| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 84 === Nata is a fine cellulose pellicle formed by the bacteria of
Acetobacter aceti subsp. xylinum through the fermentation of
fruit juice or plant extract. The objectives of this study are
to investigate the effect of fermentation conditions to the nata
formation using Ponkan citrus juice, Valencia orange juice, and
their pulp-wash juices as substrates, and to examine the
physico-chemical properties of the nata formed under different
fermentation conditions.
Fermentation of juice samples using a two-stage method
resulted in better yields as compared to non-shaking control
experiments. The nata formed by the fermentation of single
strength juices had better yields as compared to nata formed
by using pulp-wash juice as substrate.
For pulp-wash juices containing low soluble solid, it is
necessary to fortified the juices with sugar to approximately
10°Brix. Pulp-wash juices fortified with fructose gives the
highest nata yield as compared to glucose and sucrose.
There is no significant difference on nata yield among using
coconut milk and respective citrus juices in the first stage
fermentation then using Ponkan juice or Valencia juice as
substrate in the second stage. However, averaged nata yield of
0.28g/mL is obtained when using coconut milk as first stage
substrate and Valencia pulp-wash juice as second stage substrate,
which is higher than the averaged yield of 0.14-0.20g/mL in
fermentation processes using Valencia pulp-wash juice as
substrate at both first and second stages.
The nata''s lower interface colors varies depending on the
types of citrus juice as substrates. The results of texture
analysis indicates that nata from citrus juice fermentation has
similar texture to the nata de coco.
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