A mathematical model that predicts the decimal reduction time (D 72C ) of Salmonella Typhimurium (ATTC 13311) as a function of citrus model system (CMS) pH (2.56-4.74), titratable acidity (TA) (0.01-2.76% citric acid) and soluble solids (SS) (4. ) was established. The D 72C values of the reference strain in different CMS were fitted into a second order model. Regression analysis of variance and goodness-of-fit assessments showed that the model was highly significant (P < 0.0001). The linear influences of pH and SS and quadratic influences of all physicochemical properties on D 72C were significant (P < 0.05). The smallest positive D 72C resulted in pH, TA and SS levels of 3.00, 2.20% citric acid and 16.85°Brix, respectively. Direct and inverse relationships were established between D 72C values and pH and D 72C values and at >0.65% citric acid TA, respectively. Survival rates were optimum at the SS value of 11.50°Brix when pH is 3.00 and TA is 2.20% citric acid. PRACTICAL APPLICATIONSDespite being one of the more effective and cheaper means of food preservation, thermal processing has a limitation of being dependent on intrinsic food properties. Therefore, even similar food products, like fruit juices, but with differing physicochemical properties should be subjected to unique process schedules. As the establishment of specific processes for separate food 3 Corresponding author. A.products can be painstakingly difficult, processors often apply generic thermal processes that result in under-or overprocessing and negatively affect food safety and quality. Therefore, this study tried to address this gap by developing a predictive model that can estimate the 72C decimal reduction time (D 72C ) of Salmonella Typhimurium (ATCC 13311) from the pH, soluble solid (°Brix) and titrable acidity (% citric acid) of citrus juices. Utilization of the model to establish unique thermal processes for specific citrus juices against the pertinent target pathogen is a convenient alternative to the more traditional but rigorous process.
Aims: Decimal reduction times (D-values) of the vegetative cells of Pyrodinium bahamense var. compressum and Escherichia coli in ultraviolet-and chlorine-treated seawater were established. Methods and Results: The cells of the test organisms were exposed to ultraviolet-and chlorine-treated seawater and maintained at 20±35 ppt salinity and 20 to 35°C. The dino¯agellate cells which cause Paralytic Shell®sh Poisoning (PSP) were found to be more resilient than the bacterial cells. Ultraviolet treatment was found to be more effective than chlorine to both test organisms. Irreversible morphological changes in the treated dino¯agellate cells were noted, including protoplast discoloration, cellular membrane leakage and damage to the thecal armour. Conclusions: The vegetative cells of both test organisms in seawater were more sensitive to ultraviolet treatment than to chlorine exposure. Generally, the dino¯agellate cells were less susceptible than bacterial cells to both disinfection treatments. Signi®cance and Impact of the Study: Results of this study may have signi®cant implications in depuration procedures for molluscs and cleaning protocols for ballast waters of ships.
The consumer acceptability of a Philippine cultivar quick‐cooking rice (QCR) as food for use in a disaster was studied. Test feeding in an evacuation centre involved random selection of 50 young adults and adult evacuees, rehydration of QCR and distribution of test rice samples for sensory evaluation test. The sensory evaluation results showed that more than 90% of the evacuee participants found the colour, texture, taste and overall qualities of the rehydrated QCR to be acceptable. Eighty per cent of the participants described the rehydrated rice to be adequately soft and neither undercooked nor overcooked. The test QCR samples were described by the community kitchen personnel of the evacuation centre as easy to prepare, requiring minimum cooking time and exhibiting homogeneity in doneness when cooked.
Cysts propagated by the agar block method with heat-killed Escherichia coli as nutrient overlay were inoculated into Perna viridis broth (PVB) and phosphate-buffered saline (PBS) prior to exposure to 60, 75 and 100"C for O, 3, 5, and 10 min. The heat resistance ofAcanthamoeba sp. cysts expressed in of D-and Zvalues were found to be greater in the complex organic PVB than in the aqueous PBS. The established Dvalues in the PVB were 81.20, 44.59, and 8.83 min at 60, 75, and 100'C, respectively. The calculated Z-value ofAcanthamoeba sp. cysts in PVB was 40.28'C.
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