• Preventive Nutrition and Food Science
• /
• v.16 no.4
• /
• pp.364-369
• /
• 2011

Levels of carbon dioxide gas, a metabolite of microbial growth, have been reported to parallel the onset of microbial spoilage and may be used as a convenient index for a packaged food's shelf life. This study aimed to establish a kinetic model of $CO_2$ production from perishable food for the potential use for shelf life control in the food supply chain. Aerobic bacterial count and package $CO_2$ concentration were measured during the storage of seasoned pork meat at four temperatures (0, 5, 10 and $15^{\circ}C$), and their interrelationship was investigated to establish a mathematical model. The microbial growth at constant temperature was described by using model of Baranyi and Roberts. $CO_2$ production from the stored food could be explained by taking care of its yield and maintenance factors linked to the microbial growth. By establishing the temperature dependence of the microbial growth and $CO_2$ yield factor, $CO_2$ partial pressure or concentration in package headspace could be estimated to a limited extent, which is helpful for controlling the shelf life under constant and dynamic temperature conditions. Application and efficacy of the model needs to be improved with further refinement in the model.

• Preventive Nutrition and Food Science
• /
• v.13 no.2
• /
• pp.104-111
• /
• 2008

As a way to account for the variability of the primary model parameters in the secondary modeling of microbial growth, three different regression approaches were compared in determining the confidence interval of the temperature-dependent primary model parameters and the estimated microbial growth during storage: bootstrapped regression with all the individual primary model parameter values; bootstrapped regression with average values at each temperature; and simple regression with regression lines of 2.5% and 97.5% percentile values. Temperature dependences of converted parameters (log $q_o$, ${\mu}_{max}^{1/2}$, log $N_{max}$) of hypothetical initial physiological state, maximum specific growth rate, and maximum cell density in Baranyi's model were subjected to the regression by quadratic, linear, and linear function, respectively. With an advantage of extracting the primary model parameters instantaneously at any temperature by using mathematical functions, regression lines of 2.5% and 97.5% percentile values were capable of accounting for variation in experimental data of microbial growth under constant and fluctuating temperature conditions.

• Preventive Nutrition and Food Science
• /
• v.13 no.4
• /
• pp.348-353
• /
• 2008

Aerobic bacterial growth on Korean pan.fried meat patties as a primary quality deterioration factor was modeled as a function of temperature to estimate microbial spoilage on a real.time basis under dynamic storage conditions. Bacteria counts in the stretch.wrapped foods held at constant temperatures of 0, 5, 10 and $15^{\circ}C$ were measured throughout storage. The bootstrapping method was applied to generate many resampled data sets of mean microbial counts, which were then used to estimate the parameters of the microbial growth model of Baranyi & Roberts in the form of differential equations. The temperature functions of the primary model parameters were set up with confidence limits. Incorporating the temperature dependent parameters into the differential equations of bacterial growth could produce predictions closely representing the experimental data under constant and fluctuating temperature conditions.

• Korean Journal of Veterinary Service
• /
• v.40 no.2
• /
• pp.119-131
• /
• 2017

Among different types of spoilage, microbial contamination can cause feed decomposition, which results in decreases in feed intake and productivity, infection, and breeding disorder. During the storage time, various microbes have a chance to inoculate with depreciation of feed and to infect the animals. We investigated bacteria that inhabit diverse feed ingredients and complete feed which have been stored for a few months. We isolated and identified 30 genera and 62 species of bacteria. Among these 62 species, 21 species were of non-pathogenic bacteria, 18 species were of pathogenic bacteria, 9 species were of opportunistic pathogens, and 14 species were of unknown bacteria. Pantoea allii and 24 species showed proteolytic enzyme activity. We also confirmed that 6 species including Pseudomonas psychrotolerans showed ${\alpha}$-amylase activity, and 29 species including Burkholderia vietnamiensis showed cellulase activity. Microbacterium testaceum and 3 species showed resistance to Ampicillin, Kanamycin, Streptomycin, Gentamicin, Carbenicillin, and Erythromycin ($50{\mu}g/mL$). Using mealworm larvae (Tenebrio molitor L.) as a model for pathogenicity, we confirmed that 8 species including Staphylococcus xylosus had pathogenicity for mealworm larvae. Especially, Enterobacter hormaechei, Staphylococcus xylosus, and Staphylococcus hominis were reported as being pathogenic for humans. This research suggests that hygienic management of animal feed is essential because beneficial and harmful bacteria can inhabit animal feed differently during storage and distribution.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.23 no.2
• /
• pp.75-81
• /
• 2017

Modified atmosphere packaging (MAP) of vacuum, 60% $N_2/40%$ $CO_2$, 100% $N_2$ and 100% $CO_2$ were examined to preserve fried fish cakes and extend their shelf life. When product packages in air were stored at 5, 10, and $15^{\circ}C$ with measurement in quality attributes, aerobic bacterial growth was found to be primary quality factor to determine the shelf life of the product. Huang's model was adopted to obtain the parameters for use in shelf life determination for a variety of packaging and storage conditions. Temperature dependence expressed in Arrhenius equation showed activation energies of 139.4 and 41.8 kJ/mol for inverse of lag time and growth rate of the microbial spoilage, respectively. MAP of 100% $CO_2$ could double the product shelf life at $10^{\circ}C$ compared to air package. High $CO_2$ concentration MAP at low temperature was found to be effective to prolong the shelf life.