植物膠與預糊化澱粉對非麩質米穀粉麵包
品質性質之研究

本研究主要以國內的重要米種-蓬萊米為原料，探討無麩質麵包麵糰水分最適量，以及添加預糊化米穀粉、水膠體及預糊化澱粉的效果，並利用麵糰發酵過程中的體積膨脹率進行配方效果的篩選，能有效預估結果且節省實驗時間。米穀粉麵糰在發酵50分鐘達到最大膨發體積率 253%±22 %，小麥麵粉麵糰在發酵70分鐘達到最大膨發體積率454%±7 %。添加2%甲基纖維素在70分鐘達到最大膨發體積率309%±38%，但隨著添加量的增加，膨發體積率降低。添加1%羧甲基纖維素在40分鐘達到最大膨發體積率224%±37%，但隨著添加量的增加，膨發體積率沒有顯著下降。添加10%預糊化米澱粉在30分鐘達到最大膨發體積率150%±12 %，添加5%預糊化玉米澱粉在170分鐘達到最大膨發體積率225%±10 %，但隨著添加量的增加，膨發體積率降低。水分對於烘焙產品的膨發體積會有顯著性影響，比體積在水分80%最大，但比較氣泡數及氣泡密度時，70%水分者皆顯著高於其他兩者(P<0.05)，由實驗觀測發現水分的影響主要是影響麵糰的流動性。添加預糊化米穀粉10、20及30%時會改變麵糰的流動性，皆會降低比體積，也改變氣泡數及氣泡密度。比較不同的水膠體與預糊化澱粉對米穀粉麵包之影響，結果發現，添加2%甲基纖維素、1%羧甲基纖維素的水膠體與5%預糊化澱粉(CH-20)對烘焙流失皆具有不同程度的降低效果，可以取代部份的麵筋功能，增加米穀粉麵包的保水性。對比體積的影響皆不顯著，但會增加氣泡密度，其中以添加1%羧甲基纖維素效果最好。氣泡密度的增加主要是因氣泡大小變小。在質地分析的結果顯示，添加2%甲基纖維素有最大的硬度，在黏性 (Gumminess)及咀嚼性(Chewiness)上也有相同的趨勢。色澤上，除添加2%甲基纖維素者在L值上有顯著性較高外，各配方並沒有顯著差異。感官品評結果顯示，添加不同的水膠體或預糊化澱粉之米穀粉麵包間在顏色、質地、風味及整體喜好度上並沒有顯著差異，就整體接受性之分數而言，正常配方之小麥麵包為7.83，而不同配方之米穀粉麵為5.23~6.00。總體而言，單純添加不同的水膠體與預糊化澱粉，只能改善部分的米穀粉麵包的性質。由實驗結果發現添加2%甲基纖維素、1%羧甲基纖維素及5%預糊化澱粉能有效改善米穀粉麵包的烘焙流失及氣泡密度，但對於氣泡大小的影響，以甲基纖維素較為顯著，預糊化澱粉改善效果雖較不顯著，但添加5%預糊化澱粉，若發酵時間延長為兩小時(120分鐘)，則可增加米穀粉麵糰的體積膨脹率，且增加麵糰的黏稠度，可以減少因氣泡集中變大，在冷卻過程結構的榻餡。

關鍵字

米麵包，水膠體，預糊化澱粉，物理性質

並列摘要

Leavening volume of dough in the fermentation process is an important factor in determining the texture of the bread. Due to lack of gluten to holding gas in the dough, the rice flour-based gluten-free bread could not develop suitable texture properties. Therefore, this study was investigated the leavening volume of rice dough during fermentation by adding hydrocolloids and pre-gelatinized starch as formulating the rice bread. Results showed that the maximum volume expansion ratio of rice flour dough was 253%±22 % after 50 min. in fermentation stage; wheat dough was 452% after 70min. And, the maximum volume expansion ratio of adding 2% methylcellulose was 309%±38% after 70min., but decreasing with the increasing addition. Adding 1% carboxymethyl cellulose was 224%±37% after 40 min., but didn’t significantly change with increasing addition. Adding 10% pre-gelatinized rice flour was 150%±12 % after 30 min. and adding 5% pre-gelatinized corn starch was 225%±10 % after 170 min., however, the maximum volume expansion ratio decreased with the increasing of addition level of pre-gelatinized starch. The specific volume of rice bread has significantly been affected by water content. 80% moisture of rice bread has significant highest specific volume with comparing 70% and 90% moisture. Comparing the number of air cells and cells density in the crumb, 70% moisture is significantly higher than the other two (P <0.05), presumably water, effects mainly affecting the rheology properties of the dough. Addition of pre-gelatinized rice flour decreased the specific volume, but also significantly influenced the number of air cells and cells density of rice breads. Compare effects of different hydrocolloids and modified starch on the properties of rice flour bread. The results found that all of the addition of 2% methyl cellulose, carboxymethyl cellulose 1% and 5% modified starch (CH-20) in formulation could reduce the baking loss. Due to those hydrocolloids and modified starch can replace part of the function of gluten protein and increase water retention. Although hydrocolloids and modified starch don’t improve significantly the specific volume of crumb, but they will increase the density of the air cells, which added 1% carboxymethyl cellulose has highest air cells density. Air cells density increase is mainly due to the cell size reduction. The results of texture profile analysis showed that the addition of 2% methylcellulose has highest hardness, and also have the same tendency in gumminess and chewiness. The color parameters, except for the addition of 2% methylcellulose were on the L values are significantly higher, but each recipe were not significant differences. Results of sensory evaluation showing that adding different hydrocolloid or modified in color, texture, flavor and overall acceptability were not significant difference. The overall acceptability of the score, the wheat bread normal formula of 7.83 is significantly higher than 5.23 ~ 6.00 of rice flour breads with different formulations. This study shows that simply addition of different hydrocolloids and modified starch, can only partially improve the properties of rice flour bread.