An assessment of the effect of pulsed electrical fields on tenderness and selected quality attributes of post rigour beef muscle.

The effect of conventional and PEF treatment (electric field strength: 1.1-2.8 kV cm(-1); energy density: 12.7-226 kJ/kg), frequency (5-200 Hz) and pulse number (152-300) on selected quality attributes of beef Semitendinosus (ST) was investigated. While PEF is viewed as a "non-thermal" treatment, it can induce moderate temperature rises (∆T). To eliminate any potential effect of mild temperature increases, PEF treated samples were compared to conventionally treated (water bath) samples exposed to similar temperature rises (5-35 °C) and handling conditions. Weight loss, conductivity, water holding properties and particle sizes were measured pre- and post-treatment. PEF treatment that induced a ∆T of 22 °C significantly (P<0.05) affected weight loss of samples post treatment. Particle size analysis of the extracted myofibrils showed PEF significantly (P<0.05) affected the myofibrils while weight loss results suggest that PEF treatment may have led to slight changes in the cell membrane leading to more water loss. However, instrumental texture was unaffected by the treatments applied.

Susceptibility of Campylobacter to high intensity near ultraviolet/visible 395±5nm light and its effectiveness for the decontamination of raw chicken and contact surfaces.

Campylobacter is an important cause of human gastroenteritis worldwide. Chicken meat is frequently contaminated with this organism and is considered to be a significant source of infection. It has been predicted that lowering the numbers of Campylobacter on chicken meat can reduce the risk to public health. The aims of the current study were to investigate the susceptibility of Campylobacter to high intensity near ultraviolet/visible (NUV-vis) 395±5nm light and to examine its potential for the microbiological decontamination of raw chicken and contact surfaces. Exposure of Campylobacter jejuni and Campylobacter coli to NUV-vis light of irradiances was assessed at three distances (3, 12 and 23 cm) from the light source for up to 10 min, corresponding to doses of 0.06 to 18J/cm(2). Overall, levels of inactivation in liquid and on raw chicken improved with longer exposure times and shorter distances from the light source. Reductions of more than 7log(10)CFU/mL were achieved for Campylobacter isolates in liquid following 2 min exposure at 3 cm. Exposure of skinless chicken fillet to NUV-vis light for 1 or 5 min at 3 cm distance reduced C. jejuni by 2.21 and 2.62 log(10)CFU/g, respectively. Increasing the treatment time to 10 min did not significantly increase the level of inactivation. In general, NUV-vis light treatment did not affect the colour of raw chicken. Excluding treatments which resulted in excessive heating (>50°C) of chicken skin, a maximum reduction of 0.95 log(10)CFU/g was achieved for C. jejuni following 10 min exposure to NUV-vis light at 12 cm (P<0.05). For Enterobacteriaceae and total viable counts, significant reductions were achieved only on chicken fillet samples. Light treatments were significantly effective for decontaminating contact surfaces as there were no C. jejuni recovered from stainless steel or cutting board surfaces after NUV-vis light treatments from an initial inoculum of 2-4 log(10)CFU/cm(2) (P<0.05). The current study demonstrates potential for the use of NUV-vis light for the inactivation of Campylobacter spp. in liquids, on raw chicken and contact surfaces. The incorporation of this technology could be implemented in a commercial processing plant at various stages, for example to decontaminate carcasses during air chilling. It could also be applied at critical stages within the plant to control microbial contamination on equipment surfaces.

Effect of crust freezing applied alone and in combination with ultraviolet light on the survival of Campylobacter on raw chicken.

The application of crust freezing (CF) applied as a stand-alone treatment or in combination with ultraviolet (UV) light for reducing the level of artificially inoculated Campylobacter jejuni on raw chicken was investigated. CF air temperatures of -5, -15 and -27 °C (±3 °C) with freezing times of 70, 15 and 6 min, respectively, were used. The level of C. jejuni on chicken was also examined following subsequent refrigerated (0-4 °C) storage at 3 and 7 days. All CF treatments resulted in significant reductions compared to untreated controls (P < 0.05). Although combining CF with UV also resulted in significant reductions for C. jejuni, the combined treatments were generally no more effective than treatment by CF alone. Overall, the color of chicken drumsticks was not affected by CF treatments (P ≥ 0.05). In general, CF resulted in increased drip loss (P < 0.05), which increased over storage time and was greater at higher CF temperatures. The current study indicates that CF has potential for reducing the levels of C. jejuni by between 0.5 and 1.5 log(10) CFU/g and impacts minimally on the color of treated skin.

Efficacy of high-intensity pulsed light for the microbiological decontamination of chicken, associated packaging, and contact surfaces.

The efficacy of high-intensity light pulse (HILP) technology (3 Hz, maximum of 505 J/pulse, and a pulse duration of 360 µs) for the decontamination of raw chicken and associated packaging and surface materials was investigated. Its ability to reduce microbial counts on raw chicken through plastic films was also examined. Complete inactivation of Campylobacter spp., Escherichia coli, and Salmonella Enteritidis in liquid was achieved after 30 sec HILP treatment. Reductions of 3.56, 4.69, and 4.60 log10 cfu/cm²) were observed after 5 sec HILP treatment of Campylobacter jejuni, E. coli, and Salmonella Enteritidis inoculated onto packaging materials and contact surfaces, respectively. The greatest reductions on inoculated chicken skin were 1.22, 1.69, and 1.27 log10 cfu/g for C. jejuni, E. coli, and Salmonella Enteritidis, respectively. Corresponding reductions on inoculated skinless breast meat were 0.96, 1.13, and 1.35 log10 cfu/g. The effectiveness of HILP treatment for reducing microbial levels on chicken increased as the film thickness decreased. HILP treatments of 2 sec did not significantly affect the color of raw chicken although treatments of 30 sec impacted color. This study has shown HILP to be an effective method for the decontamination of packaging and surface materials. Additionally, it has demonstrated the potential of HILP to be used as a decontamination method for packaged chicken.

Ohmic cooking of whole beef muscle--evaluation of the impact of a novel rapid ohmic cooking method on product quality.

Cylindrical cores of beef semitendinosus (500g) were cooked in a combined ohmic/convection heating system to low (72 degrees C, LTLT) and high (95 degrees C, HTST) target end-point temperatures. A control was also cooked to an end-point temperature of 72 degrees C at the coldest point. Microbial challenge studies on a model meat matrix confirmed product safety. Hunter L-values showed that ohmically heated meat had significantly (p<0.05) lighter surface-colours (63.05 (LTLT) and 62.26 (HTST)) relative to the control (56.85). No significant texture differences (p>/=0.05) were suggested by Warner-Bratzler peak load values (34.09, 36.37 vs. 35.19N). Cook loss was significantly (p<0.05) lower for LTLT samples (29.3%) compared to the other meats (36.3 and 33.8%). Sensory studies largely confirmed these observations. Cook values were lower for LTLT (3.05) while HTST and the control were more comparable (6.09 and 7.71, respectively). These results demonstrate considerable potential for this application of ohmic heating for whole meats.

Ohmic cooking of whole beef muscle - Optimisation of meat preparation.

Uniform ohmic heating of solid foods primarily depends on the uniformity of electrolyte distribution within the product. Different preparation techniques were tested in an attempt to ensure an even salt dispersion within a full beef muscle (biceps femoris). Meat pieces were soaked, injected and tumbled using a range of procedures before ohmic cooking at pasteurization temperatures. A final preparation method (multi-injection (five points) with a 3% salt solution followed by 16h tumbling) was validated. Selected quality parameters of the ohmically cooked products were compared to steam cooked products. Ohmically heated meat had a significantly (P<0.05) uniform lighter and less red colour. Cook loss was significantly lower (P<0.05) in ohmic samples and in relation to tenderness ohmic heated samples were tougher (P<0.05) though the difference was only 5.08N. Comparable cook values were attained in the ohmic and conventionally cooked products.

Ohmic heating of meats: Electrical conductivities of whole meats and processed meat ingredients.

The ohmic heating rate of a food is highly influenced by its electrical conductivity (σ). A survey of σ values of commonly used meat ingredients when dispersed as 5% (w/w) aqueous solutions/suspensions was undertaken. A subset was further investigated at typical usage levels in solution/suspension, and/or when incorporated into beef blends, while σ of selected cuts from five meat species (beef, pork, lamb, chicken and turkey) was also measured. Measurements were made from 5 to 85°C and showed a linear increase in σ values with increasing temperature. In processed beef, addition of sodium chloride and phosphate (P22) caused a significant increase in σ which in turn would lead to an increase in ohmic heating rates. Furthermore, whole meats with lower endogenous fat or processed meats with the least added fat displayed higher σ and reduced ohmic heating times. In beef maximum σ was observed when fibres were aligned with the current flow.

Combined effect of temperature and pulsed electric fields on apple juice peroxidase and polyphenoloxidase inactivation.

Pulsed electric fields (PEF) were applied to freshly prepared apple juice using a laboratory scale continuous PEF system to study the feasibility of inactivating peroxidase (POD) and polyphenoloxidase (PPO). Square wave PEF using different combinations of electric field strength, pre-treatment temperature and treatment time were evaluated in this study and compared to conventional pasteurisation (72°C; 26s). Inactivation curves for the enzyme were plotted for each parameter and inactivation kinetics were calculated. Results showed the highest level of decrease in the enzymatic activity of 71% and 68%, for PPO and POD, respectively, were obtained by using a combination of preheating to 50°C, and a PEF treatment time of 100µs at 40kV/cm. This level of inactivation was significantly higher (P<0.05) than that recorded in juice processed by conventional mild pasteurisation where the activity of PPO and POD decreased by 46% and 48%, respectively. The kinetic data for the inactivation of both enzymes could be described using a 1st-order model (P<0.001).

Flavouring reduced fat high fibre cheese products with enzyme modified cheeses (EMCs).

Medium (13%) and low (2%) fat imitation cheeses (pH 6 or 5.5) were flavoured with 5% w/w EMC containing 16%, 28% or 47% total free fatty acids (low to high levels of hydrolysis, respectively) and were examined by a sensory panel. Aroma active short-chain free fatty acids were monitored using gas chromatographic techniques. Regardless of cheese pH or EMC composition, panellists ranked all medium-fat cheeses similarly. Low-fat cheeses flavoured (pH 6 or 5.5) with low or medium lipolysis EMC were described as 'well-balanced' and 'cheesy' and were significantly more preferred to cheeses containing high hydrolysis EMCs. Low-fat cheeses were least preferred of all cheeses because of 'very intense' bursts of off-flavours. Lower pH cheeses were softer and less melting. Higher fat levels in imitation cheese modulated a greater retention of fat-based flavour compounds and improved their release during consumption more than did lower fat levels.

An examination of factors affecting radio frequency heating of an encased meat emulsion.

The potential of radiofrequency (RF) heating for rapid cooking of a cased comminuted meat emulsion (white pudding) to a pasteurisation temperature of 73°C was examined. Immersion of the product in water was essential in order to prevent thermal damage to the casings by electrical arcing effects during heating. Using a polyethylene heating cell with non-circulating water the applied RF power, primary electrode distance as well as the mineral content, temperature and volume of the surrounding water all influenced the efficiency of the RF heating. Under optimised conditions maximum/minimum temperature gradients (ΔT) across the products in excess of 15°C were observed. These could be reduced to around 6°C by heating the white puddings in a cell operating with recirculating hot water (80°C). Using an oven power output of 450W a 4.3-fold reduction in cooking time compared to conventional steam oven cooking could be achieved.

Radio frequency heating of beef rolls from biceps femoris muscle.

Chemical, physical and sensory aspects of quality were compared on encased rolls (1kg) prepared from single muscle beef (biceps femoris) cooked in a steam oven (80°C) or by radio frequency (RF) heating (500W, 27.12MHz) under recirculating water at 80°C. The RF protocol reduced cooking times to 23 and 31% of steam cooking times, respectively, in non-injected meat (PG1) and in rolls prepared with curing brines possessing similar dielectric properties (PG2-4). Compared to steam heating, cooking yields were significantly higher (P<0.05) and instrumental texture measurements related to toughness significantly lower (P<0.05) for RF cooked PG1 rolls and for meat injected with brines containing water binding dielectrically inactive additives (PG4) but not for brined rolls lacking the latter ingredients (PG2 and PG3). Participants in a 50 member untrained sensory panel were unable to detect texture differences which had been indicated by instrumental analysis for PG1 and PG4.

Development and validation of a food-frequency questionnaire for the determination of detailed fatty acid intakes.

OBJECTIVE: To validate a fat intake questionnaire (FIQ) developed to assess habitual dietary intake while focusing on the assessment of detailed fatty acid intake including total trans unsaturated fatty acids (TUFA). DESIGN: An 88 food item/food group FIQ was developed using a meal pattern technique. Validation was achieved by comparison with dietary intake assessed by a modified diet history (DH) in a cross-over design. Eighty-four individuals supplied adipose tissue biopsies for linoleic acid and total TUFA analysis as an independent validation of the FIQ and DH. SETTING: Medical Centre, Dublin Airport, Republic of Ireland. SUBJECTS: One hundred and five healthy volunteers (43 females and 62 males aged 23-63 years). RESULTS: Significant correlations (P<0.0005) were achieved for intakes of energy (0.78), total fat (0.77), saturated fat (0.77), monounsaturated fat (0.63), polyunsaturated fat (0.73), TUFA (0.67) and linoleic acid (0.71) assessed by the FIQ compared with the DH. Linoleic acid intake assessed by the FIQ and the DH was significantly correlated with adipose tissue concentrations (r=0.58 and 0.49, respectively; P<0.005); however, total TUFA intake was poorly correlated with adipose tissue concentrations (r=0.17 and 0.10 for FIQ and DH, respectively). CONCLUSIONS: The FIQ compared favourably with the DH in assessing habitual diet, in particular fatty acid intake. In addition, the FIQ was successfully validated against the linoleic acid composition of adipose tissue, an independent biomarker of relative fatty acid status. The FIQ could therefore be used as an alternative to the DH as it is a shorter, less labour-intensive method.