無麩質類麵包產品之研製–米穀粉原料性質與配方探討

Abstract

米穀粉為無麩質類麵包產品製作之主要原料，除了直鏈澱粉含量外，米穀粉破損澱粉含量及粒徑分布亦會影響其加工性質，而破損澱粉及粒徑往往決定於米粒結構及磨粉機運作機制。因此，本試驗分成無麩質類麵包產品製作及米穀粉原料兩部分作探討；第一部分以臺稉9號(TK9)米穀粉為主原料，開發無麩質類麵包產品配方，建立簡易調整最適加水量的方法，並確立無麩質類麵包產品製作方式，第二部分將臺稉9號及臺稉9號白粒(TK9c)米粒以papain或Viscozyme溶液調濕後，加熱處理，改變米粒結構，以探討酵素預處理米粒對磨粉性質的影響，並探討其對無麩質類麵包產品的影響，最後則添加maltogenic α-amylase於配方中，探討澱粉分解酵素改善無麩質類麵包產品品質之可行性。試驗結果顯示，當米糊稠度以擴散黏度測定值(spreading distance in 2 min)為1.5 cm/2 min時，米糊兼具有良好保氣性及適當流動性，所製得無麩質類麵包產品有較大之比體積及均一之孔洞分布。當使用低破損澱粉含量米穀粉時，米糊水分含量愈高之配方，其無麩質類麵包產品水分含量愈高，此時無麩質類麵包產品質地較柔軟，老化速率亦較慢；但高水分麵包之內部組織(crumb)因有許多大的孔洞，而影響其外觀與質地。為維持米糊稠度為擴散黏度測定值=1.5 cm/2 min，在配方中可適量混摻高破損澱粉含量之米穀粉及/或額外添加膠體，可製作出水分含量高之柔軟麵包，亦可顯著改善無麩質類麵包產品之組織結構與外觀。米粒磨粉試驗結果顯示，米粒預處理時，乾燥後水分含量越低，製得米穀粉之破損澱粉含量越低，且與未處理之控制組相比，凡經預處理之米粒其硬度均下降，其中尤以經調濕及水洗後的米粒，硬度為最低。酵素預處理米粒磨粉後，破損澱粉含量些微下降，具有較低的粒徑，但其糊液黏度亦較低。將米粒直接以80◦C烘乾至8%水分含量之米粒，其米穀粉破損含量最低。以未經處理之TK9及TK9c米穀粉、papain處理之米穀粉(TK9-P-W、TK9c-P-W)及直接加熱處理之米穀粉(TK9-X-N、TK9c-X-N)製作無麩質類麵包產品時，發現TK9c無麩質類麵包產品內部組織孔洞較TK9無麩質類麵包產品大，TK9-P-W及TK9c-P-W無麩質類麵包產品比體積最小，經預處理之米穀粉(TK9-P-W、TK9c-P-W、TK9-X-N及TK9c-X-N)製得無麩質類麵包產品硬化速率較未經預處理者為低(TK9及TK9c)。Maltogenic α-amylase可有效延緩無麩質類麵包產品硬化，此酵素亦會降解澱粉分子，導致澱粉糊液黏度下降，無麩質類麵包產品內部組織孔洞變大，過高劑量添加時，甚至使無麩質類麵包產品出現液化現象。

Rice flour is a main raw material of gluten-free bread-like product. The factors affecting the rice flour applications in this product include the contents of amylose and damaged starch and the particle size distribution. Damaged starch content, depending on the structure of rice grains and the type of mill used for milling, is one of important indexes of rice milling performance. Therefore, the objectives of this study are to develop the formula of gluten-free bread-like product with TK9 rice flour and establish the method and index that could be used to adjust the water absorption easily, and to investigate the effects of papain and Viscozyme treatments on TK9 and TK9c (chalky) rice milling performance and applications on the gluten-free bread-like products. The last part of this study is to evaluate the effects of maltogenic α-amylase on the staling of gluten-free bread-like products. The results of baking test indicated that the rice batter consistency measured by spreading test, which the spreading distance of batter in 2 min was 1.5 cm/2 min having a good gas retention and fluidity and having a big specific volume and uniform pore distribution. Increasing water absorption in formula would increase the moisture content of gluten-free bread, which had soft crumb with slow staling rate. However, the bread crumb with open cell and coarse crumb texture of high water absorption formula was the major drawback which could be improved by blending with high damaged starch rice flour and/or adding extra amount of gums in formula to meet the defined rice batter consistency, which spreading distance equal to 1.5 cm/2 min. The results of milling test indicated that the rice flour with lower damaged starch content could be obtained by milling the rice grains with low moisture content by drying the grains to 8% moisture content before milling. Pretreatment significantly decreased the rice grain hardness, especially pretreated by tempering and washing. Damaged starch content, mean particle size and paste viscosity of rice flour pretreated with enzymes were slightly lower than the non-pretreated rice flour. In practice, drying the rice grains at 80◦C to 8% moisture content is an easy way to obtain the rice flour with low damaged starch content. The bread-like product were made with TK9, TK9c, papain pretreated (TK9-P-W, TK9c-P-W) and heat pretreated (TK9-X-N, TK9c-X-N) rice flour. The pore size of TK9c crumb was bigger than TK9 crumb. TK9-P-W and TK9c-P-W breadhad smallest bread specific volume. The hardening rate of breads made with pretreated rice flour (TK9-P-W, TK9c-P-W, TK9-X-N, TK9c-X-N) were lower than the breads made with native rice flour (TK9 and TK9c). Maltogenic α-amylase could retard gluten-free bread staling. However the enzyme decreased rice starch viscosity, the pore of crumb became larger. Overdose of Maltogenic α-amylase could make gluten-free bread-like product liquefy.