heat-induced aggregates were highly hydrophobic. Dynamic oscillation viscosimetry showed that acid gelation using glucono-delta-lactone (GDL) started at a higher pH value in prerenneted milk. However, no change in the gelation profile of skim milk could be related to the proportion of aggregates bound to the surface of the casein micelles. The results support the idea of an early interaction between the serum aggregates and the casein micelles on acidification.

Acid Gelation in Heated and Unheated Milks: Interactions between Serum Protein Complexes and the Surfaces of Casein Micelles

The acid-induced interactions between different protein particles in milk (casein micelles and serum protein/kappa-casein complexes) were studied in a series of different mixtures of heated and unheated proteins using diffusing wave spectroscopy (DWS) and small deformation rheology. The measurements were made as functions of pH during acidification by addition of glucono-delta-lactone (GDL). Heat treatment (85 degrees C, 10 min) affected the composition of the serum and the reactivity of casein micellar surface based on the pH at which the casein micelles aggregated during acidification. It was observed that the gel points as defined by DWS and rheology did not always coincide. The experiments showed that all systems containing heated serum proteins gelled at a higher pH than those containing unheated serum proteins. For systems containing heated micelles, an intermediate network can be formed between heat-induced aggregates of serum proteins and kappa-casein formed at the surfaces of the micelles and dispersed as soluble complexes in the serum. This can explain the observation that DWS measurements detected aggregation of casein micelles at an earlier stage than did rheology. For systems containing unheated micelles and soluble complexes from heated milk, the results appear to be explained only by a direct interaction between soluble serum protein complexes and the casein micelles themselves, once the pH has decreased to below about 5.5. Comparison of the different systems studied gives a more complete description of the possible mechanism of interaction of the different protein materials during the acid-induced coagulation of milk-based systems.

EXTENDING THE SHELF LIFE OF SET FISH BALL

ABSTRACT Set fish ball is an extruded surimi‐based product that is popular in Singapore and other Southeast Asian countries. Oversetting of set fish ball occurs at chilled temperature during storage. Shelf‐life extension of set fish ball by reducing oversetting conditions and microbial counts were examined. Encapsulated citric acid (CT) and glucono‐delta‐lactone (GDL) were used to reduce oversetting. Acetic acid, GDL and chitosan were used to inhibit the growth of microorganisms. Shelf life was measured for a period of 21 days at 4C. At day 21, a reduction of 46, 56 and 26% in breaking force compared with the control (without additives) was observed for 0.5% GDL, 1.0% GDL and CT, respectively. GDL at 1.0% was shown to be the most effective in controlling the oversetting of set gel. Chitosan (1%) dissolved in acetic acid maintained both aerobic plate and yeast counts at <1 log cfu/g throughout 21 days of storage.

Instrumental Textural Characteristics of Restructured Carrot Cubes

Studies were carried out on the instrumental textural evaluation of restructured carrot cubes. The experiment was conducted by incorporating different levels of alginate, glucono delta lactone (GDL), and calcium salt to the carrot pulp. Investigations showed that as pulp level increased from 0 to 90%, there was a corresponding decrease in failure stress, failure strain, and deformability modulus. Instrumental textural profile analysis (TPA) parameters viz. hardness, springiness, gumminess, cohesiveness, chewiness, and resilience also showed a similar trend. Effect of formulation variables, i.e., alginate, GDL, and calcium salt on hardness (response variable) were evaluated by the application of response surface methodology. All the three ingredients showed a significant (P < 0.05) influence on hardness of carrot gel. Heat treatment of restructured carrot samples resulted in an increased hardness, cohesiveness, gumminess, and chewiness while springiness, cohesiveness, and resilience decreased. The data indicated that the shrinkage during thermal treatment may be responsible for the change in textural attributes. The authors concluded that a thermally stable restructured product with appreciable textural integrity can be obtained from carrot pulp.

Functional and Structural Properties of 2S Soy Protein in Relation to Other Molecular Protein Fractions

The purpose of this investigation is to develop a better understanding of the structure-function relationship of the 2S fraction of soy protein that has not been considered in earnest by the research community. Defatted soy flour was used to extract the three major fractions of the protein (2S, 7S, and 11S). It was found that 2S exhibits better foaming and emulsification properties than the other two molecular fractions. Work was extended to structural properties, which were monitored using spectrophotometry, atomic force microscopy, scanning electron microscopy, small-deformation dynamic oscillation on shear, and large-deformation compression testing. An experimental protocol utilizing glucono-delta-lactone (GDL), GDL with N-ethylmaleimide, or GDL with urea was capable of identifying the nature of molecular interactions responsible for gelation. Surprisingly, it was found that in the initial stages of structure formation, 2S fared better than 7S, with 11S exhibiting the highest rates of aggregation. Given time, however, 7S produced a firmer network with a better water-holding capacity than that of 2S. Non-covalent interactions, as opposed to disulfide bridging, were found to be largely responsible for the changing functionality of the molecular fractions throughout the experimentation from the formation of a vestigial structure to that of a mature gel.

Formation of stable nanoparticles via electrostatic complexation between sodium caseinate and gum arabic

The formation of electrostatic complexes between sodium caseinate and gum arabic (GA) was studied as a function of pH (2.0-7.0), using slow acidification in situ with glucono-delta-lactone (GDL) or titration with HCl. The colloidal behavior of the complexes under specific conditions was investigated using absorbance measurements (at 515 or 810 nm) and dynamic light scattering (DLS). In contrast to the sudden increase in absorbance and subsequent precipitation of sodium caseinate solutions at pH < 5.4, the absorbance values of mixtures of sodium caseinate and GA increased to a level that was dependent on GA concentration at pH 5.4 (pH(c)). The absorbance values remained constant with further decreases in pH until a sudden increase in absorbance was observed (at pH(phi)). The pH(phi) was also dependent upon the GA concentration. Dynamic light scattering (DLS) data showed that the sizes of the particles formed by the complexation of sodium caseinate and GA between pH(c) and pH(phi) were between 100 and 150 nm and these nanoparticles were visualized using negative staining transmission electron microscopy (TEM). Below pH(phi), the nanoparticles associated to form larger particles, causing phase separation. zeta-Potential measurements of the nanoparticles and chemical analysis after phase separation showed that phase separation was a consequence of charge neutralization. The formation of complexes between sodium caseinate and GA was inhibited at high ionic strength (>50 mM NaCl). It is postulated that the structure of the nanoparticles comprises an aggregated caseinate core, protected from further aggregation by steric repulsion of one, or more, electrostatically attached GA molecules.

The viscoelastic properties of soybean curd (tofu) as affected by soymilk concentration and type of coagulant

SummaryThe viscoelastic properties of different types of tofu were investigated. Soymilk concentrations were 5, 6, 7, 8 and 9%. Coagulants used were 30 mm CaSO4 or 30 mm glucono‐delta‐lactone (GDL). As the concentration of soymilk was increased viscosity and handling difficulties increased. A high concentration of soymilk in tofu gave a high break stress and produced hard tofu. The four‐element Burgers model fitted the creep behaviour and both viscous and elastic parameters could be acquired from model analysis, reflecting changes in elasticity and viscosity of tofu. The constant viscous parameter in the model increased with increasing soymilk concentration. The viscous parameters of viscoelastic materials like tofu gel, obtained from small deformation tests, seemed to correlate, to some extent, with the break stress obtained from large deformation tests. For hard tofu production increasing the soymilk concentration within a certain range and the partial replacement of calcium sulphate coagulant by GDL could be effective options.

Glucono Delta-lactone의 첨가가 쌀밥의 품질에 미치는 영향

쌀밥의 저장기간 연장과 품질개선을 목적으로 glucono delta-lactone(GDL) 및 acetic acid(AA)를 첨가하여 취반한 후 30℃에 저장하면서 미생물학적, 물리적 색도, 조직감을 평가하였다. 대조구와 아세트산 0.05% 및 GDL 0.05% 첨가구가 저장 중 미생물 생육으로 인해 부패된 것과 달리 아세트산 0.1% 첨가구와 GDL 0.1%~0.2% 첨가구는 저장 72시간까지 미생물이 검출되지 않았다. 색도의 경우 아세트산과 GDL 첨가에 의해 명도는 증가하였고 황색도는 감소하였다. 경도는 아세트산과 GDL 첨가에 의해 증가하는 경향이었으나, 점착성은 아세트산 첨가구가 감소한 것과 달리 GDL 첨가구는 증가하여 밥의 조직감이 향상된 것으로 나타났다. 이상의 결과를 종합하여 볼 때 GDL은 쌀밥의 저장기간 연장 뿐만 아니라 밥의 색과 조직감 등 쌀밥의 품질을 향상시키는데 아주 효과적인 것으로 나타났다.

Effect of antimicrobials as ingredients of pork bologna for Listeria monocytogenes control during storage at 4 or 10 °C

Sodium or potassium lactate and sodium diacetate are currently included as ingredients in meat products for control of Listeria monocytogenes contamination during storage. This study compared the antilisterial activity of sodium lactate (SL), sodium diacetate (SD) and glucono-delta-lactone (GDL) used as single or combined ingredients at various levels in pork bologna stored under refrigeration (4°C) or at a mildly abusive temperature (10°C). Moreover, treatments were evaluated for their influence on the microflora of the product. Inoculated (3–4log cfu/cm2; 10-strain composite of L. monocytogenes) bologna slices were vacuum-packaged, and stored at 4°C or at 10°C. Absence of the above antimicrobials from the formulation allowed increases of L. monocytogenes to 8.3log cfu/cm2 in 10–20 days and 8.8log cfu/cm2 in 8–12 days at 4 and 10°C, respectively. Modelling of L. monocytogenes growth as a function of time, indicated that the treatment that resulted in the lowest maximum specific growth rate (μmax) was the combination of 1.8% SL with 0.25% SD (0.009 and 0.084day−1 at 4 and 10°C, respectively), followed by the combination of 1.8% SL with 0.125% SD and 0.125% GDL (0.039 and 0.210day−1 at 4 and 10°C, respectively); the μmax of control treatments was 0.609day−1 at 4°C and 1.34day−1 at 10°C. Lactic acid bacteria (LAB) were the most prominent spoilage organisms isolated from the product. The combination of 1.8% SL with 0.25% SD seemed to be the treatment that controlled growth of LAB more effectively at 4°C, while at 10°C their growth was inhibited more effectively by 0.125% GDL. These findings indicated that meat processors need to select the most effective combination and concentration of these preservatives to achieve safety as well as the shelf-life necessary for these products.

Optimization on response surface models for the optimal manufacturing conditions of dairy tofu

The purpose of this research was to create response surface models through regression on experimental data and to apply the Sequential Quadratic Programming (SQP) and Genetic Algorithms (GAs) on the models to obtain optimal processing conditions for dairy tofu. The two-stage effort of obtaining a surface model using response surface methodology (RSM), and optimizing this model using GAs or SQP techniques was demonstrated to be an effective approach. Both SQP and GAs techniques were able to determine the optimal conditions for manufacturing the probiotic dairy tofu. The conditions were 1% of glucono-delta-lactone (GDL), 0% of peptides level, 3% of isomaltooligosaccharides (IMO) and 18% of milk concentrations, and they were confirmed by verification experiments. Among the SQP and two GAs employed, the SQP, modified with the multi-start capability, is the most efficient one.

Unusual redox catalysis in a ruthenium oxide-Prussian blue combined material.

A stable high-valent RuVII: In pH<12 aqueous solutions, ruthenium tends to convert into lower oxidation states due to the disproportionation-decomposition reaction (DDR) shown. For the first time the novel stabilization of RuVII (as >RuVIIO) was identified in a ruthenium oxide–Prussian blue (RuOx–PB) analogue in an acidic medium (pH 2) without any DDR. The RuOx–PB can selectively catalyze the oxidation of glucose (G) to gluconolactone (GO).

Casein gelation under simultaneous action of transglutaminase and glucono-delta-lactone.

Casein solutions (5% w/v) were treated with microbial transglutaminase (MTG) and glucono-delta-lactone (GDL) under varying conditions in order to obtain gels. Storage modulus (G') and gelation time of the gels were measured by oscillation rheometry, while protein cross-linking was determined by gel permeation chromatography. The addition of only GDL to milk resulted in very weak gels, while MTG on its own was not able to create gel networks. Simultaneous action of both ingredients led to gels, the firmness of which was linearly related to the added amount of MTG, but passed through a maximum with rising GDL concentrations. Using chromatographical analysis, increasing G' values were interrelated with the formation of MTG-induced oligomers. The gelation time was directly proportional to the GDL concentration but not influenced by the addition of MTG within the studied range of concentration.

Contribution of starter cultures to the proteolytic process of a fermented non-dried whole muscle ham product

Porcine longissimus dorsi muscles were cured by brine injection. Curing brine containing 15% (w/v) NaCl, 1.33% (w/v) glucose, 750 ppm sodium nitrite, and appropriate levels of either Lactobacillus sakei LAD, L. sakei LAD plus Kocuria varians FT4 (formally Micrococcus varians), L. sakei LAD plus papain and GDL (glucono-delta-lactone) plus K. varians FT4, was injected to the muscle at a pumping rate 15% w/v. The effect of these treatments on the proteolysis in the ham system was compared to a control ham, produced without starter culture and containing GDL acidulant to control pH and antibiotics to reduce the contribution of background microflora. Hydrolysis of sarcoplasmic and myofibrillar protein fractions was evaluated by SDS-PAGE and reverse phase-HPLC. Hams with different treatments were also investigated for differences in amino acid profile, protein and non-protein nitrogen level, colour, pH, water activity and moisture and microbiological evolution. There was no significant difference in the gross compositional analysis of any of the treatments compared to the control. There was no significant difference ( p>0.05) in the protein content, non-protein nitrogen level, SDS-PAGE and free amino acid analysis between the control ham and ham inoculated with proteolytic starter culture. However, it was observed that hams containing starter cultures exhibited decreases in certain peptide fractions and corresponding increases in some free amino acids compared to the uninoculated control. It can be concluded that, while the principle mechanisms resulting in the proteolysis of this non-dried ham product involve the activity of endogeneous cathepsins, the addition of proteolytic starter cultures influence the amino acid profile thereby potentially enhancing the sensorial attributes of the ham.

Stability of soybean seed composition and its effect on soymilk and tofu yield and quality

Soymilk was made from 10 soybean [ Glycine max (L.) Merr.] lines grown at three locations for 2 years, using an 18:1 water/soy protein ratio. Tofu was made with either glucono-delta-lactone (GDL) or calcium sulphate dihydrate (CS). Genotype and year effects were substantially greater than location effects on soybean protein content and seed composition; soymilk and tofu yield, solids levels, and pH; and tofu colour, hardness, and firmness. Genotype by location and genotype by year interaction effects were minor relative to the genotype and year effects. Yield of soymilk, GDL tofu, and CS tofu, which averaged 7.39 l, 6.29 kg, and 6.15 kg per kg soybeans, respectively, were all positively correlated with seed protein and stachyose, and negatively correlated with seed oil, free sugar, sucrose and remainder content. Seed protein was positively correlated with tofu hardness and firmness, while seed oil, free sugar, sucrose, and remainder content were generally negatively correlated with tofu quality parameters. Results of stepwise regression analysis showed that seed protein was the major determinant of soymilk yield and solids content, while soymilk yield was, in turn, the major factor determining GDL tofu yield. Procedures used in making soymilk and tofu play a major role in determining which seed component has a major effect on soymilk and tofu yield and quality.

Influence of Milk-Clotting Enzyme Concentration on the αS1-Casein Hydrolysis During Soft Cheeses Ripening

We studied the influence of the dose of milk-clotting enzyme on αs1-CN degradation, soluble nitrogen production, and sensory profile for an Argentinean soft cheese: Cremoso Argentino. Five different types of cheeses were produced: 1) control cheeses with normal technology, 2) cheeses with inactivated milk-clotting enzyme, 3) cheeses with inactivated milk-clotting enzyme, without starter (acidified with glucono delta lactone), 4) cheeses with a half dose of milk-clotting enzyme, and 5) cheeses with a double dose of milk-clotting enzyme. Proteolysis was assessed by isoelectric focusing electrophoresis of the insoluble fraction at pH 4.6, followed by densitometric quantification. Soluble nitrogen at pH 4.6, expressed as a percentage of total nitrogen and defined as ripening index was also performed. A sensorial panel evaluated the cheeses at the end of ripening. The hydrolysis level of αs1-CN depended on the milk-clotting enzyme dose used in cheese making. Cheeses without active coagulant did not show degradation at the end of ripening, while cheeses with half and whole doses showed proportional degradations to coagulant dose. Cheese with a double dose of coagulant did not show higher αs1-CN hydrolysis than normal cheese. No difference was found between cheeses with and without microbiological starter, indicating that the selected culture, composed of thermophilic strains, was unable to attack the whole casein. A high linear correlation was found between ripening index and the relation%αs1−Iαs1−I+αs1.Sensorial characteristics of cheeses agree with objective analysis. Cheeses without active coagulant were hard and crumbly, while cheeses with normal dose were soft and creamy.

Mechanical properties and water-vapor permeability of soy-protein films affected by calcium salts and glucono-delta-lactone.

Edible films were prepared from solutions of soy protein with calcium salts and glucono-delta-lactone (GDL). Calcium salts cross-linking interactions with soy-protein isolate (SPI) could result in the formation of films with rigid three-dimensional structure. GDL contributed to the formation of a homogeneous film structure due to increased protein--solvent attraction. Tensile strength (TS) of calcium sulfate treated SPI film (8.6 MPa) was higher than the TS of calcium chloride treated SPI films (6.4 MPa) and the control SPI film (5.5 MPa). Puncture strength (PS) of calcium sulfate treated SPI film (9.8 MPa) was higher than the PS of calcium chloride treated SPI films (8.5 MPa) and the control SPI film (5.9 MPa). SPI film formulated with GDL had larger elongation at break (39.4%) than that of SPI control film (18.2%). Calcium salts and GDL-treated SPI films had lower water-vapor permeability than the SPI control film.

Rheological properties of milk gels formed by a combination of rennet and glucono-delta-lactone.

The effects of heat treatment of milk, and a range of rennet and glucono-delta-lactone (GDL) concentrations on the rheological properties, at small and large deformation, of milk gels were investigated. Gels were made from reconstituted skim milk at 30 degrees C, with two levels each of rennet and GDL. Together with controls this gave a total of sixteen gelation conditions, eight for unheated and eight for heated milk. Acid gels made from unheated milks had low storage moduli (G') of < 20 Pa. Heating milks at 80 degrees C for 30 min resulted in a large increase in the G' value of acid gels. Rennet-induced gels made from unheated milk had G' values in the range approximately 80-190 Pa. However, heat treatment severely impaired rennet coagulation: no gel was formed at low rennet levels and only a very weak gel was formed at high levels. In gels made with a combination of rennet and GDL unusual rheological behaviour was observed. After gelation, G' initially increased rapidly but then remained steady or even decreased, and at long ageing times G' values increased moderately or remained low. The loss tangent (tan delta) of acid gels made from heated milk increased after gelation to attain a maximum at pH approximately 5.1 but no maximum was observed in gels made from unheated milk. Gels made by a combination of rennet and GDL also exhibited a maximum in tan delta, indicating increased relaxation behaviour of the protein-protein bonds. We suggest that this maximum in tan delta was caused by a loosening of the intermolecular forces in casein particles caused by solubilization of colloidal calcium phosphate. We also suggest that in combination gels made from unheated milk a low value for the fracture stress and a high tan delta during gelation indicated an increased susceptibility of the network to excessive large scale rearrangements. In contrast. combination gels made from heated milk formed firmer gels crosslinked by denatured whey proteins and underwent fewer large scale rearrangements.

Effects of chemical hurdles on microbiological and oxidative stability of a cooked cured emulsion type meat product

Two combinations of hurdles, 2.0% lactate+0.5% acetate or 2.0% lactate+0.25 % glucono-delta-lactone (GdL), were both found to prevent growth of Listeria monocytogenes inoculated onto sliced saveloys manufactured with 60 or 150 ppm nitrite. The saveloys were packed in modified atmosphere (80% N 2/20% CO 2) using a film with low oxygen transmission rate (0.45 cm 3/m 2/atm/24 h) and stored at 5 or 10°C for up to 4 weeks. Changes in red colour (measured as Minolta a-values) and lipid oxidation [measured as thiobarbituric acid reactive substances (TBARS)] were low during storage at 5°C and unaffected by the storage conditions (±light). However, 2.0% lactate+0.25% GdL improved oxidative stability and led to significantly lower TBARS and significantly higher a-values. Levels of nitrosamines were low with values near the detection level. Although observed differences were small, members of a trained sensory panel were able to distinguish saveloys containing chemical hurdles from saveloys without. Judges most often mentioned flavour as being the deviating descriptor.