Comparative study of selected quality parameters of marinated mackerel packed in vacuum and modified atmosphere

Mariniranje je jedan od starijih postupaka konzervisanja ribe i često se primenjuje u Evropi. Ovaj postupak se najčešće koristi za ribe sa većim sadržajem masti, kao što su sardina, skuša, haringa, a ne retko se koristi i za konzervisanje rakova i školjki. Uopšteno govoreći, održivost i bezbednost mariniranih proizvoda od ribe i plodova voda, u koji nije uključena toplotna obrada, zavisi od vrste organske kiseline koja se koristi za mariniranje i koncentracije soli. Poznato je da je pH niži od 4,5 dovoljan da se produži održivost ribe. Međutim, niske pH vrednosti marinade mogu da uzrokuju jak, kiseo ukus. Termin „marinada“ ili „marinirana riba“ se koristi za ribu koja se za mariniranje koristi kao sveža, odmrznuta ili samo soljena, a tretirana je sa jestivim organskim kiselinama, najčešće sirćetnom kiselinom. Marinirana riba se posle završenog mariniranja pakuje najčešće u vakuumu ili modifikovanoj atmosferi, Čime se održivost marinirane ribe produžava. Ambalažiranje hrane, pa i ribe, ima za cilj da potrošačima pruži i osnovne informacije o ribi, a naročito o uslovima čuvanja i o roku trajanja. S tim u vezi, današnju prehrambenu industriju karakteriše posebno razvoj jednog njenog segmenta, a to je pakovanje hrane. Cilj istraživanja u okviru ove doktorske disertacije je bio ispitivanje uticaja pakovanja soljene, odnosno marinirane ribe (skuše) u vakuumu i modifikovanu atmosferu na održivost i odabrane parametre kvaliteta. U eksperimentu je korišćena skuša konzumne veličine (mase od 350-400 grama) koja je obrađena na način uobičajen za industrijski objekat koji se bavi obradom ribe. Riba je obrađena tako da je za soljenje, mariniranje, odnosno, pakovanje korišćen primarno obrađen trup. Riba je podeljena u dve podgrupe, od kojih je jedna podgrupa tretirana samo u slanom rastvoru (10 % soli), a druga podgrupa marinirana u marinadi sa 10 % soli i sa 0,5 % sirćetne kiseline. Tretiranje ribe trajalo je dvadeset četiri sata. Prva podgrupa je podeljena u dve grupe od kojih je jedna pakovana u vakuum (prva grupa), a druga grupa u modifikovanu atmosferu (40 % CO2+60 % N2). Na isti način je podeljena i druga podgrupa i pakovana u vakuum (treća grupa), odnosno modifikovanu atmosferu (40 % CO2+60 % N2) (četvrta grupa). Svi uzorci su skladišteni pri istim kontrolisanim uslovima. Temperatura skladištenja je bila 4 °C. Na početku eksperimenta i na svakih deset dana, tokom pedeset dana, vršene su mikrobiološke (ukupan broj bakterija, ukupan broj enterobakterija, broj psihrotrofa, broj anaerobnih bakterija, broj bakterija mlečne kiseline), hemijske (osnovni hemijski sastav, sadržaj ukupnog isparljivog azota, malondialdehid i histamina), fizičko-hemijske (pH vrednost i aw vrednost) i senzorne analize...The marinating process is one of the oldest preservation methods of fish, and is often used in Europe. This method is commonly used for preservation of the fish with a higher fat content, such as sardines, mackerel, herring, but for the crustaceans and molluscs as well. Generally, shelf life and safety of the marinated fish and seafood, without temperature treatment, depends on the type of organic acid which is used for marinating, and the concentration of salt. It is known that the pH values lower than 4.5 are sufficient to prolong the shelf life of the fish. However, the low pH values of the marinade may cause strong acidic taste. The terms marinade or marinated fish refer to fish products consisting of fresh, frozen, or salted fish or portions of fish treated with an edible organic acid, usually acetic acid. After completing marinating, fish is usually packed in vacuum or modified atmosphere, which is a way to prolong shelf life of marinated fish. The aim of food, including fish labelling is to provide consumers with key information about the fish, and especially on storage conditions and expiration date of the product. In this regard, nowadays, food industry in particular is characterized by the development of food packaging segment. The aim of the study within this PhD thesis was to investigate the influence of packaging of salted and marinated fish (mackerel) in vacuum and modified atmosphere on the shelf life and selected quality parameters. In the experiment it has been used commercial size mackerel (a mass of 350-400 g), which is treated in the manner customary for industrial plant which deals with processing of fish. Fish is processed so that for salting, marinating, and packaging has been used primarily processed fish carcasses. The fish was divided into two subgroups, first which was treated only with saline (10% salt), and a second subgroup which was marinated in a 10% salt and 0.5% acetic acid. The fish was treated for twenty-four hours. The first sub-group is divided into two groups, one of which is packaged in a vacuum (the first group), and the second group in modified atmosphere (40% CO2 + 60% N2). In the same way the other sub-groups were divided and packed in a vacuum (the third group), or a modified atmosphere (40% CO2 + 60% N2) (fourth group)..

Effect of modified atmosphere and vacuum packaging on selected chemical parameters of rainbow trout (Oncorhynchus mykiss) and carp (Cyprinus carpio) cuts freshness

The purpose of food packing in modified atmosphere is to extend its sustainability by preventing both biochemical processes and growth of spoilage bacteria. Gases or their mixtures which are mostly used in the modified atmosphere food packing technology are carbon-dioxide (CO2), oxygen (O2) and nitrogen (N2). The aim of our research was to examine the influence of packaging in modified atmosphere and vacuum on the total volatile basic nitrogen (TVB-N) content and pH in muscle of rainbow trout (Oncorhynchus mykiss) and common carp (Cyprinus carpio), as well as to determine the most suitable gas mixtures for packing of these freshwater species. Three sample groups of trout and carp cuts were investigated. The first two groups were packaged in modified atmosphere with different gas ratios: 60%CO2+40%N2 (I group) and 40%CO2+60%N2 (II group), whereas the samples from third, control group, (III group) were vacuum packaged. During trials samples were stored in refrigerator at +3°C. Determination of TVB-N and pH was performed on 1st, 7th and 14th day of storage. The obtained results indicate that the investigated mixtures of gases and vacuum as well had a significant influence on the values of TVB-N in trout and carp cuts samples. The lowest increase in TVB-N was established in trout and carp cuts samples from the group I, whereas the highest increase was established in samples from group III. Statistical significant difference (p < 0,001) between the average values of TVB-N for trout (I group: 18,17 ± 0,93; II group: 20,90 ± 0,81 and III group: 36,18 ± 2,65 mg N/100 g ) and carp cuts (I group: 26,74 ± 1,48; II group: 30,02 ± 0,31 and III group: 35,10 ± 1,75 mg N/100 g) was established on 14th day. The lowest pH value was established in samples packaged in modified atmosphere with 60% CO2 +40% N2 (I group). On 14th day of testing the obtained value was 6,15 ± 0,09 for trout and 5,94 ± 1,11 for carp samples. Increase in pH value in trout samples packed in vacuum was established during the whole period of investigation (p < 0,001), while in carp cuts samples packaged in vacuum the increase in pH value (p < 0,05) was established up to 7th day of testing. Based on the obtained results it can be concluded that gas mixture consisting of 60% CO2 and 40% N2 was the most suitable for packaging of fresh trout and carp cuts in terms of selected chemical parameters, such as TVB-N and pH. [Projekat Ministarstva nauke Republike Srbije, br. TR 31011 i br. TR 31075