Effects of superheated steam processing on the functional properties of oat groat, bran and flour, and on viability of Geobacillus stearothermophilus spores

ATA alimentary toxic aleukia BA bile acids BG p-glucans CLA conjugated linoleic acid DON deoxynivalenol DSC differentialscanningcalorimetry FA fatly acids FDA Food and Drug Administration FFA free fatty acids GI gasho-intestinal HAD hot air drying HACCP hazardanalysis and critical control point HPAEC high performance anion exchange chromatography IIPSEC high performance size exclusion chromatography LDL low-density lipoprotein MALS multi angle light scattering MC moisture content NtV nivalenol RH relative humidity RTE ready to eat RVA rapid visco analysis SCFA short chain fatty acids SS superheated steam TL total lipids 1 INTR.ODUCTXON At one time oats were considered only as animal fodder and their human consumptionwas limited to areas in Scotland and Ireland (Webster 2002).Nowadays, oats are highly regarded as wholesome food beneficial to human health.Oat grain is rich in quality protein, unsaturated faffy acids, dietary fibre (especially its soluble fraction) minerals and vitamins, as well as phenolic compounds and other bioactive phytochemicals @rzikova et al. 2005; Manthey et al. 1999; Sayar et al. 2006).In human consumption, this multifunctional food is used mainly as breakfast porridge (oatmeal), in various snack forms (granola bars), and in baby foods (Hoover et al. 2003; Sayar et al. 2006).Oat products are often used as ingredients or additives in bread and cookies production or as thickeners in sauces and gravies (Bumette et aI.1992).In 1997, the US Food and Drug Administration (FDA) ruled that "diets low in saturated fat and cholesterol that include soluble fibre from oats (p- glucans) may reduce the risk of coronary heart disease" (Webster 2002).As a result of that, development of functional foods and food ingredients containing oat components has been explored (Bekers et al.2001;Brennan and Cleary 2005).Raw oat grain becomes rancid in a short period of time due to the presence of oil with high degree of unsaturation and active lipolytic en4¡mes.Uncontrolled activity of the enzymes shortens shelf life of oat products.The solution to that problem is hydro-thermal inactivation of the enzymes and this approach is commonly used in conventional processing of oats for human consumption (Liukkonen et al. 1993; Youngs 1986).The primary objective of conventional oat processing is therefore inactivation of the heat-labile lipolytic enzymes (Ganssmann and Vorwerck 1995).The secondary objectives are development of the characteristic "oatyltoasted" flavours and reduction of oat grain microbial contamination.Conventional oat processing includes conditioning with saturated (wet) steam and kiln dryitrg (Molteberg et al. 1995).The application of wet steam increases moisture content and temperature of oat grain for faster inactivation of the lipolytic enzymes.Kiln drying of the grain is therefore needed in order to bring the grain moisture content down to levels acceptable for storage.This step requires a major energy input.The kiln drying ends with a cooling step during which ambient air is drawn through the grain mass, introducing microorganisms present in the air.The kiln drying is difficult to control and not energy efficient.A potential technology for oat grain is to use superheated steam (SS) processing instead of the kiln drying.Processing with SS has been proposed over a century ago as a drying method and is often referred to as SS drying @lustondo et aL.2002;Schwartze and Brocker 2002).Superheated steam can be used to dry moist materials due to its capacity to absorb moisture as long as the SS temperature stays above the saturation point for water at a given pressure.It has been reported that SS drying rates are faster than those of hot air under certain conditions (Chow and Chung 1983; Tang and Cenkowski 2000).As a result, much lower energy consumption may be achieved when SS is used as a drying medium (Mujumdar and Huang 2007).Superheated steam drying technology has been accepted in paper, lumber, and sugar-beet industries either because of better quality of materials processed with SS or better energy effìciency compared to hot-air drying(Jensen 1992; Svensson 1985; Urbaniec and Malczewski 1997).Changes other than drying may occur in food materials exposed to SS, including changes in structure, texture, colour, starch geLatiruzation, and protein denaturation (Tang and Cenkowski 2000).Temperatures commonly used in SS processing vary between 100

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