15A-16 |
Process for calcium retention during skim milk ultrafiltration |
H. K. VYAS and P. S. Tong. Dairy Products Technology Center, California Polytechnic State Univ., 1 Grand Ave., Bldg. 18-2, San Luis Obispo, CA 93407 Lactose is separated from milk or other fluid dairy products or by-products for a variety of reasons. Ultrafiltration is a known way of removing lactose from these products. However, during ultrafiltration valuable minerals like calcium, are also lost into permeate. The objective of the present study was to develop a process to retain calcium during lactose reduction by ultrafiltration of fluid dairy products. Skim milk was concentrated to 4X level (volume basis) with help of 10 kDa membranes using a stirred cell at laboratory scale and a spiral wound crossflow unit at the pilot scale. The resultant permeate containing lactose and minerals was either (1) heat-treated (63 ºC for 30 min), or (2) pH adjusted (to 8.0) or (3) pH adjusted (to 8.0) and then heat-treated (63 ºC for 30 min). Then the treated permeates were refiltered using the same clean membrane. Skim milk, retentates, permeates and treated permeates were analyzed for total solids, ash, calcium and lactose content. The process was first developed at laboratory scale and then its applicability was tested at the pilot scale. About 76% of the total lactose and 50% of the soluble calcium present in skim milk permeated through the membrane during ultrafiltration. The three treatments applied produced white precipitates and turned the clear permeates turbid. On refiltering the treated permeates approximately 42, 50 and 70 % of the total calcium present could be recovered from heat-treated, pH adjusted, and pH adjusted and heat-treated permeates, respectively. Similar results were obtained for both laboratory and pilot scale experiments. There was no marked change in the lactose content due to any of the three treatments and subsequent refiltering of the treated permeates. Maximum calcium was recovered using pH adjustment and heat-treatment to the permeate followed by refiltration.
Session 15A, Dairy Foods
|