Improving Lactose Crystallization in Milk Sugar Production

This article introduces a new milk sugar technology with improved purification and lactose crystallization. The technology consisted of ultrafiltration of skim milk, nanofiltration of UV-permeate, electrodialysis, condensing, lactose crystallization, and drying. Nanofiltration followed by electrodialysis provided 70–90 % desalting. After condensing to 53–55 % solids, the resulting syrup was heated to 75 °C. The lactose crystallization included two stages. During the first stage, the syrup was cooled by 4–5 °C per 1 min until it dropped down to 27–33 °C, i.e., the temperature of enhanced lactose crystallization. At that moment, 0.01–0.02 % fine crystalline lactose entered the syrup. At the second stage, the crystallized substance continued to cool down at a rate of 1–2 °C per 1 min until the temperature was 10–15 °C. To complete the process, the crystalline lactose remained at this temperature for 5–10 min. The finished product was subjected to granulometric microscopy to determine the homogeneity coefficient. The homogeneity of crystals increased, which means that the quality of the finished product improved. The cooling method was tested on the premises of the Scientific and Experimental Dairy Plant, N. V. Vereshchagin Vologda State Dairy Academy.