The rheological properties of ketchup as a function of different hydrocolloids and temperature

The flow properties of ketchup were assessed upon addition of commonly used food thickeners: guar, xanthan and CMC gum at three different concentrations (0.5%, 0.75% and 1%) and four temperatures (25, 35, 45 and 55 °C). The ketchup without supplementation served as a control. All ketchup formulations exhibited non-Newtonian, pseudoplastic behaviour at all temperatures and hydrocolloid levels. The Power-law and Herschel-Buckley model were successfully applied to fit the shear stress versus shear rate data. The flow behaviour indices, n and n' , varied in the range of 0.189–0.228 and 0.216–0.263, respectively. The consistency coefficients, k and k' , were in the range of 8.42–27.22 and 6.56–20.10 Pa s ⁿ , respectively. The addition of hydrocolloids increased the yield point (τ₀) and apparent viscosity of the ketchup in comparison to that of the control. The Arrhenius equation was successfully used to describe the effects of temperature on the apparent viscosity of the prepared formulations. The E _a value appeared in the range between 5492.6 and 21475.8 J mol⁻¹.     

Effect of selected Hofmeister salts on textural and rheological properties of nonfat cheese

Three Hofmeister salts (HS; sodium sulfate, sodium thiocyanate, and sodium chloride) were evaluated for their effect on the textural and rheological properties of nonfat cheese. Nonfat cheese, made by direct acidification, were sliced into discs (diameter = 50 mm, thickness = 2 mm) and incubated with agitation (6 h at 22°C) in 50 mL of a synthetic Cheddar cheese aqueous phase buffer (pH 5.4). The 3 HS were added at 5 concentrations (0.1, 0.25, 0.5, 0.75, and 1.0 M) to the buffer. Post-incubation, cheese slices were air dried and equilibrated in air-tight bags for 18 h at 5°C before analysis. Small amplitude oscillatory rheology properties, including the dynamic moduli and loss tangent, were measured during heating from 5 to 85°C. Hardness was determined by texture profile analysis. Acid-base buffering was performed to observe changes in the indigenous insoluble (colloidal) calcium phosphate (CCP). Moisture content decreased with increasing HS concentration. Cheeses incubated in high concentrations of SCN⁻ softened earlier (i.e., loss tangent = 1) compared with other HS treatments. Higher melting temperature values were observed for cheeses incubated in high concentrations of SO₄²⁻. Hardness decreased in cheeses incubated in buffers with high concentrations of SCN⁻. The indigenous CCP profile of nonfat cheese was not greatly affected by incubation in Cl⁻ or SCN⁻, whereas buffers with high concentrations of SO₄²⁻ reduced the acid-base buffering contributed by CCP. The use of high concentrations (1.0 M) of SCN⁻ for incubation of cheeses resulted in a softer protein matrix at high temperatures due to the chaotropic effect of SCN⁻, which weakened hydrophobic interactions between CN. Cheese samples incubated in 1.0 M SO₄²⁻ buffers exhibited a stiffer protein matrix at high temperatures due to the kosmotropic effect of SO₄²⁻, which helped to strengthen hydrophobic interactions in the proteins during the heating step. This study showed that HS influenced the texture and rheology of nonfat cheese probably by altering the strength of hydrophobic interactions between CN.     

Effect of frozen storage on the proteolytic and rheological properties of soft caprine milk cheese

Freezing and long-term frozen storage had minimal impact on the rheology and proteolysis of soft cheese made from caprine milk. Plain soft cheeses were obtained from a grade A goat dairy in Georgia and received 4 storage treatments: fresh refrigerated control (C), aged at 4°C for 28 d; frozen control (FC), stored at −20°C for 2 d before being thawed and aged in the same way as C cheese; and 3-mo frozen (3MF), or 6-mo frozen (6MF), stored at −20°C for 3 or 6 mo before being thawed and aged. Soft cheeses had fragile textures that showed minimal change after freezing or over 28 d of aging at 4°C. The only exceptions were the FC cheeses, which, after frozen storage and aging for 1 d at 4°C, were significantly softer than the other cheeses, and less chewy than the other frozen cheeses. Moreover, after 28 d of aging at 4°C, the FC cheeses tended to have the lowest viscoelastic values. Slight variation was noted in protein distribution among the storage treatment, although no significant proteolysis occurred during refrigerated aging. The creation and removal of ice crystals in the cheese matrix and the limited proteolysis of the caseins showed only slight impact on cheese texture, suggesting that frozen storage of soft cheeses may be possible for year-round supply with minimal loss of textural quality.     

A model system for studying the effects of colloidal calcium phosphate concentration on the rheological properties of Cheddar cheese

A novel model system was developed for studying the effects of colloidal Ca phosphate (CCP) concentration on the rheological properties of Cheddar cheese, independent of proteolysis and any gross compositional variation. Cheddar cheese slices (disks; diameter = 50 mm, thickness = 2 mm) were incubated in synthetic Cheddar cheese aqueous phase solutions for 6 h at 22°C. Control (unincubated) Cheddar cheese had a total Ca and CCP concentration of 2.80 g/100 g of protein and 1.84 g of Ca/100 g of protein, respectively. Increasing the concentration of Ca in the synthetic Cheddar cheese aqueous phase solution incrementally in the range from 1.39 to 8.34 g/L significantly increased the total Ca and CCP concentration of the cheese samples from 2.21 to 4.59 g/100 g of protein and from 1.36 to 2.36 g of Ca/100 g of protein, respectively. Values of storage modulus (index of stiffness) at 70°C increased significantly with increasing concentrations of CCP, but the opposite trend was apparent at 20°C. The maximum in loss tangent (index of meltability/flowability) decreased significantly with increasing concentration of CCP, and there was no significant effect on the temperature at which the maximum in loss tangent occurred (68 to 70°C). Fourier transform mechanical spectroscopy showed the frequency dependence of all of the cheese samples increased with increasing temperature; however, solubilization of CCP increased the frequency dependence of the cheese matrix only in the high temperature region (i.e., >35°C). These results support earlier studies that hypothesized that the concentration of CCP strongly modulates the rheological properties of cheese.     

Microstructure and rheological properties of Iranian white cheese coagulated at various temperatures

The effect of milk coagulation temperature on the composition, microstructure monitored using scanning electron micrographs, opacity measured by a Hunter lab system, and rheological behavior measured by uniaxial compression and small amplitude oscillatory shear were studied. Three treatments of Iranian White cheese were made by applying coagulation temperatures of 34, 37, and 41.5°C during the cheese-making procedure. A higher coagulation temperature resulted in increased fat and protein contents, and decreased the moisture content and ratio of moisture to protein. The highest temperature (41.5°C) had a significant effect on the opacity of Iranian White cheese. Milk coagulation at this temperature decreased the whiteness index (Hunter L value) and increased the yellowness index (Hunter b value) of the aged product compared with cheeses coagulated at lower temperatures. Microstructure of the cheese coagulated at 41.5°C was more compact and undisturbed, reflecting the higher values of stress at fracture and storage modulus measured for this treatment.     

Effect of substituting whey cream for sweet cream on the textural and rheological properties of cream cheese

In the manufacture of cream cheese, sweet cream and milk are blended to prepare the cream cheese mix, although other ingredients such as condensed skim milk and skim milk powder may also be included. Whey cream (WC) is an underutilized fat source, which has smaller fat droplets and slightly different chemical composition than sweet cream. This study investigated the rheological and textural properties of cream cheeses manufactured by substituting sweet cream with various levels of WC. Three different cream cheese mixes were prepared: control mix (CC; 0% WC), cream cheese mixes containing 25% WC (25WC; i.e., 75% sweet cream), and cream cheese mixes with 75% WC (75WC; i.e., 25% sweet cream). The CC, 25WC, and 75WC mixes were then used to manufacture cream cheeses. We also studied the effect of WC on the initial step in cream cheese manufacture (i.e., the acid gelation process monitored using dynamic small amplitude rheology). Acid gels were also prepared with added denatured whey proteins or membrane proteins/phospholipids (PL) to evaluate how these components affected gel properties. The rheological, textural, and sensory properties of cream cheeses were also measured. The WC samples had significantly higher levels of PL and insoluble protein compared with sweet cream. An increase in the level of WC reduced the rate of acid gel development, similar to the effect of whey phospholipid concentrate added to mixes. In cream cheese, an increase in the level of added WC resulted in significantly lower storage modulus values at temperatures <20°C. Texture results, obtained from instrumental and sensory analyses, showed that high level of WC resulted in significantly lower firmness or hardness values and higher stickiness compared with cream cheeses made with 25WC or CC cream cheeses. The softer, less elastic gels or cheeses resulting from the use of high levels of WC are likely due to the presence of components such as PL and proteins from the native milk fat globule membrane. The use of low levels of WC in cream cheese did not alter the texture, whereas high levels of WC could be used if manufacturers want to produce more spreadable products.     

脂肪替代物对Mozzarella干酪流变学特性影响研究

目的研究脂肪替代物对部分脱脂Mozzarella干酪的流变学特性及微观结构的影响。方法通过测定不同脂肪替代物(菊粉、麦芽糖醇、WPC-80、大豆卵磷脂)制成的部分脱脂干酪的基本组分、流变学特性、粘弹性模量变化、微观结构,研究不同脂肪替代物对干酪的影响。结果菊粉、WPC-80、大豆卵磷脂均能提高部分脱脂干酪的水分含量,加入脂肪替代物的干酪的pH明显低于对照组部分脱脂干酪的pH。WPC-80 G菊粉G大豆卵磷脂G麦芽糖醇G对照G,说明加入脂肪替代物能显著改善部分脱脂干酪的黏弹流变学特性。结论麦芽糖醇作为脂肪替代物替代脂肪的效果较好,能提高蛋白分子间疏水作用,加入麦芽糖醇的部分脱脂干酪的黏弹性与对照组最为接近。     

Effect of different starches on rheological and microstructural properties of (I) model processed cheese

A range of processed cheese spread samples containing starch were prepared on a Rapid Visco Analyser (RVA). The starches used were waxy cornstarch, high‐amylose cornstarch, rice starch, potato starch, wheat starch and acid‐converted starch. Incorporation of the starches at different levels produced marked differences in the rheological, microstructural and functional properties of the processed cheese spreads. Rheological attributes such as complex modulus and viscosity increased; the extent of increase depended on the starch type and the starch level. Starch incorporation at reduced protein levels demonstrated the possibility of maintaining satisfactory rheological properties at lower ingredient cost.     

Effect of different curd-washing methods on the insoluble Ca content and rheological properties of Colby cheese during ripening

A curd-washing step is used in the manufacture of Colby cheese to decrease the residual lactose content and, thereby, decrease the potential formation of excessive levels of lactic acid. The objective of this study was to investigate the effect of different washing methods on the Ca equilibrium and rheological properties of Colby cheese. Four different methods of curd-washing were performed. One method was batch washing (BW), where cold water (10°C) was added to the vat, with and without stirring, where curds were in contact with cold water for 5 min. The other method used was continuous washing (CW), with or without stirring, where curds were rinsed with continuously running cold water for approximately 7 min and water was allowed to drain immediately. Both methods used a similar volume of water. The manufacturing pH values were similar in all 4 treatments. The insoluble (INSOL) Ca content of cheese was measured by juice and acid-base titration methods and the rheological properties were measured by small amplitude oscillatory rheology. The levels of lactose in cheese at 1 d were significantly higher in CW cheese (0.06-0.11%) than in BW cheeses (∼0.02%). The levels of lactic acid at 2 and 12 wk were significantly higher in CW cheese than in BW cheeses. No differences in the total Ca content of cheeses were found. Cheese pH increased during ripening from approximately 5.1 to approximately 5.4. A decrease in INSOL Ca content of all cheeses during ripening occurred, although a steady increase in pH took place. The initial INSOL Ca content as a percent of total Ca in cheese ranged from 75 to 78% in all cheeses. The INSOL Ca content of cheese was significantly affected by washing method. Stirring during manufacturing did not have a significant effect on the INSOL Ca content of cheese during ripening. Batch-washed cheeses had significantly higher INSOL Ca contents than did CW cheeses during the first 4 wk of ripening. The maximum loss tangent values (meltability index) of CW cheese at 1 d and 1 wk were significantly higher compared with those of BW cheeses. In conclusion, different curd washing methods have a significant effect on the levels of lactose, lactic acid, meltability, and INSOL Ca content of Colby cheese during ripening.     

Effect of trisodium citrate concentration and cooking time on the physicochemical properties of pasteurized process cheese

The effects of the concentration of trisodium citrate (TSC) emulsifying salt (0.25 to 2.75%) and holding time (0 to 20 min) on the textural, rheological, and microstructural properties of pasteurized process Cheddar cheese were studied using a central composite rotatable design. The loss tangent parameter (from small amplitude oscillatory rheology), extent of flow (derived from the University of Wisconsin Meltprofiler), and melt area (from the Schreiber test) all indicated that the meltability of process cheese decreased with increased concentration of TSC and that holding time led to a slight reduction in meltability. Hardness increased as the concentration of TSC increased. Fluorescence micrographs indicated that the size of fat droplets decreased with an increase in the concentration of TSC and with longer holding times. Acid-base titration curves indicated that the buffering peak at pH 4.8, which is due to residual colloidal calcium phosphate, decreased as the concentration of TSC increased. The soluble phosphate content increased as concentration of TSC increased. However, the insoluble Ca decreased with increasing concentration of TSC. The results of this study suggest that TSC chelated Ca from colloidal calcium phosphate and dispersed casein; the citrate-Ca complex remained trapped within the process cheese matrix. Increasing the concentration of TSC helped to improve fat emulsification and casein dispersion during cooking, both of which probably helped to reinforce the structure of process cheese.     

Use of time–temperature superposition to study the rheological properties of cheese during heating and cooling

The objective of this study was to investigate the time–temperature superposition behaviour of the rheological properties of cheese during heating and cooling. A standard part‐skim Mozzarella cheese and a fat‐free cheese were used for the study. Fourier transform mechanical spectroscopy was used to simultaneously study the rheological properties over a range of frequencies from 0.08 to 8 Hz while samples were being heated from 10 to 90 °C or cooled from 90 to 10 °C at the rate of 1 °C min^?1. Master curves of storage modulus (G′), loss modulus (G′′) and loss tangent were obtained using a reference temperature of 70 °C.     

Dynamic oscillatory shear properties of O/W model system meat emulsions: Linear viscoelastic analysis for effect of temperature and oil concentration on protein network formation

Effects of oil concentration (57.50%, 58.75%, 60.00% and 61.25%) and temperature (5, 10 and 15 °C) on O/W model system meat emulsions were analyzed using oscillatory dynamic shear tests, allowing all emulsion systems to be characterized as linear viscoelastic solids exhibiting a pseudoplastic flow. The emulsion systems were characterized as weak gel-like macromolecular dispersions with G′ much greater than G″, exhibiting a plateau region. A modified Cox-Merz rule was applicable using shift factors. Frequency dependence of complex modulus (G^∗) was studied to measure strength of cross-linking protein network of the emulsion systems by calculating a practically constant order of the relaxation function (α = 0.10) and a concentration dependent stiffness parameter (A_α) using Friedrich and Heymann theory. It was concluded that the viscoelastic characteristics and strength of the emulsion systems increased with increasing oil level, but decreased with temperature. Different mathematical models were successfully constructed to predict the rheological parameters.     

Effect of sodium hexametaphosphate concentration and cooking time on the physicochemical properties of pasteurized process cheese

Sodium hexametaphosphate (SHMP) is commonly used as an emulsifying salt (ES) in process cheese, although rarely as the sole ES. It appears that no published studies exist on the effect of SHMP concentration on the properties of process cheese when pH is kept constant; pH is well known to affect process cheese functionality. The detailed interactions between the added phosphate, casein (CN), and indigenous Ca phosphate are poorly understood. We studied the effect of the concentration of SHMP (0.25-2.75%) and holding time (0-20 min) on the textural and rheological properties of pasteurized process Cheddar cheese using a central composite rotatable design. All cheeses were adjusted to pH 5.6. The meltability of process cheese (as indicated by the decrease in loss tangent parameter from small amplitude oscillatory rheology, degree of flow, and melt area from the Schreiber test) decreased with an increase in the concentration of SHMP. Holding time also led to a slight reduction in meltability. Hardness of process cheese increased as the concentration of SHMP increased. Acid-base titration curves indicated that the buffering peak at pH 4.8, which is attributable to residual colloidal Ca phosphate, was shifted to lower pH values with increasing concentration of SHMP. The insoluble Ca and total and insoluble P contents increased as concentration of SHMP increased. The proportion of insoluble P as a percentage of total (indigenous and added) P decreased with an increase in ES concentration because of some of the (added) SHMP formed soluble salts. The results of this study suggest that SHMP chelated the residual colloidal Ca phosphate content and dispersed CN; the newly formed Ca-phosphate complex remained trapped within the process cheese matrix, probably by cross-linking CN. Increasing the concentration of SHMP helped to improve fat emulsification and CN dispersion during cooking, both of which probably helped to reinforce the structure of process cheese.     

The effect of concentration and composition of ternary emulsifying salts on the textural properties of processed cheese spreads

We used regression analysis to model the influence of varying ratios of disodium hydrogenphosphate (DSP), tetrasodium diphosphate (TSPP) and sodium polyphosphate (POLY) upon the hardness, cohesiveness, and relative adhesiveness of processed cheese spread (dry matter – 40 g/100 g; fat in dry matter – 50 g/100 g) at total emulsifying salt levels of 2.0, 2.5 and 3.0 g/100 g. Specific ratios of DSP to TSPP that rapidly increased hardness and decreased cohesiveness (1:1–3:4) and relative adhesiveness (1:1–1:2) were identified. The effect of the specific ratio of DSP:TSPP on textural parameters of samples was weakening with the rising amount of POLY in the ternary mixture. With the amount of POLY above 60%, the effect of the specific ratio of DSP:TSPP on textural parameters of samples was insignificant. With an increasing concentration of emulsifying salts, the values of hardness and cohesiveness were rising while the values of relative adhesiveness of the processed cheeses were falling. However, neither the concentration of emulsifying salts nor the adjustment of pH of the samples reaching the optimal range (5.69–5.84) affected the general trend of dependence of the observed textural parameters of model processed cheeses on the changing proportion of DSP, TSPP and POLY (P ≥ 0.05).     

The effect of selected hydrocolloids on the rheological properties of processed cheese analogues made with vegetable fats during the cooling phase

The aim of this work was to observe the influence of different hydrocolloids on changes in the rheological properties of processed cheese and their analogues within the process of cooling depending on the type of the fat used (butter, coconut fat and palm oil). κ‐carrageenan, ι‐carrageenan, λ‐carrageenan, arabic gum and locust bean gum were used at a concentration of 1.0% w/w. With the decreasing temperature during the cooling period, an increase in the complex modulus (G*) was observed in all samples tested. Within the cooling period, the sample with the addition of κ‐carrageenan showed both the most significant increase in G* in comparison with the control and the highest values of hardness after a 7‐day storage period regardless of the type of the fat used. The samples with coconut fat were assessed as the hardest. On the other hand, the samples with palm oil showed the lowest hardness (with the same hydrocolloid used). In the gelling hydrocolloids (κ‐ and ι‐carrageenan), only small changes in temperature of coil‐to‐helix transition were observed (in range of 2–7 °C) as a result of the addition of different types of fat.     

Steady and dynamic shear rheological properties of sweet potato flour dispersions

Korean sweet potato flour dispersions at different concentrations (6, 7, 8, 9, and 10%) were evaluated for their steady and dynamic shear rheological properties. The steady shear rheological properties showed that sweet potato flour dispersions at 25 °C showed a shear-thinning fluid (n=0.31–0.41) exhibiting a yield stress. The magnitudes of Casson yield stress (σ_oc), consistency index (K) and apparent viscosity (η_a,100) increased with an increase in concentration. Within the temperature range of 25–70 °C, the apparent viscosity obeyed the Arrhenius temperature relationship with high determination coefficient (R ²=0.97–0.99) with activation energies (Ea) ranging 0.015–0.024 KJ/mol. Both power law and exponential type models were used to establish the relationship between concentration and apparent viscosity (η_a). Magnitudes of G′ and G″ increased with an increase in concentration. G′ values were higher than G″ over the most of the frequency range (0.63–63 rad/s), being frequency dependent. The sweet potato flour dispersions did not closely follow the Cox–Merz rule at concentrations lower than 10%.     

The effect of composition of ternary mixtures containing phosphate and citrate emulsifying salts on selected textural properties of spreadable processed cheese

Ternary mixtures consisting of phosphate and citrate emulsifying salts were studied for their impact on selected textural properties (especially hardness) of processed cheese spreads over a 30 day storage period at 6 ± 2 °C. Two different groups of samples were manufactured, one with pH adjustment (target values within the interval of 5.60–5.80) and one without pH adjustment. When binary mixtures with trisodium citrate (TSC) and tetrasodium diphosphate (TSPP) were used (with zero content of the other salts tested in the ternary mixture), the products consisting of TSC and TSPP at a ratio of approximately 1:1 were the hardest. Increasing the content of TSC, TSPP and/or sodium salt of polyphosphate and decreasing that of disodium hydrogen phosphate (DSP) in ternary mixtures resulted in the increasing of the hardness of processed cheese. The absolute values of processed cheese hardness significantly changed as a result of pH adjustment.     

Effect of the type of fat on rheology,functional properties and sensory acceptance of spreadable cheese analogue

The objective of this work was to evaluate the effect of different types of fat (butter oil, partially hydrogenated soybean fat and soybean oil) on the functionality, rheology and sensory acceptance of spreadable cheese analogues. Analogues made with partially hydrogenated soybean fat or soybean oil in substitution to butter oil presented lower fat globule size. As a consequence, these analogues showed lower melting, lower spreadability, higher hardness and higher values for the elastic and viscous moduli than cheese made with butter oil. Despite not managing to imitate the flavour of the traditional cheese, the analogue made with partially hydrogenated soybean fat showed good sensory acceptance.     

干酪流变学性质及其对质地的影响

综述了关于流变学性质方面的构成因素、影响因素、作用机理、对质地的影响以及酪蛋白凝胶结构的形成机理和它对流变学特性的影响。同时讨论了分子问相互作用对流变学性质的作用机理和加工条件对它的影响情况。通过对流变学和质地性质的研究，将有助于干酪生产者更好的地预测和控制产品的质量。     

The effect of pectin concentration on viscoelastic and sensory properties of processed cheese

The effect of pectin addition on viscoelastic properties of model processed cheeses with 40% w/w dry matter and 50% w/w fat in dry matter after 42 days of storage at temperature 6 ± 2 °C has been investigated using dynamic oscillation rheometry (plate–plate geometry; frequency range 0.1–50.0 Hz; temperature 20 °C). The role of pectin concentration (0.2%, 0.4%, 0.6% and 0.8% w/w) has been studied. Also, the sensory evaluation of samples has been made to assess cheese appearance, rigidity, spreadability and flavour. All samples with the pectin addition were more rigid and less spreadable compared with processed cheeses without pectin. With the increasing concentration of pectin the storage ( G ') and loss ( G ") moduli rose at the whole tested frequency range (0.1–50.0 Hz). Growing pectin content resulted in the decrease in loss tangent (the nature of gel was changed to more elastic material). The dependence of processed cheese rigidity on pectin concentration (in range 0–0.8% w/w) was not linear. The appearance and flavour were not worse by pectin addition.