Transcript
Influence of lipids, moisture content, whey protein, xanthan gum, guar gum and carob bean gum in Philadelphia cream cheese texture.
Harguindeguy, Maite
Department of Food Science, Oregon State University
Milk is a dispersion in which water is the continuous phase containing fat droplets, casein micelles, whey proteins, sugars and salts in the system. Due to its physicochemical complexity, milk can be used to produce a large range of products. The proteins in milk interact with salts like calcium, forming more complex structures called micelles. These casein micelles are negatively charged in the natural milk pH which keeps them apart and prevents their precipitation.
Casein is the basis of cheese making, the casein micelles are dispersed aggregates of the casein proteins together with mineral calcium and phosphate called colloidal calcium phosphate. (Lucey et al., 2003) To make cheese, the basic idea is rennin catalyzed cleavage of k-casein between 105 and 106 residues, phenylalanine and methionine. This leaves the C-terminal (hydrophobic) domain which will form the cheese matrix and the N-terminal (hydrophilic) domain which is going to be solubilized in the aqueous phase (whey). The C-terminal and N-terminal are Para-k-casein and Glycomacropeptide, respectively. Milk whey is a by-product of the cheese-making industry, which is about 85-95% of the milk bulk and contains nutrients such as lactose, soluble proteins, lipids, minerals, vitamins and organic acids. (Paraskevopoulou et al., 2003)
The manufacture of spreadable cheese process is achieved through breakdown of a primary paracaseinate network in natural cheese by the application of heat and mechanical action in the presence of emulsifying salts and proteins, resulting in its conversion into a fluid mass that can immobilize water and emulsify fat. (Dimitreli & Thomareis, 2008) A Schematic drawing of the structure cheese can be seen in picture 1 below.
Picture 1. Schematic representation of cheese protein matrix.
From: Lucey et al., 2003
It is common to use in many different food products proteins and polysaccharides together. In food emulsions, proteins are normally used to emulsify oil droplets while polysaccharides are used to increase viscosity, to obtain a gel-like product or to reduce particle mobility on the food (stabilize). (Hemar et al., 2001) Its observed that high methoxyl pectin can stabilize emulsions containing caseinate against precipitation upon acidification, and this was attributed to the formation of a pectin layer on the casein-coated oil droplet surface as a result of interactions with absorbed casein molecules through electrostatic forces.
The physical characterization of cream cheese is viscoelastic. (Dimitreli & Thomareis, 2008) To be characterized as cream cheese by the US Department of Agriculture, its content has to have at least 33% of milk fat, moisture content of no more than 55% and pH range of 4.4 to 4.9. Philadelphia regular spreadable cream cheese has in its composition milk fat, polysaccharides, salts, proteins as shown in Table 1.
INGREDIENTS: Pasteurized Nonfat Milk, and Milkfat, Cheese Culture, Salt, Stabilizers (Xanthan Gum, and/or Carob Bean Gum, and/or Guar Gum).
Table 1. List of Philadelphia regular spreadable cream cheese main ingredients.
The average shelf life of cream cheese, while the package is still closed, is one year. (Perveen et al., 2011) After open, the main alterations that influence the organoleptic characteristics of cream cheese are decrease in moisture content and pH variation due to microbial activity. Temperature has influence on various factors such as pH, titratable acidity (% lactic acid) and percent reduction in moisture content and microbial growth, which determines spoilage of cheese. (Perveen et al., 2011) As can be seen in Table 2, temperature has a significant impact on cream cheese pH, the lower the temperature the lower the pH variation in the period of 28 days. The temperature induced reduction in microbial activity and the rate of other chemical processes which delays deterioration in several respects: oxidation of lipids and fatty acid production by triglyceride hydrolysis and the generation of other organic products that spoil cream cheese sensorial characteristics.
Table 2. Changes in pH for different samples of cream cheese under different storage temperatures.
From: Perveen et al., 2011
Besides pH alteration, the titratable acidity increase implies food deterioration once the increase of this acidity is an indicative of microbiological growth. The increase on titrable acidity in cream cheese samples under different temperatures during the period of time of 28 days can be seen below in Table 3.
Table 3. The changes in titratable acidity (% lactic acid) of cream cheese during storage
From: Perveen et al., 2011
In addition to pH and titratable acidity variations during cream cheese storage, moisture content changes a lot during storage periods which has a substantial impact on cream cheese quality. As can be seen in the graph 1 below, in 28 days of storage, moisture content of cream cheese decreases radically from approximately 65% to approximately 40%. The moisture content affects dramatically the rheology of spreadable cream cheese once the increase of moisture gives cream cheese a more liquid-like behavior.
Graph 1. Decrease in moisture content of different cream cheese samples.
From: Perveen et al., 2011
Lipids, proteins and polysaccharides are the components that most determine rheological behavior of cream cheese. Its composition includes a polar phase and a non-polar phase dispersed as an emulsion. Philadelphia cream cheese has whey protein in its composition as already mentioned. These whey protein particles help to stabilize oil droplets dispersed in the cream cheese network. (Perez et al., 2010) The functional properties of whey proteins and caseins (related to emulsification) can also be modified by the addition of other components. Proteins and polysaccharides are two important structure forming ingredients in foods and there are synergistic effects between whey proteins and polysaccharides. (Rocha et al., 2009) Eelectrostatic complexation between oppositely charged proteins and polysaccharides allows better anchoring of the new-formed macro-molecular amphiphile onto oil-water interfaces. (Benichou et al., 2002) In fact, complexes made of proteins and polysaccharides exhibit many functional properties able to provide new food texture and stabilization methods. (Rocha et al., 2009)
Moisture content shows a contribution to a more liquid-like behavior of the system. Increasing moisture content decreases the coherence of the protein matrix resulting in products with a more liquid-like behavior. In the cream cheese matrix, the unfolding protein molecules are hydrated and bind water. The more added water, the more the proteins will swell and the greater their expansion due to reduce intrachain attractive forces. Additionally, the increase in protein solubility results in a higher sequestration capacity of emulsifying salts. They permeate more easily between casein molecules and disperse them in a superior degree leading to the formation of small hydrated protein molecules with weaker protein-protein interactions. While cooling, water molecules are restrained within the tridimensional protein matrix and weaken the structure of the final network. Thus, increasing moisture content reduces the coherence of the protein matrix resulting in the manufacture of products with more liquid-like behavior. The more casein in the system, the more they can interact in the cheese matrix increasing inter and intra strand linkages which make the system more elastic. (Dimitreli & Thomareis, 2008)
Fat, acting as a lubricant, also increases the liquid-like behavior of spreadable cheeses while the protein content in a solution is related to more solid-like behavior. In addition to that, when the moisture and fat content of a spreadable-type processed cheese were increased elastic and viscous moduli decrease. In contrast, proteins increase the linear visco-elastic properties. (Dimitreli & Thomareis, 2008) This means that greater moisture content weakens the rigidity of the cheese matrix which brings a more liquid-like behavior. (Lucey et al., 2003) Thus, moisture acts like a plasticizer and fat as a lubricant, both resulting in weaker protein matrix while proteins lead to the formation of a denser network with increased strength. (Dimitreli & Thomareis, 2008)
Besides the stabilizer properties of the polysaccharides added to cream cheese, these compounds interact synergistically with whey and casein proteins influencing the gel formation characteristics. The bean gum changes the whey proteins gels microstructure; this affects the aggregation and segregation equilibrium and the gelatinization time. Besides that, the presence of salt leads to enhancement in the gel strength in a bean gum – whey protein system. This happens due to interaction between sodium and casein proteins that lead to the formation of sodium caseinate (Na-CN), a great emulsifier due to its amphiphilic properties. However, stability of emulsion made with Na-CN is sensitive to protein concentration. (Hemar et al., 2001) The chemical structure of bean gum can be seen in Picture 2 below.
The interaction between xanthan gum and whey protein help to emulsify the system, once cream cheese is an oil-in-water emulsion. (Perez et al., 2010) The surface dynamic properties of milk whey protein (MWP) adsorbed films could be improved by macromolecular interactions with xanthan gum. (Perez et al., 2010) Comparing polysaccharides, it appears that pectin is less effective in stabilizing the system against precipitation and 'wheying off' can be observed in within a few days of storage, even when the polysaccharide is present at concentration level as high as 1%. By the other hand, xanthan gum is more effective as a stabilizer than guar gum at 0.2% concentration (Paraskevopoulou et al., 2003) but probably both are used in the cream cheese formulation due to pricing issues besides other enhance in characteristics that guar gum may offer. The chemical structure of xanthan gum and guar gum can be seen in picture 3 and 4 below respectively.
Picture 2. Chemical structure of Locust Bean Gum.
Picture 3. Xanthan gum chemical structure
Picture 4. Chemical structure of Guar Gum.
The increase of xanthan gum concentration causes extensive flocculation of fat droplets, but also improves the creaming stability of emulsions. This is probably due to the increase of viscosity of the continuous phase of the emulsion, which slows the diffusion rate of the droplets and flocks which results in a decreasing in the speed of creaming. (Hemar et al., 2001)
Locust bean gum modifies the microstructure of the whey protein gels by changing the equilibrium between aggregation and segregation. The gelation time is also decreased in the presence of very low amounts of locust bean gum (LBG). The volume of the protein-enriched phase decreases with the increase of LBG concentration and the protein concentration probably increases within that phase. For higher LGB concentrations, the gelation time is increased. The final structure of the gels is a result of the equilibrium between aggregation and segregation and the increase of the protein concentration on the protein-enriched phase. The whey proteins concentrate synergism with locust bean gum is affected by the protein hydrolysis. A small amount of LBG in the presence of salts leads to a big enhancement in the gel strength. (Rocha et al., 2009)
In sum, the cream cheese is a processed kind of cheese with different ingredients being added to enhance its rheological and sensorial characteristics. The milk and cheese culture are the original basis for the cheese making. The polysaccharides (guar gum, bean gum and xanthan gum) were added in order to improve texture and to stabilize the oil-in-water emulsion which constitutes the system. The whey protein added plays the role of emulsifying; reducing the interfacial tension in between both phases and also contributes to sensorial characteristics. Besides that, whey protein and polysaccharides have synergistic interactions that contribute to the cream cheese viscoelastic properties as already mentioned. In addition, salt has some effect in the emulsification of oil droplets, but also is added for flavor purposes.
The three polysaccharides cited in the formulation as "and/or" as seen have the same purpose and contribute in a similar way to the rheological properties of cream cheese although the synergistic interactions and the thickening ability of each polysaccharide shows some variance.
Works Cited
Dimitreli, Georgia, and Apostolos S. Thomareis. 2008. "Effect of Chemical composition on the linear viscoelastic properties of spreadable-type processed cheese." Journal of Food Engineering 84: 368-74.
Hemar, Y., M. Tamehana, P. A. Munro, and H. Singh. 2001. "influence of xanthan gum on the formation and stability of sodium caseinate oil-in-water emulsions." Food Hydrocolloids 15: 513-19.
Paraskevopoulou, A., I. Athanasiadis, G. Blekas, A. A. Koutinas, M. Kanellaki, and V. Kiosseoglou. 2003. "Influence of polysaccharide addition on stability of a cheese whey Kefir-milk mixture." Food Hydrocolloids 17: 615-20.
Perez, Adrian A., Cecilio Carrera Sanchez, Juan M. Rodrigues Patino, Amelia R. Rubiolo, and Liliana G. Santiago. 2010. "Milk whey proteins and xanthan gum interactions in solution and at the air-water interface: A Rheokinetic Study." Colloids and Surfaces B: Biointerfaces 81: 50-57.
Rocha, C., J. A. Teixeira, L. Hilliou, P. Sampaio, and M. P. Goncalves. 2009. "rheological and structural characterization of gels from whey protein hydrolysates/locust bean gum mixed systems." Food Hydrocolloids 23: 1734-745. Print.
Perveen, Kahkashan, Badriah Alabdulkarim, and Shaista Arzoo 2. 2011. "effect of temperature on shelf life, chemical and microbial properties of cream cheese." African Journal of Biotechnology 10: 16929-6936.
Benichou, Axel, Abraham Aserin, and Nissim Garti. 2002. "Protein-polysaccharide interactions for stabilization of food emulsions." Journal of Dispersion Science and Technology23.1-3: 93-123
Lucey, J. A., M. E. Jonhson, and D. S. Horne. 2003. "Invited Review: Perspectives on the basis of the rheology and texture properties of cheese." Journal of Dairy Science 86.9: 2725-743
`
