Location: Dairy and Functional Foods Research
2023 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
Sub-objective 1.A. Lactobacillus species are common probiotic bacteria in foods such as yogurt. They hydrolyze dairy proteins by producing cellular envelope proteases, leading to the liberation of potentially bioactive peptides. Different strains may generate peptides of varying bioactivities, such as antihypertensive and antioxidative activities. We experimented with two L. helveticus strains, B1929 and ATCC15009, to carry out fermentations using commercial liquid milk (ultra-pasteurized) and reconstituted dried milk powder to evaluate the resulting antihypertensive activities, as measured by angiotensin-converting enzyme inhibition (ACE-I) activity. We further identified 17 possible peptide fragments from beta-casein, one of the major proteins in milk, that may be attributed to the observed ACE-I activity. We further demonstrated that the ACE-I activity positively correlates with the degree of protein hydrolysis and that liquid milk is a more advantageous medium for producing bioactive peptides.
Objective 2. The synthesis of galacto-oligosaccharides requires the transgalactosylation activity of lactose by beta-galactosidase, often from microbial sources. The beta-galactosidase activity was evaluated among 11 strains of Lactobacillus bulgaricus, and LB11 exhibited the highest activity. When incubated at 50 °C in 50-mM sodium phosphate buffer (pH 6.5) containing either 150 or 300 g/L lactose for 18 hours, over 15 g/L glucose is released. Depending on the starting concentration of cells, varying structures of galacto-oligosaccharide trisaccharides and tetrasaccharides along with galactose and glucose residues were produced in differing quantities.
Detailed composition, fine structure, and function were determined for carrot pomace fiber remaining after commercial juice extraction from carrots harvested at four different times during 2017, in different California, U.S. locations. This pomace was treated with commercial enzymes and the changes in carbohydrate composition were analyzed. The enzyme-treated carrot pomace contained pectic oligosaccharides that were branched, unsaturated, partially acetylated and methylated rhamnogalacturonan I (RG-I) with arabinogalacto-oligosaccharide side chains as well as free galacto-oligosaccharides and galacturono-oligosaccharides detected by MALDI-TOF mass spectrometer (MS) and nuclear magnetic resonance (NMR) analysis. The molecular weight and degree of galacto-oligosaccharide polymerization decreased while water solubility increased following enzymatic treatment. While carrot soluble dietary fiber remained relatively constant, insoluble dietary fiber and total dietary fiber increased during the year. The carrot pomace fiber structure changed between the June and September harvests so that it was more susceptible to enzymatic degradation, and its shape became more linear. The diversity of carrot RG-I oligosaccharide structures was the greatest in the enzyme-treated pomace harvested in September and the RG-I became almost completely debranched by the enzyme treatment for the pomace harvested in December. The structural properties of these carrot pomace fiber fractions suggest that they can function as a low viscosity beverage food ingredient, and the rhamnogalacturonan I structure indicated the potential for anti-viral, immuno-modulatory and prebiotic properties. The rhamnogalacturonan structural composition changes during the growing season highlights the need for bioactivity monitoring of carrot pomace obtained from different sources, and harvested at different times during the year.
Accomplishments
1. Carrot pectin healthy food ingredient development. Carrots are considered healthy foods, but little is known about the variation in carrot pectin structure during commercial processing. The structural composition of carrot fiber that remained after commercial juice and baby carrot processing was described from four harvests in California during 2017 by USDA-ARS scientists in Wyndmoor, Pennsylvania, as health-promoting dietary fiber pectin with low levels of protein and fat. Carrot pectin is known to have anti-viral properties and to promote the growth of health-beneficial human gut bacteria, while the carrot fiber composition also indicated that it could act as a low-viscosity healthy beverage ingredient. This information will be useful to understand the variation in bioactive carrot pectin structure during commercial processing for different harvests during a year and will provide more value for this specialty crop food.
Review Publications
Mendez-Encinas, M.A., Carvajal-Millan, E., Simon, S., White, A.K., Chau, H.K., Yadav, M.P., Renye Jr, J.A., Hotchkiss, A.T., Rascon-Chu, A., Astiazaran-Garcia, H., Valencia-Rivera, D.E. 2022. Arabinoxylans and cross-linked arabinoxylans: Fermentation and potential application as matrices for probiotic bacterial encapsulation. Food Hydrocolloid for Health. https://doi.org/10.1016/j.fhfh.2022.100085.
Hotchkiss, A.T., Chau, H.K., Strahan, G.D., Nunez, A., Harron, A.F., Simon, S., White, A.K., Yadav, M.P., Yeom, H. 2022. Carrot rhamnogalacturonan I structure and composition changed during 2017 in California. Food Hydrocolloids. https://doi.org/10.1016/j.foodhyd.2022.108411.
Jin, Z.T., Yadav, M.P., Qi, P.X. 2023. Antimicrobial and physiochemical properties of films and coatings prepared from bio-fiber gum and whey protein isolate conjugates. Food Control. 148:109666. https://doi.org/10.1016/j.foodcont.2023.109666.
