Prebiotic Food Starch Characteristics and Materialization for “Dodamssal”

다국어 초록 (Multilingual Abstract)

Resistant starch (RS), a type of prebiotic, presents various functions, such as increasing satiety, improving colon environment, blood sugar and insulin response, and reducing and maintaining weight. Most rice cultivars comprise less than 1% of RS, whereas “Dodamssal” (DDS) contains about 10% in white rice. In this study, we aimed to elucidate the starch characteristics in various rice cultivars with different amylose contents developed by the National Institute of Crop Science and enhance use of RS-containing DDS brown rice as a health-promoting low-glycemic-index (GI) food. Non-digestible starches (NDS) and native starches (NS) were isolated from four rice cultivars: Baegokchal (BOC), Ilmi (IM), Mimyeon (MM), and DDS. MM- and DDS-derived NS showed high amylose and low rapidly digestible starch contents as well as high slowly digestible starch and RS proportions. The BOC, IM, and MM starch crystals showed A-type X-ray diffractometry patterns. However, the DDS granules displayed a C-type crystallinity pattern with a predominant B-type and convex spherical shape. All the IM and BOC starches were hydrolyzed, with no remaining NDS residues. MM and DDS NDS showed longer average amylopectin chain length but lower molecular weight and viscosity than the NS. The DDS starch had the lowest digestibility and highest RS content, showing its potential to prevent obesity and hyperglycemia. Roasting conditions, which increase the RS content in DDS, were explored in the 180∼300°C and 10∼30 min ranges. We compared the intermediate-amylose ‘IM’ and high-amylose ‘Goami4’ and ‘DDS’ cultivars. The IM RS content was not significantly different before and after roasting. The Goami4 RS content was significantly higher before roasting and significantly lower at temperatures above 210°C than that of DDS (P<0.05). The starch hydrolysis index and expected GI (eGI) were higher in the following order: IM, Goami4, and DDS, regardless of the roasting treatment. The sensory evaluation for color, flavor, bitter taste, and sweetness yielded high scores for DDS at 240°C for 10 min and 210°C for 30 min. The results indicate that DDS is a suitable cultivar for low-GI powder meal preparation. Upon analyzing the roasted DDS and 60∼200 mesh-passed brown rice flour (BRF) quality characteristics, the average particle size, hydrolysis index, and eGI showed significantly lower values for DDS than for Ilpumbyeo (P<0.05). The DDS RS content was 13% regardless of standard sieve or particle size. Therefore, we concluded that DDS is a valuable health food, as it is easily ground evenly when processed into BRF, contains RS, and has a low eGI. To improve the DDS BRF quality and establish the processing protocol, we steamed rough rice (SRRD) and brown rice (SBRD) for 30 min, then dried and roasted them at 240°C for 10 min. The particle size, crystallinity, thermal properties, RS content, and BRF digestion rate were compared with those of similarly treated IM (SRRI) and single-roasted DDS (RD). In the case of SRRI and SBRD, exhibiting a high order of gelatinization degree, significant differences with large average particle size, high digestion rate, and eGI, as well as low RS content were observed (P<0.05). SRRD showed significant differences in the fine powder particle distribution range with the highest proportion, RS content, and low eGI, although the gelatinization degree increased compared with RD (P<0.05). Therefore, SRRD, with improved BRF quality, could be potentially used as a carbohydrate source for developing functional powdered food for health improvement.