Date of Award
Master of Science
Food Science and Technology
Mark T. Morgan, Tao Wu
Encapsulation of lactase has been considered as an alternate strategy to overcome lactose intolerance and negative sensory properties of lactose-free milk if capsules can be dispersed in milk, retain lactase during storage, and selectively release lactase in the intestines after ingestion. The overall objective of this thesis was to study lactase-loaded biopolymer capsules with characteristics suitable for delivering lactase in milk. Lactase-loaded zein/pectin capsules were prepared by antisolvent precipitation of zein with assistance of ionic cross-linking of low-methoxyl sugar beet pectin (SBP) with Ca2+. Mass ratios of zein:SBP and CaCl2:SBP were studied for impacts on encapsulation efficiency, particle size and morphology, zeta potential, and stability and turbidity of dispersions. Encapsulation of lactase was verified using electrophoresis of capsules. The capsule formation mechanisms were additionally studied for surface hydrophobicity (H0), dispersion stability, and fluorescence spectroscopy as affected by molecular force blockers. Capsules were assessed for release kinetics at 4, 25, and 37 °C at pH 7, lactose hydrolysis during 3-week storage in whole and skim milk, and lactose hydrolysis during in vitro digestion. The optimal formulation was observed at a zein:pectin mass ratio of 3:2 and a pectin:CaCl2 mass ratio of 5:1 corresponding to an encapsulation efficiency of 93.0%, Z-average mean diameter of 652.7 nm, and the spherical capsules. The SDS-PAGE of the capsules showing protein bands corresponding to lactase and zein verified encapsulation of lactase. Zeta potential and H0 revealed the core-shell structure of the capsules. Electrostatic interactions, hydrophobic interactions, hydrogen bonding, and Ca2+ cross-linking between SBP molecules were responsible for nanoparticle formation based on turbidity and fluorescence intensity of dispersions as affected by sodium dodecyl sulfate, ethylenediaminetetraacetic acid, and urea. Capsules resulted in 33.1% and 40.0% lactose hydrolysis in whole and skim milk, respectively, at milk storage conditions. During in vitro digestion, encapsulated lactase resulted in 100 % and 89.4 % lactose hydrolysis in whole and skim milk, respectively, contrasting with negligible lactose hydrolysis by the same units of free lactase. Findings from this thesis suggest the potential of the studied capsules to incorporate lactase in milk, prevent lactose hydrolysis during storage, and hydrolyze lactose in milk during digestion.
Dong, Lianger, "Encapsulation of lactase in dispersible biopolymer particles as a potential delivery system to control lactose hydrolysis in milk. " Master's Thesis, University of Tennessee, 2018.