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Journal of Microwave Power and Electromagnetic Energy, 47 (3), 2013, pp. 155-176.
A Publication of the International Microwave Power Institute
Physico-chemical Characteristics of
Microwave-dried Wheat Distillers
Grain with Solubles
Maria Rosario P. Mosqueda, Lope G. Tabil, and Venkatesh Meda
Department of Chemical and Biological Engineering, University of Saskatchewan, 57
Campus Drive, Saskatoon, SK Canada S7N 5A9
Received: June 14, 2013
Accepted: June 26, 2013
ABSTRACT
Laboratory-prepared samples of wheat distillers grain with solubles with varying
condensed distillers solubles (CDS) content were dried under varying microwave power, and
microwave convection settings using a domestic microwave oven to examine their effect on
the chemical, structural, color, flow, compression, thermal, and frictional properties of the
product, which is dried distillers grain with solubles (DDGS). As CDS level increased, protein
and ash content increased, while fat and fiber content decreased in wheat-based DDGS. Fat
content was also markedly effected by the microwave oven drying conditions. While CDS level,
microwave power or microwave convection setting, and/or their interactions significantly
effected a number of physical properties; results indicated that CDS level had a stronger
influence compared to the other factors. DDGS samples with high CDS levels were significantly
denser, finer but more differentiated in size, less flowable, and less dispersible. These also
produced denser and stronger pellets.
KEYWORDS: CDS, chemical composition, DDGS, microwave energy, physical properties, wheat
distillers grain.
INTRODUCTION
Product variability, energy-intensive drying process and reduced protein quality are
among the challenges that currently confront wheat distillers dried grain with solubles (DDGS)
production from ethanol processing plants in western Canada [University of Saskatchewan,
2011]. Several animal feed studies, for example, reported low lysine content, availability and
digestibility in wheat DDGS, despite its high crude protein content [Nyachoti et al., 2005;
Widyaratne and Zijlstra, 2007; Lan et al., 2008; Cozannet et al., 2010]. Loss of lysine, an
essential amino acid in animal diet, lowers the nutritive value of a feed ingredient [Fayle and
Gerrard, 2002] and limits the utilization of wheat DDGS as feed ingredient for monogastric
animals [Widyaratne and Zijlstra, 2007]. Also, Nuez-Ortin [2010] found significant nutrient
variability in wheat DDGS samples obtained from two Saskatchewan plants and stressed the
importance of product consistency not only for more accurate animal feed formulations but
also in improving the market prospects of wheat DDGS.
High temperature drying and the blending of condensed distillers solubles (CDS) and
wet distillers grain (WDG) were identified as among the major causes of variation in the
physico-chemical characteristics and reduced protein quality in both corn [Batal and Dale,
2006; Fastinger et al., 2006; Ileleji and Rosentrater, 2008] and wheat [Nyachoti et al., 2005;
International Microwave Power Institute
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