Document Type

Thesis - Open Access

Award Date


Degree Name

Master of Science (MS)


Agricultural and Biosystems Engineering

First Advisor

Kasiviswanathan Muthukumarappan


fortification, kidney bean, pinto bean, yogurt


Nowadays, yogurt (a nutritious fermented dairy product) is getting popular around all over the world due to beneficial action provided by bacteria present in yogurt culture. Along with that, diet plans, which are high in protein and low in fat, has become appealing for growing healthy conscious population that makes a huge shift toward plantbased protein consumption. Therefore, the main objective of this research was to study the effects of yogurt fortification with extracted protein of different beans (legumes)- pinto and kidney beans on the physio-chemical (Moisture, Fat, Protein, Ash, Total Solids Content (TSC), pH, Titratable Acidity (TA), Water Holding Capacity (WHC), and Color), microbiological, and rheological properties. The main reason for using legumes was that they are an excellent source of protein with miscellaneous applications in the food industry. Protein was extracted from the beans by following the isoelectric point precipitation method. Protein concentrate was added to the yogurt at different fortification levels of 0, 2.5, 5, 7.5, and 10% before the inoculation stage. 0% fortification represents the control yogurt sample. The fortified and control milk samples were incubated at 42±1 °C until the pH reached 4.6. The prepared control and fortified yogurt samples were stored at 5 °C and analyzed for their physio-chemical, microbiological and rheological properties over a storage period of 1, 7, 14, 21 and 28 days respectively. Physio-chemical properties were determined by standard procedure (AOAC), microbiological by total plate procedure and power law model used to describe the rheological behavior of the control and fortified yogurt. The ANOVA procedures applied on physiochemical properties of control and both pinto bean protein concentrate (PBPC) and kidney bean protein concentrate (KBPC) fortified yogurt were found to be statistically significant with p-value less than 0.05 and R2 values to be more than 0.93 for all the physiochemical properties. The protein content of KBPC, PBPC and control yogurt at 2.5 % fortification level were 6.08%, 5.87%, and 4.44% respectively. The pH of KBPC and PBPC fortified yogurt varies (pinto > kidney) from 4.57-4.12 whereas control yogurt samples vary from 4.61-4.19 during 28 days of storage. There were no significant differences obtained in color of 0 and 2.5% fortification level on day 1 for both bean types. The WHC of PBPC yogurt found to be higher as compared to the KBPC and control yogurt samples. The WHC of both bean type fortified yogurt increased with increase in the fortification level and decreased with respect to a storage period of 28 days. No significant difference has been observed in the means values of viable count between different bean types. Both the control and fortified yogurt samples have followed a shear thinning behavior (n< 1). The consistency index of fortified yogurt samples was increased significantly (p< 0.05) with the increase in the fortification level whereas the flow behavior index values decreased significantly with increase in fortification level. The obtained results showed that the kidney and pinto beans protein could be used as potential source of providing new alternative fermented dairy product with The obtained results showed that the kidney and pinto beans protein could be used as potential source of providing new alternative fermented dairy product with high protein content, no significant change in microbial properties but may affects the rheological properties of yogurt. However, on comparing PBPC and KBPC fortified yogurt, KBPC fortified yogurt was found better on the basis of protein content, total solids content, color, consistency and flow behavior index.

Library of Congress Subject Headings

Proteins in human nutrition.
Enriched foods.


Includes bibliographical references



Number of Pages



South Dakota State University


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