Effect of Whole Quinoa Flours and Lipase on the Chemical, Rheological and Breadmaking Characteristics of Wheat Flour

Abstract

Bakery products are gaining great interest from consumers for their convenience, variety of taste and relatively low price. The consumersrequirements led to development of various tastes and to improvement of the nutritional value with addition of functional supplements to bread ingredients. Although quinoa is one of the oldest traditional cereals that has been cultivated since the age of the Inca Empire, it was not generally used for daily diet. However, after NASA s recommendation of quinoa as one of the suitable plants for CELSS (Controlled Ecological Life Support System) in the 90s, quinoa has been used for various food ingredients. Hence, bread made from quinoa flour substitution for wheat flour is served to patients suffering from wheat allergy. The functional properties of quinoa seeds have been previously studied 1) and also a small amount substitution of quinoa flour for wheat flour made relatively positive bread qualities. 2,3) In contrast, the increase in the amount of quinoa flour for wheat flour showed a decrease in the loaf volume and dough qualities. This result was surely due to the deficiency of gluten and the increase of the bran fraction. Though quinoa can be used in various ways, very few scientific reports have described its effects on baking quality. In the present study, two different treatments of whole quinoa seeds, stone mortar milled quinoa flour (SMQ) and roller milled and roastedquinoa flour (RMRQ), were carried out for preventing the loss of nutritional components and improvement of flavor, respectively. It is generally believed that the stonemortarmilled flour has less loss of nutritional components than rollermilled flour as the rise of temperature is suppressed during milling. In addition, in ancient times, roasting was traditionally used to improve the flavor of tea and coffee. Since similar effects might be found by applying the roasting treatment to quinoa, two kinds of whole quinoa flours were prepared for the present experiments. Furthermore, quinoa flours contained a high amount (67%, ww) of lipid, and then bacterial li-pase was added to the quinoa substituted wheat flour to improve the quality of bread, as reported previously, 4) because consumers do not prefer artificial improvers to be used for food ingredients. The purpose of this study was to test the dough properties and baking quality for practical applications of SMQ and RMRQ with or without li-pase. MATERIALS AND METHODS Materials. Wheat flour used for bread making was a hardtype commercialCameriaobtained from Nisshin Flour Milling Inc. (Kobe, Japan). Two kinds of quinoa flours (Chenopodium quinoa Willd.), SMQ and RMRQ, were obtained from DaiNippon Meiji Sugar Co., Ltd. (Sakai, Japan) which imported quinoa seeds from Peru. Abstract: Two kinds of whole quinoa seeds, the stone-mortar milled quinoa flourSMQand the roller milled and roasted-quinoa flourRMRQ , were tested for their chemical, rheological and breadmaking characteristics. The loaf volume of breads baked with SMQ and RMRQ substituted wheat flour distinctly decreased in proportion to the increase of substitution30%, ww. The additions of lipase7.510 3 Ugsignifi-cantly increased the loaf volume of SMQ or RMRQ substituted wheat bread, except for the 30% substitution of RMRQ. Addition of lipase to SMQ or RMRQ substituted wheat bread distinctly decreased the firmness of breadcrumbs compared to those without lipase. Lipase addition to SMQ and RMRQ substituted doughs lowered viscosity, while the enthalpy change of melting for starch-lipid complexesH2was slightly higher than the substituted doughs without lipase. Microscopic observation of the SMQ substituted dough30%, ww showed that the increase in the substitution of SMQ could not form a well-developed gluten matrix. However, addition of lipase to the SMQ substituted dough sufficiently made the extensible gluten structure that covered starch granules. The increase in the amount of substitution of SMQ and RMRQ for wheat flour showed unfavorable bread quality, but the addition of lipase to SMQ or RMRQ substitution distinctly improved the bread qualities. These improvements might be caused by the effects of mono-and di-acylglycerol as natural emulsifi-ers, which were increased from lipid hydrolyzed by lipase during breadmaking.