@article{park_allen_2000, title={Antigenicity of casein phosphopeptides prepared with immobilized glutamic acid-specific endopeptidase or trypsin}, volume={20}, ISSN={["0271-5317"]}, DOI={10.1016/s0271-5317(00)00129-9}, abstractNote={The antigencity of phosphopeptides derived from the hydrolysis of αs- or β-casein with trypsin or glutamic acid-specific endopeptidase (GSE) was studied using a rat model system. Relative levels of specific IgG and IgE made in response to intraperitoneal sensitization to tryptic or GSE hydrolysates of αs- or β-casein or derivatives were determined using indirect and amplified indirect ELISA, respectively. Serum was tested for antibodies to whole, αs- or β-casein. More reactive IgG against whole and αs-casein than β-casein was expressed. Hydrolysis of αs- or β-casein with either trypsin or GSE did not reduce antigenicity relative to intact protein, but tryptic αs-casein phosphopeptides were significantly less antigenic than intact αs-casein and its hydrolysates. The antigenicity of tryptic hydrolysis was less than that of GSE hydrolysis. These results suggest that tryptic phosphopeptides could be used as a food ingredient with hypoallergenicity.}, number={3}, journal={NUTRITION RESEARCH}, author={Park, OJ and Allen, JC}, year={2000}, month={Mar}, pages={359–370} }
 @article{park_swaisgood_allen_1998, title={Calcium binding of phosphopeptides derived from hydrolysis of alpha(s)-Casein or beta-Casein using immobilized trypsin}, volume={81}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(98)75844-8}, abstractNote={Abstract Calcium binding to casein phosphopeptides that were derived from α s -CN or β -CN was studied. Purified α s -CN or β -CN was prepared from fresh skim milk using an anion-exchange column. Peptides were prepared by casein hydrolysis using a fluidized bed bioreactor containing 2ml of immobilized trypsin (activity: 49.4 U/g of beads). The disappearance of intact protein and the appearance of products of low molecular mass were monitored by SDS-PAGE. α s -Casein and β -CN hydrolysates were loaded on an anion-exchange column, followed by stepwise elution with 0, 0.1, 0.2, 0.4, and 0.5 M KCl in equilibration buffer to separate the phosphopeptides from the other casein peptides. Protein and P were measured in the elution peaks. Calcium binding to each fraction was determined with a Ca-selective electrode. Electrophoresis showed that intact proteins were hydrolyzed rapidly, and peptides appeared on the gel in greater concentrations as the incubation time increased. The major products were a main band with a molecular mass of 6.2 kDa from β -CN hydrolysates and a series of bands from 4.0 to 12.8 kDa from a α s -CN hydrolysate. The greatest yield and concentration of phosphate from β -CN hydrolysate were found in the peak that eluted with 0.4 M KCl in equilibration buffer and for α s -CN in the peak that eluted with 0.1 M KCl. The α s -CN phosphopeptides showed greater Ca 2+ binding than the phosphopeptides from β -CN. Separation of casein phosphopeptides using anion exchange was not specific. However, results showed that each peak containing high concentrations of phosphate had Ca 2+ -binding ability. Further characterization of these casein phosphopeptides might result in a Ca-complexing food ingredient.}, number={11}, journal={JOURNAL OF DAIRY SCIENCE}, author={Park, O and Swaisgood, HE and Allen, JC}, year={1998}, month={Nov}, pages={2850–2857} }
 @article{park_allen_1998, title={Preparation of phosphopeptides derived from alpha(s)-casein and beta-casein using immobilized glutamic acid-specific endopeptidase and characterization of their calcium binding}, volume={81}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(98)75845-X}, abstractNote={Abstract Phosphopeptides that were derived from α s -CN or β -CN were prepared with immobilized glutamic acid-specific endopeptidase, and their Ca 2+ binding was characterized. α s -Casein or β -CN was hydrolyzed in a fluidized bed bioreactor containing 2ml of immobilized glutamic acid-specific endopeptidase by recirculating 20ml of α s -CN or β -CN solution (10 mg/ml in 50mM Tris·HCl and 0.02% NaN 3 , pH 8.0) for 3h at 20°C. The molecular masses of casein peptides were monitored by SDS-PAGE. Each hydrolysate was applied to an anion-exchange column using stepwise elution with various concentrations of KCl to separate peptides. The casein phosphopeptide content of the elution profile was monitored by analysis of protein and P concentrations. Calcium binding in phosphopeptide-enriched fractions was determined by CaCl 2 titration and measurement of free Ca 2+ with a Ca-selective electrode. The electrophoresis patterns showed four major peptides having molecular masses of 10.8, 9.0, 6.6, and 3.6 kDa in the α s -CN hydrolysate and 9.3, 8.2, and 6.2 kDa in the β -CN hydrolysate. The highest concentrations of P were detected in the fractions that eluted with 0.4 and 0.5M KCl for the α s -CN hydrolysate and with 0.4 M KCl for the β -CN hydrolysate. The calcium-binding ability was found only in the fraction that was eluted with 0.4 M KCl; the maximum Ca 2+ binding and the apparent binding constant were 0.24 mmol/mg of protein and 75 M –1 , and 0.14 mmol/mg of protein and 148 M –1 , respectively. α s -Casein phosphopeptides had different patterns for Ca 2+ binding than did β -CN phosphopeptides as the total Ca concentration was increased. Calcium binding to these casein phosphopeptides differed from that previously characterized for the tryptic peptides.}, number={11}, journal={JOURNAL OF DAIRY SCIENCE}, author={Park, O and Allen, JC}, year={1998}, month={Nov}, pages={2858–2865} }
 @article{heddleson_park_allen_1997, title={Immunogenicity of casein phosphopeptides derived from tryptic hydrolysis of beta-casein}, volume={80}, ISSN={["0022-0302"]}, DOI={10.3168/jds.S0022-0302(97)76140-X}, abstractNote={The immunogenicity of phosphopeptides derived from tryptic hydrolysis of beta-casein (CN) was investigated in a rat model system. The titers of specific immunoglobulin (Ig)G and IgE antibodies made in response to intraperitoneal sensitization to beta-CN, casein phosphopeptides, and skim milk proteins were examined using indirect and amplified indirect ELISA, respectively. Serum IgG antibodies from rats injected with beta-CN were significantly more reactive to beta-CN, casein phosphopeptides, and skim milk proteins coated on microtiter plate wells than were the IgG antibodies generated in rats that had been subjected to other treatments. A significant difference in titers because of the time of sampling (14 or 21 d postinjection) was noted for IgE but not for IgG. Rats that were injected with casein phosphopeptides did not produce IgG antibodies that crossreacted with either skim milk proteins or beta-CN. Specific antibody levels for the IgE class rarely exceeded those of unimmunized controls. The findings suggest that immunogenicity of the phosphopeptides was reduced compared with that of native beta-CN and skim milk proteins.}, number={9}, journal={JOURNAL OF DAIRY SCIENCE}, author={Heddleson, RA and Park, O and Allen, JC}, year={1997}, month={Sep}, pages={1971–1976} }