Date of Award:

1988

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Nutrition, Dietetics, and Food Sciences

Department name when degree awarded

Nutrition and Food Sciences

Advisor/Chair:

Rodney J. Brown

Abstract

Ice cream mix was fermented with yogurt cultures of Streptococcus thermophilus and Lactobacillus bulgaricus to four different pH's then frozen in a batch ice cream freezer. A consumer panel of 120 people tasted samples of strawberry flavored product with pH's of 4.4, 4.7, 5.1, and 5.4 and commercial frozen yogurt as a standard. Results from the panel were used to predict a preferred pH of 4.9. Another panel of 181 people compared product at pH 4.9 with 10, 15 and 20% strawberry flavoring. There was not a statistically significant difference among levels of flavoring.

Starter culture populations and lactase activity were monitored for one month both in yogurt and in the frozen fermented ice cream mix. Lactase activity and colony counts progressively decreased in refrigerated yogurt at 4°C during the 30-day period. In frozen fermented ice cream mix, lactase activity and colony counts decreased slightly. The fermented ice cream mix can be held frozen for more than one month with active lactase activity, and viable colony counts, but refrigerated yogurt does not have a shelf life of more than one month.

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