Ali R. Taherian

Evaluation of rheological properties of selected salt enriched food hydrocolloids

Abstract Rheological properties of hydrocolloids are important for the design and operation of continuous processes such as ohmic heating. Addition of salt to hydrocolloids may be desirable to enhance the efficiency of ohmic heating. A rotational viscometer was used to characterize the flow behavior of pectin, starch, xanthan and carrageenan solutions at four temperatures ( 20° C , 40° C , 60° C and 80 ° C ) and three concentrations. Salt was added at 1%. Samples were subjected to a programmed shear rate increasing from 0 to 300 s −1 in 3 min, held constant at 300 s −1 for 10 min and linearly decreasing to 0 during 3 min. The power law model was fitted to shear stress vs. shear rate data to obtain the consistency coefficient (m) and the flow behavior index (n) for starch and pectin whereas the Herschel–Bulkley model was used for carrageenan and xanthan. Both m and n were sensitive to changes in temperature and concentration.

Steady and Dynamic Shear Rheological Properties, and Stability of Non-Flocculated and Flocculated Beverage Cloud Emulsions

Rheological properties of single-phase, and emulsions containing modified starch and gum arabic as surface active hydrocolloids, as well as xanthan and tragacanth gums as stabilizers were evaluated under steady and dynamic shear testing conditions using a control stress rheometer. Emulsions were formed by 9% and 14% gum concentrations with oil concentration maintained at 9% thus giving a 1:1 and 1.5:1 surface active agent to oil ratio, respectively. The rates of droplet coalescence and creaming, for a total of 8 emulsions, as a function storage time before and after dilution in a simulated fruit beverage were then investigated. Steady shear (flow curve) were well described by the Carreau model at shear stress ranging from 0.01 to 100 Pa. All prepared water phases indicated a zero-shear viscosity plateau followed by shear thinning behavior with flow behavior index (n) ranging from 0.51 to 0.79 for 14% starch-0.3% xanthan and 14% gum arabic-0.8% tragacanth stabilized emulsions, respectively. The water phase flow property data were well fitted by the Einstein equation and its expansions. The dynamic rheological properties of water phase and emulsions were also evaluated for G′(ω) and G″(ω) from 1 to 50 rad/s. Similar curves were obtained with varying degrees of deviations (G′ from G″) for different emulsions. Starch-xanthan emulsion and associated water phase at 1.5/1 agent to oil ratio demonstrated viscoelastic behavior (G′ ≥ G″) with lower droplet coalescence and creaming rates. On the other hand, gum arabic-xanthan emulsion at 1:1 agent to oil ratio showed the highest rate of droplet coalescence and a greater degree of creaming. It was speculated that the lower stability of gum arabic-xanthan emulsion could be related to the denaturation of proteinaceous part in the gum and loss of emulsification capacity due to lower pH and pasteurization.

Structural and Rheological Properties of Succinoglycan Biogums Made from Low-Quality Date Syrup or Sucrose Using Agrobacterium radiobacter Inoculation

This study examines and compares the structural and rheological properties of succinoglycan exopolysaccharide made by fermentation of sucrose or date syrup at identical temperature, pH, and total soluble solid. Using thin-layer chromatography (TLC), Fourier transform infrared (FTIR) spectroscopy, and rotational viscometery structural and rheological properties of prepared exopolysaccharides were assessed. The variables under studies were biogum concentrations (0.5%, 1.0%, 1.5%, and 2.0% w/w), temperature (5, 25 and 40°C), and pH (2.5, 4.0, 7.0, and 10.0). Results revealed that the quantity of exopolysaccharide produced in the date syrup (DSE) medium was three to five times greater than that of sucrose (SE) medium. The biogums exhibited non-Newtonian, shear-thinning behavior, and the viscosity of DSE was higher than SE at all tested concentrations. The TLC and FTIR spectroscopy assessments designated that the biogum is composed of glucose and galactose units, carrying a carboxylic group and indicated the presence of succinoglycan. The outcomes of this study could be useful to food industries seeking low cost biogum.

Kinetic Considerations of Texture Softening in Heat Treated Root Vegetables

Cylindrical pieces of turnip (Brassica napobbrassica) and beet root (B. vulgaris L) were heated at temperatures ranging from 70–100°C for different time intervals. Texture values of heat-treated products were evaluated by a computer-interfaced compression testing machine using a single-cycle deformation test. The force-to-deformation ratio was taken as a measure of sample firmness; the stress-to-strain ratio (modulus of deformability) as a measure of the sample stiffness; and the percentage of recoverability of input energy (percentage ratio of the area under the force-to-deformation curve during relaxation in relation to the total area) as a measure of sample springiness. The thermal softening behavior represented by all three measured parameters were found to follow the same trend of the pseudo first-order kinetic theory based on two substrates, one softening faster than the other. The softening rate for the rapid (first) mechanism was up to 100 times faster than for the slower (second) mechanism. The softening rate for turnip was up to 15 times faster than for the beet. While turnip pieces indicated a higher associated activation energy (141–167 kJ/mol) for the rapid mechanism compared to the slower mechanism (60–83 kJ/mol), the beet root showed a closer range of activation energy (82–92 kJ/mol) for the two mechanisms. The results obtained are useful in thermal processing applications to improve the quality of root vegetables.

Effect of intramammary infusion of chitosan hydrogels at drying-off on bovine mammary gland involution

The transition from lactation to the dry period in dairy cows is a period of high risk for acquiring new intramammary infections. This risk is reduced when the involution of the mammary gland is completed. Accordingly, approaches that speed up the involution process after drying-off could reduce the incidence of mastitis. The current study aimed to develop a biological response modifier that could be injected into cow teats to promote immune cell migration and speed up involution. Chitosan, a natural polysaccharide derived from chitin, is able to trigger host innate immunity. We developed 2 formulations made from either high- or low-viscosity chitosan. Both are liquid at room temperature but form a hydrogel at body temperature. In the first experiment, each udder quarter of 7 Holstein cows in late lactation was randomly assigned at drying-off to receive one of the following intramammary infusions: 2.5 or 5 mL of 5% (wt/vol) low-viscosity chitosan hydrogel, 5 mL of 5% high-viscosity chitosan hydrogel, or 5 mL of water. Milk (mammary secretion) samples were collected from each quarter on d -4, -1 (drying-off), 1, 3, 5, 7, and 10. Milk somatic cell counts and the concentrations of involution markers such as BSA, lactate dehydrogenase, and lactoferrin were measured in each sample. In comparison with the control, the chitosan hydrogel infusions significantly hastened the increases in somatic cell counts, BSA and lactoferrin concentrations, and lactate dehydrogenase activity in mammary secretions. No major differences between sources or volumes of chitosan were observed for the measured parameters. The compatibility of this approach with an internal teat sealant was verified in the second experiment. Each udder quarter of 8 Holstein cows was randomly assigned at drying-off to receive one of the following intramammary infusions: 5 mL of 2% low-viscosity chitosan hydrogel, 4 g of an internal teat sealant, a combination of sealant and chitosan, or 5 mL of water. Milk (mammary secretion) samples were collected from each quarter on d -4, -1 (drying-off), 5, and 10 to measure involution markers. These results suggest that chitosan hydrogel infusion hastened mammary gland involution and activate immune response, which may reduce the risk of acquiring new intramammary infections during the drying-off period. Those results were not affected by the presence of the teat sealant, showing that both approaches are fully compatible and could be used in combination.

KINETIC MODELING OF TEXTURE PROPERTIES OF BOLOGNA SAUSAGE UNDER COOKING CONDITIONS

Texture properties are important indices for the evaluation of Bologna sausage quality. The objective of the study was to investigate the effect of cooking temperature and time on texture properties, to determine correlations between various texture properties (i.e., hardness, springiness, adhesiveness, cohesiveness, gumminess, chewiness, and resilience), and to develop kinetic models of selected texture properties as a function of cooking temperature and time. Cooking conditions were established at five levels of cooking temperature from 50–70°C, and at five levels of cooking time from 10 to 30 min. Results showed that cooking conditions (temperature and time) and their interactions significantly affected the texture properties except for the adhesiveness (p < 0.01). A significant correlation (p < 0.01) was found between gumminess and chewiness. The relationship between cooking temperature and time and texture properties can be well described by a second order polynomial equation. Statistical results showed that these kinetic models can be used (R2 > 0.92) for the prediction of Bologna sausage texture properties within the range of experimental cooking conditions.

Viscoelastic Properties of Wiener Sausages During Cooking

Viscoelastic properties of Wieners during cooking were measured by a rheometer using a stress creep procedure (stress of 5 Pas and time of 60 s) for the retardation and the recovery stage. Experiments were performed at 6 temperatures (40–65°C) and 4 times (5–14 minutes). The viscoelastic behavior of Wieners was well described (R2 > 0.98) by a Burgers model. Main parameters, the instantaneous compliance Jo; the retardation compliance J1, the retardation viscosity μ1 and the Newtonian viscosity μo, varied significantly with cooking temperature and time. Four second order regression models were developed for these parameters. Predicted and experimental values were in good agreement (R2 > 0.84).

Dilution and aging of a sugar solution after its multiple uses in an osmotic dehydration process of lowbush blueberries

Osmotic dehydration occurs upon the immersion of biological pieces in hypertonic aqueous solutions. Two major counter-current flows are generated. Water comes out from the biological structure and solutes migrate from the solution. There has been an increasing R&D interest but only few examples of successful industrial implementation. Few options are available to overcome the problem of the solution dilution. Sugar can be added continuously but the result is an undesirable solution build-up. Another alternative is to concentrate the dilute solution by membrane processing or evaporation. However, these operations can be very costly. Little has been reported on the quality and aging of solutions after multiple uses. The objective of the study was to osmotically dehydrate batches of lowbush blueberries. Baskets of blueberries were immersed in a batch reservoir that was either opened or closed. The process was performed at 60oC for 3 hours. The sucrose solution was recirculated (30 L/min) with a ratio of 10:1 (solution:blueberries). Various chemical changes (e.g. pH, sucrose, glucose, fructose, anthocyanins) were measured. The pH of the solution decreased to reach an equilibrium value of 3.6. It was found that there was a significant inversion of sucrose into glucose and fructose in the solution. If the osmotic process was performed using an open reservoir, the natural evaporation was sufficient to compensate for the dilution of the solution. Using the same solution, anthocyanin content and pH values were found to reach equilibrium after 4 uses, limiting further losses of fruits components.

Kinetic Modelling of Texture Properties of Bologna Sausage During Cooking

Texture properties are important indices for the evaluation of Bologna sausage quality. The development of kinetic models describing the evolution of the texture property during the cooking process is a key step to further build a proper quality control system as well as to search for the optimized processing conditions while establishing cooking-cooling cycles. The objective of the study was to investigate the effect of cooking temperature and time on texture properties, to determine correlation coefficients between various texture properties (i.e. hardness, springiness, adhesiveness, cohesiveness, gumminess, chewiness and resilience), and to develop kinetic models of selected texture properties as a function of cooking temperature and time. Texture properties were measured using a TA-XT2 Texture Analyzer. For all test samples, a double compression procedure (Texture Profile Analysis or TPA) was used at a speed of 0.8 mm/s. Cooking conditions were established at 5 levels of cooking temperature from 50 to 70oC and 5 levels of cooking time from 10 to 30 min. Statistical analyses were performed to include an analysis of variance (ANOVA), a correlation matrix analysis, and a multiple regression analysis. Results showed that cooking conditions (temperature and time) and their interaction significantly affected the texture properties except for the adhesiveness (p 0.01). A significant correlation (p 0.01) was found between gumminess and chewiness. The relationship between cooking temperature and time and texture properties can be well described by a second order polynomial equation. Using a multiple variable nonlinear regression analysis, kinetic models were developed as a function of temperature and time for hardness, springiness, cohesiveness, and chewiness. Statistical results showed that these kinetic models can be safely used for the prediction of Bologna sausage texture properties within the range of experimental cooking conditions.