| Summary: | 碩士 === 國立臺灣大學 === 食品科技研究所 === 86 === Galactooligosaccharides (GalOS) can be produced from lactose by an enzymat
ic transgalactosylation reaction.It has been shown that GalOS can induce the
growth of bifidobacterium, a healthy microbe, in the intestine of humans. The m
ain goal of this study was to evaluate the potential of manufacturing low-lact
ose- and high-GalOS-milk (LLHGM) products using b-galactosidase. Two appro
aches for manufacturing LLHGM products were considered in this study. Thefirs
t mthod used b-galactosidase to transfer the lactose in milk to GalOS directl
y. The second method applied ultrafiltration techniques to separate the lactos
e in milk from other big moleculars, such as proteins, and then transferred th
e lactose in the permeate to GalOS by b-galactosidase, and finally added the p
ermeate back to the retentate. Our results indicated that the optimal cond
itions for the direct enzymatic approach for producing LLHGM were found to be
16.7% lactose concentration, 5.1% enzyme/substrate ratio at 47oC for 1.4hr, wi
th the maximum yield of 22.8% GalOS and the residue of 34.7% lactose. Neverth
eless, the optimal conditions for the enzymatic reaction in the permeate was 2
5.3% lactose concentration, 6.7% enzyme/substrate ratio at 50oC for 3.5hr, wit
h the maximum yield of 31.1% GalOS and the residue of 35.3% lactose. Alth
ough the yield of GalSO under the enzymatic reaction in the permeate was signi
ficantly higher than that under direct enzymatic reaction in milk, the yield o
f GalSO calculated as a ratio to the total lactose in milk made no significant
difference between the two cases. The results further indicated that when mi
lk was processed by ultrafiltration, the yield of GalSO in terms of the total
lactose depended upon how well the system can separate the lactose. In other
words, the more lactose in the permeate, the higher the yield of GalSO. Howev
er, the cost for the operation of ultrafiltration is expensive, particularly w
hen high efficiency in separating the lactose is desired. Therefore, it requir
es furtherinvestigation to determine whether manufacturing LLHGM products by a
pplying ultrafiltration techniques is economically feasible.
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