The effect of long-term storage on the quality of sterilized processed cheese.

The aim of this work is to evaluate the effect three different storage temperatures (6, 23 and 40 °C) on the sterilized processed cheese quality during 24-month storage. Sterilized processed cheese (SPC) is a product with extended shelf life (up to 2 years). The samples of SPC were subjected to basic chemical analyses, i.e. pH-values, dry matter, fat, crude protein and ammonia content, and microbiological analyses, i.e. total number of microorganisms, number of coliforms, colony forming units of yeasts and/or moulds and spore-forming microorganisms. Furthermore, amino acid content (ion-exchange chromatography), protein profile (SDS-PAGE) and fat globules size (image analysis of microscopic technique) were monitored and sensory analysis (scale test and pair comparative test) was implemented, too. Increasing storage temperature and length evoked decrease of total amino acid content and protein nutrition value, increase of ammonia amount, protein changes, enlargement of fat globule size and deterioration of sensory properties of SPC. All the changes grew expressive with increasing storage temperature and time.