Following changes in total number of mesophilic bacteria and torry meter readings in samples of fresh trout packaged in modified atmosphere and vacuum

Abstract

Today, food must be healthy, subjected to minimal processing, and attractively packaged, as the expectations of consumers are ever higher. Consumers are highly sensitive to the use of additives in the food industry. There is a constant demand for fresh food that does not contain any unnecessarily added chemicals. In order to prevent spoilage of food items, an efficient and intelligent concept for preserving freshness has been developed - packaging in a modified atmosphere. Changes in a certain composition of the atmosphere within the packaging have resulted in a longer shelf life and a satisfactory quality of the food articles. Modified atmosphere packaging (MAP) is well-known and has been applied in practice in the food processing industry for more than one century. The objective of these investigations was to determine the growth of the total number of mesophilic bacteria in the meat of trout packaged in a vacuum and a modified atmosphere and torry meter reading results due to changes in the dielectric characteristics of the skin that take place during the period of storage of the fresh fish. California trout (Oncorhynchus mykiss) with an average weight of 293 g was used for the experimental part of the investigations. Four groups of fish samples were set up for the research. The first three groups of samples were packaged in a modified atmosphere with a different ratio of gases: Group I - 60%CO2+40%N2; Group II - 40%CO2+60%N2; Group III - 90%CO2+10%N2. Group IV comprised samples packaged in a vacuum. Investigations were carried out on days 0, 7, 14, and 21 of storage. The total number of mesophilic bacteria in the examined samples was determined according to the method ISO 4833. Measurements of changes in the dielectric characteristics of the fish skin were performed using a torry meter apparatus (The Torry Fish Freshness Meter). The results have shown that packaging of fresh trout in a modified atmosphere (60% CO2 + 40% N2 and 40% CO2 + 60% N2) has an advantage regarding the growth of the total number of mesophilic bacteria and the decreased torry meter readings in comparison with vacuum packaging and packaging with a higher concentration of carbon dioxide (90%).

Svest potrošača o zdravoj ishrani danas je na visokom nivou. Potrošači su veoma osetljivi kada je u pitanju upotreba aditiva u industriji hrane. Zahtev je da se, u svakom trenutku, može nabaviti sveža hrana bez nepotrebno dodatih hemikalija. Da bi se sprečio kvar namirnica razvijen je efikasan i inteligentan koncept očuvanja svežine – pakovanje u modifikovanu atmosferu. Promenom određenog sastava atmosfere unutar pakovanja postignuti su duža održivost i zadovoljavajući kvalitet namirnica. Pakovanje u modifikovanu atmosferu (MAP) je poznato i primenjuje se u oblasti prerade namirnica duže od jednog veka. Cilj ovog istraživanja je utvrđivanje rasta ukupnog broja mezofilnih bakterija u mesu pastrmke upakovane u vakuum i modifikovanu atmosferu i kretanje torimetrijske vrednosti usled promena dielektričnih svojstava kože koja se dešavaju tokom perioda skladištenja sveže ribe. Za eksperimentalni deo rada korišćena je kalifornijska pastrmka (Oncorhynchus mykiss) prosečne mase 293 g. Za potrebe istraživanja formirane su četiri grupe uzoraka ribe. Prve tri grupe uzoraka upakovane su u modifikovanu atmosferu sa različitim odnosom gasova: grupa I – 60%CO2+40%N2; grupa II – 40%CO2+60%N2; grupa III – 90%CO2+10%N2. Uzorci grupe IV upakovani su u vakuum. Ispitivanja su rađena nultog, sedmog, četrnaestog i dvadesetprvog dana skladištenja. Određivanje ukupnog broja mezofilnih bakterija u ispitivanim uzorcima vršeno je prema metodi ISO 4833. Merenje promene dielektričnih svojstava na koži ribe obavljeno je pomoću aparata torimetar (The Torry Fish Freshness Meter). Rezultati su pokazali da pakovanje sveže pastrmke u modifikovanoj atmosferi (60% CO2 + 40% N2 i 40% CO2 + 60% N2) ima prednosti u pogledu rasta ukupnog broja mezofilnih bakterija i opadanja torimetrijske vrednosti u odnosu na vakuum pakovanje i pakovanje sa većom koncentracijom (90%) ugljen-dioksida.