Thermal Effects on Fast Skeletal Myosins from Alaska Pollock, White Croaker, and Rabbit in Relation to Gel Formation

Thermodynamic properties in differential scanning calorimetry (DSC) and changes in viscoelasticity upon heating of myosins from white croaker, Alaska pollock, and rabbit fast muscles were investigated in relation to their thermal gel formation abilities. Alaska pollock myosin unfolded in a wide temperature range of 19 to 69°C as revealed by DSC, whereas rabbit myosin unfolded in very narrow range of 32 to 56°C. Thermal unfolding of white croaker myosin occurred in an intermediate temperature range of 30 to 60°C. Viscoelastic properties determined as storage modulus, G′, and loss modulus, G″, reflected differences observed in DSC for the 3 myosins.     

Thermal gelation of brown trout myofibrils from white and red muscles: effect of pH and ionic strength

The effects of pH and ionic strength on the thermal gelation of brown trout myofibrils from white and red muscles were analysed by thermal scanning rheometry. The highest gelation ability was obtained at low pH (around 5.6) whatever the ionic strength. No effect of ionic strength was observed at pH 5.6; however, at pH 6.0, lowering the salt (KCl) concentration to 0.3 M or less improved the characteristics of the gels formed. The effects of pH and ionic strength on myofibrils from both muscle types appeared to be similar, but red muscle proteins were less sensitive to changes in their physicochemical environment. Consequently, the differences between muscle types appeared to be dependent on pH and ionic strength. Solubility measurements revealed large differences between muscle types and between different pH values. Ultrastructural observations confirmed that different kinds of gels were formed depending on the physicochemical conditions and muscle type origin. © 2002 Society of Chemical Industry     

Effect of succinylation on the physicochemical,rheological, thermal and retrogradation properties of red and white sorghum starches

Starches isolated from red and white sorghum were modified with succinylation. After modification proximate composition, moisture content, ash, protein and fat were reduced in percentage. Increase in swelling power was observed and did not show any significant change in solubility. Swelling and solubility were pH dependent with higher values obtained at pH 12 in both native and modified starches. At pH 4 both succinylated red and white starches had lower solubility.     

Salt‐ and pyrophosphate‐induced structural changes in myofibrils from chicken red and white muscles

Myofibrils isolated from post‐rigor chicken Pectoralis major (PM, white) and Gastrocnemius (Gas, red) muscles were irrigated with various concentrations of NaCl (0.1–1.0 M ) with or without 10 mM sodium pyrophosphate at pH 5.5 and 6.0. Structural changes were examined using phase contrast microscopy. PM myofibril samples tended to show more definitive H‐zones but obscure Z‐lines compared to Gas myofibrils. Significant myofibril swelling, accompanied by a pronounced protein extraction, occurred in 0.5 M NaCl solution. The extent of swelling as well as protein extraction increased with the NaCl concentration up to about 0.8 M . Addition of pyrophosphate facilitated myofibril swelling and reduced the minimal NaCl concentration for swelling to 0.4 M . Without pyrophosphate, protein extraction for both PM and Gas myofibrils occurred along the A‐band, sometimes starting from the centre, but when pyrophosphate was added, the extraction began from the ends of the A‐band. At pH 5.5, protein extraction was similar for PM and Gas, but at pH 6.0, PM myofibrils were more extractable and their architecture changed more extensively than Gas myofibrils, especially when pyrophosphate was present. The results may explain the different water‐imbibing abilities of white and red meat when processed with salt and phosphate. © 2000 Society of Chemical Industry     

Dynamic rheological measurements on heat-induced myosin gels: Effect of ionic strength,protein concentration and addition of adenosine triphosphate or pyrophosphate

Myosin solutions and suspensions have been monitored during heating at pH 6.0 by using dynamic rheological measurements. The storage modulus (G′), the loss modulus (G) and the phase angle (δ) all showed a marked dependence on ionic strength in the temperature range 25–75°C. The filamentous gels (ionic strength <0.34) displayed a temporary reduction in G′ at temperatures between 50 and 60°C, presumably due to denaturation in parts of the rod portion of the myosin molecule. In the same temperature region the concentration dependence of G′ changed by a power of 2. The loss modulus also showed a marked concentration dependence, while the phase angle varied with concentration primarily at low (<50°C) temperatures. For the final gels, heated to 75°C, only G′ indicated marked differences due to different protein concentrations and ionic strengths; all gels were almost completely elastic (δ?1°). Adenosine triphosphate was shown to have a pronounced temporary effect on the filamentous gel formed at low temperatures, i.e. on the gel with the highest concentration dependence, while pyrophosphate had no such effect. However, both adenosine triphosphate (or rather its hydrolysis product: adenosine diphosphate) and pyrophosphate appeared to have a small, lasting effect on the heat-gelling ability of myosin: the former a detrimental effect, the latter an improvement.     

Properties, translucence, and microstructure of Pacific white shrimp treated with mixed phosphates as affected by freshness and deveining

ABSTRACT:  Effects of freshness and deveining on some properties, translucence, and microstructure of Pacific white shrimp ( Litopenaeus vannamei ) soaked in 2.5% NaCl containing different phosphates were studied. Shrimp soaked in all solutions had increases in weight gain and cooking yield with lowered cooking loss, compared with the control ( P < 0.05). However, efficacy of mixed phosphates in quality improvement of ice-stored shrimp was lower than fresh shrimp. Deveining resulted in increased weight gain and yield ( P < 0.05). Nevertheless, samples treated with phosphates became more translucent. Shrimp stored in ice for 7 d and treated with mixed phosphates were generally more translucent than fresh counterparts ( P < 0.05). Shrimp soaked in 2.5% NaCl containing 0.875% sodium acid pyrophosphate (SAPP) and 2.625% tetrasodium pyrophosphate (TSPP) were generally less translucent and had high weight gain and cooking yield along with low cooking loss. The microstructure study revealed that the muscle fibers were less attached with the loss of Z-disks after being treated with mixed phosphates. Cooked meats of fresh shrimp and ice-stored shrimp had more compact fiber arrangement with the shrinkage of sarcomere compared with raw samples. Disintegration was observed at the M-line in ice-stored shrimp treated with mixed phosphates after cooking, while such a phenomenon was not found in the cooked fresh sample treated with phosphates. T _max and enthalpy of both myosin and actin peaks shifted to lower values when shrimp were treated with mixed phosphates ( P < 0.05). Those changes were generally more pronounced in ice-stored shrimp. Therefore, freshness and deveining process had an impact on the quality of Pacific white shrimp treated with phosphates.     

Gelation process in two different squid (Dosidicus gigas) surimis throughout frozen storage as affected by several cryoprotectants: Thermal, mechanical and dynamic rheological properties

Differential scanning calorimetry (DSC) was used to follow the thermal denaturation of two differently processed surimis from giant squid (Dosidicus gigas), A (isoelectric precipitation) and B (acid washing). Both surimis were added with several cryoprotectants (sucrose, sorbitol and trehalose), and kept in frozen storage at −15 °C for 6 months. DSC profiles and transition enthalpies showed that protein quality was better in B than in A surimis whether fresh or frozen. It was also demonstrated that the sucrose-plus-sorbitol mixture and trehalose were the most efficient for preserving B and A type formulations respectively after frozen storage. Mechanical (puncture), small amplitude oscillatory (SAOS) and dynamic-mechanical thermoanalyses were performed on both gels from A and B series surimis throughout frozen storage. Gels from surimi A (GA) were considerably brittler than gels from surimi B (GB) and presented significantly lower strain amplitudes. Several correlations among different experimental data have been developed.     

The rheological properties of exudates from cured porcine muscle: effects of added carrageenans and whey protein concentrate/carrageenan blends

Meat exudates were collected from massaged cured porcine M semimembranosis using a model massaging unit. Exudates were used to observe changes in gelation properties of test exudates containing carrageenans and whey protein concentrate (WPC) and carrageenan blends. Three carrageenan powders iota (ι ), kappa (κ), as well as a kappa/locust bean gum mix, were assessed at a 1% residual level, both individually and as blends. WPCs assessed included high gelling A‐35, B‐75 and C 55% protein β‐lactoglobulin powders, as well as a regular 76% protein, WPC D. All WPCs were incorporated at a 2% residual powder level in the final meat. Treatment and control meat samples and resulting exudates were prepared in duplicate with analysis performed in triplicate. The viscoelastic properties of control and test meat exudate samples (n=6) were analysed using control stress rheology in oscillatory mode. All exudates were heated from 20 to 80°C at 1°C min⁻¹ , and subsequently cooled after 30 min back down to 20°C at 1°C min⁻¹. Combinations of high gelling WPCs, especially β‐lactoglobulin together with iota and kappa‐carrageenans A and B, were found to increase storage modules G′ (Pa) values when compared with control values. Significant (p<0.05) synergies were observed on blending high gelling WPCs with carrageenans A and B. © 1999 Society of Chemical Industry     

Milk fat globules by confocal Raman microscopy: Differences in human,bovine and caprine milk

Infant formulas are usually based on bovine milk and caprine milk. Pasteurization, homogenization and spray-drying are basic processes for the production of infant formulas. In this study, confocal Raman spectroscopy had been used to rapidly determine the differences between human, bovine and caprine milk fat globules (MFGs). The unsaturated fatty acids in human colostrum and mature MFGs were over 2 times more than in bovine and caprine MFGs. The phospholipid bands at 860 cm^− 1 of human colostrum MFGs were 5 times more than human mature, bovine and caprine MFGs. The carotenoid content varied according to the species of milk, with human MFGs containing more carotenoids than bovine and caprine MFGs. And the cholesterol content was not correlated with the size of the MFGs. Human MFGs were more mobile than bovine and caprine MFGs. The lipid composition and mobility of MFGs were underwent significant changes under different processing conditions. These results laid the foundations for the improvement and development of powdered milk formulas.     

Low-moisture part-skim mozzarella cheese made from blends of camel and bovine milk: Gross composition,proteolysis, functionality,microstructure, and rheological properties

Camel (CM) milk is used in variety of ways; however, it has inferior gelling properties compared with bovine milk (BM). In this study, we aimed to investigate the physicochemical, functional, microstructural, and rheological properties of low-moisture part-skim (LMPS) mozzarella cheese, made from BM, or BM mixed with 15% CM (CM15%) or 30% CM (CM30%), at various time points (up to 60 d) of storage at 4°C after manufacture. Low-moisture part-skim mozzarella cheeses using CM15% and CM30% had high moisture and total Ca contents, but lower soluble Ca content. Compared with BM cheese, CM15% and CM30% LMPS mozzarella cheese exhibited higher proteolysis rates during storage. Adding CM affected the color properties of LMPS mozzarella cheese manufactured from mixed milk. Scanning electron microscopy images showed that the microstructure of CM15% and CM30% cheeses had smooth surfaces, whereas the BM cheese microstructures were rough with granulated surfaces. Low-moisture part-skim mozzarella cheeses using CM15% and CM30% showed significantly lower hardness and chewiness, but higher stringiness than BM cheese. Compared with BM cheese, CM15% and CM30% cheeses showed lower tan δ levels during temperature surges, suggesting that the addition of CM increased the meltability of LMPS mozzarella cheese during temperature increases. Camel milk addition affected the physicochemical, microstructural, and rheological properties of LMPS mozzarella cheese.     

Removal of pesticides from red and white wine by the use of fining and filter agents

Effects of the use of the fining and filtration agents, diatomaceous earth, bentonite, polyvinylpoly-pyrrolidone and activated carbon, on the removal of seven fungicides (carbendazim, chlorothalonil, fenarimol, metalaxyl, oxadixyl, procymidone and triadimenol) and three insecticides (carbaryl, chlorpyrifos and dicofol) from wines were investigated. Carbendazim was determined by high performance liquid chromatography (HPLC) after quantitative conversion into 2-aminobenzimidazole (2AB). The concentrations of all the other compounds in wine were quantified using a multi residue assay involving solid phase extraction (SPE) and gas chromatography-mass spectrometry (GC-MS). After treatment and processing, conducted under conditions simulating those that are typical in Australian commercial winemaking, the greatest reduction in concentration in all treatments was for chlorothalonil, chlorpyrifos and dicofol. There was a significant relationship between the extent of removal of each pesticide and its solubility in wine, such that the lower the solubility, the greater the extent of removal. Activated carbon had the largest effect on the removal of most pesticides, while bentonite had a major effect on the removal of carbendazim. For all compounds and agents, the rate of removal was greater in white wine than in red wine.     

Characterisation of chickpea flour‐based gluten‐free batters and muffins with added biopolymers: rheological,physical and sensory properties

Chickpea flour (CF)‐based muffin formulations were made with CF alone and with added biopolymers [whey protein (WP), xanthan gum (XG) and inulin (INL)] to evaluate their suitability to be a wheat flour (WF) substitute in muffins. Structural characteristics of the batters and muffins were studied by means of rheometry, microscopy, physicochemical properties, and texture and sensory analysis. Partial replacement of CF with XG, alone (at 0.5 and 1%) or blended with either WP or INL, significantly increased the batter viscoelasticity as denser matrices developed; moreover, the muffins with XG added at 1% had similar hardness to wheat gluten muffins. The replacement of WF decreased the springiness, cohesiveness, chewiness, resilience and specific volume of the muffin. However, baked muffins with added XG also showed higher sensory sponginess and moisture associated with numerous air bubbles in the batter and were perceived to be easier to swallow and to have better general appearance.     

Nitrogen in browse species: ruminal degradability and post-ruminal digestibility measured by mobile nylon bag and in vitro techniques

This study determined nitrogen degradability and digestibility of rumen undegradable nitrogen using mobile nylon bag (MNB) and pepsin/pancreatin in vitro technique (IV) of 40 browse species. Thirty Ethiopian highland sheep fitted with rumen cannulae were used in nitrogen (N) degradability studies. Six steers fitted with rumen cannulae were used in preparation of 16-h and 24-h ruminal undegraded residues and four steers fitted with distal abomasal cannulae were used in MNB technique. The browses varied widely in nitrogen solubility (15–468 g kg⁻¹), potential degradability (223–976 g kg⁻¹), rate of degradation (0·13–24% h⁻¹) and effective degradability (135–821 g kg⁻¹). The apparent N digestibility (ND) of the rumen undegraded residues differed significantly (P<0·05) among browse species. No significant difference (P>0·05) was observed in ND of 16-h and 24-h residues. The ND of the 16-h residue varied from -218 to 759 g kg⁻¹ and 169 to 851 g kg⁻¹ for MNB and IV methods, respectively. Browse species with high tannin contents such as Acacia hockii, A horrida, A melanoxylon, A persiciflora, A salicina, A saligna and Flemingia macrophylla had high rumen by-pass and a low ND, while Sesbania spp and A nilotica with low tannin contents underwent rapid and extensive dry matter and nitrogen degradation in the rumen. Acacia sieberiana, Chamaecytisus palmensis, Erythrina spp, Gliricidia sepium, Samanea saman and Enterolobium cyclocarpum had high proportions of protein escaping rumen degradation (BP ) and with a high proportion of the by-pass protein digested in the intestine, therefore these browses had a high potential as protein supplements. The ND measured with the MNB were significantly lower (P<0·001) than by the IV method. The correlation between MNB and IV was high and significant (R²=0·89, P<0·0001) as also indicated by the regression equation (SE in parentheses): MNB=-22·8 (4·55)+1·0 (0·08)IV (RSD=10·56, R²=0·79, n=40, P<0·001). The intercept of the linear relationship obtained was different from zero while the slope was not different from unity. Multiple regression analysis suggested that some of the unexplained variation could be accounted for by either nitrogen, acid detergent fibre, total phenolics or neutral detergent fibre bound tannin levels in browses. The IV method is accurate for estimating digestibility of ruminally undegradable N, and hence its use would considerably reduce the need for delicate surgery and the elaborate procedures involving the MNB technique. © 1998 SCI.     

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

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

Reliability of ultrasonographic measurements of bovine sole structures in relation to sole horn thickness,measured by computed tomography,and sole horn hardness

The goal of the present study was to determine the effect of sole horn thickness (SHT) and sole horn hardness (SHD) on ultrasonographic visualization of sole structures in the inner and outer claws of 150 Holstein-Friesian cows, and to evaluate different ultrasound frequencies for this purpose. Ultrasonographic views of the sole structure were considered complete when 3 echogenic lines, representing the ventral surface of the sole horn, the borders of the sole horn and soft-tissue layer, and the ventral surface of the distal phalanx, were seen. The proportion of complete ultrasonographic views of the sole structures, designated as the ultrasonographic visualization proportion (UVP), and the measurement errors of SHT were evaluated by comparing images from computed tomography (CT) and ultrasonography. The latter images were generated using 3 different probes, frequencies of 6.5 and 5.0 MHz, and 2 different ultrasound machines (#1 and #2) to assess the apex, middle, and heel regions of the claws. The UVP were 60.8 to 77.9% for the 6.5-MHz probe in ultrasound machine #1 (probe A), which were lower than those (>90%) for both the 5.0-MHz probe in ultrasound machine #1 (probe B) and the 5.0-MHz probe in ultrasound machine #2 (probe C). The UVP was significantly lower in claws with an SHD ≥50 units than in claws with an SHD <40 or 40 to <50 units (UVP: 77.1% compared with 93.7 and 91.4%, respectively) when measured with probe B. In claws with an SHT <10 mm, the UVP was significantly lower when SHD was ≥50 units compared with <40 or 40 to >50 units; the values were 69.0% versus 91.3 and 85.9%, respectively, for probe A, and 89.7% versus 100 and 100%, respectively, for probe B. When SHT were measured by either probes A or B in ultrasound machine #1, the proportions of claws in which ultrasonographic values were within a ±1 mm range compared with the values obtained by CT were 84.9 to 91.3% for CT-determined SHT <5 mm, 66.7 to 71.9% for CT-determined SHT 5 to <7 mm, 28.9 to 51.2% for CT-determined SHT 7 to <10 mm, and 6.2 to 19.7% for CT-determined SHT ≥10 mm. The data indicated that increased SHT was associated with a decrease in ultrasonographic measurement accuracy. In claws with an SHT <5 mm, the high proportion of ultrasonographic values that were accurate within a ±1 mm range suggests that this imaging modality would be useful in cows with thin soles.     

Effect of different freeze drying cycle in Semimembranous and Gluteus Medius bovine muscles: changes on microstructure,colour, texture and physicochemical parameters

The aim of the present research was to evaluate effects of freeze drying cycle in Semimembranous and Gluteus Medius bovine muscles (sp: Aberdeen Angus) for instant meal. Samples were analysed by Scanning electron microscopy; texture and colour parameters were analysed by image analysis and physicochemical properties by instrumental assays. Micrographs revealed that a higher porous size structure and shrinkage of muscle fibre diameter were obtained at ?40 °C. In Semimembranous and Gluteus Medius bovine muscles, significant difference (P < 0.0001) was obtained for texture, colour and physicochemical parameters. Results revealed that colour, texture and physicochemical parameters were less affected when freeze drying cycle was performed at ?40 °C. Freeze drying cycle at ?50 and ?60 °C showed increases in lightness (L*) and yellowness (b*); decrease in redness (a*) and in water absorbing capability).     

Risk of disease from wildlife reservoirs: badgers, cattle, and bovine tuberculosis

Livestock face complex foraging options associated with optimizing nutrient intake while being able to avoid areas posing risk of parasites or disease. Areas of tall nutrient-rich swards around fecal deposits may be attractive for grazing, but might incur fitness costs from parasites. We use the example of dairy cattle and the risks of tuberculosis transmission posed to them by pastures contaminated with badger excreta to examine this trade-off. A risk may be posed either by aerosolized inhalation through investigation or by ingestion via grazing contaminated swards. We quantified the levels of investigation and grazing of 150 dairy cows at badger latrines (accumulations of feces and urine) and crossing points (urination-only sites). Grazing behavior was compared between strip-grazed and rotation-grazed fields. Strip grazing had fields subdivided for grazing periods of <24 h, whereas rotational grazing involved access to whole fields for 1 to 7 d each. A higher proportion of the herd investigated badger latrines than crossing points or controls. Cattle initially avoided swards around badger latrines but not around crossing points. Avoidance periods were shorter in strip-compared with rotation-grazing systems. In rotation-grazing management, latrines were avoided for longer times, but there were more investigative contacts than with strip-grazing management. If investigation is a major route of tuberculosis transmission, the risk to cattle is greatest in extensive rotation-grazing systems. However, if ingestion of fresh urine is the primary method of transmission, strip-grazing management may pose a greater threat. Farming systems affect the level and type of contact between livestock and wildlife excreta and thus the risks of disease.     

Cold,gel-like soy protein emulsions by microfluidization: Emulsion characteristics,rheological and microstructural properties,and gelling mechanism

In this paper we reported the rheological and microstructural properties of a kind of novel cold, gel-like soy protein isolate (SPI) emulsions obtained by means of microfluidization. These gel-like emulsions were formed from untreated and preheated (95 °C, 15 min) SPI at a protein concentration of 6% (w/v), and various oil volume fractions (Φ; 0.2–0.6) and NaCl concentrations (0–500 mM). The rheological properties and microstructure were characterized using steady viscosity and dynamic oscillatory measurements, as well as confocal laser scanning microscopy (CLSM). The characteristics (e.g. droplet size distribution and creaming stability) of the emulsions, formed at lower protein concentrations (e.g. 0.5–4.0%), were also characterized, aiming to reveal the mechanism of the gel-like network formation. The dynamic oscillatory data indicated that both untreated and preheated SPI emulsions exhibited gel-like rheological properties, but the specific apparent viscosity (η) and storage modulus (G′) of the latter ones were much higher at a comparable Φ. Both η and G′ progressively increased upon Φ increasing, indicating enhanced inter-droplet interactions. At a given Φ value (0.3), increasing NaCl concentration progressively increased η and G′ of the preheated SPI emulsions, indicating the importance of electrostatic screening for the gel-like network formation. The CLSM analyses confirmed formation of the gel-like network, mainly composed of aggregated oil droplets, which was closely dependent on the Φ and NaCl concentration. The gel-like network was formed by bridging flocculation of oil droplets, mainly through inter-droplet hydrophobic interactions between the proteins adsorbed at the interface. These results suggested that soy proteins exhibit excellent potential to produce cold, gel-like emulsions, especially through a heat pretreatment followed by microfluidization, which might be of vital importance for the development of soy protein-based formulations, especially as carriers for heat-labile ingredients with health effects.     

Kinetics of protein physicochemical changes induced by heating in meat using mimetic models: (2) Effects of fibre type,peroxides and antioxidants

Heating-induced changes in meat proteins were investigated using models made of aqueous suspensions of myofibrils according to muscle fibre types and cellular compounds (oxidants and antioxidants). These changes were evaluated by measurements of carbonyl groups and protein surface hydrophobicity. Model results were compared to trial results obtained on pork meat (M. Longissimus dorsi) heated under the same conditions (45 and 75 °C, from 5 to 120 min). Myofibrillar proteins from α-white fibres were more sensitive to oxidation and thermal denaturation than those from β-red fibres. At 45 °C, there were negligible differences due to peroxide or antioxidant types. At 75 °C, organic peroxides (ROOH) were less oxidative than hydrogen peroxide (H₂O₂), and antioxidant enzymes were less efficient than vitamin E and carnosine at protecting proteins against oxidation. Protein oxidation observed in meat is lower than in the mimetic models and the increase in hydrophobicity remained limited in meat.