  During last years theoretical works shed new light and proposed new
hypothesis on the mechanisms which regulate the time behaviour of biological
populations in different natural systems. Despite of this, the role of
environmental variables in ecological systems is still an open question.
Filling this gap of knowledge is a crucial task for a deeper comprehension of
the dynamics of biological populations in real ecosystems. In this work we
study how the dynamics of food spoilage bacteria influences the sensory
characteristics of fresh fish specimens. This topic is crucial for a better
understanding of the role played by the bacterial growth on the organoleptic
properties, and for the quality evaluation and risk assessment of food
products. We therefore analyze the time behaviour, in fresh fish specimens, of
sensory characteristics starting from the growth curves of two spoilage
bacterial communities. The theoretical study, initially based on a
deterministic model, exploits experimental temperature profiles. As a first
step, a model of predictive microbiology is used to reproduce the experimental
behaviour of the two bacterial populations. Afterwards, the theoretical
bacterial growths are converted, through suitable differential equations, into
"sensory" scores, based on the Quality Index Method (QIM), a scoring system for
freshness and quality sensory estimation of fishery products. As a third step,
the theoretical curves of QIM scores are compared with the experimental data
obtained by sensory analysis. Finally, the differential equations for QIM
scores are modified by adding terms of multiplicative white noise, which mimics
the effects of uncertainty and variability in sensory analysis. A better
agreement between experimental and theoretical QIM scores is observed, in some
cases, in the presence of suitable values of noise intensity respect to the
deterministic analysis.
