Progress 07/01/07 to 06/30/12
Outputs
OUTPUTS: "The impact of salt and calcium levels was studied on three different cheeses: Ragusano cheese that is made using a cooking stretching process (published in Journal of Dairy Science, Fuca et al 2012), Feta cheese (published in Journal of Dairy Science, McMahon et al 2009), and Cheddar cheese curd (published as a MS thesis, Utah State University, Lu 2012). Expulsion of whey from cheese was controlled by the shrinkage or expansion of the cheese protein matrix structure in relation to its chemical environment and temperature. Very low salt levels, low calcium levels and low temperature result in an expansion of the cheese matrix. As salt and calcium levels increase, and as temperature increases the cheese matrix contracts as corresponding more whey is expelled. The effect of temperature is partially reversible. The knitting together of cheese curd particles to form a smooth textured block of cheese was studied as a means of adding fiber into cheese. While 5% levels of various fibers (pectin, inulin, resistant starch, polydextrose) could be incorporated into the cheese, the texture of the cheese was unsatisfactory as the cheese curd did not knit together properly. We were unable to develop a process that would give the cheese a smooth texture. An alternative method for adding fiber into cheese was developed by incorporating the fiber within the inner droplets of an water-in-oil-in-water emulsion. This emulsion was added to low fat cheese (at a calculated 1.6% level) and it also improved the texture of the low fat cheese (published as PhD dissertation, Wadhwani 2012). As part of this work the color of low fat cheese was also studied with improvement in consumer liking improved when the cheese contained a combination of annatto (to give orange color) and titanium dioxide (to give opaqueness) (published in Journal of Dairy Science, Wadhwani et al 2012). Salt levels applied to cheese curd impacts the extent of whey syneresis by causing a contraction of the outer layer of the curd protein matrix. A flush of whey occurs after 3% (w/w) salt has been added to the milled curd. When lower levels are used (e.g. 2%), even if added all at once rather than over 3 applications, the whey expulsion is reduced dramatically (published as MS thesis, Lu 2012)." PARTICIPANTS: Nicoletta Fuca, CoRFiLaC, Sicily, Italy, participated in the work on changes in Ragusano cheese brought about by brining. Mahmoud Motawee, post-doctoral fellow, conducted research on effect of brining on feta cheese. Ranjeeta Wadhwani,PhD student, studied low fat cheese and strategies for adding fiber into cheese. Ying Lu, MS student, conducted trials on the impact of salt on cheddar cheese curd and consequent whey expulsion. TARGET AUDIENCES: US cheese manufacturing industry is the target audience, especially those involved in product development and technical services. This group will be reached through presentations at dairy science meetings, presentations sponsored by Dairy Management Inc., and annual meeting of Western Dairy Center. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
"The goal of this research was to add other nutrients such as dietary fiber into cheese. Our challenge was to develop a technology that would permit this while still retaining the good eating attributes of cheese. It has been impractical to add dietary fiber into the milk before it is converted into curd because too much is lost into the whey and not enough retained in the cheese. We had added the fiber by blending it together with the curd later in the process but the cheese was too crumbly when press together into a block. To enhance the sticking of cheese-fiber particles, we looked at how salt and calcium influence the cheese curd with the aim of getting them to knit together better. We were not able to solve the problem of blending fiber and cheese together to form a block of cheese that had the proper cheese texture using this process. There were still issues with the cheese having too gritty a mouthfeel. Some different mechanical treatment is needed that would reduce the cheese particles all the way to a paste. We did discover during this project other information that would be useful for cheese makers. Specifically we learned that the diffusion of salt into cheese and simultaneous expulsion of water during brining of cheese, such as mozzarella and feta, is not just a function of their relative concentrations in the cheese and in the brine, but is controlled by whether the protein matrix of the cheese contracts or expands. For example, when making feta cheese, we learned that temperature at which cheese is stored in the brine changes the weight of the cheese. If the cheese is kept too long at room temperature the cheese will shrink and lose weight, so it is important that the cheeses be cooled quickly. This can help cheese makers to increase their income by obtaining a greater yield of cheese from their milk. After our lack of success in adding dietary fiber directly to cheese we looked for another solution, and undertook some preliminary work to see if we could use a double emulsion technique to add the fiber to the initial milk without having it lost into the whey or interfering with the coagulation process. Usually, the fat in milk is in the form of stabilized oil droplets dispersed throughout the water (or whey) phase of the milk. These fat droplets are then trapped inside the cheese curd when the milk is coagulated. We found that we could incorporate even smaller water droplets (or droplets of a water-dietary fiber solution) inside the fat droplets, and that these would then be trapped in the curd during coagulation without most of the fiber going into the whey. This was effective in showing some improvement in the texture of a low fat cheddar cheese and has formed the basis of continuing research in this field. An additional benefit was we observed that low fat cheeses are typically translucent in appearance this is not liked by consumers especially when it is a colored cheddar cheese. For consumers to like a low fat cheese it is important that it have an opaque appearance. All these factors will need to be considered in order to make low fat cheeses with acceptable flavor, texture and appearance."
Publications
- Brown, K. M., McManus, W. R., & McMahon, D. J., (2012). Starch addition in renneted milk gels: Partitioning between curd and whey and effect on curd syneresis and gel microstructure: J. Dairy Sci., 95(12): 6871-6881. (Accepted).
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Progress 01/01/11 to 12/31/11
Outputs
OUTPUTS: Cheddar cheese curd was obtained after milling and salting. Soluble Ca was determined by mixing 5 g shredded cheese with 50 g deionized water, waiting for 10 min then filtering the slurry and measuring mineral content of the filtrate. A test solution for monitoring the movement of Ca from the curd was prepared by mixing whey obtained during cheddaring with deionized water (1:1), adding 42 g/L NaCl, and 1.0, 2.0, 10 and 20 g/L Ca as calcium chloride. Then a 100-g piece of curd was immersed in 300 g of solution for 6 or 18 h. Initial composition of the cheese curd was 405 g/kg moisture with a Na and Ca content of 6.2 and 6.9 g/kg respectively. The Ca was partitioned between soluble Ca contained in serum phase of cheese and insoluble Ca bound to proteins. Soluble Na and Ca concentrations were 15.1 and 9.8 g/kg moisture respectively. Insoluble Ca was calculated by difference as 8.8 g/kg solids. As was expected, Ca content increased in proportion to [Ca] of the solution and also affected (P<0.01) cheese moisture, total Na, [Na] in cheese serum, pH and weight of the cheese. Increasing time from 6 to 18 h influenced (P<0.01) the cheese moisture and weight but did not (P>0.3) affect Na and pH. There were significant (P<0.01) Ca x time interactions for all the above parameters. Most of the changes in weight, moisture, and mineral content of the cheeses occurred during the initial 6 h of immersion. With increasing Ca absorbed into the cheese the pH of the cheese decreased linearly from pH 5.3 at the lowest Ca level (1.0 g/L added Ca) to pH 4.9 at the highest Ca level of 20 g/L. This has been shown in previous research and is related to the release of protons as Ca2+ ions react with HPO42- ions and are precipitated as Ca3(PO4)2 and become part of the insoluble Ca associated with the protein matrix. Calcium content of the solution influenced (P<0.001) total Ca in the cheese as well as serum [Ca], insoluble Ca and the ratio of Ca to cheese solids. There was also significant (P<0.001) effects of immersion time and Ca x time interaction on serum [Ca] and total Ca in the cheese. However, neither insoluble Ca nor its ratio to cheese solids was affected by immersion time (P>0.6). Initially, the cheese curd contained, 6.9 g/kg total Ca, 5.2 g/kg insoluble Ca and had a soluble [Ca] of 4.0 g/kg moisture and Ca:solids ratio of 8.8. After 6 h of immersion in the test solution, the cheese immersed in the 5 g/L solution had a slightly lower Ca:solids ratio of 8.4, while that immersed in the 10 g/L solution had aslightly higher Ca:solids ratio of 9.1. With only 1 g/L of Ca in the solution, Ca was lost from the cheese while at 20 g/L of Ca, there was a large increase in Ca in the cheese. After immersion in the 10 g/L solution, the total Ca in the cheese was the same (5.2 g/kg) and the increase in total Ca (to 9.0 g/kg) was a result of the soluble [Ca] increasing to 7.6 g/kg of moisture. The observed increase in weight of the cheese after 6 h immersion can be attributed to either (1) an expansion of the protein matrix caused by a decrease in the Ca:solids ratio, or (2) a contraction of the protein matrix caused by an increase in the Ca:solids ratio. PARTICIPANTS: Ying Lu, MS student at USU, conducted trials to determine the calcium content needed in test solutions to maintain constant calcium:solids ratio in the cheese curd. Ranjeeta Wadhwani, defended a PhD dissertation that included strategies for adding fiber into cheese. Nicoletta Fuca, CoRFiLaC, Sicily, Italy, submitted a paper on changes in Ragusano cheese brought about by brining that was accepted for publication in the Journal of Dairy Science. TARGET AUDIENCES: US cheese manufacturing industry is the target audience, especially those involved in product development and technical services. This group will be reached through presentations at dairy science meetings, presentations sponsored by Dairy Management Inc., and annual meeting of Western Dairy Center. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The past challenge we have encountered when adding dietary fiber into comminuted cheese is that the curd particles do not re-knit together upon pressing (even when no fiber is present). This produces a cheese that has a gritty mouthfeel when eaten as the cheese breaks apart into individual curd particles. This work on expansion and contraction of the protein matrix in cheese curd suggests that if the calcium to solids ratio in cheese is reduced then the protein matrix will have a tendency to expand. Such an expansion may improve the tendency of curd particles to knit together after comminuting. When doing further work on cheese curd response to salt levels it is necessary to increase the calcium concentration in the test solution to about 10 g/kg because at lower levels , such as 2 g/kg typically added to brine solutions, there is still a loss of insoluble calcium from the cheese. This information will help cheesemakers understand the processes taking place upon addition of salt, or other ingredients, into cheese and how the proteins in the cheese respond to a change in chemical environment.
Publications
- UTAO+224 Fuca, N., McMahon, D. J., Caccamo, M., Tuminello, L., La Terra, S., Manenti, M., & Licitra, G., (2012). Effect of brine composition and brining temperature on cheese physical properties in Ragusano cheese: J. Dairy Sci., 95(1): 460-470. (Published).
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Progress 01/01/10 to 12/31/10
Outputs
OUTPUTS: An experiment was conducted in which low fat cheddar cheese was aged for 15 days then comminuted to 1.5 mm size particles. The cheese was mixed in 1.8-kg batches with 2 soluble dietary fibers, inulin and pectin, and 2 insoluble dietary fibers, polydextrose and resistant starch, with or without the addition of 5% water. These were then pressed in molds to reform into cheese blocks, vacuum packaged and stored at 4C. Then after 3 months the cheeses were analyzed for texture using a 2-bite texture profile analysis and after 6 months for texture and sensory properties by counting the number of bites necessary before swallowing. No liquid expulsion from repressed cheese mixed with fiber was observed which resulted in 100% retention of fiber in cheese except for polydextrose which experienced liquid expulsion of <0.5%. When added with water, cheese mixed with inulin or pectin resulted in better knitting and uniform mixing of cheese particulates which was confirmed by increased cohesiveness from 0.48 to 0.65 for inulin with water and 0.50 for pectin with water. Hardness for inulin (46 N) and pectin (56 N) cheeses were significantly lower than non-repressed control cheeses (81 N) and chewiness was also significantly reduced from 44 N to 12 N. Polydextrose and resistant starch cheese were poor in appeal and lacked smooth texture. Chewdown method showed that full fat cheese and comminuted cheeses required 12 bites before swallow whereas non-comminuted cheese control required twice as much chewing, i.e., 24 bites. PARTICIPANTS: Ranjeeta Wadhwani, PhD student at USU, has been conducting trials related to inclusion of four different fibers into comminuted cheese. Ying Lu, MS student at USU, has been conducting trials to determine the composition (pH, calcium, salt content) that can be used to test changes in cheddar cheese 1 day and 10 days after manufacture. Nicoletta Fuca, CoRFiLaC, Sicily, Italy, has continued to work with me on preparing a paper on changes in Ragusano cheese brought about by brining. TARGET AUDIENCES: US cheese manufacturing industry is the target audience, especially those involved in product development and technical services. This group will be reached through presentations at dairy science meetings, presentations sponsored by Dairy Management Inc., and annual meeting of Western Dairy Center. The information will be used in development of new cheese products for presentation to the dairy industry through Dairy Management Inc. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
In summary, inulin and pectin have some promise for adding to low fat cheese to provide dietary fiber content, while polydextrose and resistant starch too severely restricted the re-knitting of the curd particles together and produced an unsatisfactory cheese. There are still issues with the cheese having too gritty a mouthfeel that needs to be resolved. Comminuting cheese, mixing with fiber, and repressing into a block does not appear to be a suitable method for adding dietary fiber. The impact is that some better method(s) to increase the fusion of the cheese particles either by changing the nature of the cheese, or using different reforming techniques, is needed.
Publications
- No publications reported this period
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Progress 01/01/09 to 12/31/09
Outputs
OUTPUTS: During brining of feta cheese there is a change in cheese weight that is influenced by temperature, salt concentration of the brine, and initial cheese composition. Absorption of salt from brine accounted for some of the weight change, but this can be overshadowed by changes in cheese volume. All cheeses absorbed salt, and reached a moisture S/M level based on the amount of salt in the brine and the total moisture present in the brine and cheese, which for equal starting weights of cheese and brine was 4.6, 5.7 and 6.7 g/100 g for the 6.5, 8.0 and 9.5% brines, respectively. Cheeses brined at 3 C increased in moisture content whereas those brined at 22 C decreased in moisture content with intermediate changes occurring at 6 and 10 C. Fermenting cheese to a lower pH (4.83 versus 4.92) before brining partially prevented moisture uptake by the cheese such that when brined at 6 C, the cheeses had mean changes in moisture content of -0.8 and +4.1 g/100g, respectively. This trend would be expected to continue if initial pH of cheese dropped below pH 4.83. Cheese pH decreased during brining based on salt concentration and temperature, with no change occurring at 3 C in 9.5% brine and pH dropping to pH 4.15 + 0.03 in 6.5% brine at 22 C. Volume changes were mainly dependent on temperature with only slight increases in cheese volume as brine concentration increased. At 3 C, the cheeses expanded with increases in volume of 11 to 28% and had a cheese microstructure consisting of only a well hydrated protein matrix containing dispersed fat globules. In contrast, when brine at 22 C, the cheese shrunk from 1 to 17% as a consequence of a contraction of the protein matrix presumably because of increased protein-protein hydrophobic associations. Such cheeses had numerous serum pockets interrupting the protein matrix and increased presence of coalesced fat droplets. These changes in cheese during brining are only partially reversible when temperature is changed. In general, the cheeses will expand when the temperature is lowered, but initial exposure to 22 C for 10 d, inhibited expansion of the protein matrix when temperature was subsequently lowered to 3 C and the cheeses remain below their original weight and volume. Thus, temperature history as well as cheese pH before brining, brining temperature, and brine salt concentration all impact yield of feta cheese obtained after brining. PARTICIPANTS: A post-doctoral student from Egypt performed the feta cheesemaking and the brining experiment starting in 2008 and then in 2009 a paper was written for publication of the research. TARGET AUDIENCES: US cheese manufacturing industry is the target audience, especially those involved in product development and technical services. This group will be reached through presentations at dairy science meetings, presentations sponsored by Dairy Management Inc., and annual meeting of Western Dairy Center. The information will be used in development of new cheese products for presentation to the dairy industry through Dairy Management Inc. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Information from this portion of the research has shown that when feta cheese is brined after manufacture, its final composition depends on the salt concentration of the brine, the ratio of cheese to brine, and the temperature of the brine. Storing cheese at cold temperatures will increase its weight as brine is absorbed into the cheese as the protein matrix expands. Brining at room temperature can make the cheese block contract and lose weight. This demonstrates the dynamic state of the proteins in cheese immediately after manufacture and the importance of hydrophobic interactions in cheese. Selection of storage conditions of feta cheese in brine can be used for maximizing the yield of feta cheese.
Publications
- McMahon, D.J., H. Du, W. R. McManus and K.M. Larsen 2009. Microstructural changes in casein supramolecules during acidification of skim milk. J. Dairy Science 92:5854-5867.
- McMahon, D. J., M. M. Motawee, and W. R. McManus 2009. Influence of brine concentration and temperature on composition, microstructure and yield of feta cheese. J. Dairy Science 92:4169-4179.
- McMahon, D. J., Motawee, M. M., and W. R. McManus. 2009. Influence of brine concentration and temperature on composition, microstructure and yield of feta cheese. J. Dairy Science 92 (E-Supp. 1):263 (436).
- Motawee, M. M., and D. J. McMahon 2009. Fate of aflatoxin M1 during manufacture and storage of feta cheese. J. Food Science 74:T42-45.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: An experiment on how the protein matrix of cheese changes when subjected to different temperatures and salt concentrations was conducted using feta cheese curd as the cheese. This involved the brining steps and examining microstructure by laser scanning confocal microscopy. Statistical analysis was performed and a manuscript was partially written for publication. Statistical analysis was also performed on the previous experiment using Ragusano cheese. PARTICIPANTS: This experiment was performed in partnership with CoRFiLaC cheese research institute in Ragusa, Italy. A PhD student from Catania University, Italy is participating in the project and worked in my laboratory during the first half of the year. A post-doctoral student from Egypt worked on the project during May through December. TARGET AUDIENCES: US cheese manufacturing industry is the target audience, especially those involved in product development and technical services. This group will be reached through presentations at dairy science meetings, presentations sponsored by Dairy Management Inc., and annual meeting of Western Dairy Center. The information will be used in development of new cheese products for presentation to the dairy industry through Dairy Management Inc. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The protein matrix of cheese undergoes changes immediately following cheesemaking in response to addition of salt and lowering of temperature. Normally such changes are limited by the amount of water entrapped in the cheese at the time of block formation but for cheeses such as feta cheese, brine acts as a reservoir of water. Our objective was to determine the extent to which the protein matrix expands or contracts as a function of salt concentration and temperature, and whether such changes can be reversed. Blocks of feta cheese made overnight at 20 and 31oC yielded cheese of pH 4.92 and pH 4.83 (P<0.05) with 50.8 and 48.9 g/100g moisture (P<0.05), respectively. These cheeses were then cut into 100 g pieces and placed in plastic bags containing 100 g of whey brine solutions of 6.5, 8.0 and 9.5% salt, and then stored at 3, 6, 10, and 22oC for 10 d. After brining, cheese and whey were re-weighed, whey volume measured and cheese salt, moisture and pH determined. A second set of cheeses were similarly placed in brine (n=9) and stored for 10 d at 3oC, followed by 10 d at 22oC, followed by 10 d at 3oC, or the complimentary treatments starting at 22oC. Cheese weight and whey volume (n=3) were measured at 10, 20 and 30 days of brining. Cheese structure was examined using confocal microscopy. Brining temperature had the greatest influence on cheese composition (except for salt content), cheese weight and cheese volume. Salt-in-moisture content of the cheeses approached expected levels based on brine concentration and ratio of brine to cheese, i.e., 4.6, 5.7 and 6.7%. Brining at 3oC increased (P<0.05) cheese moisture, especially for cheese with initial pH of 4.92, producing cheese with moisture up to 58 g/100g. Cheese weight increased after brining at 3, 6 or 10oC. Cold storage also prevented further fermentation and the pH remained constant, while at 22oC the pH dropped as low as pH 4.1. At 3oC the cheese matrix expanded (20 to 30%) while at 22oC there was a contraction and a 13 to 18 g/100g loss in weight (P<0.05). Expansion of the protein matrix at 3oC was reversed by changing to 22oC. However, contraction of the protein matrix, was not reversed by changing to 3oC and the cheese volume remained less than what it was initially.
Publications
- McMahon, D. J. and B. S. Oommen 2008. Supramolecular structure of the casein micelle. Journal Dairy Science 91:1709-1721.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Analyzed data from an experiment on weight and volume changes of cheese after being stored in salt solutions of different salt concentrations (2, 10, 18 and 26% ), different calcium concentrations (0, 0.1, 0.2 and 0.4%) and at different temperatures (4, 12 and 20 C). Chemical composition and selected microstructural analysis was performed. Organized for a PhD student from Italy to come to Utah State University as a short term scholar, and provided mentoring to that student during the visit.
PARTICIPANTS: This experiment was performed in partnership with CoRFiLaC cheese research institute in Ragusa, Italy. A PhD student from Catania University, Italy is participating in the project.
TARGET AUDIENCES: US cheese manufacturing industry is the target audience, especially those involved in product development and technical services. This group will be reached through presentations at dairy science meetings, presentations sponsored by Dairy Management Inc., and annual meeting of Western Dairy Center. The information will be used in development of new cheese products for presentation to the dairy industry through Dairy Management Inc.
Impacts
The protein matrix of cheese responds to both temperature and chemical environment. In general, as temperature increases there is a tendency for the protein matrix to contract, and conversely expand when cooled. Similarly, at high salt concentrations a contraction occurs and at low salt concentrations, an expansion occurs. The cheese brining experiments help provide insight into what is happening to the protein matrix after its initial manufacture and how this can be manipulated so as to increase or decrease the level of protein-protein interactions in cheese. A cheese stored at 4 C will increase in volume by 30% in a 2% brine solution, increase by 8% in a 10% brine solution, but decrease in volume by 10% in an 18% brine solution, and decrease by 13% in a saturated (26%) brine solution (with all brines containing 0.1% Ca). Storage at 12 C produces similar results ( slightly less expansion and slightly more contraction) but if the cheese is stored at 20 C, then the
increased importance of hydrophobic interactions between proteins as temperature increases counters the effect of a low salt concentration. Thus, at 20 C, only a 4% expansion occurred in the cheese stored for 24 h in the 2% brine, and a 3% decrease in volume occurred for cheese stored in a 10% brine. If cheese is stored in a saturated brine at 20 C then a 24% decrease in volume of the cheese was observed. Calcium concentration has an even greater influence on the cheese protein matrix and a 10% salt solution containing 0.4% Ca will bring about a 17% decrease in cheese volume when stored at 20 C. If no Ca is added to a 10% salt solution, an expansion of the cheese will occur (25% volume increase compared to only 8% at 0.1% Ca. Typically, 0.1 to 0.2% Ca is added when brining cheese.
Publications
- No publications reported this period
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