Degree Type


Date of Award


Degree Name

Master of Science


Agricultural and Biosystems Engineering


Agricultural and Biosystems Engineering

First Advisor

Kurt Rosentrater


Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as fats, proteins, vitamins, or minerals. Animal-based food products play a significant role in the current U.S. diet. In 2003, the total meat consumption per capita was 90.5 kg/year. Since the U.S. has a high consumption of animal-based food products, the animal feed ingredients are fundamentally important. The ingredients can affect not only the quality of the animal-based food products, but also the potential human health.

The U.S. is the largest producer of animal feed in the world. Feed ingredients might include grains, milling byproducts, added vitamins, minerals, fats/oils, and other nutritional and energy sources. And kinds of feed ingredients are produced to use, like DDGS and soybean meal. Recently, some co-products of energy production, like DDGS are used as feed ingredient worldwide. This kind of co-product is nutrient rich and meets the requirement of animal feed nutrition. Since these feed ingredients are used worldwide, they must be transported a long distance to some domestic and international market. And sometimes they are stored for a long time before be used. So during transportation and storage, ingredients often became restricted. This is a major problem that can affect the quality of ingredients. These issue most likely results from many factors, including ingredients’ moisture content, particle size, temperature and relative humidity of air or pressure.

A gluten-free diet excludes gluten protein. An increasing number of people are choosing gluten-free diets for either medical or personal reasons. The production of gluten-free snack foods has great potential. One method of processing that can be used to create gluten-free foods is extrusion. Extrusion is defined as a process where ingredients are pushed through a die of desirable shape. This process has been used in food, feed, and biomass. In food applications, extrusion processing has become an increasingly important manufacturing method.

The first part of this study was to investigate potential factors affecting flowability of feed ingredients, as well as examines the effect of three moisture content levels (10, 20 and 30% db) on the resulting physical and flow properties of feed ingredients. Certain amounts of water were added to adjust moisture content of ingredients and Carr indices were used to quantify the flowability of each ingredient. The results showed that moisture content had significant effects on physical and flow properties. According to Carr indices, flowability generally declined with increased moisture content. Using these, the best condition can be found for transportation and storage to maintain the good quality for ingredients when they are used.

The second part of this study was to test the extrudate properties for three gluten-free grains (millet, sorghum and teff) at two different moisture content levels (30%, 40% d.b.). Additionally, both raw grain and flours were tested prior to processing. Following extrusion, the bulk density, water activity, unit density, expansion ratio, and color were evaluated. It was found that initial grain condition (raw vs flour) and initial moisture content greatly impact extrudate physical properties. The most desirable moisture content and grain condition was 40% and flour.


Copyright Owner

Xin Jiang



File Format


File Size

102 pages