Merki: Shelf life

Skýrslur

Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

Útgefið:

01/12/2009

Höfundar:

Emilía Martinsdóttir, Cyprian Ogombe Odoli, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Hannes Magnússon, Sigurjón Arason, Ragnar Jóhannsson

Styrkt af:

Tækniþróunarsjóður

Tengiliður

Kolbrún Sveinsdóttir

Verkefnastjóri

kolbrun.sveinsdottir@matis.is

Optimal storage conditions for fresh farmed tilapia (Oreochromis niloticus) fillets

Tilgangur tilraunanna var að finna bestu geymsluaðstæður fyrir fersk tilapíuflök með því að ákveða geymsluþol með skynmati, örverutalningum og eðlis- og efnafræðilegum mælingum. Nílartilapía (Oreochromis niloticus) alin í endurnýtanlegu vatnshringrásarkerfi var flökuð og pökkuð í 100% lofti og loftskiptum pakkningum 50% CO2: 50% N2 MA fyrir geymslu við 1˚C og -1˚C. Lýst er þróun QIM-einkunnaskala og skynmatseiginleikum ferskra og soðinna tilapíuflaka og notkun skalans í geymsluþolstilraun. Línulegt samband fannst milli gæðastuðuls og geymslutíma (r > 0.93) fyrir alla geymsluhópa. Niðurstöður skynmats og örverutalninga sýndu að flök sem pakkað var í lofti höfðu geymsluþol 13-15 daga við 1˚C og 20 daga við -1˚C. Við lok geymsluþols í loftpakkningum var heildarörverufjöldi og fjöldi pseudomonads örvera log 7 CFU/g í holdi. Í flökum í loftskiptum pakkningum var lagfasi lengri og heildarfjöldi örvera var undir log 4 CFU/g eftir 27 daga geymslu bæði við 1˚C og -1˚C. Samt sem áður höfðu loftskiptar aðstæður slæm áhrif á lit flaka skömmu eftir pökkun en litur flaka hefur veruleg áhrif á val kaupenda. Efnafræðilegar mælingar eins og TVB-N og TMA voru ekki góður mælikvarði á skemmd tilapiuflaka. Bestu geymsluaðstæður fyrir tilapíuflök er pökkun í lofti og geymsla við stöðugt lágt hitastig -1°C. Skýrsla þessi er byggð á helstu niðurstöðum úr meistaraprófsverkefni Cyprian Ogombe Odoli.

The main aim was to establish optimal storage conditions for fresh tilapia fillets by determining its shelf life by sensory and microbiological evaluation, as well as monitoring its physical-chemical properties. Nile tilapia (Oreochromis niloticus) farmed in recirculation aquaculture system was filleted and packaged in 100% air and 50% CO2: 50% N2 MA prior to storage at different temperature; 1˚C and -1˚C. This report further describes the development of a Quality Index Method (QIM) scheme and a sensory vocabulary for fresh and cooked tilapia fillets accordingly and application in a shelf life study. The application of the QIM scheme for tilapia fillets showed a linear relationship between QIM scores and storage time (r > 0.93) for all samples. The results from sensory analysis of cooked samples as well as microbial growth indicated that fillets packaged in 100% air had a shelf life of 13-15 days during storage at 1˚C and 20 days during storage at -1˚C. At the end of shelf life in 100% air packaged groups, TVC and pseudomonads counts reached log 7 CFU/g in flesh. In MA packaged fillets, the lag phase and generation time of bacteria was extended and recorded total counts below the limit for consumption (< log 4 CFU/g) up to 27 days of storage at both 1˚C and -1˚C. However, MA packaging affected negatively the colour characteristics of the fillets soon after packaging (as from d6) but colour is an important indicator of quality and a major factor in influencing retail purchase decisions. Chemical analyses (TVB-N and TMA) were not good indicators of spoilage of tilapia fillets in the present study. 100% air packaging at -1˚C storage temperature is the optimal storage conditions for fresh tilapia fillets. The report is based on the master thesis of Cyprian Ogombe Odoli.

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Skýrslur

The effect of liquid cooling at processing and different cooling techniques during transport of cod (Gadus morhua) fillets

Útgefið:

01/11/2009

Höfundar:

Hannes Magnússon, Lárus Þorvaldsson, Kolbrún Sveinsdóttir, Hélène L. Lauzon, Kristín Anna Þórarinsdóttir, Sigurjón Arason, Emilía Martinsdóttir

Styrkt af:

AVS R&D Fund of Ministry of Fisheries in Iceland, the Technology Development Fund at the Icelandic Centre for Research and EU (contract FP6-016333-2)

Tengiliður

Kolbrún Sveinsdóttir

Verkefnastjóri

kolbrun.sveinsdottir@matis.is

The effect of liquid cooling at processing and different cooling techniques during transport of cod (Gadus morhua) fillets

Tilgangur tilraunanna var að kanna áhrif mismunandi kælitækni og áhrif hitasveiflna á gæði og geymsluþol þorskflaka. Eftirfarandi kælitækni var könnuð: Vökvakæling í pækli við vinnslu miðað við enga kælingu og áhrif hitasveiflna við geymslu í samanburði við stöðugt hitastig (-1°C). Auk þess voru könnuð áhrif þess að nota annars vegar ísmottur og hins vegar þurrís við geymslu flakanna. Fylgst var með breytingum á hitastigi með hitanemum á öllum stigum. Sýni voru gæðametin með skynmati, örveru- og efnamælingum í allt að 14 daga frá veiði (11 daga frá vinnslu og pökkun). Mismunandi meðhöndlun leiddi til mismunandi ferskleikatíma og geymsluþols samkvæmt skynmati. Hópar sem voru vökvakældir við vinnslu höfðu um 2-3 daga skemmra geymsluþol en flök sem ekki voru kæld á þennan hátt. Rekja mátti ástæður þessa til þess að kælipækillinn innihélt töluvert magn örvera m.a. skemmdargerilinn Photobacterium phosphoreum sem er mjög virkur framleiðandi á trímetýlamíni (TMA). Samanburður á vökvakældu flökunum sýndi að notkun á þurrís lengdi geymsluþol um 1-2 daga í samanburði við ísmottur. Geymsla við -1°C hafði ekki merkjanleg áhrif á ferskleikatíma og geymsluþol í samanburði við flök þar sem hitasveiflum var beitt samkvæmt skynmati. Niðurstöður örveru- og efnamælinga voru í samræmi við þessar niðurstöður.

The aim of the experiment was to investigate the effects of different cooling techniques and temperature fluctuations on the storage life of cod fillets. The following cooling techniques were studied: liquid cooling in brine at plant as compared to no special cooling at processing. The effect of real temperature (RTS) simulation during storage was compared to a steady storage temperature at -1°C. Additionally, the influence of using either dry ice or ice packs during storage was studied. The temperature history of each group was studied using temperature loggings. The samples were analyzed with sensory evaluation, microbial and chemical methods for up to 14 days from catch (11 days from packaging). The different treatments of the groups resulted in different lengths of freshness period and maximum shelf life according to sensory evaluation. Liquid cooling resulted in a 2-3 days shorter maximum shelf life than the group that was not receiving liquid cooling. This could be attributed to the fact that the cooling brine carried considerable amounts of microbes including the spoilage bacterium Photobacterium phosphoreum which is an active producer of trimethylamine (TMA). Comparison of the groups receiving liquid cooling showed that dry ice appeared to extend the shelf life of 1-2 days as compared to ice packs. Storage at -1°C did not have much influence on the freshness period or maximum shelf life. These results were confirmed by total volatile bases (TVB-N) and TMA analysis and microbial counts.

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Skýrslur

The effect of different cooling techniques and temperature fluctuations on the storage life of cod fillets (Gadus morhua)

Útgefið:

01/08/2009

Höfundar:

Hannes Magnússon, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Björn Margeirsson, Eyjólfur Reynisson, Árni Rafn Rúnarsson, María Guðjónsdóttir, Kristín Anna Þórarinsdóttir, Sigurjón Arason, Emilía Martinsdóttir

Styrkt af:

AVS R&D Fund of Ministry of Fisheries in Iceland, the Technology Development Fund at the Icelandic Centre for Research and EU (contract FP6-016333-2)

Tengiliður

Kolbrún Sveinsdóttir

Verkefnastjóri

kolbrun.sveinsdottir@matis.is

The effect of different cooling techniques and temperature fluctuations on the storage life of cod fillets (Gadus morhua)

Tilgangur tilraunanna var að kanna tvo kælimiðla um borð í veiðiskipi, að nota mismunandi kælitækni við vinnslu, m.a. svonefnda CBC (combined blast and contact) kælingu og kanna áhrif hitastigssveiflna við geymslu í samanburði við stöðuga geymslu við -1 °C. Lítill munur var á örveru- og efnamælingum hvort sem notaður var plötuís eða vökvaís fyrir vinnslu en samkvæmt skynmati reyndist hópurinn sem var kældur með vökvaís hafa eins dags lengri ferskleikatíma og geymsluþol. Hitastig var yfirleitt aðeins hærra í hópnum þar sem plötuís var notaður fyrir vinnslu yfir geymslutímann. Samkvæmt skynmati, örverutalningum og efnamælingum reyndist CBC kæling best til lengingar á ferskleikatíma og geymsluþoli. Hitastig reyndist vera lægra í þeim hópum þar sem CBC kæling var notuð. Örverufjöldi var svipaður í þeim tveimur hópum þar sem CBC kæling var ekki notuð við vinnsluna (vökvakæling og engin kæling). Þessar niðurstöður voru í samræmi við niðurstöður skynmats. TMA gildi voru aðeins hærri á geymsludögum 12-19 í hópnum sem var vökvakældur. Niðurstöður hitastigsmælinga yfir geymslutímann voru svipaðar. Svipaður örverufjöldi reyndist vera í hópum sem geymdir voru við stöðugt hitastig (um -1 °C) annars vegar og í hópum þar sem hitastigssveiflum var beitt fyrri hluta geymslutímans hins vegar. Fyrstu 15 daga geymslunnar reyndust TVB-N og TMA gildi vera svipuð í hópunum. Þeir hópar sem geymdir voru við stöðugt hitastig fóru ekki í skynmat. Örverumælingar sem gerðar voru með hinni fljótvirku aðferð qPCR voru í góðu samræmi við ræktunaraðferðir m.t.t. til Pseudomonas spp. og Photobacterium phosphoreum.

The purpose of this experiment was to examine two different cooling methods on board fishing vessel, to apply different cooling techniques during processing at fish plant including the CBC (combined blast and contact) cooling and to compare storage of packed cod fillets kept either at steady temperature (-1 °C) or under temperature fluctuations. No marked difference was seen in microbial and chemical measurements whether plate ice or liquid ice was used prior to filleting but according to sensory analysis, the experimental group where liquid ice was used had one day extension in freshness and shelf life compared to the group with plate ice. Temperature was usually slightly higher in the plate ice group than the liquid ice group during storage. According to sensory, microbiological and chemical analysis, the CBC cooling clearly resulted in longer freshness period and shelf life extension in comparison to the two groups where this technique was not applied during processing. Temperature was lower in these groups during the storage period. Similar microbial counts were found between the two experimental groups where CBC was not applied during processing (liquid cooling and no cooling). These results were in agreement with results from sensory analysis. TMA values were however higher on storage days 12 to 19 in the group with liquid cooling. Temperature measurements during storage of these two groups were very similar. No marked difference was seen in microbial counts between groups that were stored at a constant temperature around -1 °C compared to groups where temperature fluctuations were used during early phases of storage. During the first 15 days of storage, TVB-N and TMA values were very similar for these groups. Sensory analysis was not done on the two groups kept at -1 °C. The rapid qPCR analysis was generally in good agreement with the cultivation methods for Pseudomonas spp. and Photobacterium phosphoreum.

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Skýrslur

Effect of modified atmosphere packaging (MAP) and superchilling on the shelf life of fresh cod (Gadus morhua) loins of different degrees of freshness at packaging

Útgefið:

01/09/2008

Höfundar:

María Guðjónsdóttir, Hannes Magnússon, Kolbrún Sveinsdóttir, Björn Margeirsson, Hélène L. Lauzon, Eyjólfur Reynisson, Emilía Martinsdóttir

Styrkt af:

AVS Rannsóknasjóður, Tækniþróunarsjóður Rannís

Tengiliður

Kolbrún Sveinsdóttir

Verkefnastjóri

kolbrun.sveinsdottir@matis.is

Effect of modified atmosphere packaging (MAP) and superchilling on the shelf life of fresh cod (Gadus morhua) loins of different degrees of freshness at packaging

Tilgangur þessarar tilraunar var að meta áhrif loftskiptra umbúða (MAP) og ofurkælingar á gæðabreytingar og geymsluþol þorskbita af misfersku hráefni sem var unnið og pakkað eftir 2 og 7 daga frá veiði. Tilraunin var gerð í samvinnu við Samherja, Dalvík og Norðlenska, Akureyri í október og nóvember 2007. Fiskurinn var geymdur heill í ís fram að pökkun við -0.2 ± 0.1°C (2 dagar frá veiði) og -0.2 ± 0.2°C (7 dagar frá veiði). Hnakkastykki voru skorin í tvennt og þeim var síðan pakkað (350-550 g) í loftskiptar umbúðir. Samsetning gasblöndunnar var eftirfarandi: 50% CO2, 5% O2 og 45% N2. Pakkaðir þorskbitar voru geymdir í kæligeymslu við -0.6 ± 1.4°C og sýni tekin yfir 3ja vikna geymslutíma og metin með skynmati, örveru- og efnamælingum. Aldur hráefnis við pökkun hafði greinileg áhrif á skynmat bitanna. Pökkun eftir 2 daga leiddi til lengingar á ferskleikaeinkennum framan af geymslu. Auk þess komu skemmdareinkenni mun síðar fram en í bitum sem pakkað var 7 daga frá veiði. Geymsluþol bita eftir pökkun á 7. degi má gróflega áætla 4-8 dagar en a.m.k. 19 dagar í bitum pökkuðum á 2. degi. Þetta stutta geymsluþol bita frá 7. degi má skýra með þróun örveruflórunnar og myndun rokgjarnra skemmdarefna ásamt hitastigsferli á heilum fiski fyrir pökkun. Áhrif mismunandi pökkununardags hafði veruleg áhrif á örveruflóruna. Þannig var heildarörverufjöldi mun minni í bitum sem pakkað var eftir 2 daga heldur en á 7. degi (log 3.7 vs 5.4/g). Þennan mun má að miklu leyti rekja til mismikils fjölda Photobacterium phosphoreum (Pp) í holdi rétt eftir pökkun, en hann greindist ekki við fyrri pökkun á 3. tilraunadegi (undir log 1.3/g) og á 8. degi var fjöldinn aðeins log 2.4/g. Á þeim degi var fjöldi Pp 1000x meiri í bitum pökkuðum á 7. degi og voru þeir ríkjandi út geymslutímann í þessum hópi. Á 8. degi var fjöldi annarra skemmdarörvera (H2S-myndandi gerla og pseudomonads) nokkru hærri (Δ log 0.6-0.7/g) í þessum hópi miðað við hópinn sem pakkað var á 2. degi. Þessar niðurstöður staðfesta að P. phosphoreum sé ein af aðalskemmdarörverum í gaspökkuðum þorskbitum en einnig í kældum, heilum þorski. Niðurstöður TVB-N and TMA mælinga voru í góðu samræmi við örverumælingar en þó sérstaklega Pp. Low Field Nuclear Magnetic Resonance (LF-NMR) tækni var notuð til að mæla “relaxation times” í sýnum yfir geymslutímann. Marktækt hærri “relaxation times” mældust í bitum sem pakkað var eftir 7 daga frá veiði en í bitum sem pakkað var 2 daga frá veiði. Það gefur til kynna meiri bindingu vatnssameinda við umhverfið í 7 daga bitunum. Þetta er í samræmi við almennt hærri vatnsheldni og vatnsinnihald í þeim sýnum yfir geymslutímann. Í heildina sýna niðurstöður mikilvægi þess að nota sem ferskast hráefni til MA-pökkunar og tryggja þannig meiri gæði og lengra geymsluþol sem ætti að skila sér í hærra verði vörunnar.

The aim of this study was to evaluate the effect of modified atmosphere packaging (MAP) and superchilling on the shelf life and quality changes of fresh loins prepared from Atlantic cod (Gadus morhua) of different freshness, i.e. processed 2 or 7 days post catch. The study was performed in cooperation with Samherji (Dalvík, Iceland) and Norðlenska (Akureyri) in October and November 2007. The average fish temperature during storage prior to processing on days 2 and 7 was -0.2 ± 0.1°C and -0.2 ± 0.2°C, respectively. Cod loins (350-550 g) were packed in trays under modified atmosphere (50% CO2/ 5% O2/ 45% N2), stored at -0.6 ± 1.4°C and sampled regularly over a three-week period for sensory, microbiological and chemical analyses. The results show that the raw material freshness clearly influenced the sensory characteristics of packed loins. Processing 2 days post catch resulted in more prominent freshness sensory characteristics the first days of storage. In addition, sensory indicators of spoilage became evident much later compared to MApacked fillets from raw material processed 5 days later. The expected shelf life of the MA-packed cod loins could be roughly calculated as 4-8 days when processed 7 days post catch, but at least 19 days when the cod was processed 2 days post catch. This reduced shelf life of MAP products processed at a later stage was also explained by the temperature profile of the whole fish prior to processing, microbial development and volatile amine production observed. In fact, the day of packaging had a major effect on the microflora development, with lower total viable counts (TVC) in loins processed earlier in relation to time from catch (log 3.7 vs 5.4/g). This difference could be linked to large variations in levels of Photobacterium phosphoreum (Pp) in the flesh at processing times, being below detection (log 1.3/g) 2 days post catch but found to increase to log 2.4/g in early processed loins 6 days later, in contrast to 1000-fold higher Pp levels in loins processed later. Pp was found to quickly dominate the microflora of loins processed 7 days post catch. Similarly, slightly higher levels (Δ log 0.6- 0.7/g) of other spoilage bacteria, H2S-producing bacteria and pseudomonads, were found 8 days post catch in loins processed later. These results confirm that P. phosphoreum is one of the main spoilage organisms in cod, unprocessed as MA-processed. TVB-N and TMA production corresponded well to the microbial development, especially counts of P. phosphoreum. Low Field Nuclear Magnetic Resonance (LF-NMR) was used to measure the relaxation times of the samples during storage. The samples packed 7 days after catch showed significantly higher relaxation times than samples packed 2 days after catch. This indicates stronger bindings of the water molecules to their environment in samples packed at a later stage. This is in agreement with the generally higher water holding capacity and water content in the samples during storage. Finally, the results demonstrated that delaying processing of raw material is undesirable if it is intended to be MA-packed and sold as more valuable products.

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Skýrslur

Combined Blast and Contact cooling — Effects on physiochemical characteristics of fresh haddock (Melanogrammus aeglefinus) fillets

Útgefið:

01/06/2008

Höfundar:

Magnea Guðrún Arnþórsdóttir, Sigurjón Arason, Björn Margeirsson

Styrkt af:

Tækniþróunarsjóður, AVS

Tengiliður

Sigurjón Arason

Yfirverkfræðingur

sigurjon.arason@matis.is

Combined Blast and Contact cooling — Effects on physiochemical characteristics of fresh haddock (Melanogrammus aeglefinus) fillets

Skaginn hf. hefur einkaleyfi á nýrri vinnslutækni við vinnslu ferskra og frystra flaka sem byggist á svonefndri roðkælingu fyrir roðflettingu. Tilgangur þessa rannsóknarverkefnis var að bera saman flakavinnslu með roðkælingu og hefðbundna flakavinnslu. Í verkefninu eru borin saman annars vegar fersk flök og roðkæld flök með tillit til nýtingar, gæða og geymsluþols. Tvær tilraunir voru framkvæmdar, annars vegar tilraun I þar sem vatnsheldni, gæði, suðunýting og útlit voru skoðuð, og hins vegar tilraun II þar sem þessir sömu þættir voru skoðaðir auk þess sem skoðuð var áhrif roðkælingar á aukið geymsluþol ferskrar og frosinnar ýsu. Tilraunirnar voru framkvæmdar hjá Festi ehf. í Hafnarfirði. Meginniðurstöður þessara rannsókna sýndu að flakavinnsla með roðkælingu hefur fleiri kosti en hin hefðbundna flakavinnsla. Roðkælingin gefur hærri nýtingu og verðmætari afurðir með lengra geymsluþol. Aukið geymsluþol fersks fisks gefur aukinn möguleika á útflutningi sem er mjög mikilvægt fyrir fiskiðnaðinn.

The aim of the project was to compare a new processing technique, CBC, with traditional processing of haddock fillets. In the latter the fillets go through the process without additional refrigeration. In the new processing technique, CBC, the fillets, after filleting and pre-trimming, go through pre-cooler/fluid-ice followed by CBC super-chilling. Two trials were performed, a preliminary experiment (I) and a main experiment (II). In the preliminary experiment (I), water holding capacity, quality and cooking yield were examined. In the main experiment (II) these same factors were examined, in addition to the superchilling effect on extended shelf-life of fresh and frozen haddock fillets. After the pre-cooler step, the fillets gained weight with yields of 101.6% to 102.7%. After the CBC super-chilling the fillets had final yields of 100.3% to 101.2%. After skinning, the fillets without refrigeration (traditional processing) lost most weight. The highest value of cooking yield was obtained in CBC super-chilled fillets with skin. Skinless traditional and CBC super-chilled fillets showed similar cooking yield (P>0.05). CBC super-chilling increased the total yield of the fillets. The difference between the traditional fillets and the super-chilled fillets was significant. The appearance of the CBC super-chilled fillets was much better and with less gaping than the traditional fillets. The traditional fillets had more ragged outlines, and the ratio of cut-offs after fine-trimming was therefore higher for the traditional fillets than the CBC super-chilled fillets. Appearance of the traditional fillets showed a little yellow tinge which increased during the storage time. The CBC super-chilled fillets had a whiter and more “fresh” appearance and were therefore more attractive. Examination of total bacterial count, and amount of TMA and TVN showed that the CBC super-chilling process can extend the shelf life of fresh haddock fillets.

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Skýrslur

Áhrif undirkælingar á saltupptöku við pæklun þorskhnakkastykkja (Gadus morhua)

Útgefið:

01/06/2008

Höfundar:

Ragnhildur Einarsdóttir, María Guðjónsdóttir, Sigurjón Arason

Styrkt af:

Rannsóknasjóður Rannís

Tengiliður

Sigurjón Arason

Yfirverkfræðingur

sigurjon.arason@matis.is

Áhrif undirkælingar á saltupptöku við pæklun þorskhnakkastykkja (Gadus morhua)

Saltupptaka og geymsluþol roð- og beinlausra flakabita þorsks (Gadus morhua) var rannsakað við mismunandi hitastig. Saltupptaka var skoðuð við 0,5°C, -2°C og 5°C. Niðurstöður benda til þess að fiskvöðvi taki upp salt hraðar við -2°C en 5°C og saltupptaka gerist hraðast fyrstu 5 mínúturnar. Þegar leitað er eftir því að lokastyrkur salts sé 0,6% þá er 4% saltpækill æskilegastur. Við geymsluþolstilraun var hitastigið 0°C annars vegar og – 2°C hins vegar. Geymsluþol flakabita sem geymdir voru við -2°C reyndust hafa 3-4 daga lengri geymsluþol en þeir sem geymdir voru við 0°C. Ensímvirkni, nánar tiltekið trypsínlík próteasavirkni var skoðuð í ofurkældum fiskvöðva. Fiskvöðvi með 0,5% saltinnihald geymdur við -2°C reyndist hafa hærri virkni en aðrir hópar. Rannsóknin bendir til að áhugavert væri að skoða samspil meðhöndlunar, hitastigs og ensíma nánar.

The salt uptake during brining and shelf life of skinless and boneless cod loins (Gadus morhua) was investigated at different temperatures. The salt uptake was studied at 0.5°C, -2°C and 5°C. The results show that the salt uptake of the cod muscle is faster at -2°C than at 5°C and that the salt uptake is fastest during the first 5 minutes. When aiming for a salt concentration of 0.6% in the muscle during brining it is optimal to use a 4% salt brine. In the shelf life study, samples were stored at 0°C and -2°C. The cod loins stored at -2°C showed 3-4 days longer shelf life than samples stored at 0°C. Enzymatic activity, or trypsine like protease activity to be more precise was studied in the superchilled muscle. Cod muscle with 0.5% salt and stored at -2°C showed higher activity than other groups. The study shows that there is a need for further studies on the combined effects of processing and storage temperatures on enzymatic activity.

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Geymsluþolstilraunir á þorskbitum: Áhrif ofurkælingar, pæklunar og gaspökkunar á gæðabreytingar og geymsluþol / Storage trials on cod loins: Effect of superchilling, brining and modified atmosphere packaging (MAP) on quality changes and sensory shelf-life

Útgefið:

01/05/2007

Höfundar:

Hannes Magnússon, Hélène L. Lauzon, Kolbrún Sveinsdóttir, Ása Þorkelsdóttir, Birna Guðbjörnsdóttir, Emilía Martinsdóttir, Guðrún Ólafsdóttir, María Guðjónsdóttir, Sigurður Bogason, Sigurjón Arason

Styrkt af:

AVS rannsóknasjóður í sjávarútvegi, Tækniþróunarsjóður (Rannís)

Tengiliður

Kolbrún Sveinsdóttir

Verkefnastjóri

kolbrun.sveinsdottir@matis.is

Geymsluþolstilraunir á þorskbitum: Áhrif ofurkælingar, pæklunar og gaspökkunar á gæðabreytingar og geymsluþol / Storage trials on cod loins: Effect of superchilling, brining and modified atmosphere packaging (MAP) on quality changes and sensory shelf-life

Markmið þessara tilrauna var að meta áhrif ofurkælingar, lofskiptra umbúða (MAP) og pæklunar á gæðabreytingar og geymsluþol þorskbita. Þá voru könnuð áhrif gaspökkunar og mismunandi geymsluhita á vöxt nokkurra sýkla og bendiörvera. Tilraunin var framkvæmd í október 2006 hjá Samherja á Dalvík. Eftir lageringu (0,6 og 2% salt) var fiskurinn snyrtur og hnakkastykkjum pakkað annars vegar í hefðbundnar 3 kg frauðplastpakkningar (loftpökkun) og hins vegar í loftskiptar umbúðir. Gasblandan var stillt á 50% CO2, 5% O2 og 45% N2. Þrír bitar (350- 550g) voru settir í hvern bakka með þerrimottu. Eftir pökkun var sýnunum komið fyrir í frystihermum Matís sem stilltir voru á 0°C, -2°C og -4°C. Sýnin voru rannsökuð yfir fjögurra vikna geymslutímabil. Skynmat, örverutalningar og efnamælingar voru notaðar til að meta gæðabreytingar og geymsluþol. Pæklaður (2% salt) fiskur geymdist skemur en ópæklaðir (0,6% salt). Samanburður á örverufjölda daginn eftir pökkun sýndi að pæklaði fiskurinn innihélt tífalt meira af kuldaþolnum örverum en ópæklaður. Samkvæmt skynmati var geymsluþol pæklaða fisksins við -2°C 12-15 dagar í bæði loft- og gaspökkuðum bitum. Í ópæklaða fiskinum voru áhrif gaspökkunar og ofurkælingar greinileg. Geymsluþol loftpakkaðra bita var um 11 dagar við 0°C en 14-15 dagar við -2°C. Geymsluþol gaspakkaðra bita var hins vegar um 15 dagar við 0°C en um 21 dagur við -2°C. Ofurkæling ferskra ópæklaðra fiskafurða í loftskiptum umbúðum getur því aukið geymsluþol verulega. Gaspökkun dró verulega úr vaxtarhraða sýkla og bendiörvera við lágt hitastig. Mest voru áhrifin á vöxt Salmonella, þá á Escherichia coli en minnst á Listeria monocytogenes. Við loftskilyrði óx L. monocytogenes við -2°C, en E. coli byrjaði að fjölga sér við 5°C og Salmonella við 10°C.

The aim of these experiments was to evaluate the effect of superchilling, modified atmosphere packaging (MAP) and brining on the quality changes and sensory shelf-life of cod loins. The effect of MAP and different storage temperatures on some pathogenic and indicator bacteria was also tested. These experiments were initiated in October 2006 at Samherji, Dalvík. After brining (0,6 og 2% salt) the fish fillets were trimmed, and loins packed on one hand in 3 kg styrofoam boxes (air) and on the other in MA. The gas mixture used was 50% CO2, 5% O2 and 45% N2. Three pieces (350-550 g) were placed in each tray with an absorbing mat. After packaging the samples were placed in 3 coolers at Matís which were adjusted to 0°C, -2°C and -4°C. Samples were examined over a four-week period. Sensory analysis, microbial counts and chemical measurements were used to determine the quality changes and shelf-life. Brined loins had a shorter shelf-life than unbrined (0,6% salt). Comparison on numbers of microorganisms the day after packaging revealed that the brined pieces contained ten times more microbes than the unbrined ones. According to sensory analysis the shelf-life of the brined loins at -2°C was 12-15 days for both air- and MA-packed fish. In the unbrined loins the effects of superchilling and MAP were obvious. The shelf-life of air-packed loins was about 11 days at 0°C and 14-15 days at -2°C. The shelf-life of MA-packed loins was about 15 days at 0°C but 21 days at -2°C. Superchilling of unbrined fish under MA can therefore increase the keeping quality considerably. MA-packaging clearly decreased the growth rate of pathogenic and indicator bacteria at low storage temperatures. Most effects were seen with Salmonella, then Escherichia coli but least with Listeria monocytogenes. In fact, L. monocytogenes could grow at -2°C under aerobic conditions, while proliferation of E. coli was first observed at 5°C but 10°C for Salmonella.

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