Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science


Sweet dry whey was used to replace 25% and 50% of nonfat dry milk solids in ice cream mix. Forty-five batches experimental and control lots of vanilla ice cream were manufactured. A commercial lactase was used to hydrolyze lactose to over 90% conversion and the lactase was inactivated after hydrolysis. The extent of lactose hydrolysis in the mix was adjusted to 50% or 75% by blending non-hydrolyzed nonfat dry milk and whey solids with hydrolyzed preparations. Extra sweetness of the conversion products permitted reduction of sucrose by 6.25% and 12.5%, respectively, in the 50% and 75% hydrolyzed lactose ice cream mixes. Total solids of the hydrolyzed ice cream mixes were kept constant by adding nonfat dry milk and whey solids in lieu of the sucrose omitted. Each individual mix was pasteurized at 11°c for 30 minutes, homogenized, aged, frozen in a batch freezer, packaged in 1.8 liter packages, and stored at -10°c after hardening at -29°C. Sensory evaluations of flavor and body and texture were made after 24 hours of hardening, 7 days of storing, and at monthly intervals for 5 consecutive months. There appeared to be no differences in sensory qualities between control, whey containing, and hydrolyzed lactose batches. The non-hydrolyzed whey batches had coarseness/icy criticism after 4 months of storage. Freezing point determination, compositional analyses, and other laboratory tests were carried out for the overall evaluation of the physical and chemical properties of the manufactured ice cream. There were significant differences in freezing points of control and the experimental batches. The protein percent varied from 3.76 to 4.24% in the 25% whey and 3.08 to 3.45% in the 50% whey batches. The highest ash content in 75% hydrolyzed lactose batches with whey supplying 50% of the milk solids-not-fat was 1.24% in comparison to 1.02% in the control with no hydrolysis. Approximate cost analysis showed that the savings from the use of less sucrose and cheaper ingredients compensated for the enzyme cost in the hydrolyzed lactose whey-containing batches. Thus, the results indicated lactose hydrolysis permits usage of relatively high whey solid contents in ice cream, thereby reducing costs whilst obviating problems of lactose intolerance and sandiness defect.

Library of Congress Subject Headings

Ice cream. ices. etc.


Includes bibliographical references (pages 89-97)



Number of Pages



South Dakota State University


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Dairy Science Commons