scholarly journals Listeria monocytogenes Assessment in a Ready-to-Eat Salad Shelf-Life Study Using Conventional Culture-Based Methods, Genetic Profiling, and Propidium Monoazide Quantitative PCR

Foods ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 235
Author(s):  
Rita Bernardo ◽  
Ana Duarte ◽  
Luís Tavares ◽  
António Salvador Barreto ◽  
Ana Rita Henriques
Keyword(s):  
Listeria Monocytogenes ◽  
Shelf Life ◽  
Pulsed Field Gel Electrophoresis ◽  
Life Assessment ◽  
Propidium Monoazide ◽  
Contamination Source ◽  
Genetic Profiling ◽  
Life Study ◽  
Conventional Culture ◽  
Shelf Life Studies

Listeriosis is almost entirely transmitted through foods contaminated with Listeria monocytogenes. Ready-to-eat foods present a particular challenge due to their long refrigerated shelf-life, not requiring any heat treatment before consumption. In this work, a shelf-life assessment of an industrially produced ready-to-eat salad was performed using conventional culture-based and molecular methods. L. monocytogenes isolates were confirmed and serogrouped using multiplex PCR, and genetic subtyping was performed by pulsed-field gel electrophoresis (PFGE). PMAxx-qPCR was used as an alternative method for L. monocytogenes quantification in foods. Salad samples were kept at 4 °C, 12 °C, and 16 °C for eight days and analysed. At 4 °C, acceptable results were obtained considering hygiene indicators, i.e., Enterobacteriaceae (ranging from 3.55 ± 0.15 log cfu/g to 5.39 ± 0.21 log cfu/g) and aerobic mesophilic colony counts (5.91 ± 0.90 log cfu/g to 9.41 ± 0.58 log cfu/g) throughout the study, but the same did not happen at 12 °C and 16 °C. L. monocytogenes culture-based quantification exhibited low numbers (<1 log cfu/g) for all temperatures. From 30 presumptive isolates, 10 (33.3%) were confirmed as L. monocytogenes with the majority belonging to serogroup IVb. PFGE subtyping showed that 7 of the 10 L. monocytogenes isolates had 100% of pulsotype similarity, suggesting a possible common contamination source. PMAxx-qPCR revealed a statistically higher L. monocytogenes quantification (>3 log cfu/g) when compared to the conventional culture-based method, suggesting viable but non-culturable forms. Taken together, results underline the need to combine conventional methods with more sensitive, specific, and rapid ones for L. monocytogenes assessment in ready-to-eat foods shelf-life studies to reduce the potential risk for consumers.

scholarly journals Development of Ambient Stable Retort Pouch Processed Ramasseri Idli

2019 ◽  
Vol 8 (4) ◽  
pp. 1503-1507
Keyword(s):  
Shelf Life ◽  
Thermal Processing ◽  
Quality Evaluation ◽  
Standard Procedure ◽  
Life Study ◽  
Ambient Storage ◽  
Physico Chemical ◽  
Microbial Analysis ◽  
Retort Pouch ◽  
Shelf Life Studies

Development retort pouch packaged Ramasseri idli was undertaken with specific objectives of standardisation of thermal process in retort pouch package, shelf life study and quality evaluation. The Ramasseri idli, an indigenous cereallegume based food of south India, was procured and packaged in retort pouches with one idli in each pouch. The idlis were pasteurized at different time temperature combinations to achieve desired F0 values (110°C for F0=3 min, 110°C for F0=6 min 100°C for F0=3 min, 110°C for F0=6 min). After thermal processing the pouches were stored for shelf life studies under ambient storage (28°C) and refrigerated storage (7°C). The processed product was analysed for microbial and physico-chemical qualities viz; moisture content, pH, water activity, colour and texture using standard procedure at regular intervals. Based on physico-chemical characteristics and sensory evaluation, the thermal processed Ramasseri idli at 100°C for F0=6 min and stored under refrigeration showed best results up to three week of storage among the four treatments. The microbial analysis also showed that the product was safe up to 3 weeks of storage.

scholarly journals Development of a scientific study for accessing the criteria under Commission Regulation (EC) 2073/2005 on traditional Slovak sheep cheese "bryndza"

2011 ◽  
Vol 29 (No. 1) ◽  
pp. 31-34
Author(s):  
L. Cabanová ◽  
O. Škuntová ◽  
D. Matisová ◽  
M. Pipová
Keyword(s):  
Listeria Monocytogenes ◽  
Shelf Life ◽  
Laboratory Tests ◽  
Growth Potential ◽  
Life Study ◽  
Physico Chemical ◽  
Commission Regulation ◽  
The Difference ◽  
Microbiological Analyses ◽  
Positive Results

A scientific shelf-life study for Listeria monocytogenes in the typical Slovak cheese "bryndza" was performed in accordance with the requirements of the Commission Regulation (EC) 2073/2005. Based on the previous positive findings of L. monocytogenes in the final products, the producer decided to perform laboratory tests, the results of which would allow him a different evaluation of these positive results. Both the physico-chemical (pH, a<sub>w)</sub> and microbiological examinations of "bryndza" cheese stored at 5.8&ndash;6.2&deg;C were performed every two days till the end of the product shelf-life (7 days). Microbiological analyses were performed after artificial contamination of the final product with a mixture of three L. monocytogenes strains. The growth potential of L. monocytogenes was calculated as the difference in the counts of this bacterium between the last day and the first day of the test. The Slovak traditional "bryndza" cheese has been found not to support the growth of L. monocytogenes. Thus, the counts of L. monocytogenes must not exceed 50 CFU/g at the beginning and 20 CFU/g at the end of the product shelf-life in order to ensure its safety for the consumer.

scholarly journals Studies on the Preparation and Shelf-Life of Soursop, Tamarind, and Blended Soursop-Tamarind Soft Drinks

1969 ◽  
Vol 58 (1) ◽  
pp. 99-104
Author(s):  
J. R. Benero ◽  
A. L. Collazo de Rivera ◽  
L. M. I. De George
Keyword(s):  
Shelf Life ◽  
Sensory Evaluation ◽  
Soft Drinks ◽  
Soluble Solids ◽  
Fruit Pulp ◽  
Life Study ◽  
Solids Concentration ◽  
Shelf Life Studies ◽  
Short Time ◽  
Soluble Solids Concentration

Soursop, tamarind, and blended tamarind-soursop soft drinks were prepared by dispersing the desired amount of fruit pulp in water and adjusting the soluble-solids concentration to the corresponding Brix level. The drinks then were pasteurized in a short-time pasteurizer at 185° F, canned in 7 1/2-ounce plain tin containers, cooled under water, air-dried, and finally stored at 85° F. For soursop drinks, levels of 10- to 15-percent fruit-pulp content were dried at a 15° Brix soluble-solids concentration; and for tamarind, levels of 9- to 12-percent pulp with the soluble solids adjusted at 21.5° Brix. In the case of blended drinks, the fruit pulp contents were varied from 10- to 14-percent by increasing the ratio of tamarind pulp to soursop. Two soluble-solids concentrations were studied: 15° and 17° Brix. The sensory evaluation of the drinks at different pulp concentrations, which were performed during the shelf-life studies, revealed no significant differences among the samples tested, although a tendency to prefer the sweeter one (17° Brix) was observed in the case of the blended drink. Soursop drinks with 12- to 15-percent pulp content remained acceptable for over 1 year and tamarind drinks throughout the whole year of the shelf-life study. Blended drinks were found acceptable for over 10 months.

Molecular Typing To Trace Listeria monocytogenes Isolated from Cold-Smoked Fish to a Contamination Source in a Processing Plant

2006 ◽  
Vol 69 (4) ◽  
pp. 835-841 ◽  
Author(s):  
HIROMI NAKAMURA ◽  
YUKA TOKUDA ◽  
AYUMI SONO ◽  
TOMOKA KOYAMA ◽  
JUN OGASAWARA ◽  
...  
Keyword(s):  
Listeria Monocytogenes ◽  
Molecular Typing ◽  
Pulsed Field Gel Electrophoresis ◽  
Processing Plant ◽  
Fish Processing ◽  
Contamination Source ◽  
Processing Equipment ◽  
Smoked Fish ◽  
Different Types ◽  
Raw Fish

In this study, Listeria monocytogenes contamination in a cold-smoked fish processing plant in Osaka, Japan, was examined from 2002 to 2004. A total of 430 samples were collected and divided into five categories: raw fish, materials during processing, processing equipment, environment, and finished products. A total of 59 finished products were examined throughout this study. L. monocytogenes was isolated from four of these samples during summer and autumn but was not found during winter or spring. During the warmer seasons, L. monocytogenes was more prevalent on processing equipment, especially slicing machines (8 of 54 samples in summer and autumn versus 1 of 50 samples in winter and spring). L. monocytogenes was not detected on whole skins removed from 23 frozen raw fish. L. monocytogenes strains isolated from 56 samples were characterized by serotyping, pulsed-field gel electrophoresis, and three PCR-based methods. Seventy-seven L. monocytogenes strains were recognized as contaminants of the samples: 2 distinguishable strains were identified in each of 13 samples, 3 strains were identified in 2 samples, 5 strains were identified in 1 sample, and the other 40 strains were identified in 40 samples. Combining the results from these techniques, 77 strains were classified into 13 different types. Three of these types prevailed throughout the plant, and two of the three were also isolated from final products. The DNA subtype found in the product was also found on the slicing machines. Our findings suggest that the slicing machines at this plant were the source of the product contamination. Implementing an appropriate cleaning regime for the slicing machines was effective in preventing contamination.

scholarly journals A shelf-life study of silica- and carbon-based mesoporous materials

2021 ◽  
Author(s):  
Emma M. Björk ◽  
Aylin Atakan ◽  
Pei-Hsuan Wu ◽  
Alessandra Bari ◽  
Carlotta Pontremoli ◽  
...  
Keyword(s):  
Shelf Life ◽  
Mesoporous Materials ◽  
Life Study ◽  
Carbon Based

Packaging of beef fillet with active chitosan film incorporated with ɛ-polylysine: An assessment of quality indices and shelf life assessment

Meat Science ◽  
2021 ◽  
pp. 108475
Author(s):  
Kazem Alirezalu ◽  
Samira Pirouzi ◽  
Milad Yaghoubi ◽  
Maryam Karimi-Dehkordi ◽  
Shima Jafarzadeh ◽  
...  
Keyword(s):  
Shelf Life ◽  
Chitosan Film ◽  
Life Assessment ◽  
Quality Indices

scholarly journals Assessment of chicken breast shelf life based on bench-top and portable NIR spectroscopy tools coupled with chemometrics

2020 ◽  
Author(s):  
Ilaria Lanza ◽  
Daniele Conficoni ◽  
Stefania Balzan ◽  
Marco Cullere ◽  
Luca Fasolato ◽  
...  
Keyword(s):  
Discriminant Analysis ◽  
Shelf Life ◽  
Meat Quality ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Life Assessment ◽  
Chicken Breast ◽  
Portable Devices ◽  
Physicochemical Processes ◽  
Insight Into

Abstract Near-infrared (NIR) spectroscopy is a rapid technique able to assess meat quality even if its capability to determine the shelf life of chicken fresh cuts is still debated, especially for portable devices. The aim of the study was to compare bench-top and portable NIR instruments in discriminating between four chicken breast refrigeration times (RT), coupled with multivariate classifier models. Ninety-six samples were analysed by both NIR tools at 2, 6, 10 and 14 days post-mortem. NIR data were subsequently submitted to partial least squares discriminant analysis (PLS-DA) and canonical discriminant analysis (CDA). The latter was preceded by double feature selection based on Boruta and Stepwise procedures. PLS-DA sorted moderate separation of RT theses, while shelf life assessment was more accurate on application of Stepwise-CDA. Bench-top tool had better performance than portable one, probably because it captured more informative spectral data as shown by the variable importance in projection (VIP) and restricted pool of Stepwise-CDA predictive scores (SPS). NIR tools coupled with a multivariate model provide deep insight into the physicochemical processes occurring during storage. Spectroscopy showed reliable effectiveness to recognise a 7-day shelf life threshold of breasts, suitable for routine at-line application for screening of meat quality.

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