Location: Dairy and Functional Foods Research
2019 Annual Report
Objectives
1: Integrate non-thermal milk processing technologies with replacing sodium with potassium during cheesemaking to determine the effects on quality traits, shelf-life, and bioactives of fresh high moisture cheeses, Queso Fresco and dry cottage cheese.
1.a: Characterize the effects of NTP, with and without heat, on the chemical, microbiological, and physical properties of milk.
1.b: Optimize cheesemaking protocols using NTP-modified milk.
1.c: Characterize the effects of NTP of cheesemilk and altering the Na-K levels on the chemical, microbiological, sensorial, functional, textural, rheological, and structural properties of aging low-sodium cheese.
2: Enable non-thermal milk processing technologies that alter protein-fat interactions on milk enriched with long-chained polyunsaturated fatty acids (PUFA) during cheesemaking to assess their impact on quality traits, shelf-life, and bioactives of fresh high-moisture cheeses, Queso Fresco and dry cottage cheese.
2.a: Characterize the chemical and physical properties of PUFA-enhanced fractions.
2.b: Characterize the effects of NTP, with and without heat, on the chemical, microbiological, and physical properties of PUFA-enhanced milk.
2.c: Characterize the effects of NTP of PUFA-enhanced cheesemilk on the chemical, microbiological, sensorial, functional, textural, rheological, and structural properties of aging cheese.
3: Integrate the impact of non-thermal milk processing on cheeses made in Objectives 1 and 2,with bioactive peptide formation during aging and in vitro digestion.
3.a: Characterize the effects of NTP on proteins and peptides in milk.
3.b: Characterize the effects of NTP on the formation of bioactive peptides in aging cheese and during in vitro digestion.
Approach
This study focuses on the incorporation of non-thermal processes (NTP) that use high pressure homogenization (microfluidization) or ultra-high frequencies (ultrasonication) in the manufacture of high-moisture cheeses with unique textures, such as Queso Fresco (QF) and dry curd cottage cheese (CC). A combination of treatments, including NTP with and without heat and homogenization will be used to modify cheesemilk for the manufacture of low sodium cheese in which different NaCl-KCl treatments will be applied to the curds before molding (QF) or packaging (CC). Modified milk fat fractions will be created and incorporated into the cheesemilk using the combination of treatments above and used to make QF and CC. All cheeses will be evaluated for compositional, physical, microbiological, functional, rheological, microstructural, and sensorial properties and profiles generated for lipid, proteins, and volatile compounds at intervals throughout aging. The effects of NTP on the release of bioactive peptides, such as casein phosphopeptides and peptides with antihypertensive or antimicrobial activities, from the proteins within the cheese matrix will be evaluated.
Progress Report
Ultrasonication (US) of cheese milk. Cheesemilk was standardized to 3.0% fat and vat pasteurized at 63°C for 30 min. Small batches (5 gal vats) of Queso Fresco were made using 1) US-treated milk, processed at a flow rate of 0.12-L/min at 54°C, with 4 passes through the US system, and 2) control milk, homogenized in a 2-stage unit at pressures of 10/5 MPa. The US treatment provided some reduction in the fat droplet sizes without loss of curd firmness. Limited evaluation of the quality traits of the two cheeses showed similar composition (16% fat, 61% moisture, 15% protein, and 3.3 % lactose) and texture values (hardness, 1.1 kg; springiness, 0.5 mm; cohesiveness, 0.19; and chewiness 114). Preliminary results show that milk could be sonicated at mid-range conditions in a timely manner for cheese production and result in a high moisture cheese similar to the control.
Comparison of the two nonthermal processing (NTP) treatments showed limitations to both approaches. Microfluidization, the nonthermal process used previosuly, successfully reduced fat droplets to submicron sizes in one pass but was not able to process milk in quantities required for cheesemaking. Pilot plant ultrasonication could process larger quantities of milk but longer exposure times are needed to obtain uniform submicron sized fat droplets.
Polyunsaturated fatty acids (PUFA)-enhanced milk. The contingency plan to use plant-based oils was initiated when dairy-based PUFA-enhanced fractions could not be produced in quantities required for cheesemaking. Three common food grade oils were tested: perilla and flax seed oils containing the highest levels of omega-3 FA (C18:3), 60 and 57%, respectively, and about 14% of omega-6 (C18:2); while canola oil contained 8% omega-3 and 19% omega-6 (C18:2). Both perilla and canola oil made stable emulsions of the oil (0.5%) and milk (2.5% fat) when made using 2-stage microfluidization, and ultrasonication, but perilla oil warrants future consideration because of the higher C18:3 content. Flax seed oil emulsions were not stable.
Accomplishments
