Chicken Breast Samples Research Articles

Reduction of Listeria monocytogenes on chicken breasts by combined treatment with UV-C light and bacteriophage ListShield

The aim of this study was to determine the effect of a commercial bacteriophage (ListShield) against Listeria monocytogenes, alone or in combination with UV-C treatment, using artificially inoculated chicken breast. A mixture of three L. monocytogenes strains ATCC 19113, ATCC 19115, and ATCC 13932 was inoculated in chicken breast muscle (approximately 4.5 log CFU/g), followed by UV-C irradiation (at 600, 1200, 1800, and 2400 mWs/cm2), and/or phage treatment. Chicken breast samples were analyzed after 5 min and then stored for 72 h at 4 °C. Phage treatment was seen to reduce bacterial counts by up to 0.84 log units when applied alone, or 2.04 log units in combination with UV-C treatment during storage for 72 h. Additionally, the quality evaluation of chicken breast fillets such as thiobarbituric acid reactive substances (TBARS), pH, surface color as well as other sensory analysis were examined. There were no significant difference (p > 0.05) in color, pH (up to 48 h), TBARS and sensory quality (up to 24 h) due to phage and UV-C treatment (600–2400 mWs/cm2). In conclusion, our results demonstrate that a commercial bacteriophage preparation can be very effective for the control of L. monocytogenes in chicken fillets, either alone or in combination with UV-C treatment.

Study on the abuse of amantadine in tissues of broiler chickens by HPLC-MS/MS.

To evaluate the residual target tissues for better monitoring of amantadine abuse in broiler chickens, 22-day-old commercial Arbor Acres broiler chickens were, respectively, fed with 10, 20, and 40mg/kg of amantadine for five consecutive days. Plasma, breast, and liver tissue samples from the chickens were collected 0, 4, 16, 24, 48, 96, 144, and 312h after amantadine withdrawal. The high-performance liquid chromatography-tandem mass spectrometry method was used to detect the concentrations of amantadine. The highest concentration was found in the chicken liver and it took the longest time for amantadine to vanish by metabolism. In the high-dose group, amantadine residues were still detected 312h after amantadine withdrawal. As the amantadine dose increased, amantadine residues in the chicken liver were more slowly to disappear than in other tissues. Even if approximately the same concentration of amantadine residues was found in chicken breast and plasma samples, it took a shorter time before the residues were eliminated. In the medium- and high-dose groups, the concentrations of amantadine residues in chicken liver samples were substantially higher than those in chicken breast and plasma samples, and it took more time to eliminate them. Therefore, the chicken liver can be used as a target tissue to detect illegal use of amantadine.

Development of a rapid method to quantify Salmonella Typhimurium using a combination of MPN with qPCR and a shortened time incubation

A novel method was developed for the specific quantification of S. Typhimurium using a most-probable-number (MPN) combined with qPCR and a shortened incubation time (MPN-qPCR-SIT). For S. Typhimurium enumeration, dilutions of samples were transferred into three wells on a microtiter plate and the plate was incubated for 4 h. The S. Typhimurium presence in the wells was identified using a qPCR and populations were determined based on an MPN calculation. The R2 between the MPN-qPCR-SIT and conventional MPN exhibited a high level of correlation (0.9335–0.9752), suggesting that the MPN-qPCR-SIT offers a reliable alternative method for S. Typhimurium quantification. Although plating and qPCR were limited in their ability to detect low levels of S. Typhimurium (e.g. 0.18 log MPN/ml), these levels could be successfully detected with the MPN-qPCR-SIT. Chicken breast samples inoculated with S. Typhimurium were incubated at 0, 4, and 24 h and incubated samples were subjected to microbiome analysis. Levels of Salmonella and Enterobacteriaceae increased significantly with incubation time. The obvious benefits of the MPN-qPCR-SIT are: 1) a further confirmation step is not required, 2) the detection limit is as low as conventional MPN, but 3) is more rapid, requiring approximately 7 h to simultaneously complete quantification.

Application of Laser Spectrochemical Analytical Techniques to Follow Up Spoilage of White Meat in Chicken

The overall objective of this paper is to evaluate the potential of laser spectrochemical analytical techniques as rapid, cost-effective, and accurate techniques to detect the onset of spoilage in fresh chicken breast fillets in three consecutive days directly following slaughter day. Samples were periodically examined via laser-induced breakdown spectroscopy (LIBS) and laser-induced fluorescence (LIF). In the case of LIBS, the cyanide (CN) and carbon (C2) molecular spectral emission bands in the LIBS spectra of meat have been taken as indicators of protein content in the chicken breast samples. The ratio of ionic to atomic spectral lines of both magnesium and iron is found to be proportional to the chicken meat tenderness which decreases with storage time. LIF has been also exploited as a simple and fast technique for white meat spoilage detection. There was a clear inverse proportionality between the intensity of the samples’ fluorescence band and the storage period. The obtained spectrochemical results have been validated by measuring the total proteins in the investigated samples using a conventional meat analyzer. This work demonstrates the feasibility of adopting LIBS and LIF techniques in characterization of both fresh and spoiled chicken meat samples.

Antimicrobial effect of an Undaria pinnatifida composite film containing vanillin against Escherichia coli and its application in the packaging of smoked chicken breast

SummaryTo develop a value‐added product, we used the under‐utilised seaweed Undaria pinnatifida as a source material for the fabrication of a biodegradable film by extracting U. pinnatifida protein (UPP). UPP/gelatine composite films with different constituent ratios were prepared. In addition, the UPP/gelatine composite films containing vanillin (0.05%, 0.1% and 0.5%) were prepared as antimicrobial packaging material. To evaluate the utility of the UPP composite film containing 0.5% vanillin as food packaging material, smoked chicken breast samples inoculated with Escherichia coli were packed with the film and stored at 4 °C for 10 days. It was observed that packaging of smoked chicken breast with the UPP composite film containing vanillin decreased the population of the inoculated E. coli by 1.12 log CFU g−1 compared with that in the control sample. Thus, the UPP/gelatine composite film with added vanillin can be utilised as a packaging material for smoked chicken breast.

Kualitas Mikrobiologis Daging Unggas di RPA dan yang Beredar di Pasaran

The aim of this study is to determine the microbiological aspect of meat from slaughterhouses to the consumer and to identify the factors and solutions in handling the contamination of meat. In this study the number of psychrotrophs, E, coli, S. aureus in purchased meat in traditional markets and RPA artisanal, has exceeded reasonable limits set out in the guidelines (1996) CNERNA-CNRS poultry meats. Thus in the samples purchased in these sites were regarded as unacceptable quality. Meanwhile Sixty-six samples of chicken meat collected from retailers, 21 samples of chicken breast without skin, 19 samples of chicken breast with skin, and 26 samples of frozen chicken meat 'ground'. The results of analysis, the percentage of Salmonella spp. 10.60%; S. Auerus amounted to 30.30%; enterobacteria at 24.84%; L. monocytogenes at 3.03%; and clostridium sulfate at 1.5%. It could not been found any contamination of Campylobacter spp. in the samples.

Effects of pulsed electric field (PEF) and oscillating magnetic field (OMF) combination technology on the extension of supercooling for chicken breasts

In this study, a pulsed electric field (PEF) and an oscillating magnetic field (OMF) were used to achieve an extension of a supercooled state within chicken breasts. The specifications of protocol are: (i) PEF with duty cycle sequence of 0.8, 0.5, and 0.2 were applied for 300 s, 120 s, and 90 s, respectively and (ii) during PEF with duty cycle of 0.2, OMF with 1 Hz was applied to vibrate water molecules and inhibit sudden ice nucleation. At the freezer temperature of −7 °C (±0.5), temperature of chicken breast samples under PEF and OMF treatment decreased down to −6.5 °C in a supercooling state during the whole testing period (approximately 12 h); while the control samples were partially frozendown to −6.5 °C. The impacts of the supercooling on microstructure, drip loss, color, texture, pH and lipid oxidation were evaluated as compared with samples stored at refrigeration (4 °C) and at freezing (−7 °C). It was found that the PEF + OMF supercooling was highly effective in the maintenance of original meat qualities without significant physical damages or chemical changes. The supercooling of meat samples using the developed PEF and OMF combination technique led to the advanced designing of innovative food freezers for long term preservation of ‘fresh-like’ foods at subzero temperature.

Improving Displacement Signal-to-Noise Ratio for Low-Signal Radiation Force Elasticity Imaging Using Bayesian Techniques

Radiation force–based elasticity imaging is currently being investigated as a possible diagnostic modality for a number of clinical tasks, including liver fibrosis staging and the characterization of cardiovascular tissue. In this study, we evaluate the relationship between peak displacement magnitude and image quality and propose using a Bayesian estimator to overcome the challenge of obtaining viable data in low displacement signal environments. Displacement data quality were quantified for two common radiation force–based applications, acoustic radiation force impulse imaging, which measures the displacement within the region of excitation, and shear wave elasticity imaging, which measures displacements outside the region of excitation. Performance as a function of peak displacement magnitude for acoustic radiation force impulse imaging was assessed in simulations and lesion phantoms by quantifying signal-to-noise ratio (SNR) and contrast-to-noise ratio for varying peak displacement magnitudes. Overall performance for shear wave elasticity imaging was assessed in ex vivo chicken breast samples by measuring the displacement SNR as a function of distance from the excitation source. The results show that for any given displacement magnitude level, the Bayesian estimator can increase the SNR by approximately 9 dB over normalized cross-correlation and the contrast-to-noise ratio by a factor of two. We conclude from the results that a Bayesian estimator may be useful for increasing data quality in SNR-limited imaging environments.

Poultry marketing controls – Inter-laboratory validation of a method to detect previously frozen chicken breasts by determination of HADH activity

EU poultry marketing legislation requires that poultry be marketed either as fresh (chilled) poultry or as frozen (or quick-frozen) poultry. It is not permitted to market poultry which has been previously frozen as if it were fresh. A robust analytical method that is capable of distinguishing between fresh and previously frozen poultry is therefore required for the enforcement of the legislation. A method to detect whether poultry and other meats have been previously frozen was developed and validated by an earlier collaborative study in 1997. The method is based on measuring the HADH activity of intracellular juice pressed from the test samples. The ratio of the HADH activity of sub-samples tested before and after laboratory freezing is compared to a reference cut-off limit, to determine whether the sample has previously been frozen. In a subsequent study in 2010, improvements were made to the analytical procedure and a revised cut-off limit for chicken of 0.5 was determined. The aim of the current study was to validate the improved analytical procedure and the revised cut-off value for chicken via a collaborative trial with 12 European NRLs and 12 UK OCLs. Each laboratory was asked to analyse 24 chicken breast samples and to use the results to determine their thermal history (chilled or previously frozen) according to the SOP provided. All samples were supplied as chilled blind samples. The results of the study showed inter-laboratory variation between the results obtained for chilled and for previously frozen chicken breasts, however despite this, almost all of the samples were correctly identified and reported in terms of their thermal history. Although some reduction in the analytical variability of the method would be beneficial, the results confirmed the suitability of the method and the revised cut-off limit of 0.5 for the official control of marketing of chicken breasts within the EU.

Contactless remote induction of shear waves in soft tissues using a transcranial magnetic stimulation device

This study presents the first observation of shear waves induced remotely within soft tissues. It was performed through the combination of a transcranial magnetic stimulation device and a permanent magnet. A physical model based on Maxwell and Navier equations was developed. Experiments were performed on a cryogel phantom and a chicken breast sample. Using an ultrafast ultrasound scanner, shear waves of respective amplitudes of 5 and 0.5 μm were observed. Experimental and numerical results were in good agreement. This study constitutes the framework of an alternative shear wave elastography method.

Textural characteristics of fresh and frozen meat chicken and turkey

The purpose of the study is to determine the structural characteristics of the texture of chilled and frozen meat of chickens and turkeys. The object of the study were chicken and turkey breast and legs frozen and refrigerated. Research was carried out using two methods - the analysis of the profile of texture (TPA) and shear Warner-Bratzler (WB). The total chemical composition determined by methods: total protein - Kjeldahl, carbohydrates, fats and total ash down in the relevant known methods. Samples have similar protein containing identical anatomical sites, have some differences in the content of fat and minerals. The results show that the water content of the turkey breasts and legs lower than with the chicken at about equal protein content. According to analysis of variance (ANOVA), a statistical difference was observed between the shear forces of refrigerated and frozen chicken legs, but no significant differences in the results of the shear characteristics of the refrigerated and frozen chicken breast samples were detected. Parameters produced by Warner-Bratzler correlates well with the characteristics of strength, hardness and wiry, obtained by texture profile analysis. The results indicate that the test samples have different textural characteristics depending on the type of meat and the thermal state. Methods of Warner-Bratzler and ATP method in combination with others, may be used to determine in which the thermal state (chilled or frozen) were meat turkey and chicken.

Shrinkage and Density Change of De-Boned Chicken Breast during Deep-Fat Frying

The effects of frying oil temperature (FOT) and time on densities and shrinkage in chicken breast meat during deep-fat frying were investigated. De-boned Chicken breast samples were diced and fried at different FOT (170℃, 180℃, and 190℃) in an industrial fryer for periods varying from 5 to 900 s. Bulk and apparent densities were determined with a fluid displacement pycnometer, and fat analysis was conducted using soxhlet extraction with petroleum ether solvent. The physical structure of chicken meat changed significantly with the frying time and FOT (P 3 in the raw product and decreased to 0.98, 0.95, and 0.93 g/cm3 after 900 s of deep-frying at 170℃, 180℃ and 190℃, respectively. Similarly, apparent density changed from 1.13 to 1.25, 1.24 and 1.22 g/cm3 and moisture loss was linearly correlated with both densities. Volumetric shrinkage was significantly (P < 0.05) affected by the process variables and hence a linear correlation also existed with moisture loss. The rates of shrinkage were 0.013, 0.001, and 0.008/s and occurred rapidly during the first 90s of FOT (170℃, 180℃, and 190℃), respectively and decreased as frying time increased.

Changes in Meat Quality Characteristics of the Sous-vide Cooked Chicken Breast during Refrigerated Storage.

This study was performed to investigate the changes in meat quality characteristics of the sous vide cooked chicken breast during refrigerated storage at 4℃ for 14 d between before and after sous-vide cooking. Cooking loss and shear force were significantly increased, whereas expressible drip was significantly decreased along with reduction in the water holding capacity in both of two groups. Redness of meat juice was significantly (p<0.05) increased during storage, and considerably increased in the refrigerated samples after sous-vide cooked at the 7 to 10 d. The thiobarbituric acid reactive substances (TBARS) was significantly increased and was higher in the refrigerator stored chicken breast samples after sous-vide cooking. The volatile basic nitrogen (VBN) value was significantly increased in both groups, but the VBN value of the stored raw meat sample before sous-vide cooking was increased at an early storage, while the VBN value of the stored sample after sous-vide cooking was increased gradually in this study. Total viable counts and coliform counts were significantly decreased during storage, and coliforms were not detected after 7 d of storage in both groups. Salmonella spp. was not detected during the whole studied period. The outcome of this research can provide preliminary data that could be used to apply for further study of chicken breast using sous-vide cooking method that could be attractive to consumers.

Comprehensive analytical model for CW laser induced heat in turbid media.

In this work, we present a new analytical approach to model continuous wave laser induced temperature in highly homogeneous turbid media. First, the diffusion equation is used to model light transport and a comprehensive solution is derived analytically by obtaining a special Greens' function. Next, the time-dependent bio-heat equation is used to describe the induced heat increase and propagation within the medium. The bio-heat equation is solved analytically utilizing the separation of variables technique. Our theoretical model is successfully validated using numerical simulations and experimental studies with agarose phantoms and ex-vivo chicken breast samples. The encouraging results show that our method can be implemented as a simulation tool to determine important laser parameters that govern the magnitude of temperature rise within homogenous biological tissue or organs.

Cardiac shear-wave elastography using a transesophageal transducer: application to the mapping of thermal lesions in ultrasound transesophageal cardiac ablation

Heart rhythm disorders, such as atrial fibrillation or ventricular tachycardia can be treated by catheter-based thermal ablation. However, clinically available systems based on radio-frequency or cryothermal ablation suffer from limited energy penetration and the lack of lesion’s extent monitoring. An ultrasound-guided transesophageal device has recently successfully been used to perform High-Intensity Focused Ultrasound (HIFU) ablation in targeted regions of the heart in vivo. In this study we investigate the feasibility of a dual therapy and imaging approach on the same transesophageal device. We demonstrate in vivo that quantitative cardiac shear-wave elastography (SWE) can be performed with the device and we show on ex vivo samples that transesophageal SWE can map the extent of the HIFU lesions.First, SWE was validated with the transesophageal endoscope in one sheep in vivo. The stiffness of normal atrial and ventricular tissues has been assessed during the cardiac cycle () and mapped (). Second, HIFU ablation has been performed with the therapy-imaging transesophageal device in ex vivo chicken breast samples (n = 3), then atrial (left, ) and ventricular (left , right ) porcine heart tissues. SWE provided stiffness maps of the tissues before and after ablation. Areas of the lesions were obtained by tissue color change with gross pathology and compared to SWE.During the cardiac cycle stiffness varied from 0.5 ± 0.1 kPa to 6.0 ± 0.3 kPa in the atrium and from 1.3 ± 0.3 kPa to 13.5 ± 9.1 kPa in the ventricles. The thermal lesions were visible on all SWE maps performed after ablation. Shear modulus of the ablated zones increased to 16.3 ± 5.5 kPa (versus 4.4 ± 1.6 kPa before ablation) in the chicken breast, to 30.3 ± 10.3 kPa (versus 12.2 ± 4.3 kPa) in the atria and to 73.8 ± 13.9 kPa (versus 21.2 ± 3.3 kPa) in the ventricles. On gross pathology, the size of the lesions ranged from 0.1 to 1.5 cm2 in the imaging plane area. Elasticity-estimated depths and widths of the lesions differed respectively with a median of 0.2 mm (first quartile Q1: −0.8 mm; third quartile Q3: 2.6 mm) for a mean squared error (MSE) of 5.1 mm2 and a median of 0.2 mm (Q1: −2.7 mm; Q3: 2.7 mm) for a MSE of 11.1 mm2 from gross pathology.We have demonstrated the feasibility of the HIFU thermal ablation monitoring using a dual therapy and imaging transesophageal device. The combination of HIFU, ultrasound imaging and SWE on the same transesophageal system could lead to a new clinical device for a safer and controlled treatment of a wide variety of cardiac arrhythmias.

Bacterial Status of Fresh Marketed Chicken Meat cuts-up

This study was conducted to evaluate bacteriological contamination of fresh marketed chicken cuts-up,and their hazards on public health. A grand total of 100 random samples of chicken breast and thigh(50 of each)were collected from different retail shops for bacteriological examination. The mean valuesof APC, Coliform and staph. aureus counts(log cfu/g) were7.83±0.01, 4.68± 0.02and 6.88 ± 0.01 in theexamined chicken breast samples, respectively, while they were 7.94±0.03, 4.90±0.01,6.79 ± 0.007 and6.98 ± 0.01 in the examined chicken thigh samples, respectively. The incidence of isolated E.coli washigher in the examined thigh samples (88%) than breast samples (70%). Moreover, the serologicallyidentified E. coli were Enteropathogenic E. coli (O55 :H7,and O78), Enterotoxogenic E. coli(O125:H18, O128:H2 and O127:H6), Enteroheamorrhagic E. coli(O26 and O111:H4) andEnteroinvasive E. coli (O124). The public health importance of the isolated microorganisms and therecommended points were discussed.

Quality Characteristics of Marinated Chicken Breast as Influenced by the Methods of Mechanical Processing.

The aim of this study was to investigate the effects of various marination processes on the quality characteristics of chicken breast prepared with chicken feet gelatin and wheat fiber. The chicken feet gelatin was swollen with hydrochloric solution (0.1 N HCl, pH 1.31±0.02) and dehydrated by freeze-drying. The composition (w/w) of the marinade was water (10%), soy sauce (12%), phosphate (0.3%), wheat fiber (1.5%), and chicken feet gelatin (1.5%). Three samples of chicken breast were manufactured with Tumbler (only tumbler), Tenderizer (tenderizer and tumbler), and Injector (injector and tumbler). The water content of the Injector sample was significantly higher than those of the Tumbler and Tenderizer samples (p<0.05). During heating, the lightness of all chicken breasts increased and the redness decreased. The tumbling and cooking yield of the Injector sample were significantly higher than those of the Tumbler and Tenderizer samples (p<0.05). The shear force of the Tenderizer sample was significantly lower than that of the Tumbler and Injector samples (p<0.05). No significant differences, except for color, were observed in the sensory analysis of the samples. Thus, the proper selection of mechanical processing is important to improve the quality characteristics of marinated chicken breast, considering the types of final products.

Efficacy of Various Antimicrobials on Reduction of Salmonella and Campylobacter and Quality Attributes of Ground Chicken Obtained from Poultry Parts Treated in a Postchill Decontamination Tank

Ground chicken is likely to have higher microbiological loads than whole carcasses and parts. Therefore, it is necessary to identify antimicrobials that reduce pathogens and overall microbial loads without negatively impacting meat quality. The objectives of this research were to evaluate the effect of various postchill antimicrobials on reducing Salmonella and Campylobacter, and determine the impact of these treatments on shelf life and quality attributes of ground chicken. Five treatments (0.003% chlorine, 0.07 and 0.1% peracetic acid [PAA], and 0.35 and 0.6% cetylpyridinium chloride [CPC]) were evaluated. Samples (n = 120) of skin-on chicken breast and thigh meat were inoculated with Salmonella Typhimurium (10(8) CFU/ml) and C. jejuni (10(8) CFU/ml). Following a 30-min attachment time, parts were rinsed with either chlorine, PAA, or CPC in a decontamination tank for 23 s. Parts then were ground, samples (25 g) were plated, and reduction of Salmonella Typhimurium and C. jejuni was determined. Noninoculated ground breast and thigh meat were used for sensory and shelf-life determination. Samples (n = 200) for shelf-life determination were collected on days 1, 4, 7, and 10 to estimate spoilage microflora of ground chicken stored at 4°C. Additionally, color measurement and sensory evaluation were conducted on days 1, 4, and 7. Ground chicken treated with 0.07 and 0.1% PAA had the greatest reductions (P ≤ 0.05) in Salmonella and Campylobacter providing approximately a 1.5-log reduction, followed by a 0.8-log reduction after treatment with 0.35 and 0.6% CPC. Chlorine (0.003%) was the least effective treatment (P ≤ 0.05), while treatments with 0.07 and 0.1% PAA also extended the shelf life of ground chicken for 3 days. None of the treatments had negative impact on color or sensory attributes of ground chicken patties during the storage (P ≤ 0.05). Results from this study indicated that using PAA as an antimicrobial agent in a postchill decontamination tank to treat ground poultry parts is effective for the reduction of Salmonella and Campylobacter while maintaining product quality.

Fiber-Based Polarization Diversity Detection for Polarization-Sensitive Optical Coherence Tomography

We present a new fiber-based polarization diversity detection (PDD) scheme for polarization sensitive optical coherence tomography (PSOCT). This implementation uses a new custom miniaturized polarization-maintaining fiber coupler with single mode (SM) fiber inputs and polarization maintaining (PM) fiber outputs. The SM fiber inputs obviate matching the optical lengths of the two orthogonal OCT polarization channels prior to interference while the PM fiber outputs ensure defined orthogonal axes after interference. Advantages of this detection scheme over those with bulk optics PDD include lower cost, easier miniaturization, and more relaxed alignment and handling issues. We incorporate this PDD scheme into a galvanometer-scanned OCT system to demonstrate system calibration and PSOCT imaging of an achromatic quarter-wave plate, fingernail in vivo, and chicken breast, salmon, cow leg, and basa fish muscle samples ex vivo.

Development of a food spoilage indicator for monitoring freshness of skinless chicken breast

A colorimetric mixed-pH dye-based indicator with potential for the development of intelligent packaging, as a “chemical barcode” for real-time monitoring of skinless chicken breast spoilage, is described. Also investigated was the relationship between the numbers of microorganisms and the amount of volatile compounds. This on-package indicator contains two groups of pH-sensitive dyes, one of which is a mixture of bromothymol blue and methyl red, while the other is a mixture of bromothymol blue, bromocresol green and phenol red. Carbon dioxide (CO2) was used as a spoilage metabolite because the degree of spoilage was related to the amount of increased CO2, and which was more than the level of total volatile basic nitrogen (TVB-N) during the storage period. Characteristics of the two groups of indicator solutions were studied, as well as their response to CO2. A kinetic approach was used to correlate the response of the indicator label to the changes in skinless chicken breast spoilage. Color changes, in terms of total color difference of a mixed-pH dye-based indicator, correlated well with CO2 levels of skinless chicken breast. Trials on skinless chicken breast samples have verified that the indicator response correlates with microbial growth patterns, thus enabling real-time monitoring of spoilage either at various constant temperatures or with temperature fluctuation.