Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Kenneth R. Spurgeon


Yogurt is one of the oldest and most traditional fermented dairy products. Since early times it has been an important food item of the people in the Middle East. Except for its refreshing taste and wholesomeness as a food, no special virtues were claimed for it until early in the 20th century when the bacteriologist, Elie Metchnikoff, who shared a Nobel Prize in 1908, concluded from his studies on the effect of lactic acid bacteria of the digestive tract, that yogurt arrests putrefaction in the intestinal tract and thus might be beneficial to health (55). Attempts to popularize yogurt in the United States (US) and Canada were first successful in the 1940's. In 1955, the total production of yogurt in the US was only 17,000,000 lb, whereas by l980 the production increased -to 589,000,000 lb. On a per capita basis, consumption rose from .2 lb in 1960 to 2.67 lb in 1980 (64). The future looks bright for the yogurt industry, particularly in view of the fact that per-capita consumption in the US is still far below that of most European countries; annual yogurt consumption per person in 1977 was 1.2 kg in the US compared to 14.9 kg in the Netherlands, 14.2 kg in Denmark, 12.2 kg in Switzerland, and 8.0 kg in France (103). Whey is plentiful. According to Delaney (19), approximately 16,000,000 tons of whey are produced in the US yearly. About 80% of the whey is from whole milk cheese and 20% from cottage cheese manufacture. It is estimated that just over one-half of this whey is used and the remainder is disposed as waste (6). In the middle ages, whey was utilized as a pharmaceutical drug, as a skin balm, and in cattle feed; but rarely was it used as a food for humans. As the cheese industry grew, production of an increasing volume of byproduct fluid whey, for which there was little demand, accompanied it. Strong new regulations prohibit dumping of whey into streams, rivers, and even into municipal sewerage systems because of its high biological oxidation demand (53). The dairy industry is always interested in use of new and different ingredients that are lower in cost and do not affect quality of product. A great deal of research has been aimed toward promoting proper utilization of whey; but it has not been nearly enough, arid utilization of whey remains perhaps the most serious problem facing the dairy -industry worldwide. One must therefore admire the many efforts in research and manufacturing aimed at making something consumable and marketable, if not profitable, from whey. The use of whey in yogurt and other dairy products has been limited heretofore, because of its effect on the quality of the finished product. However, in the current decade research has been done on the feasibility of replacing nonfat dry milk with dry whey in yogurt and frozen desserts. Use of lactase (e-D-galactosidase or E. C. 3. 2. 1. 23 β-D-galactoside galactohydrolase) to hydrolyze lactose, the major carbohydrate of milk, into its constituent monosaccharides glucose and galactose prior to product manufacture has received considerable attention during the past decade. Applications for the food industry are readily apparent; one application is preparation of low lactose dairy products intended for use by lactose sensitive individuals. The objectives of this research were: 1) to determine the acceptability of yogurts made with reconstituted nonfat dry milk bases, having 50 or 75% hydrolysis of the total lactose available in the mixes along with replacement of 25 or 50% of the nonfat dry milk content with sweet dry whey; 2) to ascertain economy achieved by use of dry whey, which costs less than nonfat dry milk, and use of less sugar in hydrolyzed batches since the products of lactose hydrolysis are sweeter than lactose per se; and 3) to ascertain whether enzymatic hydrolysis of lactose to its component simple sugars would make possible the use of greater percentages of dry whey in yogurt formulas without adverse effects on flavor and/or other properties of the yogurt.

Library of Congress Subject Headings



Includes bibliographical references (pages 76-84)



Number of Pages



South Dakota State University


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Dairy Science Commons