Texture development in cheese

Texture development in cheese By Saad Haleem

1. Cheese Texture Muhammad Saad Haleem

2. Introduction Texture is the primary quality attribute of cheeses Cheeses offer a variety of textures For each cheese type. “For example, Mozzarella cheese is “stretchy” or “stringy” and Parmesan cheese is "crumbly,” etc.” Major structure-forming constituent in cheese The casein matrix in which fat globules are entrapped. Water or serum is both bound to casein and fills interstices of the matrix. Factors contributing in cheese texture Scalding temperature Fineness of the curd Duration of stirring Acidity pH

3. Factors affecting cheese texture Lower pH of milk at the time of enzyme addition or that of the curd at milling results in harder cheese.(shown in fig a). Low acidity weakens the protein bonds through charge repulsion, as the negative charges on casein molecules increase with pH in the cheese structure. Higher fat and water content tends to weaken the protein structure in the cheese and vice versa. Increase in fat content results in smoother and softer cheese and increase in casein content results in firmer cheese.

4. Effect of pH on cheese texture (figure A)

5. Different Terms: Describe Cheese Texture Sensory Term Definition Adhesiveness Stickiness of sample in the mouth throughout mastication Brittleness Breakability of the sample at the first bite Creaminess The extent to which the cheese has a velvety mouthfeel Crumbliness The ease of fragmenting cheese into small particles Chewiness Number of chews required to swallow a certain amount of sample Cohesiveness Amount of deformation undergone by a material before rupture when biting completely through the sample using molars Firmness The force required to compress the cheese with the Finger.

6. Different Terms: Describe Cheese Texture Sensory Term Definition Graininess The extent to which the cheese is bitty towards the end of chewing Hardness Force required to penetrate the sample with the molar teeth Long/Longness Tendency to fracture only after a relatively large deformation Smoothness The smoothness of the cheese against the palate as it breaks down during mastication Thickness In-mouth consistency assessed as the force developed by the tongue during the compression of the food between the roof of the mouth and the tongue

7. Textural Changes during Storage Texture of many cheeses change almost continuously after it is manufactured due to the proteolytic action of the residual enzyme. Lawrence et al. (1987) list the following three factors as having an effect on cheese texture during ripening: (a) pH at which whey is drained from the curd. This determines the proportions of chymosin and plasmin in the cheese (b) Salt-in-moisture ratio that controls, along with temperature, the activity of residual rennet and plasmin in cheese (c) pH of cheese after salting

8. The textural changes in cheese during storage may be considered to occur in 2 phases; PHASE 1 (the first two weeks after manufacture) There is a rapid change during which the casein network is greatly weakened when only a single bond in about 20% of the αs 1 -casein is hydrolyzed. The resulting peptide αs 1 -I causes the initial softening of the cheese. This peptide is present in all types of cheeses, at least during the early stages of ripening. PHASE 2 (the period subsequent to the first two weeks) The proteolytic changes are fairly gradual. The extent of textural change during this phase is based on the rate of proteolysis and increase in pH. As each peptide is cleaved, two new ionic groups are generated. This reduces the amount of free water in the matrix by increasing the solvation of the protein chains. Thus, as the Cheddar-type cheese ages, it hardens, and the protein matrix becomes less cohesive.

9. The most notable change with age, due to proteolytic breakdown of the protein matrix, is; Decrease in fracture strain and springiness. Increase in creaminess. Texture development of cheese is affected by; pH (cheese pH has been described as the single most important factor that influences the texture). Storage temperature. Humidity conditions of Storage.

10. Chadder Cheese As the Cheddar-type cheese ages, it hardens, and the protein matrix becomes less cohesive. The changing texture of Cheddar cheese might be divided into three distinct stages corresponding to the commercial classification of mild , medium , and mature Cheddar cheese. (Hort and Grys , 2001) In fact, after 64 weeks the Cheddar cheese is very soft, having lost its structural integrity due to extensive proteolysis (Hort and Grys , 2001) Mozzarella Cheese: Mozzarella cheese is regarded as unripened cheese, it does undergo changes during storage; Due to the proteolytic breakdown of αs 1 - casein in Mozzarella cheese, the protein matrix is both reorganized and weakened , resulting in a softer, less elastic, and more meltable cheese. Insufficient proteolysis due to high salt content can cause “Curdy” texture in Mozzarella cheese (Olson, 1982).

11. Feta Cheese: During Feta cheesemaking, a relatively high concentration of rennet is used. This leads to high aggregation rate and a coarse casein network that is responsible for the firm gel and cheese. In the Young Feta cheese , this firming effect is greater than the softening effect of proteolysis. As storage time is prolonged , the proteolytic effect increases to an extent that the cheese becomes softer and shorter

12. Measurement of Texture Instrumental measurements of “mechanical” characteristics, those that are manifested by the reaction of the foods to applied stress have been correlated with sensory attributes fairly well. The ten most frequently used texture terms in the United States are: Crisp Dry Juicy Soft Creamy Crunchy Chewy Smooth Stringy, and hard.

13. Texture measurement techniques can be grouped into Subjective technique Instrumental technique Subjective Measurements: Subjective measurements or sensory evaluation are made by the trained taste panel . Instrumental methods can be broadly grouped under the following three categories Empirical Imitative Fundamental. Empirical measurements Those tests that tend to relate a measured variable to a material property without a rigorous scientific basis. Example: Penetrometer, Puncture test, and Ball-compressor tests.

14. Imitative Methods The method in which may also be called semi-fundamental methods, include measurement systems that are used to make mechanical measurements with little control of experimental variables. Example:- Probe type and size, Product shape. The imitative methods are perhaps the largest group of instrumented texture-measurement methods. Fundamental methods These methods are employ valid rheological test techniques, and the data are analyzed using well-defined rheological, structural, and molecular theories. The fundamental test methods also yield results that are independent of test instrument. Some fundamental tests that are popularly used for texture evaluation include (Uniaxial compression, bending, and torsion tests) .

15. Texture evaluation of cheese depend upon Physical texture Sensory texture Physical texture evaluation classified liquid foods and Soft Cheeses Solid foods and Soft Cheeses liquid foods and Soft Cheese Successful correlations of fundamental measurement of rheological properties and sensory perception of viscosity or thickness, smoothness. Solid foods and Solid cheese Present an additional challenge because they require work of mastication before their texture can be perceived and even worse, the texture of solid foods changes during mastication. Mouthfeel of cheeses and fracture stress and toughness is influenced by the lubricating properties of the fats.

16. Sensory Texture Evaluation Involves an interaction between the food and the soft body tissues of fingers and mouth. In instrumented measurements, only the food material is deformed. Instrumented and other techniques are of restricted value in predicting the product characteristics as perceived by the consumers

17. Texture Profile Analysis The TPA test was performed using the General Foods Texturometer (GFT) that compressed the food sample in two successive deformations. by a flat plunger, to imitate the grinding action of the jaw, the plunger was driven. by an eccentric at constant speed; but the plunger traveled with a sinusoidally varying speed, coming to a momentary stop at both ends of the stroke. (Friedman et al.,1963). There are three textural characteristics of foods Mechanical Geometrical others The mechanical properties were further grouped as primary properties (hardness, cohesiveness, viscosity, elasticity, and adhesiveness) secondary properties (brittleness, chewiness, and gumminess).

18. The geometrical properties are those related to size and shape. the other properties are those pertaining to moisture content and fat content (e.g., oiliness and greasiness) of the product

19. TPA testing of cheese