Field Validation of Predictive Models for the Growth of Lactic Acid Bacteria in Acidic Cheese-Based Greek Appetizers

Abstract

A microbial model was developed for spoilage of two acidic Greek appetizers, namely, tyrosalata (TS) and tyrokafteri (TK), with pH values of 4.34 to 4.50 and 4.22 to 4.38, respectively. The specific spoilage organisms of these products were lactic acid bacteria (LAB), which dominated during storage, while yeasts, whenever present, remained at low levels (1 to 2 log CFU/g). Correlations of LAB populations with changes in pH and sensory characteristics indicated that the spoilage level of LAB ranged from 8.1 to 8.6 log CFU/g for both products. TK showed a relatively higher microbial stability than did TS. The growth of LAB was modeled with the Baranyi model, while their maximum specific growth rates were further modeled as a function of temperature with square-root model and Arrhenius equations for each appetizer. The validation of the model was performed under nonisothermal conditions in the laboratory and in a field validation trial with temperature logging during distribution of individual packages in the chill supply chain, including transportation from the plant to the distribution center, retail display, and household refrigerators. Models for both appetizers showed satisfactory agreement with data, with a slight tendency of overprediction of LAB in TS. The field validation process also confirmed the higher stability of TK over TS. The developed models may serve as a useful tool for monitoring the microbiological quality of such complex products and manage their distribution. Furthermore, depending on the seasonal variation of chill chain conditions, reassessment of shelf life may be performed.

Towards biotracing in food chains

“…▪ Development in detection technologies for Salmonella, Bacillus, Clostridium, Norovirus, and extraction technology for S. aureus (Josefsen et al, 2007;Fach et al, 2009) ▪ Sampling strategies and innovative sampling technology for Salmonella, Campylobacter, B. cereus and B. anthracis (Reiter et al, 2009;Andersson and Haggblom, 2009) ▪ Mathematical modelling approaches and models developed, such as modular process risk modelling for Salmonella and domain models for S. aureus in milk and Salmonella in pork (Barker et al, 2009) ▪ Incorporation of field sampling data into models (Manios et al, 2009) ▪ Improved understanding of pathogen physiology and immobilised cells (Belessi et al, 2008).…”

Biotracing: a new integrated concept in food safety

“…· Food chain and mathematical models have been linked to developments in detection and tracing technologies. The matrix of data generated is the basis for predicting the behaviour of pathogens under given conditions in relevant scenarios (Manios et al 2009, Schvartzman et al 2010b). · There have been developments in novel sampling and sample preparation technologies to overcome existing bottlenecks in end-use analytical laboratories (Olsen et al 2009).…”

“…The concept of biotracing in the dairy chain will be enhanced by recent advances in knowledge of the physiology of L. monocytogenes and S. aureus and the inclusion of additional parameters into mathematical models (Manios et al 2009, Schvartzman et al 2010b, Reichert-Schwillinsky et al 2009). Development and validation of an ELISA method for S. aureus enterotoxins (Wallin-Carlquist et al 2010), knowledge of the factors controlling enterotoxin production in conditions corresponding to the dairy chain from farm to the consumer and transcriptional changes in S. aureus enterotoxin under different conditions all contribute to biotracing.…”

Growth potential of Listeria monocytogenes in ready‐to‐eat Feta cheese‐based sauce stored at 4°C

“…Furthermore, the use of chemical preservatives, such as sorbic and benzoic acid, along with salt and sugar concentrations corresponding to a certain level of water activity ( A w ; e.g., A w > 0.964), are crucial factors affecting microbial growth in these products (Tiganitas, Zeaki, Gounadaki, Drosinos, & Skandamis, ; Vermeulen et al, ). The shelf‐life of acidic cheese‐based salads and sauces normally exceeds 1–2 months when these products are properly refrigerated (Manios et al, ). Alterations in product composition regarding the aforementioned ingredients (i.e., organic acids, chemical preservatives, A w ) result not only in products with desirable changes to their organoleptic features but also to differences in their microbiological safety.…”

“…The shelf-life of acidic cheese-based salads and sauces normally exceeds 1-2 months when these products are properly refrigerated (Manios et al, 2009). Alterations in product composition regarding the aforementioned ingredients (i.e., organic acids, chemical preservatives, A w ) result not only in products with desirable changes to their organoleptic features but also to differences in their microbiological safety.…”