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Keywords:SurimiFish gelatinGelMechanical propertiesAlaska pollock

it is mainly obtained from pork skin, and beef skin and bones(Badii & Howell, 2006; Choi & Regenstein, 2000; Larrazabal &Camacho, 2008). However, sh gelatin has gained importance inrecent years due to several factors, including the bovine

Gomez-Guillen, 2000), Alaska pollock surimi processing byproducts(Kim & Park, 2004), Alaska pollock (Zhou & Regenstein, 2004; 2005),dover sole (Solea vulgaris) (Gimenez, Gomez-Guillen, & Montero,2005), yellown tuna (Thunnus albacares) (Cho, Gu, & Kim, 2005),brown backed toadsh (Lagocephalus gloveri) (Senaratne, Park, &Kim, 2006), skate (Raja kenojei) (Cho, Jahncke, Chin, & Eun, 2006),North Sea horse mackerel (Trachurus trachurus) (Badii & Howell,2006), brownstripe red snapper (Lutjanus vitta) and bigeye snapper(Priacanthus macracanthus) (Jongjareonrak, Benjakul, Visessanguan,

* Corresponding author. Department of Food Science and Technology, UAMReynosa-Aztlan, Universidad Autonoma de Tamaulipas, Apdo Postal 1015, Reynosa,Tamaulipas 88700, Mexico.

Contents lists availab

Food Hydr

ls

Food Hydrocolloids 23 (2009) 24462449E-mail address: gvelazquez@uat.edu.mx (G. Velazquez).The connective tissue of animals is formed mainly by collagen.This brous protein has a specic secondary structured (triplehelix), which confers strength to the connective tissue matrixwhich includes all the myobril cells allowing the coordinatedaction of moving. Collagen is also abundant in skin and bones ofmammalians, birds and shes. Collagen can be subjected to mildacid or alkaline hydrolysis to obtain gelatin, a protein widelyused in the food, cosmetic and pharmaceutical industry. Theestimated world usage of gelatin is 200,000,000 kg per year and

issues in some countries and markets. Another important factorfor the increasing interest in obtaining gelatin from sh isbecause the extraction of gelatin from the sh skin reduces theecological impact of wasting the skin, which is a major byproductof the sh-processing industry (Choi & Regenstein, 2000; Gil-senan & Ross-Murphy, 2000).

There have been several studies dealing with mechanical andphysicochemical properties of sh gelatins obtained from severalsh species. The properties of sh gelatin from different specieshave been reported: megrim (Lepidorhombus boscii) (Montero &1. Introduction0268-005X/$ see front matter 2009 Elsevier Ltd.doi:10.1016/j.foodhyd.2009.07.002most important attributes of surimi are gelling and whiteness. The objective of this work was todetermine the effect of using sh gelatin as an additive in surimi to improve the mechanical andfunctional properties of gels. Surimi gels were prepared by mixing grade A or FA surimi (Alaskapollock) with salt (20 g/kg w/w) and commercial sh gelatin at 0 (control), 5, 7.5, 10, or 15 g/kg (w/w)previously dissolved in water (200 mL/kg surimi). The solubilized paste was incubated at 40 C for30 min followed by cooking at 90 C for 15 min. Changes in mechanical properties (torsion test),a functional property (expressible water content) and color attributes of surimi gels were measured.Grade FA surimi gels containing 7.515 g/kg of sh gelatin showed an improved expressible moisture.However, gelatin added at 15 g/kg showed a disruptive effect detrimental to the mechanical prop-erties. Color parameters were modied slightly. Whiteness attribute as affected by increasing the shgelatin was instrumentally detected but not observed by sensory panelists. Gelatin did not change theoverall color attributes and all gels remained in the grayish region. These results indicated that shgelatin did not have an advantage for using as a functional additive in Alaska pollock surimi gradesA or FA. However, it can be used at up to 10 g/kg without a negative effect on the mechanicalproperties.

2009 Elsevier Ltd. All rights reserved.

spongiform encephalopathy (BSE) crisis and religious and socialAccepted 15 July 2009

sh gelatin as a food additive is increasing due to its increased commercial availability. Surimi iswashed minced sh meat used as the raw material for seafood analogs like crabmeat substitutes. TheArticle history:Received 16 July 2008

Fish gelatin is a food additive obtained after hydrolysis of collagen from sh skin. The importance ofEffects of adding sh gelatin on Alaska

Araceli Hernandez-Briones a, Gonzalo Velazquez a,b

aDepartment of Food Science and Technology, UAM Reynosa-Aztlan, Universidad Autonb PMB 374, 501 N. Bridge St., Hidalgo, TX 78557, United StatescArea Tecnologa de los Alimentos, Facultad de Veterinaria, Universidad de Santiago de

a r t i c l e i n f o a b s t r a c t

journal homepage: www.eAll rights reserved.llock surimi gels

Manuel Vazquez c, Jose A. Ramrez a,b

de Tamaulipas, Apdo Postal 1015, Reynosa, Tamaulipas 88700, Mexico

postela, Carballo Calero s/n, 27002 Lugo, Spain

le at ScienceDirect

ocolloids

evier .com/locate/ foodhyd

containing water-ice for cooling. Prior to testing, sh gels were

2.3. Expressible water content

The expressible water content (EWC) for each treatment wasmeasured using the procedures described by Uresti, Lopez-Arias,Gonzalez-Cabriales, Ramrez, andVazquez (2003) and implementedas follows. Triplicate samples (30.2 g) of solubilized surimi gel thatwere not subjected to the torsion test, were placed between twolayers of Whatman n1 lter paper (Whatman plc, Kent, UK), wereloaded at the bottom of 50 mL centrifuge tubes and centrifuged at1000 g for 15 min at 4 C (Hermle Labortechnike Model Z383,Gosheim, Germany). Immediately after centrifugation, the solubi-lized surimi gel samples were carefully separated from the lterpaper and reweighed. The EWC was calculated as follows:

EWC Wi WfWi

*100

where, Wi and Wf are the initial and nal sample weights,respectively.

2.4. Color

Spectral reectance of surimi gels was determined following the

Hydrocolloids 23 (2009) 24462449 2447removed from the tubes and stored overnight at 4 C in poly-ethylene bags to avoid dehydration.

2.2. Torsion test

Surimi gels were kept at room temperature (w20 C) for 40 minbefore the torsion test. Gels were cut at 3 cm length and milled intoan hourglass shape with a diameter of 1 cm in the centre usingspecial equipment designed in our laboratory (patent pending).Each milled sample was thenmounted and xed in a special xtureof a Brookeld digital viscometer (Model 5XHBTD, BrookeldEngineering Laboratories, Inc., Stoughton, MA, USA) following theprocedure of Lanier and Lee (1992). The sample was twisted at2.5 rpm to failure while a computer recorded the plot of torqueversus angular rotation (deformation) produced. From this plot, thepeak torque and angular deformation at failure (breakage) wasobtained for each sample using the software provided with theviscometer. Under these conditions, the shear stress and shearstrain at the failure were calculated as described by Hamann,Amato, Wu, and Foegeding (1990). All analyses were performedsh gelatin as an additive in surimi to improve the mechanical andfunctional properties of gels.

2. Material and methods

2.1. Solubilized sh pastes and gels

Commercial grade A and FA frozen Alaska pollock (Theragrachalcogramma) surimi (Pacic Surimi Joint Venture L.L.C., War-renton, OR, USA) thawed overnight (4 C) was cut into smallpieces before solubilization. Surimi paste samples (500 g) wereprepared in a 5.5 L capacity Hobart cutter (Model 84 145, Troy,OH, USA) by mixing commercial surimi for 4 min with 20 g salt/kg(w/w) and commercial sh gelatin (Gelatin Rousselot 275 FG,Rousselot SAS, Courbevoie, France) at 0 (control), 5, 7.5, 10, or15 g/kg (w/w) previously dissolved in water (200 mL/kg surimi).Rousselot gelatins at temperature above 35 C give solutionswith a viscosity ranging from 1.5 to 5 mPa s and the melting pointwas 2335 C. The nal chopping temperature was kept below15 C. The paste was stuffed into stainless steel tubes (internaldiameter 20.8 mm; length 175 mm; self-manufactured)previously sprayed with commercial vegetable oil to preventsticking. The tubes were capped before immersion for 2 h at 40 Cfollowed by immersion for 15 min in a water bath at 90 C andthen immediately placed for 30 min in a 45 C water bathProdpran, & Tanaka, 2006a; Jongjareonrak, Benjakul, Visessanguan,& Tanaka, 2006), Atlantic salmon (Arnesen & Gildberg, 2007) andgrass carp (Catenopharyngodon idella) (Kasankalaa, Xuea, Weilonga,Honga, & He, 2007).

Several studies about applications for sh gelatin in the foodindustry have been published recently. Surh, Decker, and McCle-ments (2006) reported theuse of sh gelatin as a food emulsier andAvena-Bustillos et al. (2006) reported a study dealing with lmsfrom sh gelatins. Other authors studied the mechanical and phys-icochemical properties of sh gelatin modied by adding microbialtransglutaminase, inducing covalent cross-linking between adja-cent protein chains (Fernandez-Diaz, Montero, & Gomez-Guillen,2001; Jongjareonrak, Benjakul, Visessanguan, Prodpran, et al., 2006;Ko1odziejska, Kaczorowski, Piotrowska, & Sadowska, 2004). A newapplication for sh gelation could be its use as an additive in surimiprocessing. No studies have been published about this application.

The objective of this work was to determine the effect of using

A. Hernandez-Briones et al. / Foodwith six replicates for each treatment.procedures described by Uresti et al. (2003) using a HunterLabMiniScan XE Plus spectrocolorimeter (Model 45/0-L, Hunter Assoc.,Reston, VA, USA) calibrated against black and white tiles. L*, a*, andb* values, chroma (C* [a*2 b*2]1/2), hue angle (H* arc tan b*/a*)and whiteness {W 100[(100L)2 a2 b2]0.5} were calculatedbased on illuminant C and the 2 standard observer (Shie & Park,1999). Six samples were evaluated for each treatment using all thecontent of a gel tube to measure the color.

2.5. Statistical analysis

Statistical analysis was performed using Statgraphics 5.0(BitstreamInc., Cambridge,MA). LSDsmultiple range testswereusedto determine signicantly differences (P 0.05) among treatments.

3. Results and discussion

Commercial sh gelatin from 0 (control) to 15 g/kg was addedinto Alaska pollock grade A or FA surimi paste before the cookingtreatment and the changes in functional and mechanical properties

0

0.5

1

1.5

2

2.5

0 5 7.5 10 15Fish gelatin (g/kg)

Gam

ma

Surimi grade ASurimi grade FA

0

40

80

120

160

Tau

(KPa

) A

B

a a a a a

a a a a a

a a a,b a,bb

aa,b b,c

b,c b,c

Fig. 1. Effect of sh gelatin on shear stress at failure (tau) and shear strain at failure(gamma) of surimi gels. Mean values of six replicates with bars showing standard

deviation. Different letters indicate signicant differences between treatments(P 0.05).

The effect of adding sh gelatin on expressible water of surimigels is shown in Fig. 2. The amount of extracted water increasedfrom 5.8 to 8.8% in grade A surimi gels and decreased from 6.3 to5.2% in grade FA surimi gels. Grade A surimi gels containing 7.515 g/kg of sh gelatin showed signicantly higher values ofexpressed water than control (P 0.05), indicating that theseconcentrations of sh gelatin induced a loss in the water holdingcapacity (WHC) of gels. On the other hand, grade FA surimi gelscontaining 7.515 g/kg of sh gelatin showed signicantly lowervalues than control, indicating a benecial effect.

Different additives have been reported as being appropriate forimproving the mechanical properties of surimi gels. Such additiveshave different mechanism of action associated with their benecialeffect. Velazquez et al. (2007) reported that the increase inmechanical properties of surimi by adding 020 g/kg of soluble

Fish gelatin (g/kg)

Expr

essib

le w

ater

(%)

0 2.5 5 7.5 10 12.5 15

Surimi grade A

Surimi grade FA

a

b

a,ba,b a,b a

a,b

b b b

0

3

6

9

12

Fig. 2. Effect of sh gelatin on expressible water content of surimi gels. Mean values of

A. Hernandez-Briones et al. / Food Hydrocolloids 23 (2009) 244624492448as well as color attributes of the surimi gels as affected by shgelatin concentration were measured.

Changes in torsion test parameters are shown in Fig. 1. Shearstress at failure values ranged from 89 to 92 in grade A surimi gels,and from 150 to 113 in surimi grade FA surimi gels. The shear strainat failure ranged from 1.4 to 1.6 kg and from 2.31 to 1.93 in grade Aand FA surimi gels, respectively. Shear stress decreased signicantlyby adding 15 g/kg of sh gelatin in both grade A and FA surimi gels.The shear strain values of surimi gels were not affected signicantly(P 0.05) in grade A surimi gels by adding 515 g/kg of sh gelatin.However, in grade FA surimi gels shear strain at failure decreasedsignicantly after adding 10 g/kg.

Several hydrocolloids including proteins and carbohydrates havebeen used to improve the mechanical properties of surimi and shgels. Starch, carrageenan and konjak are commonly used in surimi.Proteinaceous additives, such as egg white (Yetim & Ockerman,1995), casein (Baker, Lanier, & Green, 2000; Uresti, Tellez-Luis,Ramrez, & Vazquez, 2004) and beef plasma-thrombin (Baker et al.,2000) have been shown to improve the mechanical properties ofsh and surimi gels. On the other hand, carbohydrates such asalginates, xanthan and high methoxyl pectins have a disruptiveeffect on surimi and sh gels (Barrera, Ramrez, Gonzalez-Cabriales,& Vazquez, 2002; Lee, Wu, & Okada, 1992; Park, 2000). FA gradesurimi gels have highermechanical properties than A grade gels andin this work, sh gelatin did not improve the mechanical propertiesof surimi grade A gels and showed a disruptive effect in surimi grade

six replicates with bars showing standard deviation. Different letters indicate signi-cant differences between treatments (P 0.05).FA when added at levels of 10 g/kg or higher. Differences for bothgels seem to be associated with a disruptive effect of sh gelatinwith the high grade gelling systems.

Table 1Effect of adding different levels of sh gelatin on the color attributes of surimi gels.

Fish gelatin in A grade surimi gels L* a*

Control 73.6 2.2a 3.2 0.1ab5 g/kg 76.3 2.5ab 3.3 0.2a7.5 g/kg 75.1 2.2ab 2.9 0.1c10 g/kg 74.0 2.8a 3.1 0.1bc15 g/kg 76.9 2.5b 3.0 0.1bc

Fish gelatin in FA grade surimi gelsControl 73.8 1.9ab 3.1 0.1ab5 g/kg 73.6 0.9ab 3.2 0.1a7.5 g/kg 75.3 1.3b 2.9 0.1bc10 g/kg 73.1 2.1a 2.9 0.1bc15 g/kg 74.9 1.3ab 2.8 0.2c

Mean values of six replicates and standard deviation.a,b,c, Indicate signicant differences between treatments (P 0.05).protein from surimi waste water (SWWSP) into grade FA surimigels was associated with an increase in the water holding capacityin surimi gels. The authors indicated that the absorption of thewater by the SWWSP favored a higher proteinprotein interac-tion, inducing a stronger gel. However, a disruptive effect wasobservedwhen SWWSPwas added at 3050 g/kg, decreasing boththe WHC and the mechanical properties of gels. Similar effect hasbeen reported for other additives used to improve mechanicalproperties (Uresti et al., 2003). In this work, sh gelatin modiedsignicantly the WHC of the surimi gels when added at levelshigher than 7.5 g/kg associated with a failure to improve themechanical properties of gels and a negative effect when 15 g/kg ofsh gelatin was added.

The detrimental effect on mechanical properties of FA gradesurimi gels might be associated with a disruptive effect of thegelatin during the formation of the three-dimensional structure bythe myobrillar protein interactions during the gelling phenom-enon. This three-dimensional structure is responsible for themechanical properties. Other feasible explanations for the failure ofthe sh gelatin to improve the mechanical properties seems to berelated with the failure of sh gelatin to improve WHC, promotinga higher number of myobrillar proteinwater interactions andinhibiting the myobrillar proteinprotein interactions.

The effect of sh gelatin on the color attributes of grade A surimigels is shown in Table 1. The amount of sh gelatin added changedthe color attributes of surimi gels. The L* value of the control gel was73.6 and increased signicantly to 76.9 in gels containing 15 g/kg ofsh gelatin. The a* parameter increased signicantly in samplescontaining 7.515 g/kg of sh gelatin indicating a change from slightgreenish in the control sample to slight redness. The b* parameterincreased signicantly in all samples with the amount of gelatinadded, indicating an increase in the yellowish. The chrome valueof gels increased slightly but signicantly in samples containing

b* Chrome* Hue* Whiteness

5.6 0.1a 6.4 0.2a 119 1.4c 72.9 1.2a5.8 0.3ab 6.7 0.2ab 119 2.1c 75.4 1.9ab6.2 0.3c 6.8 0.3b 115 1.1a 74.2 1.6ab5.9 0.3bc 6.7 0.3b 117 0.9b 73.2 1.3a6.2 0.2c 6.9 0.2b 116 0.9ab 75.9 1.2b

5.7 0.3ab 6.5 0.3a 118 0.9bc 72.9 0.6ab5.6 0.3a 6.5 0.2a 120 1.7c 72.8 0.9ab5.8 0.3ab 6.5 0.2a 117 2.0ab 74.5 1.1b5.7 0.2ab 6.5 0.3a 117 0.8ab 72.3 0.8a6.3 0.1c 6.8 0.1a 112 0.7a 74.0 1.2ab

7.515 g/kg of sh gelatin indicating a more intense chroma. Thechange in the hue angle value by adding 7.515 g/kg of sh gelatinindicates that an increase in yellowish color is obtained byincreasing the amount of sh gelatin.

The effect of sh gelatin on the color attributes of grade FAsurimi gels is also shown in Table 1. Adding sh gelatin did notshow a specic pattern in modifying the L* and C* attributes butaffected signicantly (P 0.05) the a* and b* parameters and the H*attribute. Increasing the amount of sh gelatin increased the valuesof the a* and b* parameters and decreased signicantly (P 0.05)

Cho, S. H., Jahncke, M. L., Chin, K. B., & Eun, J. B. (2006). The effect of processingconditions on the properties of gelatin from skate (Raja kenojei) skins. FoodHydrocolloids, 20, 810816.

Choi, S. S., & Regenstein, J. M. (2000). Physico-chemical and sensory characteristicsof sh gelatin. Journal of Food Science, 65, 194199.

Fernandez-Diaz, M. D., Montero, P., & Gomez-Guillen, M. C. (2001). Gel properties ofcollagens from skins of cod (Gadus morhua) and hake (Merluccius merluccius)and their modication by the coenhancers magnesium sulphate, glycerol andtransglutaminase. Food Chemistry, 74(2), 161167.

Gilsenan, P. M., & Ross-Murphy, S. B. (2000). Rheological characterisation of gelatinsfrom mammalian and marine sources. Food Hydrocolloids, 14(3), 191195.

Gimenez, B., Gomez-Guillen, M. C., & Montero, P. (2005). Storage of dried shskins on quality characteristics of extracted gelatin. Food Hydrocolloids, 19,

A. Hernandez-Briones et al. / Food Hydrocolloids 23 (2009) 24462449 2449the H* attribute indicating an increase in the yellowish color ofsurimi gels. One important attribute for surimi gels is whiteness. Inthis study, whiteness attribute as affected by increasing the shgelatin was detected instrumentally but it was not observed bysensory panelists.

4. Conclusions

Fish gelatin caused different effects when added into grade A orFA surimi. Adding sh gelatin into grade A surimi gave gels that didnot show changes in their mechanical properties but WHC wasimproved by adding 7.5 g/kg of sh gelatin. In high gelling grade FAsurimi, the mechanical properties decreased by increasing theamount of sh gelatin. Shear stress decreased signicantly when15 g/kg was added and shear strain decreased by adding 7.5 g/kg.The sh gelatin induced only small changes in color attributes thatcan be detected instrumentally, but not detected by most ofconsumers. Results obtained indicate that sh gelatin might beused as a functional additive to produce Alaska pollock surimi gelsbut it is not recommended for the FA grade surimi.

Acknowledgements

The authors are grateful to Fondo Mixto CONACYT- Gobiernode Tamaulipas for the nancial support of this work (projectTAMPS-2002-C01-14). A grant from CONACYT (Mexico) to authorA. Hernandez-Briones is gratefully acknowledged.

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Effects of adding fish gelatin on Alaska pollock surimi gelsIntroductionMaterial and methodsSolubilized fish pastes and gelsTorsion testExpressible water contentColorStatistical analysis

Results and discussionConclusionsAcknowledgementsReferences