Food Science and Technology Department


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A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Food Science and Technology, Under the Supervision of Professor Vicki L. Schlegel. Lincoln, Nebraska: December, 2011

Copyright (c) 2012 Rebbeca M. Duar


Prebiotic carbohydrates are now added to a variety of processed foods to beneficially affect the gut microbial composition and activities. However, published data remain limited on the stability of prebiotics during food processes, such as baking, extrusion, pasteurization, high temperature heating, low pH condition, etc. As the complexity of the food matrix may also affect the ability to test for prebiotics, product specific analytical methods, including UV-vis spectroscopy, GC and HPLC, were developed and validated to monitor the stability of FOS, inulin and GOS in different types of processed food (breakfast cereal, cookie, muffin, sports drink and a nutritional bar). The results showed satisfactory linearity (r>0.9) for all the validated methods, however differences in the complexity of the ingredients were reflected in method accuracy and precision. Method precision was determined by calculating the percent relative standard deviation (% RSD) of spiked samples (n=5) below (0.5%) and above (2%) the target amount to be supplemented in the food products (1%) with results ranging from 1-39%. Methods for monitoring FOS and GOS resulted in low detection and quantitation limits allowing analysis of prebiotics of less than 1% in the presence of complex matrices. On the other hand the inulin method presented high detection and quantitation limits. Additionally, accuracy was affected by compounds present in the food matrix, which was accessed by determining the percent recoveries of spiked prebiotic in the control samples and applying corresponding correction factors to the supplemented processed foods when the accuracy was below 90% or above 110%. The chemical fate of the prebiotics was determined by applying the optimized and validated extraction and analytical method to prototype food products with 1% supplemented prebiotic. Recoveries ranged from 25-300% depending on method’s performance, complexity of the matrix and the severity of the processing effects. Finally the fate of the prebiotics in a cereal and sports drink that were prepared under various processing conditions indicated a high stability of GOS, while FOS and inulin were affected by low pH and high temperatures.

Adviser: Vicki L. Schlegel.

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