Inactivation of MS2 F(+) coliphage on lettuce by a combination of UV light and hydrogen peroxide.

The efficacy of a produce decontamination method based on a combination of UV light (254 nm) and hydrogen peroxide (H2O2) to inactivate the MS2 F(+) coliphage inoculated onto iceberg lettuce was evaluated. Lettuce inoculated with 6.57 log PFU of MS2 was reduced by 0.5 to 1.0 log unit when illuminated with UV light alone for 20 to 60 s (12.64 to 18.96 mJ/cm2). In contrast, a 3-log reduction in MS2 was achieved with 2% (vol/vol) H2O2 spray delivered at 50 degrees C. No significant increase in log count reduction (LCR) was observed when H2O2 and UV light were applied simultaneously. However, H2O2 sprayed onto lettuce samples for 10 s, followed by a further 20-s UV illumination, resulted in an LCR of 4.12 that compares with the 1.67 obtained with 200 ppm of calcium hypochlorite wash. No further increase in MS2 inactivation was achieved by the use of either longer H2O2 spray or UV illumination times. The extent of MS2 reduction was significantly (P < 0.05) decreased when the H2O2 spray was delivered at 10 or 25 degrees C compared with 50 degrees C. In the course of aerobic storage at 4 degrees C, lettuce treated with UV light and H2O2 (10 or 25 degrees C) developed discoloration (polyphenol accumulation) within 6 days. In contrast, lettuce treated with UV light and H2O2 at 50 degrees C developed less discoloration within this time period and was comparable to untreated controls. This study demonstrated that the combination of UV light and H2O2 represents an alternative to hypochlorite-based washes to reduce the carriage of viruses on fresh produce.

Inactivation of human pathogens and spoilage bacteria on the surface and internalized within fresh produce by using a combination of ultraviolet light and hydrogen peroxide.

AIMS: To evaluate the efficacy of ultraviolet (UV) light (254 nm) combined with hydrogen peroxide (H(2)O(2)) to inactivate bacteria on and within fresh produce. METHODS AND RESULTS: The produce was steep inoculated in bacterial cell suspension followed by vacuum infiltration. The inoculated samples were sprayed with H(2)O(2) under constant UV illumination. The log count reduction (LCR) of Salmonella on and within lettuce was dependent on the H(2)O(2) concentration, temperature and treatment time with UV intensity being less significant. By using the optimized parameters (1.5% H(2)O(2) at 50 degrees C, UV dose of 37.8 mJ cm(-2)), the surface Salmonella were reduced by 4.12 +/- 0.45 and internal counts by 2.84 +/- 0.34 log CFU, which was significantly higher compared with H(2)O(2) or UV alone. Higher LCR of Escherichia coli O157:H7, Pectobacterium carotovora, Pseudomonas fluorescens and Salmonella were achieved on leafy vegetables compared with produce, such as cauliflower. In all cases, the surface LCR were significantly higher compared with the samples treated with 200 ppm hypochlorite. UV-H(2)O(2)-treated lettuce did not develop brown discolouration during storage but growth of residual survivors occurred with samples held at 25 degrees C. CONCLUSIONS: UV-H(2)O(2) reduce the bacterial populations on and within fresh produce without affecting the shelf-life stability. SIGNIFICANCE OF THE STUDY: UV-H(2)O(2) represent an alternative to hypochlorite washes to decontaminate fresh produce.

Efficacy of radio frequency cooking in the reduction of Escherichia coli and shelf stability of ground beef.

The effectiveness of radio frequency (RF) cooking on the inactivation of Escherichia coli in ground beef and its effect on the shelf stability of ground beef were investigated with a comparison to hot water-bath cooking. E. coli K12 was used as a target bacterium instead of E. coli O157:H7. The ground beef samples inoculated with E. coli K12 (ampr) were heated until the centre temperature of each sample reached 72 degrees C. These samples were then stored at 4 degrees C for up to 30 days. The enumeration of E. coli K12, background E. coli and coliform counts in ground beef samples was carried out for shelf-life study. Although both methods significantly reduced E. coli K12 (ampr), E. coli and coliform counts and extended the shelf-life, RF cooking had a shorter cooking time, and more uniform heating. Thus, RF cooking of meat has a high potential as a substitute for the hot water-bath cooking.

Estimation of ultrasound attenuation and dispersion using short time Fourier transform.

Determination of the acoustic attenuation and dispersion has important applications in ultrasound tissue characterization and non-destructive material testing. Current signal processing methods Fourier transform of ultrasound signals to get the spectra of amplitude and phase to estimate respectively the attenuation and dispersion of a given medium. These methods are frequency domain method and obsessed with ambiguity issue in the phase unwrapping calculation. Conventional ultrasound velocity measuring method detects the time of arrival of a pulse (or echo) signal, which is a time domain method to compute group velocity (not phase velocity). This paper presents a novel approach based on the short time Fourier transform (STFT)--a time-frequency analysis, to estimate the ultrasonic dispersion and attenuation. Only the amplitude information of the pulse-signal spectra is used. Based on the time-frequency presentation, the attenuation coefficient of the signal is obtained by computing the amplitude decay of pulse spectrum in time domain, while phase velocities are obtained based on the "time-of-flight" (TOF) of the mono frequency component of the pulse signals. As a result, we eliminate the ambiguity issue in phase angle calculation. Furthermore, the proposed method makes the phase velocity pedagogically intuitive for novice users. The paper presents experiments to evaluate demonstrate the performance of the proposed method.

A self-aligning ultrasound sensor for detecting foreign bodies in glass containers.

This paper introduces the principle and design of an ultrasonic transducer system with auto-alignment mechanism. The proposed system is used for detecting foreign bodies (FBs) in beverage containers. Variation in reflection amplitude is analyzed as a function of the ultrasound beam incident angle to beverage container surface. It is concluded that there exists a quadratic relationship between the strength of the reflected signal and the incident angle. Furthermore, a calculation for effective angular increment for searching the normal of a curved surface is introduced. Experiments conducted using the prototype demonstrated that FBs are detectable in various juices. Experiments also observed some false echo signals that occur due to curved container surface. Threshold in confined time region is therefore set to ensure no fail of detection in low signal to noise ratio. This design is also applicable to non-destructive inspection for metal canned food.

Radio frequency cooking of ground, comminuted and muscle meat products.

The effect of radio frequency (RF) cooking, on the quality (colour, water holding capacity, texture), heating rate, and temperature history of three types of meat products (ground, comminuted and muscle), was investigated after heating to centre temperature of 72 °C in a 1.5 kW RF heater operating at 27.12 MHz. The results were compared with that obtained from heating in a water bath. RF cooking of processed meat products resulted in a decreased cooking time (5.83, 13.5, and 13.25 min for ground beef, comminuted meat, and muscle, respectively compared to 151, 130, and 109 min in water bath), lower juice losses, acceptable colour, water holding capacity and texture. The results indicate that when using RF, ground beef has the highest power efficiency (60.17%) followed by comminuted meat (44.41%), and muscle (43.38%). However, the texture of ground beef was too chewy and elastic. The muscle's colour was inferior. The comminuted and muscle meat products exhibited average energy efficiency with improved texture. The comminuted meat displayed a large cross-sectional temperature differential, possible due to uneven salt distribution. The well mixed comminuted and ground meat products appeared to be most promising for RF cooking.

Prediction of food thermal process evaluation parameters using neural networks.

Two neural networks (ANN) were developed to predict thermal process evaluation parameters g and f(h)/U (the ratio of heating rate index to the sterilizing value), respectively. The temperature change required for the thermal destruction curve to traverse one log cycle (z), cooling lag factor (j(c)) andf(h)/U were input variables for predicting g and z, while j(c) and g were inputs for predicting f(h)/U. The data used to train and verify the ANN were obtained from reported values. Shrinking of input and output variables using natural logarithm function improved the prediction accuracy. The use of "Wardnets" with three slabs of 14 nodes in each slab, with a learning rate of 0.7 and momentum of 0.9 provided the best predictions. The g (unshrunk values) was predicted with a mean relative error of 1.25 +/- 1.77%, and a mean absolute error of 0.11 +/- 0.16 degrees F. The f(h)/U was predicted with a mean relative error of 1.41 +/- 3.40%, and a mean absolute error of 2.43 +/- 15.97, using 10 nodes in each slab. The process time calculated using the g from the ANN models closely followed the time calculated from the tabulated gvalues (RMS=0.612 min, average absolute error=0.466 min with an S.D. of 0.400 min).

Reduction in levels of Escherichia coli O157:H7 in apple cider by pulsed electric fields.

Many studies have demonstrated that high voltage pulsed electric field (PEF) treatment has lethal effects on microorganisms including Escherichia coli O157:H7; however, the survival of this pathogen through the PEF treatment is not fully understood. Fresh apple cider samples inoculated with E. coli O157:H7 strain EC920026 were treated with 10, 20, and 30 instant charge reversal pulses at electric field strengths of 60, 70, and 80 kV/cm, at 20, 30, and 42 degrees C. To accurately evaluate the lethality of apple cider processing steps, counts were determined on tryptic soy agar (TSA) and sorbitol MacConkey agar (SMA) to estimate the number of injured and uninjured E. coli O157:H7 cells after PEF treatment. Cell death increased significantly with increased temperatures and electric field strengths. A maximum of 5.35-log10 CFU/ml (P < 0.05) reduction in cell population was achieved in samples treated with 30 pulses and 80 kV/cm at 42 degrees C. Cell injury measured by the difference between TSA and SMA counts was found to be insignificant (P > 0.05). Under extreme conditions, a 5.91-log10 CFU/ml reduction in cell population was accomplished when treating samples with 10 pulses and 90 kV/cm at 42 degrees C. PEF treatment, when combined with the addition of cinnamon or nisin, triggered cell death, resulting in a reduction in E. coli O157:H7 count of 6 to 8 log10 CFU/ml. Overall, the combination of PEF and heat treatment was demonstrated to be an effective pasteurization technique by sufficiently reducing the number of viable E. coli O157:H7 cells in fresh apple cider to meet U.S. Federal Drug Administration recommendations.

Prediction of temperature and moisture content of frankfurters during thermal processing using neural network.

An artificial neural network (ANN) was developed to predict temperature and moisture content of frankfurters during smokehouse cooking. Fat protein ratio (FP), initial moisture content, initial temperature, radius of frankfurter, ambient temperature, relative humidity and process time were input variables. Temperature at the frankfurter centre, average temperature of the frankfurter and average moisture content (d.b) of the frankfurter were outputs. Network training data were obtained from validated heat and mass transfer models simulating temperature and moisture profiles of a frankfurter. Backpropagation method was used for ANN training. Selection of hidden nodes, learning rate, momentum and range of input variables were important to ANN prediction. The FP was not an important factor in predictions.

Development and application of soy-protein films to reduce fat intake in deep-fried foods.

A soy protein film coating was developed and evaluated to reduce fat transfer in deep-fried foods during frying. Soy protein isolate solutions (10% SPI) with 0.05% gellan gum as plasticizer cooled after being held at 80 °C for 20 min provided suitable films. There was a significant fat reduction (55.12 (±6.03)%db) between fried uncoated and coated discs of doughnut mix. The same films were used on potato fries. Some panellists observed a slight difference between the coated and uncoated fries but many preferred the coated fries over the uncoated ones. Penetration test on potato fries showed no significant difference between the texture of coated (SPI with gellan gum) and the uncoated fried samples. A solution of 10% SPI with 0.05% gellan gum is recommended for coating foods to reduce fat intake during deep-fat frying. © 2000 Society of Chemical Industry.

Regulating the use of degraded oil/fat in deep-fat/oil food frying.

During frying, the degradation of oil produces harmful compounds. Improper monitoring of oil-discard times in restaurants either risks the public health or causes financial losses to industries. Measuring the oil quality is a complex problem and an online sensor is needed. The process of frying reviewed includes moisture, heat and fat/oil transfer, crust formation and various structural, textural and chemical changes in the product, and degradation of frying medium. Some of the European nations and the U.S. have specific regulations against the use of deteriorated frying oils. Due to the absence of a suitable online frying oil quality sensor for restaurant situations, it is difficult to implement any regulation against the use of deteriorated frying oil. Based on various regulations, a model regulation to increase the safety and quality of fried foods is discussed. Background and requirements for developing an online sensor to measure frying oil quality are discussed. Other related areas reviewed in this article are factors affecting oil penetration and absorption by the food, surfactant theory of frying, analytical indices, quick tests and acceptability of frying oil.

Electroporation of cell membranes: a review.

The study of the electroporation on biomembranes has become one of the most exciting topics in the biophysical and biotechnological areas. Researchers all over the world have been focused on four major areas: measurements of transmembrane potential (TMP); dynamics of electroporation such as time sequence, properties of electropores such as size, structure, and population; membrane permeabilization and breakdown theory; and the effects of secondary factors such as ions type and cell growth stage on electroporation. This article reviews some of the recent discoveries and theories on this subject. Studies on TMP and pore dynamics remain a difficult task. Since the area of electroporation on a biomembrane is small (less than 0.1% of total surface area) and the time sequence of electropores is in the submicrosecond range measuring devices with subtle detection and time resolution are required. While more and more studies have shown the formation sequence of electropore(s) at specific locations on various biomembranes, the pore(s) widening process and the subsequent membrane breakdown mechanisms remain controversial. The influence of electromechanical stress or transmembrane potential on membrane discharge and rupture seems to be a function of various factors such as membrane properties, external medium, and the protocols of electroporators.

Changes in colour of beef m. longissimus dorsi muscle during ageing.

The effects of vacuum packaging, chilling rate (slow or fast), and fat cover thickness (⩽4 mm or 7-8 mm) on the colour parameters of beef m. longissimus dorsi muscle were assessed during ageing. The m. longissimus dorsi muscle was aged on the carcass or in vacuum packaging. Muscle samples for analysis were taken on days 0 (24 hr post mortem), 2, 4, 8, 12 and 16 to ascertain the parameters. Ageing time influenced all colour parameters, while chilling rate affected lightness ('L'), yellowness ('b'), and hue angle difference (HD), and fat cover thickness influenced 'L' and 'b' only.

Optimum conditions for beef carcass chilling.

Optimum chilling schemes for a two- or three-stage chilling system were developed using a validated heat and mass transfer model and a pattern search algorithm. The optimization was performed for the ambient temperature during each stage for an air velocity of 0·5 m/s and 90% relative humidity. The experiments were conducted to evaluate the effect of the optimum conditions on beef quality after ageing.

Effects of Kramer-shear-press-test conditions on the shear properties of beef products.

Tenderness parameters of bologna, salami, and pastrami were measured by Kramer-shear tests. Three levels of sample size and crosshead speed were used. The initial yield force did not change significantly as the sample size changed. The friction between the sample and press, and the sample's stress and strain changes, were studied to explain the effect of sample size on shear properties. Peak-force distance (PD) increased proportionally to the increase in fill percentage. Peak force (PF) and initial-yield distance (IYD) increased partly as the fill percentage increased. The slope changed with the change in IYD, and break area (BA) changed proportionally to the changes in PF and PD. Recommended test conditions for bologna are 50% fill percentage at any crosshead speed; those for salami are 25% fill percentage at 150-mm/min crosshead speed; and those for pastrami are 75% fill percentage at 250-mm/min crosshead speed.

Changes in pH and water holding properties of Longissimus dorsi muscle during beef ageing.

The effects of vacuum packaging, chilling rate (slow or fast), and fat cover thickness (≤ 4 mm or 7-8 mm) on pH and water-holding properties of longissimus dorsi muscle were assessed during beef ageing. The longissimus dorsi muscles were aged on the carcass or in vacuum packaging. Muscle samples were taken on days 0 (24 h post-mortem), 2, 4, 8, 12 and 16 to measure these properties. Ageing time significantly influenced muscle pH and cooking loss; however, interaction fat × chill × time affected press juice. The pH was also influenced by vacuum-packaged ageing. Press juice positively correlated with cooking loss and pH.

Effects of various cellulose gums on the quality parameters of low-fat breakfast sausages.

Composition, textural, viscoelastic, hydration, colour and sensory attributes of regular (26% fat) and low-fat (13%) pork breakfast sausages with and without cellulose gums (two types of carboxymethyl cellulose (CMC-I and -II) and microcrystalline cellulose (MCC-I and -II)) were investigated. The fat was replaced with water in low-fat products. In cooked low-fat sausages, the fat content decreased by 52-60%, and moisture content reduced by 61-65% of the initial values. The cooked high-fat products' composition showed an increase of about 6% fat and a decrease of 7% moisture due to cooking. MCC was more effective in retaining moisture compared to CMC. Product lightness was reduced due to both CMC and MCC. Gums have not affected fat content, water holding capacity, redness, yellowness, hardness, chewiness and gumminess. High-fat products were less elastic and easier to chew. Springiness was reduced by CMC-II and cohesiveness by other cellulose gums.

Kinetics of hydration properties of meat emulsions containing various fillers during smokehouse cooking.

The cooking kinetics of meat emulsions containing various fillers was determined by monitoring changes in hydration properties such as cooking loss and water-holding capacity during smokehouse cooking. Press juice, consumer cook test and emulsion stability of cooked product were also determined. The fillers used were buttermilk powder, corn starch, microcrystalline cellulose, modified corn starch, modified wheat flour, soy-protein concentrate and whey-protein concentrate. The cooking process was modelled using reaction kinetics and Eyring's absolute reaction rate theory. Enthalpy and entropy changes of activation were calculated for various properties and fillers.

Kinetics of pH and colour of meat emulsions containing various fillers during smokehouse cooking.

The cooking kinetics of meat emulsions containing various fillers was determined by monitoring changes in pH and colour during smokehouse cooking. The fillers used were buttermilk powder, corn starch, microcrystallline cellulose, modified corn starch, modified wheat flour, soy-protein concentrate and whey-protein concentrate. The cooking process was modelled using reaction kinetics and Eyring's absolute reaction rate theory. Enthalpy and entropy changes of activation were calculated for various properties and fillers.

Phosphates and antioxidants as cryoprotectants in meat batters.

The gelation and rheological properties of minced beef frozen and stored at -18°C for 6 months without additives, with salt (1·5% NaCl), tripolyphosphate (TPP 0·5%), sodium acid pyrophosphate (SAPP 0·5%) and an antioxidant mix (BHA + BHT, 200 ppm) were studied. The relationships between shear rate and shear stress for the different treatments were nonlinear and resembled the Bingham pseudoplastic behaviour. Continuous evaluation of the modulus of rigidity (G) during cooking (0·5°C/min) revealed higher G values for the unfrozen phosphate treatments. Salt addition resulted in significantly lower G values of the stored meat compared to the control. Antioxidant addition retarded some of these effects. Among the phosphates, TPP was the best in maintaining the same G values as the control. Water-holding capacity (after salt addition) was increased after phosphate addition in the unfrozen meat and did not change after storage. The control, NaCl and antioxidant treatments showed an increase in WHC during storage.