臺灣高直鏈澱粉玉米之理化性質及其應用

Abstract

本研究共分為三大部分，第一部分在於探討臺灣高直鏈玉米 (Taiwanese high amylose corn, THAMC)澱粉之理化性質及消化性質，並與市售Hylon V、Hylon VII及Hi-maize® 260比較其差異，及探討THAMC全穀粉之理化性質、機能性成分及消化性質，並與市售硬質玉米全穀粉比較其差異。結果顯示，第一批及第二批臺灣高直鏈玉米澱粉的直鏈澱粉含量(79.33%及77.29%)較市售Hylon V (57.03%)、Hylon VII (68.27%)及Hi-maize® 260 (66.69%)為高。，由示差掃描熱分析儀 (differential scanning calorimetry, DSC) 測得THAMC澱粉在84-108°C處有一吸熱峰，其熱焓值達2.73-3.21 J/g，推測THAMC澱粉因直鏈澱粉含量高及bound lipid含量較一般玉米澱粉高，可證實樣品中存在有直鏈澱粉-脂質複合物。膨潤力及溶解度試驗結果顯示，高直鏈玉米澱粉在95°C時膨潤力及溶解度顯著比一般玉米澱粉低，此乃因前者之糊化溫度高達98.59°C (DSC測定結果)。快速糊液黏度測定儀 (Rapid Viscosity Analyser, RVA)測定結果顯示，高直鏈玉米澱粉糊液(14%)之黏度雖較Hi-maize高，但其整體黏度值仍遠低於Hylon VII，推測此與前者有較高的直鏈澱粉含量及高的糊化溫度有關。由澱粉體外消化試驗及推估升糖指數(estimated glycemic index, eGI)試驗結果得知，臺灣高直鏈玉米澱粉的抗性澱粉含量(58.92-59.60%)較市售Hylon V (44.18%)及Hylon VII (45.46%)為高，且前者之eGI (65.01-67.34)較後者為低(69.50及70.93)，其中又以Hi-maize® 260的 eGI值(59.37)為最低。全穀粉的部分，由千粒重的分析結果得知，THAMC籽粒千粒重(167.46-220.61 g)遠低於市售硬質玉米籽粒(404.13 g)，進而推測THAMC籽粒澱粉充實度較市售硬質玉米籽粒高，其胚芽及種皮的比例相對提高，導致THAMC籽粒的總澱粉含量較低，粗蛋白、粗脂肪、灰分、總黃色色素、葉黃素、玉米黃素以及總酚類化合物含量則較市售玉米籽粒為高。由澱粉體外消化及推估升糖指數實驗結果得知，THAMC全穀粉的抗性澱粉含量(31.51-34.31%)較市售玉米(27.67%)及其輾磨製品(17.72-24.76)為高，且推估升糖指數較低(59.23-60.60)。第二部分則以THAMC全穀粉或澱粉為原料，部分取代麵粉製成麵包和戚風蛋糕，探討其理化性質及澱粉消化性質，結果顯示，取代10%及20%麵粉的麵包及蛋糕之eGI較控制組(未取代者)低，且抗性澱粉含量隨著取代量的增加而增加。第三部分則是探討濕熱處理(100°C/24 h)對THAMC澱粉理化性質及澱粉消化性質之影響並與市售Hi-maize® 260性質進行比較。結果顯示，經濕熱處理之THAMC澱粉之糊液黏度並沒有顯著變化，但由DSC測得其在121-157°C有一吸熱峰，推測此為直鏈澱粉雙股螺旋結晶之吸熱峰。由澱粉體外消化及推估升糖指數試驗結果得知，經濕熱處理之THAMC澱粉，其抗性澱粉含量可顯著提升5.21%，且具有與Hi-maize® 260 (59.37)相近之eGI值。

Abstract There are three parts are included in this study. The first part of this study includes the determinations and comparisons of physicochemical properties and digestibility of (1) the starch isolated from the Taiwanese high amylose corn (THAMC), commercial Hylon V, Hylon VII and Hi-maize® 260, and (2) THAMC whole grain flour and commercial corn flours. The results showed that the starches isolated from the first and the second batches of THAMC had higher amylose content (79.33 and 77.29%) than Hylon V (57.03%), Hylon VII (68.27%) and Hi-maize® 260 (66.69%). The THAMC starch had higher contents of amylose and bound lipid than the commercial normal corn starch, suggested the higher tendency of the formation of amylose-lipid complex. This could be evidenced by the measurements of differential scanning calorimetry (DSC), which an endothermic peak at 84-108°C with a delta enthalpy of 2.73-3.21 J/g was determined. The low swelling property and solubility of THAMC starch at 95℃ is attributed to its high gelatinization temperature (98.59°C determined by DSC). The pasting properties determined by rapid viscosity analyzer (RVA) showed that the THAMC starch paste (14%) had higher viscosity than that of Hi-maize® 260. However, their viscosities were much lower than Hylon VII paste, attributed to the high amylose content and high gelatinization temperature of the former samples. The resistant starch contents of THAMC starch (58.92-59.6%) were higher than the commercial Hylon V (44.18%) and Hylon VII (45.46%). The estimated glycemic index (eGI) of THAMC were 65.01-67.34, which is slightly higher than Hi-maize® 260 (59.34). The thousand-kernel weight of THAMC was lower than the commercial corn, indicating the slimmer kernels of THAMC. As a result, the THAMC whole grain flour containing relatively lower total starch content but relatively higher contents of crude protein, crude fat, ash, total yellow pigment, lutein, zeaxanthin and total phenolic compound could be expected. The resistant starch contents (31.51-34.31%) of THAMC whole grain flour were higher than the commercial whole corn flour (27.67%) and its milling products (17.72-24.76%). In the second part of this study, 0-30% of wheat flour were substituted by using the THAMC starch or whole grain flour for bread and chiffon cake making. The eGI values of breads and cakes made with 10 and 20% substitutions of THAMC starch was lower than the control sample (0% substitution), and the resistant starch content increased with increasing the percentage of substitution. In the last part of this study, the effect of hydrothermal treatment (100°C/24 h) on the physicochemical properties and starch digestion properties of THAMC starch were estimated. There were no significant differences on the viscosity of THAMC starch paste before and after hydrothermal treatments. While, an endothermic peak at 121-157°C was determined by DSC, suggesting the formation of amylose double helix. The increase of resistant starch content (5.21%) of hydrothermal treated THAMC starch with the eGI value of 58.17 similar to that of Hi-maize® 260 (59.37), was obtained.