Location: Dairy and Functional Foods Research2016 Annual Report
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.
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.
Project research centers on modifying milk using pilot-scale processes which include common dairy unit operations such as fat separation, homogenization, high and ultra-high temperature pasteurization and specialized nonthermal operations such as high pressure homogenization (Microfluidizer) and high frequency ultrasonic processing (Objectives 1 and 2). The key pieces of equipment are on-site or have been purchased recently. The nonthermal processing (NTP) operations used in this project alter the fat-protein interactions in milk. Operating parameters are currently being determined to obtain different degrees of modification in cheesemilk and will be used throughout the project. Preliminary tests have been conducted on 100 mL of whole milk using a bench top ultrasonic unit fitted with a 20 kHZ - 0.5 cm diameter - 9 cm length probe and starting temperatures from 4 – 37 degrees C, energy levels from 25-100%, and time exposures from 1 to 10 min. Whole milk at room temperature was processed from 35 – 170 MPa in the Microfluidizer. Results indicated that it will be possible to make different samples containing specifically sized fat droplets (reducing from about 8.0 to 1.2 um) but that the generation of heat within the NTP unit during the run (10-30 degrees C increase) is an issue that needs further investigation. We are currently planning ways to adapt protocols to generate size-stable samples through investigation of the impact of temperature of the starting milk and/or use of multiple passes and different cooling options to minimize excessive heating of the samples. Milk naturally contains several polyunsaturated fatty acids (PUFA), such as omega-3 fatty acids and conjugated linoleic acid (CLA), which have been shown to be beneficial to human health. Our goal is to improve the health-value of milk and the resulting cheese by enhancing the levels of these healthy lipids in the milk using dairy - sourced fats (Objective 2). Development of techniques to isolate PUFA-enhanced fractions from milk or cream has been initiated. One technique using temperature separation, cooling until the saturated fats have solidified, has shown promise in isolating the healthy PUFAs, which remain liquid below room temperature. It is essential to thoroughly characterize all of the fatty acids present in these fractions, especially the healthy PUFA fats which, because they are similar in structure, tend to be difficult to separate and identify. We are currently testing different analytical instruments, separation columns, and protocols to optimize the thorough characterization and profiling of all of the fatty acids present in the fractions. Techniques, such as electrophoresis (PAGE), ultra-performance liquid chromatography (UPLC), and quadrupole-time of flight mass spectrometer (Q-TOF), are in place to evaluate the peptides in samples and will be used to track the release of peptides from the milk proteins in modified milk, digested samples, and aging cheese throughout the project (Objective 3) with an emphasis on the peptides that have a biological role in maintaining a healthy body, such as casein phosphopeptides (CPP) which are important in transporting calcium in the body.
Tunick, M.H., Ren, D.X., Van Hekken, D.L., Bonnaillie, L., Paul, M., Kwoczak, R., Tomasula, P.M. 2016. Effect of heat and homogenization on in vitro digestion of milk. Journal of Dairy Science. 99(6):4124-4139. DOI: 10.3168/jds.2015-10474.
Tunick, M.H., Thomas-Gahring, A.E., Van Hekken, D.L., Iandola, S.K., Singh, M., Qi, P.X., Ukuku, D.O., Mukhopadhyay, S., Onwulata, C.I., Tomasula, P.M. 2016. Physical and chemical changes in whey protein concentrate stored at elevated temperature and humidity. Journal of Dairy Science. 99:2372-2383. DOI: 10.3168/jds.2015-10256.
Brewster, J.D., Paul, M. 2016. Short communication: Improved method for centrifugal recovery of bacteria from raw milk applied to sensitive real-time quantitative PCR detection of Salmonella spp. Journal of Dairy Science. 99(5):1-5.
Tunick, M.H., Van Hekken, D.L., Paul, M., Ingham, E. 2015. Case study: Differences in milk characteristics between a cow herd transitioning to organic versus milk from a conventional dairy herd. International Journal of Dairy Technology. 68:511-518. DOI: 10.1111/1471-0307.12255.
Ukuku, D.O., Onwulata, C.I., Mukhopadhyay, S., Thomas-Gahring, A.E., Chau, L.I., Tunick, M.H. 2016. Changes in microbial populations of WPC34 and WPC80 whey protein during long term storage. Journal of Food Processing and Preservation. doi: 10/1111/jfpp.12743.
Tunick, M.H., Van Hekken, D.L., Paul, M., Karreman, H.J., Ingham, E. 2016. Case study: Comparison of milk composition from adjacent organic and conventional farms. International Journal of Dairy Technology. 69(1):137-142. doi: 10.1111/1471-0307.12284.