Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department

Dairy Science

First Advisor

Sanjeev Anand

Abstract

Studies were conducted to determine the effectiveness of ultrasonication and hydrodynamic cavitation, in a continuous mode, alone and in combination with thermal treatments, on heat resistant aerobic sporeformers and spores in skim milk, and skim milk concentrate. The first study was conducted to investigate the effectiveness of a continuous ultrasonication process to reduce thermoduric Bacillus coagulans cells in skim milk. A 25% reduction was obtained by lab pasteurization alone, whereas ultrasonication alone resulted in an inactivation of 92% after 12 passes (80 sec exposure time per pass). Ultrasonication when combined with pasteurization resulted in further increased inactivation to 99.98%. It can thus be concluded that a continuous ultrasonication process followed by pasteurization is effective to inactivate thermoduric Bacillus coagulans cells. The second study was conducted to investigate the effectiveness of a continuous hydrodynamic cavitation process to reduce thermoduric spore forming bacilli in skim milk. The study also evaluated its impact on skim milk concentrate, and the final sporeformer counts of skim milk powder, in a simulated pilot scale skim milk manufacturing process. The results revealed that 6 pass cavitation effect alone and in combination with pasteurization was very effective in inactivating thermally resistant vegetative cells of Bacillus coagulans by 99.963% and 99.996% respectively. A 99.66% reduction of Bacillus coagulans cells was found in non-fat dry milk when made from cavitated milk, and upto a 99.65% reduction of total count was found in skim milk concentrate after cavitation treatment. The third study was conducted to investigate the effectiveness of a continuous hydrodynamic cavitation process to reduce thermoduric spores of Bacillus licheniformis in skim milk. Heat treatment alone did not result in any inactivation of the spores. Cavitation with holding at 30ºC for 3 hours and heating at 85°C for 15 min resulted in an inactivation of 97.59%. Another treatment with preheating at 65°C along with cavitation and holding at 30ºC for 3 hours followed by heat treatment at 80°C for 1 min resulted in inactivation of 99.29%. Overall, both ultrasonication and hydrodynamic cavitation when combined with heat treatment were found more effective in reduction of thermally resistant bacilli in skim milk.

Library of Congress Subject Headings

Skim milk -- Microbiology

Bacterial spores

Milk contamination

Ultrasonic waves -- Industrial applications

Cavitation

Milk -- Heat treatment

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

176

Publisher

South Dakota State University

Rights

Copyright © 2016 Dikshi Bawa

Included in

Dairy Science Commons

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