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Ashish Pandit

Document Type

Thesis - University Access Only

Award Date

2008

Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Sanjeev K. Anand

Abstract

Conjugated linoleic acid (CLA) is known to possess several health benefits including anticarcinogenicity and aiding in weight loss. Dairy products are considered a source of CLA but fall short of the recommended intake of about 3.0g per day for any health benefits. Increasing CLA level in dairy products could thus help bridge the gap between daily CLA requirement and dietary intake that is about 200mg/day. Direct supplementation and ruminant diet manipulation has been tried to enhance CLA levels in milk. The present investigation was undertaken to evaluate another approach to utilize CLA producing lactic acid bacteria (LAB) for the manufacture of Cheddar cheese with enhanced CLA levels obtained by natural fermentation. The objectives were to isolate and screen LAB from various sources for CLA production, determine the suitability of highest CLA producing LAB for cheese making, and use of these LAB in Cheddar cheese making, either as starters or adjunct cultures. A total of 155 cultures of LAB from three sources were screened for CLA production. Of the 18 CLA positive cultures, the cheese isolate 4b (Lactococcus lactis) produced highest (1.12 g/1 00g FA) CLA that was then evaluated as a starter. Another cheese isolate 1 la (Lactobacillus sp.) produced 0.63g CLA/1 00g FA that was then evaluated as an adjunct culture. Prior to actual cheese making trials, these cultures in combination with another CLA positive Lactobacillus helveticus (ATCC 15807) were evaluated for their suitability to manufacture Cheddar cheese by cheese slurry method for a short ripening period of 5 days at 37°C. Cheese slurries were inoculated with different culture combinations and evaluated for CLA production, pH, bacterial counts on Ml 7 and MRS, and free fatty acids. The results were compared with CLA negative commercial direct vat starter (DVS) obtained from Chr Hansen. Cheese isolate 4b produced highest CLA (1.1 0g/1 00g FA) in cheese slurry and had g9od characteristics to be used as a cheese starter. Similarly, another CLA producing Lactobacillus helveticus culture was found to be suitable as an adjunct culture. On the basis of cheese slurry experiments, the 4 treatments employed for cheese making were; Control DVS (CLA negative), cheese isolate 4b (highest CLA producing culture), DVS (CLA negative) combined with Lb. helveticus (CLA positive), and CI 4b combined with Lb. helveticus. Three batches of Cheddar cheese were manufactured for each treatment, using a completely randomized block design. Cheeses were evaluated at 0, 3 and 6 months intervals during the ripening period for CLA content, pH, functionality, sensory evaluation, bacterial counts on Ml 7 and MRS, and proteolysis. The control cheeses made with CLA negative starter had 0.63g CLA/l00g FA (day 1), compared to which, the CLA content could be enhanced from 0.85g/100g FA (dayl) to 0.98g/100g FA (6 months) by the application of CLA producing LAB. There was no difference in the chemical composition of cheeses across all treatments. Due to higher acid production, the pH of cheeses made with CLA producing LAB was lower than the control. On the other hand, proteolysis (water soluble nitrogen and trichloro acetic acid soluble nitrogen) was higher it) treatment cheeses than the control cheeses. Treatment cheeses had lesser (P≤0.05) free oil and meltability than the control cheeses. The texture of treatment cheeses changed during the ripening period (1-3 months) and was comparable to the control cheeses at the end of ripening study (6 months). Bacterial counts on M 17 and MRS agar were higher (P≤0.05) in treatment cheeses, as compared to the control, throughout the study. Treatment cheeses also had more Cheddar flavor intensity, and a high acceptable score without any objectionable flavor. Our study has demonstrated a substantial increase in CLA content in Cheddar cheese by the use of lactic cultures without any added substrate to milk. With some further work on optimization of culture combinations with commercial DVS, this process can find significant application in dairy industry for developing Cheddar cheese with enhanced CLA contents.

Library of Congress Subject Headings

Cheddar cheese
Linoleic acid
Lactic and bacteria

Description

Includes bibliographical references (pages 54-68)

Format

application/pdf

Number of Pages

124

Publisher

South Dakota State University

Rights

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

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