Microstructure, Rheological and Textural Characteristics of Low Fat Buffalo Milk Cheddar Cheese

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1 Microstructure, Rheological and Textural Characteristics of Low Fat Buffalo Milk Cheddar Cheese Mian Anjum MURTAZA a,b, *, Alistair S. GRANDISON b, Nuzhat HUMA b,c, Sarfraz AHMAD c and Mian Shamas MURTAZA c a Institute of Food Science and Nutrition, University of Sargodha, Sargodha-40100, Pakistan b Department of Food and Nutritional Sciences, University of Reading, Whiteknights, Reading, UK c National Institute of Food Science and Technology, University of Agriculture, Faisalabad-38040, Pakistan *Corresponding anjum_ft@yahoo.com/mian.anjum@uos.edu.pk ABSTRACT Buffalo milk is at the top in Indo-Pak milk production; however, not characterized and studied in depth. Cheddar cheese is produced in the world from cow milk and low fat product is preferred on compositional basis but fells short in quality. The study was designed to manufacture the low fat Cheddar cheese from buffalo milk and assess that how fat content affects its structure and rheology. Cheddar cheese was manufactured from buffalo milk standardized at 2% and 4% fat levels and was investigated for chemical composition, microstructure, hardness and rheological characteristics. Reduction in milk fat from 4% to 2% enhanced the moisture and protein levels and reduced the fat contents in cheese. Confocal scanning laser microscopy showed that the size and the number of non-spherical fat globules reduced on lowering the fat levels in cheese. Reducing the fat contents of buffalo cheese increased the elastic and viscous modulus at 20 C but no perceptible variations were observed at 40 C. The discrepancy in cheese rigidity (elastic and viscous modulus) might be owing to the modifications in gel network between buffalo milk proteins and fats that was consequence of variations in fat content and their distribution. Total hardness in low fat cheese found by compression and texture profile as g and g respectively was almost two times than of full fat cheese (340.00g and g, respectively). The established results have momentous variations as compared to those reported in cow milk cheese. Hence, it can be concluded that reduced fat buffalo milk produced cheese with acceptable textural and structural quality. Keywords: Buffalo milk, Cheddar cheese, fat content, microstructure, texture, rheology INTRODUCTION The ambition for caloric reduction in food, distinctively targeting the calories from fat, persuades the development of low-fat alternatives to traditional products (Rogers et al., 2010). Cheese is rich in fat food and some consumers hesitate to include it within diet, although it is an excellent source of dietary calcium (Johnson et al., 2009). Reduced and fat free cheeses are preferred due to their compositional profile but mostly their overall quality fell diminutive (Rogers et al., 2010). Fat in cheese is not only of nutritional importance but also confers the sensory and functional characteristics by playing an influential role in texture, flavor and aroma development in cheese (Mistry, 2001). However, reduction in fat content poses a negative impact on sensory characteristics and develops an unwanted rubbery and firm texture (Rogers et al., 2009). Studies are still underway to develop the techniques and alternatives for lucratively producing the reduced fat cheese. The consumers consider the rheological characteristics commonly referred as cheese body and texture as the imperative quality traits. In addition to flavor and appearance, the texture is a key feature of cheese quality (Messens et al., 2000). Being a solid food, Cheese has viscoelastic character, so it shows both viscous and elastic behaviors. This feature demands the performance of rheological and textural measurements of cheese (Pinho et al., 2004). Accepted April 10, 2013; Online February 24,

2 Buffalo s milk is rich in fat, lactose, caseins, calcium, magnesium and phosphate as compared to cow (Ahmad et al., 2008) and on account of the composition, it proffers exceptional prospects for the manufacturing of various milk products (Murtaza et al., 2008). Cheddar cheese is manufactured from cow s milk worldwide however; buffalo milk is at top in milk production of Pakistan and is more appropriate for the manufacturing of cheese (Murtaza et al., 2012). Many studies have conducted to produce and evaluate the low fat cheese from cow milk. However; investigations to manufacture reduced and low fat cheeses from buffalo milk are still deficient. The present research was designed to manufacture the low fat Cheddar cheese from buffalo milk and assess the impact of fat content on its microstructure, rheological and textural characteristics. MATERIALS AND METHODS Cheddar Cheese Manufacturing and Ripening Buffalo milk procured from Farm House, University of Agriculture, Faisalabad, Pakistan was standardized at 2.0% and 4.0% fat levels. Cheddar cheese samples were manufactured using direct in vat (DVS) Mesophilic starter cultures of CHR-Hansen, Denmark, following the standard protocol, with some modifications, as described by Rehman et al. (2000). Cheese was stored for ripening at 6-8 C for a period of 60 days. After ripening, samples were evaluated for chemical composition, microstructure, hardness and rheological characteristics. Chemical Composition Moisture, fat and protein contents were determined following the protocols of AOAC (1990). Cheese Hardness Hardness of cheese samples was evaluated by performing the compression and texture profile analysis (TPA) on texture analyzer (Texture Pro CT V1.2 Build 9, Brookfield Engineering Labs, Inc. USA) as described by O Mahony et al. (2005). Rheological characteristics Rheological analysis were performed on a Stress Tech controlled rheometer (ATS Rheosystems, Bordentown, NJ) fitted with a 20-mm smooth parallel plate geometry, according to the method of Rogers et al. (2009). Cheese samples were tested for temperature and time sweeps and their elastic and viscous modulus at 20 C and 40 C at 0, 5 and 10 minutes each. Microstructure Cheese microstructure was imaged using confocal scanning laser microscopy (CSLM) as done by Rogers et al. (2010). Cheese samples were sliced into sections approximately 5 mm 5 mm 1 mm thick using a razor blade. Fluorescent dyes Nile Red and phosphate Green (Invitrogen Molecular Probes, Eugene, OR) were used to image the fat and protein phases of the cheese, respectively. Samples were imaged using an inverted Leica TCS SP1 CSLM using a PL Fluotar oil UV objective (Leica Microsystems GmbH, Wetzlar, Germany). Statistical Analysis All the cheese samples were prepared and analyzed in triplicates and results drawn were statistically analysed using Analysis of Variance (Steel et al., 1997). RESULTS AND DISCUSSIONS Chemical Composition The composition of cheese showed that lowering the milk fat reduced the fat content in cheese (Table 1). As anticipated, moisture (38.29±0.21%) and protein (28.86±0.37%) contents were higher in low fat cheese as compared to full fat cheese (35.98±1.10% and 24.38±0.18% respectively). These variations contribute to discrete texture, microstructure and rheological characteristics (Rogers et al., 2009). Cheese Hardness Cheese hardness was the force required to compress the cheese sample to 30% of its original height during the first compression cycle. The hardness calculated by compression and TPA showed 1347

3 that half reduction in fat level increased the hardness up to double (Table 2). The increase in hardness was owing to the fact that low fat cheese has more dense protein network and firm hard texture (Rogers et al., 2009). However, the comparatively less hardness in buffalo cheese as compared to cow might be due to differences in fat globules size, distribution and composition (Menard et al., 2010). Rheological characteristics Regarding rheological characteristics, storage (elastic) modulus and loss (viscous) modulus increased on reducing the fat levels and similarly the tan delta values (ratio) were affected. However, the time sweep showed inverse effects on both modulus (Tables 3, 4 and 5). At start, the elasticity in low fat cheese was almost two times than full fat however, with time, the differences were reduced. At higher experimental temperature (40 C), the deviations among the full fat and low fat cheeses were not of that extent as at low temperature (20 C). It might be due to melting of fat at higher temperature. The variations in rheological parameters because of fat contents and temperatures are similar as reported by Rogers et al. (2010). The temperature behavior can be endorsed to the changes of fat from solid to fluid phase in cheese and modifications in protein network (Vithanage et al., 2009). Microstructure The CSLM images of cheese microstructure (Figure 1 and 2; having red and green colors representing fat and protein, respectively) showed that the size of fat globules decreased on reducing the cheese fat content and also showed variation in the shape of fat globules. Moreover, low fat cheese had more spherical fat globules dispersed all through the matrix, however; fat globules in full fat cheese emerged clustered and coalesced into non-spherical shapes. The globules dispersion in low fat cheese also supports the increase in elastic and viscous modulus. This imaging is comparable to the observations of low fat Cheddar cheeses by Guinee et al. (2000) and Rogers et al. (2010). CONCLUSION The present study characterized the low and full fat buffalo milk cheese and it was concluded that low fat cheese with acceptable texture and structure can be produced from buffalo milk. REFERENCES Ahmad, S., I. Gaucher, F. Rousseau, E. Beaucher, M. Piot, J. F. Grongnet and F. Gaucheron Effects of acidification on physico-chemical characteristics of buffalo milk: a comparison with cow s milk. Food Chem. 106: AOAC Official Methods of Analysis. 15th Edn. The Association of Official Analytical Chemists, Arlington, Virginia. Guinee, T.P., M.A.E. Auty and M.A. Fenelon The effect of fat content on the rheology, microstructure and heat-induced functional characteristics of Cheddar cheese. Int. Dairy J. 10: Johnson, M.E., R. Kapoor, D.J. McMahon, D.R. McCoy and R.G. Narsimmon Reduction of sodium and fat levels in natural and processed cheese: Scientific and technological aspects. Comp. Rev. Food Sci. Food Safety 8: Menard, O., S. Ahmad, F. Rousseau, V. Briard-Bion, F. Gaucheron and C. Lopez Buffalo vs. cow milk fat globules: Size distribution, zeta-potential, compositions in total fatty acids and in polar lipids from the milk fat globule membrane. Food Chem. 120: Messens, W., D. Van de Walle, J. Arevalo, K. Dewettinck and A. Huyghebaert, Rheological properties of high-pressuretreated Gouda cheese. Int. Dairy J. 10: Mistry, V Low fat cheese technology. Int. Dairy J. 11: Murtaza, M.A., S.U. Rehman, F.M. Anjum and H. Nawaz Nutritional comparison of cow and buffalo milk Cheddar cheese. Pak. J. Nutr. 7:

4 Murtaza, M.A., S.U. Rehman, F.M. Anjum, N. Huma, O.M. Tarar and G. Mueen-ud-Din Organic acids contents of buffalo milk Cheddar cheese as influenced by accelerated ripening and sodium salt. J. Food Biochem. 36: O Mahony, J.A., J.A. Lucey and P.L.H. McSweeney Chymosin-mediated proteolysis, calcium solubilisation, and texture development during the ripening of Cheddar cheese. J. Dairy Sci. 88: Pinho, O., E. Mendes, M.M. Alves and I.M.P.L.V.O. Ferreira Chemical, physical, and sensorial characteristics of Terrincho ewe cheese: change during ripening and intravarietal comparison. J. Dairy Sci. 87: Rehman, S.U., J.M. Banks, E.Y. Brechany, D.D. Muir, P.L.H. McSweeney and P.F. Fox Influence of ripening temperature on the volatiles profile and flavour of Cheddar cheese made from raw or pasteurized milk. Int. Dairy J. 10: Rogers, N.R., D.J. McMahon, C.R. Daubert, T.K. Berry, E.A. Foegeding Rheological properties and microstructure of Cheddar cheese made with different fat contents. J. Dairy Sci. 93: Rogers, N.R., M.A. Drake, C.R. Daubert, D.J. McMahon, T.K. Bletsch and E.A. Foegeding The effect of aging on low-fat, reduced-fat, and full-fat Cheddar cheese texture. J. Dairy Sci. 92: Steel, R.G.D., J.H. Torrie and D.A. Dickey Principles and Procedures of Statistics. 3rd Ed. A Bio-Metrical Approach, McGraw Hill Book Company, New York, USA. Vithanage C.R., M.J. Grimson and B.G. Smith The effect of temperature on the rheology of butter, a spreadable blend and spreads. J. Texture Stud. 40: Table 1. Chemical composition of Cheddar cheese. Parameters Full fat (4%) Low Fat (2%) Mositure (%) 35.98±1.10b 38.29±0.21a Fat (%) 38.28±0.11a 20.36±0.29b Protein (%) 24.38±0.18b 28.86±0.37a Table 2. Total hardness (g) of Cheddar cheese. Method Full fat (4%) Low Fat (2%) Compression ±27.06b ±16.43a TPA ±267.36b ±611.26a 1349

5 Table 3. Loss Modulus Values (Mean±SD) of Full and Low Fat Cheddar cheese (in KPa). C Time Full Fat Low Fat 0 min 1.06E+05 ± E+05 ± C 5 min 9.07E+04 ± E+05 ± min 8.50E+04 ± E+04 ± min 4.31E+04 ± E+04 ± C 5 min 1.19E+04 ± E+04 ± min ± E+04 ± Table 4. Storage Modulus Values (Mean±SD) of Full and Low Fat Cheddar cheese (in KPa). C Time Full Fat Low Fat 0 min 3.75E+05 ± E+05 ± C 5 min 3.08E+05 ± E+05 ± min 2.85E+05 ± E+05 ± min 1.04E+05 ± E+04 ± C 5 min 1.09E+04 ± E+04 ± min ± E+04 ± Table 5. Tan Delta Values (Mean±SD) of Full and Low Fat Cheddar cheese. C Time Full Fat Low Fat 0 min ± ± C 5 min ± ± min ± ± min ± ± C 5 min ± ± min ± ±

6 Figure 1. Microstructure of full fat cheese samples. Figure 2. Microstructure of half fat cheese samples. 1351