Protein and Micronutrient Composition of Low-Value Fish Products Commonly Marketed in the Lake Victoria Region

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1 World Journal of Agricultural Scincs 7 (5): , 2011 ISSN IDOSI Publications, 2011 Protin and Micronutrint Composition of Low-Valu Fish Products Commonly Marktd in th Lak Victoria Rgion M.K. Kabahnda, R. Amga, E. Okalany, S.M.C. Huskn and S. Hck 1 Dpartmnt of Food Tchnology and Nutrition, Collg of Agricultural and Environmntal Scincs, Makrr Univrsity, P O Box 7062, Kampala, Uganda 2 Th World Fish Cntr, Addis Ababa Rd, P O Box 51289, Lusaka, Zambia Abstract: Incras in dmand of fish from Lak Victoria rgion has cratd gaps in local fish supplis and this raiss concrn sinc thr ar rports of limitd animal-sourc food consumption plus protin and micronutrints dficincis in this rgion. To fill th gap, lss-prfrrd plagic fish spcis such as Mukn (Rastrnobola argnta) and by-products from fillting Nil prch (Lats niloticus), which wr commonly usd for animal fds, ar incrasingly bing minimally procssd and marktd for dirct human consumption. Ths fish products constitut what has bn trmd as low-valu fish products. This study was carrid out to assss th nutrint contnt of low-valu fish products (LVFPs) so as to documnt thir potntial contribution to protin and micronutrint intak of individuals who dpnd on ths products as thir major animal sourc food.commonly marktd sampls of frsh, smokd, dp frid and sun-drid Nil prch by-products and mukn wr collctd from factoris, by-product procssing sits and markts to dtrmin thir nutrint contnts. Th rsults show that most LVFPs had protin lvls comparabl to Nil prch fillt but mukn products had th highst crud protin (47.9% to 58.8%), followd by frsh prch ggs products (32.1% to 38.7%). On dry wight basis, th concntration of iron was highst in mukn products ( mg/100g) and lowst in prch fillt (1.06 mg/100g); zinc was highst in mukn products ( mg/100g) and frsh prch ggs (4.07 mg/100g); whil calcium was highst in prch skin ( mg/100g) and mukn products ( mg/100g). Prch fillt was among th products with lowst amounts of iron, zinc and calcium.ths findings suggst that LVFPs can improv protin and micronutrint intak of individuals with limitd accss to animal-sourc foods. Thr is nd to ducat communitis to improv procssing, handling and accptability of LVFPs products for dirct human consumption. Ky words: Low-valu fish products Animal-sourc food Calcium Iron zinc INTRODUCTION mukn (a plagic fish spcis), by-products from fillting Nil prch and juvnil fish in ordr to dtrmin whthr Analysis of trnds in global animal sourc food ths products provid a good altrnativ sourc for consumption indicat dcrasing fish consumption in protin and micronutrints among populations that dvloping countris; yt ths countris alrady had cannot accss high valu animal-sourc food products low pr capita consumption of animal sourc foods such as matur fish and fillt. [1]. This situation raiss concrn bcaus lss dvlopd Som of th stratgis proposd to improv fish countris continu to rcord high prvalnc of supply for human consumption includ incrasd us of undrnutrition and this is partly attributd to limitd undrutilizd spcis and rduction in fish wastag in ditary intak of nutrint dns foods such as form of unintndd by-catchs and post-harvst losss animal-sourc food products. This study invstigatd th [2]. At th momnt, th only undrutilizd fish spcis in nutrint contnt of lss valud fish products such as th Lak Victoria rgion ar small plagic fish spcis Corrsponding Author: Kabahnda, M.K., Dpartmnt of Food Tchnology and Nutrition, Collg of Agricultural and Environmntal Scincs, Makrr Univrsity, P O Box 7062, Kampala, Uganda. 521

2 such as Rastrinobola argnta (which is commonly calld mukn in Uganda, dagaa in Tanzania and omna in Knya) and haplochromins (Nkjj). Unintndd by-catchs in Nil prch and tilapia fishris ar oftn comprisd of indignous fish spcis such as Protoptrus (lung fish or Mmamba) and catfishs (spcifically Bagrus docmac, Synodontis victoria, Clarias garipinus and Schilb intrmdius) but ths indignous fishs ar highly valud and fully utilizd for local consumption [3]. Anothr catgory of by-catchs from th Lak Victoria ar mollusca (spcially P. Athiopicus) and caridina nilotica (which ar commonly calld prawns or shrimp); howvr Mollusca ar not harvstd for dirct human consumption bcaus thy ar considrd disas vctors whil th harvst of prawns for dirct human consumption is bannd in th Lak Victoria rgion sinc prawns constitut a major pry for Nil Prch. A rviw of low-valu fish products marktd in th Lak Victoria rgion [3] rvald that th bulk of LVFPs tradd and consumd by populations in th rgion wr comprisd of fish frams (backbon and fins with or without hads), hads, ro (ggs) and skin gnratd from fillting Nil prch [3]. Ths products in combination with mukn and by-catchs of juvnil fish ar th fish products that ar rfrrd to as low-valu fish products (LVFPs) in this papr. Promoting LVFPs has high potntial to improv food and nutrition scurity in th Lak Victoria rgion bcaus this rgion is xprincing incrasd dmand for its fish at intrnational and rgional markts; howvr fish stocks and catchs hav bn dclining ovr th yars. As a rsult, artisanal fishrfolk in Lak Victoria rgion hav divrtd to harvsting of immatur fish (mostly juvnils of tilapins, Nil prch and catfishs) and plagic fish (mostly mukn) whil artisanal procssors hav divrtd to procssing by-products from fish fillting factoris as a stratgis to improv gaps in local fish supply [3]. Th dilmma in using LVFPs for dirct human consumption is that ths products ar oftn handld as trash and crudly procssd for local and informal rgional markts [4-6]. Th poor handling and minimal procssing oftn inducs dgradation and is xpctd to rsult in products with limitd nutritiv valu. Hnc, th purpos of this study was to dtrmin th nutritiv valu of LVFPs commonly marktd in th Lak Victoria rgion in ordr to assss thir potntial contribution to improving ditary intak of protin and micronutrints among populations who dpnd on ths LVFPs as thir major animal-sourc food. MATERIALS AND METHODS Sampl Collction: Th numbr of sampls collctd for ach product dpndd on th numbr of procssors or vndors daling in th product. Efforts wr mad to collct ach sampl from at last thr procssors or vndors. Th sampls collctd wr catgorizd by procssing mthod which includd frsh (unprocssd), dp frid, smokd and sundrid (includs saltd) products. Although mukn is a sundrid fish product, in this study mukn (which is commonly calld omna in Knya and dagaa in Tanzania) is considrd as a sparat catgory of LVFPs bcaus th dynamics of its harvst and trad diffrs from othr sundrid LVFPs that wr studid. Frsh LVFPS: Frsh skins, frams and hads of Nil prch (L. niloticus) wr acquird from th sam fillting factory. Nil prch ggs (ro) wr acquird from artisanal LVFP procssors in Katw food markt whil Mukn was acquird from fishrfolk at Kiyindi landing sit. Dp Frid Products: Som of th frsh skins, frams and hads dscribd abov wr takn to artisanal procssors who dp frid ths products to gnrat th dp frid sampls usd in this study. Artisanal procssors dp frid ths LVFPs using th oil thy wr using to dp fry othr products for thir usual businss. Oil usd for dp frying was a mixtur of vgtabl oil and oil gnratd from Nil prch by-products. Most procssors usd vgtabl oil as bas oil to start off th frying procss but th volum of dp frying oil was maintaind by adding fat pads gnratd from prch frams. Non of th ight procssors intrviwd could tll for how long thy had usd th oil. Othr food products that wr dp frid in th sam oil includd chips of frsh swt potatos and frsh cassava. Saltd and Sun-Drid Products: Drid prch hads, frams and chips (also calld trimmings or off-cuts) wr bought from artisanal procssors at th Busga by-products procssing sit. In gnral, tradrs wr not willing to sll sundrid products. Hnc, sampls of about 2-3 kg ach of hads and frams (without had) wr obtaind from four artisanal procssors. Th sampls of chips (about 1 kg in total) wr collctd from two procssors. 522

3 Mukn: Frshly drid sampls of about grams wr bought from artisanal procssors that wr drying mukn at landing sits in Kiyindi and Buvuma islands. Othr sampls wr collctd from tradrs that wr airing mukn at Kiyindi landing sit. Oldr sampls wr collctd from rtail fish mongrs in food markts around Kampala. Saltd, drid mukn sampls wr collctd from a commrcial procssor at Kiyindi landing sit. Smokd Products: Frshly smokd sampls of fish skins wr purchasd from th by-product procssing sit in Busga. Frshly smokd sampls of juvnil prch wr bought from artisanal procssors in Buvuma islands. Oldr sampls of juvnil Nil prch wr purchasd from rtail fish mongrs in food markts around Kampala; howvr, sinc vndors gt products through middlmn, it was not possibl to dtrmin how long ths sampls had bn on th markt. With th xcption of saltd mukn and prch fillt, all LVFPs assssd wr collctd from artisanal procssors to allow for gnralizing of findings to usual procssing conditions. All sampls wr put on ic bags in thrmo cooling boxs immdiatly aftr thy wr collctd in ordr to rduc spoilag during transportation. Sampl Prparation: Sampl prparation involvd cooking (staming or boiling) fish sampls and xtracting dibl tissu from th cookd products. Edibl tissu was xtractd from th bons on day of collction manually using a kitchn knif. Extractd dibl tissu was thn ground using a havy duty blndr to obtain a homognat which was stord in non-transparnt plastic containrs in a frzr. Mukn sampls wr stord as purchasd and ground right bfor nutrint dtrmination. All sampls wr analyzd within 1 wk of collction. Nutrint Dtrmination: All xprimnts on dtrmination of moistur contnt, crud protin, fat and minrals (calcium, iron and zinc) wr prformd in triplicat. Dtrmination of Moistur Contnt: Moistur contnt was dtrmind using th dry ovn mthod AOAC [7]. For ach low-valu fish product, thr sampls of 3-4 g wr placd in dry moistur dishs of known wight and wighd using a digital food wighing scal. Dishs with sampl wr thn placd in ovn and drid for 4 hours at 125 C aftr which drid sampls wr wighd again to dtrmin moistur loss. Dtrmination of Crud Protin: Crud protin was dtrmind by th Kjldahl mthods (AOAC ) using sulphuric acid for sampl digstion. Total nitrogn was quantifid by titrating th distillat against 0.05M hydrochloric acid. Mthyln blu and mthyl rd mixtur was usd as indicator. Crud protin was dtrmind by multiplying th nitrogn valu by th convrsion factor of Dtrmination of Crud Fat: Crud fat was dtrmind using AOAC mthods [7]. Th sampl was xtractd with ptrolum thr (BP C) in Soxhlt typ continuous xtraction apparatus. Dtrmination of Minral Contnt: Calcium, iron, zinc and sodium contnt wr dtrmind quantitativly using atomic absorption spctrophotomtric mthods [7]. Statistical Analyss: Rsults wr subjctd to analysis of varianc (ANOVA) using Stata statistical softwar (Stata Corporation, Txas, USA). Multipl comparisons of mans wr don using th Bonfrroni mthod and p-valus < 0.05 wr considrd statistically significant. RESULTS Tabl 1 summarizs th major findings from this study. In gnral, all low-valu fish products (LVFPs) assssd had high lvls of micronutrints invstigatd. Moistur Contnt: As shown in Tabl 1, moistur contnt of LVFPs assssd varid basd on procssing mthod and th typ of product. Moistur contnt of frsh products rangd from 62.4% to 81.1%. Moistur contnt of all drid products xcdd th 12% cut-off. Products with th last moistur contnt wr frshly sundrid mukn (12.4%), dp frid mukn (14.2%) and smokd juvnil prch on th markt (14.2%). Smokd juvnil prch on th markt had about half th moistur contnt of frshly smokd juvnil prch. Crud Protin: Drid mukn (R. argnta) had th highst protin contnt ( %) whil smokd prch juvnils sampls collctd from th markts and frsh gills had th last protin (10.4% and 16.2%, rspctivly). All othr prch by-products did not significantly diffr from prch fillt. 523

4 Tabl 1: Nutrint Composition of Commonly Consumd Low-valu Fish Products Nutrints pr 100 g dry mattr of dibl portions Fish product Procssing mthod % Moistur contnt % Crud fat % Crud protin Iron (mg) Zinc (mg) Calcium (mg) Sodium (g) Prch had Frsh, boild (n=6) f 74.7 ± 0.7 a 2.49 ± 0.9 c 29.38± ± ± ± ± 0.04 b a a a Dp frid, boild (n=8) 62.2± ± ± ± ± ± ± 0.12 b c a a a a Saltd sundrid, boild (n = 6) d 48.6± ± ± ± ± ± ± 0.08 a c a a a c Prch gills Boild (n=2) 42.3± ± ± ± ± ± ±0.07 c a a a a a a Prch fram Frsh, boild (n=6) 72.5 ± ± ± ± ± ± 0.01 a b a a a Dp frid fram (n=8) d 52.2± ± ± ± ± ± 0.08 c c a a a Prch skin Frsh, boild (n = 3) 69.4 ± ± ± ± ± ± ± 0.03 a c a a b a Saltd sundrid, boild (n=4) 67.1± ± ± ± ± ± ±0.02 a b a a b b Dp frid, boild (n = 3) 59.9± ± ± ± ± ± ± 0.08 d c a a b a Smokd, boild (n = 3) 48.0± ± ± d c b Prch chips Saltd sundrid, stamd (n=1) 43.1± ± ± ± ± ± c b b a a a Prch oil Crud (n=1) ±0.68 Trac Trac - a Prch ggs Frsh, dp frid (n=2) ± ± ± ±0.03 Trac - d c b b Frsh, stamd (n=2) ± ± ± ±0.16 Trac - a d b a Juvnil prch Smokd frsh from kiln (n=3) 31.2± ± ± b a c Smokd from markt (n=4) 14.2± ± ± a a a R. Argnta Frsh, boild (n = 2) g 81.1± ± ± ± ± ± a b a b b Markt, drid boild (n=7) 66.2± ± ± ± ± ± ±0.020 a c c c b a Landing sit, drid saltd (n=1) 17.1± ± ± ± ±0.37 a c c c Landing sit, drid unsaltd (n=8) 12.4± ± ± ± ± ± a c c c b Prch fillt Frsh (n=1) 84.2± ± ± ± ± ± g a b a a a n rfrs to numbr of procssors or vndors from whom sampls wr collctd. All sampls wr analyzd in triplicat. Mans with th sam lttr in th sam column ar not significantly diffrnt (P=0.05). Data ar rprsntd as mans ± standard dviation Fat Contnt: Of th products assssd in this Calcium Contnt: Mukn and Nil prch skin wr study, crud fat was lowst in smokd juvnil prch dtrmind to hav th highst amounts of calcium. As (0.7% to 2.0%) and highst in prch chips (6.9%). Dp shown in Tabl 1, th calcium contnt of prch skin frying incrasd fat contnt by 6-fold in prch skin (without scals) rangd from 1827 to 1986 mg/100 g dry (3.9% to 23.5%) and by 10-fold in mats scrappd from mattr whil mukn was composd of 1556 to 1866 prch frams (1.7% to 17.4%). Sundrid Mukn products mg/100 g dry mattr. Amounts of calcium in prch fillt had an avrag of % fat pr 100 g of dry mattr, wr not significantly diffrnt from chips, gills and mats which was highr than all prch products that wr not xtractd from prch hads. Prch ggs had ngligibl dp frid. amounts of calcium. Iron Contnt: Iron contnt varid significantly across DISCUSSION th diffrnt products. Sundrid mukn products had th highst amounts of iron (8.2 to 10.7 mg pr 100 g of In gnral, all low valu fish products assssd had dry mattr). Mats from prch had wr mostly high lvls of iron and zinc. In addition Nil prch skin comprisd of rd mats, hnc also had high lvls of iron and mukn (Rastrinobola argnta) products had (6.1mg/100 g). Prch ggs, which had an avrag of 5.4 mg xcptionally high lvls of calcium. Th micronutrint to 5.7 mg pr100 g of dry mattr, wr also among th profils of LVFPs invstigatd in this study indicat that products with significantly highr iron contnt. Prch fillt low valu fish products can contribut to nutrition was comprisd of whit mat only and its iron contnt scurity of low incom populations that dpnd on ths was 1.06 ±0.03 mg pr 100 g dry mattr, which puts fillt products as thir major animal sourc food. Although this among th products with th last amounts of iron. study only focusd on iron, calcium and zinc, th high lvls of ths nutrints suggst that low-valu fish Zinc Contnt: Zinc was highst in sundrid products ar a good sourc of othr micronutrints that mukn products ( mg/100 g) and in prch ggs ar xpctd to b high in fish. ( mg/100 g). All othr products had zinc contnts With th xcption of mukn, all th low-valu fish highr than fillt but th diffrncs wr not products assssd had slightly lowr protin contnt than statistically significant. rportd in othr studis [6] that hav lookd at high 524

5 valu fish. This can b attributd to poor handling consqunt dgradation, juvnil prch and mukn from practics. For xampl, onc th by-products wr out of artisanal procssors had significantly highr amounts of fillting factoris, thr was no cold chain for LVFPs and protin than juvnil prch and mukn from th markts, in most cass ths products wr handld as trash. Poor rspctivly. handling practics ar likly to hav inducd spoilag in most LVFPs invstigatd and incrasd protolytic CONCLUSIONS procsss and growth of microorganisms which rsultd in low protin contnt. Furthr studis ar ndd to Ovrall, low-valu fish products marktd in Lak invstigat protin losss along th LVFPs procssing Victoria rgion ar nutrint dns and can contribut to chain. In th mantim, it is important to hav quality improving th gap in local fish supply. Thr is nd for controls at procssing and markt lvl to nsur that policy to rgulat divrsion of ths products into animal consumrs accss wholsom products with accptabl fds and to rgulat xportation of ths products in nutritiv and organolptic proprtis. ordr to improv accss of LVFPs among populations at Dspit th blif that prch is a fatty fish, risk for malnutrition. Local utilization of LVFPs can b all prch products that wr not dp frid mt th 5% nhancd if th procssing of ths products is improvd cut off critrion that I s usd to classify fish as low fat to avail consumrs with visually appaling products with [8]. Th practic of dp frying fish products incrass accptabl organolptic proprtis. Givn th fact that total fat and maks LVFPs lss dsirabl for halth LVFPs ar not kpt undr cold storag, thr is nd to conscious consumrs. Th amount of fat in mukn is improv smoking and sun-drying procsss in ordr to high; howvr, th fatty acid profil rvals that nsur longr shlf lif of ths fish products. Adquat mukn fat is mostly comprisd of poly-unsaturatd fatty procssing and appropriat packaging of LVFPs can acids (rsults rportd lswhr). Iron, zinc and calcium improv th nutritiv quality and utilization of LVFPs and wr also highst in mukn bcaus this fish is atn thrby improv accss to animal-sourc foods in th whol. Lak Victoria rgion. Lik othr small fish spcis [4, 9, 10], mukn was dtrmind to b nutrint dnsr than all othr ACKNOWLEDGEMENTS LVFPs invstigatd. In this study, sundrid mukn had th highst amounts of micronutrints than fillt and Th authors ar gratful to SIDA for funding this by-products gnratd from fillting Nil prch. Whn projct. Th guidanc from staff of th Dpartmnt of compard to prch fillt, mukn had 8- to 10-fold iron Fishris Rsourcs in Uganda and mmbrs of Bach contnt, mor than 14-fold zinc contnt and about 14-fold Managmnt Units and th support of participants at calcium contnt. This is an important finding givn th landing sits and markts ar highly apprciatd. fact that mukn stocks and catchs hav incrasd in Th authors also acknowldg th tchnical support Lak Victoria as a rsult of th dwindling stocks of Nil of Mr. Sntongo from DFTN, Makrr Univrsity and prch which is a major prdator of mukn. Howvr, th Prof Robrt A Skilton of BECA Hub/ILRI. protin contnt of mukn was lowr than dtrmind from othr studis. This could hav rsultd from REFERENCES inadquat drying which rsults in som mukn rotting as som sampls wr obsrvd to hav visibl signs of 1. Spdy A.W., Global Production and rot and discoloration. Consumption of Animal Sourc Foods. J. Nutrition, Smoking and sun-drying ar major mthods usd to 133: 4048S-4053S. prsrv fish in Lak Victoria rgion, howvr rsults from 2. Svrdrup-Jnsn, S., Fish Supply and Dmand this study indicat that many of th LVFPs ar not drid Projctions. NAGA Supplmnt, July-Dcmbr, nough to arrst nzym activity, lipid oxidation and pp: hydrolytic ractions which ar oftn associatd with high 3. Kabahnda, M.K. and S.M.C. Huskn, watr activity [11]. Smokd products wr partially drid A Rviw of Low-Valu Fish Products in th Lak bcaus of th nd to sav on ful wood whil sundrid Victoria Rgion. Th World Fish Cntr Rgional LVFPs wr partially drid to avoid rductions in wight Programm - Fishris and HIV/AIDS in Africa: bcaus ths products ar sold to tradrs on wight Invsting in Sustainabl Solutions. Lusaka, Zambia. basis. As a rsult of inadquat drying and th Projct Rport,

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