Chemistry Reference
In-Depth Information
100
40 °C
50 °C
60 °C
10
70 °C
1
160 180 200 220 240 260 280 300 320 340 360 380 400 420 440 460 480 500
Concentration [kg anhydrous lactose.m
-3
solution]
Figure 4.9.
Dissolution times for producing solutions with lactose concentrations of
160-500 kg/m
3
[-- -- 50 mm, - - - 150 mm, ---- 400 mm] (data from Hodges et al., 1993; Lowe
and Paterson, 1998).
process takes 600 min and is governed totally by the mutarotation kinetics
and particle size has very little effect. This is still largely true at 208C, where
the increased temperature reduces the dissolution time to 60 min; but at 308C,
the mutarotation reaction is so fast that the mechanism governing the dis-
solution is dependent on mass transfer and the particle size has a large effect
with the time required being 2.5 min for 400 mm crystals, 0.5 min for 150 mm
and 0.1 min for 50 mm crystals. Figure 4.9 covers the range of concentrations
from 160 to 500 kg anhydrous lactose per m
3
of solution.
If the lactose powder contains a range of particle sizes, then the
dissolution time for the largest particle size is the best one to use, but it
will underestimate the time required, especially if near-saturated solutions
are being produced. The curves have been stopped short of the saturated
limits. However, within these limitations,thegraphscanbeusedtoestimate
the approximate dissolution times required to achieve a given concentration
when dissolving
-lactose monohydrate in water at a given temperature.
4.5.
The Future for Lactose
Lactose has changed over the last 30 years from being a problem component
in dairy wastewater with a high BOD to being a valuable by-product of the
dairy industry. Lactose will continue to have a market as a required
