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Flow and dynamic rheological properties of hot thickened soups for consumption by the elderly people with swallowing difficulty (dysphagia) were investigated at a serving temperature of 60°C. In this study, sea mustard soup (SMS) and dried pollock soup (DPS), which have been widely known as favorable hot soups provided in a domestic hospitals and nursing homes for dysphagic patients, were thickened with four commercial xanthan gum (XG)-based food thickeners (coded A~D) marketed in Korea. Thickened soups prepared with different thickeners showed high shear-thinning flow behaviors (n=0.15~0.21). Apparent viscosity (ηa,50), consistency index (K), storage modulus (G′), and loss modulus (G″) demonstrated differences in rheological behaviors between the XG-based thickeners. The magnitudes of G′ were much higher than those of G″ over the entire range of frequency (ω) with the high dependence on ω, showing the rheological behavior similar to a weak gel. In general, all rheological parameter values of thickened DPS samples were higher when compared to the thickened SMS samples. These results indicate that flow and dynamic rheological properties of hot thickened soups containing commercial XG-based thickeners are strongly dependent on the type of thickener and soup.

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D-ribose, a five-carbon sugar, is used as a key intermediate for the production of various biomaterials, such as riboflavin and inosine monophosphate. A high D-ribose-producing Bacillus subtilis SPK1 strain was constructed by the chemical mutation of the transketolase-deficient strain, B. subtilis JY1. Batch fermentation of B. subtilis SPK1 with 20 g l(-1) xylose and 20 g l(-1) glucose resulted in 4.78 g l(-1) dry cell mass, 23.0 g l(-1) D-ribose concentration, and 0.72 g l(-1) h(-1) productivity, corresponding to a 1.5- to 1.7-fold increase when compared with values for the parental strain. A late-exponential phase was chosen as the best point for switching to a fed-batch process. Optimized fed-batch fermentation of B. subtilis SPK1, feeding a mixture of 200 g l(-1) xylose and 50 g l(-1) glucose after the late-exponential phase reduced the residual xylose and glucose concentrations to less than 7.0 g l(-1) and gave the best results of 46.6 g l(-1) D-ribose concentration and 0.88 g l(-1) h(-1) productivity which were 2.0- and 1.2-fold higher than the corresponding values in a simple batch fermentation.