Digestibility and Quality Characteristics of Sulgidduk (a Traditional Korean Rice Cake) Prepared with Malic Acid-Treated Wheat Starch

Abstract

With rising obesity rates worldwide and growing health awareness, the demand for low-calorie, blood sugar-controlling products is heightening. Particularly, research has increasingly explored the incorporation of resistant starch (RS) in dietary applications, as it does not add to calorie intake and helps regulate blood sugar levels, prevent constipation, and increase fecal volume, similar to dietary fiber. This study evaluated the quality characteristics and digestibility of malic acid-treated wheat starch (MA starch) with a high RS content for use as a rice flour substitute in Sulgidduk. MA starch was incorporated at 10-40% of the rice flour weight. Adding MA starch to Sulgidduk resulted in slight color changes, with decreased lightness and increased redness and yellowness, although structurally it remained unchanged. Higher MA levels reduced the pH and moisture content but increased sugar content and hardness. Compared to the control sample (rapidly digestible starch (RDS): 68.3%, RS: 30.3%), Sulgidduk prepared with MA starch had lower RDS (55.7%) and higher RS (42.3%) content. MA starch significantly affected RDS and RS levels, which are associated with the glycemic index, while also affecting moisture content and textural characteristics. Based on these findings, 30% substitution with MA starch (MA-30) appears to be the optimal ratio for maintaining health benefits while minimizing quality degradation. Collectively, these results highlight the potential of MA starch as a functional food ingredient and support its application in the formulation of dietary products for calorie management.

Keywords: Resistant starch; Sulgidduk; flour substitute; malic acid; rice flour; wheat starch.

Fig. 1. Appearance of Sulgidduk prepared with various proportions of malic acid-treated wheat starch (MA starch).

Control: 100% rice flour, MA-10: rice flour replaced with 10% MA starch, MA-20: rice flour replaced with 20% MA starch, MA-30: rice flour replaced with 30% MA starch, MA-40: rice flour replaced with 40% MA starch.