PertanikaJ. Trap. Agric. Sci. 20(2/3): 107-111(1997) ISS : 0126-6128© Universiti Putra Malaysia Press

The Effect of Tamarind (Tamarindus indica) and Lime (Citrus medica) JuiceWashing on the Sensory Attributes and the Rancidity Development

in Breaded Tilapia - A Preliminary Study

JAMILAH BARAR AND SITI AINI HAMZAHDepartment of Food Technology

Faculty of Food Science and BiotechnologyUniversiti Putra Malaysia

43400 UPM Serdang, Selangor, Malaysia

Keywords: muddy flavour or odour, breaded tilapia fillet, storage

ABSTRAK

Keberkesanan bagi menyah bau dan citarasa lumpur di dalam ikan tilapia hitam (Oreochromis mossambicus)dengan perlakuan pembasuhan (15. % b/isipadu jus asam jawa, 1.5% jus limau nipis dan campuran: O. 75%jus limau dan 0.75 % jus asam jawa) telah dikaji. Kesan pembasuhan terhadap ketengitan di dalam ikantilipia bersalut yang disimpan di suhu -20°C juga dibuat. Pembasuhan dengan larutan asid berjayamengurangkan bau dan citarasa lumpur mengikut ahli panel. Sampel yang dibasuh dengan asam jawamenunjukkan perbezaaan daripada sampel lain dan mendapat lebih tinggi yang ketara bagi citarasa, baudan wama. Kesemua sampel yang diberi perlakuan menunjukkan perbezaan kekenyalan yang ketara dari sampelkawalan. Walaubagaimanapun, proses ketengitan di dalam sampel berdasarkan nilai peratus asid thiobarbituric(TBARS) yang di simpan tidak dapat direncatkan.

ABSTRACT

The feasibility of removing the muddy flavour and odour of black tilapia (Oreochromis mossambicus) withnatural acid extracts from tamarind and lime l7y washing treatment (1.5 % w/v tamarind juice, 1.5 % v/v limejuice and a mixture of lime juice 0.75 % and tamarind juice 0.75 % was investigated. The effect of the washingtreatment on rancidity development in breaded tilapia kept at -20°C was also monitored. Acid washing improvedthe acceptability for flavour and odour as detected l7y sensory panellists. Samples treated with tamarind juice weredifferent from other samples and were scored significantly higher for flavour, odour and colour than othertreatments. All treated samples had a significantly tougher texture than the control. However, the ranciditydevelopment as indicated l7y the percentage of thiobarbituric acid reactive substances (TBARS) values in storedsamples was not retarded.

INTRODUCTION

Fish is a major source of protein, especially inthe Asian region. However, fish consumption ismainly limited to marine species as freshwaterfish is still less acceptable. One deterrent to theacceptability of freshwater fish is its characteris­tic muddy or earthy flavour and aroma whichare mainly due to the presence of geosmin and2-methylisoborneol (Yurkowski and Tabachek1974, 1980; Kuusi and Suihko 1983). Geosmin isa volatile compound (Tyler et al. 1978), whichcan be transformed into an odourless compound

by acids (Marshall and Hochstetler 1968). Themarketability of fish can also be increased if it isformulated as a convenience food such as abreaded product. Attempts to remove the muddyflavour from live fish in holding tanks have beenreported in pond-cultured channel catfish (Lovell1983) and rainbow trout (Yurkowski andTabachek 1974). Van Allen and Pessoney (1982)demonstrated that the off-flavour in culturedcatfish can be reduced by the addition of potas­sium ricinoleate to the pond water to inhibit thegrowth of the blue-green algae believed to be

JAMILAH BAKAR AND SITI AINI HAMZAH

the source of the compound that causes themuddy flavour. In either case, it takes time to beeffective, e.g. 14 days for rainbow trout (Yurkowskiand Tabachek 1974). Hence it is time consumingcompared with a method that removes the smellduring the processing itself. However, Rohaniand Yunus (1994) reported that soaking for 30min in 5% salt solution leached out some of themuddy attribute as reflected by the sensory scoresof the deboned red tilapia meat.

Traditional practices, such as washing wholefish with lime juice, tamarind juice and flour,are said to remove the muddy flavour and thusincrease the acceptability of the fish. The effec­tiveness of this procedure has not been scientifi­cally tested, but may have some basic since tama­rind and lime juice are rich tartaric andcitric acids, respectively. We here report theresults of a preliminary study on the effect ofwashing tilapia fillets with tamarind juice, limejuice or a mixture to removal its muddy flavour,to evaluate the sensory attributes of the filletsand to monitor rancidity development in thebreaded product. The rancidity factor is takeninto account since the breaded tilapia is a deep-

fried product and the development of ranciditymay be induced by the presence of the addi­tional oil in the fish and breading.

MATERIALS AND METHODS

Live black tilapia (Oreochromis mossambicus) weigh­ing approximately 500-600 g each were pro­cured from a nearby farm and brought alive tothe laboratory. The procedure for their prepara­tion is shown in Fig. 1.

Preparation of Washing Solutions

The lime juice solution was prepared by squeez­ing ripe fresh limes (Citrus medica) and dilutingthe juice to the percentage (v/v) with distilledwater. The tamarind (Tamanndus indica) paste(the form used locally) was purchased from thenearby retail shop. The percentage of tamarindjuice for washing was prepared on wIv basis(excluding the seeds). The pH of the juiceextracts was not determined. A higher percent­age of the juice is not desirable as a preliminarystudy showed it caused excessive gaping andtoughening of the muscle and also imparted aslightly acidified flavour to the cooked samples.

Whole live fish

~Kill by sudden blow

~Filleting (100 g per piece)

~Washing in shaking water bath

(2 min; 1 litre washing solution to 3 fillets; 140 rpm)

~Drip dry

. J bDIp matter

~Breading

~Flash fry (1 min at 180°C)

~Air cooled

~Packaged in polystyrene trays and overwrapped

~Stored at -20°C

~Final frying (for sensory evaluation only)

Fig. 1. Flowchart for the sample preparation of lrreaded tilapia

108 PERTANIKAJ. TROP. ACRIe. SCI. VOL. 20 NO. 2/3,1997

THE EFFECT OF WASHING ON BREADED TILAPIA FILLETS

Titrable Acidity

The titrable acidity of both juice was deter­mined by the method used by Ranganna (1986).

TABLE 1pH of tilapia fillets

Item* pH**

6.67a

6.68a

6.68a

6.57b

6.73c

Control - washing with water; TAJ - washing with1.5% tamarind juice; LIJ - washing with 1.5% limejuice; MIX - washing with 0.75% lime juice +0.75% tamarind juice

** Based on the average scores of flacour, odour,colour and textureMeans followed by a 'different superscript aresignificantly different at 5% level.

*

TABLE 2Sensory scores of cooked breaded tilapia

Treat- Flavour Odour Colour Texture Accept-ment* ability**

Control 5.7b 6.0ab 5.9b 5.3a 5.7b

TAJ 6.1" 6.3a 6.5a 5.9b 6.2a

LIJ 5.8ab 5.8b 6.8a 5.7b 6.0ab

MIX 5.5b 5.9b 6.0b 5.7b 5.7b

slight toughening of the fillets was noted. TA]received the highest acceptability score. Hence,the effectiveness of the treatment can be rankedas TA] > LIJ > control, mix.

The % TBARS values (Fig. 2) in breadedtilapia increased linearly with storage time. Wash­ing with either lime juice or tamarind juice didnot retard the rancidity development in frozensamples. Ramanathan and Das (1992) indicatedthat samples with % TBARS > 100% are indica­tive of the presence of rapid lipid oxidation.This value was achieved by all samples afterabout eight weeks of frozen storage. However,no samples were scored unfavourably or rejectedfor off-flavour development (Fig.3). Similarly,no samples was rejected for off-odour develop­ment (Fig 4.) The rapid decline in both flavourand odour scores of the samples indicates theymay be rejected after a few more weeks' storageat -20°C.

* Control - washing with water; TAJ - washing with1.5% tamarind juice; LIJ - washing with 1.5% limejuice; MIX - washing with 0.75% lime juice +0.75% tamarind juice

** Means followed by a different superscript are sig­nificantly different at 5% level.

fish muscle (unwashed)ControlTAJLIJMIX

RESULTS AND DISCUSSION

The titrable acidity of both tamarind and limejuice was 2.0 ± 0.1 %. The fillets washed with LIJhad a pH significantly lower than those thatwere unwashed (control), washed with TA] andwashed with mix (Table 1). This lower pH of theLI] washed samples may be the reason why thesesamples were slightly springy in texture as com­pared to the others (Kramer 1971).

Table 2 shows the sensory scores of cookedbreaded tilapia. The TA] samples scored signifi­cantly higher (P<0.05) for flavour and odourcompared to other treatments. However, filletswashed in TA], LIJ were scored significantlyhigher for colour. The samples looked morebleached than the control and those washedwith the MIX. The texture of the control scoredsignificantly lower than all treated samples. A

Thiobarbituric Acid Reactive Substances (% TBARS)The percentage of thiobarbituric acid reactivesubstances (% TBARS) values (Ramanathan andDas 1992) was measured after samples had beenstored at -20°C. Storage was carried out mainlyto observe the possible effect of the washingtreatment on the rancidity development of theproduct.

Sensory Evaluation

The sensory evaluation was carried out by 12untrained panellists according to the scale ofKosmark (1986) where 7 = like very much; 4 =neither like nor dislike and 1 = dislike verymuch. It is presumed that samples that wereliked did not have a muddy odour or flavour,which if present would have been scored as lessthan 4, i.e. are disliked. The attributes scoredwere flavour, odour, colour, texture and accept­ability. It was done fully cooked samples, i.e.after frozen storage they were further deep-friedto golden brown prior to evaluation.

pH Determination

Determination of pH of unbreaded fillets wascarried out after the drip-drying process. Tengrams of the samples were homogenized in 100ml of distilled water and the pH was determinedby a pH probe. Readings were done in triplicates.

PERTANIKAJ. TRap. AGRIC. SCI. VOL. 20 0.2/3,1997 109

JAMILAH BAKAR AND SITI AI I HAMZAH

200 ,..---------------,

150

(J)a:;ii 100I-

50

i /:

0-'" >i/"- ....•.

C

P_..

TAJ~

L1J

MIX--[]

6.5,..--------------.,c-'TAJ

lIJ

MIX

-0

'.o ............---'-----'----'----L...---L...-....J..J

128 10642o4.5 U-_-'-_.l....----'_---'-_--I..._--LJ

Storage time at -20°C (week)

Fig. 4. Odour scores of breaded tilapia kept at-20 DC

12o 2 4 6 8 10

Storage time at -20°C (week)

Fig. 2. % TBARS values ofbreaded tilapia storedat -20 DC

REFERENCES

KOSMARK, JJ. 1986. Standardizing sensory evalua­tion methods for marketing fish product. InProceedings of the International Symposium onSeafood Quality Determination, ed. D. Kramerand J. Liston, p. 99-108. Amsterdam: Elsevier.

KRAMER, D.E. 1971. Hypoxanthin and nucleotidelevels in Pacific halibut stored in refrigeratedsea water, in ice, and plate frozen. In TechnicalAspects of Fish Quality Control, p. 28-38. FAOFisheries Report o. 115.

KUUSI, T. and M. SUIHKO. 1983. Occurrence ofvarious off-flavours in fish in Finland from1969-1981. Water Science and Technology 15: 47­58.

L1J

MIX

-0--

5

0-_

6 0

6.5 ,.---------------, -c...•...

lAJ

·0··

~---"". o,.~__

5.5 13 -__~"'. . "". ~

LCJ·· •• ,•••.... -.'0~~0-_ ..•. ....

-"'0._ "'- "~.'---0_._ •. \ ....•

D· _,

\'\'b4.5

CIlQ)

o()CIl

:Jo>CIlLL

4L-----I---'----'----'---...J......Jo 2 4 6 8 10 12

Storage time (week) at -20°C

Fig. 3, Flavour scores of breaded tilapia kept at-20 DC

CONCLUSION

Washing with TAj, LIj or the MIX improvedacceptability score for the odour and flavour oftilapia fillets. Tamarind juice washing scoredhighest for overall acceptability. one of thewashing treatments retarded rancidity develop­ment in breaded fillets during storage as meas­ured by the % TBARS value.

LOVELL, R.T. 1983. Off-flavours in pond-culturedchannel catfish. Water Science and Technology15: 67-73.

MARsHALL, J.A. and A.R HOCHSTETLER. 1968. Thesynthesis of (+)-geosmin and the other 1, 10­dimenthyl-9-decalol isomers. Journal of OrganicChemistry 33(96): 2593-2595.

RAMANATHAN, Land .P. DAS. 1992. Studies on thecontrol of lipid oxidation in ground fish bysome polyphenolic natural products. Journal ofAgricultural and Food Chemistry 40 (1): 17-21.

RANCANNA, S. 1986. Proximate constituents. In Hand­book of Analysis and Quality Control for Fruit and

no PERTANIKAJ. TROP. ACRIe. SCI. VOL. 20 NO. 2/3,1997

THE EFFECT OF WASHI GO BREADED TIlAPIA FILLETS

Vegetable Products, 2nd edn. p. 1-15. ew Delhi:Tata McGraw-Hill.

ROHANI, A.c. and M. Yu IUS. 1994. Processing ofsurimi from freshwater fish-tilapia. In 5thAseanFood Conference, 26-29 July, Kuala Lumpur,Malaysia. p. 286-288.

TYLER, L.D., T.E. ACREE, RR NELSON and R.M.BUDs. 1978. Determination of geosmin in beetjuice by gas chromatography. Journal ofAgricul­ture and Food Chemistry 26(3): 774-775.

VAN ALLEN, RT. and G. PESSONEY. 1982. Algal re­search affects catfish off-flavour. Aquaculture 8:18-23.

YURKOWSKI, M.M. and J.L. TABACHEK. 1974. Identifi­cation, analysis and removal of geosmin frommuddy flavoured trout. Journal of Fisheries Re­search Board Canada. 31: 1951-1858.

YURKOWSKI, M. and J.L.TABACHEK. 1980. Geosminand 2-methylisoborneol implicated as a causeof muddy odour and flavour in commercialfish from Cedar Lake, Manitoba. CanadianJournal ofFisheries and Aquatic Science 37: 1449­1450.

(Received 3 February 1996)(Accepted 1 October 1997)

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