Progress 10/01/04 to 09/30/09
Outputs
OUTPUTS: Six publications regarding the microbiological and chemical factors affecting calcium lactate crystal formation and prevention in Cheddar cheese have been published. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Academics and industry benefited from the findings we have presented in written, poster and oral presentations.
Publications
- No publications reported this period
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: A sixth publication regarding the microbiological and chemical factors affecting calcium lactate crystal formation and prevention in Cheddar cheese was published in 2008. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Academics and industry benefit from the findings we have presented in written, poster and oral presentations.
Publications
- Agarwal, S., J.R.Powers, B.G.Swanson, S.Chen, and S.Clark. 2008. Influence of Salt to Moisture Ratio on Starter Culture and Calcium Lactate Crystal Formation. Journal of Dairy Science. 91:1-14.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Microbiological and Chemical Factors Affecting Calcium Lactate Crystal Formation in Cheddar Cheese
PARTICIPANTS: Shantanu Agarwal, Shulin Chen, Joseph Powers, Barry Swanson
TARGET AUDIENCES: Commercial cheese plants
PROJECT MODIFICATIONS: none
Impacts
Occurrence of L(+)-lactate crystals in hard cheeses continues to be an expense to the cheese industry. Salt-tolerance of starter culture and salt to moisture ratio (S/M) in cheese dictate the final pH of cheese, which influences calcium lactate crystals (CLC) formation. This research investigated these interactions on the occurrence of CLC. A commercial starter was selected based on its sensitivity to salt (less than and greater than 4.0 S/M). Cheddar cheese was made using either whole milk (3.25% protein, 3.85% fat) or whole milk supplemented with cream and ultrafiltered milk (4.5% protein, 5.3% fat). Calculated amounts of salt were added at milling (pH 5.40 + or - 0.02) to obtain cheeses with less than 3.6 and more than 4.5 S/M. Total and soluble calcium, total lactic acid and pH were measured and development of CLC was monitored in cheeses. All cheeses were vacuum packaged and gas flushed with N2 and aged at 7.2C for 15 weeks. Concentration of total lactic acid in
high S/M cheeses ranged from 0.73 to 0.80 g/100 g of cheese while in low S/M cheeses ranged from 1.86 to 1.97 g/100 g at the end of 15 weeks of aging due to starter culture's salt sensitivity. Low and high S/M concentrated milk cheeses (LSCMC and HSCMC), exhibited 30 to 28% increased total calcium (1242 and 1239 mg/100g cheese, respectively), than low and high S/M whole milk cheeses (LSWMC and HSWMC; 954 and 967 mg/100g of cheese, respectively) throughout aging. Soluble calcium was 41 to 35% greater in low S/M cheeses (LSWMC and LSCMC; 496 and 524 mg/100g cheese, respectively) compared to high S/M cheeses (HSWMC and HSCMC; 351 mg/100g and 387 mg/100g cheese, respectively). Due to the lower pH of the low S/M cheeses, CLC were observed in low S/M cheeses. However, the greatest intensity of CLC was observed in gas flushed cheeses made with milk containing increased protein concentration due to the increased content of calcium available for CLC formation. These results show that
occurrence of CLC is dependent on cheese milk concentration and pH of cheese, which can be influenced by S/M and cheese microflora.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
Gas flushed packaging is commonly used for cheese shreds and cubes to prevent aggregation and loss of individual identity. A defect sometimes observed on cubed cheese surfaces is calcium lactate crystals (CLC). The white haze is unappealing to consumers, who may confuse the crystals with mold. Annually, CLC costs cheese manufacturers millions of dollars in lost revenue. In one study, a sanitized cheese plant was swabbed for the presence of non-starter lactic acid bacteria (NSLAB) biofilms. Swabs were analyzed to determine the sources and microorganisms responsible for contamination. In pilot plant experiments, cheese vats filled with Standard cheese milk (SCM, lactose: protein = 1.47) and Ultrafiltered cheese milk (UFCM, lactose: protein = 1.23) were inoculated with Lactococcus lactis ssp. cremoris starter culture (8 log cfu/ml) and with or without isolates, Lactobacillus curvatus or Pediococci acidilactici, as adjunct cultures (2 log cfu/ml). Cheddar cheeses were
aged at 7.2oC or 10oC for 6 months. Raw milk silo, ultrafiltration (UF) unit, cheddaring belt and cheese tower had the most NSLAB biofilms, (2-4 log cfu/100cm2). The population of Lb. curvatus reached 8 log cfu/gm while Ped. acidilactici reached 7 log cfu/gm of experimental Cheddar cheese in just 14 days. Higher NSLAB counts were observed in the first 14 days of aging in cheese stored at 10oC compared to 7.2oC. However, microbial counts decreased more quickly in Cheddar cheeses aged at 10oC compared to 7.2oC after 1 month. In cheeses without specific adjunct cultures (Lb. curvatus or Ped. acidilactici), calcium lactate crystals (CLC) were not observed within 6 months but crystals were observed after only 2 months in cheeses containing Lb. curvatus. Another study was designed to determine whether gas flushing of Cheddar cheese contributes to the occurrence of CLC. Cheddar cheese was manufactured using standard methods, with addition of starter culture, annatto and chymosin. Two
different cheese milk compositions were used: Standard (lactose:protein=1.47, protein:fat=0.90, lactose=4.8%) and Ultrafiltered (UF) (lactose:protein=1.23, protein:fat=0.84, lactose=4.8%), with or without adjunct Lb.curvatus. Curds were milled at 0.45% titratable acidity and pressed for 16h. After aging at 7.2oC for 6 mo, cheeses were cubed (1cm*1cm*4cm) and either vacuum packaged or gas flushed with carbon dioxide, nitrogen, or a 50:50 mixture of carbon dioxide and nitrogen, then aged three additional mo. Heavy crystals were observed on surfaces of all cubed cheeses that were gas flushed, but not on cheeses that were vacuum packaged. Cheeses without Lb. curvatus exhibited L(+)-CLC on surfaces, while cheeses with Lb. curvatus exhibited racemic mixtures of L(+)/D(-)-CLC throughout the cheese matrix.
Impacts
Our research shows that low levels of contamination with certain NSLAB can result in CLC, regardless of lactose:protein ratio. Further, gas flushing, regardless of gas composition, milk composition and presence of nonstarter lactic acid bacteria (NSLAB), can contribute to the development of CLC on cheese surfaces. These findings stress the importance of packaging to cheese quality.
Publications
- Agarwal, S., K.Sharma, B.G.Swanson, G.U.Yuksel, and S.Clark. 2006. Non-starter lactic acid bacteria biofilms and calcium lactate crystals in Cheddar cheese. Journal of Dairy Science. 89:1452-1466.
- Agarwal, S., J.R.Powers, B.G.Swanson, S.Chen, and S.Clark. 2006. Cheese pH, protein concentration and formation of calcium lactate crystals. Journal of Dairy Science. 89:1452-1466.
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Progress 01/01/05 to 12/31/05
Outputs
To study relationships among total and soluble calcium in cheese, pH, lactic acid and calcium lactate crystal (CLC) formation, cheeses were made from cheese milk adjusted to different protein concentrations using either NFDM or Ultrafiltered (UF) nonfat milk. Total and soluble calcium (Ca) concentrations were measured in nonfat milk (total solids 8.7%), and concentrated nonfat milk (CSM) (total solids 13.5%) using atomic absorption spectroscopy. Concentration of milk by addition of NFDM increased the total calcium in CSM (210 mg/100g of milk) by 52%, compared to total Ca in nonfat milk (138 mg/100g of milk). The colloidal Ca in CSM (147 mg/100g of milk) increased by 83%, compared to colloidal Ca in nonfat milk (80 mg/100g of milk). At pH 5.4, soluble Ca in CSM (179 mg/100g of milk) was 68% more when compared to soluble Ca in nonfat milk (106 mg/100g of milk). These findings demonstrate that excessive Ca, available in soluble form, can react with lactic acid and form
CLC. Reducing the pH of the cheese milk from a pH of 5.4 to pH 5.0 increased the amount of soluble Ca in both nonfat milk (17.83 mg/100g of milk) and CSM (34.73 mg/100g of milk). Increased soluble Ca concentration in CSM can increase occurrence of CLC in cheeses made using concentrated cheese milk. The problem of CLC can be seriously increased when the pH of the cheese is reduced after pressing, which can be due to the presence of active starter lactic acid bacteria or growth of non starter lactic acid bacteria. In another ongoing study, cheeses were made from nonfat milk (SMC) (3.14% protein, 8.7% total solids), nonfat milk concentrated with NFDM (CSM1)(6.60% protein, 15.5% total solids) and UF nonfat milk (CSM2) (6.65% protein, 12.8% total solids). Total and soluble Ca in cheeses were studied at pH 5.4, 5.3, 5.2, 5.1, 5.0, 4.9 and 4.8. In cheeses made from CSM1, total Ca (1240 mg/100g cheese) was 32% higher than SMC (940 mg/100 gm of cheese). Colloidal Ca in CSM1 (880 mg/100g of
cheese) was 38% more than SMC (639 mg/100g of cheese). In SMC as the pH of the cheeses decreased from 5.4 to 5.0 the amount of soluble Ca increased by 71% from 301 mg/100g of cheese to 516 mg/ 100g of cheese. In cheeses made from CSM1, the amount of soluble Ca increased by 68% from 360 mg/100g of cheese to 606 mg/100g of cheese. These results show that not only does the amount of soluble Ca increase in cheese with increase in concentration of milk, but also with decrease in pH of the cheese during storage. Heavy CLC were observed in all cheeses stored overnight, which had a pH of 5.0 or less, showing the importance of pH of cheese during storage. These results help us to understand why we saw increased intensity of CLC in cheeses made from concentrated milk (Agarwal et al., 2006). More work is currently being pursued to study the interaction of calcium with phosphate and citrate at different pH. Further studies plan to find the relationships between cheese composition (moisture and
fat) and formation of CLC and serum migration dynamics in cheeses during storage of cheese.
Impacts
Results will help us develop a mathematical model that should be able to predict the occurrence of calcium lactate crystals (CLC) in cheese, helping cheese manufactures to predict CLC and plan their packaging methods and sales accordingly, to minimize the problem of CLC.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
Cheddar cheeses, made with and without racemase-positive non-starter lactic acid bacteria (NSLAB), were cubed, then vacuum packaged and flushed with gas to determine the effect of various gases upon calcium lactate crystal (CLC) formation. Duplicate batches of cheeses were made (Standard cheese with starter culture, Standard cheese with starter culture and L. curvatus, Ultrafiltrated milk (UF) cheese with starter culture, and UF cheese with starter culture and L. curvatus). Replicates of cheese were made from 90.8 kg of milk, using standard procedures. Finished cheeses were then aged at 7.2C for six months. After aging, cheeses were cut and repackaged as would have been done in a cut and wrap facility. Sets of 10 pieces of cut cheese were either vacuum packaged or gas flushed with CO2, N2 or a mixture of 50%CO2/50%N2. At the end of 12 weeks of storage, a 7-8% reduction in volume was observed in cheeses gas flushed with CO2. Carbon dioxide is very soluble in water,
forming carbonic acid. Carbon dioxide is readily absorbed by the moisture present on cheese surface, which probably explains the 7-8% loss in volume in packages flushed with CO2. However, no significant differences were observed in cheese pH among cheeses flushed with different gases. A possible explanation for the non-significant difference in pH of cheeses is the high buffering capacity of cheese in pH range of 4.8 to 5.2. CLC were observed in both control and cheeses with L. curvatus in all cheese packages that were gas flushed. L(+)-lactate crystals were observed in all control cubed cheeses that were gas flushed, however no crystals were observed in control cheeses that were vacuum packaged. D(-) lactate crystals were observed in all cheeses with L. curvatus. Additionally, higher intensity of D(-) crystals were observed in cheeses that were gas flushed compared to cheeses that were vacuum packaged. Finally, higher crystal intensity was observed in cheeses made from UF milk
compared to cheeses made from standard milk. Possible reasons for increased occurrence and higher intensity of crystals in gas-flushed compared to vacuum packaged cheeses follow. Cubing of cheese increases surface area and increased surface area leads to increased loss of moisture to the surrounding environment. Loss of moisture may facilitate concentration of salts on the surface of the cheese, leading to initiation of lactate crystallization. Loss of moisture from surface also triggers movement of serum to the surface, enabling binding of calcium and lactate ions. Increased concentration of calcium and lactate leads to increased occurrence of CLC. Additional research to confirm the reasons for both D(-) and L(+)-lactate crystal formation in Cheddar cheese is warranted.
Impacts
Quality and appearance defects in Cheddar cheeses discourage repeat purchases by consumers. White crystals on the surface of Cheddar cheese detrimentally affect sales and have been documented since the 1930s. The problem still remains a challenge and expense to cheese manufacturers, with significant amounts of Cheddar cheese still manufactured in US with the problem of calcium lactate crystals (CLC). Even large dairy industries like Land-O-Lakes and cheese plants that manufacture cheese for Land-O-Lakes loose 5 to 7 million dollars each year due to CLC. According to Johnson almost all cheese plants have the problem of CLC in mild and medium Cheddar cheese during some part of the year. Researchers at the Center of Dairy Research in Wisconsin, Madison continue to work on this problem while other large dairy companies continue to do their own research in trying ways to prevent CLC in Cheddar cheese. Understanding and control of CLC is still a hot topic because Dairy
Management Inc. invited grant proposals for 2005. Understanding the complex relationships among cheese-milk composition, bacteria, processing procedures, and aging conditions may enable processors to minimize the occurrence of calcium lactate crystals (CLC) in the future. These understandings will be built upon fundamental research specially designed to isolate and independently address each of the multitude of issues that affect CLC formation. The financial losses that CLC cost the cheese industry warrant research into intervention strategies.
Publications
- Soeryapranata,E., Powers,J.R., Weller,K.M., Hill,H.H. and Siems, W.F. 2004. Differentiation of intracellular peptidases of starter and adjunct cultures using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Lebensmittel-Wissenschaft und Technologie 37:17-22.
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Progress 01/01/03 to 12/31/03
Outputs
Non-starter microorganisms, Pediococcus acidilactici, Staphylococcus saprophyticus and Lactobacillus curvatus, were isolated from various locations within a sanitized commercial cheesemaking production line and finished cheeses. The three isolates were capable of racemizing L(+)-lactic acid to D(-)-lactic acid and were used as adjunct cultures in cheesemaking trials. Ultrafiltered milk (lactose:protein ratio 1.23) and standard milk (lactose:protein ratio 1.47) were used to make experimental cheeses. Lactose concentration, 4.8% w/v, was maintained for both batches. Finished cheeses were aged at 7.2 degrees C and 10 degrees C. Concentrations of residual lactose, L(+)- and D(-)-lactic acid were determined and calcium lactate crystal (CLC) formation was monitored for 6 mo. Within the first 14 d of aging most of the residual lactose in cheeses was utilized by microorganisms and no significant differences were observed in the lactose concentrations between UF and standard
milk cheeses. No significant differences in L(+)-lactic acid concentrations were observed after 28 d between UF and standard milk cheeses. Cheeses stored at 10 degrees C exhibited lower mean lactose and higher D(-)-lactic acid concentrations than cheeses stored at 7.2 degrees C (p<0.05), but with no significant differences in L(+)-lactic acid concentrations. Within 56 d, 35% of the total lactic acid in cheeses with added L. curvatus and stored at 10 degrees C was in the D(-)-form and CLC were observed. At the end of 6 mo, 24% of total lactic acid in cheeses with added P. acidilactici and S. saprophyticus was in the D(-)-form with no CLC observed. Irrespective of lactose:protein ratio, contamination of cheese milk with racemizing NSLAB L. curvatus, may lead to CLC, particularly at elevated storage temperatures. Elimination of racemizing NSLAB and control of storage temperature are important measures to inhibit CLC.
Impacts
Plant sanitation to inhibit non-starter microorganism proliferation and prevention of temperature fluctuations during cheese storage are critical components that must be controlled to minimize calcium lactate crystal formation in cheese.
Publications
- Chou, Y.-E., C.G. Edwards, L.O.Luedecke, M. P. Bates and S. Clark. 2003. Nonstarter lactic acid bacteria and aging temperature affect calcium lactate crystallization in Cheddar cheese. J. Dairy Sci. 86: 2516-2524.
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Progress 01/01/02 to 12/31/02
Outputs
Non-starter microorganisms (NSLAB) were isolated from various locations, raw ingredients, and finished cheeses within a commercial cheese plant in WA. Post-sanitation, high levels of contamination were found in raw milk silos, ultrafiltration unit, Cheddar Master, milling and salting equipment, cheese transport lines from milling and salting machine to the cheese tower, and Cheddar cheese towers. Isolates were identified and tested for capability to racemize D(less then)/L(greater then)-lactic acid. Pediococcus acicilactici, Staphyloccus saprophyticus and Lactobacillus curvatus were selected as adjuncts for cheesemaking trials based on their high racemization activity. Cheese-milk was standardized before pasteurization to protein:fat ratio of 0.84 for ultrafiltrated (UF) milk and 0.90 for standard milk. The lactose:protein ratio was 1.23 for UF milk and 1.47 for standard milk, with lactose concentration of 4.8 % wt/vol for both. Isolated NSLAB were added to milk to
achieve initial populations of 500-700 cfu/ml to mimic the low initial NSLAB typically found in pasteurized cheese milk. At 0.45% TA, the loaves were milled and curds salted (0.3% wt/wt of milk). Finished cheeses were aged at 45F and 50F, in light and in darkness. Total plate counts in experimental cheeses increased slightly from 7.8 log to 8.1 log within 7 days of manufacture. After the first week, the total microbial numbers decreased, indicating lysis of the starter lactic acid bacteria (SLAB) due to depletion of lactose in cheese. Total NSLAB increased from 102cfu/gm to 106cfu/gm in the first month. Higher NSLAB counts were found in cheeses aged at 50F compared to cheeses stored at 45F, but lighting had no effect. The P.acidilactici population increased from 102 to 106cfu/gm in one month, and remained around 106 cfu/gm through 6 months of aging. The population of L.curvatus increased from 102 to 107cfu/gm in 14 days, while the population of SLAB decreased from 108 to 105cfu/gm.
Cheeses inoculated with L.curvatus exhibited white crystals, once the packets were opened, after 2 months of ripening.
Impacts
Utmost care must be taken to completely clean and sanitize equipment prior to cheesemaking. Biofilms, if not removed, may inoculate cheese milk or cheese with non-starter microorganisms that may be capable of contributing to calcium lactate crystal formation. Certain NSLAB contribute to the formation of calcium lactate crystals, while others do not. Specifically, NSLAB that convert L(greater than)-lactic acid to D(less than)-lactic acid at high rates, promote crystal formation. In the present study, L. curvatus contributed to crystals more readily than P. acidilactici and S. saprophyticus even though the latter are capable of converting L(greater than)-lactic acid to D(less than)-lactic acid. Accumulation of D(less than)-lactate is exacerbated at elevated storage temperatures, but is not influenced by lighting conditions.
Publications
- No publications reported this period
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Progress 01/01/01 to 12/31/01
Outputs
Although the occurrence of unappetizing calcium lactate crystals (CLC) in Cheddar cheese is a challenge and expense to manufacturers, little is known regarding their origin. It was hypothesized that nonstarter lactic acid bacteria (NSLAB) affect CLC by producing D(-)-lactate. This study was designed to understand the growth of NSLAB and aging temperature on CLC. Chesses were made from milk inoculated with Lactococcus lactis starters culture, with or without Lactobacillus curvatus of L. helveticus WSU19 adjunct cultures. Cheeses were aged at 4 degrees C or 13 degrees C for 28 days prior to changing storage temperature. Half of the cheeses from 4 degrees C and 13 degrees C were transferred to 13 degrees C and 4 degrees C, respectively, for the remainder of aging. The form of lactate in cheeses with L. helveticus WSU19 was predominantly L(+)-lactate (>95%wt/wt) and crystals were not observed after 70 days aging. While initial lactate in cheeses containing L. curvatus was
only L(+)-latate, the concentration of D(-)-lactate increased as cheeses were aged. After 28 days of aging, a racemic mixture of D/L-lactate was measured in cheeses containing L. curvatus while, at the same time, CLC was observed. Earliest and greatest extent of CLC occurred on cheeses aged at 13 degrees C for 28 days and then transferred to 4 degrees C. These results showed that formation of D(-)-lactate and aging temperature affect CLC in maturing Cheddar cheese and a minimum of 50% of the total lactate in the D(-) isomer was necessary before CLC could be observed.
Impacts
Calcium lactate crystals (CLC) in Cheddar cheese cost the dairy industry millions of dollars each year. Understanding the source of the problem and identifying ways to eliminate CLC formation will benefit the dairy industry as a whole.
Publications
- No publications reported this period
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Progress 01/01/00 to 12/31/00
Outputs
Three duplicate batches of Cheddar cheese, were manufactured with initial lactose contents of cheese-milk (3.8%, 4.7% and 5.2%). Lactose has been implicated as a source of calcium lactate crystals (CLC). Cheeses were sealed in high barrier polyethylene plastic and stored at 45 degrees F. Batches were split for temperature fluctuation (70 degrees F, 24 hours) and contamination (with cheese containing CLC) treatments to mimic commercial cutting conditions. Lactose and L(+)- and D(-)-lactate were monitored weekly for the first month, then monthly for 6 months. Initial milk lactose levels and temperature fluctuations did not significantly influence residual lactose, L(+)-, or D(-)-lactate formation. However, temperature fluctuation along with contamination significantly influenced L(+)- and D(-)-lactate. The findings suggest that microbial flora play a more significant role in CLC formation than cheese-milk lactose concentration. Retail handling conditions may influence
CLC formation. Non-starter lactic acid bacteria (NSLAB) in Cheddar cheeses containing CLC were isolated. NSLAB isolates capable of forming a significant amount of D(-)-lactate were selected for cheese making. Cheddar cheese was made from milk standardized with 5.2% lactose and 0.87 protein:fat. One starter culture was combined with each of three different adjunct cultures, and a fourth cheese, without an adjunct, served as a control. Cheeses were sealed in high barrier polyethylene and split in half for ripening temperature treatments and again for temperature fluctuation treatments. Crystals began to appear on cheeses made with adjunct NSLAB isolates after only 8 weeks. Crystals were identified as calcium lactate hydrate. Microflora populations and D(-)-lactate increased significantly in cheeses with NSLAB adjuncts, but not in cheeses with WSU19 adjunct or control cheeses. CLC appeared when more than 50% of the total lactate was in the D(-)-lactate form. Elevated temperature promoted
NSLAB growth, lactose utilization, and D-lactate production in cheese. NSLAB and aging temperature play a significant role in calcium lactate crystallization, so elimination of NSLAB and control of storage temperature are recommended to prevent unappealing CLC.
Impacts
The results of this research will have application to improving Cheddar cheese quality through ripening and retail handling, which will economically benefit the dairy industry through increased sales and less waste. This research improves our basic understanding of the biochemical and microbiological processes involved in the aging of Cheddar cheese and their effect on formation of calcium lactate crystals. This research will lead to a greater comprehension of the defect and enable recommendations to be made regarding manufacturing and handling practices necessary to minimize CLC occurrence and maximize cheese quality.
Publications
- Chou, Y.E., S. Clark, L. Luedecke, C. Edwards, and M. Bates. 2000. Nonstarter lactic acid bacteria and aging temperature affect lactic acid production and calcium lactate crystallization in Cheddar cheese. Institute of Food Technologists Annual Meeting. Abstract.
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Progress 01/01/99 to 12/31/99
Outputs
The peptidolytic activities cheese cultures for their effect on bitterness in Cheddar cheese was evaluated. Mixed strain primary starters, Lactococcus lactis ssp. lactis and Lc. lactis ssp. cremoris, #56, #98 and #105, with varying tendencies to produce bitter cheeses, and two adjunct cultures, Lactobacillus helveticus WSU19 and W900R, varying in aminopeptidase (AP) activity, were studied. Peptidolytic activity was measured in cell free extracts (CFE) and in extracts from cheeses made with or without adjunct cultures. X-Prolyl Dipeptidyl AP and general AP activities from CFE of WSU19 were markedly greater than W900R and starter cultures. The lactococci population was greater during ripening in cheeses made with starter #105 than #56 or #98. Rapid reduction in cell number during ripening in WSU19 cheeses was accompanied by accumulation of large amounts of free amino groups and free amino acids. Cheeses made with WSU19 had greater AP activity compared to the other
cheeses. There was no significant difference (p<0.05) between AP activity of W900R and control cheeses. Sensory analysis found that cheeses made with WSU19 were less bitter compared to W900R and control cheeses at 6 and 9 months. This study confirmed that addition of an adjunct Lb. helveticus culture containing a high level of AP that is rapidly released, reduces bitterness in Cheddar cheese. Calcium lactate crystals (CLC) in WSU Cheddar cheeses and a commercial Cheddar cheese were identified by X-Ray Diffraction and Nuclear Magnetic Resonance. The presence of L-tyrosine on the surface and interior of both WSU Cheddar and Cougar Gold cheeses was confirmed. Crystals in the commercial Cheddar cheese were identified as calcium lactate and contained a mixture of D(-)- and L(+)-lactic acid. Cheddar cheeses were made from standardized milk containing three levels of lactose under controlled conditions to investigate the influence of lactose concentration upon CLC formation. Changes in
cheese lactose, L(+)- and D(-)-lactic acid over time and after temperature abuse are under investigation. Several non-starter lactic acid bacteria (NSLAB) were isolated from WSU Cheddar cheeses and the commercial Cheddar cheese. Gram stains were positive, catalase tests were negative, and oxidase tests were negative for all isolates. From the observations of growth at different NaCl% (2%, 4%, and 6%), initial broth pH (5, 7 and 9), and incubation temperatures 5, 23, and 40 C), possible microorganisms include: Lactococcus lactis, Streptococcus raffinolactis, Lb. brevis, Lb. casei, Lb. plantarum, Lb. fermentum, Lb. lactis, Lb. bulgaricus, and Lb. helveticus. To confirm species, the strains' abilities to utilize different carbohydrate sources will be determined. The isolated microorganisms will also be tested for their ability to produce D(-)- and L(+)-lactic acid. D(-)-lactic acid is presumed to contribute to the crystal formation on cheese because of its lower solubility than -lactic
acid. Microorganisms which can produce significant amount of D(-)-lactic acid will be used as adjunct cultures in cheesemaking to observe crystal formation.
Impacts
(N/A)
Publications
- No publications reported this period
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Progress 01/01/98 to 12/31/98
Outputs
Two research grant proposals titled 'Reducing the Development of Calcium Lactate Crystals in Cheddar Cheese' were submitted in the fall, 1998. One proposal, submitted to Dairy Management Incorporated (requested $87,489 for 3 years) was not granted. Another, submitted to the Washington State Dairy Products Commission (requested $29,228 for 1 year), was granted. An additional research grant proposal titled, 'Factors Affecting the Flavor and Quality of Cheddar Cheese' was submitted to the Washington State Dairy Products Commission (requested $10,654 for 1 year) and was granted. Two Master's degree candidates started working on this project in August, 1998. Each student spent the fall semester conducting literature reviews on 'Reducing the Development of Calcium Lactate Crystals in Cheddar Cheese.' The spring semester will be spent identifying calcium lactate crystals (CLC) in 2 WSU Cheddars and 1 commercial Cheddar cheese. Additional work will be done to isolate,
identify and classify the starter cultures and non-starter lactic acid bacteria (NSLAB) in 2 WSU Cheddar cheeses and 1 commercial Cheddar cheese.
Impacts
(N/A)
Publications
- No publications reported this period
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