Comparison of Full-Fat and Low-Fat Cheese Analogues with Or Without Pectin Gel Through Microstructure, Texture, Rheology, Thermal and Sensory Analysis

International Journal of Food Science and Technology 2008, 43, 1581–1592 1581

Original article Comparison of full-fat and low-fat cheese analogues with or without pectin gel through microstructure, texture, rheology, thermal and sensory analysis

He Liu,1,2 Xue Ming Xu1,2* & Shi Dong Guo2

1 The Key Laboratory of Food Science and Safety, Ministry of Education 2 School of Food Science and Technology, Southern Yangtze University, Jiangsu, Wuxi, China (Received 17 November 2006; Accepted in revised form 29 March 2007)

Summary The effects of pectin gel and protein base on processed semi-solid cheese analogues were studied through microstructure, texture, rheology, thermal analysis and sensory evaluation. Scanning electron microscopy revealed differences in the microstructure of processed cheese analogues. Samples made with full-fat contained higher concentrations of fat globules and were denser compared with low-fat cheese analogues with or without pectin gel. The pectin gel in the products acted as a linkage with other ingredients and made the products more compact and had less cavity compared with the products without pectin gel added. On rheological analysis, the full-fat products manifested a more solid-like form. The storage modulus of pectin gel sample was higher than that without pectin gel. All the samples’ rheological parameters were depending on the oscillatory frequency and temperature. In low-fat samples, pectin gel added or not affected the hardness, gumminess, chewiness and adhesiveness significantly. The pectin gel addition show positive effect to the texture profile of the low-fat cheese analogues. Through thermal analysis, the meltability and glass transition temperature of the processed cheese analogues were measured. The low-fat cheese analogue with pectin gel addition got the higher texture and mouthfeel scores through sensory evaluation. Keywords Cheese analogue, differential scanning calorimetry, low fat, microstructure, pectin gel, rheology, texture.

more readily adhere to nutritional guidelines concerning Introduction fat consumption. Largely influenced by health-related Cheese analogues or imitation cheeses contain edible oil concerns, there has been pressure on the food industry or fat emulsified in an aqueous protein phase. Cheese to reduce the amount of fat, sugar, cholesterol, salt and analogues are usually defined as products made by certain additives in the diet. Food manufacturers have blending individual constituents, including the non- responded to consumer demand and there has been dairy fats or proteins, to produce a cheese-like product rapid market growth of products with a healthy image. that can meet specific requirements. They are being used Low-fat dairy products, such as milk, yoghurt, ice cream increasingly because of their cost-effectiveness, attrib- and some cheese products have been available for uted to the simplicity in their manufacture and the several years. In cheese production, the removal or replacement of selected milk ingredients by cheaper reduction of fat adversely affects both the flavour and vegetable products (Bachmann, 2001). texture (Ehab et al., 2002). Therefore, several strategies Over the past decade, the consumption of low-fat have been proposed to improve the flavour and texture food products has become more than just a trend. In of low-fat cheeses. These strategies can be collected in view of the general consensus that the amount and type three titles (Drake & Swanson, 1995; Mistry, 2001): that of fat consumed is of importance to the aetiology of is making-process modifications; starter culture selection several chronic diseases (e.g. obesity, cardiovascular and use of adjunct cultures; and use of fat replacers. Fat diseases, cancer), it is not surprising that consumers replacers are ingredients that are intended to replace natural fats with the main objective of obtaining a *Correspondent: Fax: +86-510-85879711; reduction in the caloric value. They are categorised as e-mail: [email protected] fat substitutes which are fat-based and as fat mimetics

doi:10.1111/j.1365-2621.2007.01616.x 2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology 1582 Comparison of full-fat and low-fat cheese analogues H. Liu et al.

which are protein- and carbohydrate-based. Fat mimet- viscoelastic materials. The rheology analysis of cheese ics have often been recommended to be used in cheese samples had been carried out in many literatures products consisting mainly of microparticulated pro- (Paraskevopoulou et al., 2003; Romdhan & Eric, tein- and carbohydrate-based materials (Romeih et al., 2003; Govindasamy-Lucey et al., 2005). Thermal ana- 2002). lysis by differential scanning calorimetry (DSC) on As the introduction of Siebel & Sylvia (1996), pectin is cheese is scarce, but the DSC tests on gel were a purified carbohydrate product, obtained by aqueous introduced in the literatures (Deszczynski et al., 2003; extraction under mildly acidic conditions of some plant Normand, et al., 2003; Lazaridou et al., 2004; Ross material – usually citrus fruits and apples. Traditionally, et al., 2006). pectin is used as a gelling agent for jams and jellies. The The objective of this study was to determine the effects major parts of all pectin production are consumed by of pectin gel on the physical, composition of low-fat the fruit processing industry. Other traditional applica- cheese analogues and also to find the correlation between tions are confectionery products, dairy products, fruit these properties. The rheology properties and thermal preparations, bakery fillings. properties of the samples were also studied. The effects of New applications of pectin within the food area are the fat reduction on these properties were also deter- constantly developing, and fat replacement is one of the mined. At the same time, the possibility of pectin gel as a latest newcomers. SLENDID, a registered trademark fat mimetic addition to cheese analogue was examined. of Hercules Incorporated, was introduced in 1991 (Siebel & Sylvia, 1996). The SLENDID concept covers Materials and methods a range of specialty pectins tailor-made for fat replacement. The production of SLENDID takes place on the Materials premises of a company in Denmark. In 1994, the company was granted a patent covering a fat-simulating The casein and sodium caseinate were supplied by composition consisting of heat-stable carbohydrate gel Linxia Huaxia Dairy Products Co. Ltd, China. The particles, a food product normally containing fat ⁄ oil citrus low-methoxylated pectin gel was prepared by that has been improved by substituting all or a portion mixing the pectin with water and interacted with calcium of the fat ⁄ oil by gel particles, and the process by which ion to form a weak-gel Pectin was from Jaingxisheng the gel particles are formed. SLENDID may be used in Shangrao Fuda Pectin Co. Ltd, China. Other materials a wide range of food applications such as spreads, used for manufacture of the processed cheese anologues mayonnaises and salad dressings, processed meats, ice were (a) emulsifying salt and sodium chloride prepared cream, processed cheeses, soups and sauces, desserts and in laboratory and related material were from China bakery products, in which fat may be partly or fully Medicine (Group) Shanghai Chemical Reagent Cor- replaced. poration (b) nisin from Tianyu Group., China. (c) Use of scanning electron microscopy (SEM) tech- cheddar Paste 565-1 and (d) butter flavour from niques to cheeses and gels and evaluation of the product Chr.Hansen., Denmark. (e) colour from Wuhan Stars were successful in showing the microstructure (Sipahio- Modern Bio-engineering Co. Ltd, China. glu et al., 1999; Sanche et al., 2000). Texture properties of Cheddar cheese samples were determined using Production of protein bases compression and stress relaxation tests carried out on an Instron Universal Testing machine (Hort and Grys, The production of protein base and the processed cheese 2001). It is convenient to employ instrumental texture was as introduced by Muir et al. (1999). The emulsifying analysis in the current accepted form using uniaxial salts were dissolved in suitable quantity of water and compression. Literature introduced the texture profile poured into the glass beaker which was placed in a water analysis (TPA) test on cheeses and discussed the bath. The temperature was raised to 50–60 C, then a properties of the texture of the cheese samples (Ehab measured quantity casein or sodium caseinate was et al., 2002; Truong et al., 2002; Kealy, 2006). Rheology added to make the protein base using first a low-speed is mainly concerned with the relationship between mixer, then a high-speed mixer until the lubricous cream strain, stress and time. When subjected to external was formed. After overnight storage for 14–16 h at forces, solids (or truly elastic materials) will deform, 4 C, the protein bases were used in the production of whereas liquids (or truly viscous materials) will flow. processed cheese analogues. However, contemporary rheology is more interested in the behaviour of real materials with properties interme- Processed cheese analogue production diate between those of ideal solids and ideal liquids (Doraiswamy, 2002). These industrially important mate- After overnight storage, the protein bases had formed rials are called viscoelastic materials, which include gels. These gels were placed in a processing kettle (A. almost all real materials. Without question, cheeses are Stephan. U. Sohne GmbH, Germany); 2 kg capacity

International Journal of Food Science and Technology 2008 2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology Comparison of full-fat and low-fat cheese analogues H. Liu et al. 1583 and blended the other ingredients according to the Textural analysis recipes shown in Table 1. The ingredients were first mixed for 1 min at low speed, following application of Texture profile analysis parameters were determined by vacuum, the mixture was then heated to 70 Cwith using a texture analyser TA-XT2i (Stable Micro System, direct steam injection. The vacuum was then switched Ltd, UK). A flat plate probe (P ⁄ 0.5-Delrin cylinder off and heating continued to 90 C followed by mixing probe) with 0.5 inches of diameter was attached to at high speed for 2 min. The hot melted cheese was moving crosshead. Samples were not moved from the packaged in rigid plastic cups and heat sealed with cup and it was ensured that the height of the samples aluminium foil. All samples were cooled and stored for were identical by cut at least 1 cm away from cheese 2 months at 4 C. The complete experiment was repli- analogues surface. They were left at 25 C for about cated twice more on separate occasions. 30 min until they reached the definite temperature. The central temperature of a control specimen was measured by a thermocouple. The operating conditions were: Chemical analysis selecting TPA as test mode and option. Pretest speed ) ) The amounts of moisture, and ash in the cheese samples was 2.0 mm s 1, test speed was 1.0 mm s 1. Postspeed ) were measured by AOAC Official Method 926.08 (1995) was 5.0 mm s 1. Two bite time interval was 5.00 s. Trig and AOAC Official Method 935.42 (1995), respectively. type was ‘auto’. Trig force was 20 g. Acquisition rate was Total protein and total fat content of the cheeses were 200.00 pps, 20% of compression ratio from the initial determined using the Kjeldahl, and the modified Mo- height of the sample in two bites. The texture profile jonnier method, respectively (Marshall, 1992). The parameters were determined using the TPA curve, an protein content of cheeses was calculated by multiplying example, given in Fig. 1: the compressive force(g) the total nitrogen content by 6.38. recorded at maximum compression during the first bite as a measure of cheese hardness (Katsiari et al., 2002); the distance of the detected height of the product on the Microscopic analysis second compression divided by the original compression Scanning electron microscopy is a valuable technique in distance (Length 2 ⁄ Length 1) as a measure of springi- 2 dairy research because it provides information on ness; The negative force area (A3,cm) during the first microstructure of dairy products which can be related bite as a measure of adhesiveness (Antoniou et al., 2000); to physical properties. Small cubes of the cheese The ratio of positive area during the second compression analogues were fixed with 2.5% (v ⁄ v) glutaraldehyde to the positive area during the first compression (A2 ⁄ A1) in water for 1 h and rinsed three times with phosphate as a measure of cheese cohesiveness; the product of buffer. After that, the samples were then put in 0.2% hardness · cohesiveness as a measure of gumminess; the (w ⁄ v) OsO4 left overnight, rinsed three times with product of gumminess · springiness as a measure of phosphate buffer and dehydrated in a graded ethanol chewiness (Katsiari et al., 2002). Texture values were the series [(50–70–90–100)% (v ⁄ v); 20 min per step] and mean of three replicates tested each sampling time. placed in 100% (v ⁄ v) ethanol for an overnight. The samples were critical point dried through CO . They 2 Rheological analysis were then fractured and coated with Au by diode sputter coating. Micrographs were made with a QUANTA-200 Samples were put on the bottom plate of the rheometer (FEI) at an acceleration voltage of 10.0 kV. (TA Instruments AR-1000, UK) which was equipped with a 40-mm, plate–plate measuring system and a Table 1 Experimental recipes (%) for the production of processed 1000 lm spacing. To prevent evaporation and protect cheese analogues against dehydration during test of the samples, low- viscosity silicone oil was applied to the exposed surfaces Ingredient Ff Lf Lfc of the samples. Preliminary experiments were carried Casein ⁄ Sodium caseinate 15 15 15 out to determine the linear viscoelastic regions at which Butter 20 10 10 the frequency sweep of the samples was obtained. Pecin gel 0 10 0 Frequency sweep and temperature sweep were per- Emulsifying salt 2 2 2 formed and measured values obtained included G¢ Cheddar cheese flavour 1 1 1 (elastic modulus), G¢¢ (loss modulus) and tan d (loss Butter flavour 1 1 1 tangent = G¢¢ ⁄ G¢). Cheese analogue samples were sub- Nisin 0.01 0.01 0.01 jected to heating and cooling profiles: A strain of 5% Sodium chloride 1.5 1.5 1.5 was applied at a frequency of 1 Hz to the samples, the ) Water 60 60 70 heating and cooling rate used was 2 C min 1 at 20– Ff, full-fat cheese analogue; Lf, low-fat with fat mimetics cheese 60 C and the tan d values were obtained (Gunasekaran analogue; Lfc, low-fat control cheese analogue. and Mehmet Ak, 2003).

2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology International Journal of Food Science and Technology 2008 1584 Comparison of full-fat and low-fat cheese analogues H. Liu et al.

Figure 1 The typical TPA curve of full-fat cheese analogue (springiness = Length

2 ⁄ Length 1; adhesivness = A3; cohesiveness = A2 ⁄ A1; gumminess = hardness · cohesiveness; chewiness = gumminess · springiness). were evaluated for aroma (creamy, milky, acid), colour Thermal analysis (neutral, white), texture (presence of holes and eyes, Differential scanning calorimetry analysis was per- elasticity, stickiness) and mouthfeel (creamy, hard, formed with a DSC-7 calorimeter (Perkin–Elmer, Nor- crumbly). A five-point hedonic scale (5 = very good; walk, CT, E. U. A.) An empty pan was used as a 1 = very poor) was used for aroma, colour, and ten- reference. The samples (about 10 mg), previously weigh- point scale (10 = very good; 1 = very poor) for texture ted in aluminum pans, were analysed according to the and mouthfeel. following two independent program: (a) Heating from 25–80 C at a rate of 5 C ⁄ min and measure the meltabilities of samples. Temperature for the different Statistical analysis transitions (i.e. the onset temperature, To; ending A two-way analysis of variance for the data for chemical temperature, Te) were determined using the first deriv- analysis, textural, sensory analysis (the factors being the ative of the heat capacity calculated with the DSC pectin gel addition and the protein base) were carried out program library and by comparison with the baseline. to determine the significance of the individual differ- ) On the contrary, enthalpy (Delta H,Jg1) for solid– ences. Significant means were compared using F-test and liquid transition was estimated integrating the corres- standard deviations for mean values of chemical analysis ponding endothermic peak. (b) Heating from )25 to were also calculated. Simple correlations were performed ) 20 C at a rate of 10 C min 1, then cooling from 20 C between the textural, rheology, thermal properties and ) ) to )25 C at a rate of 10 C min 1, then a 10 C min 1 microstructure of the cheese analogue samples. All the heating rate scanning from )25 Cto)14 C and statistical analysis was conducted using the Matlab holding for 120 min, followed by cooling to )25 Cat (Version 6.5) commercial statistical package. ) 2 C min 1 before scanning from )25 Cto10Cat ) 2 C min 1. On basis of the last step, glass transition Results and discussion region might be detected and the Tg were determined by using the DSC programs. Composition of cheeses The composition of full-fat, low-fat with pectin gel and Sensory evaluation low-fat control cheese analogues were given in Table 2. A ten member sensory panel evaluated one cheese of The moisture of low-fat control cheese analogue each type at the end of the ripening period. The cheeses and low-fat cheese analogue with pectin gel were

Table 2 Percentage chemical composition of cheese analogue samples water content in the full-fat, low fat with pectin gel (mean ± SD) addition, and low fat without pectin gel addition cheese analogue (Table. 2), the full-fat cheese analogue in Moisture Ash Fat Protein Fat which water content were about 10% less than that in Base type Mean SD Mean SD Mean SD Mean SD low fat with or without pectin gel addition cheese analogues, the full-fat samples were more firm than the Sodium FfSC 0.608 0.008 4.707 0.242 17.257 0.086 17.213 0.445 low-fat and low-fat control samples and showed less caseinate LfSC 0.705 0.004 4.593 0.047 8.173 0.189 18.260 0.535 porous characteristic. The quantities of cavities in low- LfcSC 0.704 0.005 4.147 0.166 7.837 0.146 17.543 0.186 fat samples with pectin gel addition were less than those Casein FfC 0.597 0.007 3.573 0.060 18.033 0.110 18.217 0.398 LfC 0.687 0.012 3.530 0.115 9.690 0.155 17.470 0.780 in low-fat samples control. As introduced that a pectin LfcC 0.704 0.002 3.633 0.114 7.817 0.172 18.073 0.764 gel is formed when portions of homogalacturonan are SSE Base – *** – – cross-linked to form a three-dimensional crystalline Fat *** – *** – network in which water and solutes are trapped Pectin * * * – (Willatsa et al., 2006). Thus, the structure of formers looked denser. The results might be attributed to the FfSC, full-fat cheese analogue with sodium caseinate as protein base; effect of water entrapped in the pectin gel and formed a LfSC, low-fat cheese analogue with fat mimetic when the protein base is more continuous phase. The microstructure affects the sodium caseinate; LfcSC, low-fat cheese analogue control when the protein base is sodium caseinate; FfC, full-fat cheese analogue with mouthfeel, for the cheese, when the structure was more casein as protein base; LfC, low-fat cheese analogue with fat mimetic compact, the mouthfeel might be harder. Structures of when the protein base is casein; LfcC, low-fat cheese analogue control pectin were not observed in the SEM micrographs. when the protein base is casein. SSE, statistical significance of effect (F- Pectin was probably embedded in the protein matrix just test) from ANOVA; –, not significant. as the starch role in low-fat feta cheese (Sipahioglu *P < 0.05; **P < 0.01; ***P < 0.001. et al., 1999). significantly higher while their fat contents were lower Textural properties than those of full-fat cheese, as shown in Table 1. The water added to the recipe was higher than the water The mean values of the TPA parameters were given in added to the full-fat cheese analogues and fat was Table 3. Hardness was defined as the maximum peak reverse. The use of different protein base affected the force during the first compression cycle (first bite) and values of ash, and protein content. The means of ash con- had often been substituted by the term firmness. tent in sample with sodium caseinate as protein base Adhesiveness was defined as the negative force area were higher than that in sample with casein as protein for the first bite and represented the work required to base. The Na+ might contribute to this result. The protein overcome the attractive forces between the surface of a contents in all samples were not different significantly. food and the surface of other materials with which the food came into contact, i.e. the total force necessary to pull the compression plunger away from the sample. For Microscopic analysis materials with a high adhesiveness and low cohesiveness, Figure 2 showed that the type of protein base and water when tested, part of the sample was likely to adhere to content affected the microstructure of the cheeses. Three the probe on the upward stroke. Springiness (originally distinct structures: protein aggregates (P), fat globules called elasticity) was related to the height that the food (F) and cavities(C) (formed after water or air in the recovered during the time that elapsed between the end cheese was eliminated when the prepared cheese ana- of the first bite and the start of the second bite. logues were to run the SEM test) were observed in SEM Chewiness meant the amount of the energy required to micrographs of all cheese analogues (Fig. 2). Uniform masticate a solid food. This was the characteristic most protein aggregate networks were observed in full-fat difficult to measure precisely, because mastication cheese analogue samples as shown in Fig. 2a, d. The involved compressing, shearing, piercing, grinding, microstructure of full-fat samples with sodium caseinate tearing and cutting, along with adequate lubrication as protein base was different from the structure of full- by saliva at body temperatures. Cohesiveness might be fat ones with casein as the protein base. The fat globules measured as the rate at which the material disintegrated in former were smaller than those in the latter and this under mechanical action. Tensile strength was a mani- might be due to the emulsifying ability of sodium festation of cohesiveness. If adhesiveness was low caseinate was better than casein. Microstructures of low- compared with cohesiveness, then the probe was likely fat samples with or without pectin gel addition and to remain clean as the product had the ability to hold sodium caseinate as the protein base looked similar to together. Cohesiveness was usually tested in terms of the those with casein as the protein base of the protein secondary parameters brittleness, chewiness and gum- aggregates. Because of the significant differences in miness (from the instruments manual).

2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology International Journal of Food Science and Technology 2008 1586 Comparison of full-fat and low-fat cheese analogues H. Liu et al.

(a) (b)

Figure 2 Scanning electron micrographs of (a) Full-fat cheese analogue with Sodium Caseinate as protein base (FfSC), (b) Low-fat cheese analogue with fat mimetic when the protein base is Sodium Caseinate (LfSC), (c) Low-fat cheese analogue control when the protein base is Sodium Caseinate (LfcSC), (e) (f) (d) Full-fat cheese analogue with Casein as protein base (FfC), (e) Low-fat cheese analogue with fat mimetic when the protein base is Casein (LfC), (f) Low-fat cheese analogue control when the protein base is Casein (LfcC). The letters C, P, F by white arrow in ﬁgures denoted the cavity formed after water or air in the cheese was eliminated when the prepared cheese analogues were to run the SEM test, protein aggregate and fat globule in the cheeses, respectively.

The full-fat cheese analogues were significantly harder gel or only water. Compared with cheese analogues with than the low-fat cheese analogues whether with or or without pectin gel addition, it was inspiring that the without pectin gel addition. This meant that fat globules TPA parameters of low-fat cheese analogues with pectin reinforce the gel strenth of the cheese analogues. gel addition were more similar to full-fat cheese Although protein matrix content contributed to the analogue. This might due to the pectin gel formed hardness of cheese (Romeih et al., 2002), and the protein network which could maintain the firmness of the cheese contents were similar in all samples (Table. 2), it was not analogues. It was reasonable to state that the pectin gel a surprising result because water broke up the protein had the potential to imitate the role of fat in the cheese matrix and plays the role of lubricant to provide analogues but need further research on how to prepare smoothness and a softer texture. It was found that the the pectin gel to better act as fat mimetic in cheese higher the water content in the cheeses, the softer the analogues. samples. It was also found that the positive effect of Different protein base also showed effects on the pectin gel on the hardness of low-fat cheese analogues hardness, chewiness and guminess of cheese analogues. which could be attributed to both their ability of holding The samples with sodium caseinate as protein base were water and made the cheese more compact and harder. significantly higher than hardness, chewiness and gumi- As the fat content of cheese analogues decreased, all the ness of those with casein as protein base. The results TPA parameters except Springiness and Cohesiveness were supported by the microstructure of the samples decreased. The reason might be that the crystal fat (Fig. 2a, d) in which the protein micelle distributed globules which could contribute to the firm structure of differently. The likely comparison was found between the cheese analogues were partially substituted by pectin low-fat cheese analogues with different protein base.

Table 3 TPA (texture proﬁle analysis) parameters for different cheese analogues

Hardness(g) Springiness Cohesiveness Gumminess (g) Chewiness (g) Adhesiveness

ID Mean SD Mean SD Mean SD Mean SD Mean SD Mean SD

FfSC 681.11 1.8738 0.92 0.0354 0.55 0.0071 375.17 3.2173 4919.04 45.5942 )566.13 24.2654 LfSC 172.59 6.4456 0.90 0.0200 0.55 0.0100 94.68 2.7292 1193.00 47.6264 )88.03 2.6890 LFcSC 12.22 0.2515 0.94 0.0252 0.59 0.0115 7.18 0.0503 99.31 5.2622 )31.01 1.3583 FfC 307.34 23.6136 0.92 0.0473 0.54 0.0153 166.49 4.4666 2166.84 97.7403 )331.47 5.2124 LfC 105.19 2.7968 0.96 0 0.59 0.0058 62.14 0.0264 786.15 10.6930 )244.90 2.8094 LfcC 31.11 5.9404 0.95 0.0115 0.66 0.0361 20.43 0.7795 261.23 14.6051 )125.53 7.7138 SSE base – – – – – – SSE fat ** – ** ** ** SSE pectin ** – – ** ** ***

FfSC, full-fat cheese analogue with sodium caseinate as protein base; LfSC, low-fat cheese analogue with fat mimetic when the protein base is sodium caseinate; LfcSC, low-fat cheese analogue control when the protein base is sodium caseinate; FfC, full-fat cheese analogue with Casein as protein base; LfC, low-fat cheese analogue with fat mimetic when the protein base is casein; LfcC, low-fat cheese analogue control when the protein base is casein. Signiﬁcance of effect (F-test) from ANOVA; –, not signiﬁcant. *P < 0.05; **P < 0.01; ***P < 0.001.

10%. As shown in Fig. 3a, from 1% to 10% strain the Rheological properties complex modulus (G*) varied little. We selected 5% Rheological characterisation of cheese is important as a strain as the preference to perform oscillatory rheolog- means of determining body and texture characteristics ical analysis. and to determine how these parameters are affected by The changes in G¢,G¢¢ and tan d as functions of the composition, and processing techniques (Konstance & applied frequency for samples were presented in Fig. 3. Holsinger, 1992). Cheese analogues are viscoelastic Among the investigated parameters, G¢ and G¢¢ materials and their viscoelastic behaviour can be influ- increased when the frequency increased, whereas tan d enced by changes in their formulation caused by the decreased. As for G¢, the values of full-fat samples were incorporation of fillers which interact with the casein higher than the low-fat samples with pectin gel addition matrix in the curd (Lobato et al., 2000). Instrumental and the low-fat control samples were the lowest measurements of food texture are based on the food’s (Fig. 3b). Storage modulus (G¢) represents the solid-like rheological properties. Dynamic low amplitude strain or elastic character of a viscoelastic material such as testing offers very rapid result with minimal chemical cheeses. As water in cheese acts as a plasticizer, more and physical change. Small strain dynamic rheological water will make the cheese analogues plastic and vice methods have been used to define both the elastic and versa. Lowering the water content increases the inter- viscous nature of cheese. Such information is useful to molecular linkages by concentrating the proteins, characterise and differentiate cheese varieties (Tunick whereas a higher moisture content caused a swelling of et al., 1990). Such methods are implemented within the the casein matrix and decreases the molecular inter- linear viscoelastic region of the material and, therefore, actions and hence caused a lower G¢ value. Without are designed to be nondestructive to the basic structure considering the protein base type, the full-fat cheese of the material. Additionally, the elastic and loss moduli analogues had higher G¢ value. For the low-fat cheese become only a function of time and a function of the analogues, the samples with pectin gel added had higher magnitude of the stress or strain applied by performing G¢ value. It appeared that the firmness of cheese tests within the linear viscoelastic region (Tunick, 2000). analogues depend on three factors: the amount of water In low amplitude oscillatory shear experiments, the bound to the cheese analogues interior framework, the sample was contained between two parallel plates and fat content and free water. The much free water the underwent sinusoidally oscillating deformation as the samples had, the lower the G¢ of the samples. As it is lower plate was fixed while the upper plate was known that hydrocolloid has the ability to hold water oscillating at a specified frequency and transient and pectin gel had the good ability to entrap water. The responses were recorded. pectin gel addition lowered the free water content. So Rheology measurements were carried out in order to the result which the samples with pectin gel added had investigate cheese heterogeneity and to discriminate higher G¢ value when compared with those low-fat between the six cheese analogues. First, in order to cheese control was unquestionable. determine the linear viscoelastic region of the cheese As for G¢¢, the curves of full-fat samples were distinct analogues, strain sweep was performed between 1% and higher than low-fat ones. The curve of low-fat control

2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology International Journal of Food Science and Technology 2008 1588 Comparison of full-fat and low-fat cheese analogues H. Liu et al.

(a) (b) 30 000

10 000 LfcC 25 000 FfSC 9000 LfSC 8000 FfC 20 000 LfC 7000 LfcSC Strain sweep step 6000 15 000

5000 G' (Pa) |G*| (Pa) 4000 10 000

3000

2000 5000

1000

0 0 0 20 000 40 000 60 000 80 000 10 000 12 000 0.05000 100.0 % strain Frequency (Hz) (c) (d) 12 000 2.000

1.750 LfcC 10 000 LfcC FfSC FfSC LfSC LfSC 1.500 FfC 8000 FfC LfC LfC 1.250 LfcSC LfcSC 6000 1.000 G'' (Pa) tan(delta) 0.7500 4000 0.5000 2000 0.2500

0 0 0.05000 100.0 0.05000 100.0 Frequency (Hz) Frequency (Hz)

Figure 3 Oscillatary rheological characterisation of cheese analogue samples at 20 C: (a) linear viscoelastic region at a constant frequency of 1 Hz, (b) changes of G¢ (storage modulus) at different frequency, (c) changes of G¢¢ (loss modulus) at different frequency, (d) changes of tan d (loss tangent) at different frequency.

samples with sodium caseinate as protein base situated frequency increased. The samples which were low-fat the lowest position. (Fig. 3c). The low-fat samples with cheese analogues without pectin gel addition were solid- pectin gel addition and low-fat control samples show like only at higher frequency. Pectin gels played an similar curves. important role in the cheese analogues systems. The As for tan d, the curves situation were just reverse to cross-linking structure of the gels improved the solid- the G¢ vs. frequency curves of the cheese analogues like system through adsorption by protein (Marozienea (Fig. 3b, d). An increase in loss tangent indicated a and Kruif, 2000). change in the character of the cheese from solid-like to a Temperature sweep tests were performed and changes viscous- or liquid-like character. When the loss tangent of loss tangent during heating and cooling procedure equalled one, this meant that the systems were on the were shown in Fig. 4. The value of the loss tangent at crossover of G¢ and G¢¢. The tan d values of full-fat and higher temperature was used as index of meltability sodium caseinate based low-fat samples with pectin gel (Mounsey and O’Riordan, 1999). The value of the loss addition were all below one along with increasing of tangent at lower temperature may be used as index of frequency. This showed that these samples were more gelation. During the heating procedure, the loss tangent solid-like than liquid-like. Casein based low-fat sample values of low-fat control and casein-based sample with with pectin gel addition was liquid-like at initial pectin addition were all above one which showed that frequency and suddenly changed to solid-like when the samples were liquid-like. This result was consistent

(a) protein base which had no point of crossover of G¢ and 10.00 LfC G¢¢ and was solid-like throughout the cooling period. LfSC 9.000 FfC This phenomenon suggested that it was a thermal FfSC irreversible gel system and may be due to the properties 8.000 LfcSC LfcC of protein. The ﬁndings that the loss tangent of full-fat 7.000 cheese analogue with casein as protein base and low-fat 6.000 cheese analogue with same protein base and with pectin gel addition meanwhile decreased during the heating 5.000 procedure and increased during the cooling procedure tan(delta) 4.000 when the temperature was higher were abnormal. The 3.000 reason of the abnormality might be elucidated if a further study was carried out. 2.000

1.000 Thermal analysis 0 20.1 60.0 The effects of fat contents or pectin gel on the melting Temperature (°C) temperature, melting enthalpy and glass transition (b) temperature involved were determined by DSC (Fig. 5; 8.000 LfC Table 4). The increase of fat content had a positive LfSc influence on the melting enthalpy (Delta H) and 7.000 FfC FfSC negative influence on the onset melting temperature. LfcSC Because of the higher fat content, the Ff cheese 6.000 LfcC analogues needed more energy than the Lf cheese 5.000 analogues and manifested poor meltability. The low- fat cheese analogues with pectin gel addition had a lower 4.000 Delta H and this might be due to the pectin’s structure

tan(delta) that changed and released energy at a temperature of 3.000 about 40 C or the pectin interacted with fat or protein 2.000 and decrease the Delta H. As to the glass transition temperature (Tg), all samples’ Tg were approximately 1.000 )14.8 C and diﬀered not so much. Overall, the results of the thermal analysis were not according with the 0 19.9 60.0 theory hypothesis that higher moisture might decrease Temperature (°C) the Tg of the cheese analogue. This result might be due to the unsuitable of the measure means or complex Figure 4 Oscillatary rheological characterisation of cheese analogue interaction of the ingredient added to prepare the samples at heating and cooling procedure: (a) heating procedure, cheese analogues and this needs to further study and (b) cooling procedure. discussion.

Sensory evaluation with the data shown in the (Fig. 3d). At 25 C, the sodium caseinate-based samples with pectin gel addition As shown in Table 5, there were no differences ‘melted’ and full-fat cheese analogues’ melting temper- (p > 0.05) in aroma and colour characteristics between atures were higher than it at approximately 30 C. full-fat and low-fat cheese analogues. The panellists During cheese melting, the temperature at crossover found the differences in texture and mouthfeel between modulus was an indication of the ‘softening point’ of full-fat and low-fat cheese analogues with or without cheese, the onset temperature of rapid melt and flow. pectin gel addition. However, the full-fat and low-fat Low-fat cheese analogues’ meltability was better than cheese analogue without pectin gel addition were poorer full-fat samples because the moisture contents were in texture and mouthfeel as reflected by their lower higher and the structure of the samples was not so rigid. score. The lower score in mouthfeel and texture of full- With similar fat content, the sample with casein as fat samples was likely due to the denser microstructure protein base melted more easily and this may be due to which made the sample too hard. In addition, the lower the protein’s structure and other properties. During the score in mouthfeel and texture of low-fat samples cooling procedure, all samples showed a gel-like beha- without pectin gel addition might be due to the too soft viour and the temperature of the gelation was different feeling of the samples resulting from the high moisture (Fig. 4b) except for full-fat samples with casein as the level of the product. On all accounts, based on the

2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology International Journal of Food Science and Technology 2008 1590 Comparison of full-fat and low-fat cheese analogues H. Liu et al.

(a) 23.0

22.5

LfC: T = 39.241 T = 44.556 Delta H = 0.632 o e 22.0

21.5 LfcSC: T = 38.069 T = 46.541 Delta H = 1.249 o e

21.0

LfcC: T = 41.467 T = 42.215 Delta H = 1.094 o e 20.5

20.0 Heat flow endoup (mVV) Heat flow FfC: T = 37.162 = T = 45.794 Dekta H = ’.813 o e 19.5

LfSC: T = 41.766 T = 46.510 Delta H = 0.925 19.0 o e

FfSC: T = 45.727 Dekta H = 1.455 18.5 o

18.0 34.51 36 38 40 42 44 46 48 50 52 54 55.5 Temperature (ºC)

(b) 39.626

39.624

39.622

39.620

LfSC: T = -14.794 39.618 g

39.616 LfC:T = -14.803 g

39.614

39.612 FfSC: T = -14.790 g

39.610 Heat flow endoup (mVV) Heat flow Lfc C: T = -14.833 39.608 g

39.606 Lfc SC: T = -14.813 g Figure 5 DSC traces of cheese analogues 39.604 during the two different programs: (a) the 39.602 FfC: T = -14.793 g power varieties of the cheese analogues’ phase 39.600 transition, (b) the measurement of the glass –14.958 –14.90 –14.85 –14.80 –14.75 –14.70 –14.65 –14.60 –14.55 –14.5 Temperature (°C) transition region.

sensory evaluation results, the authors were optimistic to apply pectin gel to substitute partial fat to prepare Table 4 The onset temperature (To), ending temperature (Te), enthalpy (Delta H,Jg)1) of solid–liquid transition and glass transition tem- cheese analogues.

perature (Tg) of diﬀerent samples measured with diﬀerent scanning programs by DSC Conclusions

)1 ID To (°C) Te (°C) Delta H (J g ) Tg (°C) Fat reduction in semi-solid cheese analogues and the use

FfSC 37.833 45.727 1.455 )14.790 of pectin gel aﬀected low-fat samples in diﬀerent ways. LfSC 41.766 46.510 0.925 )14.794 Fat reduction and moisture augment caused the micro- LfcSC 38.069 46.541 1.249 )14.813 structure of low-fat cheese analogues obviously more FfC 37.162 45.794 1.813 )14.793 loose. The low-fat samples showed lower hardness, LfC 39.214 44.556 0.632 )14.803 gumminess, chewiness and adhesiveness and low-fat LfcC 41.467 42.215 1.094 )14.883 samples with pectin gel addition were more similar to the full-fat cheese analogues. Pectin gel addition showed FfSC, full-fat cheese analogue with sodium caseinate as protein base; that it can decrease the melt enthalpy of the samples LfSC, low-fat cheese analogue with fat mimetic when the protein base is sodium caseinate; LfcSC, low-fat cheese analogue control when the which may be due to the conformation or structural protein base is sodium caseinate; FfC, full-fat cheese analogue with change of pectin or pectin interacted with fat or protein casein as protein base; LfC, low-fat cheese analogue with fat mimetic to decrease the Delta H. The low-fat cheese analogue when the protein base is casein; LfcC, low-fat cheese analogue control made with pectin gel addition was well received by the when the protein base is casein. sensory panel. The properties of the low-fat cheese with

Table 5 Sensory characteristics of full-fat and low-fat cheese analogues Ehab, A.R., Alexandra, M., Costas, G.B. & Gregory, K.Z. (2002). Low-fat white-brined cheese made from bovine milk and two Aroma Colour Texture Mouthfeel commercial fat mimetics: chemical, physical and sensory attributes. International Dairy Journal, 12, 525–540. Base Fat type Mean SD Mean SD Mean SD Mean SD Govindasamy-Lucey, S., Jaeggi, J.J., Johnson, M.E., Wang, T. & Lucey, J.A. (2005). Use of cold ultrafiltered retentates for standard- Sodium FfSC 4.65 0.28 4.74 0.24 6.54 0.76 6.46 0.74 ization of milks for pizza cheese: impact on yield and functionality. caseinate LfSC 4.25 0.34 4.68 0.34 8.17 0.49 7.68 0.43 International Dairy Journal, 15, 941–955. LfcSC 4.34 0.35 4.57 0.46 6.37 0.66 5.43 0.48 Gunasekaran, S. & Mehmet Ak, M. (2003). Cheese Rheology and Casein FfC 4.57 0.37 4.59 0.60 6.73 0.65 6.23 0.39 Texture. New York: CRC Press. Hort, J. & Grys, G.L. (2001). Developments in the textural and LfC 4.20 0.42 4.73 0.51 8.39 0.75 7.89 0.68 rheological properties of UK Cheddar cheese during ripening. LfcC 4.12 0.22 4.63 0.41 7.81 0.52 5.47 0.46 International Dairy Journal, 11, 475–481. SSE Base – – – – Katsiari, M.C., Voutsinas, L.P. & Kondyli, E. (2002). Improvement of Fat – – * * sensory quality of low-fat Kefalograviera-type cheese with commer- Pectin – – * * cial adjunct cultures. International Dairy Journal, 12, 757–764. Kealy, T. (2006). Application of liquid and solid rheological technol- FfSC, full-fat cheese analogue with sodium caseinate as protein base; ogies to the textural characterisation of semi-solid foods. Food LfSC, low-fat cheese analogue with fat mimetic when the protein base is Research International, 39, 265–276. sodium caseinate; LfcSC, low-fat cheese analogue control when the Konstance, R.P. & Holsinger, V.H. (1992). Development of rheologi- protein base is sodium caseinate; FfC, full-fat cheese analogue with cal test methods for cheese. Journal of Food Technology, 46, 105–109. casein as protein base; LfC, low-fat cheese analogue with fat mimetic Lazaridou, A., Biliaderis, C.G., Micha-Screttas, M. & Steele, B.R. (2004). A comparative study on structure–function relations of when the protein base is casein; LfcC, low-fat cheese analogue control mixed-linkage (1 fi 3), (1 fi 4) linear ß-d-glucans. Food Hydrocol- when the protein base is casein. loids, 18, 837–855. SSE, statistical significance of effect (F-test) from ANOVA; –, not signifi- Lobato, C.C., Aguirre, M.E., Vernon, E.J. & Sanchez, G.J. (2000). cant. Viscoelastic properties of white fresh cheese filled with sodium *P < 0.05. caseinate. Journal of Texture Studies, 31, 379–390. Marozienea, A. & Kruif, C.G. (2000). Interaction of pectin and casein micelles. Food Hydrocolloids, 14, 391–394. Marshall, R.T. (1992). 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International Journal of Food Science and Technology 2008 2008 The Authors. Journal compilation 2008 Institute of Food Science and Technology