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Thesis - University Access Only
Master of Science (MS)
Lloyd E. Metzger
Nonfat yogurt is a popular fermented product available in various forms. In the US, the Code of Federal Regulations (CFR) requires >8.25% milk solids in the yogurt base. NDM is a common ingredient utilized to provide milk solids in yogurt produced in the US. However, in International markets, Skim Milk Powder (SMP), Milk Protein Concentrate (MPC), and De-Proteinized Whey (DPW) are also utilized in yogurt formulations. The protein content, Total Solids (TS), source of milk protein, and seasonal variation in yogurt formulations may have an impact on the functionality of yogurt. Additionally, physicochemical changes during storage of powders can result in variation of the functional properties of powders as well as of the product in which they are used. The first objective of this study was to evaluate the effects of Milk Solids Not Fat (MSNF) based fortification of yogurt formulations with various milk powders (SMP, NDM, MPC40, and MPC70) on the functionality of nonfat stirred yogurts. Required amounts of powder were added to produce yogurts containing 8.5% MSNF. The second objective of this study was to evaluate the effects of storage of various milk powders (SMP, NFDM, MPC40, and MPC70) on their functional properties and on the functionality of nonfat yogurts at three different protein and TS levels. Three different lots of SMP, NDM, MPC40 and MPC70 were collected from US manufacturers and each lot was divided into 3 portions. A portion was analyzed after 3, 9, and 15 months of storage at 25°C. At each storage time, yogurt formulations with %protein/%TS of 4/12.5, 4.5/13.5 and 505.5 were produced from each lot of SMP, NDM, MPC40, and MPC70. The third objective of this study was to evaluate the effects of seasonal variation of powder manufacture (SMP and NDM) on their functional properties and on the functionality of nonfat yogurt at three different %protein/% TS ratios ( 4/12.5, 4.5/13.5 and 5/15.5). Skim milk powder and NDM were collected from US manufacturers during summer (May'09 - August'09) and winter (Nov'09- Feb' 10) season for yogurt manufacture. A Rapid Visco Analyzer (RVA) method was utilized to produce yogurt for all objectives. At each storage time, yogurt formulations with three different · %protein/%TS (4/12.5, 4.5/13.5 and 5/15.5) were produced from each lot of SMP, NDM, MPC40, and MPC70. Varying amount of DPW was included to standardize the protein and TS content. Functional properties such as solubility, Emulsification Ability Index (EAI), foaming, and hydrophobicity of each powder lot was evaluated at 3, 9, and l 5months of storage. The data were analyzed by split plot design using PROC Mixed in SAS. Functional properties of yogurts (standardized at 8.5% MSNF) improved with an increase in the protein content in the formulation. Powders storage time did not have a significant effect (p>0.05) on the functional properties of yogurts fortified with NDM, MPC40, and MPC70 at all protein/TS ratio (protein:TS). Viscosity of both MPC40 and MPC70 yogurts was significantly (p<0.05) lower than SMP and NDM yogurts at each protein:TS. Syneresis of SMP yogurts was significantly higher (p<0.05) than NDM yogurts at each protein:TS of yogurt. Storage time had a significant effect (p<0.05) on solubility and foaming properties where solubility of MPC70 and foam overrun of SMP, MPC40, and MPC70 decreased significantly (p<0.05) with an increase in storage time of the powders. Emulsification properties of MPC70 were significantly higher (p<0.05) than SMP, NDM, and MPC40. Additionally, yogurts fortified with winter season powders showed improved functional properties as compared to yogurts fortified with summer season powders. Seasonal variation in powder manufacture did not have a significant (p>0.05) effect on their functional properties such as solubility, EAI and hydrophobicity. In conclusion, the storage of milk powders has an impact on their functional properties but has a minimal influence on the functional properties of nonfat yogurt, whereas the use of MPC had a substantial impact on the functionality of nonfat yogurt. Furthermore, the season of powder manufacture also has an impact on the functional properties of yogurts.
Library of Congress Subject Headings
Proteins in human nutrition
Includes bibliographical references (pages 69-93)
Number of Pages
South Dakota State University
In Copyright - Educational Use Permitted
Shah, Kartik, "Impact of Protein Content, Total Solids, Protein Source, and Storage Time on the Functionality of Nonfat Stirred Yogurt" (2014). Electronic Theses and Dissertations. 1618.