Prediction of Lactose Crystals Present in Supersaturated Lactose and Whey Solutions by Measuring the Water Activity

Figures & data

Figure 1 Changes in the solubility of lactose and water activity of the lactose solution over time (at 20°C). The values presented are the average of three replications (measured values were the same within replicates).

Figure 2 Changes in the water activity of lactose and whey solutions at 20°C (solid lines are the linear predicted line).

Table 1 Measured and predicted water activities of crystallizing solution of supersaturated lactose and whey

Time (days)	Lactose content in solution (g α-lactose monohydrate 100 g^−1 water)	aw measured	aw predicted by Eq 1
0	54.5	0.970	0.970
1	51.8	0.972	0.971
2	45.1	0.976	0.976
3	39.9	0.978	0.979
4	36.9	0.980	0.980
5	33.2	0.982	0.981
6	32.3	0.983	0.982
	MAE (%) ^a	0.037
^aMean absolute error (MAE) % = 100[Σ│ (aw measured – aw expected) │/│ aw measured │]/n.

Table 2 Water activity prediction of supersaturated lactose solutions by Raoult, Norrish, and Money-Born models

	aw measured		aw predicted
Lactose (g lactose 100 g^−1 of water)	Lactose	Whey	Raoult	Norrish	Money-Born
18.3	0.989	0.980	0.990	0.989	0.986
23.0	0.986	0.976	0.988	0.987	0.982
27.6	0.983	0.973	0.986	0.984	0.979
32.2	0.980	0.968	0.983	0.981	0.975
36.7	0.979	0.963	0.981	0.977	0.972
41.3	0.976	0.959	0.979	0.974	0.968
45.8	0.973	0.955	0.976	0.971	0.965
50.4	0.970	0.951	0.974	0.968	0.962
MAE Lactose (%) ^a			0.28	0.12	0.58
MAE Whey (%) ^a			1.71	1.38	0.83
^aMAE % = 100[Σ│ (aw lactose observed – aw calculated) │/│ aw lactose observed │]/n.