Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Doctor of Philosophy (PhD)

Department / School

Dairy and Food Science

First Advisor

Lloyd Metzger

Keywords

Acid curd, Functional characteristics, Imitation Mozzarella cheese, Micellar casein concentrate, Microfiltration membranes, Process cheese products

Abstract

Micellar casein concentrate (MCC) is a high protein ingredient that can be used in several applications, such as manufacture of acid curd and process cheese products (PCP). Acid curd is one of the casein (CN) products, which can be obtained by precipitating the CN at a pH of 4.6 (isoelectric point) using starter cultures or direct acids. Acid curd has low mineral and calcium content due to the solubility of colloidal calcium phosphate at the isoelectric point in the whey. Acid curd and MCC can be utilized in manufacture of clean label PCP formulations. PCP is a dairy food prepared by blending dairy ingredients (such as natural cheese, protein concentrates, butter, non-fat dry milk: NFDM, whey powder, and permeate) with nondairy ingredients (such as sodium chloride, water, emulsifying salts: ES, color, and flavors) and then heating the mixture with continuous agitation to produce a homogeneous product with an extended shelf-life. If acid curd is mixed with MCC, it may be possible to create a partially deaggregated casein network without the use of ES. The ratio of acid curd to MCC will have an impact on the level of deaggregation and the pH of the final PCP. We hypothesize that a ratio of 2 parts of protein from acid curd and 1 part of protein from MCC will create a partially deaggregated casein network similar to a typical process cheese that utilizes ES. The objectives of the first study were to determine the optimum protein content (3, 6, and 9% protein) in MCC to produce acid curd and to manufacture PCP using a combination of acid curd cheese and MCC that would provide the desired improvement in the emulsification capacity of caseins without the use of ES. To produce acid curd, MCC was acidified using lactic acid to get a pH of 4.6. In the experimental formulation, the acid curd was blended with MCC to have a 2:1 ratio of protein from acid curd relative to MCC. The PCP was manufactured by blending all ingredients in a kitchenaid to produce a homogeneous paste. A 25 g sample of the paste was cooked in a rapid visco analyzer (RVA) for 3 min at 95°C at 1000 rpm stirring speed during the first 2 min and 160 rpm for the last min. The cooked PCP was then transferred into molds and refrigerated until further analysis. This trial was repeated three times using different batches of acid curd. MCC with 9% protein resulted in acid curd with more adjusted yield. The end apparent viscosity (402.0-483.0 cP), hardness (354.0-384.0 g), melting temperature (48.0-51.0°C), and melting diameter (30.0-31.4 mm) of PCP made from different batches of acid curd showed were slightly different from the characteristics to typical process cheese produced with conventional ingredients and ES (576.6 cP end apparent viscosity, 119.0 g hardness, 59.8°C melting temperature, and 41.2 mm melting diameter) due to the differences in pH of final PCP (5.8 in ES PCP compared to 5.4 in no ES PCP). We concluded that acid curd can be produced from MCC with different protein content. Also, we found that PCP can be made with no ES when the formulation utilizes a 2:1 ratio of acid curd relative to MCC (on a protein basis). The objectives of the second study were to develop a process to produce acid curd from MCC using starter cultures and to manufacture imitation Mozzarella cheese (IMC) using a combination of acid curd and MCC that would provide the required emulsification ability to the caseins without the use of ES. The formulations were targeted to produce IMC with 18.0% protein, 49.0% moisture, 20.0% fat, and 1.5% salt. In the IMC formulation (FR-2:1), the acid curd was blended with MCC so that the formula contained a 2:1 ratio of protein from acid curd relative to MCC. Additional dairy and nondairy ingredients (milk permeate, vegetable oil, and salt) were also utilized in the formulations. Another IMC formulation was made using conventional ingredients and ES as a control. The IMC was prepared by mixing all ingredients in a kitchen aid to produce a homogeneous paste. A 20 g of the mixture was cooked in the RVA for 3 min at 95°C with a 1000 rpm stirring speed during the first 2 min and 160 rpm during the last min. The cooked IMC was then transferred into molds and refrigerated until further analysis. This trial was repeated 3 times using 3 different batches of acid curd. The end apparent viscosity of IMC was approximately 5711.0 cP for control and 7500.0 cP for FR-2:1, while the hardness was 301.0 g for control and 95.0 g for FR-2:1. The melt temperature was 55.5 and 50.0°C, melt diameter was 29.4 and 31.6 mm), melt area was 679.6 and 783.1 mm2, and stretchability was 12.5 and 12.3 cm of control and FR-2:1 IMC, respectively. The melt and stretch characteristics of IMC made from FR-2:1 were similar compared to control IMC. We conclude that IMC can be made with no ES when the formulation utilizes a 2:1 ratio of protein from acid curd relative to MCC. The objectives of the third study were to produce MCC using MF membranes and develop a process to produce a novel culture-based acid curd powder ingredient. Skim milk was pasteurized at 76°C for 16 sec and then microfiltered (MF) in 3 MF stages using graded permeability (GP) ceramic membranes. The skim milk was MF in a 3 stages process at 50°C with a 3× concentration factor (CF) and diafiltration (DF) to get MCC with >9% true protein (TP) and >13% total solids (TS). Part of the MCC was dried to produce MCC powder. The rest of the MCC was used to produce acid curd. The MCC was fortified with milk permeate as a source of lactose and inoculated with 0.5% starter cultures at 43°C to get the pH of 4.6 in 10-14 h. The curd was subsequently cut, drained, washed, and pressed. The curd was then milled and dried at 70-75°C outlet temperature for 3-4 h. The dried curd was then milled to produce acid curd powder. The skim milk, MF permeate, liquid MCC, modified MCC, acid curd, acid whey, MCC powder, and acid curd powder were compositionally analyzed. This trial was repeated 3 times using 3 different batches of skim milk. The skim milk had approximately 0.7, 3.4, 0.3, 0.9, 0.6, 9.0, and 4.4% ash, total protein (TPr), nonprotein nitrogen (NPN), noncasein nitrogen (NCN), serum protein (SP), TS, and lactose, respectively. The fortified MCC had 1.4% ash, 10.9% TPr, 0.2% NPN, 1.4% NCN, 1.2% SP, 17.4% TS, and 4.2% lactose. The curd prior drying showed approximately 1.0, 36.4, 0.7, 1.3, 0.6, 40.4, and 0.80% for ash, TPr, NPN, NCN, SP, TS, and lactose, respectively. The acid curd powder had approximately 2.0% ash, 86.9% TPr, 2.2% NPN, 2.3% NCN, 0.08% SP, 96.4% TS, and 1.4% lactose. The acid curd prior drying and acid curd powder were successfully produced from MCC. Future studies will be performed to utilize the acid curd and MCC powders at different ratios in process cheese products formulations and examine the functional properties of the cheese. The objective of the fourth study was to produce PCP without ES using different ratios of protein from novel cultured micellar casein concentrate ingredient (cMCC) and MCC powders. Three PCP treatments were formulated with 3 different ratios of cMCC: MCC including 2.0:1.0, 1.9:1.1, and 1.8:1.2 on a protein basis. The composition of PCP was targeted to 19.0% protein, 45.0% moisture, 30.0% fat, and 2.4% salt. This trial was repeated 3 times using different batches of cMCC and MCC powders. All PCP were evaluated for their final functional properties. No significant differences (P>0.05) were detected in the composition of PCP made with different ratios of cMCC and MCC except for the pH. It was expected to increase slightly with elevating the MCC amount in the PCP formulations. The end apparent viscosity was significantly higher (P<0.05) in 2.0:1.0 formulation (4305 cP) compared to 1.9:1.1 (2408 cP) and 1.8:1.2 (2499 cP). The hardness ranged from 407 to 512 g with no significant differences (P>0.05) within the formulations. However, the melting temperature showed significant differences (P<0.05) with 2.0:1.0 having the highest melting temperature (54.0°C), while 1.9:1.1 and 1.8:1.2 showed 43.0 and 42.0°C melting temperature, respectively. The melting diameter (38.8 to 43.9 mm) and melt area (1183.9 to 1538.6 mm2) did not have any differences in different PCP formulations. The PCP made with a 2.0:1.0 ratio of protein from cMCC and MCC showed better functional properties compared to other formulations.

Number of Pages

318

Publisher

South Dakota State University

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Rights Statement

In Copyright