Kinematic viscosity and water activity of aqueous solutions of glycerol and sodium chloride

During osmotic dehydration, a removal of water from foodstuffs is achieved with a decrease in the water activity of the food sample. This dehydration process involves the utilization of highly concentrated solutions with one or several solutes that increase considerably the viscosity of the liquid phase. This property is fundamental in the studies of mass and momentum transfer processes. Glycerol and sodium chloride are studied as systems employed in this type of process due to the advantages for the final dehydrated product. Kinematic viscosities of binary and ternary aqueous solutions of these solutes were measured at various concentrations (from 0 to up 5.0 mol kg^–1) and temperatures (from 20 up to 50 °C). Water activities for each indicated solution at 25 °C are also reported. Experimental data for both physical properties were simultaneously correlated with concentration and temperature for binary and ternary solutions with a suitable accuracy. Additionally, relationships between kinematic viscosities and water activities were established.     

Sensory properties of some synthetic high‐intensity sweeteners in water solutions

BACKGROUND: When sucrose is eliminated from products to meet consumers' demand for calorie‐free products and substitutes are used, sweetness becomes an important characteristic. The objective of this study was to compare sensory properties of four sucrose substitutes: aspartame, acesulfame K, sodium saccharin and sodium cyclamate in water solutions. RESULTS: The lowest concentrations of sweeteners such as 0.35 g kg^?1 for aspartame and acesulfame K showed an equi‐sweet level relative to approx. 55 g kg^?1 aqueous sucrose solution, whereas 2.3 g kg^?1 sodium cyclamate and 0.4 g kg^?1 sodium saccharin relative to approx. 65 g kg^?1. Aspartame had almost the same sweetness potency as acesulfame K, whereas the remaining sweeteners differed completely. The four sweeteners showed their specific sensory profiles. Besides the characteristics of sweetness and bitterness, metallic and astringent attributes plus warming and cooling effects were found. CONCLUSIONS: Of the four sweeteners, aspartame and sodium cyclamate can be considered as the best sucrose substitutes due to their similar sensory profiles to the sucrose. The data showing the interdependence between sweetness intensity of the sweeteners and sucrose are useful as a quick and easy indicator of the sweetener amount having equi‐sweet levels relative to sucrose. Copyright © 2009 Society of Chemical Industry     

Water activity at 35 °C in 'sugar ' + water and 'sugar ' + sodium chloride + water systems

Water activities of aqueous solutions of xylose, glucose, fructose and sucrose, and of these sugars with sodium chloride, were measured and correlated with a simple empirical equation proposed by Lin et al . (1996) . Parameters for the equation were obtained and, from them, values of water activity were calculated with an average relative deviation of less than 0.14% for all the systems studied.     

Kinematic Viscosity of Ternary Aqueous Solutions of Ethanol and Sucrose

A capillary viscosimeter was used to measure the kinematic viscosity data of aqueous solutions of ethanol and sucrose at several temperatures (from 20 up to 45°C) and concentrations (from 5% up to 95.11% w/w ethanol concentration with variable sucrose concentrations as a function of its solubility). Two models were proposed for fitting the experimental data (one for water/ethanol and another for water/ethanol/sucrose solutions). These models were based in pre-existing equations like Redlich-Kister and Torok-Rard-Miller (for dependency on concentration), and also Vogel-Fulcher-Tamman (for dependency on temperature). The estimated values by these two models gave low deviations from the experimental data for binary and ternary mixtures.     

Effect of substituting fresh‐cut perennial ryegrass with fresh‐cut white clover on bovine milk fatty acid profile

BACKGROUND

Including forage legumes in dairy systems can help address increasing environmental/economic concerns about perennial ryegrass monoculture pastures. This work investigated the effect of substituting fresh‐cut grass with increasing quantities of fresh‐cut white clover (WC) on milk fatty acid (FA) profile and transfer efficiency of dietary linoleic (LA) and α‐linolenic (ALNA) acids to milk fat. Three groups of three crossbred dairy cows were used in a 3 × 3 crossover design. Dietary treatments were 0 g kg^?1 WC + 600 g kg^?1 grass, 200 g kg^?1 WC + 400 g kg^?1 grass, and 400 g kg^?1 WC + 200 g kg^?1 grass. All treatments were supplemented with 400 g kg^?1 concentrates on a dry matter basis. Cows had a 19‐day adaptation period to the experimental diet before a 6‐day measurement period in individual tie stalls.

RESULTS

Increasing dietary WC did not affect dry matter intake, milk yield or milk concentrations of fat, protein or lactose. Milk polyunsaturated FA concentrations (total n‐3, total n‐6, LA and ALNA) and transfer efficiency of LA and ALNA were increased with increasing dietary WC supply.

CONCLUSION

Inclusion of WC in pastures may increase concentrations of nutritionally beneficial FA, without influencing milk yield and basic composition, but any implications on human health cannot be drawn. © 2018 The Authors. Journal of the Science of Food and Agriculture published by JohnWiley & Sons Ltd on behalf of Society of Chemical Industry.

     

Study of two different cold restructuring processes using two different qualities of hake (Merluccius capensis) muscle,with addition of microbial transglutaminase

BACKGROUND: Microbial transglutaminase (MTGase) can improve the mechanical and functional properties of restructured fish products without the need of thermal gelation. The present study seeks to determine whether, for different setting times, MTGase activity in restructured hake muscle made with pieces or with homogenised muscle can be affected by the quality of the protein in the raw materials. RESULTS: As regards mechanical properties, samples of both qualities subjected to the two different processes attained a suitable consistency after setting for 24 h at 5 °C. The quality of the protein in the sample is important when pieces are used for restructuring, but not when sample is homogenised. Also, there were strong correlations between residual MTGase activity up to 12 h and mechanical properties and electrophoretic band density. Water binding capacity (WBC) was not significantly altered by MTGase addition. CONCLUSION: The experimental combination of 10 g kg^?1 of MTGase, 15 g kg^?1 of sodium chloride and 7.5 g kg^?1 of sodium caseinate was suitable for the production of minimally processed raw restructured fish products made with two different qualities of fish protein and two different restructuring processes. In the restructured products made with pieces, the protein quality significantly affected final properties, but in finely homogenised product the protein quality was less important. Copyright © 2009 Society of Chemical Industry     

Kinematic Viscosity of Aqueous Solutions of Ethanol and Glucose in the Range of Temperatures from 20 to 45°C

The purpose of this investigation was to determine, using a capillary viscosimeter, kinematic viscosity data of aqueous solutions of ethanol and glucose, at several temperatures (from 20 up to 45ºC) and concentrations. Glucose solubility strongly depended on ethanol concentration allowing the kinematic viscosity study (from 5% up to 45% w/w ethanol concentration with variable glucose concentrations as a function of its solubility). Kinematic viscosity modelling with solution concentration and temperature simultaneously, based on previous models for respective binary systems, was successfully carried out. The estimated values by this model give low average deviations (2.62%) from the experimental data. Glucose solubility (at 25ºC) in alcohol solutions and index of refraction (at 20ºC) of ternary solutions were also determined and empirical models are proposed in order to evaluate both physical properties with high (R² > 0.993 and >?0.991, respectively) accuracy.     

Amino Acid-Lactose Interactions and Their Sensory Consequences

The effects of twelve possible sweetness potentiators, L-alanine, glycine, D-leucine, D-phenylalanine, L-phenylalanine, D-tryptophan, L-tryptophan, Maltol, Ethyl Maltol, β-D-fructose, anhydrous α-D-glucose, and sodium chloride upon lactose were investigated using a trained sensory panel and magnitude estimation. Specific levels of each potentiator were added to five concentrations of lactose arranged in a geometrical progression within the range of 6 × 10^?2 to 3 × 10^?1M. The monosaccharides were evaluated separately within the range 3 × 10^?2 to 3 × 10^?1M and in combination with lactose. Additivity and synergism were tested using two mathematical models. Of the potential synergistic agents (PSA) examined, D-tryptophan was the only one to demonstrate possible synergistic properties. When studied using an expansion of the equation, S = KCⁿ, no clear evidence of synergism was found. Three types of response to PSA-lactose combination were observed. The combination may be strictly additive, lactose may depress sweetness at low concentrations, or the rate of change relating concentration to response may not be constant across the concentration range tested.     

Prediction of Lactose Crystals Present in Supersaturated Lactose and Whey Solutions by Measuring the Water Activity

Linear models based on water activity measurement were developed to predict the crystalline fraction of lactose present in the supersaturated crystal-solution mixture of lactose and whey. By this method, it was possible to measure the crystalline fraction in the mixture even if the sample is opaque or coloured, which would be difficult to measure by the conventional refractometric method. To calculate the fraction of lactose crystallized, the differential water activity of the crystallized mixture and non-crystalline supersaturated solution needs to be determined. For the pure lactose, the predictive linear equation was Δ?L = 1874.4 Δ?a_w, whereas for whey it was Δ?L = 1155.2 Δ a_w, where Δ L is the amount of α-lactose monohydrate crystals (g 100g^?1 water) that is in the crystallized solution, and Δ a_w is the differential water activity after and prior to crystallization. Other equations such as Raoult's. Norrish, and Money-Born were also tested to predict the water activity of supersaturated solutions of lactose or whey.     

Effects of methionine addition in soya bean or casein diets supplemented with carrageenan on weight gain and blood lipids in rats

Seven groups of 12 Wistar rats were fed during two experimental periods. During the first period of 4 weeks, rats were fed diets containing 100 g kg^?1 of casein or soya-protein. In the case of casein, diets contained casein, casein + 3.5 g kg^?1 of sodium carrageenan and casein + 3.5 g kg^?1 of sodium carrageenan + 1 g kg^?1 of DL-methionine. In the case of soya protein, diets contained soya protein, soya protein + 6.2 g kg^?1 of sodium carrageenan, soya protein + 6.2 g kg^?1 of sodium carrageenan + 1 g kg^?1 of DL-methionine and soya protein + 1 g kg^?1 of DL-methionine. During the second period of 8 weeks, all rats were fed laboratory pellets containing 170 g kg^?1 of standard protein mixture. Methionine supplementation of heated soya bean meal containing carrageenan prevented the decrease of growth observed with unsupplemented diet. Methionine supplementation of casein improved protein efficiency ratio and had no effect on long-term growth of rats because carrageenan did not cause growth retardation. At the end of second period, carrageenan ingested during the first period had no effect on plasma cholesterol. When carrageenans added to casein were ingested during the first period, plasma triglycerides were significantly lower after the second period. It would seem that carrageenans induce protein malnutrition by a lack of methionine when they are present in low protein diets with low methionine content, and that a sufficient content of methionine in diets prevents the carrageenan effect.     

Activity coefficients in the evaluation of food preservatives

Food preservatives are used in very low concentrations. However, usually they are used in aqueous high ionic strength solutions. The Pitzer model allows activity coefficient determination in these cases. Without the knowledge of activity coefficients, activity or ‘correct concentration’ cannot be known. In this work, the activity coefficients of sodium chloride, potassium chloride and calcium chloride in pure solutions were calculated by the Debye–Hückel theory and the Pitzer theory. The calculated values were compared with experimental values. Activity coefficients of pure sodium benzoate in aqueous mixed solutions with potassium chloride or calcium chloride were evaluated using the Pitzer model. The same evaluation can be done to more complex systems once all Pitzer parameters values for the ionic species are known.     

不同盐溶液漂洗对带鱼鱼糜凝胶强度及其挥发性风味的影响

以鱼糜盐溶蛋白相对含量、凝胶强度、鱼肉漂洗损失率为指标,选取不同浓度的盐溶液漂洗带鱼鱼肉,结合电子鼻和GC-MS研究不同盐溶液对带鱼鱼糜凝胶特性及其风味的影响。鱼肉漂洗液的盐浓度均对鱼肉漂洗效果产生影响,四种盐溶液漂洗鱼肉的合适浓度分别为:0.3%Na Cl、0.06%Ca Cl2、0.5%Na HCO3或0.5%柠檬酸钠;电子鼻分析显示,对照组与盐溶液漂洗后得到的鱼糜风味主成分分析(PCA)图区分明显,没有任何重叠,而Ca Cl2、Na Cl或Na HCO3溶液处理后的鱼糜PCA图有较多重叠;采用GC-MS分析,在对照组、Na Cl、Ca Cl2、Na HCO3、柠檬酸钠溶液漂洗所制得鱼糜中,分别检出51、36、40、38、56种挥发性成分,并以醛、酮、醇类为主;与对照组相比,盐溶液漂洗后鱼肉中的挥发性酸类物质被去除,酯类物质都有所增加,Ca Cl2溶液组中烷烃和烯烃类物质有明显增加,而Na Cl、Na HCO3、柠檬酸钠溶液组明显增加的分别是酮、醇、醛类物质。     

Kinetics of degradation of sorbic acid in aqueous glycerol solutions

Degradation of sorbic acid in aqueous glycerol solutions at pH 4·0 over the a_w range 0·71–1·00 and the temperature range 40°–60°C was found to follow first-order reaction kinetics and to conform to the Arrhenius equation. Activation energy values obtained were 5·8 kcal mol^?1 and 7·8 kcal mol^?1 for systems at 0·80 a_w with and without added Co⁺⁺, respectively. The rate of sorbic acid degradation was observed to increase with decreasing a_w (i.e. increasing glycerol concentration). The presence of added Co⁺⁺ decreased the rate of sorbic acid breakdown at any particular a_w or temperature. Browning of sorbate solutions during storage was markedly inhibited by Co⁺⁺.     

Chemical properties and sensory quality of ice cream fortified with fish protein

BACKGROUND: Fish protein powder is a functional ingredient that can be used for enhancing the nutritional value of food products. In this study the effect of fortification with different levels of fish protein powder (FP) on chemical properties and sensory quality of Persian ice cream with 0, 30 and 50 g kg^?1 FP during storage at ? 18 °C for 4 months was investigated. RESULTS: Ice creams fortified with 50 and 30 g kg^?1 FP had significantly higher protein and solid‐non‐fat content than ice cream with 0% FP or 83, 69 and 51 g kg^?1 protein and 215, 204 and 181 g kg^?1 solid non‐fat, respectively. All products had the same levels of fat, lactose, acidity and pH. They had similar sensory quality after production except for colour, but sensory properties of fortified samples changed significantly after 2 months of storage. Colour faded, cohesiveness decreased, sandiness/coarseness increased, sweetness decreased and fish flavour and off‐odour increased. The control ice cream scored highest for additives odour and flavour. CONCLUSION: Development of ice cream fortified with fish protein powder could be an effective way to enhance nutritional and functional value of ice cream. But studies on storage stability, consumers' acceptance and attitudes are recommended if companies are planning to do so. Copyright © 2011 Society of Chemical Industry     

Reduction of sodium and increment of calcium and ω‐3 polyunsaturated fatty acids in dry fermented sausages: effects on the mineral content,lipid profile and sensory quality

BACKGROUND: A combined technological approach was applied in the development of healthier dry fermented sausages: a partial substitution of the pork back fat by pre‐emulsified linseed oil and a partial replacement of sodium chloride with calcium ascorbate at two different levels, leading to low amounts of salt (14gSalt and 10gSalt, with 14 g and 10 g NaCl per kg of mixture, respectively). RESULTS: The developed products (14gSalt and 10gSalt) showed adequate results for a_w (0.85 and 0.87) and pH (4.98 and 5.21), and low lipid oxidation values (1.4 × 10^?4 and 1.5 × 10^?5 g malondialdehyde (MDA) kg^?1). The lipid modification led to a significantly higher supply of ω‐3 (23.3 g kg^?1) compared to the control (3.2 g kg^?1). Simultaneously, reductions of 38% and 50% in sodium content and a calcium supply of 4 and 5.2 g kg^?1 were achieved in the 14gSalt and 10gSalt formulations, respectively, compared to the control products (26 g salt and 0.87 g kg^?1 Ca). Instrumental analysis of colour and texture and sensory studies demonstrated that the organoleptic quality of the new formulations was similar to that of traditional products. CONCLUSIONS: The developed dry fermented sausages showed healthier properties than traditional ones owing to their reduced sodium and higher calcium content and a significant supply of ω‐3 fatty acids. © 2012 Society of Chemical Industry     

The effect of casein on the viscosity of solutions of hydrocolloids

The apparent viscosities of aqueous solutions of guar gum, locust bean gum, sodium carboxymethylcellulose and k-carrageenan have been measured over a range of shear rates from 14 to 1142 s^?1. Comparable measurements were made on solutions to which different quantities of casein (10-40 g litre^?1) had been added. For all the solutions a power law equation describes the variation of relative viscosity with shear rate. Addition of casein has no effect on the solutions of guar and locust bean gum, but does affect the rheology of solutions of sodium carboxymethylcellulose and k-carrageenan. The behaviour of k-carrageenan indicates a dependence on the polyanion:casein ratio, reaching a maximum at a concentration ratio of 1:4. The only significant solute-solute interactions in the hydrocolloid-casein solutions are electrostatic in nature.     

Taste recognition threshold concentrations of styrene in oil-in-water emulsions and yoghurts

Taste recognition threshold concentrations (TRTC) of styrene were determined in samples of oil-in-water emulsions (30–300 g kg^?1 oil) and yoghurts (1–30 g kg^?1 fat), spiked with styrene. The observed TRTC increased linearly with increasing fat content and ranged from 0–3 to 2–1 mg kg^?1 for the emulsions and from 36 to 171 g kg^?1 for the yoghurts. Styrene equilibrium partition coefficients between emulsions and their respective vapour phases were determined. The concentrations of styrene in the continuous aqueous phase of the emulsions and yoghurts were calculated at the TRTC. The styrene concentrations in the continuous phase had constant values of about 15 g kg^?1 indicating that perception of styrene for oil-in–water emulsions is determined by the aqueous phase of the emulsion. The concentrations of styrene in the vapor phases above the emulsions and yoghurts were also calculated and were found to be constant at the TRTC. This relationship probably resulted from the equilibrium of distribution of styrene between the respective phases. Commercial yoghurt packed in polystyrene beakers contained styrene levels in the range 2–11 g kg^?1, much lower then the TRTC reported.     

Dielectric properties of frozen maltodextrin solutions with added NaCl across the glass transition

The change in the dielectric properties of frozen 200 g kg^?1 maltodextrin solutions upon warming has been recorded using a capacitance meter and a dielectric thermal analysis instrument. The capacitance and permittivity increased by several orders of magnitude after melting, and higher values were obtained at a higher measurement frequency or with added NaCl, while a marked increase (labelled T_rise) was seen close to the glass transition temperatures measured by differential scanning calorimetry. The transition temperatures shifted to more negative values by 4–6 °C upon the addition of 0.1 mol kg^?1 NaCl, consistent with the freezing point depression of the freeze‐concentrated solutions. Copyright © 2004 Society of Chemical Industry     

Effect of calcium salts on the texture,structure and sensory acceptance of osmotically dehydrated guavas

The effect of additives, calcium chloride and calcium lactate (5–25 g kg^?1), on the osmotic dehydration of guavas with sucrose solutions was studied, aiming at the structural preservation of processed fruits. The osmotic process was evaluated from the reduction in weight of the guavas, water loss and solids gain, and the samples were analyzed with respect to calcium content, texture (stress and strain at failure, relaxation time and residual stress), structure by light microscopy and sensory acceptance. Calcium salts had a strong influence on the texture and structure of the processed guavas, resulting in the maintenance of tissue structure when calcium lactate was used at concentrations up to 15 g kg^?1, and calcium chloride was used at 5 g kg^?1. The sensory acceptability of guava was related to the structural and texture results. Calcium treatments did not improve guava's sensory acceptance. Guavas treated with calcium lactate showed good sensory acceptance, presenting slight inferior scores only at concentrations above 20g kg^?1, while CaCl₂ treated guavas showed average scores statistically equal to the sucrose and calcium lactate treated fruits only at 5 g kg^?1. Copyright © 2007 Society of Chemical Industry     

Antihyperlipidaemic effect of Aegle marmelos fruit extract in streptozotocin‐induced diabetes in rats

The present study determines the effect of an aqueous extract of Aegle marmelos fruits on serum and tissue lipids in experimental diabetes. Albino Wistar rats were rendered diabetic by intraperitoneal administration of streptozotocin (45 mg kg^?1). Serum and tissue lipids such as total cholesterol, triglycerides, free fatty acids and phospholipids were elevated in diabetic rats. Oral administration of A marmelos fruit extract at doses of 125 and 250 mg kg^?1 to diabetic rats twice daily for 1 month led to a significant lowering of these lipids in diabetic rats. The effect exerted by the fruit extract at a dose of 250 mg kg^?1 was greater than that of the dose of 125 mg kg^?1 or of glibenclamide (300 µg kg^?1). The results of this study demonstrate that an aqueous A marmelos fruit extract exhibits an antihyperlipidaemic effect in streptozotocin‐induced diabetic rats. Copyright © 2004 Society of Chemical Industry