COMPREHENSIVE ASSESSMENT OF MICROBIAL CONTAMINATION AND PHYSICOCHEMICAL CHARACTERISTICS OF RETAIL AND MODEL-FORMULATED DELI SALADS

Abstract

This study evaluated the microbiological safety and selected physicochemical parameters of retail and model-formulated deli salads. The dynamics of microbial contamination (total viable count – TVC, coliform bacteria, Bacillus cereus, microscopic filamentous fungi – MFF, and yeasts) and physicochemical parameters (pH, water activity, and salt content) were monitored with respect to sample type and storage conditions. Thirteen commercial deli salads were purchased from retail display counters and analysed immediately after purchase and after 24 h of storage at 4 °C. In the second part of the study, one commercial sample and four laboratory-prepared model salads simulating gastronomic practice were evaluated. All model ready-to-eat salads (Vlašský šalát, a traditional Central European mayonnaise-based deli salad) contained identical ingredients but differed in the type of dressing (no dressing, mayonnaise, tartar sauce, or yogurt). Analyses were performed immediately after preparation and after 12, 24, and 48 h of storage at 3 °C and 8 °C. Among retail samples, the highest TVC was detected in Norwegian salad (3.38 log CFU/g) and “Devil’s” salad (3.37 log CFU/g), while the lowest was observed in Dutch salad (1.91 log CFU/g). No statistically significant differences in TVC were observed during storage (P > 0.05), although a slight increase in counts was recorded. Coliform bacteria were detected in only one sample and remained within legislative limits. Microscopic filamentous fungi and yeasts occurred at low levels (<4×10¹ CFU/g). pH remained stable, whereas two samples exceeded the permitted salt content. In model salads, storage temperature and time significantly influenced microbial growth (P < 0.05), with faster proliferation at 8 °C. Dressings showed an initial inhibitory effect which decreased after 48 h. After 48 h at 8 °C, the lowest TVC was observed in mayonnaise salad (5.22 log CFU/g) and the highest in yogurt salad (5.45 log CFU/g). Coliform bacteria were absent; however, yogurt salad exceeded the limit for Bacillus cereus (4.13 log CFU/g). Yeasts and filamentous fungi remained low in all samples. Storage caused slight increases in pH and water activity. All model salads prepared according to commonly available recipes exceeded the maximum salt content, except the yogurt variant. The results highlight the importance of storage temperature control and formulation factors in ensuring the microbiological safety of deli salads.