报 告 人：Keshun Liu 研究员
Keshun Liu Ph.D. is a Research Chemist with the United States Department of Agriculture, Agricultural Research Service (USDA-ARS), where he manages a Grain Chemistry and Utilization Laboratory. His expertise is in chemistry, processing, and value-added utilization of grains, oilseeds (soybeans), legumes and their co-products. Dr. Liu received his B.S. degree in horticulture from Anhui Agricultural University in 1982, and for the next two years he enrolled in South China Agricultural University as a postgraduate study abroad under the Ministry of Education. In 1986 and 1989, he received his M.S. and Ph.D. degrees in Food Science from Michigan State University (USA), respectively, and did post-doctoral work at Coca-Cola Co. and University of Georgia (USA) thereafter. Prior to joining USDA-ARS, he was employed at Monsanto Co. and University of Missouri. Thus, he has 35 years of research experience at academic institutions, private industry and governmental agency. Over the years, Dr. Liu authored or co-authored more than 130 publications, organized or co-organized 6 international conferences and 47 symposia for scientific meetings and gave more than 100 technical presentations to domestic and international audiences. In addition, he wrote, edited or co-edited four English reference books, including two books on soybeans (which were both translated in Chinese and published in China), one on distillers’ grains and one on Asian foods. He is the recipient of American Oil Chemists Society Fellow (2011) and Institute of Food Technologists Fellow (2014) for his outstanding achievements.
Incorporating plant proteins into food or feed products by partial or full replacement of animal proteins is becoming important for human health, environmental protection, and sustainability. Extrusion has played an important role in achieving this noble goal. A proper extrusion process can impart a structured or fibrous texture to plant proteins and transform them into products with special features. Although extrusion processes vary greatly, they can be categorized into low-moisture and high moisture extrusion. During low-moisture extrusion, protein products are thermo-mechanically processed through an extruder under a moisture level of 15-45%. Upon exiting from a die, extrudates are expanded and structured. After drying, they become commercially known products, texturized vegetable proteins, which have been extensively used as fillers (also known as meat extenders) in processed meats. In contrast, high moisture extrusion features use of a twin-screw extruder with a cooling die. Protein materials are processed under 45-75% moisture levels. The extrudates do not expand, have fibrous structures, and thus more resemble muscle meat. During low or high moisture extrusion, many complex physicochemical reactions occur, and numerous parameters are involved, making it difficult to develop a proper extrusion process. Furthermore, controversy exists in the literature over the relative importance between the disulfide bond and non-covalent bonds and formation of other covalent bonds. Regardless, as new innovative meat analogs are fast entering markets, there is renewed interest in extrusion, and it is becoming the most important processing technology for expanding plant protein utilization. The presentation will also include a brief introduction of the USDA research branch (Agricultural Research Service) and updates of recent research at Liu’s lab.