Casein was enzymatically hydrolyzed for potential use in a hypoallergenic infant formula. Samples from the digest at different hydrolysis time (HT) intervals were tested for antigenicity, hydrophobicity, net charge (zeta potential), and emulsifying activity. Casein antigenicity loss could be approximated by three-phased first-order kinetics. Extensive antigenicity loss occurred during the first 10% of HT and relatively small changes occurred during the remaining 90% of HT. Hydrophobicity and emulsifying activity decreased, while the magnitude of the net charge increased (P ~0.01) with increasing degree of hydrolysis. Strong correlations (r* 2 0.89) were found among hydrophobicity, emulsifying activity and zeta potential.
The rabbit hyperimmunization model has previously been used to evaluate candidate hypoallergenic protein ingredients. Use of the model has been expanded to include the evaluation of protein hydrolysate formulas. Each formula's immunological reactivity was determined by ELISA measurement of formula-specific rabbit antibody. Animals hyperimmunized with formulas containing extensively hydrolyzed proteins (Alimentum, Nutramigen, and Pregestimil) generated very weak immune responses (< 100 fold antibody increase). Products containing intact or partially hydrolyzed proteins (Similac, Enfamil, Good Start, Beba HA, and Nidina HA) elicited high level (> 10,000 fold increase) immune responses. Immunogenicity results were then compared to measurements of residual antigen content (by inhibition ELISA) and clinical performance. Correlation of formula immunogenicity, antigenicity and clinical performance indicates that the rabbit model is useful for screening "hypoallergenic" formulas to predict allergenic reactivity.
Mono- and diglycerides, as well as commercial monoglyceride emulsifiers, were analyzed by capillary supercritical fluid chromatography (SFC). Carbon dioxide without modifier was used as the mobile phase in the chromatography. Samples were prepared by simply being dissolved in solvents or by propionyl ester derivatization. A capillary SFC methyl silicone column (SB-methyl 100, 100 μm X 10 m, 0.5 μm film thickness, Lee Scientific) was used for the separation, and a flame ionization detector was used for the detection. A calibration standard containing known concentrations of monomyristln, monopalmitin, monostearin, dimyristin, dlpalmitin, and distearin were used for the determination of the response factor (unit weight per peak area) of each analyte. The response factors were used in the quantitation of the analytes in the test samples from their respective integrated peak areas. Monomyristin was used as an internal standard for the quantitation of monoglycerides In commercial emulsifiers. The accuracy of the methods was demonstrated by comparing the percent area (%A) determined by the chromatography with the percent weight (%W) of each of the components in the standard mixture, and the precision of the methods was indicated by the relative standard deviation (RSD). The mean ratio and RSD of %A/%W were 0.98 ± 0.09 (<5%) and 1.01 ± 0.03 (<2.5%) for underlvatized and derivatized samples, respectively. Two lots of commercial monoglyceride emulsifiers were analyzed with and without derivatization, and the results were compared to those obtained by gas chromatography (GC). 7-tests comparing the method means did not indicate any significant mean differences (95% confidence level) between the GC and SFC methods. Nor did the variance ratio F-test indicate that the overall variances of the methods were significantly different. However, the error variance of the SFC-underivatized method was significantly higher than that of the GC and SFCderivatized methods. These results demonstrated the feasibility of applying the SFC technology in the analysis of monoand diglycerides with and without derivatization
Nine laboratories participated in an AOAC International/ International Dairy Federation collaborative study on a liquid chromatographic (LC) method for determination of iodine in milk. Liquid milk is passed through a 25 000 MW membrane filter to remove protein and insoluble material. Iodine (in the form of iodide) in the clear filtrate is separated by reversed-phase ion-pair LC and is detected electrochemically. Participants analyzed 2 commercial pasteurized whole milks and 5 nonfat dry milk powders in blind duplicate. Each sample was tested in duplicate on 2 days. Repeatability and reproducibility standard deviations (sr and SR, respectively) and repeatability and reproducibility relative standard deviations (RSDr and RSDR, respectively) for determinations of iodine in whole milk (mean recovery, 86.7%) were as follows: sr, 22 μg/L; SR, 22 μg/L; RSDr, 8.2%; and RSDR, 8.3%. For powdered milk (mean recovery, 91 %), the values were as follows: sr, 0.14 μg/g; SR, 0.22 μg/g; RSDr, 9.0%; and RSDR, 12.7%. The method was adopted first action by AOAC International.
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