Pressurized water above its boiling point, i.e., subcritical water, is an environmental benign “green” solvent amenable to producing extracts and hydrolyzates from agricultural feed stocks for food and energy utilization.  We summarize in this presentation of over  20 years of research in the application of this medium as applied to lipid- and polysaccharide-containing  substrates using temperatures in the range of 100- 300 C.  Using temperatures from 100-180 C, extracts have been produced from a number of materials such as fruit/berry pomaces, herbal botanicals, and essential oils in less than 20 minute extraction times.  Increase of the water temperature to between 200-300 C results in an increase in the non-polar solvent characteristics of subcritical water assuring increasing miscibility of the components in switchgrass and corn stover (polysaccharides) as well as increasing levels of triglycerides from seed oils such as soybean and coconut oils. In these latter cases, the high temperature water medium under appropriate requisite temperatures is acting as both an extraction-reaction medium particularly for the depolymerization of polyphenols- and cellulose or hemicellulose-containing matrices, or hydrolysis to fatty acids in the case lipid containing moieties. Several methods for separating the extraction-reaction products from the aqueous medium will be cited including drying, precipitation, and membrane-based concentration.   Efficient use of water in these processes will be discussed with respect to processing optimization and required thermal input.  Finally, cost of manufacturing (COM) criteria will be cited to justify the use of subcritical water for the above processes.

Application of subcritical water to the sustainable production of agricultural crops and processing by-products

255th National Meeting (2018)

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