On the need for another type of predictive model in structured foods

Kinetics of migration of colloidal particles in meat muscles in the absence and presence of a proteolytic enzyme to simulate non-motile bacteria penetration

“…The microorganisms studied there diffused some centimeters over hours or days, which led to calculated apparent diffusion coefficients that were 3 log levels higher than the ones calculated in this study (Table 1). Moreover, determination of diffusion coefficients of Escherichia coli in liquid model systems yielded diffusion coefficients of 1.6 × 10 −8 to 5.5 × 10 −11 m 2 /s (Adler & Dahl, 1967;Dens & Van Impe, 2001;Lovely & Dahlquist, 1975). These findings are in line with the calculated apparent diffusion coefficients shown in Table 2.…”

“…The distance that particles traveled over a defined time was determined by image analysis and is hence referred to as the mean distance. If the apparent diffusion coefficient is very high the particles can diffuse without any limitations whereas an apparent diffusion coefficient of zero indicates no movement of particles in the system (Dens & Van Impe, 2001). …”

“…There authors concluded that the diffusion coefficient of bacteria in structured foods should be around 1.39 × 10 −12 m 2 /s (Dens & Van Impe, 2001). Meat may be seen as a mixture of liquids and solids, because in the intermediate spaces the sarcoplasm is in a (partially) liquid state, while the surrounding meat fibers are in a solid state.…”

Low Pore Connectivity Increases Bacterial Diversity in Soil

“…Using a 16S rRNA community fingerprinting approach, we showed that bacterial diversity in soil increased as water potential decreased (water content decreased) ( Table 1). Previous studies have shown that the coexistence of different bacterial species is favored by low water potential (16,17,30,31,48). However, these studies measured competition between only two bacterial species for a single substrate and were either modeling studies (17,30,31) or laboratory studies using agar or artificial soil (16,48).…”

“…Low pore connectivity in soil may hinder the capacity of competitive organisms to decrease substrate availability to competitors and create opportunities for diffusional and spatial "sheltering" of less competitive organisms (30,48). In modeling studies of bacterial competition, slow diffusion of substrates and low motility were thought to explain the coexistence of competing bacteria on rough surfaces (30,31) and in solid foods (17). The theory of pore connectivity may provide a fundamental theory to explain the high diversity of bacteria in soil.…”