Food Science and Technology Department


Date of this Version

Summer 7-2014


Sabillón Galeas, L. 2014. Understanding the Factors Affecting Microbiological Quality of Wheat Milled Products: From Wheat Fields to Milling Operations. Master's Thesis, University of Nebraska.


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 Andréia Bianchini. Lincoln, Nebraska: July, 2014

Copyright (c) 2014 Luis Eduardo Sabillón Galeas


Although regarded as a low-risk commodity, wheat flour-based mixes have been implicated in several food safety incidents. The present thesis is a compilation of five scientific manuscripts on the effect of weather variation, milling steps and implementation of pre-milling interventions on the microbiological quality and safety of wheat and milled products. The first manuscript is a review of the microbiological quality and safety of wheat-based products. Despite the low water activity, wheat flour may harbor dormant but viable microorganisms, which could lead to safety concerns when flour is used to produce refrigerated dough products. The second manuscript illustrates the effect of climatic conditions on the microbiological quality of wheat, where wheat grown under higher relative humidity and higher maximum temperature may be more susceptible to lower microbiological quality. In the third manuscript, the effect of the milling steps on the microbial load of wheat milled products is reported. While the cleaning and tempering steps did not affect the initial microbial counts, the grinding process caused a redistribution and concentration of microbial contaminants into the bran and germ fractions. The fourth manuscript reports the effect of novel tempering solutions on reducing microbial load in wheat prior to milling. Results showed that tempering solutions containing organic acids and NaCl were capable of effectively reducing the microflora of wheat kernels when compared to the traditional tempering process. In the last manuscript, the combined antimicrobial effects of organic acid and NaCl during tempering and its impact on flour functionality were evaluated. The results indicated a synergistic effect between lactic acid and NaCl, which was very remarkable in reducing microbial counts. Moreover, the impact on mixing, pasting, and baking properties was minimal.

Adviser: Andréia Bianchini