Lactulose is efficiently synthesized from lactose using
catalysts such as boric acid and triethylamine . However, since
neither catalyst is food-safe, both must be removed after
processing. Lactulose is also produced inadvertently during heat
treatment of dairy products, although in small quantity. Studies
have indicated that altering the heat processing conditions can
improve lactulose yield .
A high lactulose , mixed carbohydrate preparation was produced
without the use of toxic catalysts . Using two Taguchi's fractional
factorial designs, eight factors were tested as to their influence
on lactulose yield : pH, lactose, NaOH, citrate and phosphate
concentrations, heating temperature and duration , and purification
of the lactose substrate. In the first design, lactose
concentration (at levels of 40, 79, and 155 mg/mL) , pH (9.0, 10.5,
and 12.0), heating temperature (90, 110, and 130°C), citric acid
concentration (40, 70, 100 mM) and in the second design, NaOH
concentration (18, 50, and 100 mM) , was shown to significantly
influence lactulose yield . All other factors did not significantly
influence lactulose yield at the selected levels . The interactions
of lactose, citrate , and phosphate concentrations of the first
design also significantly influenced lactulose yield . The
conditions selected for the conversion of lactose to lactulose was
decalcified whey permeate at > 70 mg/mL lactose , a pH of 10.5-11.0,
with an added 50 mM sodium citrate , was heat treated at 110°C for
10 minutes. Approximately 30% of initial lactose was converted to
lactulose via primarily the Lobry de Bruyn and Alberda van
Ekenstein transformation.
Again using a Taguchi design, four factors were tested to if
they significantly influenced the preferential precipitation of
lactose over lactulose in a cooled aqueous solution : pH, sugar
concentration, temperature decrease, and final temperature. The pH
of the mixed carbohydrate solution (at levels of 7.0, 9.0, and
10.7) and sugar concentration (29, 39, and 52%) both significantly
influenced either the lactulose yield of precipitation or the sugar
ratio in the decant. For further study, the lactulose preparation
was concentrated to approximately 50% solids and pH 10.5, cooled
from 65° C to 20° C at 5C°/hour, and held for 24 hours,
preferentially precipitating lactose over lactulose. After one cooling cycle, there was a lactose yield of approximetly 82% and a 1:1 lactose: lactose ratio . After a second precipitation of
the decanted portion , there was a 78% lactulose yield and a 3.4:1
lactulose : lactose ratio . There was a total loss of about 40% of
lactulose through the two precipitation cycles. Ion-exchange
columns removed the majority of the natural and added salts from
the lactulose preparations. Activated charcoal removed most of the
brown colour of the preparation but also 30% of the solids .
The final syrup contained 59% lactulose , 26% lactose, 5.0%
galactose, 1.0% glucose, and 0.81% fructose, based on total solids .
Carbohydrates were assayed using an enzymatic spectro-photometric
method. An unidentified substance was detected using thin - layer
chromatography of carbohydrates. / Land and Food Systems, Faculty of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/5885 |
| Date | 05 1900 |
| Creators | Layton, Anne Alexandra |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 5376078 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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