CHILLING AND CONTROLLED ATMOSPHERE FOR KEEPING MICROBIAL SAFETY OF MINIMALLY PROCESSED CELERY STICKS

摘要

Minimally fresh processed celery as sticks is available in the markets as a fresh-cut product. Usually stored at 0 to 4°C its shelf life is about 2 to 3 weeks. In those conditions initial microbial counts increase affecting product safety and quality. The combination of controlled atmospheres (CA) and chilling temperatures could inhibit those processes. In this research the effect of two temperatures and a CA on microbial quality of celery sticks was studied. Green celery sticks of 25 cm length were placed in hermetic glass jars under a continuous flow of humidified air (control) or a CA of 5 kPa O{sub}2 plus 5 kPa CO{sub}2. Sticks were stored during 21 d at 0° and 4°C. To analyse microbial quality of the sticks at the beginning and at the end of the storage standard methods (PCA media, incubation at 7°C for 7 days and 38°C for 48 h for psychrotrophic and mesophilic bacteria respectively) were used. After 21 days of cold storage microbial growth was significant for all treatments except for mesophiles under CA at 0°C. Growth of mesophiles under CA at 4°C was the same that under air at 0°C, being the highest growth at 4°C under air. For psychrophiles the use of CA and 0°C gave the best results. However, for all the CA, microbial counts were below the maximum level accepted by Spanish legislation. CA and chilling kept the microbial quality of celery sticks up to 21 days and, even when CA effect at 4°C was lower than at 0°C, it allowed to extend its storage life for 7 days over the typically obtained by the fresh processing industry.