Investigating the effect of storage temperature and hot-water treatment on the microbial dynamics in edible oyster (Saccostrea cucullata)
01 Jan 2013-International Journal of Postharvest Technology and Innovation (Inderscience Publishers Ltd)-Vol. 3, Iss: 4, pp 382-391
TL;DR: The results indicated that oysters must be stored for a limited time as shell-stock and during cooking it should be prepared as shucked meats, and washing with boiled water is a simple method for making it microbes free.
Abstract: Oysters are an important sea food all over the world apart from shrimp and crabs. They are usually sold as a live product and can be stored for several weeks before consumption. Temperature abuse during oyster post-harvest handling may allow multiplication of natural spoilage microflora as well as pathogens, which is a potential threat to consumers and/or compromising product quality. In this study, the effect of storage temperatures (25°C, 4°C, 0°C and –10°C) and boiling on the microbial quality of shell stock and shucked meats of oysters (Saccostrea cucullata) were examined. The load of total bacteria, fungi, coliform, fecal coliform, Salmonella sp. and Streptococcus sp. were comparatively higher in shucked meat than in the shell-stock at all the storage temperatures (except Vibrio sp.) and the number of the spoilage bacteria is directly proportional to the storage time but decreased with lowering of the temperature. Microbial count also observed at various interval of treatment with boiling water (100°C). During boiling water treatment of the shell-stock and shucked meats, the decimal reduction time, D-value (D100°C) for total microbes was found to be 2.7 min and 2.4 min respectively. The results indicated that oysters must be stored for a limited time as shell-stock and during cooking it should be prepared as shucked meats, and washing with boiled water is a simple method for making it microbes free.
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TL;DR: In this paper, the effect of superchilled storage at -1°C on the microbial safety of oyster depurated with 0.2, 0.4, and 0.6 mg/L ozone was studied for 14 days.
Abstract: The effect of superchilled storage at -1°C on the microbial safety of oyster depurated with 0.2, 0.4, and 0.6 mg/L ozone was studied for 14 days. Fecal coliforms (4,100-16,000 MPN/100 g), Escherichia coli (1,500-3,650 MPN/100 g), Vibrio cholerae non-O1/non-O139 (13.0-102.0 MPN/g), and Salmonella spp. (2.270-3.035 × 103 CFU/g) were initially present in raw oysters. After 6 h depuration, fecal coliform counts decreased (P < 0.05) to 300, 20 and 20 MPN/100 g for 0.2, 0.4, and 0.6 mg/L treatments, while a 0.3 log decrease in control oysters was observed. Initial E. coli counts decreased (P < 0.05) in oysters to 50, 20, and 20 MPN/100 g for 0.2, 0.4, and 0.6 mg/L treatments, respectively. A 1 log reduction in V. cholerae non-O1/non-139 levels were observed in 0.4 and 0.6 mg/L-treatments after 2 and 4 h depuration. Salmonella spp. was not detected in oyster samples after 6 h depuration in 0.4 and 0.6 mg/L-ozone treatments. Considering the bacterial loads after depuration, at the end of superchilled storage the 0.4 mg/L-ozonated oysters attained lower (P < 0.05) fecal coliform levels (280 MPN/100 g) and E. coli counts in 0.4 and 0.6 mg/L-ozonated oysters (20 and 95 MPN/100 g, respectively). A 2-log decrease in V. cholerae non-O1/non-O139 levels on day 5 in 0.4 and 0.6 mg/L-ozonated oysters (< 0.3 MPN/g) was attained. V. cholerae non-O1/non-O139 counts in control oysters decreased 1 log on day 9 of superchilled storage. Salmonella spp. was not detected in ozonated and superchilled stored oysters. Levels of fecal coliforms, E. coli, Salmonella spp., and V. cholerae non-O1/non-O139 in non-ozone depurated oyster samples were higher than in control, 0.4 and 0.6 mg/L ozonated oyster samples during superchilled storage. The cumulative mortality rates after 14 days of storage for superchilled oysters (22.2%) was higher (P < 0.05) than 0.6 mg/L O3 (7.2%) and 0.4 mg/L O3 (5.8%) treatments, and control oysters (5.6%). pH values in control oysters decreased significantly (P < 0.05) throughout the storage period but not in oysters of both ozone treatments, indicating no detrimental effects on oyster survival. The results of this study suggest that superchilled storage enables ozonated shellstock oysters (0.4 mg/L-6 h) stored for 9 days to be safe human consumption.
15 citations
TL;DR: Depuration and proper cooking of oysters before consumption during the monsoon season is strongly recommended, and E. coli MPN values in oyster growing waters were below the threshold limits set by the USFDA and EU during the months of December to April.
Abstract: Oysters are commercially cultured from the Ashtamudi Lake in India, and support 12,000 tonnes of bivalve fisheries/year. Oysters and oyster growing waters were sampled from July 2012 to June 2013 for analysis of total coliforms (TC), faecal coliforms (FC), Escherichia coli, faecal Streptococci (FS) and total plate counts (TPC). E. coli MPN values in oyster growing waters were below the threshold limits set by the USFDA and EU during the months of December to April. Seasonally, the highest MPN values for E. coli were obtained during the monsoon season (June–September), and this trend gradually decreased during the post-monsoon (October–January) and pre-monsoon (February–May) periods. E. coli displayed a significant (p<0.01) variation in accumulation during different seasons. A strong negative correlation (R2=−0.70, p<0.05) between temperature and E. coli numbers in oysters was observed, while rainfall and E. coli were positively correlated (R2=0.695, p<0.05). Hence, we strongly recommend depuration and proper cooking of oysters before consumption during the monsoon season.
15 citations
Cites background from "Investigating the effect of storage..."
...Recently, the edible oysters are very popular as raw and processed food in the South Indian states, particularly in Kerala and Goa (Jana et al., 2013), where large number of foreigners visiting every year....
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01 Jan 2016
TL;DR: Decomposers are widely distributed in the salty blue soup of the planet Earth and occupy a key position in an ecological food chain/web and are considered as "cleaners" of the ecosystem as they are capable of degrading complex organic matter in to simpler forms as discussed by the authors.
Abstract: Decomposers are widely distributed in the salty blue soup of the planet Earth and occupy a key position in an ecological food chain/web. They are considered as ‘cleaners’ of the ecosystem as they are capable of degrading complex organic matter in to simpler forms. The vast volume of saltwater may be the reason behind the presence of wide variety and large number of decomposers in the marine and estuarine ecosystems.
References
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TL;DR: While seasonal prevalences of NoV and HAV were generally greater in oysters harvested from December to March, the low detection frequency obscured any apparent seasonal effects and there was no relationship between the levels of indicator microorganisms and the presence of enteric viruses.
Abstract: Two samples of market oysters, primarily from retail establishments, were collected twice each month in each of nine states during 2007. Samples were shipped refrigerated overnight to five U.S. Food and Drug Administration laboratories on a rotating basis and analyzed by most probable number (MPN) for total and pathogenic Vibrio parahaemolyticus and V. vulnificus numbers and for the presence of toxigenic V. cholerae, Salmonella spp., norovirus (NoV), and hepatitis A virus (HAV). Levels of indicator organisms, including fecal coliforms (MPN), Escherichia coli (MPN), male-specific bacteriophage, and aerobic plate counts, were also determined. V. parahaemolyticus and V. vulnificus levels were distributed seasonally and geographically by harvest region and were similar to levels observed in a previous study conducted in 1998-1999. Levels of pathogenic V. parahaemolyticus were typically several logs lower than total V. parahaemolyticus levels regardless of season or region. Pathogenic V. parahaemolyticus levels in the Gulf and Mid-Atlantic regions were about two logs greater than the levels observed in the Pacific and North Atlantic regions. Pathogens generally associated with fecal pollution were detected sporadically or not at all (toxigenic V. cholerae, 0%; Salmonella, 1.5%; NoV, 3.9%; HAV, 4.4%). While seasonal prevalences of NoV and HAV were generally greater in oysters harvested from December to March, the low detection frequency obscured any apparent seasonal effects. Overall, there was no relationship between the levels of indicator microorganisms and the presence of enteric viruses. These data provide a baseline that can be used to further validate risk assessment predictions, determine the effectiveness of new control measures, and compare the level of protection provided by the U.S. shellfish sanitation system to those in other countries.
185 citations
TL;DR: The long-term survival of pathogenic microorganisms was evaluated and modeled in simulated fermented and dried, uncooked sausages, such as salami and pepperoni, and showed several forms of declining curves, including classic first-order declines, shoulder or lag phases, and two-phase declines with shoulder.
Abstract: The long-term survival of pathogenic microorganisms was evaluated and modeled in simulated fermented and dried, uncooked sausages, such as salami and pepperoni.Listeria monocytogenes andSalmonella were inoculated in BHI broths with added lactic acid or lactate (0–1.5%), NaCl (0–19%) and NaNO2 (0–200 ppm) and then incubated at 4–42°C for up to 9 months. Enumerations of surviving cells showed several forms of declining curves, including classic first-order declines, shoulder or lag phases, and two-phase declines with shoulder. Two primary models were tested for their ability to depict the data. The effect of the environmental conditions on the parameters of the models were described with multiple regression equations (secondary models).
117 citations
TL;DR: A medium was devised for the rapid presumptive identification of Aeromonas hydrophila and offered good differentiation of Klebsiella, Proteus, and other enteric species.
Abstract: A medium was devised for the rapid presumptive identification of Aeromonas hydrophila. It also offered good differentiation of Klebsiella, Proteus, and other enteric species. Mannitol fermentation, inositol fermentation, ornithine decarboxylation and deamination, indole production, motility, and H2S production from sodium thiosulfate and cysteine could be recorded in a single tube of the medium.
101 citations
01 Sep 2000-Food Additives and Contaminants Part A-chemistry Analysis Control Exposure & Risk Assessment
TL;DR: Low temperature pasteurization was effective in reducing Vibrio spp.
Abstract: Vibrio vulnificus and V. parahaemolyticus are natural inhabitants of estuarine environments and may be transmitted to humans by ingestion of raw oysters. This study focused on the use of low temperature pasteurization, to reduce these Vibrio spp. to nondetectable levels, thus reducing the risk of infection associated with raw oyster consumption. Artificially-inoculated V. vulnificus and V. parahaemolyticus and naturally-contaminated V. vulnificus in live oysters were pasteurized at 50 degrees C for up to 15 min. Samples of processed and unprocessed oysters were enumerated for V. vulnificus, V. parahaemolyticus, and aerobic spoilage bacteria for 0-14 days. Low temperature pasteurization was effective in reducing these pathogens from > 100,000 to non-detectable levels in less than 10 min of processing. Spoilage bacteria were reduced by 2-3 logs, thus increasing the shelf-life for up to 7 days beyond live unprocessed oysters. Vibrio vulnificus in control oysters was reduced by 10(2) during ice storage alone. Following pasteurization and during a temperature storage abuse study (24 h at 22 degrees C), V. vulnificus was not recovered. During this storage period spoilage bacteria exceeded 1 million/g oyster meat.
89 citations
TL;DR: This study aims to evaluate the effect of postharvest temperature on bacterial communities in live Pacific oysters using nonculture‐based methods and shows no clear relationship between temperature and bacterial communities.
Abstract: Aims: To evaluate the effect of postharvest temperature on bacterial communities in live Pacific oysters (Crassostrea gigas) using nonculture-based methods.
Methods and Results: Live oysters were compared before and after storage at 4, 6, 15, 20 and 30°C using terminal restriction fragment length polymorphism (T-RFLP). Bacterial communities in freshly harvested (control) vs stored oysters were significantly different. Changes in bacterial communities at 4, 15 and 30°C observed by T-RFLP were further investigated by clone library analysis. Members of the Proteobacteria predominated (43·0–57·0% of clones) in control oysters, while storage altered the bacterial profile. At 4°C, Psychrilyobacter spp. (phylum Fusobacteria) predominated (43·8% of clones), while at 15 and 30°C, members of the phylum Bacteroidetes represented 63·0 and 60·2% of clones, respectively. High microbial diversity in oysters was observed, with at least 73 different genera-related clones among all samples.
Conclusions: Changes in the overall bacterial community of Pacific oysters were influenced by storage temperature and would likely not be detected by standard culture-based methods currently used to assess oyster quality. Certain dominant genera, such as Psychrilyobacter, Polynucleobacter and a bacterial group related to Alkaliflexus, should be further studied as possible indicators for postharvest temperature control.
Significance and Impact of the Study: This work is the first report describing the effect of different storage temperatures on bacterial diversity in postharvest live Pacific oysters using molecular-based methods.
73 citations