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Abstract
Effects of two types of emulsifying salts on the functionality of Mozzarella cheese were studied. Trisodium citrate (TSC) and trisodium pyrophosphate (TSPP) were added to the stretching water at level of 1%, 3% and 5% during hot-stretching step, respectively. The main composition, textural properties, meltability and free oil content of the cheese prepared were measured, and the rheological behaviors of the cheese were also observed. The results showed that addition of TSC and TSPP significantly affected the meltability of the cheese. Also, hardness, cohesiveness and free oil content of the cheese increased (P<0.05). Meltability content was increased by 37.58% and 59.57% with TSC of 3% and TSPP of 3%, respectively. Addition of the emulsifying salts promoted solubilization of phosphate in the cheese, resulting in protein-protein interactions decreased and protein-water interactions increased. The results showed that addition of TSC and TSPP into stretching water could significantly improve the functionality of Mozzarella cheese.
String cheeses were prepared using a single-screw extruder, and principal component analysis (PCA) was used to investigate the influence of the stretching temperature on their physicochemical properties. The results showed that both cheese curd and string cheese stretched at 70℃ had a high expressible serum content; strong mobility in bound, occluded, and free waters; a high proportion of occluded and free water components; high L* and a* values; a low proportion of bound water component; and low hardness, gumminess, chewiness, and resilience. Compared with the cheeses prepared at other stretching temperatures, string cheese prepared at a stretching temperature of 90℃ had a lower expressible serum content; weaker mobility in bound, occluded, and free waters; lower proportions of occluded and free water components; lower L* and a* values; higher proportion of bound water component; and higher hardness, gumminess, chewiness, and resilience. The elasticity, b*, and c values of string cheese were not significantly influenced by the stretching temperature (p〉0.05). The comprehensive assessment model of the stretching temperature and physicochemical properties of string cheese was established based on the PCA. The principal component score indicated that good physicochemical properties of string cheese could be obtained at 80℃ with a screw speed of 45 r/min. ©, 2014, South China University of Technology. All right reserved.
String cheeses were provided by a small-scale single screw extruder, and the effect of stretching temperature on the rheological characteristics and microstructure of string cheese was observed in this research. Scanning electron microscopy of string cheese indicated that cheese microstructure changed from amorphous three-dimensional into a near-linear parallel fibrous structure after stretching, which exhibited a more dense protein network structure at higher temperature. This microstructural change was consistent with a reduction in the level of serum expressed by centrifugation and suggested that after the stretching treatment the water holding capacity of the casein matrix increased with the rise of temperature. Dynamic measurement of the viscoelastic changes on heating the cheese from 25 to 80°C showed that rheological properties of string cheese were unstable below 50°C. Dynamic measurement of the viscoelastic changes on the string cheese from 0.1~10 Hz frequency sweep displayed that it had stronger viscoelastic and shear thinning properties, and the performance was more obvious with increasing stretching temperature. TPA results revealed that cheese hardness was affected by the stretching temperature significantly.
The relationship between sensory and instrumental texture measurements of natural and processed cheeses was studied. A descriptive analysis panel evaluated seven mouth-evaluated and five hand-evaluated texture terms. Instrumental measurements included texture profile analysis (TPA), frequency sweeps, and creep. Multivariate analyses showed that many of the sensory and instrumental analyses were highly correlated. Principal component analysis showed similarities and differences in how the cheeses were differentiated by sensory and instrumental techniques. TPA and fundamental rheological tests worked equally well at predicting sensory attributes of the cheeses, but TPA was better at predicting sensory attributes when cheeses were divided into two groups, natural and processed. Instrumental measurements predicted sensory attributes of processed cheeses better than natural cheeses. While fundamental rheological tests reveal important information on network structure and molecular arrangement, these results indicate that empirical texture evaluations work equally well or better at predicting sensory texture properties.
The effect of different milling pH value on cheese meltability was studied. Combined with confocal laser scanning spectroscopy, DSC and rheometer techniques, meltability, freezable water content, pH 4.6-soluble protein and Urea-PAGE were analyzed during 1~7 weeks storages. Results showed that Mozzarella cheese with a low milling pH value had less freezable water and more binding water. When the storage prolonged (more than 21d), protein degradation increased, and better meltability was achieved.
The addition of mineral salts to cheesemilk affected the processing variables as well as the final composition and texture of the mozzarella cheese. These effects were dependent both on the type of salt and the level at which it was added. Addition of Ca (0.05-0.20 mole/kg milk solids non-fat, MSNF) reduced the time for curd formation, lowered the pH of curd at cutting and increased moisture in cheese. The addition of phosphate to cheesemilk at levels up to 0.15 mole-added phosphate/kg MSNF did not affect time for curd formation or pH of curd at cutting but addition of phosphate at a higher level (0.20 mole/kg MSNF) delayed the time for formation of the curd and increased the pH of curd cutting. The addition of citrate (0.05 mole/kg MSNF) had similar effects to the addition of high levels of phosphate (0.2 mole/ kg MSNF). There was no curd formed on addition of a high level of added citrate (0.2 mole/kg MSNF). With the use of Ca plus citrate or Ca plus phosphate, the time for curd formation was generally unchanged or slightly reduced. With use of Ca plus phosphate, the pH of cutting was lower than that for cheesemilk without any added salts whereas the effects of added Ca plus citrate were variable. The effects of added salts on the textural properties of the cheese were variable and dependent on the season of mozzarella cheesemaking.
Objectives of this research were to determine whether locational differences in composition within a cheese block affected melting characteristics. Immediately after brining, industrial low moisture and low moisture, part skim cheeses were divided in half vertically. Equally weighted samples representing surface and center from one-half of each block were analyzed immediately (d 2) for apparent viscosity, free oil, and composition (moisture, fat, NaCl, Ca, pH). Samples from the other half were vacuum packaged and stored at 4°C until analysis on d 16. From d 2 to d 16, free oil increased significantly, and apparent viscosity decreased significantly. Free oil increased the most in the center of low moisture cheeses, indicating that Mozzarella with high fat and low NaCl contents has greater tendency to oil off. Surface samples had significantly higher NaCl and apparent viscosity and lower moisture, Ca, and free oil than center samples. These locational differences in melting characteristics may be caused in part by exchange of Na with casein-bound Ca at the cheese surface, which enhances the emulsifying ability of soluble casein, resulting in a more emulsified fat phase at the cheese surface and less formation of free oil.
Shreds of full fat Mozzarella cheese usually melt, fuse, and form light brown blisters, but fat-free or lower fat Mozzarella cheese shreds have limited melt and fusion and become scorched during pizza baking in commercial food service pizza ovens. Why is the functionality so different? Our results indicate that dehydration of the shred surface and subsequent skin formation are the critical events during pizza baking that limit melting and induce scorching of fat-free and lower fat Mozzarella cheese during pizza baking. When skin formation is prevented by lightly coating fat-free (
The effect of milk preacidification with acetic or citric acid on the composition and yield of low fat Mozzarella cheese was determined. Two cheese manufacturing trials were conducted. In trial 1, three vats (230 kg of milk per vat) of cheese were made in 1 d using no preacidification (control) and preacidification to pH 6.0 and pH 5.8 with citric acid. In trial 2, four vats (230 kg of milk per vat) of cheese were made in 1 d using no preacidification (control), preacidification to pH 6.0 and 5.8 with acetic acid, and preacidification to pH 5.8 with citric acid. Cheese manufacture was repeated on three different days in trial 1 and four different days in trial 2 using a randomized-complete block design. Preacidification to pH 5.8 with citric acid decreased cheese calcium more than preacidification to pH 5.8 with acetic acid. Preacidification with citric acid in trial 1 decreased protein recovery in the cheese, and there was a trend for decreased protein recovery in the cheese for trial 2. Differences in fat recovery due to preacidification varied, sometimes being lower than the control other times being higher than the control. The reduction in calcium and protein recovery in the cheese caused by preacidification lowered composition adjusted cheese yield and yield efficiency. Yield efficiency was reduced by about 2.5 and 5.5%, respectively, with preacidification to pH 6.0 and 5.8 with citric acid. Yield efficiency was reduced by about 2.2 and 3.4%, respectively, with preacidification to pH 6.0 and pH 5.8 with acetic acid.
Influence of emulsifying salts (ES) on some physical properties of casein micelles was investigated. A reconstituted milk protein concentrate (MPC) solution (5% wt/wt) was used as the protein source and the effects of ES [0 to 2.0% (wt/wt)] were estimated by measuring turbidity, acid-base titration curves and amount of casein-bound Ca and inorganic P (P(i)). Various ES, trisodium citrate (TSC), or sodium phosphates (ortho-, pyro-, or hexameta-) were added to MPC solution, and all samples were adjusted to pH 5.8. Acid-base buffering curves were used to observe changes in the amount and type of insoluble Ca phosphates. An increase in the concentration of TSC added to MPC solution decreased turbidity, buffering at pH approximately 5 (contributed by colloidal Ca phosphate), and amount of casein-bound Ca and P(i). Addition of up to 0.7% disodium orthophosphate (DSP) did not significantly influence turbidity, buffering curves, or amount of casein-bound Ca and P(i). When higher concentrations (i.e., > or =1.0%) of DSP were added, there was a slow decrease in turbidity. With increasing concentration of added tetrasodium pyrophosphate (TSPP), turbidity and buffering at pH approximately 5 decreased, and amount of casein-bound Ca and P(i) increased. When small concentrations (i.e., 0.1%) of sodium hexameta-phosphate were added, effects were similar to those when TSPP were added but when higher concentrations (i.e., > or =0.5%) were added, the buffering peak shifted to a higher pH value, and amount of casein-bound Ca and P(i) decreased. These results suggested that each type of ES influenced casein micelles by different mechanisms.
Effects of 2 types of emulsifying salts (ES) on the functionality of nonfat pasta filata cheese were examined. Nonfat pasta filata cheese was made from skim milk by direct acidification. Trisodium citrate (TSC) and tetrasodium pyrophosphate (TSPP) were added to curds (at 1, 3, and 5%, wt/wt) at the dry-salting step, together with glucono-delta-lactone to maintain a constant pH. When TSC was added, there were no significant compositional differences, although insoluble Ca and P contents significantly decreased with the addition of TSC. When TSPP was added, fat content was not significantly different, but protein content decreased with increasing concentrations of TSPP. Both insoluble Ca and P contents increased with the addition of 1% TSPP. The addition of ES affected textural and functional properties. With increasing concentrations of TSC, meltability increased, whereas increasing the TSPP content decreased meltability. Cheese made with 1% TSC had better stretchability compared with control cheese. However, the addition of more than 3% TSC decreased stretchability. Addition of TSPP caused a considerable decrease in stretchabilty. Scanning electron microscopy revealed that the size and number of serum pockets decreased and protein appeared more hydrated with the addition of both ES. These results suggested that TSC and TSPP influenced the functionality of nonfat pasta filata cheese differently; that is, the effects of TSC were probably caused by a decrease in the number of colloidal calcium phosphate cross-links and an increase in electrostatic repulsion, whereas the effects of TSPP may have been related to the formation of new TSPP-induced casein-casein interactions.