The microstructure and textural properties of Australian cream cheese with differing composition

Confocal laser scanning microscopy was used to compare the microstructure of six Australian commercial cream cheese products. The optimal conditions for cryo scanning electron microscopy (cryo SEM) analysis of cream cheese microstructure were also examined. These complementary techniques revealed a typical cream cheese microstructure of homogenised fat globules embedded in a non-continuous protein network. The association between fat and protein within the microstructure was influenced by product composition (fat:protein ratio, moisture content) and ingredients. The addition of emulsifier led to a softer product with distinct microstructure. Cryo SEM also revealed a “honeycomb”-like structure, which was interpreted as a eutectic artefact formed by the addition of gum(s). Product hardness and gel strength generally correlated with high fat, low moisture content and a compact microstructure. Overall, this study shows how product composition affects the microstructure, texture and rheological properties of cream cheese.     

Microstructure,texture, colour and sensory evaluation of a spreadable processed cheese analogue made with vegetable fat

‘Requeijão cremoso’ is a spreadable processed cheese that shows ample acceptance on the Brazilian market. In this work, analogues of this cheese, made by substituting 25% and 50% of the dairy fat with vegetable fat, were studied with respect to physical–chemical composition, texture profile, microstructure and sensory acceptance. The substitution of part of the dairy cream by vegetable fat resulted in increased adhesiveness and hardness. The traditional cheese presented a uniform protein network in which numerous small fat particles were dispersed, whilst in the analogues, the fat globules were present in smaller numbers and with greater diameters, a behaviour intensified by increasing proportions of vegetable fat. In the sensory analysis, the traditional cheese and the analogue with 50% vegetable fat were better evaluated than the analogue with 25% vegetable fat.     

Effect of homogenisation of cheese milk and high‐shear mixing of the curd during cream cheese manufacture

The role of the homogenisation pressure of cheese milk (0, 25, 100 MPa) and high‐shear mixing of cheese curd at different speeds (750, 1500, and 3000 r.p.m.) and times (2 and 4 min) in improving the texture of medium‐fat cream cheese was investigated independently. Homogenisation resulted in small fat globules and firmer texture, while increasing speed and mixing times resulted in a decrease in curd particle size and an increase in the spreadability of the cheese. All curd samples from both the trials exhibited shear‐thinning behaviour. Unhomogenised milk and high‐shear mixing of the curd showed a low coefficient of friction (better lubrication property).     

Effect of cream homogenization on textural characteristics of low-fat Iranian White cheese

The effects of cream homogenization of cheese making milk on textural and sensory characteristics of Iranian White cheese were studied. Cream was homogenized in a two-stage homogenizer at 6.0/2.5 or 9.0/2.5 MPa. Cheese samples were analyzed for rheological parameters (uniaxial compression and small amplitude oscillatory shear), meltability, microstructure, and sensory characteristics. Cream homogenization increased fat content leading to increased meltability. This effect increased as the homogenization pressure increased. The values of storage modulus, stress at fracture and Young's modulus of elasticity for cheeses from homogenized treatments were lower than those of unhomogenized cheese. Cream homogenization at 6.0/2.5 MPa effectively improved the textural, functional and sensory characteristics and enhanced the yield of low-fat Iranian White cheese. This cheese had the lowest values of storage modulus and stress at fracture, probably due to the high number of small, evenly dispersed fat globules in microstructure and especially its lower protein content. Cheeses with homogenized cream had improved texture, flavor and appearance.     

MILK GEL STRUCTURE. X. TEXTURE AND MICROSTRUCTURE IN CHEDDAR CHEESE MADE FROM WHOLE MILK AND FROM HOMOGENIZED LOW-FAT MILK1

Reduced-fat cheese (17% fat, 44% moisture) was considerably firmer and more elastic than full-fat cheese (35% fat, 35% moisture), even though the moisture levels in the nonfat matter (MNFM) of the cheese were the same, at 54%. Electron microscopy and compositional analysis revealed about 30% more protein matrix in the reduced-fat cheese. Apparently more of this matrix must be cut or deformed in sensorial and texture assessments. A practical implication is that MNFM should be slightly higher in the reduced-fat cheese than in full-fat cheese to achieve more similar texture. Homogenization of milk tended to increase the moisture content and decrease firmness and elasticity, but not markedly. The smaller fat globules, per se, did not apparently affect texture as measured in these experiments. Curd granule junctions were prominent in nonhomogenized-milk cheese, because large fat globules were lost at the granule surfaces leaving protein-dense junctions; those in homogenized-milk cheese were less apparent because the protein-dense areas, which resulted from the loss of small fat globules, were narrower. Sensory and textural parameters for firmness and elasticity were inter-correlated. The Bite Test was more useful than Instron measurements of deformation (20%), apparently because the latter was markedly affected by a slight openness in the cheese.     

The effect of adding enzyme‐modified cheese on sensory and texture properties of low‐ and high‐fat cream cheeses

The influence of enzyme‐modified cheese (EMC) and fat content on sensory and texture properties of cream cheese was investigated. Enzyme‐modified cheese and fat content were set at three levels each, and organoleptic and texture properties for all experimental cheeses were then determined. Data were analysed using response surface methodology. Both design parameters had significant influence on sensory and texture properties. The EMC did not alter hardness significantly, whereas the higher fat formula had the higher hardness. The results indicated that the optimum level of EMC was less than 1% for high‐fat cream cheeses and at least 5% for low‐fat cream cheeses.     

Characterisation of ice cream containing flaxseed oil

Five batches of a 12% (w/w) fat ice cream formulation were prepared using different amounts of flaxseed oil (0%, 3%, 6%, 9% and 12% w/w) to replace milkfat. Meltdown rates, texture of ice cream, particle size of fat globules and microstructure of the ice cream were determined. Increasing the proportion of flaxseed oil in ice cream resulted in an increase in the meltdown rate and a decrease in the ice cream hardness. These were attributed to the low melting temperature of flaxseed oil and the varying extent of fat flocculation. In ice cream containing a high proportion of milkfat, the fat globules formed large particles largely due to flocculation rather than partial‐coalescence. The extent of fat flocculation decreased as the proportion of flaxseed oil was increased. Evidence of fat coalescence was observed in ice cream containing 12% flaxseed oil. The fat flocculates stabilised the air cells and strengthened the foam structure of the ice cream.     

油脂用量对搅打稀奶油的搅打性能和品质的影响

研究了油脂用量对搅打稀奶油的粒度分布、脂肪部分聚结、液相蛋白质浓度、搅打起泡率、质构特性、感官品质和稳定时间的影响。研究表明:随着油脂用量增加,冷却后乳浊液脂肪球粒径增大;搅打过程中脂肪部分聚结速度和脂肪球粒径d4,3均随油脂用量增加而增大,且脂肪部分聚结率与脂肪球粒径d4,3有很好的相关性;液相蛋白质浓度和搅打起泡率降低;搅打稀奶油的质构特性值增加;稳定时间呈先增后减趋势,当油脂用量为23%时,搅打稀奶油的稳定时间最长达到2.7h;搅打稀奶油的感官品质以油脂用量为20%最好,综合考虑,油脂最佳用量范围是20%-23%。     

Rheological properties and microstructure of Cheddar cheese made with different fat contents

Reduced- and low-fat cheeses are desired based on composition but often fall short on overall quality. One of the major problems with fat reduction in cheese is the development of a firm texture that does not break down during mastication, unlike that observed in full-fat cheeses. The objective of this investigation was to determine how the amount of fat affects the structure of Cheddar cheese from initial formation (2 wk) through 24 wk of aging. Cheeses were made with target fat contents of 3 to 33% (wt/wt) and moisture to protein ratios of 1.5:1. This allowed for comparisons based on relative amounts of fat and protein gel phases. Cheese microstructure was determined by confocal scanning laser microscopy combined with quantitative image analysis. Rheological analysis was used to determine changes in mechanical properties. Increasing fat content caused an increase in size of fat globules and a higher percentage of nonspherical globules. However, no changes in fat globules were observed with aging. Cheese rigidity (storage modulus) increased with fat content at 10°C, but differences attributable to fat were not apparent at 25°C. This was attributable to the storage modulus of fat approaching that of the protein gel; therefore, the amount of fat or gel phase did not have an effect on the cheese storage modulus. The rigidity of cheese decreased with storage and, because changes in the fat phase were not detected, it appeared to be attributable to changes in the gel network. It appeared that the diminished textural quality in low-fat Cheddar cheese is attributed to changes in the breakdown pattern during chewing, as altered by fat disrupting the cheese network.     

Microstructural changes in fat during the ripening of Iranian ultrafiltered Feta cheese

In this study, fat globules in Iranian ultrafiltered Feta cheese (3 to 60 d) were directly observed during the ripening period by scanning electron microscopy. According to images of ultrafiltered Feta cheese samples obtained by scanning electron microscopy, individual fat globules and aggregates of fat were easily distinguishable on d 3 and had completely disappeared within 20 d of storage. On d 20, only the fingerprints of the fat globules and pools of free fat in the casein matrix remained. After 40 d of ripening, the texture was homogeneous and no fat globules or fat voids were detected. Chemical analysis of cheese samples showed that with an increase in the ripening period, the contents of dry matter and fat decreased significantly, whereas the pH values and salt content did not indicate any significant changes.     

Characterization of particles in cream cheese

Cream cheese is used as a spread and as an ingredient in many food applications. A gritty or grainy mouthfeel is an undesirable textural defect that occurs in cream cheese. However, the factors that cause the textural defect are not well understood. The objectives of this study were to isolate and characterize particles from cream cheese and to study the effect of particles on cheese texture. Particles were isolated by washing cream cheese with water first at 25 degrees C and then at 50 degrees C repeatedly 4 to 5 times. The size of these particles was determined using a particle size analyzer. The particles as well as the original cheeses were analyzed for moisture, fat, protein, ash, and lactose. The particle size ranged of 0.04 to 850 microm. It was found that isolated particles were significantly higher in protein content as compared with the whole cheese. To study the effect on the cheese texture, particles were added at 5, 15, and 25% (wt/wt) levels to smooth cream cheese, and a sensory ranking test was done on the samples. Isolated particles were further separated into 2 size classes of 2.5 to 150 microm and > or =150 microm. These particles were then mixed with smooth cream cheese at 16 and 29% (wt/wt), and a sensory test was conducted on these samples. Smooth cream cheese with only 5% (wt/wt) added particles was perceived as significantly grittier than the control sample. This experiment also revealed that the perceived grittiness increased with increase in amount and size of particles.     

黄油-代可可脂基奶油生产工艺优化及其晶型形成分析

在分析油脂用量对黄油-代可可脂基奶油品质影响的基础上,通过正交试验研究油脂用量、黄油-代可可脂质量比和均质压力对奶油搅打性能、质构特性、脂肪球部分聚结率、结晶特性等的影响。结果表明,在油脂用量30%、黄油-代可可脂质量比2∶3、均质压力60?MPa的条件下,能保证脂肪部分聚结的发生,并保持搅打稀奶油较好的感官特性、起泡性和结晶特性。60?MPa的均质压力保证了体系的稳定性,使大量游离脂肪球产生从而促进脂肪部分聚结。晶型形成分析结果表明,在优化条件下,原料乳浊液X-射线衍射峰峰形由较宽、较尖锐变为峰形适中均匀,适宜搅打稀奶油的β’晶型晶体明显增多,搅打稀奶油乳浊液在低温条件下发生脂肪结晶,表现为脂肪晶体尺寸增大。     

Effects of buttermilk powders on emulsification properties and acid tolerance of cream

Emulsifying properties and acid tolerance are 2 of the most important characteristics of cream. The effects of the buttermilk component, especially its phospholipids, on the emulsifying properties and acid tolerance of cream were investigated in this study. Two buttermilks with differing phospholipid contents and skimmed milk were used to evaluate the effects of phospholipids on the aforementioned parameters. The mean diameter of fat globules and the cream viscosity were used as indicators of emulsifying properties. Acid tolerance was evaluated by studying the effect of citric acid on the maximum viscosity of cream. This was tested by adding 400 μL of 10% (w/w) citric acid solution to cream every minute and simultaneously measuring pH and viscosity. In 45% and 40% fat cream systems, buttermilk, and especially that with higher phospholipid content, improved the emulsifying properties and acid tolerance of the cream. The components of buttermilk could alter the properties of the surface of fat globules, thereby altering the emulsification properties of the cream. However, neither of the tested buttermilks affected the emulsifying properties and acid tolerance of lower-fat (35% and 30%) cream systems. Emulsifying components exist in proportionately larger amounts in lower-fat creams, which could render the emulsifying properties resistant to change. The number of fat globules may also influence acid-induced changes in viscosity. The addition of phospholipids or lysophospholipids did not improve the acid tolerance of creams, a finding that may be attributable to the formation of complexes of phospholipids and protein. PRACTICAL APPLICATION: The findings presented herein demonstrate the ability to improve the acid tolerance of cream using materials derived from milk. Implementing these findings appropriately may result in a high-quality cooking cream.     

Rheological and microstructural characterization of double cream cheese

Firmness at 5 °C, dynamic viscoelastic moduli (G' G) and capillary extrusion profiles at 20 °C, were obtained on double cream cheese after the different steps of processing (curd obtention, mixing at 70 °C and 500 r.p.m. with heat-denatured WPC, heating at 85 °C, homogenizing at 20 MPa (1st stage) and 5 MPa (2nd stage) and cooling to 20 °C and 13 °C) and storage 7–9 days at 5 °C. It was found that double cream cheese became firmer and more elastic after heating and homogenization, although it became softer and more viscous after mixing and cooling. Transmission Electron Microscopy (TEM) and cryo-Scanning Electron Microscopy (SEM) micrographs showed that rheology results could be related to aggregation (during heating and homogenization) and disruption (during cooling) of milk fat globule/casein complexes. Dispersion of homogenization clusters after cooling, and aggregation of milk fat globules during storage caused double cream cheese structural instability to appear. It was suggested that the heterogeneity of capillary extrusion profiles could be quantified through application of fractal concepts and Fourier analysis and related to structure and texture of double cream cheese.     

Polymorphism, microstructure and rheology of butter. Effects of cream heat treatment

The effect of cream heat treatment prior to butter manufacturing, fluctuating temperatures during storage and presence of fat globules vs. no fat globules was examined in laboratory scale produced butter. X-ray diffraction and differential scanning calorimetry was used to study crystallization behaviour and nuclear magnetic resonance to measure solid fat content and water droplet size distribution. Furthermore, the crystal structure was linked to the rheological properties and microstructure of the butter using confocal laser scanning microscopy. Butter produced from non-matured cream mainly formed α- and β'-crystals with minor traces of β-crystals. Maturing of the cream caused a transition from α- to β'- and β-form. The rheological behaviour of slow cooled butter deviated from the matured ones by having a lower elastic modulus, caused by a weaker crystal network. Presence of fat globules did not affect the rheological properties significantly.     

Science and technology of cultured cream products: A review

Cultured cream, produced by fermentation, has several culinary uses requiring different properties, and this may necessitate using different production technologies. Products with reduced fat content are increasingly popular, but compromised sensory properties are not desired. Here, the technology for the production of cultured cream and the influence of various parameters on its properties are reviewed; the effect of homogenisation on cream of varying fat content and the subsequent fermentation of this cream is given special focus. The structure of low fat (10–15%) cultured cream is dominated by a milk protein acid gel; high fat (≥30%) cultured cream is dominated by a gel structure consisting of coagulated protein-covered fat globules. Cultured cream with approximately 20% fat has neither a dense protein acid gel nor a high density of coagulated protein-covered fat globules. Quality challenges presented by the latter products may be mitigated by addition of milk protein.     

The fat globule membrane in ice cream

A method for determining the average thickness of the membrane around the fat globules in homogenised ice cream mix from the mix viscosity is examined. The difficulties with this approach, such as the non-Newtonian behaviour of the mix, the polydisperse nature of the fat globule size distribution and the contribution of the micellar casein to the volume fraction of the aqueous phase, are discussed. Values of 60 to 90 nm for the effective “hydrodynamic” thickness have been obtained for ice cream mixes of 9% w/w vegetable fat and 10.5% w/w skim milk solids. It is suggested from these values, and from the interpretation of electron micrographs of similar mixes, that part of the micellar casein is attached to fat globules, thus increasing the effective volume fraction of the fat and accounting for the abnormally high viscosities of these mixes.     

再制干酪乳化过程中理化、功能特性及微观结构的变化

以再制干酪为研究对象,探究再制干酪在不同乳化温度下（80℃和85℃）,从乳化开始到结束（5～30 min）,再制干酪功能特性（融化性、油脂析出性）、质构特性、流变学特性和微观结构的变化情况。结果表明,随着乳化时间延长,产品的融化性及油脂析出性呈下降趋势,乳化过程中85℃再制干酪的油脂析出性显著高于80℃再制干酪（P<0.05）。干酪的质构特性随着乳化时间的延长整体呈增大趋势,其中85℃干酪胶着性和咀嚼性显著增大（P<0.05）,85℃再制干酪的硬度、胶着性和咀嚼性均大于80℃。两种加工温度的干酪在相同乳化程度下干酪的储能模量（G’）均大于损耗模量（G”）,0.1～10 Hz内G’和G”都随频率的升高呈上升趋势。干酪的微观结构显示,乳化5～15 min时脂肪球数量大大减少且直径减小,分布更加均匀,蛋白质基质更加光滑,干酪结构更加致密;但乳化20～30 min时干酪的微观结构呈蜂窝状,即奶油化反应过度。因此,再制干酪加工过程中乳化时间短,奶油化反应不充分;再制干酪乳化时间过长会使质地发生不良变化。再制干酪乳化反应过程中,蛋白质-蛋白质和蛋白质-脂肪的相互作用增强,产品的功能特性...