Micellar Casein Concentrate As A Novel Dairy Protein Ingredient: Shelf-Life Stability And Its Application In The Production Of Low Fat Cheddar Cheese
Caseins are regarded as one of the principal functional food proteins which provide foaming, emulsifying, and water binding properties in food systems. Most of commercial caseins are produced by destabilizing casein micelles by rennet coagulation or acid precipitation, hence the native casein micelles are disrupted. With the advancement of microfiltration technology, it is possible to separate casein by microfiltration (MF) of skim milk while maintaining its micellar structure. The MF retentate of skim milk is called micellar casein concentrate (MCC). Fresh liquid MCC can be further concentrated by ultrafiltration (UF) to remove excess water, and at the same time remove low molecular weight (MW) compounds which can pass through the UF membrane. The liquid MCC can also be spray dried to produce powder. The MCC is a milk protein ingredient with properties that are different from other available protein ingredients, thus it might serve particular functions that other protein ingredients can't deliver. MCC could be used for high-protein, low-lactose drinks, cheesemaking, including production of low-fat Cheddar cheese. Our 1st objective was to develop a process to produce a high concentration liquid MCC (18% protein) with a long refrigerated shelf-life. To achieve a long refrigerated shelf-life, the processing of MCC18 was designed to maximize the removal of low MW compounds, e.g. lactose, nonprotein nitrogen (NPN) which can be easily metabolized by microbes, while minimizing the microbial count in the final product. The production of MCC18 was replicated 3 times. Skim milk was ultrafiltered (UF) which removed more than a half of lactose and NPN. The UF skim milk retentate was microfiltered (MF) in 3 stages to remove approximately 95% of the serum protein and further remove lactose and NPN. The final MF retentate was concentrated to 18% protein by UF, then batch pasteurized. The MCC18 was collected immediately in sterile plastic vials and stored at 4°C. The MCC18 contained 21.75% total solids, 18.27% true protein, 0.31% nonprotein nitrogen and 0.13% lactose. The mean aerobic bacterial and spore counts of MCC18 at day 0 were 2.1 log cfu/mL and 2.3 log cfu/mL, respectively. The MCC18 produced in this study maintained a bacterial count < 20,000 cfu/mL for 16 wk when stored at refrigeration temperature of 4°C. The conversion of skim milk to MCC and its coproducts (serum protein concentrate and lactose concentrate) could be used as an alternative to balance milk production seasonality. Our 2nd objective was to produce low-fat Cheddar cheese (LFCC) by combining reducedfat Cheddar cheese (RFCC) made by a fat removal process with MCC to try to achieve texture and flavor characteristics of full-fat Cheddar cheese (FFCC). The production of LFCC was replicated 3 times with a different batch of commercial FFCC, from which RFCC was produced, as an ingredient for LFCC-making. The LFCC was formulated to achieve 6% fat, 28% protein, 1.2% salt by combination of RFCC, MCC powder, water, salt, lactic acid and rennet. The 6% fat target was used to comply with the FDA standard for a low-fat label claim. The pH of the LFCC mixture was adjusted to 5.3 by lactic acid. Rennet was added, followed by pressing and packaging. Chemical and sensory data were analyzed by ANOVA using the Proc GLM of SAS to determine if there were differences on chemical compositions and sensory among different cheeses. Descriptive sensory scores were used to construct a PCA biplot to visualize flavor profile differences among cheeses. The LFCC had 83% less fat, 32% less sodium, higher protein and moisture than FFCC. When the cheese texture was evaluated in the context of a filled-gel model consisting matrix and filler (100% minus % matrix), the LFCC had lower filler volume than FFCC, yet the LFCC had a softer texture than FFCC. The LFCC contained some of the original FFCC cheese matrix that had been disrupted by the fat removal process, and this original FFCC matrix was embedded in a LFCC matrix formed by the action of rennet on casein from the continuous phase of hydrated MCC. Thus, the texture of the LFCC was desirable and was softer than the FFCC it was made from, whereas commercial RFCC (50% and 75% fat reduction) were firmer than the FFCC. The sulfur flavor in LFCC was closer to FFCC, than commercial RFCC. The LFCC had bitter and grape-tortilla off-flavors which came from the dried MCC ingredient. The commercial RFCC and experimental LFCC made in this study were missing the typical aged Cheddar character (catty, nutty, fruity, brothy, milkfat) found in FFCC.
Barbano, David Mark
McCormick, Charles Chipley W
Food Science and Technology
M.S., Food Science and Technology
Master of Science
dissertation or thesis