Correlating mozzarella cheese properties to its production processes and microstructure quantification

Production processes influence both the composition and microstructure of cheese. Frequently the relationship between property, processing and structure has been studied empirically and the complex interactions between all parameters have not been quantified. This is often due to the limited number of production processes used to produce samples which may potentially produce biased correlations. In this study mozzarella cheeses were manufactured with a range of compositions and production processes to give three groups of cheeses with different fat contents, draining pH or calcium contents, and stretching conditions, i.e. stretching temperature and speed. Principal Component Analysis was applied to the analysis of correlations within each group of cheese samples. In this study, we found that a positive correlation exists between the diameter of fat globules and meltability, as well as free oil. In addition, we also found a positive correlation between the protein content and stretching parameters.     

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.     

Impact of the type of cooker-stretcher on chemical,rheological and microstructural properties of low-moisture mozzarella cheese analogue

In this work, we carried out the curd plasticisation of part-skim low-moisture Mozzarella cheese analogue (LMMCA) through a continuous dipping-arms cooker-stretcher or a batch twin-screw extruder. The chemical composition of LMMCA samples obtained with the two machines was not statistically significant. During refrigerated storage (8°C), samples processed with the cooker-stretcher showed higher hardness values and were slightly less proteolysed. Hydrolysis of para-casein proceeded at the same rate in LMMCA samples made with the two systems. We observed similar microstructures by confocal laser scanning microscopy. Under adopted processing conditions, both treatments allowed to obtain LMMCA samples with stable hardness values up to 50 days.     

Utilization of two plant polysaccharides to improve fresh goat milk cheese: Texture,rheological properties,and microstructure characterization

This study aimed to evaluate the effects of added jujube polysaccharide (JP) and Lycium barbarum polysaccharide (LBP) on the texture, rheological properties, and microstructure of goat milk cheese. Seven groups of fresh goat milk cheese were produced with 4 levels (0, 0.2, 0.6, and 1%, wt/wt) of JP and LBP. The goat milk cheese containing 1% JP showed the highest water-holding capacity, hardness, and the strongest rheological properties by creating a denser and more stable casein network structure. In addition, the yield of goat milk cheese was substantially improved as a result of JP incorporation. Cheeses containing LBP expressed lower fat content, higher moisture, and softer texture compared with the control cheese. Fourier-transform infrared spectroscopy and low-field nuclear magnetic resonance analysis demonstrated that the addition of JP improved the stability of the secondary protein structure in cheese and significantly enhanced the binding capacity of the casein matrix to water molecules due to strengthened intermolecular interactions. The current research demonstrated the potential feasibility of modifying the texture of goat milk cheese by JP or LBP, available for developing tunable goat milk cheese to satisfy consumer preferences and production needs.     

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     

Composition,structure, rheological properties,and sensory texture of processed cheese analogues

Processed cheese analogues were made with different fat and moisture in nonfat solids (MNFS) contents and used to study relationships between composition, microscopic structure, rheological properties and sensory texture. Fat contents ranged from 58 to 230 g kg^?1 and MNFS from 487.6 to 603.3 g kg^?1. Regressions showed that those rheological parameters measured by uniaxial compression at large deformations and moderately high rates were best explained by linear combinations of MNFS, protein and fat. The moisture in the protein network acted as a plasticiser lowering the rheological parameters. Fat alone had little direct effect on the rheological characteristics under these conditions but at small deformations and low deformation rates it formed elastic inclusions that contributed to the properties. Examination of fracture surfaces in the SEM suggested that, during fracture, fat was squeezed out and acted as a lubricant. Maximum stress and work to maximum stress measured at moderately high deformation rates related best to the sensory results and described fracture of the cheeses. From the regressions, for 95% confidence limits, sensory analysis could theoretically measure changes within the range of composition tested of <0.1% in MNFS or fat. Of the rheological parameters only work to maximum stress was as sensitive. However, interaction between these compositional factors reduced the sensitivity in practice.     

An approach to improve the baking properties and determine the onset of browning in fat-free mozzarella cheese

Compared with low-moisture part-skim mozzarella and mozzarella cheese, bake performance of low-fat and fat-free mozzarella on pizza has a lot to desire. We hypothesized that a water-soaking pretreatment step of low-fat and fat-free cheese shreds before baking would improve pizza baking performance. The study also examined the correlation of the onset of cheese browning with the rate of moisture loss, changes in cheese surface temperature, and 3-dimensional (3D) plot L* a* b* CIELAB color analysis. The pretreatment of soaking cheese shreds in water improved the baking properties of fat-free mozzarella cheese on pizza. Compared with the control sample, which demonstrated significant shred identity, poor shred melt, fusion, and stretch during a pizza bake with fat-free mozzarella, the soaked cheese (SC) sample demonstrated satisfactory cheese melt, fusion, and stretch. In addition, the SC sample had desired browning as opposed to the control sample's excessive browning. The additional moisture from the soaking pretreatment aided in delaying the onset of cheese browning in the SC sample when compared with the control sample. For both the control and SC samples, there was a strong correlation between the onset of cheese browning with the peak of moisture-loss rate, and an increase in cheese surface temperature (>100°C). The color analysis of the 3D plot confirmed the relationship between the onset of cheese browning and the shift in L* (lightness), a* (red-green color), and b* (blue-yellow) values. According to the study's findings, soaking cheese shreds before baking can help improve bake performance on pizza. Furthermore, 3 measurement tools used in the study, (1) moisture-loss rate, (2) cheese surface temperature, and (3) 3D plot CIELAB color, were useful in determining the onset of cheese browning and can be applied to different intervention strategies to control cheese browning during pizza baking.     

Spreadable ricotta cheese with hydrocolloids: Effect on physicochemical and rheological properties

Ricotta cheese was selected to develop a novel food product. Ricotta is easily obtained from the precipitation of whey and milk proteins, through the application of heat and acidification. This product is characterised by its compact, finely granulated and crumbly mass of limited shelf life. Unlike the conventional methods for ricotta elaboration, a novel processing step was introduced to improve spreadability. The effect of hydrocolloids addition on physicochemical, mechanical and rheological properties was evaluated during storage. Hydrocolloids had a positive effect on the cheese matrix regarding microstructure and rheological properties. Samples showed acceptable physicochemical properties (compared with the control) during storage. Addition of hydrocolloids attenuated syneresis. Preliminary results showed that the best formulation was ricotta cheese containing high gelification capacity gelatin. Results of this study may contribute to the development of a novel dairy product.     

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.     

Effect of mechanical and thermal treatments on the microstructure and rheological properties of carrot,broccoli and tomato dispersions

BACKGROUND: The food industry has shown an increased interest in the manufacture of healthier and more natural food products. By tailored processing fruit and vegetables can be used as structurants thus reducing artificial gums and stabilisers. The effect of different thermal and mechanical treatments, including high‐pressure homogenisation, on the microstructural and rheological properties of carrot, broccoli and tomato dispersions was studied. As part of the rheological characterisation small oscillatory deformation as well as shear flow measurements were performed. RESULTS: Carrot and broccoli showed a different behaviour from tomato under the conditions studied. Changing the order of thermal and mechanical treatment led to microstructures with different flow properties. The resulting microstructures differed in the manner of cell wall separation: either breaking across the cell walls or through the middle lamella. High‐pressure homogenisation decreased the viscosity of carrot and broccoli dispersions, while it increased the viscosity of tomato. Cryo‐scanning electron microscopy showed that the cell walls of carrot and broccoli remained as compact structures after homogenisation whereas tomato cell walls were considerably swollen. CONCLUSIONS: Based on the type of vegetable, the different processes applied led to microstructures with different rheological properties. This study shows that particle size distribution, morphology and phase volume are important parameters to explain the complex relationship between rheology and microstructure for these types of systems. Copyright © 2010 Society of Chemical Industry     

Physicochemical,rheological and sensory properties of Egyptian Kariesh cheese containing wheat bran

The physicochemical, rheological and sensory properties during the storage of Kariesh cheeses made with 0.1, 0.2, 0.3, 0.4 or 0.5 g wheat bran/100 g milk were evaluated at 0, 7 and 15 days. The cheeses with 0.5 g wheat bran/100 g milk had a significantly (P < 0.01) higher yield and moisture content, and lower pH and protein content than the control. No significant differences (P > 0.01) in salt and ash contents were observed among the cheeses studied. Texture profile analysis showed that the rheological characteristics decreased significantly in cheeses made with wheat bran. These results suggested that wheat bran (up to 0.4%) can be used to produce a fibre fortified Kariesh cheese.     

Invited review: Sensory and mechanical properties of cheese texture

Instrumental mechanical properties (instrumental tests that measure force and deformation over time) of cheese and cheese texture (sensory perception of cheese structure) are critical attributes. Accurate measurement of these properties requires both instrumental and sensory testing. Fundamental rheological and fracture tests provide accurate measurement of mechanical properties that can be described based on chemical and structural models. Sensory testing likewise covers a range of possible tests with selection of the specific test dependent of the specific goal desired. Establishing relationships between instrumental and sensory tests requires careful selection of tests and consideration and analysis of the results. A review of these tests and a critical analysis of establishing relationships between instrumental and sensory tests is presented.     

ADSA Foundation Scholar Award: Materials science approach to the study of mechanical and diffusion properties in cheese

Dairy products can be manufactured in a variety of structural forms (e.g., liquid, semi-solids, and solids). Although liquid milk is a colloidal dispersion of fat and protein in the serum portion, it can easily be converted into a soft gel (yogurt) upon acid coagulation. Similarly, cheese, a rennet-coagulated, casein-rich fraction of milk, falls in the category of semi-solid foods. Structurally, all of these materials are complex in nature because of interactions between protein, fat, and water components. The structural origin of these diversified food textures is derived from the way that various food constituents are arranged to form a unique body or mass. Food materials science helps in the assessment of structural arrangements of these molecules at various length scales. This article focuses on the use of various materials science approaches for understanding the fundamental relationship between process, structure, and property in solving critical issues that pertain to the dairy industry and academia.     

Composition,microstructure and chemical interactions during the production stages of Mozzarella cheese

Changes in chemical composition, microstructure and chemical interactions before and after the stretching stage of mozzarella cheese processing were investigated. The increased acidity and the decreased pH resulted in the solubilisation of total calcium. The protein matrix became more compact and the size of the fat globules decreased with the incorporation of small individual fat globules, aggregates and fat globules of irregular form into the matrix. The predominant bonds in the curd before the stretching stage were hydrophobic interactions, whereas the number of calcium bonds was minimal. After the stretching stage, the primary bonds responsible for maintaining the cheese structure were calcium bridges, electrostatic interactions and hydrogen bridges. These results clarify important aspects of the bonds involved in the production of this type of cheese.     

Effect of freezing on the rheological, chemical and colour properties of Serpa cheese

The effect of freezing on the properties of a raw ewes'-milk semi-soft cheese (Serpa cheese) was studied using small amplitude oscillatory (SAOS) and texture measurements, colour and chemical parameters. The freezing was introduced at three different stages of the ripening process (28, 35 and 42 days), and the cheeses were maintained frozen for 12 months. Cheeses were submitted to a slow or fast freezing method, and to different storage temperatures: -10 and -20°C (three replicates for each set conditions). Chemical data showed that only the proteolysis indicators exhibited differences between frozen and non-frozen samples; frozen samples showed higher values of NPN than the non-frozen samples, indicating that the freezing process did not prevent the secondary proteolysis of cheese. Frozen samples showed a significantly (P<0·05) stronger structure than the non-frozen, as indicated by hardness. However, the differences between the frozen and non-frozen samples were not significantly for storage modulus (G' 1Hz) and loss tangent (tan δ 1Hz) (P>0·05). Freezing affected mainly colour parameters: frozen samples were more luminous, and more yellow-green. The results allowed us to conclude that the damages caused by freezing to cheese properties could be minimized if this type of storage is introduced at the end of ripening (42 d) using a freezing temperature of -20°C.     

Homogenisation improves the microstructure,syneresis and rheological properties of buffalo yoghurt

Homogenisation is known to improve the textural properties of bovine yoghurt but the potential of this processing step has not been systematically explored for buffalo yoghurt. In this study, buffalo milk was homogenised at 80 bar or 160 bar and the effect on the properties of buffalo yoghurt examined. The microstructure of both buffalo yoghurt samples produced from homogenised milk was significantly altered, forming a more interconnected protein network with smaller embedded fat globules. These structural changes resulted in a significant decrease in syneresis and hysteresis area and led to a considerable increase in the storage modulus, gel firmness and flow behaviour index. A higher homogenisation pressure of 160 bar resulted in a lower gel firmness and storage modulus, possibly due to the presence of bigger fat–protein clusters within the homogenised milk. A homogenisation pressure of 80 bar could be optimal for improving the quality of buffalo yoghurt.     

Effect of milk preacidification on low fat mozzarella cheese: II. Chemical and functional properties during storage.

The effect of milk preacidification on cheese manufacturing, chemical properties, and functional properties of low fat Mozzarella cheese was determined. Four vats of cheese were made in 1 d using no preacidification (control), preacidification to pH 6.0 and pH 5.8 with acetic acid, and preacidification to pH 5.8 with citric acid. This process was replicated four times. Modifications in the typical Mozzarella manufacturing procedures were necessary to accommodate milk preacidification. The chemical composition of the cheeses was similar among the treatments, except the calcium content and calcium as a percentage of protein were lower in the preacidified treatments. During refrigerated storage, the chemical and functional properties of low fat Mozzarella were affected the most by milk preacidification to pH 5.8 with citric acid. The amount of expressible serum, unmelted cheese whiteness, initial unmelted hardness, and initial apparent viscosity were lower with preacidification. The reduction in initial unmelted cheese hardness and initial apparent viscosity in the pH 5.8 citric treatments represents an improvement in the quality of low fat Mozzarella cheese that allows the cheese to have better pizza bake characteristics with shorter time of refrigerated storage.     

Interactions of water-soluble myofibrillar protein with chitosan: Phase behavior,microstructure and rheological properties

This study investigated the electrostatic interaction between water-soluble myofibrillar protein (MP) and chitosan (CH) for further developing muscle protein-based functional foods. Effects of pH (3.0–7.5), protein/polysaccharide mixing ratio (20:1–1:1), ionic strength (0.05–0.6 M KCl) and deacetylation degree (DD) of CH (70–95%) on the interactions were studied by turbidity analysis, phase behavior, zeta-potential, particle size, microstructure and rheological properties. Lower mixing ratios (5:1 and 1:1) improved the colloid stability of MP in mildly acidic environments (pH < 6.5). KCl (0.05–0.6 M) destroyed the colloidal stability and promoted phase separation. A high DD of CH (95%) promoted complexation by increasing the available cationic groups. Rheology displayed that the maximum viscoelasticity for each factor was occurred at a MP/CH ratio of 1:1, pH 6.5 and 95% DD of CH due to the enhanced intermolecular interactions. Fourier transform infrared spectroscopy (FTIR) confirmed that the electrostatic interactions contributed to complex formation, while hydrogen bonds also participated in. This research provided great insight for understanding the interaction of water-soluble MP with CH to further exploit low-salt meat protein-based foods.     

Changes in the physicochemical,microstructural and rheological properties of traditional Kope cheese during ripening

The effect of ripening time on the microstructural, physicochemical and rheological characteristics of traditional Kope cheese ripened in clay pots was investigated. The moisture content, pH and total nitrogen (TN)/dry matter (DM) of the cheese decreased, and DM, fat in DM and water‐soluble nitrogen/TN increased during this period. Storage and loss moduli increased, while loss tangent decreased; as a result, the elasticity characteristics were greater than the viscous characteristics of the samples. Microstructure images showed that the size of pores and casein network density increased significantly during ripening and, after 90 days, the structure of many pores became very similar to each other.