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Effects of RS4 type resistant corn starch on the quality characteristics of cookies were investigated by physicochemical, instrumental and sensory evaluation. The resistant starch was made by cross-linking of corn starch as following; corn starch slurry was annealed at pH 2.0 and 50℃ for 2 h followed by the cross-linking reaction. The cross-linking reaction was performed at 50℃ for 12 h in the presence of 1.2%/st.ds NaOH, 10%/st.ds sodium sulfate and 10%/st.ds of sodium trimetaphosphate (STMP)/sodium tripolyphosphate (STPP) mixture. Dietary fiber content of the resistant starch was estimated to be 73.8% by the AOAC method. For quality characteristics, dough pH decreased with the increase of the resistant starch content and spread factor decreased a little at 20% of the resistant starch. The moisture content and L value of cookies increased with the increase of the resistant starch content. However, the hardness and fracturability decreased with the increase of the resistant starch content. In the sensory evaluation, no significant differences were observed between the two cookies with or without the resistant starch. The results of this study suggest that the RS4 type resistant corn starch can be a good ingredient to increase dietary fiber content in cookies without changes of their qualities.

We evaluated the immunomodulatory activity of type-4 resistant starch (RS) in mesenteric lymph nodes (MLNs) using a rat model. Sixteen male Sprague-Dawley rats were fed either a cellulose diet or an RS diet (RSD) for 4 weeks. Serum immunoglobulin A levels, as well as the CD4(+) T cell population and the ratio of CD4(+)/CD8(+) T cells in the MLNs of rats, were significantly elevated by replacing cellulose with RS in the diet. The survival rate of concanavalin A (Con A)-stimulated MLN lymphocytes and interleukin-4 secretion from the Con A-stimulated MLN lymphocytes were significantly increased in rats fed RSD. These results indicate that type-4 RS might ameliorate allergic inflammation in the MLNs of rats through an increased CD4(+) T cell population and enhanced differentiation of MLN lymphocytes into type-2 T cells.

The optimum annealing conditions of corn starch slurry were studied for RS4 type resistant starch production by phosphorylated cross-linking. When a corn starch slurry was cross-linked by using phosphate salts (STMP/STPP mixture) in the presence of 0.9%, 1.2% and 1.5% NaOH/st.ds, a high concentration of NaOH resulted in a rapid increase of the RS contents at the early reaction stage. However, similar RS contents were obtained after 12 h of cross-linking regardless of NaOH concentrations. The annealing treatment was conducted under various conditions such as pH between 2-10, temperature 40-60℃, time 0-14 h followed by phosphorylated cross-linking. The lower slurry pH was for the annealing treatment, the higher RS contents were obtained after cross-linking. When the slurry annealed for various period of time and temperature, a maximal amount of RS was formed after 2 h of annealing at 50℃ of annealing temperature of the starch slurry (pH 2.0). Therefore, an optimal annealing conditions at pH 2.0 and 50℃ for 2 h were proposed under the cross-linking conditions of sodium sulfate 10%/st.ds, NaOH 1.2%/st.ds and 12 h of the reaction time. The RS contents were linearly increased with the increase of phosphate salt addition. The RS4 prepared under the optimal conditions contained RS 72.3% and its phosphorus content was 0.36%/st.ds, which was below the limit (0.4%/st.