| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 85 === Dental caries is perhaps the most prevalent disease affecting humans today
,which is mainly caused by the Streptococcus mutans by forming the dental plaq
ues.The preventive methods, active and passive immunizations, were suggested b
y many investigators. Owing to the predominant side effects of active immuniza
tioninduced by causative bacterium, passive immunization with hen-yolk antibod
y (immunoglobulin in yolk, IgY) is preferably favored. In this experiment,
hens were im immunized on thighs by using tie whole cells of Streptococcus mut
ans (c) as antigen and the eggs were collected to investigate the changes of I
gY content during the immunization period. Severalproperties of crude IgY, sep
arated from yolk by the addition of 0.225% high methoxy pectin, were examined
to understand the stability during the food processing. In thermal stability t
est, protectants such as sugars, glycerol and amino acids, were applied. Gastr
ic-intestinal enzymes, such as trypsin,chymotrypsin and pepsin (E/S=1/40, 37℃
), were also employed to investigate the relationships between the degree of h
ydrolysis of IgY and the changes of binding activities to Streptococcus mutans
(c), E. coli and Salmonella. Hydrolysates, prepared with the above three enzy
mes, were applied to gel filtration chromatography on Sephacryl S-300 and the
fractions were pooled to identify the positions of protein fragments with IgY
activity by double immunodiffusion method. The molecular weights of IgY hydrol
ysates were determined simultaneously by non-reductived SDS-PAGE. The effects
of pH and enzymes on IgY activity of freezed-dried yolk powder and powders coa
ted with 5% arabia gum were also examined. Storage tests of freezeddried yolk
powder packed under various conditions, i.e. N2 gas, air, aluminum foil and p
olyethylene bags, at 4°or 25℃, were conducted and the changes of IgY activi
ty were checked by ELISA method. Results showed that the Ig Y activity of b
oth yolk and crude Ig Y decreased with increasing heating temperature (70° 74
° 78°and 80℃), but the rate of denaturation of IgY between those two sample
s were not significant. The addition of high concentration (50%) of sucrose or
maltose showed significant protection effect on thermal denaturation of IgY,
however, 2% glycine in the samples displayed satisfactory effect. No remarkabl
e decline of IgY activity was observed when samples, yolk powder and crude IgY
, were digested with trypsin (pH 7.6), chymotrypsin (pH 7.6) or pepsin (pH 2.0
) at 37蚓 for 8 hr when observed with ELISA method on the binding activity to
E. coli and Salmonella. The second peak of gel filtration chromatographic pat
terns of crude IgY digested with chymotrypsin and pepsin (E/S=1/40, 37℃, 8 hr
) on Sephacryl S-300 were both found to be with IgY activity by Double immunod
iffusion method, which revealed the fact that high degree of hydrolysis can on
ly destroy the IgY activity. Similar to the results of freezed-dried processin
g, yolk powder spray-dried at low temperature (lower than 60℃) could maintain
the activity more than 90%, especially for that added with 5% arabia gum as c
oating material. During the storage test, IgY activity of both yolk powder and
crude IgY were quite stable at 4°or 25℃ for almost three months.
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