Increasing the moisture content of imitation cheese: effects on texture, rheology and microstructure

Increasing moisture content may be a practical and cost-effective means to control the functional properties of imitation cheese. Imitation cheeses with moisture contents of 46, 50, 52 and 54 g/100 g were manufactured. An increase in the moisture content of the imitation cheese resulted in significantly increased meltability, tan values and decreased hardness (all P<0.05). The relationship between moisture content (x) and meltability (y) was described by the model (r²=0.99). A linear relationship emerged between moisture content (x) and hardness (y), where (r²=0.95) but cohesiveness was unaffected by moisture content. Increasing the moisture content to 52 or 54 g/100 g led to pockets of free water within the cheese and larger but fewer fat globules. The maximum level of moisture that the cheese matrix can retain appears to be 54 g/100 g.     

Modification of imitation cheese structure and rheology using pre-gelatinised starches

The rheological properties and microstructure of imitation cheeses containing 3%, w/w, pre-gelatinised maize, waxy-maize, wheat, potato or rice starches were compared to a control (0%, w/w, starch). Dispersions of pre-gelatinised rice or waxy-maize starches with casein had the highest viscosities following heating at 80 °C compared to casein heated alone or in mixtures with the other starches. Imitation cheese products containing pre-gelatinised starches had larger fat globule size distributions (especially rice or waxy-maize starch) and less homogeneous background protein matrices than the control as evidenced by scanning electron microscopy, which indicated poorer fat emulsification. The resultant imitation cheeses were softer, less cohesive and had reduced melting properties compared to the control. During processing, the pre-gelatinised starch competed with the rennet casein for water and impaired the caseins hydration as evidenced visually by delayed emulsification of free oil. Differences in levels of amylose retrogradation may have been responsible for variances in functionality between starches of different origins.     

Alteration of imitation cheese structure and melting behaviour with wheat starch

Imitation cheeses were manufactured with increasing levels (0–20%, w/w) of native wheat starch in partial or total replacement of rennet casein protein. With increased addition of native wheat starch up to 9% (w/w), irregular starch particles (sometimes horseshoe-shaped) became more numerous and disruptive of the protein structure. Differential scanning calorimetry showed the presence of a large endothermic peak at 42 °C, corresponding to the melting of the palm oil constituent, and a smaller second endotherm at 79–82 °C with the inclusion of starch at levels of up to 9% (w/w). This smaller endotherm was not present on heating imitation cheese containing 20% (w/w) starch, which had no meltability. Results indicated that the second smaller endotherm corresponded to a phase transition in the casein-continuous matrix facilitating flow behaviour in the imitation cheese network. At concentrations of 3–9% (w/w), wheat starch behaved like a filler material, with limited effects on the rheology of the casein matrix at temperatures below 50 °C, however its inclusion increased the processing time and reduced the meltability of the imitation cheese.     

Effects of emulsifying salts reduction on imitation cheese manufacture and functional properties

Imitation cheese (48%, 50% and 52% moisture) was manufactured using a Farinograph. The standard emulsifying salts (ES) concentration was 1.4%, giving a casein:ES ratio of 19:12. The effect of ES reduction on cheese manufacture and functionality, assessed by texture profile analysis, heat-induced flowability and dynamic rheology, was studied. Microstructure was investigated by light and cryo-scanning electron microscopy. Reducing ES increased processing time and hardness and decreased flowability and fat globule diameter. In comparison to standard ES, a reduction of up to 20% produced cheeses in reasonable processing times with slightly altered functionality. On further ES reduction, processing times greatly increased giving much harder and less meltable cheeses. Reducing ES by 40% increased processing times ∼3-fold, halved fat globule diameter and flowability and doubled hardness, compared to standard cheeses. At ES reduction above 40% the product obtained, after prolonged processing time, bore little resemblance to cheese.     

工艺参数对再制干酪的质构和流变性质的影响

利用质构仪和流变仪对影响再制干酪品质的多个因素进行了研究。结果表明，水分影响再制干酪的质构和流变性质：乳化盐对再制干酪产品的质构没有显著的影响；不同的温度和不同的搅拌时间对样品的质构有着相似的变化；在所有加工条件下．再制干酪的G′始终大于G″，G′和G″没有交叉点，而且复合黏度η^＊随着频率的增加而急剧降低，体系表现出了弱凝胶的特性。     

Inclusion of starch in imitation cheese: Its influence on water mobility and cheese functionality

The impact of starch type and concentration on the nature of water in and the rheology of imitation cheese were investigated. Imitation cheese (55% moisture) containing four starches (native, pre-gelatinised, resistant or waxy corn) at inclusion levels of 1.9%, 3.9%, 5.8%, 7.8%, or 9.9% w/w were manufactured using a Brabender Farinograph-E^®. The textural properties were assessed by torsion gelometry and dynamic rheology and the mobility of water by nuclear magnetic resonance (NMR) relaxation techniques. Cheese microstructure was assessed using light microscopy. Increasing the starch content changed the texture of cheeses from ‘soft’ to ‘brittle/tough’ and significantly (p<0.05) decreased the mobility of water. Cheese melt and hardness were influenced by the mobility of water. Matrices in which the water was more mobile produced good melting soft cheeses, while cheeses in which water was less mobile were tough and non-melting. Light micrographs showed that starch type influenced cheese microstructure. The native and pre-gelatinised starches became swollen and disrupted the continuity of the protein matrix, separating the matrix into a protein and starch phase. Resistant and waxy corn starches were present in the protein matrix as small discrete particles, appearing relatively intact, unswollen and relatively unchanged by the cheese manufacturing process. The study indicates that varying the level/type of starch alters the water mobility and thus the functionality of imitation cheeses.     

Crispiness of a microwave-expanded imitation cheese: Mechanical, acoustic and sensory evaluation

The objective of this study was to determine the crispiness of microwave-expanded imitation cheese and compare the results with sensory evaluation. Three cheeses were manufactured with 36%, 19%, or 15% protein; all three with 0% fat, a fourth cheese had 4% fat and 19% protein. After 3 and 9 days of storage at 5 °C, the cheeses were subjected to microwaving and the volumetric expansion, mechanical, acoustic and sensory crispiness of the expanded products was determined. The expansion and crispiness increased with increasing heating time and decreased with decreasing protein content. The expanded cheese with the highest protein (36%) and the cheese with 4% fat were considered the most and the least crispy respectively by mechanical, acoustic and sensory evaluation. Crispiness of the microwave-expanded imitation cheese was influenced by the protein content and the degree of plasticisation of the cheese matrix.     

Reducing salt in imitation cheese: Effects on manufacture and functional properties

Imitation cheeses (48% moisture, 0-1.5% NaCl) were manufactured using a Farinograph or Blentech cooker. The effects of NaCl reduction on cheese manufacture, functionality (assessed by texture profile analysis, flowability, dynamic rheology and microscopy), microbiological stability and sensory attributes were investigated. Reducing NaCl concentration decreased processing times and mixing energy required during manufacture and, post-manufacture, decreased cheese hardness, G′ values at 25 °C and crossover temperature and increased fat globule size. Cheeses from both cookers showed the same trend in functionality. Microbial stability was reduced at 0% NaCl, and the sensory panellists preferred the 50% reduced NaCl cheese to the standard.     

Effect of moisture content and water mobility on microwave expansion of imitation cheese

The effects of moisture content (60–45%), and refrigerated storage (1–9 days) on the functional properties, water mobility and microwave expansion of imitation cheese are investigated. Cheese hardness, elastic (G′) and viscous moduli (G″) increased with decreasing moisture content and decreased during storage. Flowability, loss tangent (tan δ) and water mobility decreased with decreasing moisture content and increased during storage. Microwave expansion of imitation cheese decreased with decreasing moisture content and increased with prolonging storage time prior to microwaving. The changes in texture, rheology and flowability of cheese with decreasing moisture content, changes in water mobility and storage time reflected the level of cheese plasticisation by water and had strong linear correlations with microwave expansion. This work provides evidence that moisture content influences microwave expansion of imitation cheese by providing the driving force for expansion and plasticising the cheese matrix.     

利用稳定剂复配改善模拟干酪质地特性的研究

为解决模拟干酪的质地比天然干酪差的问题,研究了在模拟干酪配方中添加稳定剂的单因素试验,研究发现使用单一稳定剂的模拟干酪出现弹性较弱、黏聚性较差、添加量过多时产品过硬等缺陷,所以本试验通过对稳定剂进行复配,来改善产品质地,在单因素基础上,采用{3,2}单纯格子设计法对卡拉胶、刺槐豆胶和瓜尔豆胶3种稳定剂进行复配试验,通过检测硬度、弹性、黏聚性和感官评分,获得最优稳定剂的配比,结果为复配稳定剂添加总量为0.40%,卡拉胶、刺槐豆胶和瓜尔豆胶的质量比为1∶0.91∶1.02时,模拟干酪感官评价最好。这是由于稳定剂间的协效性,使模拟干酪质地方面更接近天然干酪。     

Development of the structure of an imitation cheese with low protein content

The structure of an imitation cheese with low protein content was developed by replacing 80% of the rennet casein with waxy maize starch and κ-carrageenan in the formula. Starch was partially hydrolyzed by using a fungal α-amylase to provide meltability. Formulation studies were carried out to obtain meltability and textural properties of a hard cheese with high protein content in the developed cheese. Response surface method was used to determine the effects of α-amylase and κ-carrageenan on the physical properties of the cheese. Hardness, cohesiveness and springiness of the cheese were affected positively by κ-carrageenan and negatively by α-amylase. Square of the meltability scores was used to explain the effects of components on meltability of the cheese. Square of the meltability was affected positively by α-amylase and negatively by κ-carrageenan. A formula was determined by using multiple response optimization method that would provide hardness, cohesiveness and meltability in the developed cheese similar to those of the high protein counterpart used as targets. Results obtained from a trial cheese produced according to the determined formula confirmed that the values of physical properties estimated by the optimization can be achieved.     

Phase structures impact the rheological properties of rennet-casein-based imitation cheese containing starch

The dynamic rheological and microstructural properties of rennet-casein-based imitation cheeses containing various concentrations of potato starch were investigated using a stress-controlled rheometer and confocal laser scanning microscopy. The influence of added starch on the size of the oil droplets in the imitation cheeses was also examined. Imitation cheeses with 0–15% protein replaced by starch were processed in a Rapid Visco Analyser (RVA) at 90 °C for 10 min at a shear rate of 800 rev/min and were then evaluated using oscillatory shear measurement and a temperature sweep (20–90 °C). The storage modulus (G′) of the rennet casein imitation cheeses increased abruptly at added starch concentrations >4%. In the temperature range 20–90 °C, tan δ of the imitation cheeses decreased with increasing starch concentration and was <1 at added starch concentrations >4%. A binary continuous phase consisting of a protein phase and a starch phase was observed in systems containing >4% starch, whereas the starch was dispersed in the protein matrix as small particles of irregular shapes at added starch concentrations ≤4%. As the dispersed phase, the size of the oil droplets increased with starch addition in the imitation cheeses. The marked increase in G′ and the reduction in tan δ may be attributed to the formation of a binary continuous separated phase structure in imitation cheeses containing added starch that is driven by thermodynamic incompatibility between rennet casein and starch.     

High-pressure effects on the microstructure, texture, and color of white-brined cheese

Abstract: White‐brined cheeses were subjected to high‐pressure processing (HPP) at 50, 100, 200, and 400 MPa at 22 °C for 5 and 15 min and ripened in brine for 60 d. The effects of pressure treatment on the chemical, textural, microstructural, and color were determined. HPP did not affect moisture, protein, and fat contents of cheeses. Similar microstructures were obtained for unpressurized cheese and pressurized cheeses at 50 and 100 MPa, whereas a denser and continuous structure was obtained for pressurized cheeses at 200 and 400 MPa. These microstructural changes exhibited a good correlation with textural changes. The 200 and 400 MPa treatments resulted in significantly softer, less springy, less gummy, and less chewy cheese. Finally, marked differences were obtained in a* and b* values at higher pressure levels for longer pressure‐holding time and were also supported by ΔE* values. The cheese became more greenish and yellowish with the increase in pressure level. Practical Application: The quality of cheese is the very important to the consumers. This study documented the pressure‐induced changes in selected quality attributes of semisoft and brine‐salted cheese. The results can help the food processors to have knowledge of the process parameters resulting in quality changes and to identify optimal process parameters for preserving pressure‐treated cheeses.     

模拟Mozzarella干酪工艺参数优化的研究

模拟Mozzarella干酪是一种类似天然干酪的产品。为使其品质更接近于天然Mozzarella干酪,研究了以干酪的质构、融化性、拉伸性和油脂析出性为指标,对生产工艺中的几个关键工艺参数进行优化。结果表明,融化温度、搅拌时间和搅拌速度对模拟Mozzarella干酪未融化时的物理特性和融化时的主要功能特性都有极显著性影响(P<0.01);融化温度为85℃,搅拌时间(加柠檬酸前)为5min,搅拌速度为250r/min时加工的模拟干酪的品质最接近于天然Mozzarella干酪。因此,在模拟Mozzarella干酪的加工工艺中选择融化温度85℃,搅拌时间5min,搅拌速度250r/min。     

Flavouring of imitation cheese with enzyme-modified cheeses (EMCs): Sensory impact and measurement of aroma active short chain fatty acids (SCFAs)

Enzyme-modified cheeses (EMCs) are used to impart flavour to imitation cheese products. Cheeses (pH 6 or 5.5) were formulated with 5% w/w EMC, having low, medium or high levels of lipolysis and were examined by a sensory panel. Free fatty acid analyses were performed using SPME/GC. The flavour profile of the flavoured cheeses was affected by EMC composition and pH of the cheese base. Cheeses at a pH of 6.0, flavoured with low lipolysis EMCs, were described as ‘bland’. Lowering the pH of the cheese matrix to 5.5 appeared to increase the flavour intensity of the cheese flavoured with low lipolysis EMC and panellists ranked this cheese the highest, describing its flavour as ‘well-balanced and ‘cheesy’. This study shows that the flavours of imitation cheeses are influenced by the level of lipolysis of the EMCs used to flavour them and also by the pH of the cheese base.     

Effect of cation, sodium or potassium, on casein hydration and fat emulsification during imitation cheese manufacture and post-manufacture functionality

Imitation cheeses (48 g moisture/100 g cheese), in which the salt (NaCl) and sodium emulsifying salts were partially or wholly replaced with their potassium equivalents were manufactured. The effect of the replacement on manufacture and post-manufacture functionality (microstructure, texture, flowability, dynamic rheology and NMR T₂ relaxometry) was assessed. The replacement of sodium salts with potassium equivalents led to decreased torque values throughout the manufacture and to slight changes in functional properties including increased fat globule size and flowability, decreased hardness and cohesiveness. The potassium-salt cheeses exhibited adhesiveness, which was absent in the standard cheese, and also showed lower microbial stability.     

The effect of varying fat content on the microstructure of Oaxaca cheese,a typical pasta filata cheese

The effect of varying fat content in Oaxaca cheese, a typical pasta filata, on microstructure was described. Microstructure of cheeses was analysed by scanning electron microscopy (SEM) and light microscopy (LM) in nondehydrated and dehydrated samples. In nondehydrated samples, protein fibres were wide and compact in fat‐free cheese, and big serum channels were approximately 100 μm in width. Width of protein fibres and size of channels decreased as fat content increased. Small channels seemed to be occupied only by fat, while in big channels, water and fat were observed. LM both confirmed and supplemented the observations made by SEM, particularly the presence and distribution of fat in channels.     

Casein hydration and fat emulsification during manufacture of imitation cheese, and effects of emulsifying salts reduction

The manufacture of imitation cheese in a Farinograph was interrupted at various times, and the casein matrix formed and the free liquid were collected and analysed. During manufacture, a torque profile was generated, which showed three distinctive stages; an initial torque peak “peak-1”, followed by a trough and finally a second “peak-2”. Analyses provided quantitative and qualitative evidence that the initial manufacturing stage (peak-1) was concerned with water uptake and the formation of a hydrated casein matrix, as ∼75% of the added water was absorbed. This was followed by a fat emulsification phase (trough) and, once sufficiently emulsified, by the incorporation of the fat to form a homogeneous cheese mass, at peak-2. A similar approach showed that the effect of emulsifying salts reduction was to retard casein hydration, reflected in an increase in peak-1 torque, and led to a prolonged mixing time to sufficiently emulsify fat and allow its incorporation.     

Effects of freezing and frozen storage on the microstructure and texture of ewe's milk cheese

Semi-hard ewe's milk cheeses, frozen immediately after manufacture either slowly at –35 °C or rapidly at –80 °C and stored at –20 °C for 4 months were studied for microstructural and textural characteristics during subsequent ripening. Two control groups were used to establish the effect of freezing: the fresh unfrozen cheese and cheese thawed immediately after freezing. Freezing proper did not result in any marked changes in the textural parameters of the cheeses, but considerable changes were found in slowly frozen cheeses after 4 months of frozen storage. Shear strength values were lower in all frozen and stored cheeses, particularly in cheese samples frozen slowly compared to those in the unfrozen control batch. This parameter and firmness values were significantly lower in both slowly and rapidly frozen cheeses at the completion of ripening. Ripening tended to offset differences in elasticity, noticeable in the cheeses during the first 30 days of ripening. Light microscopy and electron microscopy revealed small cracks and ruptures in the cheeses which could not be observed by the naked eye. More extensive damage to the cheese microstructure was found in slowly frozen cheese samples stored frozen for 4 months.     

Effect of chelating salt type on casein hydration and fat emulsification during manufacture and post-manufacture functionality of imitation cheese

Imitation cheese (50% moisture) was manufactured in a Farinograph using different ratios of disodium orthophosphate (DSP) and trisodium citrate (TSC) as chelating or emulsifying salts (ES). The ES:casein ratio was kept constant at 0.2549 mol ES/kg casein. The effects of DSP:TSC ratio on cheese manufacture and post-manufacture functional properties were investigated. Hardness, assessed by texture profile analysis, heat-induced flowability and dynamic rheology were studied. Microstructural analyses were performed using light and cryo-scanning electron microscopy. Increasing the DSP:TSC ratio from 0:1 to 1:0 caused a decrease in processing times (from ∼18 to 12 min) and lowering of the final mixing torque values (from ∼180 to 20 F.U.) and, post-manufacture led to a decrease in cheese hardness (from ∼360 to 165 N) and G′ values at 25 °C (from ∼81 to 38 kPa) and to increased cheese fat globule size (from ∼8 to 32 μm). The results suggest that changing the ratio of DSP:TSC may be used to alter cheese properties, but both ES are needed for optimum functionality.