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Physicochemical Properties of Flours that Relate to Sorghum Couscous Quality¹

¹Paper 15706 of the Purdue University Agricultural Research Programs. ²Department of Food Science and the Whistler Center for Carbohydrate Research, Purdue University, 1160 Smith Hall, West Lafayette, IN 47907-1160. ³Corresponding author. E-mail: hamakerb@foodsci.purdue.edu Phone: 765/494-5886. Fax: 765/494-7953.

Flours from eight sorghum cultivars were evaluated for their couscous-making ability with the objective of finding predictive relationships between flour physicochemical properties and couscous quality. Chemical composition, physical characteristics, and pasting and gelatinization properties of the flours were determined. A laboratory procedure was used to prepare couscous. Couscous properties were evaluated and compared to a laboratory-prepared and a commercial durum wheat couscous. Hard grain produced flours containing a high proportion of coarse particles with low ash and high damaged starch content and yielded a higher proportion of desirable sorghum couscous granules. A variety of colors ranging from brown to yellow were obtained when flours were processed into couscous. Cooked sorghum couscous stickiness was positively correlated (r = 0.89, P < 0.01) with the amount of damaged starch in flour. Cooked couscous hardness correlated positively (r = 0.79, P < 0.05) with apparent amylose content of flour and correlated negatively (r = -0.75, P < 0.05) with flour peak viscosity. Durum wheat couscous was lighter and had more yellow color than sorghum couscous. Sorghum couscous was stickier and harder than durum wheat couscous. Addition of 2% oil to the cooking water considerably improved the texture of some sorghum couscous to a level comparable to that of durum wheat couscous.