Following changes in total number of mesophilic bacteria and torry meter readings in samples of fresh trout packaged in modified atmosphere and vacuum | Praćenje promena ukupnog broja mezofilnih bakterija i torimetrijske vrednosti u uzorcima sveže pastrmke upakovane u modifikovanu atmosferu i vakuum

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%).