Document Type

Thesis - Open Access

Award Date

1967

Degree Name

Master of Science (MS)

Department

Dairy Science

Abstract

A dicarbonyl compound, 2, 3-butanedione, commonly referred to as diacetyl or biacetyl, is considered by many to be-an important flavor constituent of butter and butter cultures. Milk fat has no natural diacetyl content and in the past the diacetyl found in butter resulted from bacterial fermentation of the cream before churning. In recent years commercial lactic cultures have been used, which are added to the fat granules before ''working" of the butter. Bacterial cultures used by the dairy industry generally consist of a mixture of two streptococcus types. A homofermentative type produces primarily lactic acid from the lactose of milk. In butter and cheese cultures, these bacteria are generally of the species Streptococcus lactis or Streptococcus cremoris. The second type encountered is heterofermentative and produces volatile acids, carbon dioxide, acetylmethylcarbinol and diacetyl as the end products of the fermentation of lactose and citric acid. These bacteria are usually classified in the genus Leuconostoc and are considered to be either Leuconostoc citrovorum or Leuconostoc dextranicum. Since these organisms produce very little acid in milk, they are grown in association with the lactic acid producing organisms because the production of diacetyl occurs at a pH lower than that of fresh milk. The selection of the more desirable organisms and maintenance of a desirable ratio between the lactic acid producing and the flavor producing organisms is done with some difficulty. This has resulted in a lack of uniformity of flavor when such .cultures are added to butter during manufacture. Failure to maintain a consistent level of flavor from cultures in butter has made the practice of adding such cultures to butter almost non-existent in the United States. In the past, especially in the 1930's, some work was done using selected strains of Leuconostoc in cream and acidifying with various acidulants prior to churning the butter. This practice required much time and equipment to incubate large lots of cream inoculated with these organisms. This practice was not economically feasible then and would not be feasible today with present-day high-volume plants and the increasing accent on time-saving production methods. This practice also led to many flavor defects because of poor control of the fermentation and low serum pH values in the butter, which gave undesirable flavor defects in salted butter during storage. The purpose of the research in this paper was to modify the Prill and Hammer (24) method for the determination of diacetyl so that six analyses could be carried out on one apparatus. Some of the factors which influence the production of diacetyl by pure strains of diacetyl producing organisms were investigated.

Library of Congress Subject Headings

Butter -- Analysis
Lactococcus lactis

Description

Includes bibliographical references (pages 58-60)

Format

application/pdf

Number of Pages

67

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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