Location: Dairy and Functional Foods Research
2020 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
This is the final report for the Project 8072-41000-097-00D which ended November 19, 2019. A bridge project has been established (see 8072-41000-100-00D).
This study focused on the incorporation of non-thermal processes 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 and cottage cheese, and the effects of the processing on the bioactive compounds as well as the quality traits and shelf-life of the cheeses. The effects of processing were related to the effects of reducing sodium, enhancing levels of healthy lipids, and the formation of bioactive peptides from the proteins within the cheese matrix. This research provided basic and applied information on the processing stability of the bioactive compounds, the function of the bioactive compounds within the cheese matrix, and the feasibility of using non-thermal processing technologies to create healthier versions of cheese demanded by health-conscious consumers.
Microfluidization, a nonthermal process which homogenizes milk under high pressures and shear, alters the physical and functional properties of cows’ milk. ARS scientists at Wyndmoor, Pennsylvania, demonstrated that microfluidization, a nonthermal process, homogenized milk at high pressures and shear, which lowered bacterial counts, reduced milk fat droplets size by 10-20 fold, and altered the fat-protein interactions. By altering the pressure and temperature during processing, the ability of the milk to gel and form curds was changed to different degrees. This process was compatible with HTST pasteurization, but not with ultra-high temperature (UHT) processing.
The curds formed using microfluidized milk had unique textures and functionalities that can be used to make novel high-moisture cheese or other dairy foods (i.e. spreads, snacks, and desserts). Fractions that concentrate the healthy fats from cows’ milk can be made although the low yield limits its use to small-batch, high-value applications.
Dairy fat contains polyunsaturated fats (PUFAs), such as omega-3 and conjugated linolenic acid (CLAs), that are considered to be beneficial to human health, but they are found in very small amounts in milk. ARS scientists at Wyndmoor, Pennsylvania, showed that a modified, more efficient, cold fractionation technique produced a fraction from heavy cream that contains up to 50% more of the healthy PUFAs. The yield of this PUFA-enhanced fraction is very small (5%) and the amount needed to significantly increase the level of PUFAs in cheese does not make this process economically feasible to be used in cheese making. However, this approach and the PUFA-enhanced fraction may have use in other small-batch, high-value applications, such as production of dietary supplements.
The contingency plan to use plant-based oils was initiated when the dairy-based PUFA-enhanced fractions could not be produced for use in cheeses and other dairy products. In this case, two oils, perilla and flax seed oils, containing a high level of omega-3 fatty acids at about 60%, were compared to canola oil, which contains a lower level of omega-3 (8%) fatty acids. Stable emulsions of perilla and canola oils (0.5%) but not of flax seed oil, were made when using homogenization, microfluidization and ultrasonication. That for milk fat was 2.5% fat. Perilla oil might be considered because of its higher C18:3 content.
Microfluidization and ultrasonication were shown to reduce fat droplet sizes and altered the fat-protein interactions in milk. Processing under isothermal conditions using high pressure homogenization or ultrasonication, resulted in altered formation and strength of enzyme-set milk gels, which can affect the microstructure and texture of cheese curds. Comparison of the two NTP treatments showed limitations to both approaches. Microfluidization 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 exposures are needed to obtain uniform submicron sized fat droplets.
This project participated in the ARS Grand Challenge project “Develop genetic and management practices in the dairy industry for delivery of products that are nutrient dense and positively impact public health, but with a lower environmental impact.” Team members contributed their processing expertise to the development of the project and provided key input in designing the first working collaboration of the project. In this first study, six shipments of 154 milk samples were sent to Wyndmoor, Pennsylvania, for analyses; including proximate analysis on fresh samples and direct lactose analysis on frozen samples. One team member is on the database subcommittee and provided the proximate analysis data set (first to be completed) to help develop how meta data analysis will be coded/organized and made available to users. Results from this project will enhance our understanding of the relationship between the environment (soil, plant, energy usage), farm (feed, animals, management), processing, and nutrition/wellness of dairy products in human health.
ARS scientists from DFFRU, Wyndmoor, Pennsylvania, attended the annual Northeast Pasture Consortium (NEPC) Annual Meetings. Discussions on current milk research with NEPC board members and a few of the milk processors focused on improving the marketability of milk from small farms through enhancements in the nutritional- and health-value of dairy foods, through our work in fatty acids. Discussions with animal and human nutritionists on our research involving fatty acids in milk and cheese focused on enhancing the nutritional- and health-value of dairy foods. As a result of one of our discussions, NEPC board members asked a team member to talk about the current research status of 'a2' milk at a monthly NEPC board teleconference.
Accomplishments
