Chicken fillets subjected to UV-C and pulsed UV light: Reduction of pathogenic and spoilage bacteria, and changes in sensory quality.

We have compared the efficacy of continuous ultraviolet (UV-C) (254 nm) and pulsed UV light in reducing the viability of Salmonella Enteritidis, Listeria monocytogenes, Staphylococcus aureus, enterohemorrhagic Escherichia coli, Pseudomonas spp., Brochothrix thermospacta, Carnobacterium divergens, and extended-spectrum ß-lactamase producing E. coli inoculated on chicken fillet surface. Fluences from 0.05 to 3.0 J/cm2 (10 mW/cm2, from 5 to 300 s) used for UV-C light resulted in average reductions from 1.1 to 2.8 log cfu/cm2. For pulsed UV light, fluences from 1.25 to 18.0 J/cm2 gave average reductions from 0.9 to 3.0 log cfu/cm2. A small change in the odor characterized as sunburnt and increased concentration of volatile compounds associated with burnt odor posed restrictions on the upper limit of UV treatment, however no sensory changes were observed after cooking the meat. Treatments under modified atmosphere conditions using a UV permeable top film gave similar or slightly lower bacterial reductions. PRACTICAL APPLICATIONS: Ultraviolet (UV) light may be used for decontaminating the surface of food products and reduce viability of pathogenic and spoilage bacteria. Exposure of raw chicken fillet surface to various doses of continuous UV-C or pulsed UV light proposed in the present work represent alternatives for microbiological improvement of this product. Chicken fillets can be treated in intact packages covered with UV permeable top film, thus avoiding recontamination of the meat. UV-C light treatment is a low cost strategy with low maintenance, whereas pulsed UV light involves more elaborate equipment, but treatment times are short and less space is required. Both methods can be helpful for producers to manage the safety and quality of chicken fillets.

Cooking chicken at home: Common or recommended approaches to judge doneness may not assure sufficient inactivation of pathogens.

About one third of foodborne illness outbreaks in Europe are acquired in the home and eating undercooked poultry is among consumption practices associated with illness. The aim of this study was to investigate whether actual and recommended practices for monitoring chicken doneness are safe. Seventy-five European households from five European countries were interviewed and videoed while cooking chicken in their private kitchens, including young single men, families with infants/in pregnancy and elderly over seventy years. A cross-national web-survey collected cooking practices for chicken from 3969 households. In a laboratory kitchen, chicken breast fillets were injected with cocktails of Salmonella and Campylobacter and cooked to core temperatures between 55 and 70°C. Microbial survival in the core and surface of the meat were determined. In a parallel experiment, core colour, colour of juice and texture were recorded. Finally, a range of cooking thermometers from the consumer market were evaluated. The field study identified nine practical approaches for deciding if the chicken was properly cooked. Among these, checking the colour of the meat was commonly used and perceived as a way of mitigating risks among the consumers. Meanwhile, chicken was perceived as hedonically vulnerable to long cooking time. The quantitative survey revealed that households prevalently check cooking status from the inside colour (49.6%) and/or inside texture (39.2%) of the meat. Young men rely more often on the outside colour of the meat (34.7%) and less often on the juices (16.5%) than the elderly (>65 years old; 25.8% and 24.6%, respectively). The lab study showed that colour change of chicken meat happened below 60°C, corresponding to less than 3 log reduction of Salmonella and Campylobacter. At a core temperature of 70°C, pathogens survived on the fillet surface not in contact with the frying pan. No correlation between meat texture and microbial inactivation was found. A minority of respondents used a food thermometer, and a challenge with cooking thermometers for home use was long response time. In conclusion, the recommendations from the authorities on monitoring doneness of chicken and current consumer practices do not ensure reduction of pathogens to safe levels. For the domestic cook, determining doneness is both a question of avoiding potential harm and achieving a pleasurable meal. It is discussed how lack of an easy "rule-of-thumb" or tools to check safe cooking at consumer level, as well as national differences in contamination levels, food culture and economy make it difficult to develop international recommendations that are both safe and easily implemented.

Determination of critical levels of residual oxygen to minimize discoloration of sliced packaged Norwegian salami under light display.

Discoloration of sliced packaged salami is contributing to rejection of the product, food waste and economical loss. A combination of residual O2 in the headspace of packages and light is causing photooxidation and deterioration of colour. The aim of this study was to establish maximum tolerable concentrations of residual O2 in packages of salami slices with 100% N2 under light display at 4 and 20°C. Salami sausages had variable inherent O2 consumption rate. Storage of salami in 1% O2 in darkness did not induce discoloration. The upper limits for O2 for avoiding discoloration under light were variable in the range 0.1-1.0%, depending on temperature and type of salami. Display at 20°C increased the rate of O2 depletion compared to 4°C. To minimize discoloration, sliced and packaged salami should be stored in darkness at approximately 20°C until the level of residual O2 is reduced below a critical limit.

Functional properties of pre-rigor, pre-salted ground beef chilled with solid carbon dioxide.

Ground, pre-salted, pre-rigor semimembranosus muscles of beef were subjected to three treatments A=rapid carbon dioxide (CO(2)) chilling, B=slow CO(2) chilling and C=air chilling, and compared to a control D=slow air chilling of muscles, which were subsequently ground and salted post-rigor. Meat of the pre-rigor treatments A, B and C had higher pH values during processing, lower cooking loss, firmer texture and a lighter yellowish external colour of cooked patties than the post-rigor control D (p<0.05). The two CO(2) chilling regimes A and B had no detrimental effects on the functional properties of the pre-rigor meat. Sarcomere lengths did not differ in meat of the four treatments (p>0.05), indicating that early pre-salting protected the meat from cold shortening during rapid temperature decline. A process combination of grinding, followed by immediate pre-salting and CO(2) chilling within 312h post-mortem of non-stimulated beef muscles is likely to yield superior binding properties of cooked patties and similar ground beef products.

Color and thiobarbituric acid values of cooked top sirloin steaks packaged in modified atmospheres of 80% oxygen, or 0.4% carbon monoxide, or vacuum.

Case-ready fresh beef is typically packaged in a modified-atmosphere with approximately 80% oxygen and 20% carbon dioxide. Recently, USDA approved distribution of fresh meats in a master bag system using 0.4% carbon monoxide (CO). This study compared effects of packaging system (vacuum, 80% oxygen, 0.4% carbon monoxide), fresh meat storage time (7-21 days) and cooking temperature (49-79 °C) on extent of myoglobin denaturation, color and rancidity in cooked top sirloin steaks. Steaks packaged in 80% oxygen or CO retained desirable red color for 14 and 21 days storage, respectively. Steaks stored in 80% oxygen exhibited the greatest TBA values and myoglobin denaturation at all storage times and cooking temperatures. Steaks stored in high oxygen developed brown interior color at internal temperatures as low as 57 °C, the premature browning effect. Premature browning and rancidity associated with steaks packaged in 80% oxygen was prevented by packaging in 0.4% CO or vacuum.

Effects of carbon dioxide on yield, texture and microstructure of cooked ground beef.

The objective of the study was to find the effects of CO(2) gas on cooking loss, instrumental hardness and microstructural changes of ground beef heated to 70-83 °C. In two experiments, ground beef was stored for 4 days in 60% CO(2)/39.6% N(2)/0.4% CO and vacuum (1), or in 100% CO(2), 50% CO(2)/50% N(2), 20% CO(2)/80% N(2), 100% N(2) and vacuum (2). In an additional experiment, slices of beef semimembransosus muscles were stored for 10 days in 100% CO(2), 100% N(2) and vacuum. Cooking loss of ground beef patties was higher of all CO(2) treatments than non-CO(2) treatments (p<0.05). Storage of raw ground beef in CO(2) caused a concentration dependent decrease in raw meat pH of up to 0.12 units in 100% CO(2). In the beef slices, small CO(2) related fissures and pores were formed in the cooked meat. These changes in pH and microstructure probably contributed to the elevated cooking loss. The hardness of cooked ground beef was not affected by CO(2) exposure (p>0.05). Because CO(2) in concentrations of 20-100% is commonly used in industrial packaging processes for retail meat and meat trimmings, a reduction in cooking yield of 1-3% may have sensory and economic implications.

Prolonged shelf life and reduced drip loss of chicken filets by the use of carbon dioxide emitters and modified atmosphere packaging.

Modified atmosphere packaging containing CO2 is widely used for extending the shelf life of chicken meat. Active packaging by adding CO2 emitter sachets to packages of meat is an alternative to traditional modified atmosphere packaging. The purpose of the study was to investigate the shelf life of chicken filets under different CO2 concentrations at 4°C storage. The inhibition of microbial growth was proportional to the CO2 concentration. Storage in 100% CO2 both with and without a CO2 emitter sachet gave a microbiological shelf-life extension of 7 days compared with 60% CO2. Carnobacterium divergens, Carnobacterium sp., and Lactococcus sp. were the dominating species at the end of the storage period. During storage in pure CO2, the carbon dioxide dissolved in the meat and caused the collapse of the packages. The resulting squeeze of the meat lead to a severe increase in drip loss. The drip loss was reduced profoundly by using the CO2 emitting sachet in the packages. The addition of CO2 emitters can easily be implemented at industrial packaging lines without reduction in production efficiency.

Consumer preferences, internal color and reduction of shigatoxigenic Escherichia coli in cooked hamburgers.

The aim of this study was to relate consumer preferences and preparation of hamburgers to color change, internal temperature and reduction of shigatoxigenic Escherichia coli (STEC) serogroups O157 and the "Big Six" (O26, O45, O103, O111, O121, O145) under two ground beef packaging scenarios: 75% O2 MAP and vacuum. 75% O2 MAP hamburgers cooked to 60 °C core temperature appeared done and showed less internal red color (lower a*) than corresponding vacuum hamburgers. Similar STEC reduction (<4 log10) was found for both hamburgers at core temperatures ≤ 66 °C. In a representative survey (N=1046) most consumers reported to judge hamburger doneness by the color and many preferred undercooked hamburgers. Premature browning of 75% O2 MAP hamburgers represents a risk of foodborne illness, when considering consumers' food handling practices. The risk is even greater if such ground beef is prepared by consumers who prefer undercooked hamburgers and judge doneness by color.

Effects of food ingredients and oxygen exposure on premature browning in cooked beef.

Premature browning (PMB) in the centre of cooked hamburgers and beef loin (M. longissimus dorsi) steaks was assessed visually and instrumentally. Rosemary extract, ascorbic acid, sodium lactate, polyphosphate or lingonberry juice were added to freshly ground beef with predominant oxymyoglobin, and hamburgers were cooked to 62°C. In general, the tested ingredients did not reduce the extent of PMB in hamburgers, but polyphosphate tended to reduce PMB due to increased pH. Control burgers made of vacuum packaged meat with deoxymyoglobin were cooked to 62, 69 and 75°C, and did not express PMB. Beef loins were injected with a solution of sodium lactate, polyphosphate and sodium chloride. Loin steaks were stored under 75% O(2)/25% CO(2) for 5 days and also cooked to 62°C. Injected steaks had less PMB than non-injected controls, but of a low magnitude unlikely to influence the perception of doneness. The study demonstrated that anaerobic packaging is the most efficient measure to avoid PMB in beef.

Determination of the myoglobin states in ground beef using non-invasive reflectance spectrometry and multivariate regression analysis.

Seventy-two samples of ground beef from M. semimembranosus of two 5 and two 1.5year old animals were prepared. Two types of fat tissues from either beef or pork were added to the ground beef. The samples were prepared to contain predominantly deoxymyoglobin (DMb), oxymyoglobin (OMb) and metmyoglobin (MMb) states on surfaces using selected methods based on chemical treatment (for MMb) and oxygen pressure packaging to induce the two other states. Reflectance spectra were measured on ground beef after three storage times. Partial least regression analysis was used to make calibration models of the desired myoglobin states. Validated models using leave-one-sample out cross validation gave, after correction and normalization, prediction errors of about 5%. Long term storage of ground beef was unsuitable for preparing pure MMb states due to gradual reduction of the pigment to DMb, presumably by bacteria.

Use of computed tomography to study raw ham properties and predict salt content and distribution during dry-cured ham production.

Varying salt content in hams of equal brand is a major challenge for Norwegian dry-cured ham producers. This study was thus undertaken to test existing computed tomography (CT) calibration models for salt on entire hams, regarding predictability of salt content at different processing times including final ham and to study salt distribution during processing of dry-cured ham. Twenty-six hams were scanned by computed tomography (CT) 11 times during dry-curing for this purpose. However, previously established calibration models had to be adjusted as they overestimated salt in dry samples. Prediction of ultimate salt content was more accurate approaching the end of the dry-curing process (RMSEP=0.351-0.595% salt). Inclusion of remaining weight loss improved the prediction accuracy in un-dried samples by approximately 0.1% NaCl. The prediction errors were sufficiently low to be of practical interest.

New procedure for improving precision and accuracy of instrumental color measurements of beef.

The surface layers of steaks from bovine M. semimembranosus were prepared to have deoxy- (DMb), oxy- (OMb) and metmyoglobin (MMb) states using either chemicals (CHEM) or oxygen partial pressure packaging (OPP). Ninety-six different meat surface areas were measured in reflectance mode (400-1100 nm) for each preparation method. Reflectance spectra were converted to absorbance (A) and then transformed by Kubelka-Munk transformation (K/S) and/or extended multiplicative scatter correction (EMSC). Transformed spectra of prepared pure states were used to make calibration models of MMb, DMb and OMb using either selected wavelengths (SW) or partial least square (PLS) regression. Finally, the predicted myoglobin states were normalized to ensure that no state was <0 or >1 and the sum of all states equal to 1. Multivariate calibrations (i.e. PLS) outperformed the univariate calibrations (i.e. SW). The OPP method of preparing pure states was clearly best for OMb while the CHEM method was best for preparing MMb on fresh meat surfaces. Both preparation methods needed improvement concerning DMb. The CHEM(K/S) SW and the OPP EMSC(A) PLS methods predicted MMb, DMb and OMb with root-mean-square errors of cross validation (RMSECV) equal to 0.08, 0.16 and 0.18 (range 0-1) and 0.04, 0.04 and 0.04 (range 0-1), respectively. This new reflectance protocol has potential for routine meat color measurements.

Effects of storage atmosphere and heme state on the color and visible reflectance spectra of salmon ( Salmo salar ) fillets.

It has previously been observed that the color of mackerel muscle is dependent on the status of heme as myoglobin and hemoglobin and hence the storage atmosphere. This study gives strong indications of this being the case also in salmon. Three different storage conditions were used to promote the oxidized, reduced, and carbon monoxide (CO) bound forms of heme in salmon and mackerel fillets. Color determination (instrumental color analysis, imaging, and sensory evaluation) and spectroscopic measurements were performed to study how spectral changes corresponded to color variations. Storage in CO significantly increased the redness in mackerel. This was also seen in salmon to such a degree that it was visible over normal levels of salmon carotenoids. Air storage increased the yellowness and reduced the redness in mackerel, but this effect was partly concealed in salmon by the astaxanthin absorption. The spectral differences due to storage condition could be ascribed to the spectral features characterizing heme of different oxidation states and bound to different ligands. The status of heme should therefore always be considered when experiments related to salmon color are performed. The findings could help in the understanding, control, and prediction of color loss in salmon during processing, storage, and transport.

Monitoring secondary structural changes in salted and smoked salmon muscle myofiber proteins by FT-IR microspectroscopy.

Fourier transform infrared (FT-IR) microspectroscopy and light microscopy were used to study changes in the myofibrillar proteins and microstructure in salmon muscle due to dry salting and smoking. Light microscopy showed that the myofibers of the smoked samples were more shrunken and their shape more irregular and edged than for the nonsmoked samples. FT-IR microspectroscopy showed that salting time mostly contributed in the amide I region, revealing that secondary structural changes of proteins were primarily affected by salting. The main variation in the amide II region was caused by smoking. As it is known that smoke components can react with amino acid side chains and that the contribution of the side chain in the amide II region is larger than that in amide I, it is concluded that the observed differences are due to interactions between carbonyl compounds of smoke and amino acid side chains.

Noncontact salt and fat distributional analysis in salted and smoked salmon fillets using X-ray computed tomography and NIR interactance imaging.

To be able to monitor the salting process of cold smoked salmon, a nondestructive imaging technique for salt analysis is required. This experiment showed that X-ray computed tomography (CT) can be used for nondestructive distributional analysis of NaCl in salmon fillets during salting, salt equilibration, and smoking. The combination of three X-ray voltages (80, 110, and 130 kV) gave the best CT calibrations for NaCl, with a prediction error (root mean square error of cross-validation, RMSECV) of 0.40% NaCl and a correlation (R) of 0.92 between predicted values and reference values. Adding fat predictions based on NIR interactance imaging further improved the NaCl prediction performance, giving RMSECV = 0.34% NaCl and R = 0.95. It was also found that NIR interactance imaging alone was able to predict NaCl contents locally in salted salmon fillets with RMSECV = 0.56% and R = 0.86.