Studies on the development and properties of the gluten-free tart crust and lemon pudding fillings

Abstract

無麩質烘焙產品近年來因健康議題漸受關注，也越多學者對視為主食的「米」進行相關產品的研究。然而，以米穀為基底的無麩質塔皮，所用的稻米由於缺乏能形成雙硫鍵架構的胺基酸，使加工性能遠低於小麥，再加上缺乏麥穀及醇溶蛋白，無法構成麵筋，所以不易成型，製品易斷裂，是生產加工之困難點。本研究以國內重要米種─蓬萊米磨成的穀物粉為主原料， 透過添加不同比例之市售杏仁粉、薏仁粉及亞麻仁籽粉，開發無麩質之塔皮及探討配方對無麩質塔皮理化特性的影響，包括塔皮麵糰與成品之色澤、質地以及官能特性等。另以常用市售澱粉 (包括玉米、小麥、樹薯及馬鈴薯澱粉) 製備檸檬布丁餡料，探討澱粉種類及添加濃度對檸檬布丁餡料增稠凝膠效應的影響。首先在塔皮之色澤方面，添加薏仁粉及亞麻仁籽粉之組別 (50R50D、50A50D、50R25A25F、50R25D25F) L、a、b 值皆較低，偏暗黃色；而添加杏仁粉之組別 L、a、b 值較高，偏亮黃色，其中以 50R50A 組與僅使用中筋麵粉之控制組 (100P) 外觀顏色最為相近，推測色澤會受到穀物粉本身顏色及混合比例所影響。就麵糰質地分析而言，添加杏仁粉之硬度小、黏性高，表示其具有延展性，易於成糰，但操作時，相對黏手，而造成較多損耗；相反地，添加薏仁粉之硬度大、內聚性高，表示其塑形後，形狀較能維持一段時間，於入模時，相對不黏手，但缺點為無延展性，使得操作時易碎裂，不易成糰。而塔皮成品之質地分析結果顯示，有添加薏仁粉的組別硬度高，且隨著添加比例的增加，硬度值提高；而杏仁粉的添加則使硬度下降，且隨著添加比例的增加，硬度值下降。此外，比較 50R25A25F 和 50R25D25F 二組發現，亞麻仁籽粉的添加也會使硬度下降，產生酥鬆感。由上述結果可知，若把市售蓬萊米粉和杏仁粉、糙薏仁粉、亞麻仁粉按一定的比例混合，可生產出新型焙烤食品，不僅克服了加工上的難題，同時又能提高產品營養價值。而餡料之實驗結果顯示，色澤方面，經過冷藏 48 小時後，所有組之 L 值與冷藏前相比，皆有顯著差異，且亮度值有微幅提高。而在 b 值方面，以 8% 小麥澱粉組為最低。表示除了 8% 小麥澱粉組外，其他組的成品顏色為更符合販賣理想的亮黃色。在質地分析方面，冷藏後之各組硬度及膠黏性皆有所增加，其中，硬度值明顯隨冷藏時間拉長而增加，但冷藏時間的拉長，並不會使膠黏性隨之增加。由上述實驗分析可知，若使用不同澱粉或添加不同比例，不只能營造新的口感，增加食用趣味性，亦或能使餡料更為凝聚，讓成品於一口咬下時，不致流得滿手，這些結果可作為日後改善餡料品質的參考。

Recently, the consumers are increasingly concerned about gluten-free baking products since health issues, and there were more scholars have studied the related products of 'rice', which is a staple food in Taiwan. Due to the lack of proteins can constitute gluten, the processing performance of rice is much lower than wheat, so that the production of rice-based gluten-free tart crust isn't easy to shape, and break easily. In this study, the domestic rice varieties - Japonica rice ground into flour as the main raw material, through the addition of different proportions of commercially available almond powder, dehulled adlay powder and flaxseed powder to develop gluten-free tart crust and analysis its physical properties, including the color, texture and functional properties of the dough and the finished product. Moreover, the effects of starch types and added concentrations on the thickening gel of lemon pudding fillings were studied by using commercially available starch (including corn, wheat, potato and potato starch). The color results of gluten-free tart crusts showed that dehulled adlay powder-added group (50R50D, 50A50D, 50R25A25F, 50R25D25F) were dark yellow; and almond powder-added group were bright yellow. Addtionally, only the 50R50A group had no significant difference with the control group (100P). It revealed the color of tart crust would be affected by the color of grain itself and the mixing ratio. On the texture analysis of tart crust dough, the hardness of addition of almond powder groups were low and had ductility for good operation, but its stickiness might cause dough loss. The hardness of addition of dehulled adlay powder groups were high, and its high cohesion could keep the shape of the dough in the mold be maintained for a while. But its non-ductility increased the difficulty of dough production, which was easy to break. On the texture analysis of tart crust product, the results showed that the hardness value was increased with the increase of the dehulled adlay powder addition ratio. On the contrary, the addition of almond powder decreased the hardness, and the hardness value drops with the increase of almond powder. In addition, compared 50R25A25F and 50R25D25F two groups found that the addition of flaxseed powder will also make the hardness decreased, resulting in crisp feeling. Due to those results mentioned above, using the commercial rice flour and almond powder, dehulled adlay flour, flaxseed powder to mix with certain proportion, could become a good baking material to produce a new type of baked goods, not only overcome the processing problems, but also improve product nutritional value. The color results of the lemon pudding fillings showed that the L value of all groups after 48 hours cooling storage compared with fresh cooked were significant difference, and the values had increased slightly. And in the b value, the 8% wheat starch group was the lowest. It seemed that the color of other groups were bright yellow which was more close to the ideal selling product except for 8% wheat starch group. In terms of texture analysis, the hardness and gumminess of each group after cold storage increased, in which the hardness value increased significantly with the cold storage time. But the elongation of cold storage time wouldn't make the value of gumminess increase. All of the above results proved that the temperature really had great impact on the colloidal structure. Moreover, the use of different starch or add a different proportion can not only create a new taste texture, but make the fillings more cohesive for reaching the goal of perfect combination between tart crust and the fillings. These results can be used as a reference for improving the quality of fillings in the future.