RHEOLOGICAL CHARACTERIZATION OF KETCHUP

Ketchup flow properties were investigated with a concentric cylinder viscometer in the temperature range from 30°C to 80°C. A partial characterization of the product viscoelastic behavior at 30°C was also made by “Strain test” and “Frequency test.” The Harper and El Sahrigi equation (η_a= acβ e^Ea/RT), as well as the equation that links the apparent viscosity of ketchups to the serum viscosity and to the pulp content (η_a=η_serum+A(%P)^B), do not describe adequately the ketchup flow behavior that we found to be highly affected by the production technology and by the raw materials used.     

APPLICATION OF WLF AND ARRHENIUS KINETICS TO RHEOLOGY OF SELECTED DARK-COLORED HONEY

The rheological properties of Common Black Horehound, Globe Thistle, and Squill types of dark‐colored Jordanian honey were examined. The types of honey used were identified via assessing the source of nectar using pollen analysis (Melissopalynology). The apparent viscosity, η, was measured as a function of the shear rate, γ. In addition, the apparent viscosity was measured, at constant shear rate (6.12 s^?1), as a function of shearing time. Newton's law of viscosity (i.e., τ=ηγ) was found to adequately (R²～ 0.99) describe the flow behavior of honey samples. The apparent viscosity was found to decrease with temperature, and the temperature dependence of viscosity was contrasted versus both Arrhenius model (η=η_oe^Ea/RT) and WLF model (η/η_G= 10 (C₁(T–T)/C₂+(T–T_G))). Although Arrhenius kinetics may fit the viscosity versus temperature data for the examined types of honey, nevertheless, it gives a relatively high value of activation energy that is quite comparable with, if not even larger than, that of a typical chemical reaction. On the other hand, WLF‐model was found to adequately describe the data while at the same time it gives quite reasonable values of both T_G and η_G, which are in agreement with those cited in literature.     

Purification of New β-Galactosidase from Enterococcus faecium MTCC 5153 with Transgalactosylation Activity

A new β-galactosidase (β-gal) was purified from a lactic acid bacterial strain of Enterococcus faecium MTCC5153 by chromatographic techniques. The purified enzyme had a specific activity of 24.06 U/mg of protein with k _m and V_max values of 2 mM and 18.2 mM/min/mg of protein, respectively. The yield of purified β-gal was 10.65% and estimated molecular weight found to be ～90 kDa, consisting of two homodimeric subunits of 43kDa. The enzyme was stable in pH range of 8.0–9.0 with an optimum pH of 8 and the optimum temperature of 40°C. The enzyme was activated in the presence of metal ions such as Mg⁺², Mn⁺², Ca⁺², K⁺ and Na⁺ and was inhibited by Zn⁺², Co⁺² and Cu⁺². Chemical modifiers (N-bromosuccinamide and Diethylpyro carbonate) inactivated the enzyme indicating the role of tryptophan and histidine moieties for activity. The purified β-gal was able to synthesize oligosaccharides from lactose. This study suggests that the β-gal of Enterococcus faecium MTCC5153 could be applied in dairy industry for hydrolysis of lactose and to improve its digestibility. β-gal of probiotic cultures are of particular interest due to their transgalactosylation properties.     

Laboratory measurements of dry deposition of sulphur dioxide on to several soils from England and Wales

A laboratory method for measuring the dry deposition of sulphur dioxide (SO₂) on to soils is described. The effect of soil type on deposition velocity (v_g) was examined using samples of soils collected from 16 sites in England and Wales. Although the values of v_g measured for soils at field capacity did not differ significantly they were related to soil pH; thus they ranged from 0.422 cm s^?1 at pH 4.5 to 0.648 cm s^?1 at pH 7.5. Oven drying reduced v_g from an average value of 0.535 cm s^?1 for soils at field capacity to 0.264 cm s^?1. A large proportion of deposited SO₂ was recovered from the soil as sulphate S. At an atmospheric concentration of 36 μg SO₂ m^?3, about the mean for Great Britain, the input of sulphur through this process would be 10 kg ha^?1 in a 4-month fallow period.     

Physicochemical properties of starch isolated from Antiaris africana seeds in comparison with maize starch

Antiaris africana seeds yielded 29.6% starch which showed appreciable high contents of ash, protein, and fat. The average diameter of A. africana starch granules was 3.98 µm compared to 8.93 µm for maize starch. A. africana starch had a C‐type XRD pattern and crystallinity of 41.5%. A. africana starch had higher AM content (24.1%) than maize starch (20.9%). The gelatinization onset temperature of A. africana starch (66.7°C) was higher than maize starch (63.1°C), but its gelatinization temperature range (8.57°C) and enthalpy (13.97 J/g) were lower than the values for maize starch (14.02°C, 14.65 J/g). The pasting temperature (P_t) and setback (V_s) were lower and breakdown (V_b) higher for A. africana starch (P_t = 82.5°C, V_s = 173.8 RVU, and V_b = 121.42 RVU) than for maize starch (P_t = 84.9°C, V_s = 183.73 RVU, and V_b = 78.58 RVU). The GPC analysis gave M_w of 2.18 × 10⁷ g/mol and radius of gyration of 95.1 nm for Antiaris starch. Antiaris starch paste exhibited poor freeze‐thaw stability but its small granule size indicates potential for application as dusting starch.     

Bovine neuronal vesicular glutamate transporter activity is inhibited by ergovaline and other ergopeptines

l-Glutamate (Glu) is a major excitatory neurotransmitter responsible for neurotransmission in the vertebrate central nervous system. Vesicular Glu transporters VGLUT1 and VGLUT2 concentrate (50 mM) Glu [Michaelis constant (measuring affinity), or K_m, = 1 to 4 mM] into synaptic vesicles (SV) for subsequent release into the synaptic cleft of glutamatergic neurons. Vesicular Glu transporter activity is dependent on vacuolar H⁺-ATPase function. Previous research has shown that ergopeptines contained in endophyte-infected tall fescue interact with dopaminergic and serotoninergic receptors, thereby affecting physiology regulated by these neuron types. To test the hypothesis that ergopeptine alkaloids inhibit VGLUT activity of bovine cerebral SV, SV were isolated from cerebral tissue of Angus-cross steers that were naive to ergot alkaloids. Immunoblot analysis validated the enrichment of VGLUT1, VGLUT2, synaptophysin 1, and vacuolar H⁺-ATPase in purified SV. Glutamate uptake assays demonstrated the dependence of SV VGLUT-like activity on the presence of ATP, H⁺-gradients, and H⁺-ATPase function. The effect of ergopeptines on VGLUT activity was evaluated by ANOVA. Inhibitory competition (IC₅₀) experiments revealed that VGLUT-mediated Glu uptake (n = 9) was inhibited by ergopeptine alkaloids: bromocriptine (2.83 ± 0.59 μM) < ergotamine (20.5 ± 2.77 μM) < ergocornine (114 ± 23.1 μM) < ergovaline (137 ± 6.55 μM). Subsequent ergovaline kinetic inhibition analysis (n = 9; Glu = 0.05, 0.10, 0.50, 1, 2, 4, 5 mM) demonstrated no change in apparent K_m. However, the maximum reaction rate (V_max) of Glu uptake was decreased when evaluated in the presence of 50, 100, and 200 μM ergovaline, suggesting that ergovaline inhibited SV VGLUT activity through a noncompetitive mechanism. The findings of this study suggest cattle with fescue toxicosis may have a decreased glutamatergic neurotransmission capacity due to consumption of ergopeptine alkaloids.     

Fabrication of viscous and paste-like materials by controlled heteroaggregation of oppositely charged lipid droplets

This study describes the formation of materials with novel textural characteristics by controlled heteroaggregation of oppositely charged protein-coated lipid droplets. Heteroaggregation was induced by mixing a suspension of β-lactoglobulin (β-Lg)-coated lipid droplets (ζ = −51 mV, d₄₃ ∼ 0.35 μm, 20 wt.%) with a suspension of lactoferrin (LF)-coated lipid droplets (ζ = +32 mV, d₄₃ ∼ 0.35 μm, 20 wt.%) under conditions where the two proteins had opposite charges (pH 7). The mean particle size, flow behaviour, and shear modulus of the materials depended on positive-to-negative particle ratio (0–100%), pH (3–9), ionic strength (0–400 mM), and temperature (30–90 °C). The largest particle sizes, highest viscosities, and largest gel strengths were observed at intermediate particle ratios (40% LF:60% β-Lg), which was attributed to a strong electrostatic attraction between oppositely charged droplets (0 mM NaCl, pH 7, 25 °C). A reduction in particle aggregation, viscosity, and gel strength occurred at intermediate ionic strengths due to screening of the electrostatic attraction between oppositely charged droplets. However, increased aggregation, thickening, and gelation occurred at higher ionic strengths due to screening in electrostatic repulsion between similarly charged droplets. Thermal treatment of the samples (90 °C) promoted a substantial increase in gel strength due to protein denaturation and increased droplet attraction. This study has important implications for the utilisation of controlled particle aggregation to create novel structures in foods, cosmetics, personal care, and other products.     

Purification and Characterization of Polyphenol Oxidase from Hemşin Apple (Malus communis L.)

The polyphenol oxidase (PPO) enzyme was purified and characterized from Hem?in Apple (Malus communis L.), which was organically grown in Hem?in, in the Rize province of Turkey. Enzyme (PPO) activation was determined with catechol substrate. Apples were homogenized with homogenate buffer (pH 8.5). This process was followed by precipitation with (20–80%) saturated solid (NH₄)₂SO₄ and dialysis. Finally, purification with DE52-Cellulose ion-exchange and Sephadex G-25 columns was performed. Experiments were performed at an optimum pH (5.5) and optimum temperature (30–40°C). The kinetic and thermal parameters Km (3.40 mM), Vmax (333.3 EU/mL.min), Ea (3.57 kcal), ?H (2.968 kcal/mol), Q₁₀ (1.33), k_cat (24.57 min^?1) and V₀ (7.2x10³ mM^?1.min^?1) were assessed. Additionally, the effects of Mg²⁺, Pb ²⁺, Fe²⁺, Fe³⁺, Cd²⁺, Cu²⁺, Zn²⁺, Co²⁺, Al³⁺, Mn²⁺ and Na⁺ on enzyme activity was recorded, and the IC₅₀ values, K_? values and inhibition types were determined.     

Beta-Galactosidase of Streptococcus cremoris H

Beta-galactosidase (Beta-D-galactosidegalactohydrolase, EC 3.2.1.23) of Streptococcus cremoris H was partially purified by ammonium sulfate fractionation. Only 10% of the protein was recovered as enzyme protein and more than 50% of the enzyme in the crude extract was lost. A 2.6-fold purification only was achieved. The enzyme was most active at 65°C and recorded an optimum pH at 7.0. Km and V_max with ortho-nitrophenyl beta-D galactopyranoside as the substrate were recorded as 0.384 mM and 12.6 μmoles/mg protein/min. Manganese ions activated the enzyme. The enzyme was strongly inhibited by Hg⁺⁺, Ca⁺⁺, Ni⁺⁺, and Ag⁺ as well as parachloromercuribenoate.     

Effects of Substrate Densification and CO2 Conditions on Supercritical Extraction of Mushroom Oleoresins

The effects of densification of mushroom powders and of reduced density (p_r 1.15–1.45) and temperature (T_r, 1.105 – 1.195) of supercritical CO₂ (SCO₂) on solubilization of oleoresins were described by response surface methodology. Mushroom powder was compacted to specific volumes (v_d) between 0.825 and 1.125 mL/g and batch extracted with SCO₂ for 6 hr. The degree of solubilization (g oleoresin/100g solid) increased as p_r, T_r, or v_d increased. The effect of v_d was further studied for p_r= 1.45 and T_r= 1.197 using a 3-parameter diffusion model. It was postulated that a fraction of the oleoresin was easily extracted at a rate controlled by a diffusion coefficient of 1.0–1.5 × 10^?4 cm²/sec. The remaining constitutive and entrapped oleoresin was extracted at a rate regulated by a diffusivity 100 to 150 times lower, typical of diffusion through solids.     

Evaluation and Improvement of Extraction Methods for the Analysis of Aflatoxins B1, B2, G1 and G2 from Naturally Contaminated Maize

The extraction procedure for aflatoxin determination in maize is based on a methanol–water (8 + 2 v/v) or an acetone–water (85 + 15 v/v) mixture. Initially, the extraction efficiency of two solvents was evaluated for each aflatoxin. Different results were obtained for highly contaminated maize: significantly higher levels of aflatoxin B₁ were obtained by acetone–water, on the contrary higher levels of aflatoxin G₂ were achieved by methanol–water. Then, acetone–water mixtures in different proportions (7 + 3, 6 + 4 and 5 + 5 v/v) were tested to improve the extraction of aflatoxin G₂. Applying these extraction mixtures, the values both of aflatoxin B₁ and of other aflatoxins were generally higher compared to those obtained by acetone–water 85 + 15; moreover, acetone–water (6 + 4) and (7 + 3) showed the best extraction efficiency for all aflatoxins.     

Effects of physicochemical factors and in vitro gastrointestinal digestion on antioxidant activity of R‐phycoerythrin from red algae Bangia fusco‐purpurea

R‐phycoerythrin (R‐PE) was purified from the red algae Bangia fusco‐purpurea after 35–50% ammonium sulphate fractionation followed by ion‐exchange column chromatography on DEAE‐Sepharose, resulting in a purity (A₅₆₅/A₂₈₀) ratio of 5.1. The circular dichroism spectroscopy results suggested that the structure of R‐PE is predominately helical. The antioxidant activity of R‐PE was studied and revealed changes in conformation and antioxidant activity at different temperatures and pH values. After in vitro‐simulated gastrointestinal (GI) digestion of R‐PE, the scavenging activity of ABTS radical (EC₅₀, 769.9 μg mL^?1), DPPH radical (EC₅₀, 421.9 μg mL^?1), hydroxyl radical (EC₅₀, 32.4 μg mL^?1) and reducing power (A₇₀₀ = 0.5, 625.8 μg mL^?1) were measured. Gel filtration chromatography analysis showed that the molecular weight distribution of the final GI digest that still contained high antioxidant activity was <3 kDa. Our present results indicate that digestion‐resistant antioxidant peptides of R‐PE may be obtained by in vitro GI proteinases degradation.     

Structural and rheological properties of xanthan gum/lysozyme system induced by in situ acidification

Structural and rheological properties of xanthan gum/lysozyme (XG/Ly) system induced by electrostatic interaction through in situ acidification were investigated. The two biopolymers transited from co-solubility state to form soluble complexes, and finally produced tenuous network as the pH further decreased. The fluorescent images indicated that the network was cross-linked of XG chains by Ly, liking a polymerization process which resulted in the sol-gel transition by electrostatic interactions. High Ly content could accelerate the phase transition at the same pH condition, while XG played a contrary role. XG addition could enhance the thermal stability of Ly. The phase transition was also illustrated by ζ-potential at different pHs. The boundary parameters were determined to distinguish the phase transition regions. At the pH higher than pH_φ, the negatively liked XG and Ly were in co-soluble state. They formed soluble complexes at the pH between pH_φ and pH_g, and gel was obtained with net microstructure as the pH continuously decreased (lower than pH_g). The paper provides practical parameters that may be applicable in controlling the structure, texture, and stability of polysaccharide/protein system, as well as in food and medicinal application with various purposes.     

Purification and Properties of Beta-galactosidase from Streptococcus thermophilus

A β-galactosidase from Streptococcus thermophilus was purified to homogeneity by ammonium sulfate and acetone fractionation, gel filtration on Sephadex G-200, and ion exchange chromatography on DEAE-Sephadex A-50. The purified enzyme preparation exhibited an optimum pH at 6.6–7.0 and an optimum temperature of 57°C. The enzyme was stable at pH 6.8–7.0. Km and V_max for the enzyme, using ortho-nitrophenyl β-D-galactopyranoside as the substrate, were 0.25 mM and 83 μmoles/mg protein/min, respectively. It was strongly inhibited by Hg⁺⁺, Ag⁺, and Cu⁺⁺ as well as pchloro-mercuri benzoate. The enzyme had a molecular weight of about 6 × 10⁵ and was highly specific for β-galactoside bonds.     

Characterization of a β-Glucosidase from an Edible Mushroom,Lycoperdon Pyriforme

A β-glucosidase from Lycoperdon pyriforme, a wild edible mushroom, was characterized biochemically. The enzyme showed a maximum activity at pH 4.0 and 50°C when p-nitrophenyl-β-D-glucoside was used as a substrate. K_m and V_max values were calculated as 0.81 mM and 1.62 U/mg protein, respectively. The enzyme activity was conserved about 85% over a broad range of pH (3.0–9.0) at 4°C after 24 h incubation. The activity was fully retained after 60 min incubation at 20–40°C. Na⁺, Li⁺, Mg²⁺, Mn²⁺, Zn²⁺, Co²⁺, Ca²⁺, and Cu²⁺ did not affect the enzyme activity and 0.25% sodium dodecylsulfate inhibited the enzyme activity approximately 76%. Ethylenediamine tetra-acetic acid, phenylmethanesulfonylfluoride, and dithiothreitol showed no or a little negative effect on the enzyme activity. The resistance of the enzyme to some metal ions, chemicals, and ethanol along with the pH stability, can make it attractive for future applications in industry.     

Aflatoxins in composite spices collected from local markets of Karachi,Pakistan

This survey was carried out to evaluate the occurrence of total aflatoxins (AFs; B₁+B₂+G₁+G₂) in unpacked composite spices. A total of 75 samples of composite spices such as biryani, karhai, tikka, nihari and korma masalas were collected from local markets of Karachi, Pakistan, and analysed using HPLC technique. The results indicated that AFs were detected in 77% (n = 58) samples ranging from 0.68 to 25.74 µg kg^?1 with a mean of 4.63 ± 0.95 µg kg^?1. In 88% (n = 66) samples, AFs level was below the maximum limits (ML = 10 µg kg^?1) as imposed by EU. Furthermore, 61% (n = 46) tested samples contained AFs level between 1 and 10 µg kg^?1, 9% (n = 7) exhibited AFs contamination ranged 10?20 µg kg^?1 and only 3% (n = 2) of the investigated samples contained AFs levels higher than the ML of 20 µg kg^?1 for total aflatoxins as set by the USA. It was concluded that there is need to establish a strict and continuous national monitoring plan to improve safety and quality of spices in Pakistan.     

Bubble stability in the presence of oil-in-water emulsion droplets: Influence of surface shear versus dilatational rheology

We discuss the stability of bubbles to coalescence when undergoing a pressure drop and their stability to disproportionation under quiescent conditions, studied using previously established ‘single bubble layer experimental’ techniques, focussing on the effects on stability of the inclusion of a low volume fraction (0.25%) of stable oil droplets. Detailed measurements of the surface dilatational elasticity (?_s) and surface shear viscosity (η_s) of systems in the presence and absence of oil droplets have been performed. The surface rheology and stability have been measured as a function of adsorption time and pH, between pH 4.5 and 7, by including glucono-δ-lactone (GDL) as an acidification agent. Commercial sodium caseinate (SC) and purified β-lactoglobulin (β-L) were used at 1 wt% bulk concentration as bubble stabilizing agents. The emulsion oil droplet phase was n-tetradecane (TD) or 1-bromohexadecane (BHD), with a mean droplet size of (d₄₃) = 0.59 and 0.67 μm, respectively. The emulsion droplets were completely stable to coalescence and did not enter or spread at the air–water (A–W) interface. With SC at all pH values the values of η_s were markedly higher in the presence of TD droplets than in their absence, but particularly when the pH was lowered to pH ≤ 5.5 such that the SC started to aggregate. The increase in η_s correlated with the increase in coalescence stability under the same conditions. With neutrally buoyant BHD droplets the increase in η_s was not as great, but η_s was still significantly higher than in the absence of droplets, indicating that the rise to, and packing of, TD droplets at the A–W interface due to gravity was not solely responsible for their observed effects. The values of ?_s did not increase much at all for either β-L or SC as the pH was lowered and/or TD droplets were added, except at very low pH values, when the effects with SC were obscured by the tendency for the bulk SC to gel. In agreement with the relatively insignificant changes in ?_s as the pH was lowered or droplets were added, the resistance to disproportionation of bubbles did not change very much either.     

Rheological properties of cereal starch gels and Mesona Blumes gum mixtures

The effect of Mesona Blumes gum (MBG) was examined on steady and dynamic shear of MBG/rice starch and MBG/wheat starch gels. In addition, stress relaxation and creep tests were performed for two types of cereal starch gels. The flow curves of both MBG/starch gels exhibited pseudoplastic behavior at shear rates between 0.01 and 10 s⁻¹, and the data were fitted into the power law model (R² = 0.91–0.98). Dynamic mechanical spectrum showed that all gels were strong gels in frequency between 0.1 and 10 Hz. Stress relaxation data at different strains indicated a strain‐softening phenomenon for both gels. Data were fitted into Maxwell model (R² = 0.91–0.98). Creep curves were conducted at the shear stress 6.4 Pa within linear viscoelastic region of both MBG/starch gels. Data were fitted into Burgers model (R² = 0.91–0.98). Apparent viscosity η, storage moduli G′, equilibrium stress relaxation modulus G_e and zero apparent viscosity η₀ of MBG/rice starch gels decreased in the following order: 6/0>6/0.5>6/0.35>6/0.1 (starch/gum w/w). Whereas η, G′, G_e, and η₀ of MBG/wheat starch gels increased gradually along side the increase of MBG contents. The stress relaxation time λ of MBG/rice starch gels increased in the following order: 6/0<6/0.5<6/0.35<6/0.1 (starch/gum w/w) while λ of MBG/wheat starch gels decreased gradually with the increase of MBG level. The influence of MBG on two examined cereal starch is totally opposite.     

Direct Determination of Molybdenum in Milk and Infant Food Samples Using Slurry Sampling and Graphite Furnace Atomic Absorption Spectrometry

A fast and efficient method to determine molybdenum, Mo, in milk and other infant food by atomic absorption spectrometry with electrothermal atomization employing slurry sampling was developed. Slurries were prepared in ultrapure water with 5 to 20 min of sonication in concentrations of 10% w/v. The injection of 5.0 μL of a 0.1% (v/v) cetyl trimethyl ammonium chloride solution before the temperature program reduced the effect of build-up of carbonaceous residues within the atomizer. Europium (chemical modifier) and niobium (permanent modifier) were chosen for use from several potential modifiers. The parameters of merit were obtained in the optimized conditions T _a  =  2,700 oC, T _p  = 2,000 oC, tp = 20 s, and Eu 5.0 μg + permanent Nb 500.0 μg. These parameters were linear working range up to 100.0 μg/L, limit of detection (1.1 ± 0.1) μg/L, aqueous calibration, and standard addition curves with r ² > 0.9900 and relative standard deviation of 0.6% to 8.7%. The accuracy was evaluated by recovery tests and by certified material analysis; the agreement among these numbers validated the method. The powdered sample concentrations were between 39 and 1,570 μg/kg.     

Control of milk acidity by photoluminescence

For a quality assessment of milk and dairy products, the optical methods are used. In this paper, the use possibility is investigated of the optical method of photoluminescence for the milk acidity value finding out. The spectral measurements were carried out on a diffraction spectrofluorimeter in the range of 200–500 nm. The milk acidity measurement accuracy was controlled by the titrimetric method. It is established that as far as milk sours, the excitation spectra in the range of 200–500 nm decrease; but there are qualitative changes in the range of 350–500 nm. With acidity growth, the photoluminescence flux decreases if it is excited by the radiation value λ_e = 262 nm, grows at λ_e = 385 nm and decreases at λ_e = 442 nm. It is advisable to control the milk acidity in terms of the photoluminescence fluxes ratio Φ₃₈₅/Φ₄₄₂. The linear approximation of the function Φ₃₈₅/Φ₄₄₂(K) is statistically reliable (the determination factor R² = 0.99).