Extrusion Processing of Dry Beans and Pulses

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Library of Congress Cataloging-in-Publication Data

Dry beans and pulses production, processing and nutrition / editors, Muhammad Siddiq, Mark A. Uebersax.

pages cm

Includes bibliographical references and index.

ISBN 978-0-8138-2387-4 (hardback)1. Dried beans. 2. Dried food industry. I. Siddiq, Muhammad, 1957-editor of compilation.

II. Uebersax, Mark A., editor of compilation.

TP444.B38D79 2013

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2012019772

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—

Contents

Contributors

Preface

PART I: OVERVIEW, PRODUCTION ANDPOSTHARVEST TECHNOLOGIES

1. DryBeans and Pulses Production and Consumption—An OverviewMuhammad Siddiq and Mark A. Uebersax

2. Dry Bean Breeding and Production TechnologiesJames D. Kelly and Karen A. Cichy

3. Market Classes and Physical and Physiological Characteristics ofDry BeansMark A. Uebersax and Muhammad Siddiq

4. Postharvest Storage Quality, Packaging and Distribution of Dry BeansMark A. Uebersax and Muhammad Siddiq

VII

ix

1

3

23

55

75

PART II: COMPOSITION, VALUE-ADDED PROCESSING AND QUALITY 101

5. Composition ofProcessed Dry Beans and Pulses 103Elham Azarpazhooh and Joyce I. Boye

6. Hydration, Blanching and ThermalProcessing of Dry BeansNorman J. Matella, Dharmendra K. Mishra and Kirk D. Dolan

7. Canned Whole Dry Beans and Bean ProductsBrittany L. White and Luke R. Howard

8. Extrusion Processing of Dry Beans and PulsesJose De J. Berrios, Jose Luis Ramirez Ascheri and Jack N. Losso

9. Processingof Dry Bean Flours and FractionsXin Rui and Joyce I. Boye

10. Cowpea Processing and ProductsRobert D. Phillips

129

155

185

205

235

vi Contents

11. Utilization of Dry Beans and Pulses in AfricaJose Jackson, Joyce Kinabo, Peter Mamiro, Delphina Mamiro andVictoria Jideani

12. Common Pulses: Chickpea, Lentil, Mungbean, Black Gram, Pigeon Peaand Indian Vetch

Muhammad Nasir and Jiwan S. Sidhu

PART III: CULINOLOGY, NUTRITION AND SIGNIFICANCE INHUMAN HEALTH

13. Culinary Perspective of Dry Beans and PulsesCarl P. Borchgrevink

14. Nutrition and Human Health Benefits of Dry Beans and PulsesElizabeth A. Rondini, Kathleen G. Barrett and Maurice R. Bennink

15. Chemistry and Implications of Antinutritional Factors in Dry Beansand Pulses

Shridhar K. Sathe

Index

261

283

311

313

335

359

379

Contributors

Jose Luis Ramirez Ascheri

Embrapa Food TechnologyAv. Das Americas 29501 - 23020-470

Rio de Janeiro, RJ, Brazil

Elham AzarpazhoohFood Research and Development

Centre Agriculture and Agri-FoodCanada

3600 Casavant Blvd. West

St-Hyacinthe, Quebec J2S 8E3, Canada

Kathleen G. Barrett

Institute of Environmental Health Sciences

Wayne State UniversityDetroit, MI 48201, USA

Maurice R. Bennink

Departmentof Food Science and HumanNutrition

Michigan State UniversityEast Lansing, MI 48824, USA

Jose De J. BerriosUnited States Department of Agriculture,

Agricultural Research ServiceWestern Regional Research CenterAlbany, CA 94710, USA

Carl P. BorchgrevinkThe School of Hospitality BusinessMichigan State UniversityEast Lansing, MI 48824, USA

Joyce I. BoyeFood Research and Development Centre

Agriculture and Agri-Food Canada3600 Casavant Blvd. West

St-Hyacinthe, Quebec J2S 8E3, Canada

Karen A. Cichy

USDA-ARS, Asst. Professor, Crop & SoilSciences


Kirk D. Dolan

Dept. of Food Science & HumanNutrition; Dept. of Biosystems andAgricultural Engineering


Luke R. Howard

Department of Food ScienceUniversity of Arkansas2650 N. Young AvenueFayetteville, AR 72704

Jose Jackson

Centre for Scientific Research, IndigenousKnowledge and Innovation (CesrIKI)

University of BotswanaGaborone, Botswana

Victoria Jideani

Department of Food TechnologyCape Peninsula University of TechnologyCape Town, South Africa

James D. KellyProfessor, Crop & Soil SciencesMichigan State UniversityEast Lansing, MI 48824, USA

Joyce KinaboDepartment of Food Science and TechnologySokoine University of AgricultureMorogoro, Tanzania

vii

viii Contributors

Jack N. Losso

Louisiana State University AgriculturalCenter

Department of Food Science111 Food Science BuildingBaton Rouge, LA 70803, USA

Delphina MamiroDepartment of Food Science and

TechnologySokoine University of AgricultureMorogoro, Tanzania

Peter Mamiro

Department of Food Science andTechnology

Sokoine University of AgricultureMorogoro, Tanzania

Norman J. Matella

Campari AmericaLawrenceburg, KY 40342, USA

Dharmendra K. MishraNestle (USA)Freemont, MI 49412, USA

Muhammad Nasir

Department of Food and NutritionUniversity of Veterinary & Animal SciencesLahore, Pakistan

Robert D. PhillipsFood Science & TechnologyUniversity of GeorgiaGriffin, GA 30224, USA

Elizabeth A. Rondini

Department of Food Science and HumanNutrition


Xin Rui

Bioresource Engineering DepartmentMcGill University (Macdonald Campus)21111 Lakeshore Road

Ste. Anne de Bellevue

Quebec H9X 3V9, Canada

Shridhar K. Sathe

Department of Nutrition, Food & ExerciseSciences

The Florida State UniversityTallahassee, FL 32306, USA

Muhammad SiddiqDepartment of Food Science & Human

Nutrition


Jiwan S. Sidhu

Department of Family SciencesCollege for WomenKuwait UniversitySafat, Kuwait

Mark A. Uebersax

Professor Emeritus, Department of FoodScience & Human Nutrition


Brittany L. WhiteDepartment of Food ScienceUniversity of Arkansas2650 N. Young AvenueFayetteville, AR 72704, USA

•^

8 Extrusion Processing of Dry Beansand Pulses

Jose De J. Berrios, Jose Luis Ramirez Ascheri andJack N. Losso

Introduction

Significance of extrusion in foodprocessing

Extrusion technology and systemsExtrusion-cooking technologySystem classificationEquipment and extrusion processing

operation

Overview of extruded dry beans and otherpulses

Extruded dry bean/pulse productsQuality of extruded dry bean/pulses products

Functional propertiesNutritional and health benefits

SummaryReferences

INTRODUCTION

Extrusion cooking technology is a high-temperature short-time (HTST), versatile andmodern food operation that converts agricultural commodities, usually in a granular orpowdered form, into fully cooked food products. Due to the processing flexibility offeredby extrusion cooking technology, extrusion has found important uses in the cereal and petfood industries, as well as in dairy, bakery and confectionary applications. In general, thefinal extrudate has low moisture content and is considered a shelf-stable food product(Berrios 2006; Berrios et al. 2010). The HTST cooking process significantly reduces microbial population, inactivates enzymes, and minimizes nutrient and flavor losses in the foodbeing produced.

Legume pulses such as dry beans, dry peas, lentils and chickpeas are considered one ofthe oldest known foods to mankind and second only to cereals as a source of human foodand animal feed. Also, they are used as substitute for meats and main source of complementary protein in the diets of large segments of the populations of Mexico, Central andSouth America, and other regions of the world with subtropical and tropical climates.Without legume pulses, vegetarianism, which is practiced by large populations in the world(such as India), simply would not be a viable option.

Dry Beans and Pulses Production, Processing and Nutrition, First Edition.Edited by Muhammad Siddiq and Mark A. Uebersax.© 2013 John Wiley & Sons, Inc. Published 2013 by John Wiley & Sons. Inc.

185

186 Composition, Value-Added Processing and Quality

This chapter presents acritical review of research on extrusion processing of dry beansand other pulses with emphasis on the physical, chemical, and nutritional properties ofextrudates. Further, this chapter outlines the potential utilization of dry beans and pulses-based formulations as safe, convenient, healthy, directly expanded extruded snacks andother ready-to-eat type food products.

Significance of extrusion in food processingSeveral benefits of extrusion cooking over traditional, batch cooking methods are asfollows:

• The extruder functions as acomplex and complete processing unit where ingredientsare mixed, cooked, formed and sheared in one continuous process

• Awide variety ofproducts can be produced using one single machine by varying theingredient composition in the mix and extrusion processing conditions

• The process allows precise control over the cooking parameters and processoptimization

• The process is versatile and any changes can be made quickly during cooking• The typical HTST cooking process reduces/eliminates microorganisms, inactivates

enzymes, and minimizes nutrient and flavor losses

• Extruders may be more cost-effective to operate than traditional cooking systemsbecause they perform multiple unit operations (e.g., mixing, blending, cooking,forming) in one single machine, which increases productivity and reduces productioncosts

Extrusion technology isa long-term investment, and the advantages listed above shouldallow the investors to adapt their production units. Thus, when considering extrusion as aninvestment project, manufacturers of extruded food for human consumption, pet food, oraquafeed pellets need to understand the broader implications from the technical, quality,and economic perspectives.

EXTRUSION TECHNOLOGY AND SYSTEMS

Extrusion-cooking technology

Extrusion is a mechanical process used to create objects or products of desired shapes,sizes, and texture by forcing material through an orifice ("die" opening) under pressure. Ifthe food is heated during the extrusion by external heaters in addition to mechanical friction, this process is known as extrusion cooking. Extrusion cooking is arelatively new andadvanced food processing technique, compared to traditional baking and other batch-typecooking methods. Several definitions are given by different authors, but each consistentlyrefers to the process in which starchy and/or proteinaceous materials are continuouslycooked while traversing through a cylindrical barrel. Control variables of moisture, highpressure, high temperature and shear force are used to produce a variety offoods (DeliaValle et al.1987; Mercier et all989).

According to Chinnaswamy (1993), HTST extrusion cooking is used by many sectorsofthe food industry to produce expanded snack foods, ready-to-eat (RTE) breakfast cereals

Extrusion Processing of Dry Beans and Pulses 187

(Orthoefer and Solorio 2001), and pet foods; it is also used by other non-food relatedindustries. Crispness, a typical quality attribute of all these foods, is directly related toexpansion, which in turn is dictated by various extrusion parameters (Williams et al. 2010).Alavi (2004) reported that agricultural products, which utilize extrusion technology, constitute approximately $40 billion annually in the US market alone; a sampling of suchproducts is shown in Box 8.1.

Box 8.1. Extrusion applications in food, feed,other products

HUMAN FOODS

• Cereals ready-to-eat• Snacks (salty snacks and sweets)• Baby food• Instant soups• Flour breading and batters• Textured vegetable protein• Meat substitutes

• Mixed and enriched flour

• Milk substitutes

• Bakery additives• Modified starches

• Confectionery• Massa (noodles)• Beverages in powder• Cookies and crackers

• Dietetic products, granola, etc.• Cereals, oilseeds and precooked vegetables

ANIMAL FEED

• Feed for ruminants, pigs, poultry, fish, shrimp, etc.• Pet Foods

• Food industry waste/byproducts processing:- Waste utilization of poultry, pork, beef, fish, dairy, bakery, fruits and vegetables

INDUSTRIAL USES

• Paper industry• Biofuel industry• Textile industry• Metallurgical foundries• Petroleum industry• Adhesives and binders

• Coadjutants - insecticides and fungicides• Processing of composites, biodegradable plastics, biodegradable films from food-

based materials


Table 8.1. Commercial extruders specifications/capacities for various extruded productsExtruder

typeExpanded Expanded Breadings Texture Pet foods

snacks cereals proteinAquatic

feed

TX-57 Mag 50-120 50-120 50-120 50-200 250-850 250-850TX-85 Mag 150^50 150-450 150-450 200-650 1000-2800 500-2800TX-115M 350-1100 350-1100 350-1100 350-1600 2000-6800 1250-6800TX-144M 1100-2200 750-1900 750-2200 1000-2500 6000-13200 600-13200

Capacities shown are in kg/hr units.Source: Wenger Corp, Sabetha, KS (USA).

System classification

Screws are the main components of extruders that carry out the mixing, kneading, shearingand conveying operations within a single machine. Extruders are classified by the numberof screws used (e.g., single- or twin-screw extruders). Single-screw extruders were developed in the 1940s to make puffed snacks from cereal grits and flours. Increased demandfor precooked cereals and starches in the 1960s encouraged the fabrication oflarge production capacity extruders that could handle up to 10,000 pounds ofproduct per hour. Furtherrefinement provided more versatility to food extrusion processing, allowing it to expandinto numerous other applications, which included a variety ofsalty and sweet snacks, RTEbreakfast cereals, croutons, precooked infant foods, and adiverse number ofdry pet foods.Commercial extruders ofvariable throughput are available for producing different extrudedproducts (Table 8.1).

The application of twin-screw extruders for food processing began in the 1970s, andtheir use has increased rapidly over the years. These units improve flexibility and the efficiency ofthe process. The traditional single-screw extruders are simpler in design and lesscostly than twin-screw extruders. However, the overall energy expenditure in asingle screwextruder is generally higher than in a twin-screw extruder. Further, the production life spanofsome main processing components ofthe system, such the screws and the lining oftheextrusion barrels, is less in single-screw versus twin-screw extruders. Additionally, processfunctions in a single-screw extruder are limited, particularly when dealing with complexformulations and/or processing that require high uniformity and improved mixing. Themajor advantages of twin-screw extruders over single-screw extruders include greaterversatility in handling raw materials with a wider range ofcharacteristics, higher processflexibility, and higher process consistency and productivity. Large commercial twin-screwextruders can process over 16 tons perhour of finished product. The additional cost associated with twin screw extruders is often offset by the functional benefits and higher financialreturn. Twin-screw extruders are generally used to produce foods andfeeds thatcommanda premium price.

Equipment and extrusion processing operationThe basic components ofan extruder along with processing zones and sample screw configurations are presented in Fig. 8.1. The processing section of single- and twin-screwextruders (barrel section) is divided into three main zones: the feed/mixing zone, thecooking or transition zone, and the high pressure/forming zone.

Rotatingknife

Flavor/Color

*mimHigh pressure

zone

Viscous flow

Cooking zone

(shear)

Gelaiinization

Denaturation

Plastification

COOLING/HEATING/CONVEYING

•< FEEOZONE •>-<(Raw Material andSurface Moisture

•< Compression/Feeding • •<

•4 Reacting

<

KNEADING

ZONE(Dough Like Mass)

Cooking/Melting

Kneading

Raw materials

Conveying zone

Rotating screws

< FINAL COOKING •ZONE

(Vtsco-Amorphic Mass)

•

AmorphosizingTexturizing

SH

A

P

I

N

G

Fig. 8.1. Basic components of a single-screw extruder (top), the heating zones in a single-screwextruder barrel (middle), and conical configuration in a twin-screw extruder (bottom). Middle and bottompictures reprinted with permission from Wenger Corp., Sabetha, Kansas (USA).

189


In the feed/mixing zone, the raw ingredients in the form of coarse or fine flours arecontinuously conveyed or fed from storage bin(s) into the extruder. The screws, rotatingat a high speed, mix and move the material into the cooking zone. Water, oil, or other food-grade fluids are injected through ports in the barrel to hydrate the mix before cooking. Also,in this zone, the hydrated mix is kneaded into a continuous dough by the action of thescrew(s).

In the cooking zone, the dough is subjected to convective heat (transferred directly fromthe barrel walls into the dough) and mechanical heat (generated within the barrel by varyingthe screw configurations). Depending on the desired characteristic of the final product, heatcan also be applied by injecting steam into the dough through ports located along the barrelsections.

Finally, in the high pressure/forming zone, the material under extrusion (in the molten

state) is expelled through the die section, and the product takes its shape based on thegeometry of the die. Depending on the moisture level, temperature, pressure, die size andgeometry, expanded low-moisture products (e.g., fully cooked puffs) or low-moistureformed products (fully cooked dough or pellets) can be readily fabricated. The residencetime for cooking foods and food ingredients in an extruder varies between 20 and 90 sec,with die temperatures varying between 100°C and 200°C and under pressures between4,000 and 15,000kPa (580-2,175psi).

A complete extrusion system generally consists of storage bins, dry mix feeders, liquidpumps and meters, an extruder assembly, a steam injection port, a die, and a cutter (Fig.8.2). A preconditioner unit, a dryer and a packaging system are commonly included tocomplete the overall process. With the incorporation of computer automation, extrusionprocessing can ensure consistent product quality with minimal human labor.

OVERVIEW OF EXTRUDED DRY BEANS AND OTHER PULSES

Traditionally, dehulling/decortications, splitting and sprouting are technological practicesthat reduce the cooking time of pulses and increase their digestibility (Uebersax et al. 1989).Roasting, a common practice used prior to the cooking of beans in some countries, impartsa characteristic flavor to the product and reduces overall cooking times. Lentils, green gram,and chawli (split cow peas), are some of the pulses that are roasted before cooking. Overthe past three decades, extrusion technology had been used effectively to reduce thecooking time of pulses, as well as inactivate undesirable compounds (antinutrients), improvethe textural, nutritional and sensory characteristics in the final pulse and pulse-based extru-dates. Extrusion processing variables such as temperature, feed moisture content and screwspeed are the main important parameters creating the above changes. Therefore, extrusionprocessing provides the potential for using pulses and pulse-based mixes in the fabricationof value-added food products and ingredients with high nutritional and economic values.

Extrusion processing has been used to alleviate the hard-to-cook (HTC) defect found insome bean lots, and it increases the nutritional value of the bean flours (Steel et al. 1995;

Martin-Cabrejas et al. 1999). These studies were performed using a laboratory, Brabender19-mm, single-screw extruder with limited screw profiles and a range of operating conditions. The bean extrudates showed physical and chemical characteristics similar to thoseof extrudates from fresh beans. Additionally, extrusion cooking preserved the protein nutritional value of the HTC beans. These results were largely attributed to the short heatingtime used in the extrusion cooking of the bean flours.

I


Live Bin

Preconditioner

Extruder Die/KnifeS /Assembly

Fig. 8.2. Components ofa complete extrusion system: labeled components (top) and three-dimensionalview (bottom). Reprinted with permission from Wenger Corp., Sabetha, Kansas (USA).

Edwards et al. (1994) reported extrusion characteristics of small white beans processedthrough a Werner & Pfleiderer 37-mm Continua twin-screw extruder, using three-screwconfigurations of increased energy intensity. The authors reported that as the energy intensity increased, the expansion ratio, initial or cold and hot paste viscosities increased, whilebulk density, end-point viscosity and trypsin inhibitor (TI) activity decreased. The TI activity in the extruded products was less than 15%, indicating that extrusion processing inactivated more than 85% of this antinutrient.

Van der Poel et al. (1992) had previously reported a significant reduction on antinutri-tional factors (lectin and TIs) on the flours of two pea varieties processed by extrusion.Gujska and Khan (1990), using high starch fraction (HSF) of chickpea processed on aWenger X-5 laboratory extruder at the optimum die temperature of 132°C, reported thatTI activity was reduced by about 70-85%, and hemagglutinin was completely inactivatedby the process. Balandran-Quintana et al. (1998) extruded pinto bean flours at three different die temperatures (140°C, 160°C, or 180°C), feed moisture content (18%, 20%, or 22%,wet-basis), and screw speed (150rpm, 200 rpm, or 250 rpm) using a Brabender 19-mmsingle screw extruder. The results confirmed those reported by previous researchers that


extrusion cooking was an effective processing for inactivating TI activities. Edwards et al.(1994) and Steel et al. (1995) also concluded that extrusion temperatures and feed moistureswere highly effective for increasing in vitroprotein digestibility of the bean extrudate. Theprocessingconditionsalso significantly affected bulk density, expansion and water absorption indexes of the extrudates.

Fructooligosaccharides and dietary fibers are carbohydrate-oligosaccharide fractionspresent in dry beans and other pulses. Fructooligosaccharides play an important role onproduct acceptability, since these sugars (stachyose and raffinose) are associated with flatulence, an undesirable discomfort due to gas accumulation in the lower intestine (Siddiq etal. 2006). Dietary fibers are associated with health attributes, including prevention of coloncancer. Therefore, extrusion processing has been used to reduce the concentration offlatulence-causing sugars and increase soluble dietary fiber in the extrudates. Borejszo andKhan (1992) processed pinto bean HSFs on a Wenger TX-52 twin-screw extruder at dietemperatures in the range of 110°C to 163°C, a screw speed of 300 rpm, and a feed moistureof 18.8% (wet-basis). They reported that the levels of raffinose and stachyose contents werereduced 47% and 60%, respectively, compared to levels determined in the nonextrudedsamples. The authors obtained the highest sugar reduction at the maximum process temperature of 163°C. In a related study, a further reduction of oligosaccharides in floursprepared from 85°C extruded beans was observed. The reduction was in the range of 5.09%to 11.56% for stachyose and 18.8 % to 19.8 % for raffinose (Table 8.2), which was dueprobably to shear effect rather than leaching during conventional soaking and cooking(Kelkar et al. 2012).

Berrios and Pan (2001) processed black bean flours milled at different particle sizesthrough a Werner & Pfleiderer 37-mm Continua twin-screw extruder run at screw speedsof 400 rpm, 450 rpm, or 500 rpm (with a die temperature of 160°C and feed moisture of18%). They reported that the total oligosaccharides concentration of control and extrudedbean flours was not affected by difference in particle sizes, but was reduced significantlywith an increase in screw speed (Fig. 8.3).

Gonzalez and Perez (2002) evaluated the effects of extrusion cooking (die temperatureof 150°C and a screw speed of 90rpm) and microwave irradiation (85°C, half-power of650 W for 6min) on some physical, chemical, functional, Theological and morphologicalcharacteristics of lentil starch. Both treatments significantly decreased the crude fibercontent and starch retrogradation, while increased reducing sugars and ash contents, andthe absolute density of the extrudates.

Berrios et al. (2002) processed black bean flours with sodium bicarbonate (NaHC03)added at levels from 0.0% to 2.0%, on a Leistritz 18-mm twin-screw operated at a screwspeed of 200rpm, die temperature of 160°C, and feed moisture of 20%. They reported that

Table 8.2. Effect ofextrusion processing on the reduction ofoligosaccharides of navy and pinto beanflour

Stachyose (mg/lOOg)

Navy Pinto

Raffinose (mg/lOOg)

Navy Pinto

Raw Beans Flour

Extruded (85°C) Bean Flour

2975 2569

2631 2438

925 794

741 637

Source: Nyombaire et al. (2007); Kelkar et al. (2012]

Control

3000 stc

2000- A ft ft1000

0-J\k n G Ga F

4000

3000

2000

1000

0

4000

< 3000

4000

< 3000

Time (min)

400 rpm

10 12 14

I \I \ st1 u c

/ \ R1 1 —i— 1 1

8

Time (min)

450 rpm

Time (min)

500 rpm

10 12 14

Time (min)

Fig. 8.3. HPLC sugars profile in control black bean flours and black bean flours extruded under different screw speeds (St: stachyose; R: raffinose; C: cellobiose; G: glucose; Ga, galactose; F: fructose).

193


extrusion conditions and NaHCO, addition reduced the levels of stachyose and sucrose inthe extrudates, compared to levels determined in the nonextruded samples. Berrios et al.(2002) observed a decrease in insoluble fiber (IF) and an increase in soluble fiber (SF),which confirms that extrusion processing causes a redistribution of the IF to SF fractions,which is in agreement with results of previous studies (Bjorck et al. 1984; Lintas et al.1995; Gualberto et al. 1997). These results were contrary to Artz et al. (1990), who did notobserve changes in fiber modification resulting from extrusion processing. The fiber fraction redistribution possibly resulted from hemicellulose depolymerization. A considerableredistribution of IF to SF occurred as result of extrusion, although total dietary fiber didnot change (Martin-Cabrejas et al. 1999).

Recently, Berrios et al. (2010) evaluated the changes in sugar fraction and dietary fibercomposition of lentil, dry pea, and garbanzo flours as an effect of extrusion cooking. Forthis study they used a Clextral EVOL HT32-H twin-screw extruder run at a screw speedof 500rpm, die temperature of 160°C, and feed moisture of 17%. They reported that extrusion processing decreased the concentration of raffinose in dry pea, chickpea and lentil,and the total available carbohydrates (TAC) in garbanzo extrudates. However, extrusionprocessing did not significantly affect the TAC content of dry pea and lentil flours.

Expansion is one of the most important properties of food products obtained throughhigh-temperature, low-moisture extrusion cooking. Extrudate expansion is a complex phenomenon that occurs as a consequence of several factors and mechanisms, influenced byfeed composition and extrusion processing parameters (Patil et al. 2007). The fabricationof manysnacksand RTEfoods are in the form of expandedproducts, as expansionprovidesa desirable mouthfeel related to the textural characteristic of a crispy product. Bhattacharyaand Prakash (1994) developed an extruded snack from three blends of rice and chickpeaflours (100:0, 90:10, or 80:20) using a single-screw extruder, at three different die temperatures (100°C, 125°C, or 150°C). They indicated that incorporation of chickpeas into therice flour provided poor texture to the extrudate as there was a decrease in product expansion and an increase in bulk density, shear and breaking strength, with increased additionof chickpea flour into the mix. Also, Shirani and Ganesharanee (2009), using a similarrange of extrusion temperatures and mixtures of rice and chickpea flours, reported similarresults. They added that the poor expansion and texture observed with increased inclusionof chickpea in the mix may be attributed to the high protein and dietary fiber contents inchickpea as compared to that of rice. This confirms what Faubion et al. (1982) reportedfor cereal snacks. They indicated that higher protein in cereals decreased expansion of thefinal product.

Using a different approach, Batistuti et al. (1991) made use of defatted chickpea flourto promote expansion of the extrudate. They optimized the extrusion conditions by responsesurface methodology (RSM) and demonstrated that expansion ration increased steadilywith a decrease in feed moisture. Optimum product was obtained at a die temperature of132°C, feed moisture of 13-14%, and a screw speed of 200rpm. The authors indicated thatthe defatted chickpea extruded snack was rated higher than a commercial corn snack.Berrios and Pan (2001) evaluated the effect of the particle size of the flour and extrusionconditions on expansion of the extrudate. Black beans were ground to obtain flours withparticle sizes ranging from 0.85 mm to 2.28mm in diameter and then processed through aWerner & Pfleiderer 37-mm Continua twin-screw extruder run at a constant die temperature(160°C), and feed rate and water content of the feed (25 kg/hour at 18% moisture). However,the screw speed was run at 400 rpm, 450 rpm, or 500 rpm. They reported that the expansion


ratio and percentage torque, within the different particle sizes evaluated, increased with anincrease inscrew speed. The finer pin-milled flours (< 35mm diameter) extruded at500rpmdemonstrated greater expansion.

Lai et al. (1989) and Mercier et al. (1989) reported that by increasing extruder screwspeed, the expansion ratio of the extrudate material also increased. On the other hand,Chauhan and Bains (1985) reported that the larger the particle sizes of wheat flour, thegreater the expansion. The differences among the reported results may be due to the differences in rawmaterials andextruder typeandprocessing conditions used in thesestudies.Berrios et al. (2002) reported that the expansion ratio increased 1.6-fold at the nod and1.4-fold at the area between the nods, between the control extrudate and the extrudate witha 0.1% NaHC03 addition. These differences increased to 2.0- and 1.8-fold for extrudateswith a 0.5% NaHC03 addition at the same indicated areas. Theyalsostated thatdifferencesinthe expansion distribution pattern on an extrudate would be important to consider inthefabrication of particular snack-type products (Berrios et al. 2004).

Meng et al. (2010) developed an expanded chickpea flour-based snack-type productusing a corotating W&P ZSK-57 twin-screw extruder run at screw speed, die temperatureand feed moisture in the range of 250-320rpm, 150-170°C, and 16-18%), respectively.The expansion ratio of the extrudates was in the range of 3.06 and 4.99, similar to thosereported for other pulses extruded under similar conditions (Patil et al. 2007; Berrios etal.2002; 2004; 2010), and those reported for cereal-based extrudates (Ilo et al. 1996; Singhand Smith 1997). Additionally, the extrudates had low bulk density and hardness. Theoptimized products were obtained at low feed moisture, high screw speed, and medium tohigh barrel temperature. The results of the presented studies show that pulses can beextruded into value-added nutritious RTE snacks with desirable expansion and texturalproperties.

EXTRUDED DRY BEAN/PULSE PRODUCTS

Extrusion is an effective cooking technology used commercially to produce high-valuesnacks and breakfast foods based on cereals such as wheat or corn. However, despite thelarge number of experimental reports on the extrusion of pulses, up to now, extrusionprocessing has not been commercially used for adding value to legume pulses. Directexpanded snacks and breakfast-type foods made by extrusion processing are classified assecond-generation products. These products are characterized for having a crispy textureand low bulk density. Direct expanded products cover a large variety of recipes, formulations and shapes, and can be made into commercialized functional foods that are high inprotein and dietary fibers, low in calories, and gluten-free.

Pulses with remarkable nutritional profiles and healthy attributes are truly functionalfoods. However, direct expanded, RTE, extruded pulses andpulse-based food products arenot yet available in the marketplace. There are only a few patents and patent applicationsthat have the potential to be used by the food industry, especially for pulse-based healthyfood alternatives to secure a sector of the market that is occupied today by snacks that arehigh in calories, low in protein and dietary fibers, and high on the glycemic index.

Baker and Krueger (1999) described extrusion conditions toprocess legumes into crispcurls, puffs and chips. Some limitations of this invention are the use ofa precooking stepand the need foradditional drying of the final products, made at a relatively high moisture


content (10-40%). The precooking is not only a time-consuming process, but also energyconsuming when coupled with extrusion cooking. Additionally, this step leads to physical,chemical and nutritional changes in the final product. Barnett et al. (2008) described theinvention of an extruded legume snack food comprising an extruded puff product based ona dried legume powder mixed with a starch, extruded, and then shaped into a facsimile ofthe natural starting material, such as a pea pod. Their claim is very specific to cover thefuture international niche market of such a shaped product. Berrios et al. (2008) reportedthe invention of an extrusion process for producing uniform and highly expanded pulse-based food products. The researchers explained the developed methods to create puffy,crunchy snack foods from powdered legumes, potato starch and apple fibers, among othernatural ingredients. The snack foods contain more protein and fiber than traditional starchysnacks and their low moisture content made them shelf-stable food products. Severalbreakfast-cereal-type foods and snacks that come in a variety of shapes, from crisp bitsand balls to tubular puffs, were developed under the invention (Fig. 8.4). These convenientfood alternatives have already proven popular with 550 tasters who were encouraged totry the products at a Lentil Festival in 2006 in Pullman, Washington, USA.

The rise in consumer demand for convenience foods, health awareness and the role of

pulses in meeting these demands could provide economic incentives to interest commercialfood companies in providing consumers worldwide with better food alternatives in a convenient form.

If 10% of the $16 billion US snack food market could be captured by legume-basedextruded snack foods, it would be possible to capture a $1.6 billion market that did notexist before for legumes. But more importantly, the new products, which contain threetimes as much protein and five times as much dietary fiber as extruded snack foods on themarket today, would provide consumers with healthier food options.

Fig. 8.4. Selected extruded products from beans/pulses.


QUALITY OF EXTRUDED DRY BEAN/PULSES PRODUCTS

Functional properties

Functional properties are physical and chemical properties that affect the behavior of aningredient in food systems during processing, storage, preparation, or consumption (Kin-sella 1976). Since pulses are rich sources of proteins and carbohydrates, extrusion has asignificant effect of the functionality of the extruded products. Functional properties ofextruded pulses are determined by their protein, carbohydrate, water, lipid, and to a lesserextent their micronutrient composition. Water solubility, water binding, fat binding, emul-sification, foaming, gelation, thickening, and flavor binding are the common functionalproperties affected by extrusion processing. There is extensive data reported on the functional properties of nonextruded beans and pulses as reported by Boye et al. (2010) andMa et al. (2011). This section focuses on the physical and chemical functional propertiesof pulses after extrusion.

Physical and chemical properties of extruded products are dramatically altered by extrusion. Functionalproperties of extruded products include degree of expansion index, density,color, and microstructure. Table 8.3 presents the effect of extrusion conditions on selectedfunctional properties of red kidney beans. The degree of expansion (ratio of product-to-diedimensions) or puffing is an important physical characteristic of extrudate. The degreeof expansion affects product density, fragility, and tenderness (Conway and Anderson1973; Gujska and Khan 1991a, 1991b). Increased protein content significantly decreasesthe expansion of the protein-starch blend except when the starch composition in themixture is 70% or more (Gujska and Khan 1991a). This general trend has been observedwith other starch-based food products such as cereals. However, protein type tends toincrease the bulk density of extruded pulse products. In some cases including blends ofpulses and cereal, increasing protein concentration led to an expanded product (Faubionand Hoseney 1982). However, a high negative correlation between protein level and expansion ratio was obtained when navy bean proteins were mixed with cereal proteins (Gujskaand Khan 1991c). Moisture content, temperature and screw speed can affect the physicalproperties of extruded pulses. The screw speed rate can also affect the extruded productdensity, and studies have shown that the expansion rate can increase significantly with lowfeed moisture, increased screw speed, and barrel temperature before it reaches a criticallevel (Meng et al. 2010; Dogan and Karwe 2003; Ilo et al. 1996). Increased temperaturecauses excessive structure breakdown and starch degradation due to starch dextrinization.Increased feed moisture, screw speed and barrel temperature can increase product bulkdensity.

The water solubility index (WSI) is defined as the amount of dry solids recovered byevaporating the supernatant from the water absorption test (Lazou et al. 2010). In the samestudy using a corn-lentil mixture, it was reported that the WSI decreased with increasedfeed moisture content, while temperature increase had an inverse effect. In general, becauseof heat-induced denaturation and insolubilization of pulse proteins during extrusion, theWSI of extruded pulses decreases (Gujska and Khan 1991b).

Water absorption index (WAI) is an indication of the ability of an extruded product toabsorb water. The availability of hydrophilic groups in the extruded product is a criticalfactor for the WAI. The WAI is affected by the extruded product moisture content, theextrusion temperature, and the feed rate. In corn-lentil extrudate, the WAI increased withextrusion temperature and feed moisture (Lazou et al. 2010).

00

Tab

le8.

3.Ef

fect

ofex

trusio

npr

oces

sing

onth

eex

pans

ion

ratio S

crew

speed

Ba

rrel

Tem

pera

ture

(°C

)

12

0/1

05

13

0/1

15

Mo

istu

re

co

nte

nt

(g/1

00

g)

25 36 25 36

Sour

ce:

Nyo

mba

ireet

al.

(201

1|

Feed

ra

te

(g/m

in)

SO

12

0

so

12

0

so

12

0

so

12

0

bulk

dens

ity,w

atera

bsor

ption

index

,and

water

solub

ility

index

oflig

htred

kidne

ybe

ans

(rp

m)

ns

1S

4

25

3

11

8

1S

4

25

3

11

8

IS4

25

3

11

8

IS4

25

3

11

8

18

4

25

3

UK

18

4

25

3

11

8

18

4

25

3

11

8

IS4

25

3

Exp

an

sio

nra

tio

1.2

3

1.3

0

1.3

5

1.2

6

1.3

4

1.2

9

1.1

8

1.1

9

1.2

2

1.3

2

1.3

6

1.3

5

1.2

7

1.21

1.2

5

1.2

4

1.2

2

1.3

7

1.1

4

1.1

5

1.2

1

1.2

4

1.2

4

1.3

1

Bu

lkd

en

sity

(g/m

L)

39

.7

38

.6

38

.6

41

.0

40

.4

40

.0

40

.7

40

.7

38

.8

40

.2

40

.2

40

.7

40

.5

39

.3

37

.4

36

.7

36

.9

37

.2

39

.4

40

.3

39

.1

40

.1

40

.1

38

.4

Wa

ter

ab

sorp

tio

nin

dex

5.3

3

5.3

5

7.8

6

5.7

9

6.5

2

5.6

8

4.6

1

4.8

8

4.9

5

6.5

4

8.4

4

4.8

8

5.3

8

4.4

1

5.3

7

5.9

4

5.3

9

5.6

8

5.0

5

5.0

6

6.1

9

4.9

7

6.1

1

5.6

8

Wa

ter

solu

bil

ity

ind

ex

18

.92

19

.08

20

.16

20

.62

22

.42

23

.08

16

.02

15

.30

17

.18

16

.34

17

.88

19

.72

18

.14

20

.84

21

.56

22

.02

24

.54

23

.76

16

.56

17

.86

16

.10

16

.08

18

.92

20

.90


Oil/fat absorption capacity:. Increased moisture content decreases fat absorption, whileincreased temperature increases fat absorption by a physical entrapment mechanism (Kin-sella 1976). The potential of nonpolar interaction between the oil and nonpolar side chainsof proteins cannot be excluded in this type of environment but needs to be substantiatedthrough specific studies.

Foaming and emulsifying properties: Protein solubility or solubility of the emulsifyingagent is a critical factor that influences the emulsifying capacity of an emulsifier. Duringextrusion, proteins in the beans or pulses are exposed to high temperatures for a relativelyshort time. High temperatures used in extrusion are known to unfold and denature proteins,causing a decrease in solubility and protein aggregation. An increase in protein aggregationoften leads to a reduction in emulsifying capacity for the ingredient. Generally, publisheddata show that protein from extruded dry beans and other pulses have a low emulsifyingability.

Nutritional and health benefits

The nutritional benefits of pulses have been established; however, the nutritional benefitsof extruded pulses are still a topic of investigation because several aspects involving thedevelopment of extruded pulses need to be considered when reporting on their healthbenefits. Dry beans and other pulses are valuable sources of protein, carbohydrates, dietaryfibers, minerals and vitamins. Therefore, they are nutrient-rich source of foods for humanconsumption around the world. The use of heat, pressure and mechanical shear inherent inthe extrusion processing can have either positive or detrimental effects on individual components or the complexes generated. The health considerations of extruded beans andpulses can be summarized as follows:

Inactivation of lectin bioactivity: Lectins, which cause agglutination, are destroyed attemperatures > 85°C (typical of extrusion), suggesting that lectins are not present in well-cooked beans or pulses (Bonorden and Swanson 1992). These authors showed that thermalinactivation of the lectin in the whole seed is a biphasic, first-order reaction mechanism.Nyombaire et al. (2011) reported a 90-94.5% reduction of lectin activity in red kidneybeans extruded under varying process conditions including barrel temperature, screw speed,feed rate, and moisture content (as outlined in Table 8.3).

Improved dietaryfiber content: The literature has well established that pulses are amongthe best food sources of dietary fibers. Recent studies have indicated that during extrusionof pulses, the concentration of flatulence-inducing oligosaccharides decreases while thelevels of dietary fiber increase, thus suggesting that extrusion of pulses can have beneficialhealth effects by increasing the concentration of dietary fiber in the extruded food product(Berrios et al. 2010; Tiwari and Cummins 2011). Soluble dietary fibers are degraded in thelarge intestine into short-chain fatty acids that are beneficial for colon health and haveshown anticarcinogenic activities. Insoluble dietary fibers are degraded slowly and providebulk that can help reduce the risk of cancer in the colon.

Development of resistant starch: During cooking of pulses, starch is partially modifiedinto resistant starch (Mahadevamma et al. 2004; Faraj et al. 2004). Pulses in generalhave a low glycemic index and high retrogradation rate due to their high amylose content.Extrusion has shown to increase the content of resistant starch in the extruded pulses.The development of resistant starch along with the high retrogradation rate of pulsessuggest that extrusion technology enhances the health benefits of pulses by developingproducts that can better fit individuals with physiological problems such as diabetic patients.


Prebiotics are nondigestible food ingredients that can stimulate the growth of beneficialbacteria in the gut. Because pulses are rich in dietary fiber and extrusion technologyincreases the levels of resistant starch in extruded pulse products, it is suggested that extrusion process enhances the prebiotic properties of pulses.

Phenolic compounds: Pulses are rich in complex phenolic compounds: flavonoids,tannins, phenolic acids, and proanthocyanidins. Heat treatment leads to polymerization ofphenolic compounds. While most phenolic compounds do not degrade during heat treatment, however, they tend to polymerize. Increased polymerization often leads to decreasedbioavailability, which is an important factor associated with bioactivity of pulses. The effectof extrusion on phenolic compounds needs further research to fully delineate the occurrenceof phenolic-protein complex formation and subsequent reduced protein digestibility.

Improved nutrient bioavailability: While heat treatment has shown to improve micro-

nutrient bioavailability (Alonso et al. 2001), in the context of extruded, and given thecomposition of the extruded product, data are needed to demonstrate that extruded pulseproducts have higher available minerals than unextruded counterparts. Reduction in essential amino acids and vitamins can occur when extrusion is carried at temperatures higher

than 100°C. A significant reduction as low as 10% of essential amino acids has beenreported (Frias et al. 2011). Pulses are good sources of vitamins B, and B2, and these vitamins can be reduced by as much as 50% during extruding cooking (Frias et al. 2011).

Favism: A condition that causes acute hemolytic anemia in susceptible individuals andneeds to be removed. Germination often takes care of favism factors (Carbanaro 2011).

It is unclear what the long-term implications and the public health impacts of the traditional antinutrients (antitrypsin, alpha-amylase inhibitors, and phytic acid) are with respectto extrusion and conventional cooking.

SUMMARY

Extrusion cooking is widely used commercially to produce high-value expanded breakfastand snack foods based on cereals such as wheat, rice, or corn. However, up to now, thisprocessing has not been commercially used for adding value to dry beans and other pulses.This may be due to market cost factors involving the use of pulses and in part due to limitedknowledge about the functionality of their food components, and the perception that pulsesmay not produce a quality product as those made with cereals. The reviewed scientificliterature presented here demonstrates that extrusion-cooking technology offers greatpotential for the fabrication of value-added food products from dry beans and pulses. Theextrusion process enables the use of underutilized and undervalued hard-to-cook andnormal (fresh) dry beans and other pulses. Extrusion potentially overcomes the undesirableproperties of hardened beans, improving their nutritional value by decreasing cooking timeand inactivating undesirable antinutrients. Among many benefits, extrusion has shown tobe an effective process to modify the physical functionality (expansion index, density,color, and microstructure) and chemical properties (water solubility index, water absorptionindex, oil/fat absorption capacity, and foaming and emulsifying properties) in the finalextrudate. The nutritional attributes of pulses have been clearly established, and furtherpotential for enhanced nutritional benefits is a topic of investigation. The reviewed literature also indicates that extrusion processing offers great potential for the development ofvalue-added, quick-cooked, expanded, tasty, healthy, nutritious, safe and convenient snacksand ready-to-eat products. Extrusion enables the production of foods with reduced intestinal


gas-producing oligosaccharides from dry beans and pulses. Various patents and patentapplications describing the use of extrusion processing for the fabrication of value-addedfoods from pulses are available to be used by the food industry, especially, for makinghealthy, pulse-based food alternatives to high caloric, low protein and dietary fiber, andhigh glycemic index snacks and breakfast-type extruded foods.

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Extrusion Processing of Dry Beans and Pulses