Crab-meat-isolated psychrophilic spore forming bacteria inactivation by electron beam ionizing radiation.

The present work was performed to evaluate the potential of electron beam ionizing radiation for the inactivation of three psychrophilic spore forming bacteria (Bacillus mycoides, Bacillus weihenstephanensis and Psychrobacillus psychrodurans) isolated from ready-to-eat brown crab (Cancer pagurus). Inactivation curves for the three spores were performed in both types of crab meat, brown and white. Also the effect of pH and water activity (aw) on the lethal efficacy of ionizing radiation, for the three different psychrophilic spore forming bacteria, was evaluated. The effects of pH, aw and their possible interactions were assessed in citrate-phosphate buffers of different pH, ranging between 7 and 4, and aw, ranging from <0.99 to 0.80. A reduction of aw increased the spores resistance between >0.99 and 0.90, while an aw reduction from 0.90 to 0.80 had a minor impact on their resistance. In contrast to aw, the effect of pH showed a greater variability depending on the spore species. While pH did not affect the resistance of B. weihenstephanensis at any aw, B. mycoides showed slightly higher resistance at pH 5.5 at aw of 0.90 and 0.80. pH showed a significant effect on the resistance of P. psychrodurans. For the two types of crab meat, slightly differences were observed in 6D values. B. weihenstephanensis was the most resistant, requiring 7.3-7.6 kGy to inactivate 6 Log10-cycles of this spore forming bacterium, while for B. mycoides and P. psychrodurans 6.1-6.3 and 5.4-5.3 kGy respectively were necessary to reach the same inactivation level in crab meat. An agreement between spore resistance in crab meats and lab media, with similar characteristics in pH and aw, was also observed. The results obtained in this research demonstrated the potential for ionizing radiation to achieve an appropriate inactivation level of spores naturally present in brown crab with the application of doses lower than 10 kGy.

Evaluation of the potential of ultrasound technology combined with mild temperatures to reduce cadmium content of edible crab (Cancer pagurus).

The consumption of crustaceans is correlated with certain health risks, particularly due to several highly toxic elements they contain, including cadmium (Cd). Although Cd content in one sole crab generally exceeds the total weekly recommended intake of cadmium as established by EFSA (especially in brown meat), efficient modern strategies to reduce Cd content in crabs still have not yet been developed. The objective of this research was therefore to evaluate the potential use of ultrasound technology in combination with temperature (50°-80 °C) with the purpose of releasing Cd from brown crab (Cancer pagurus), thereby reducing the Cd content in its meat. Female crabs were immersed in a water bath at 50, 65, and 80 °C in presence or absence of ultrasound; Cd concentration in the water was monitored along time. At the end of the process, Cd content in brown and white crab meat was likewise quantified. Treatment temperature did not bear an influence on the release of Cd in absence of ultrasound, but proved to be an important variable when ultrasound assisted the process. Ultrasound increased Cd release rates 8.7-, 2.1- and 2.7-fold in conjunction with the treatments at 50, 65 and 80 °C, respectively. The maximum percentage of Cd extracted (22.8%) was observed at 50 °C for an ultrasound input power of 200 W. These results have demonstrated for the first time that the application of ultrasound during the crab-cooking process could serve as an effective physical procedure for reducing the Cd content of crabs, thereby improving the product's safety for consumers.

An assessment of the application of ultrasound in the processing of ready-to-eat whole brown crab (Cancer pagurus).

This study assesses the potential of incorporating ultrasound as a processing aid in the production of whole cooked brown crab (Cancer pagurus). The FDA recommended heat treatment to reduce Listeria monocytogenes by 6 log10 cycles in this product is a F707.5 of 2min. An equivalent F value was applied at 75°C in presence and absence of ultrasound in water alone or in water with 5% w/v NaCl added. Heat penetration, turbidity and conductivity of the cook water and also salt and moisture content of the crab meat (white and brown) were determined. Ultrasound assisted cooking allowed a reduction of the cooking time by up to 15% while still maintaining an F707.5 of 2min. Ultrasound also enhanced the rate and total amount of compounds released from the crab, which suggests that crabs cooked in the presence of ultrasound would be expected to be cleaner. Ultrasound also proved to be effective in reducing the salt content but hardly affected the final moisture content of the crab meat.

Application of ultrasound in combination with heat and pressure for the inactivation of spore forming bacteria isolated from edible crab (Cancer pagurus).

This research was performed to characterize the resistance of three different bacterial spore species isolated from pasteurized edible crab (Cancer pagurus) meat to heat treatments and to assess the potential of manosonication (MS) and manothermosonication (MTS) as an alternative for their inactivation. The spore-forming bacteria used in this study were Bacillus mycoides, Bacillus weihenstephanensis and Psychrobacillus psychrodurans. The thermal resistance of these three species was determined at different temperatures ranging from 80 to 110 °C and their resistance to ultrasound under pressure from 35 to 95 °C. Ginafit Excel tool was used to fit the Geeraerd's 'Log-linear + shoulder' and Bigelow & Easty's equations to the survival curves for heat and MS/MTS treatments. From the results obtained it can be concluded that the profile of the survival curves either for heat or for ultrasound treatments depended on the bacterial spore species. When shoulders were detected in the inactivation curves for heat they were also present in the curves for MS/MTS treatments, although the application of an ultrasonic field reduced the shoulder length. B. weihenstephanensis was found to be the most resistant species to heat, requiring 1.4 min to reduce 4log10 cycles at 107.5 °C (zT=7.1 °C) while B. mycoides was the most sensitive requiring 1.6 min at 95 °C (zT=9.1 °C). By contrast, B. mycoides was the most resistant to MS. The efficiency of the combination of ultrasonic waves under pressure with heat (MTS) for bacterial spore inactivation was directly correlated with the thermal resistance. Indeed, MTS showed a synergistic effect for the inactivation of the three spores. The highest percentage of synergism corresponded to the spore species with higher zT value (B. mycoides), but the highest temperature at which this synergism was detected corresponded to the most heat tolerant spore species (B. weihenstephanensis). This study revealed that MTS treatment is capable of inactivating spore-forming bacteria and that the inactivation efficiency of the combined treatment is correlated with the thermal resistance of the spore species.

Combined effect of selected non-thermal technologies on Escherichia coli and Pichia fermentans inactivation in an apple and cranberry juice blend and on product shelf life.

The combination of novel, non-thermal technologies for preservation purposes is a recent trend in food processing research. In the present study, non-thermal hurdles such as ultraviolet light (UV) (5.3 J/cm²), high intensity light pulses (HILP) (3.3 J/cm²), pulsed electric fields (PEF) (34 kV/cm, 18 Hz, 93 µs) or manothermosonication (MTS) (4bar, 43 °C, 750 W, 20 kHz) were examined. The objective was to establish the potential of these technologies, applied individually or in paired sequences, to inactivate Escherichia coli and Pichia fermentans inoculated in a fresh blend of apple and cranberry juice. The shelf-life evaluation of selected non-thermally treated samples was conducted over 35 days and compared to pasteurised samples and untreated juices. All treatments applied individually significantly reduced (1.8-6.0 log cfu/ml) microbial counts compared to the untreated sample (p<0.01). Furthermore, UV treatment produced significantly greater inactivation (p<0.05) for E. coli compared to P. fermentans. Combinations of non-thermal hurdles consisting of UV or HILP followed by either PEF or MTS resulted in comparable reductions for both microorganisms (p ≥ 0.05) to those observed in thermally pasteurised samples (approx. 6 log cfu/ml). Thermally pasteurised samples had a shelf life exceeding 35 days, while that of UV+PEF and HILP+PEF-treated samples was 14 and 21 days, respectively. These results indicate that combinations of these non-thermal technologies could successfully reduce levels of E. coli and P. fermentans in apple and cranberry juice, although optimisation is required in order to further extend shelf life.

Efficacy of UV light treatment for the microbiological decontamination of chicken, associated packaging, and contact surfaces.

UV light was investigated for the decontamination of raw chicken, associated packaging, and contact surfaces. The UV susceptibilities of a number of Campylobacter isolates (seven Campylobacter jejuni isolates and three Campylobacter coli isolates), Escherichia coli ATCC 25922, and Salmonella enterica serovar Enteritidis ATCC 10376 in liquid media were also investigated. From an initial level of 7 log CFU/ml, no viable Campylobacter cells were detected following exposure to the most intense UV dose (0.192 J/cm(2)) in liquid media (skim milk subjected to ultrahigh-temperature treatment and diluted 1:4 with maximum recovery diluent). Maximum reductions of 4.8 and 6.2 log CFU/ml were achieved for E. coli and serovar Enteritidis, respectively, in liquid media. Considerable differences in susceptibilities were found between the Campylobacter isolates examined, with variations of up to 4 log CFU/ml being observed. UV treatment of raw chicken fillet (0.192 J/cm(2)) reduced C. jejuni, E. coli, serovar Enteritidis, total viable counts, and Enterobacteriaceae by 0.76, 0.98, 1.34, 1.76, and 1.29 log CFU/g, respectively. Following UV treatment of packaging and surface materials, reductions of up to 3.97, 4.50, and 4.20 log CFU/cm(2) were obtained for C. jejuni, E. coli, and serovar Enteritidis, respectively (P < 0.05). Overall, the color of UV-treated chicken was not significantly affected (P ≥ 0.05). The findings of this study indicate that Campylobacter is susceptible to UV technology and that differences in sensitivities exist between investigated isolates. Overall, UV could be used for improving the microbiological quality of raw chicken and for decontaminating associated packaging and surface materials.

Effectiveness of High Intensity Light Pulses (HILP) treatments for the control of Escherichia coli and Listeria innocua in apple juice, orange juice and milk.

High Intensity Light Pulses (HILP) represent an emerging processing technology which uses short (100-400 µs) light pulses (200-1100 nm) for product decontamination. In this study, model and real foods of differing transparencies (maximum recovery diluent (MRD), apple and orange juices and milk) were exposed to HILP in a batch system for 0, 2, 4 or 8 s at a frequency of 3 Hz. After treatment, inactivation of Escherichia coli or Listeria innocua was evaluated in pre-inoculated samples. Sensory and other quality attributes (colour, pH, Brix, titratable acidity, non-enzymatic browning, total phenols and antioxidant capacity (TEAC)) were assessed in apple juice. Microbial kill decreased with decreasing transparency of the medium. In apple juice (the most transparent beverage) E. coli decreased by 2.65 and 4.5 after exposure times of 2 or 4 s, respectively. No cell recovery was observed after 48 h storage at 4°C. No significant differences were observed in quality parameters, excepting TEAC and flavour score, where 8 s exposure caused a significant decrease (p<0.05). Based on these results, HILP with short exposure times could represent a potential alternative to thermal processing to eliminate undesirable microorganisms, while maintaining product quality, in transparent fruit juices.

A comparison of conventional and radio frequency defrosting of lean beef meats: Effects on water binding characteristics.

The effect of defrosting rate (slow conventional air vs. fast radio frequency (RF) method) on water holding properties of lean beef meat (whole, minced and comminuted) was investigated using a conventional centrifugation method (drip loss), nuclear magnetic resonance relaxometry (NMR) and dielectric spectroscopy. Tempering by radio frequency (RF) or a conventional air method had no subsequent effect (P⩾0.05) on drip loss. However, thawing by RF resulted in a significant decrease in drip loss (P<0.05) when compared to air thawing. Micronutrient loss (µg/mL of drip) was also greater in air thawed samples (P<0.05). NMR T(2) distributions did not show any marked difference between thawing methods. The dielectric properties of lean beef, measured from 0.01-20GHz at 5°C, were higher following RF thawing. Increased comminution reduced dielectric values, while fine comminution gave an additional fraction in the NMR T(2) distribution. These results provide valuable information on water binding in meat following RF tempering/thawing.

A comparison of conventional and radio frequency tempering of beef meats: Effects on product temperature distribution.

This study aimed to develop radio frequency (RF) pilot-scale protocols for tempering beef meat blends (4kg blocks) to achieve average temperatures between -2 and -5°C. Post-tempering temperature distribution in these blocks was compared to products tempered by conventional methods. The optimum RF power-time combination for tempering lean and 50:50 lean:fat mixtures to the target range was 500W for 11min which produced respective means of -3.6°C (s.d. 1.1) and -3.4°C (s.d. 1.5). In contrast, 400W for 11min was optimum for fat (mean -4.9°C, s.d. 2.1). This study shows the principal advantages of RF over conventional tempering as an approximate 30 fold tempering time reduction and a greater uniformity of end point temperature distribution under the conditions employed. Furthermore, power consumption was reduced approximately ninefold with RF compared to conventional tempering. More uniform temperature distribution was achieved in samples that were comminuted to a greater extent.