Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

David J. Schingoethe


The source for lactose production in the United States is almost exclusively sweet (low acid) whey which is the byproduct of cheese manufacture. Its extraction from the whey is motivated largely by pressures to utilize whey components to advantage. The ability to recover lactose efficiently is important to the manufacturers because they are in business ·to make a profit. At current market prices this profit margin will be difficult to realize unless an operation is fairly large a11d quite efficient. However, when considering the alternative of disposing of whey or its components, including lactose, as waste instead of attempting to find uses for them, the manufacturer has a few factors with which to contend. A major consideration is the environmental impact of these products if discarded. Whey, the solids of which are primarily lactose, places a high biochemical oxygen demand (BOD) upon any system into which it is introduced. It has been figured the BOD of whey is 35,000 mg/liter in contrast to only 200-250 mg/liter for domestic sewage (3). This means if a manufacturer chooses to dispose of the whey through the use of a municipal sewage treatment system he will pay dearly for this ·service. Treatment systems generally charge on usage rate and BOD loading, which would result in formidable costs to the manufacturer. Other methods of whey disposal such as lagooning, irrigation, and feeding to livestock have their pros and cons which will not be discussed in depth here (16). In view of these facts, as means of economic practicality and public relations it is advantageous for the manufacturer to attempt retrieval of some if not all the whey components. Public relations are involved because the public takes a dim view of the adverse environmental impact; moreover, consumers do not want to pay higher prices for the product or higher utility costs. This could happen if the manufacturer did not attempt to derive a part of his profit margin by recovering some of the whey components in salable form. Without an attempt at product recovery his cash flow would be all to the negative in paying for disposal without any return from sales of recovered products. The farmer producer should also be concerned with the manufacturer's profit margin because this margin largely determines the premium he will be paid for his milk. Plant management likely will be amenable to sharing profit with producers; they cannot share what they do not make. Up to this point there have been few if any studies attempting to correlate the effects of impurities, operating temperatures and conditions, and solution total solids level upon lactose crystallization in ultrafiltered whey permeates. Most studies on lactose crystallization have been performed under controlled laboratory conditions. The tendency in these experiments was to use purified lactose solutions of varying concentrations to study crystal growth. These studies have been done to observe the crystal structure, rate of formation, and effects of single impurities upon the crystal structure (5,6,7,8,9,10,11,12,13,14,18,23,24,25,29,32,33,34,36,37,38,40). However, those trials lacked in realistic relationship to actual manufacturing situations. It is necessary such types of basic study be performed for an understanding of the internal workings of the situation, but the research has not been carried far enough to reach conclusions which would be of benefit in applied industrial situations. This study was undertaken in an attempt to fill part of the gap in information on lactose crystallization as it occurs in industrial situations, by attempting to examine the effects of temperatures and solids (supersaturation) levels upon the sizes of crystals formed in ultrafiltered whey permeate solutions. This involved trying to combine the knowledge of various known effects into a single experiment and interpreting the outcome of the combined effects upon the crystal size and rate of growth to an industrially harvestable size.

Library of Congress Subject Headings



Includes bibliographical references (pages 48-50)



Number of Pages



South Dakota State University


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Dairy Science Commons