qualitycharacteristics of gluten-free ricecakes

Gluten replacement is nowadays one of the most challenging issues for food science and technology since a lifelong gluten-free diet is essential for patients having gluten-sensitive enteropathy (GSE) or celiac disease. GSE is characterized by small intestinal malabsorption of nutrients after ingestion of prolamins from wheat and also other Triticum species like rye, barley, oat and their crossbred varieties. The number of patients having celiac disease is estimated as one out of 85–500 people in Europe, which changes depending on the country (Farrell & Kelly, 2001). Therefore, alternative food products having the identical quality characteristics as products containing gluten is a very crucial point. Rice (Oryza sativa), which has very low level of gluten, low levels of sodium, protein, fat, fiber and a high amount of easily digested carbohydrates, is one of the most frequently used cereals as a wheat substitute in gluten-free food products (Sivaramakrishnan, Senge, & Chattopadhyay, 2004). However, some food additives such as starches, gums, hydrocolloids or dairy products should be added to the gluten-free food products to obtain the desired quality. Gums are added to the food products mainly for their thickening and gelling properties. In addition, they are used to improve mouth feel and to change the viscosity of solutions due to their high polymeric nature and the interactions between polymer chains when they are dissolved or dispersed (Yaseen, Herald, Aramouni, & Alavi, 2005). In the study of O¨ zboy (2002), five different commercial food grade gums namely xanthan–guar gum blend, carrageenan gum, guar–carrageenan gum blend, xanthan–carrageenan gum blend and locust bean gum, were added to the corn starch to produce low phenylalanine starch–gum bread for phenylketonuria patients. McCarty, Gallagher, Gormley, Schober, and Arendt (2005) optimized gluten-free bread formulation based on mainly rice flour, potato starch and skim milk powder.

 

Rheological information is valuable in product development. In the study performed by Chun and Yoo (2004), the rice flour dispersions showed a high shear-thinning behavior with low magnitudes of Casson yield stress. Sivaramakrishnan et al. (2004) found that the rice dough containing hydroxy propyl methyl cellulose (HPMC) had similar rheological properties as that of wheat flour dough and was suitable for making rice bread. Yoo, Kim, and Yoo (2005) found that rice starch–galactomannan mixtures such as guar gum and locust bean gum showed high shear-thinning flow behaviors with high Casson yield stress. Based on dynamic shear data, glutinous rice flour dispersions at concentrations of 4–8% exhibited rheological behavior similar to weak gels (Yoo, 2006). Rice starch–xanthan gum mixtures at 25 1C have shown shear thinning flow behavior and both consistency index and apparent viscosity of mixtures increased with the increase in gum concentration (Kim & Yoo, 2006). Emulsifiers that have a common use in the baking industry have the ability to provide the necessary aeration and gas bubble stability during the process until the cake structure is set (Sahi & Alava, 2003). Emulsifiers function by reducing the interfacial tension between oil and water and therefore, facilitate the disruption of emulsion droplets.

 

Many researchers have shown in their studies that protein-emulsifier interactions influence the rheology of emulsions (Chen & Dickinson, 1998; Dickinson & Hong, 1995; Dickinson & Yamamoto, 1996; Sakiyan, Sumnu, Sahin, & Bayram, 2004). Microwave baking can be an alternative to conventional baking since microwaves reduce baking time and energy significantly. Since the microwave oven is at ambient temperature, the surface temperature of product is not high enough to promote browning and crust formation during microwave baking. Other quality problems observed in microwave-baked products are, firm and tough texture, rapid staling, lack of color and a dry product. In order to reduce these problems, microwave heating is recently combined with near infrared (IR) heating. IR radiation affects the surface of the product and browning and crisping can occur during baking when halogen lamps are used. Usage of IR-microwave combination baking has been shown to reduce the conventional baking time of breads by 60% recently (Demirekler, Sumnu, & Sahin, 2004). It was possible to produce high-quality cakes in IR-microwave combination oven by reducing the conventional baking time by about 79% (Sevimli, Sumnu, & Sahin, 2005). However, the quality of rice cakes baked in IR-microwave combination oven has not been studied so far. In the literature, there is no study on the rheological properties of gluten-free cake batter made from rice flour containing gums and emulsifier. Therefore, the present study was conducted to model the rheological characteristics of gluten-free cake batter made from rice flour and to compare the impact of different gums on rice batters and cake properties, which was baked in IR-microwave combination oven.