Effects of Extrusion Operating Conditions and Blend Proportion on the Expansion Properties of Sorghum-Barley-Chickpea blend Extruded Products

Effects of Extrusion Operating Conditions and Blend Proportion on the Expansion Properties of Sorghum-Barley-Chickpea blend Extruded Products

Byreddy Naveena^* , Mohan Singh

Department of Post Harvest Process and Food Engineering, Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur, Madhya Pradesh, India

Corresponding Author Email: naveenachittinavi@gmail.com

DOI : http://dx.doi.org/10.53709/CHE.2021.v02i04.028

Abstract

Keywords

Download this article as:

INTRODUCTION                                                                                                                      

            Extrusion cooking is a versatile and well-established food process that is used to make extended snack foods, pastes, modified starches, flat breads, meat and cheese analogues, ready-to-eat cereal dishes, and porridge all over the world [16]. Extrusion’s main purpose is to promote dietary variety by creating a variety of products with diverse shapes, textures, colours, and flavours from basic ingredients [4]. One way to make textured snack food is to use extrusion cooking which is high-temperature short-time (HTST) procedure. Extrusion cooking differs from other processes in that it operates at high temperatures, pressures, and shears while maintaining low-intermediate moisture content and provides ingredient modification in the feed mixture [13]. Through the utilization of temperature, moisture, shear, and mixing conditions, it is excellent for the production of fiber-rich foods [12] and [1].

            After rice and wheat, sorghum (Sorghum bicolor) is India’s third most major essential cereal. Sorghum’s chemical constituents are similar to those of maize and wheat. It is also said to be a possible source of nutraceuticals such as cholesterol-lowering waxes and antioxidant phenolics [15]. Starch is the main component of sorghum grain, followed by proteins, non-starch polysaccharides and fat [3]. Sorghums are preferred for many foods such as flat bread, thick and thin porridges, snacks and other products [14]. However, low protein content and quality limit the widespread applications of sorghum in human foods. Thus, there is a need for sorghum-based foods with higher protein content and digestibility.

            Barley (Hordeum vulgare) is one of the most ancient of the cereal crops. After wheat, rice and corn, it is the world’s fourth most important cereal [10]  For today’s consumers, barley is a new and unique flavour alternative. The ability of barley to support good consumer health through nutritional components such as fibre (particularly β-glucan), antioxidants and B vitamins has piqued interest recently. β-glucans, which are essential contributors to dietary fibre and have significant blood cholesterol-lowering benefits, are abundant in barley. Chickpeas (Cicer arietinum L.), often known as garbanzo beans, are an ancient world pulse (i.e., edible seeds) in the legume family, that have long been used in a variety of culinary inventions due to its nut-like flavour and sensory versatility [2]. Chickpeas are available in two varieties: light seeded Kabuli and tiny dark Desi (8). Pulses differ from other plant foods in that they have higher protein content (17%–30% by dry weight). Chickpeas are a low-cost and significant source of protein for vegetarians and others who cannot afford animal protein [6]. Chickpea consumption helps to maintain good health by regulating fatty acid levels in humans.           

MATERIALS AND METHODS

Material

The ingredients used for production of ready-to-eat extruded snacks were sorghum, barley and chickpeaand were procured from the Raichur local market, Karnataka, India.For preparing the samples,all the raw materials were grinded in a hammer mill separately, to reduce the size into fine particles.

Preparation of samples

The samples were prepared using process parameters such as five distinct sorghum, barley and chickpea blends (70:15:15, 65:20:15, 60:25:15, 55:30:15, 50:35:15) at feed moisture content (8, 10, 12, 14, 16%) and extruder operational parameters such as barrel temperature (120, 140, 160, 180 and 200 ^oC) and screw speed (120, 140, 160, 180 and 200 rpm). All of the flours were weighed and the moisture content was adjusted by sprinkling water into the flours and mixing them together to make a homogeneous mixture. After mixing, the samples were kept at room temperature for 12 to 24 hours in aluminium laminated polyethylene bags. The samples were sieved and placed into a feed hopper, where they were extruded with a 7 mm die diameter and collected at the die end.

Statistics design

Central composite rotatable design (CCRD) was used to analyze the influence of four independent variables i.e., Moisture Content of Feed (%), Blend Ratio (%), Barrel Temperature (^oC) and Screw Speed (rpm) on expansion properties of extrudates i.e., longitudinal expansion index (LEI) and volumetric expansion index (VEI). A second order polynomial equation was used to fit the measured dependent variables (LEI, VEI) as a function of independent extrusion variables.

Expansion properties of extrudates

Longitudinal Expansion Index

The Longitudinal Expansion Index is the ratio of the exiting velocity of the extrudate after expansion to its velocity in the die orifice expressed by the following equation:

Volumetric Expansion Index

The Volumetric Expansion Index is the product of SEI and LEI, and it represents the extrudate’s overall expansion in both radial and longitudinal directions and it is expressed as

RESULTS AND DISCUSSION

Longitudinal Expansion Index

            The Longitudinal Expansion Index is the ratio of the exiting velocity of the extrudate after expansion to its velocity in the die orifice. From the experiment, the longitudinal expansion index (LEI) of extrudates measured for all the samples ranged from 0.64 to 1.46 mm. The effect of extrusion parameters on longitudinal expansion index of extrudates are shown in 3-D surface plots (Fig. 1 to 3).

            The coefficient of determination (R²) of various regression models for predicting the longitudinal expansion index of extrudates was 0.95. The following second order model provides a multiple regression equation that represents the effect of processing factors on longitudinal expansion index in coded values.

Positive coefficients of the first order terms of BT, SS, interaction terms and quadratic terms in equation 3 indicate an increase in longitudinal expansion index (LEI) as these variables are increased, whereas negative coefficients of the first order terms of MC, BR, quadratic terms and interaction terms indicate a decrease in longitudinal expansion index of extrudates as these variable is increased.

Fig. 3 Effect of barley level and barrel temperature on longitudinal expansion       

                            index of extrudates

            As shown in fig. 1 higher moisture content of feed led to a significant reduction in the longitudinal expansion index. Fig. 2 and 3 shows that higher percentage of barley flour in blend ratio decreased the longitudinal expansion index (LEI) of extrudates. Fig. 1 and 3 shows that longitudinal expansion index increased with increase in barrel temperature. [5]   also reported that with an increase in barrel temperature, the value of expansion also increases, because of the stretching of the molecules at higher temperature, thereby enhancing the degree of gelatinization. From fig. 2 it can be depicted that longitudinal expansion index of extrudates increased with an increase in screw speed. [7] also mentioned that increasing the screw speed can increase the longitudinal expansion of extrudates.

Volumetric Expansion Index

            Volumetric expansion index (VEI) is the product of sectional expansion index and longitudinal expansion index. So, it indicates the extrudate’s overall expansion in both radial and volumetric directions. From the experiment, volumetric expansion index (VEI) of extrudates measured for all the samples ranged from 1.17 to 3.38 mm. The effect of extrusion parameters on volumetric expansion index of extrudates are shown in 3-D surface plots (Fig. 4 to 6).            

The coefficient of determination (R²) of the various regression models for predicting the volumetric expansion index of extrudates was 0.90. The following second order model provides a multiple regression equation that represents the effect of processing factors on volumetric expansion index of extrudates in coded values.

Positive coefficients of the first order terms of MC, BT, SS, interaction terms and quadratic terms in equation 4 indicate an increase in volumetric expansion index (VEI) as these variables are increased, whereas negative coefficients of the first order terms of BR, quadratic terms and interaction terms indicate a decrease in volumetric expansion index of extrudates as these variable is increased.

            As shown in fig. 4 the volumetric expansion index (VEI) was increased up to 14%, above this temperature VEI was decreased significantly. Figures 8 and 9 shows that higher percentage of barley flour in blend ratio decreased the volumetric expansion index of extrudates. Due to the high dietary fiber content, barley flour has been observed to create low expansion [11]. From fig. 4 and 5 it can be observed that volumetric expansion index was increased with the increase in barrel temperature. In the extruder, the viscosity of melt and degree of superheating of water could have been reduced by the high barrel temperature, resulting in greater expansion [9]. It can be noted from the fig. 6 that with an increase in screw speed, there was an increase in volumetric expansion index of extrudates.

CONCLUSION

The study revealed that expansion properties of sorghum-barley-chickpea extrudates on twin screw extrusion process were dependent on the process parameters. The results showed that maximum LEI (1.46 mm) was observed with the blend ratio 65:20:15, having 10% moisture content (w.b) extruded at 180 ^oC barrel temperature and a screw speed of 180 rpmand the VEI of extrudates was found maximum (3.38 mm) at 12% moisture content, 60:25:15 blend ratio, 200 ^oC barrel temperature and 160 rpm screw speed. The results acquired in this investigation revealed that there was a positive correlation of expansion properties with barrel temperature and screw speed, and a negative correlation with moisture content and barley level.

Note: Get all equations and images here…

References

[1]. Berglund PT, Fastnaught CE, Holm ET. 1994. Physicochemical and sensory evaluation of extruded high-fiber barley cereals. Cereal Chem 71: 91–96.

[2]. Deosthale YG. 1982. Food processing and nutritive value of legumes. In: Srivastava H.C., editor. Pulse Production, Constraints and Opportunities. 1st ed. Volume 1. IBH Publishing Company; New Delhi, India: pp. 377–388.

[3]. Dicko MH, Gruppen H, Traoré AS, Voragen AGJ & VanBerkel WJH. 2006. Sorghum grain as human food in Africa : Relevance of content of starch and amylaseactivities. African Journal of Biotechnology 5(5): 384–395.           

[4]. Fellow P. 1997. Food processing technology: Principles and Practices. Wood head  

Publishing Limited, Cambridge England, pp: 267.

[5]. Guha M, Ali SZ, Bhattacharya S. 1998. Effect of barrel temperature and screw speed on rapid visco analyser pasting behaviour of rice extrudate. International Journal of Food Science and Technology 33: 259–266.

[6]. Hama, SJ. 2019. Correlation and path coefficient analysis for seed yield and yield   

components in chickpea under rain fed condition. J. Kerbala Agric. Sci. 6(1): 26-35.

[7]. Hsieh F, Peng IC, Huff HE. 1990. Effects of salt, sugar and screw speed on processing and product variables of corn meal extruded with a twin screw extruder. J. Food Sci. 55:224-227.

[8]. Huntrods D. 2013. Agriculture Marketing Research Center. Iowa State University; Ames, IA, USA.

[9]. Ilo S, Liu Y and Berghofer E. 1999. Extrusion cooking of rice flour and amaranth blends. Lebensum-Wiss u-Technol.32: 79-88.

[10]. Jadhav SJ, Lutz SE, Ghorpade VM and Salunkhe DK. 1998. Barley: chemistry and value- added processing. Crit Rev Food SciNutr38:123–171.

[11]. Köksel H, Ryu GH, Başman A, Demiralp H, Ng PKW. 2004. Effects of extrusion

variables on the properties of waxy hulless barley extrudates. Nahrung/Food48:19–24. 

[12]. Lue S, Hsieh F, Huff HE.1991. Extrusion Cooking of Corn Meal and Sugar Beet Fiber: Effects on Expansion Properties, Starch Gelatinization, and Dietary Fiber Content. Cereal Chem. 68: 227–234. 

[13]. Mercier C, Linko P, Harper JM. 1989. Extrusion Cooking, American Association of Cereal Chemists, St Paul, MN. 42:38-39.

[14]. Murty DS, Kumar KA. 1995. Traditional uses of sorghum and millets. In: Sorghum and           Millets: Chemistry and Technology; Dendy, D.A.V.; Ed.; American Association of Cereal Chemists: St. Paul, MN: 185–221.

[15]. Taylor JRN & Shewry P. 2006. Preface to sorghum and millets reviews. Journal of Cereal Science 44: 223.

[16]. Thymi S, Krokida MA, Pappa A, Maroulis ZB. 2005. Structural properties of extruded corn starch. Journal of Food Engineering 68: 519-526.