The Effect of Soluble Soybean Polysaccharide on Crystallization Behavior of Lactose

Lactose can be recovered from cheese whey permeate concentrate by crystallization, and improving the recovery efficiency and purity of lactose crystals is significant to the profitability of the dairy industry. Lactose is also the major component in spray-dried dairy ingredients such as milk and whey powder. Lactose in spray-dried powder is amorphous and causes quality problems such as caking due to the crystallization of amorphous lactose during storage. Technologies are thus needed to improve the crystallinity of spray-dried lactose. In this study, soluble soybean polysaccharide (SSPS) was studied for the effects on lactose crystallization in aqueous solutions and during spray drying. In aqueous solutions with 40% w/w lactose, the addition of less than 1% w/w SSPS facilitated lactose crystallization, more significant at 0.1% SSPS than at 0.5 and 1% SSPS, and the improvement in crystal yield was more significant under seeded conditions than spontaneous crystallization. SSPS was observed to promote the nucleation of lactose, but the promotion effect was offset by the reduction in crystal growth due to increases in viscosities at increased SSPS concentrations. The highest crystal yield after 24 h at 30 °C (54.7%) was observed for the treatment with 0.1% SSPS and 0.5% lactose seed, was significantly higher than the 34% yield of the control without SSPS, and reached about 84.4% of the maximum possible yield. The purity of lactose crystals was not affected by addition of SSPS based on differential scanning calorimetry, X-ray diffraction spectroscopy, and Fourier transform infrared spectroscopy. For spray-dried powder produced at SSPS:lactose mass ratios of 0:1, 1:9, and 1:19, the addition of SSPS improved the crystallinity and yield of spray-dried powders. The highest crystallinity, 57.7%, was obtained at a SSPS:lactose mass ratio of 1:9, and the increased crystallinity prevented the clump formation of spray-dried powder during ambient storage and accelerated testing at 65% relative humidity and 25 °C. Therefore, SSPS can be used to facilitate lactose recovery from cheese whey and improve the quality of spray-dried powder containing lactose.