Treatment of Lactose with Alkaline Methanolic Solutions: Production of Beta-Lactose from Alpha-Lactose Hydrate

Crystallization of lactose from methanolic solutions of sodium hydroxide can be used to prepare /3-lactose from c~-lactose hydrate.Conversion of 90 to 93% c~-lactose hydrate to /3-1actose can be achieved by 2 h refluxing with any ratio of lactose to methanol as long as the methanol contains from .02 to .06% (wt/vol) sodium hydroxide and less than 13% (wt/wt) moisture.At room temperature, conversion was complete in 10 h at all ratios of c~-lactose hydrate to methanol containing from .1 to .3% (wt/vol) sodium hydroxide and no more than 3% (wt/wt) moisture.The conversion of ~lactose hydrate to /~-lactose ceased when moisture was above 3.5% (wt/wt) at room temperature and 13% (wt/wt) at reflux.With sodium hydroxide concentrations above .06%,at reflux, or above .3%at room temperature, alkaline rearrangement took place, and lactose was converted into a yellow mixture of degradation products.