Location: Dairy and Functional Foods Research
2017 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
Progress was made on all objectives, all of which fall under National Program
306 – Quality and Utilization of Agricultural Products, Component I, Food. Progress on this project focuses on Problem Statement B - New Bioactive Ingredients and Functional Foods and C - New and Improved Food Processing Technologies.
Research continues on using nonthermal processing techniques, which reduce bacterial counts and alter the protein-fat interactions of milk, in creating novel milk (Objective 1a) for the production of high-moisture cheeses with unique texture. We have completed phase 1 that explored a wide range of operating parameters for our first nonthermal processing technique, microfluidization, which homogenizes milk at pressures much higher than conventional homogenizers, and evaluated samples created at 3 inlet temperatures, 7 pressures, and up to 4 passes. Inlet temperatures below the melting point of milk fat were not feasible. As expected, particle size of fat droplets decreased significantly after the first pass through the microfluidizer, with only minor reductions after the second pass. Noticeable decreases in microbial counts were detected at pressures above 100 MPa. We identified 4 treatments to move forward to the next phase for full characterization.
For phase 2, we are currently examining the effects of high pressure homogenization (microfluidization) on raw or conventionally heat treated milk. Heat treatments include two common techniques employed by commercial milk production facilities, thermization and high temperature-short time (HTST) pasteurization. Thermization is a technique used by dairy manufacturers to extend the keeping quality of raw milk when it cannot immediately be used. HTST is the most common milk pasteurization technique currently employed by commercial milk production facilities. Protocols for conventional heat treatments have been established, and can be reliably performed on site. Raw and heat treated milks are then microfluidized at the four selected treatments (Objective 1a). Extensive characterization of the chemical, physical, microbiological, and coagulating properties of samples will identify which novel milk(s) have the potential to produce a high moisture cheese with unique texture.
Ultra-sonication, which uses high frequencies to alter the protein-fat interactions in milk, is the second nonthermal processing technique to be explored and the pilot scale unit has been commissioned and personnel trained in its operation. The experimental design to identify optimal operating parameters is in place and awaiting implementation. Findings from this study will be compared to the microfluidized milk and only the milk(s) with the highest potential will move forward to the cheese vat.
With the arrival of our new gas chromatography system and specialty column, the characterization of the polyunsaturated fatty acid (PUFA)-enhanced fractions that were made previously is moving forward, as well as determination of the effect of microfluidization on PUFA-enhanced milk (Objective 2b). The new system is capable of distinguishing between the various omega-3 fatty acids and isomers of the conjugated linoleic acids, which is crucial in determining if PUFA enhancement and processing treatments are effective. With the improved resolution and identification of PUFA, we re-evaluated the lipid profiles of raw and processed milks that were subjected to simulated digestion (from previous project) and found that the longer-chain "healthy" fatty acids were released faster from the triglyceride than the short- and medium-chain fatty acids, and therefore, were more readily available for uptake. Findings give more in-depth evaluation of lipolysis and a better understanding of the fate and potential bioavailability of healthy fats in milk.
Accomplishments
Review Publications
Van Hekken, D.L., Tunick, M.H., Renye Jr, J.A., Tomasula, P.M. 2017. Characterization of starter-free Queso Fresco made with sodium-potassium salt blends over 12 weeks of 4 degrees C storage. Journal of Dairy Science. doi: 10.3168/jds.2016-12081.
Paul, M., Phillips, J.G., Renye Jr, J.A. 2016. Short communication: Measuring the angiotensin-converting enzyme inhibitory activity of an 8-amino acid (8mer) fragment of the C12 antihypertensive peptide. Journal of Dairy Science. 99(5):3263-3266. doi: 10.3168/jds.2015-10437.
