應用高抗性米穀粉於土司之配方開發 及其物化與消化性質之分析

Abstract

白土司作為常見早餐與主食的選擇，但其高升糖指數(glycemic index, GI)對於健康造成不利影響。由於代謝性疾病日益普遍與消費者健康意識提升，本研究旨在開發具較低升糖指數之麵包(土司)。碎米為碾米過程中產生之副產物，經酵素去支化(debranching)與濕熱處理(heat-moisture treatment)改質，可進一步提升其抗性澱粉(resistant starch, RS)含量，然而，其應用於烘焙製品時，常伴隨質地不良與適口性差等問題。本研究以高抗性米穀粉為原料，針對麵包配方開發、成品質地、物化性質與體外消化特性進行探討。研究結果顯示，透過製程優化可將去支穀粉回收率由54.37%提升至82.99%，並且乾燥方式的不同顯著影響粉體體化消化性質。此外，添加高抗性米穀粉作為麵包原料，可藉水分調整有效改善麵包結構與性質。在去支米麵包(DB)組別，加熱處理的有無對於麵包性質並無顯著影響，但經由去支-濕熱處理穀粉中，因澱粉結晶程度提升，藉由預加熱處理後，使澱粉膨潤可增加麵包體積與適口性質，顯示原料粉類的不同可以經由加工製程改善使烘焙性質提升。將實驗最佳組別進行儲藏性與體外消化性質分析，去支-濕熱米麵包(DHB)隨著儲藏時間增加硬度上升緩慢，甚至低於對照組白土司，顯示其延緩澱粉老化的能力。在消化性方面，以白土司作為標準品進行探討，DB與DHB組體外水解指數分別降至81.85%和77.98%，在30%取代比例下，其GI值顯著下降，使麵包由高GI降為中GI等級，且RS含量明顯提升。本研究成功利用預加熱處理與配方調整開發兼具良好適口性與健康功能之麵包，提供未來產品開發新方向。

White bread (WB), a staple food with widespread consumption, is associated with a high glycemic response, which may contribute to adverse metabolic outcomes. In light of the increasing prevalence of metabolic disorders, this study aimed to develop a novel bread formulation with a reduced glycemic index by incorporating high-resistant starch rice flour. Broken rice—a byproduct of rice milling—underwent enzymatic debranching followed by temperature-cycled heat-moisture treatment (HMT) to enhance its resistant starch (RS) content. Incorporating this modified flour into bread was systematically evaluated for its effects on dough hydration, bread texture, physicochemical properties, and in vitro starch digestibility. Results indicated that process improvement increased the recovery rate of debranched rice flour from 54.37% to 82.99%, and different drying methods significantly affected the flour's physicochemical and digestibility characteristics. Formulation adjustments, particularly in water content, were critical to achieving desirable bread texture due to the altered hydration properties of the high-RS flour. Pre-gelatinization treatment effectively enhanced starch swelling and matrix integration, improving bread volume and palatability. Storage tests showed that debranched-HMT rice flour partially substituted bread exhibited slower hardness increase and suppressed starch retrogradation, suggesting extended shelf life. HMT contributed to increased starch crystallinity, thereby reducing enzymatic digestibility. At a 30% substitution level, the hydrolysis index (HI) of breads made with debranched rice flour and debranched-HMT rice flour decreased to 81.85% and 77.98%, respectively, shifting their predicted glycemic index (eGI) classification from high to medium. Additionally, RS content in the final product significantly increased. These findings suggest that high-resistant debranched rice flour is a promising functional ingredient for developing bakery products with improved metabolic health profiles and enhanced storage stability.