Location: Dairy and Functional Foods Research
2022 Annual Report
Objectives
Objective 1: Characterize bioactive peptides released from dairy proteins by enzymatic digestion and investigate the effect of protein-carbohydrate interactions on the stability and bioavailability of these peptides in dairy foods. [NP306, C1, PS1C]
Sub-objective 1.A: Production and characterization of bioactive peptides from dairy proteins through enzymatic digestion.
Sub-objective 1.B: Develop encapsulation-based delivery systems to protect and enhance the bioactivity and effectiveness of these peptides.
Objective 2: Identify novel bioactive prebiotic oligosaccharides from plant (fruit and vegetable) and animal (milk) sources in food processing low-value by-products. [NP306, C1, PS1B]
Approach
New bioactive compounds will be developed from dairy proteins, oligosaccharides and plant dietary fiber. Bioactive compounds will include antioxidative peptides from milk and dairy products. We will identify these bioactive peptides released through the enzymatic digestion of dairy proteins and products, and investigate the effect of milk fatty acids and oligosaccharides on the production of these peptides. Novel prebiotics will be characterized and compared with galacto-oligosaccharides derived from lactose and milk oligosaccharides. Pectic oligosaccharide prebiotic activity will be evaluated using animal models, mixed culture fecal fermentation and determining their effects as human bioactive food ingredients. We will develop synbiotics in live microbial systems such as yogurt and with tea products. Oligosaccharide anti-adhesive activity against pathogens will be determined with tissue culture cells. We will determine dietary fiber characteristics in fruit and vegetable processing byproducts.
Progress Report
FOr Objective 1.A Isolation of the bioactive peptides and screen for bioactivities: Lactobacillus species have been used extensively for dairy fermentation to develop a wide range of value-added food products. Numerous L. helveticus strains are known for their ability to hydrolyze milk proteins, mainly because many produce cellular envelope proteases. Different strains may generate peptides of varying bioactivities, such as antihypertensive and antioxidative activities. These activities may depend on fermentation conditions and specific cultural compositions. Currently, we are carrying out fermentation experiments using commercial milk protein products, including organic nonfat dairy milk, micellar casein, whey protein isolate, and a combination of micellar casein and whey protein isolate at concentrations typically found in cow milk. We will perform fractionation experiments to identify specific peptides that are responsible for these activities. We are also investigating differences in peptide distribution, degree of digestion, and specific antihypertensive, antioxidative, and antimicrobial activities in the fermented products caused by the strain variations. This research effort could help us select the strains and fermentation conditions that may be used to obtain highly active new dairy products.
For Objective 1.B. Test dietary fiber as possible encapsulation wall materials: Building on our previous results on the fabrication of whey protein-based edible antimicrobial food packaging materials, such as coating and composite films, we continued our research on constructing conjugates of milk protein and arabinoxylan, a low-value by-product of the corn wet or dry milling process. We continue to test the viability, efficiency, and performance of these food-grade materials as encapsulation wall materials to stabilize and deliver bioactive compounds, including those bioactive peptides generated from objective 1A and other fat-soluble micronutrients (flavonoids and polyphenol compounds). This research could help alleviate the poor bioavailability of these micronutrients when incorporated into food products.
For Objective 2 Characterize pectic oligosaccharides: Red beet pectic oligosaccharides were characterized. Red beet pomace, the fraction remaining after commercial puree extraction, contained dietary fiber (50.8%), that was largely insoluble (40.1% versus 10.7% soluble dietary fiber) with pectin as the major polysaccharide; sucrose (8.07%), fructose (1.14%) and glucose (2.33%) free sugars; protein (10.2%), and fat (3.02%). Malto-oligosaccharides and methyl-esterified, acetylated and feruloylated rhamnogalacturonan I oligosaccharides with branched arabinogalacto-oligosaccharide side chains were detected by MALDI-TOF Mass Spectrometry and Nuclear Magnetic Resonance analysis. Red beet pectin, acid-extracted with a microwave using 10 minutes and 80°C conditions, had high molar mass (1036 kDa) with viscosity that was similar to sugar beet pectin extracted under the same conditions. A random coil shape was confirmed for red beet pectin microwave extracted under 3 min and 120°C conditions. Longer microwave extraction times and microwave extraction at pH 1 produced compact spherical red beet pectin with lower molar mass and viscosity. The structural properties of these red beet pomace and fiber fractions suggest that they can function to thicken and stabilize food systems, and the structure of the pectin fractions indicate strong potential as a prebiotic food.
Accomplishments
1. Red beet functional food. Red beet is considered a healthy food consumed fresh in salads, or juices, yet more data is needed to support health claims for this vegetable. The structural composition of red beet fiber puree remaining after commercial juice processing was described in greater comprehensive detail than previously possible. Health-promoting carbohydrate dietary fiber, protein and low fat were present. Some of these compounds are known to promote the growth of health-beneficial human gut bacteria or may prevent chronic diseases. The red beet fiber composition can also act as an emulsion stabilizer and thickening agent in food formulations. This information will be useful to understand the multiple health benefits of red beet and provide more value for this specialty crop food.
2. Whey protein and dietary fiber are used as antimicrobial food packaging materials. ARS scientists in Wyndmoor, Pennsylvania, created conjugates between whey protein isolate (WPI) and corn fiber gum through a food-grade chemical reaction. We then used these conjugates to develop films and coatings using carvacrol as the antimicrobial agent in the formulations. We demonstrated that the films and coating solutions are highly effective against Escherichia coli, Salmonella, Listeria, spoilage fungi, and bacteria using both in vitro and in vivo tests. This research effort will meet the increasing demands for natural, biodegradable, and environment-friendly packaging materials and safe and effective antimicrobial agents suitable for various foods. It will also help expand the marketability of whey protein (a by-product from cheese-making) and corn fiber (a by-product from corn processing).
Review Publications
Liang, C., Garcia, R.A., Qi, P.X., Lee, C. 2022. Flocculation performance and mechanisms of heme-removed and methylated bovine hemoglobin. Separation and Purification Technology. https://doi.org/10.1016/j.seppur.2022.121017.
Du, R., Qu, Y., Zhao, M., Liu, Y., Qi, P.X., Sun, X. 2022. Logistic modeling to predict minimum inhibitory concentration of olive leaf extract against Listeria monocytogenes. PLoS ONE. https://doi.org/10.1371/journal.pone.0263359.
Cao, F., Liang, M., Liu, J., Liu, Y., Renye Jr, J.A., Qi, P.X., Ren, D. 2021. Characterization of an exopolysaccharide produced by Streptococcus thermophilus ZJUIDS-2-01 isolated from traditional yak yogurt. International Journal of Biological Macromolecules. https://doi.org/10.1016/j.ijbiomac.2021.10.055.
Hotchkiss, A.T., Chau, H.K., Strahan, G.D., Nunez, A., Simon, S., White, A.K., Dieng, S., Heuberger, E., Yadav, M.P., Hirsch, J. 2022. Structural characterization of red beet fiber pectin. Food Hydrocolloids. 129:107549. https://doi.org/10.1016/j.foodhyd.2022.107549.
