Process Optimization and Characterization of Sorghum Based Extruded Product

Abstract: Expanded snacks made up of corn， wheat and rice is very popular because of their texture. Sorghum is one of the important cereals， which is not so far studied well for extrusion processing. Due to presence of high amount of starch (56%-73%): sorghum could be the good candidate for manufacturing of expanded snacks. The extruded products obtained using extrusion conditions such as feed moisture content (12%-16%)， die temperature (150-190 °C)， screw speed (150-210 rpm) and feed rate (50-70 g min^-1) are further characterized by analyzing bulk density， expansion ratio， water absorption index (WAI)， water solubility index(WSI)， textural properties， color and sensory evaluation. Increase in feed moisture content resulted in extrudates with gradual increase in density， WAI and hardness and decrease in expansion， WSI， crispness and whiteness. Higher barrel temperature reduced the extrudate expansion， bulk density and hardness and increased the WSI and crispness of the extrudates. The most acceptable product is obtained using response surface methodology (RSM).

Key words: Extrusion， sorghum， physical properties， response surface methodology.

1. Introduction

Grain sorghum is the third most important cereal crop grown in the United States and the fifth most important cereal crop grown in the world. Nigeria is the world’s largest producer of grain sorghum followed by United States and India. It is a leading cereal grain produced in Africa and is an important food source in India. India is currently positioned as the number three in production with 11.7% of world sorghum production and the fourth exporter of sorghum in the world market. In many parts of the world sorghum has traditionally been used for preparing many food products such as porridge， unleavened bread， cookies， cakes， couscous and malted beverages. Either whole grains or flour is being used in making various traditional products. The most important property of sorghum is that its gluten free and hence may be more suitable for the gluten intolerance people. Some of the sorghum varieties are also rich in antioxidants [1， 2].

Acknowledgments

The authors are grateful to the Sorghum Research Station (SRS)， Marathwada Agricultural University， Parbhani， India， for providing varieties of sorghum for this research work.

References

[1] A.C. Smith， N. Singh， New applications of extrusion technology， Indian Food Industry 15 (1996) 14-23.

[2] L.A.M. Pelembe， C. Erasmus， J.R.N. Taylor， development of a protein-rich composite sorghum-cowpea instant porridge by extrusion cooking process， Lebensm-Wiss.U. Technol. 35 (2002) 120-127.

[3] N.J. Mesa-Stonestreet， A. Sajid， G. Jeff， Extrusion-enzyme liquefaction as a method for producing sorghum protein concentrates， Journal of Food Engineering 108 (2) (2012) 365-375.

[4] M.H. Gomez， J.M. Aguilera， Changes in the starch fraction during extrusion cooking of corn， Journal of Food Science 48 (1983) 378-381.

[5] M.H. Gomez， J.M. Aguilera， A physicochemical model for extrusion of corn starch， Journal of Food Science 49(1984) 40-49.

[6] V.J. Davidson， D. Paton， L.L. Diosady， G. Larocque， Degradation of wheat starch in a single screw extruder: Characteristics of extruded starch polymers， Journal of Food Science 49 (1984) 453-458.

[7] C. Mercier， P. Feillet， Modification of carbohydrate component by extrusion cooking of cereal product， Cereal Chemistry 52 (1975) 283-297.

[8] K. Mahasukhonthachat， P.A. Sopade， M.J. Gidley， Kinetics of starch digestion in sorghum as affected by particle size， Journal of Food Engineering 96 (2010) 18-28.

[9] P. Colonna， C. Mercier， Macromolecular modifications of manoic starch components by extrusion cooking with and without lipids， Carbohydrate Polymers 3 (1983) 87-108.

[10] P. Colonna， J.L. Doublier， J.P. Melcion， F. Monredon， C. Mercier， Extrusion cooking and drum drying of wheat starch: I. Physical and macromolecular modifications， Cereal Chemistry 61 (6) (1984) 538-543.

[11] L.F. Wen， P. Rodis， B.P. Wasserman， Starch fragmentation and protein insolubilization during twin screw extrusion of corn meal， Cereal Chemistry 67 (3)(1990) 268-275.

[12] N. Singh， P. Cairns， V.J. Morris， A.C. Smith， Physical properties of extruded wheat starch-additive mixtures， Cereal Chemistry 75 (1998) 325-330.

[13] S.I. Fletcher， P. Richmond， A.C. Smith， An experimental study of twin-screw extrusion cooking of maize grits， Journal of Food Engineering 4 (1985) 291-312.

[14] Association of Official Analytical Chemists (AOAC)， Official Methods of AOAC， Volume II， Association of Official Chemists， Washington， 1984.

[15] Association of Official Analytical Chemists (AOAC)， Official Methods of AOAC， International， 18th ed.， Gaithersburg， MD， USA， 2006.

[16] Association of Official Analytical Chemists (AOAC)， Official Methods of AOAC， Volume II， Association of Official Chemists， Washington， 1980.

[17] B. Launay， L.M. Lisch， Twin screw extrusion cooking of starches: Flow behaviour of starch pastes， expansion and mechanical properties of extrudates， Journal of Food Engineering 2 (1983) 259-280.

[18] R.A. Anderson， H.F. Conway， V.F. Pfeifer， E.L. Griffin， Gelatinization of corn grits by roll and extrusion cooking， Cereal Science Today 14 (1969) 4-12.

[19] Vainiopaa， Modelling of extrusion cooking of cereals using Response Surface Methodology， Journal of Food Engineering 13 (1) (1991) 1-26.

[20] W.R. Mason， R.C. Hoseney， Factors affecting the viscosity of extrusion-cooked wheat starch， Cereal Chemistry 63 (1986) 436-441.

[21] A.R. Kirby， A.L. Ollett， R. Parker， A.C. Smith， An experimental study of screw configuration effects in the twin-screw extrusion-cooking of maize grits， Journal of Food Engineering 8 (1988) 247-272.

[22] J.M. Faubion， R.C. Hoseney， High-temperature short-time extrusion cooking of wheat starch and flour: I. Effect of moisture and flour type on extrudate properties， Cereal Chemistry 59(1982) 529-533.

[23] Y. Liu， F. Hsieh， H. Heymann， H.E. Huff， Effect of process conditions on the physical and sensory properties of extruded oat-corn puff， Journal of Food Science 65(2000) 1253-1259.

[24] G.J. Al-Rabadi， P.J. Tarley， B.A. Williams， W.L. Bryden， M.J. Gidley， Particle size of milled barley and sorghum and physico-chemical properties of grain following extrusion， Journal of Food Engineering 103 (4) (2011) 464-472.