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Gluten-Free Bread from Sorghum: Quality Differences Among Hybrids

¹Department of Food and Nutritional Sciences and National Food Biotechnology Centre, University College Cork, College Road, Cork, Ireland. ²Present address: Department of Biological and Agricultural Engineering, Seaton Hall, Kansas State University, Manhattan, KS 66506. ³Corresponding author. Phone: 785-776-2708. Fax: 785-537-5534. E-mail: tilman.schober@gmprc.ksu.edu ⁴Department of Food Technology, University of Applied Sciences, Fulda, Germany. ⁵USDA-ARS, GMPRC, Manhattan, KS 66502. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable.

Gluten-free breadmaking quality of 10 sorghum flours was compared using (relative basis) decorticated sorghum flour (70), corn starch (30), water (105), salt (1.75), sugar (1), and dried yeast (2). Batter consistency was standardized by varying water levels to achieve the same force during extrusion. Crumb properties were evaluated by digital image analysis and texture profile analysis (TPA). Significant differences (P < 0.001) in crumb grain were found among the hybrids with mean cell area ranging from 1.3 to 3.3 mm² and total number of cells ranging from 13.5 to 27.8/cm². TPA hardness values of the crumb also varied significantly (P < 0.001). Based on significant correlations (P < 0.01), starch damage, influenced by kernel hardness, was identified as a key element for these differences. Breads differed little in volume, height, bake loss, and water activity. Investigation of added ingredients on bread quality was conducted using response surface methodology (RSM) with two sorghum hybrids of opposite quality. Addition of xanthan gum (0.3–1.2% flour weight basis [fwb]) and skim milk powder (1.2–4.8% fwb) and varying water levels (100–115% fwb) were tested using a central composite design. Increasing water levels increased loaf specific volume, while increasing xanthan gum levels decreased the volume. As skim milk powder levels increased, loaf height decreased. Quality differences between the hybrids were maintained throughout the RSM.