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 F70 7.5 of 2 min. 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 F70 7.5 of 2 min. 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

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 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

Effect of the synergy of electric pulses and oregano essential oil in the inactivation of L. monocytogenes

[SPA] Listeria monocytogenes es actualmente una de las principales preocupaciones de la industria alimentaria. Aunque el número de casos reportados en la Unión Europea es relativamente, tiene una gran gravedad, con unas tasas de hospitalización y mortandad del 97% y del 16,7%, respectivamente. Debido a la ubicuidad de este microorganismo y su capacidad de crecer en numerosas matrices alimentarias, las empresas agroalimentarias deben aplicar tratamientos que inactiven las células de L. monocytogenes. En este trabajo, se estudió la cinética de inactivación de L. monocytogenes aislada de productos marinos sometida a un tratamiento combinado de PEAV con un aceite esencial de orégano. Los resultados demuestran esta sinergia, ya que se consiguió una mayor inactivación microbiana con un campo de 20 kV/cm, 1 Hz de frecuencia, 150 pulsos y una concentración de orégano de 1/2 MIC, superior a la obtenida en las muestras control. Llegando a la conclusión de que los PEAV impulsan el efecto del orégano sobre la membrana de la bacteria. [ENG] Nowadays Listeria monocytogenes is one of the main concerns of the food industry. The number of cases reported in the European Union is relatively low it is very serious, with rates of hospitalization and mortality of 97% and 16.7%, respectively. Due to the ubiquity of this organism and its capacity to grow in many food matrices, agri-food companies must apply treatments that inactivate the cells of L. monocytogenes. In this work, it was studied the kinetics of inactivation of L. monocytogenes isolated from marine products subjected to a combined treatment of PEF with an essential oil of oregano. The results show this synergy, since it got a greater inactivation microbial with a field of 20 KV/cm, 1 Hz frequency, 150 pulses and an oregano concentration of 1/2 MIC, higher than that obtained in control samples. Concluding that the PEF promote the effect of oregano on the bacterial cell membrane.Investigación apoyada por el MICINN (es) y FEDER a través de los proyectos AGL2017-86840-C2-1-R y AGL2016-82014-REDT

The influence of compositional changes in reconstituted potato flakes on thermal and dielectric properties and temperatures following microwave heating

The objective of this study was to evaluate the effect of formulation changes on the temperatures of the reconstituted potato flakes following a standardised microwave reheating using a response surface method. Reconstituted potato flakes with elevated levels of fat (0.6–11.1%), water (69–78.7%) and salt (0–5.7%) were prepared. Thermal properties (thermal conductivity, thermal diffusivity, specific heat capacity) and dielectric properties (dielectric constant, loss factor and penetration depth) were evaluated. The reconstituted potato flakes were reheated in a microwave oven and the temperatures were recorded during and after microwave exposure. Temperatures during reheating decreased with increasing water, butter and salt content. Results show that temperatures during microwave reheating require empirical measurement as opposed to prediction due to changes in composition, thermal and dielectric properties. Reformulation offers the manufacturers an option for altering the temperatures following microwave reheating, however, the magnitude of the formulation changes required may be quite large. The data presented is useful in the preparation of computer models and simulations of microwave heating

The Effect of non-Thermal Processing Technologies on Microbial Inactivation: An Investigation into sub-Lethal Injury of Escherichia Coli and Pseudomonas Fluorescens

In recent years, there has been an increased interest in food processing technologies that could lessen the thermal impact on food products. In the present study, thermosonication (TS) and pulsed electric fields (PEF), applied individually or in combination (TS/PEF), were investigated to determine their effects on inactivation and sub-lethal injury of Pseudomonas fluorescens and Escherichia coli. TS was applied at a low (L) and high (H) wave amplitude (18.6 μm and 27.9 μm, respectively), while PEF was applied at a low and high electrical field strength (29 kV cm−1 and 32 kV cm−1, respectively). In addition, the inhibitory effects of TS/PEF combined were assessed. For P. fluorescens, when applied individually, TS and PEF resulted in ≤9% and ≤47% inactivation, respectively, with 8% sub-lethal injury following PEF treatment. However, TS/PEF treatment caused ≤48% inactivation and ≤34% sub-lethal injury, respectively. For E. coli, TS caused ≤6% inactivation, and ≤2% sub-lethal injury, while PEF treatment alone caused inactivation and sub-lethal injury of 86% and 29%, respectively. TS/PEF caused a maximum of 66% inactivation, while sub-lethally injuring approximately 26% of the of E. coli population. The present study confirms the ability of TS and PEF to inactivate microorganisms, but shows that some bacteria were not killed, but sub-lethally injured

Analysis of heat transfer during ohmic processing of a solid food

To produce a safe cooked food product it is necessary to ensure a uniform heating process. The aim of this study was to develop a mathematical model of a solid food material undergoing heating in a cylindrical batch ohmic heating cell. Temperature profiles and temperature distribution of the ohmic heating process were simulated and analysed via experimental and mathematical modelling which incorporated appropriate electromagnetic and thermal phenomena. Temperature profiles were measured at nine different symmetrically arranged locations inside the cell. The material was ohmically heated imposing a voltage of 100 V, while electrical field and thermal equations were solved for experimental and theoretical models by the use of FEMLAB, a finite element software. Reconstituted potato was chosen to represent a uniform solid food material and physical and electrical properties were determined prior to the experiment as a function of temperature. The simulation provided a good correlation between the experimental and the mathematical model. No cold spots within the product were detected but both experimental and model data analysis showed slightly cold regions and heat losses to the electrode and cell surfaces. The designed model could be used to optimize the cell shape and electrode configurations and to validate and ensure safe pasteurisation processes for other solid food materials

Combined Treatment with Mild Heat, Manothermosonication and Pulsed Electric Fields Reduces Microbial Growth in Milk.

In recent years, there has been considerable interest in non-thermal milk processing. The objective of the present study was to assess the efficacy of two non-thermal technologies (manothermosonication; MTS, and pulsed electric fields; PEF) in comparison to thermal pasteurisation, by assessing the microbial levels of each of these milk samples post-processing. Homogenised milk was subjected to MTS (frequency; 20 kHz, amplitude; 27.9 μm, pressure; 225 kPa) at two temperatures (37 °C or 55 °C), before being immediately treated with PEF (electric field strength; 32 kV/cm, pulse width; 10 μs, frequency; 320 Hz). Thermal pasteurisation (72 °C, 20 s) was included as a control treatment. Microbial content of each milk sample was monitored over a 21-day period. It was determined that milks treated with MTS/PEF at 37 °C and 55 °C contained lower microbial levels than raw milk for a certain duration, but after 14 days milk which had been pasteurised by conventional methods contained significantly (P < 0.05) less microorganisms. However, milks treated with MTS/PEF contained significantly (P < 0.05) fewer microorganisms than raw milk at each time point. Although not as effective as pasteurisation, the present study demonstrates the ability of MTS/PEF treatment to reduce microbial content of milk, while avoiding prolonged heat exposure to temperatures such as those used during conventional (thermal) pasteurisation

Effect of applying crust-freezing after skin-packaging on the natural microflora of Atlantic salmon (Salmo salar) during storage at low temperatures

peer-reviewedThe aim of the present study was to evaluate the effect of crust-freezing (CF) on fresh salmon fillets in skin-packaging during storage at −2.0°C. After CF, all treated samples and untreated controls were stored in a refrigerated cabinet for 20 d. Sampling was carried out at days 0, 2, 6, 8, 10, 14 and 20 in order to analyse total volatile basic nitrogen (TVB-N) and levels of mesophilic and psychrophilic viable counts (MVC and PVC). Enterobacteriaceae (ENT), lactic acid bacteria (LAB), H2S-producing bacteria (SPB) and Pseudomonas spp. (PSE). No significant differences in TVB-N were found between samples except for those taken on day 20 where TVB-N levels of CF samples were lower than controls. Our results suggest that ENT might be the limiting microbial group to determine the end of shelf-life. Thus, if this group is used as an indicator of acceptability, the shelf-life of salmon can be extended from 8 to 20 d when skin-packed and then treated with CF