Nutritional and Microstructural Responses in Cereal Grains to Heat-Related Processing Methods
Cereal grains share many common traits, but they also have different internal structures, nutrient values, degradation kinetics and digestion features. Heat treatments are commonly used in the feed industry. It is known that heat is able to change the nutrient values of the feed but the effect could be equivocal. In order to understand the effects of heat processing on internal structure and nutrient availability of cereal grains, two batches of wheat, triticale and corn were divided into three groups (control/raw (unheated), dry heating and moist heating) and processed at 121 °C for 80 min. Basic chemical analysis and in situ, in vitro assays were conducted and CNCPS, DVE/OEB and NRC-2001 models were used to determine the nutrient availability of the grains. In addition, two mid-IR molecular spectroscopy techniques (Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) and Synchrotron Radiation Infrared Microspectroscopy (SR-IMS)) were used to gain an insight into the heat-induced changes in the functional groups. Significant (P<0.05) differences were found between the cereal grains in their nutritional availabilities, including their chemical characteristics, protein and carbohydrate fractions, energy values, the ruminal degradation kinetics, hourly effective rumen degradation ratios, potential N-to-energy synchronization, and intestinal digestion of cereal grains. Compared to dry heating, moist heating had more impact on altering the nutrient profiles and showed the potential to increase the nutrient availability of wheat and triticale for dairy cattle. Significant differences (P<0.01) were detected between different feeds and heat treatment groups by using the ATR-FTIR technique. Results were found in consistency with the conventional chemical and animal studies mentioned above despite when using the SR-IMS technique. Significant (P<0.05) correlations were detected between some structure spectral characteristics and nutrient digestion traits. In conclusion, the moist heating had more profound impact than the dry heating in increasing nutrient supplies to ruminants in wheat and triticale. The heat-induced effects found in corn were less positive. The ATR-FTIR technique could detect the internal structural changes in cereal grains, while the sensitivity and accuracy of the SR-IMS technique were not proved in this study.
cereal grains, heat processing, mid-IR technique
Master of Science (M.Sc.)
Agricultural and Bioresource Engineering