Rheological and nutritional__ quality of selected dehulled legumes blended rice extrudates.pdf
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ORIGINAL ARTICLERheological and nutritional quality of selected dehulledlegumes blended rice extrudatesS. Balasubramanian&Anjan Borah&K. K. Singh&R. T. PatilRevised: 3 November 2010 /Accepted: 18 December 2010#Association of Food Scientists & Technologists (India) 2011Abstract Rheological and nutritional quality of ready-to-eat rice (Oryza sativa) -legume viz. black gram (Vignamungo), green gram (Vigna radiata), lentil (Lens culinaris)and peas (Pisum sativum) based extrudates were studiedusing low cost collet extruder. Extrudates were preparedkeeping constant feed rate (25 kg/h) and moisture content(14% wb) at 0, 5, 10 and 15% legume incorporation levels.Rheological properties of porridge made of extrudate flourwere evaluated using Rapid Visco Analyser (RVA).Maximum and minimum peak viscosity for rice extrudatesalone and rice extrudates blended with 15% peas were 697cp and 523 cp, respectively. There was a decreasing trend indegree of gelatinization with increase in legume incorpora-tion level. Other RVA rheological parameters like troughbreak down and final viscosity were in the range of 266-226 cp, 431-297 cp and 452-375 cp respectively. Maximumvalues of protein, fat, fibre and ash contents were found inrice extrudates at 15% legumes blend levels. There was anincreasing trend in nutrient contents with legume content inrice extrudates. Degree of gelatinization for rice aloneextrudate was 29.4% and showed a decrease in gelatiniza-tion with increase in legumes extrudate and was minimum(22.4%) for rice blended with 15% dehulled green gram.Sensory evaluation scores for all extrudates showed themost acceptable range of 6 to 8. Thus, legume blend level(up to 15%) of dehulled legumes fetched good scores andshowed promising trend for the production of low costexpanded extrudates and its instant flour.Keywords Rice.Dehulled legumes.Extrudates.Sensoryquality.NutritionIntroductionExtrusion cooking is one of the useful processes for theproduction of expanded snacks and instant flours. Duringextrusion cooking, raw materials undergo high shear,thus allowing partial starch hydrolysis (Colonna et al.1984). The existing extrusion systems involve higherfinancial investment, production capacity and technicalknowledge and are not suitable for developing countries.Single collet extruders/dry extruders that were developedfor complementary foods production during early 1980sby the University of Colorado (Harper 1995, Harper andJansen 1985, Said 2000) are too costly besides highproduction capacity (about Rs 2.5 million and 1 t/h).Adoption of extrusion cooking processing for instant flourproduction in developing countries has not still picked up.Thus, application of simple machine having small pro-duction capacity is therefore of great potential interest.The possibilities of a low cost collet extruder (about 2535 kg/h) need to be studied for the production of snackfoods and instant flours. Rice (Oryza sativa), is one of themost frequently used cereals for making gluten-free foodproducts (Sivaramakrishnan et al. 2004). Legumes are aprime source of plant proteins, calories and othernutrients. Extrusion cooking of legumes increases thedigestibility of legume protein. In product development,peak and final viscosities are important parameters, tohave an understanding of product behaviour during andS. Balasubramanian (*):K. K. Singh:R. T. PatilCentral Institute of Post Harvest Engineering and Technology,PAU Campus,Ludhiana 141 004 Punjab, Indiae-mail: balaciphetA. BorahTezpur University,Tezpur 784 028 Assam, IndiaJ Food Sci TechnolDOI 10.1007/s13197-010-0206-yafter processing. Rapid viscoanalyser can be used toinvestigate the pasting effects of lipids and amino acidson rice starch and flour (Liang et al. 2002, Liang and King2003). The compact structure resulting from extrusionprocess can lead to a dense protein network reducing theavailability of starch granules to attack by alpha-amylase(Fardet et al. 1999). Moreover, the physical barrier createdby the protein network limits the accessibility of starch toamylase and delays in vitro starch hydrolysis (Hoebler etal. 1999). Various reports suggested that pasting character-istics (Wiesenborn et al. 1994, Lai 2001), rheologicalproperties of paste and gels (Wiesenborn et al. 1994, Kimet al. 1995) and other functional properties (Wotton andBamunuarachchi 1978, Zobel 1984) of starches vary withspecies and variants. Gelatinization properties of starchesdepend on the type, granular structure, botanical originand amylose/amylopectin ratio (Sajilata et al. 2006). Waxyand normal rice gelatinize between 60 and 78C(Thorburn et al. 1987, Jenkins et al. 1994). Many factorsaffect preference and acceptability of foods. Some factorsare intrinsic to the product, such as appearance, taste andflavour; other factors are extrinsic, such as social andFig. 2 Parameters of the typicalrapid visco analyzer viscosityprofile for legumes blended riceextrudatesFig. 1 Low cost collet extruderJ Food Sci Technolcultural factors (Deliza et al. 1996). Keeping above pointsin view, the present work was undertaken to studyrheological and nutritional quality of selected dehulledlegumes blended rice extrudates.Materials and methodsDifferent dehulled legumes viz. black gram (Vigna mungo),green gram (Vigna radiata), lentil (Lens culinaris) and peas(Pisum sativum) and polished rice were purchased fromlocal market. After cleaning and grading, the raw materialswere coarse ground in plate mill to make grits in theparticle size range of 1.652.36 mm. Different legume gritswere blended at 0,5,10 and 15% levels with rice grits. Formaking extrudates, about 2 kg of blended materialsconditioned to 14% (wb) moisture were used.Low cost collet extruder It is a simple single screwautogenous extruder, driven by a 7.5 kW electric motor.The barrel length is 250 mm with a length to diameter ratioof 6:1 and has a central cylindrical die of 4 mm diam and5 mm length. The rotating speed of the screw is high(500 rpm) to allow high shear. The screw configuration hasconstant pitch and flight depth to allow a progressiveincrease in friction forces and temperature inside the barrel.The screw diam is 42.5 mm and the root diam is 32.5 mm(Fig. 1). The moisture content was kept at 14%. Theextruder barrel wall has helical grooves to enhance frictionand cooking of the product. To ensure a regular feedingrate, the extruder is equipped with a motorised feedingscrew, but it was kept constant (25 kg/h) for this study.After extrusion, extrudates were ground (particle size 0.85 mm) and subjected for rheological and nutritionalanalysis.Rheological properties Pasting properties of extrudatepowders were determined using a Rapid Visco Analyser(RVA) Model 3-D (Newport Scientific Pvt. Ltd, Australia)with Thermocline software (3.0 version) by the Method No.162 (ICC 1995). Sample suspension was prepared byplacing extrudate powder (3 g) in an aluminium canistercontaining (30 g) distilled water. A programmed heatingand cooling cycle was used. Each sample was stirred(960 rpm, 10 s) while heated at 50C, and then constantshear rate (160 rpm) was maintained for the rest of theprocess. Temperature was held at 50C up to 1 min. Thenthe samples were heated (5095C, 3 min 42 s) and held atTable 1 Parameters of viscosity profileTraitsabbreviationDescription (reference of terminology)PVPeak viscosity (61-02, Bao and Xia 1999)TTrough (61-02)BDBreakdown (Bao and Xia 1999, 61-02),decreasein viscosity during cooking at 95CFVFinal paste viscosity at the end of final holdingperiod at 50C61-02 is the ICC (1995) methods010020030040050060070080002004006008001000Time (sec)Viscosity ,cpvGreen gram010020030040050060070080002004006008001000Time (sec)Viscosity,cp010020030040050060070080002004006008001000Time (sec)Viscosity,cp0%5%10%15%Pea010020030040050060070080002004006008001000Time (sec)Viscosity,cpLentilFig. 3 Typical rapid visco analyzer plot for different dehulled blended rice extrudatesJ Food Sci Technol95C for 2 min 30 s. Subsequently samples were cooleddown (95-50C, 3 min 48 s) and then held at 50C for2 min. A RVA plot of viscosity (cP) versus time (s) wasused to determine peak viscosity (PV), trough (T),breakdown viscosity (BD) and final viscosity (FV)(Fig. 2, Table 1). Each analysis was done in duplicate.Nutritional analysis Protein content (Kjeldahl method), fatand ash (Hart and Fischer 1971), and fibre (Sadasivam andManickam 1992) for different legumes blended riceextrudates were determined. Degree of gelatinization ofextrudates was done according to Wootton et al. (1971).Sensory evaluation A semi-trained panel consisting of 11members evaluated the extrudates. The sensory attributessuch as color, flavour, surface finish, taste, crispiness andover all acceptability of extrudates were evaluated using a9-point Hedonic scale (14 dislike extremely to slightly, 5-neither like nor dislike, 69 like to slightly extremely).Samples were served to panelists immediately after condi-tioning the extrudates (105C, 3 min).Statistical analysis The data reported are mean of tenobservations and subjected to MS EXCEL 2000.Results and discussionEffect of low cost collet extruder on viscosity profile ofextrudates All viscosity parameters determined decreasedwith increased legume levels in blend as compared to riceextrudates alone (Fig. 3). But the decrease was not muchpronounced in green gram based extrudate. The breakdownviscosity was maximum in peas whereas it varied in therange of 288297 cp and was lower in all the cases. Thefinal viscosity declined in all cases but the decrease wasmuch higher in green gram where it varied from 437 to 404cp. Similar observations were recorded for peak viscosityalso. When extrudates powder suspensions were heatedabove a certain temperature, water penetrated into thegranules and weakened the hydrogen bonds in starchsegments and reflected a degradative RVA profile ascompared to its corresponding raw material due tomechanical input. The viscosity increased during heatingat constant temperature (95C), continued to decreaseduring cooling and the profile finalized with a plateau fordifferent legumes and incorporation levels, but showed aslightly increasing trend at the end of the process. All theviscosity-temperature profiles of the studied systemsshowed a similar pattern. The maximum viscosity was151719212325272931051015Legumes incorporations levels,%Degree of gelatinization %Black gramGreen gramLentilPeasFig. 4 Degree of gelatinization of different dehulled blended riceextrudatesLegumesLegumes,%Protein,%Fat,%Fibre,%Ash,%Black gram08.60.860.190.5659.20.900.250.62109.80.960.270.781510.51.030.290.96Green gram08.60.860.190.5659.70.900.240.741010.10.960.260.881510.91.020.280.98Lentil08.60.860.190.5659.70.900.230.661010.10.960.250.761511.21.030.270.88Peas08.60.860.190.5659.00.900.320.66109.60.960.390.781510.21.030.500.86Table 2 Nutritional analysis ofdifferent dehulled legumesblended rice extrudatesJ Food Sci Technolattained when the granules were in their most swollen state,still intact resulting in peak viscosity and this continuedheating of paste at this point, however, caused the granuleto rupture and accompanied by the fall in viscosity(Kearsley and Sicard 1989). The secondary increase inviscosity (setback) during the cooling phase which isassociated with the retrogradation phenomenon and relatedto amylose content was observed.Effect on degree of gelatinization Degree of gelatinizationfor rice extrudate was 29.4%. The degree of gelatinizationranged from 22.4 to 29.4% (Fig. 4). The legumes blendedextrudates showed a lower degree of gelatinization com-pared to rice extrudates. Although there was no markeddifference in degree of gelatinization among the legumesblended extrudates, the black gram and green gram showedlower values (22.4% and 22.6%) followed by peas (23.3%)and lentil (23.2%) at 15%. Partial starch dextrinisation isdesirable because it reduces swelling during gruel prepara-tion, thus allowing an appropriate semi-fluid consistency tobe maintained at a higher concentration, i.e. higher energydensity. This signified that the extrusion cooking hasincreased the degree of gelatinization of the extrudates.According to Lin et al. (1997) fat content of extrudates wasshown to interfere significantly with starch gelatinization.Thus, decrease in gelatinization with legumes additioncould be due to the increased level of protein and fat ascompared to rice.Effect on nutritional value The rice (raw milled), blackgram, green gram, lentil and peas consist of 6.8, 24, 19.7,25.1 and 19.7% protein (Gopalan et al. 1991). Thecombination of rice with legume forms a protein rich food.The legumes blended rice extrudates showed a proteincontent ranging from 8.6 to 11.15% (Table 2). Among theextrudates, rice extrudates showed low protein content ascompared to legumes blended extrudates. The proteincontent increased depending upon legume type. This maybe attributed to their inherent higher content of proteins inthe legumes. The lentil blended (15%) with rice extrudateshowed highest protein content. Extrudates made of ricealone and legumes blended rice extrudate showed a lowerfat percentage ranging from 0.86 to 1.03% as compared toraw rice (0.5%) and legumes viz., black gram (1.4%), greengram (1.2%) lentil (0.7%) and peas (1.1%). There was nosignificant difference (p0.5) in fat content betweenlegumes except green gram, which showed a lower value(1.03). Fibre content of rice and legumes blended riceextrudate ranged from 0.19 to 0.50%. The fibre content ofextrudates showed an increasing trend with increase inlegume content because of the higher fibre content oflegumes than rice. Pea blended rice extrudates at higherlevel of blend showed higher fiber values. The ash contentof extrudates increased with increase of legumes levels.Ash content ranged from 0.56 to 0.98%. Black gram andgreen gram blended extrudates showed higher ash content(0.96% and 0.98%) followed by lentil (0.88%) and pea(0.86%).Effect on sensory attributes Sensory score was significantlyaffected by the blend levels in all the cases (Fig. 5).However, black gram and pea blended extrudates did notshow much variation among overall acceptability ascompared to green gram and lentil based extrudates. Thecolour was affected by the blend levels of lentil and pea,which may be attributed to the inherent colour character-Black gram13579ColorFlavourSurface finishTasteCrispinessOver allacceptability Green gram13579ColorFlavourSurface finishTasteCrispinessOver allacceptabilityLentil13579ColorFlavourSurface finishTasteCrispinessOver allacceptabilityPeas13579ColorFlavourSurface finishTasteCrispinessOver allacceptability0%5%10%15%Fig. 5 Hedonic scores of extru-dates made of different dehulledblended rice extrudatesJ Food Sci Technolistics of the legumes. However, the blend levels of blackgram (15%), peas (15%), green gram (10%) and lentil(10%) were found acceptable without altering the overallacceptability score as compared with rice extrudate alone.ConclusionThe low cost colletextruders with a small production capacitywill be suitable to process and produce legume blended riceexpanded snack foods and instant flour with low moisturecontent (14%, wb) and low lipid content. Extrudate flourswhich are partially dextrinised and gelatinized during thetreatment, yielding instant flour showed the scope forpreparation of higher energy density gruels. The lowerviscosity profile of extrudate flour as compared to its rawcomposite flour and higher nutritional and sensory valuesexpressed the usefulness and possibility of product develop-ment, especially for diet and weaning foods.ReferencesColonna P, Doublier JL, Melcion JP, De Monredon F, Mercier C (1984)Extrusion cooking and drum drying of wheat starch. I. Physical andmacromolecular modifications. Cereal Chem 61:538544Deliza R, Macfie H, Hedderley D (1996) Information affectsconsumer assessment of sweet and bitter solutions. J Food Sci61:10801083Fardet A, Abecassis J, Hoebler C, Baldwin PM, Buleon A, Berot S(1999) Influence of technological modifications of the proteinnetwork from pasta on in vitro Starch Degradation. J Cereal Sci30:133145Gopalan C, Rama Sastry BV, Balasubramanian SC (1991) Nutritivevalue of Indian foods. National Institute of Nutrition, IndianCouncil of Medical Research, Hyderabad, pp 47-4895-96Harper J (1995) Low-cost extrusion: possibilities for Africa. TheSouth-African J Food Sci Nutr 7:142147Harper J, Jansen G (1985) Production of nutritious precooked foods indeveloping countries by low-cost extrusion technology. FoodRev Int 1:2797Hart FL, Fischer HJ (1971) Anlisis moderno de los alimentas. In:Acribia, Zaragoza, p 249Hoebler C, Karinthi A, Chiron H, Champ M, Barry JL (1999)Bioavailability of starch in bread rich in amylase: metabolicresponses in healthy subjects and starch structure. Eur J Clin Nutr53:360366ICC (1995) Rapid pasting method using the Newport rapid viscoanalyser. ICC-Draft Standard No. 162, International Associationfor Cereal Science and TechnologyJenkins DJA, Jenkins AL, Wolever TMS, Vuksan V, Rao AV,Thompson LU, Josse RG (1994) Low glycemic index: Lentecarbohydrates and physiological effects of altered food frequen-cy. Am J Clin Nutr 59:706S709SKearsley MW, Sicard PJ (1989) The chemistry of starches and sugarspresent in food. In: Dobbing J (ed) Dietary starches and sugars inman: a comparison. Springer, London, pp 134Kim SY, Wiesenborn DP, Orr PH, Grant LA (1995) Screening potatostarch for n
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