Isotachophoretic quantification of total viable bacteria on meat and surfaces

BACKGROUND

The quantification of microbes, particularly live bacteria, is of utmost importance in assessing the quality of meat products. In the context of meat processing facilities, prompt identification and removal of contaminated carcasses or surfaces is crucial to ensuring the continuous production of safe meat for human consumption. The plate count method and other traditional detection methods are not only labour-intensive but also time-consuming taking 24-48 h.

RESULTS

In this report, we present a novel isotachophoretic quantification method utilizing two nucleic acid stains, SYTO9 and propionic iodide, for the detection of total viable bacteria. The study employed E. coli M23 bacteria as a model organism, with an analysis time of only 30 min. The method demonstrated a limit of detection (LOD) of 184 CFU mL-1 and 14 cells mL-1 for total viable count and total cell count, respectively. Furthermore, this new approach is capable of detecting the microbial quality standard limits for food contacting surfaces (10 CFU cm-2) and meat (1.99 × 104 CFU cm-2) by swabbing an area of 10 × 10 cm2.

SIGNIFICANCE

In contrast to the culture-based methods usually employed in food processing facilities, this isotachophoretic technique enables easy and rapid detection (<30 min) of microorganisms, facilitating crucial decision-making essential for maintaining product quality and safety.

UV-fluorescence imaging for real-time non-destructive monitoring of pork freshness

This study aimed to develop a cost-effective fluorescence imaging system to rapidly monitor pork freshness indicators during chilled storage. The system acquired fluorescence images of pork and the color features were extracted from these images to establish partial least squares regression (PLSR) models to predict total volatile basic nitrogen (TVB-N), total viable count (TVC), pH for pork. For TVB-N, TVC and pH values, R_p were 0.92, 0.88 and 0.74, residual predictive deviation (RPD) were 2.24, 2.03, and 1.19, respectively. For TVB-N and TVC indicators showed that the predictive ability of this model was largely comparable to that of fluorescence hyperspectral imaging. However, combining fluorescence and color imaging improved the model's predictive ability. For TVB-N, TVC and pH, R_p were 0.94, 0.93 and 0.85, RPD were 2.62, 2.59, and 1.95, respectively. Therefore, this study developed a system with great potential for detecting the value of most pork quality indicators in real-time.

Synthetic dye's substitution with chokeberry extract in jelly candies

Matching the general trend of replacing synthetic additives with healthier natural products, the present research studies the effects of different concentrations of chokeberry extract which substitute carmoisine dye in jelly candies. Also, the colour and antioxidant properties of the aforementioned extract and their changes at various pH and in presence of different mineral salts from foods are analysed. The phenolic content of the extract was determined using HPLC and spectrophotometric methods. A high concentration of polyphenols was found in the chokeberry extract, of which around 97% were flavonoids. Catechin, epicatechin, ferulic acid and its methyl esther, protocatechuic, gallic and para-hydroxybenzoic acids were the major phenolics identified in the extract. The total antioxidant activity decreased in acidic media, while close-to-neutral and alkaline pH values did not exhibit any effect on this parameter. Furthermore, the green/red colour parameter, the chroma and the hue angle were enhanced in the most acidic media (pH 2.3 and 3.5). From the studied salts, CaCl₂ and KNO₃ had the most significant effects on colour. The chokeberry extract proved to be suitable as replacement of carmoisine dye in jelly candies, as the physicochemical and microbiological properties comply with the regulated requirements. More than that, the extract improved the antioxidant and sensory properties of jellies in all studied concentrations and the best total sensory score was obtained for 1.5% extract. After 5 and 50 days of storage, the microbiological properties were improved in candies prepared with aronia extracts compared to carmoisine, as the total viable count registered important diminutions.

Growth potential of Listeria monocytogenes in twelve different types of RTE salads: Impact of food matrix, storage temperature and storage time

Listeriosis is a food borne disease associated with high hospitalization and fatality rates; in 2014, EU member states reported 2194 cases with 98.9% hospitalization rates and 210 fatalities. Proper risk analysis and the development of effective food safety strategies critically depend on the knowledge of the growth characteristics of L. monocytogenes on the product in question. Ready-to-eat (RTE) salads present a challenge in this context due to the absence of a heat treatment step before consumption. This study provides challenge-test based data of the growth characteristics of L. monocytogenes on twelve RTE salads. The food matrix, storage time and storage temperature were factors with a significant impact on the growth of L. monocytogenes. While most tested salads permitted a significant increase of L. monocytogenes in at least one of the tested conditions, no growth was observed on celeriac, carrot and corn salad products. There was a considerable increase in growth at 8 °C compared to 5 °C. Our data indicate that the reduction of the storage temperature at retail level to 5 °C and product shelf life could help mitigate the risk of L. monocytogenes in RTE salads.

Growth potential of Listeria monocytogenes in six different RTE fruit products: impact of food matrix, storage temperature and shelf life

We tested the growth potential of Listeria monocytogenes on six RTE fruit products at low (4°C at the factory followed by 8°C retail/home storage) and abusive (4°C followed by 12°C) storage temperatures. Sliced coconut and fresh cut cantaloupe, as well as a fruit mix containing diced pineapple, cantaloupe, apples and grapes supported the growth of L. monocytogenes with a growth potential δ>0.5 log CFU/g over six days. Mangoes, a mix of diced kiwi, cantaloupe and pineapple as well as a mix of diced pineapple, mango, grapefruit, kiwi and pomegranate did not support a growth potential that exceeded 0.5 log CFU/g over six days. The growth potential of L. monocytogenes correlated significantly with the pH; no product with a pH below 4 showed a significant growth potential of L. monocytogenes. Time after inoculation was also a significant predictor of the growth potential, while the fruit type and storage temperature were not.

Food-borne bacterial pathogens in marketed raw meat of Dharan, eastern Nepal

Objectives

This study aims to assess the bacteriological quality of marketed raw meat with a special emphasis on isolation of Escherichia coli, Salmonella spp., Shigella spp., Vibrio spp., Pseudomonas aeruginosa and Staphylococcus aureus in raw meat marketed in Dharan. Altogether 50 meat samples were collected from local markets of Dharan and transported to the microbiology laboratory at 4 °C. The meat samples were homogenized in a sterile glass homogenizer and the possible pathogens were isolated and identified by conventional microbiological techniques.

Results

The mean total viable count values were found having a mean count of 8.22 ± 0.14, 8.29 ± 0.17, 7.87 ± 0.18 and 7.92 ± 0.19 in terms of log₁₀ CFU/g ± Standard Error for chicken, pork, buffalo, and goat meat respectively. Coliforms were found in 84% samples, S. aureus was found in 68% samples, Salmonella spp. in 34% samples, Shigella spp. in 6% samples, Vibrio spp. in only 3 samples and P. aeruginosa was isolated from 40% sample. Higher microbial load and presence of intestinal commensals E. coli, Salmonella spp., Shigella spp., Vibrio spp indicates that meat might be contaminated by the visceral content and consumers are at risk of getting a foodborne disease when eaten raw.

Microbiological contamination in Three Large-Scale Pig Slaughterhouses in Northern Italy

The aim of this survey was to obtain data on microbiological contamination of pig carcasses and environments in three large-scale Italian slaughterhouses (identified as A-B-C) located in Northern Italy. Each slaughterhouse was visited six times. Five carcasses and three different sites of the slaughterhouse (before and during slaughter) were sampled on each sampling day. A single pooled caecal sample was taken on each sampling day. A total of 90 carcasses, 108 environmental samples and 18 caecal samples were collected. Samples from pig carcasses and slaughterhouse environment were analyzed for total viable count (TVC), Enterobacteriaceae count (EBC) and Salmonella. The caecal contents were examined for Salmonella. Carcasses from slaughterhouse A presented the greatest TVC and EBC mean log value, whereas environmental samples collected during slaughter activities from slaughterhouse C showed the greatest TVC and EBC mean log value. As far as the environmental samples collected before slaughter activities are concerned, an average up to 6 log10 colony forming unit (CFU)/cm2 TVC in two slaughter plants (A and C) and 5 log10 CFU/cm2 TVC in one slaughter plant (B) was detected. Salmonella was recovered in two slaughterhouses (A and B). Four different Salmonella serotypes were detected in the positive samples (11). Within serotype S. Rissen and S. Typhimurium monophasic-variant isolates, two pulsed-field gel electrophoresis patterns were identified. The findings in this survey suggest that carcass contamination is influenced by the slaughterhouse plant and this could be a result of differences in line speed. The results of environmental sampling have not shown an association with the slaughterhouse plant.