| Summary: | 碩士 === 大葉工學院 === 食品工程研究所 === 84 === In this study, the replacement of synthetic colorants
with natural colorants to tincture candied fruits was
investigated first, and then the analytic method of synthetic
colorant was studied. In the replacement of synthetic colorants
with natural colorants, the candied mei and olive fruits,
tinctured with a 0.25% Carmine plus 0.5% Monasco Red solution
and a 2.0% Carmine plus 1.0% Monasco Red solution,
respectively, had higher color sensory evaluation scores. The
candied plum and mango fruits, tinctured with a 0.5% Carmine
plus 0.5% Monasco Red solution and a 0.25% Melon B plus
0.5% Chlorophyll solution, respectively, also had higher
color sensory evaluation scores. These mixed solutions of
natural colorants showed stable to heat and light stability
test. Moreover, the color of the candied mei, plum, olive, and
mango fruits, tinctured with suitable colorants and then packed
in OPP/CPP and stored at room temperature for 240 days,
changed slightly in the beginning period (about 60 days) and
kept steadily thereafter. The color sensory evaluation score
of the candied olive fruit after 240-day storage was
equivalent to that of marketing product, while the color
sensory evaluation scores of the candied p lum and mango fruits
were higher than those of marketing products. In the
analysis of synthetic colorants, thin-layer chromatography
(TLC) was first conducted to qualitatively analyze the
colorants. The results showed that the solvent mixture of n-
butanol, acetic acid, and water with a ratio of 10: 5: 6 and
the other solvent mixture of ethyl acetate, methanol, and
ammonia with a ratio of 3: 1: 1 were two better solvents
for developing the tested colorants in thin-layer chromatogram.
Then, in the analysis of synthetic colorants using visible
chromatography, the results showed that the number of the peaks
appeared in the absorption spectrum of visible range was the
same as that of the components in the tested synthetic
colorant mixture. The maximum absorption wavelengths of
these peaks were the same as those of the components, and
the absorbance of each peak also had a positive proportion to
the concentration of the component. Therefore, the content of
the component in the colorant mixtu re can be determined
from the its absorbance of visible spectrophotometry.
However, some colorant mixtures showed only one broad peak in
the visible spectrum. In this situation, The content of the
component in the colorant mixture could be determined using
regression analysis between the mixing ratio of the component
in the colorant mixture and the maximum absorption
wavelength of the mixture. According to the above results, the
identification of the components in a synthetic colorant
mixture can be achieve d using TLC, and the contents of the
components can be determined using visible spectrophotometry.
Finally, the analysis of synthetic colorants using
TLC, visible spectrophotometry, and high performance
liquid chromatography (HPLC) was compared. It was found
that TLC was a rapid and convenient method, but it had a
larger deviation, and the sample should be concentrated before
testing. HPLC was a rapid and high-precision method. However,
two different mobile phases should be used to minimize the
interference of the solvents used in the extraction of
colorant samples. Visible spectrophotometry was a high-
precision and feasible method, although its analytic
procedure was complicated when the maximum wavelengths of
the components in colorant mixture were close to each other
and resulted in only one broad peak in the visible spectrum.
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