Detection of Volatile Organic Compounds Arising from Chicken Breast Filets Under Modified Atmosphere Packaging Using TD-GC/MS

The study aimed to detect volatile organic compounds (VOCs) during spoilage of chicken breast filets under modified atmosphere packaging (MAP, (70% O₂; 30% CO₂)). Storage tests were conducted at 6 °C in a household refrigerator. Measurements were made using untreated chicken breast filets and using filets inoculated with either Pseudomonas fluorescens or Escherichia coli bacteria. The gas space above the sample was adsorbed once a day on Tenax® TA and analyzed using thermal desorption-gas chromatography-mass spectrometry (TD-GC/MS). During storage, 60 volatile organic compounds of hydrocarbons, alcohols, aldehydes, ketones, esters, ethers, and sulfur-containing compounds were detected. It was shown that the presence of most hydrocarbons and aldehydes declined during storage time, whereas most of the alcohols, ketones, sulfur-containing compounds, esters, and ethers increased. Some of these detected VOCs could act as indicators to describe the freshness loss of the product. The best spoilage markers for spoiled chicken breast filets under MAP were 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, 3-hydroxy-2-butanone, ethyl acetate, 2-butanone, and sulfur-containing compounds.     

Rapid Evaluation of Poultry Meat Shelf Life Using PTR-MS

The use of proton transfer reaction mass spectrometry (PTR-MS) for freshness classification of chicken and turkey meat samples was investigated. A number of volatile organic compounds (VOCs) were selected based on the correlation (>?95%) of their concentration during storage at 4 °C over a period of 5 days with the results of the microbial analysis. In order to verify if the selected compounds are not sample-specific, a number of samples sourced from various retailers were classified using the concentration of these compounds in the samples’ volatile fraction as input variables. The classification was performed using the support vector machines (SVM) supervised pattern recognition algorithm. It was concluded that it is possible to evaluate the shelf life of meat samples obtained from the same source based on the results of a prior analysis. The PTR-MS fingerprint approach might supplement the currently used methods of shelf life evaluation of poultry due to the short time and non-destructive nature of measurement and ease of quantitative analysis.     

Fourier Transform Infrared and Raman Spectroscopy Studies of the Time-Dependent Changes in Chicken Meat as a Tool for Recording Spoilage Processes

Time-dependent changes of chicken meat were studied using Fourier transform IR and Raman techniques. Small pieces of intact chicken breast muscle (pectoralis major) were used in the investigations. They were stored in air at 22 °C up to 10 days and their IR and Raman spectra were measured successfully. Analysis of the obtained spectra was performed using a deconvolution of the experimental bands into Lorentz components. All integral intensities of the observed bands were standardized using the statistical R2 coefficient of determination. The R² values were automatically created as the output of the Origin software. The time-dependent changes of the spectra were used for meat spoilage detection. The analytical relationships between the integral intensities of selected bands have been derived indicating an increase of free amino acids content as the main effect of the chicken breast muscle spoilage.     

冰鲜鸡肉腐败微生物检测技术研究进展

作为餐桌上常见食材,鸡肉质地鲜美且富含必需氨基酸,脂肪、胆固醇含量低,日渐成为重要的消费食品之一。冰鲜鸡肉极易受到微生物污染而发生腐败,影响货架期,危害人体健康。本文主要介绍冰鲜鸡肉中优势腐败菌的传统分析检测方法、分子印迹技术、聚合酶链式反应技术、高通量测序技术等研究进展,为冰鲜鸡肉的食品安全和贮藏保鲜提供参考。     

Metabolomic profiling of food matrices: Preliminary identification of potential markers of microbial contamination

The research aimed to generate an early warning system highlighting in real-time bacterial contamination of meat matrices and providing information which could support companies in accepting or rejecting batches. Current microorganisms’ detection methods rely on techniques (plate counting), which provide retrospective values for microbial contamination. The purpose of this research was to evaluate the ability of the headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC/MS) methodologies to detect volatile organic carbons (VOCs), which may be associated to a peculiar microbiological contamination of food. The disposal of fast headspace gas chromatography-mass spectrometry (HS-SPME-GC/MS) able to accurately and rapidly (30 min per sample) detect pathogens in raw meat could replace the traditional and time-consuming (3 to 4 days) standardized microbiological analysis required by regulations. Experiments focused on qualitative and quantitative evaluations of VOCs produced by Salmonella Typhimurium, Campylobacter jejuni, and Staphylococcus aureus in different types of raw meat (beef, pork, chicken). HS-SPME-GC/MS allowed to use smaller sample volumes compared to traditional methods with no sample processing and the potentiality for its application on various food matrices for the detection of a wide variety of pathogens. Data analysis showed the identification of unique VOCs’ profiles being possible markers of meat contamination due to their association to specific pathogens. The identification of VOCs markers in association to selected bacterial pathogens and their metabolites could support the rapid determination of specific meat samples contamination. Further research is required to outline-specific metabolic profiles for each microorganism responsible of meat contamination and prevent false positives.     

The Potential Application of Antimicrobial Silver Polyvinyl Chloride Nanocomposite Films to Extend the Shelf-Life of Chicken Breast Fillets

Silver (Ag) nanoparticles (NPs) were synthesised and characterised, and their antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus cereus, Pseudomonas fluorescens and microflora derived from raw chicken, beef or cooked ham was determined. Polyvinyl chloride (PVC) films or antimicrobial Ag/PVC nanocomposite films were manufactured via a solvent casting method and the mechanical and thermal properties of these materials determined. Manufactured antimicrobial Ag/PVC nanocomposite films were used to wrap chicken breast fillets, followed by modified atmosphere packaging (using conventional laminates and employing a gas mix of 60 % N₂/40 % CO₂), and compared against PVC control films. In general, Gram-negative bacteria were more sensitive to Ag NPs than Gram-positive bacteria and microflora isolated from meat products were more resistant than pure culture bacteria. However, the most sensitive bacteria to Ag NPs were Pseudomonas fluorescens. No significant differences (p?>?0.05) in tensile strength and elongation at break were observed, but glass transition temperatures (T _g) of Ag/PVC nanocomposite films were lower (p?<?0.05) when compared to PVC control films. Results also indicated that antimicrobial Ag/PVC nanocomposite films significantly (p?<?0.05) extended the shelf-life of chicken breast fillets and reduced lipid oxidation of chicken breast fillets compared to PVC-wrapped equivalents. Overall, results indicated that antimicrobial Ag/PVC nanocomposite films can potentially be used as antimicrobial packaging for food packaging applications.     

Detection and identification of selected bacteria, inoculated on chicken breast, using near infrared spectroscopy and chemometrics

Near-infrared transflectance spectra of chicken breast muscle inoculated with Listeria innocua FH 2333, Pseudomonas fluorescens 2088, Pseudomonas putida 49128, Pseudomonas mendocina or Escherichia coli K12 were investigated in order to examine the potential of NIRS to detect microbes on a food matrix. Inoculated samples were stored at 36 °C for 24 h. Two control groups were used in this study, one of fresh uninoculated samples analysed directly after removal of the muscle from the carcass and another of uninoculated chicken stored at 36 °C for 24 h. The findings of this study suggest the NIR spectroscopy can detect and differentiate between inoculated and uninoculated chicken breast muscle. In addition, it can discriminate fresh from non-fresh (in this case samples that are inoculated or not and stored at 36 °C) samples. On the other hand, NIR spectroscopy failed to differentiate between the five different strains used as inoculates for this study. These results suggest that the make up of the microflora of chicken fillets is not the deciding factor in detecting and differentiating chicken fillet samples. Instead, it seems that the total quantity of microflora present in conjunction with the physical changes associated with spoilage and, in particular, the differences in microbial concentration and level of muscle decomposition of inoculated and uninoculated samples, may be responsible for the separations observed in this analysis. This reason could also be the deciding factor for the separations achieved between the fresh samples and the other two groups.     

Quality changes during storage of cooked and sliced meat products measured with PTR-MS and HS-GC–MS

The changes in the VOC composition of industrially produced saveloy were measured with Proton-Transfer-Reaction Mass-Spectrometry (PTR-MS) and HeadSpace Gas chromatography–mass spectrometry (HS-GC–MS) during a six weeks storage period. A decrease in the volatile organic compounds contributing to the fresh aroma of saveloy was the main change observed with both PTR-MS and HS-GC–MS. Samples of four other types of cooked and sliced meat product were measured with PTR-MS in the middle and at the end of the four week shelf-life period. These measurements showed an increase in m/z 69, 71, 87 and 89 for the pork loin and in m/z 61 for the herbal saveloy samples. These ions were assigned to the microbial spoilage markers: acetic acid, 2- and 3-methylbutanol, 2- and 3-methylbutanal, diacetyl and acetoin. Overall, this study shows that PTR-MS has potential for quality control of cooked and sliced meat products.     

Identification and Quantification of Volatile Chemical Spoilage Indexes Associated with Bacterial Growth Dynamics in Aerobically Stored Chicken

Volatile organic compounds (VOCs) as chemical spoilage indexes (CSIs) of raw chicken breast stored aerobically at 4, 10, and 21 °C were identified and quantified using solid phase microextraction (SPME) combined with gas chromatography‐mass spectrometry (GC‐MS). The growth dynamics of total viable count (TVC), psychrotrophs, Pseudomonas spp., lactic acid bacteria (LAB), Brochothrix thermosphacta and H₂S producing bacteria were characterized based on maximum growth rates (μ_max), maximal microbial concentration (N_max) and at the moment of microbial shelf life (S_values), calculated from Gompertz‐fitted growth curves. Pseudomonas spp. was predominant species, while B. thermosphacta was characterized by the highest μ_max. The microbiological and sensory shelf lives were estimated based on TVC, Pseudomonas spp., and B. thermosphacta counts and sensory evaluation, respectively. Among 27 VOCs identified by GC‐MS in spoiled chicken samples, ethanol (EtOH), 1‐butanol‐3‐methyl (1But‐3M), and acetic acid (C₂) achieved the highest Pearson's correlation coefficients of 0.66, 0.61, and 0.59, respectively, with TVC, regardless of storage temperature. Partial least squares (PLS) regression revealed that the synthesis of 1But‐3M and C₂ was most likely induced by the metabolic activity of B. thermosphacta and LAB, while EtOH was attributed to Pseudomonas spp. The increase in concentration of selected volatile spoilage markers (EtOH, 1But‐3M, and C₂) in the headspace over spoiled chicken breast was found to be statistically significant (P < 0.05) with TVC growth. These findings highlight the possibility of analyzing the combination of 3 selected spoilage markers: EtOH, 1But‐3M, and C₂ as rapid evaluation for poultry quality testing using SPME‐GC‐MS.     

质子转移反应质谱在食品挥发性有机物检测分析中的应用

挥发性有机化合物(volatile organic compounds,VOCs)是食品风味的主要组成成分,同时也包含了食品特性的大量信息。直接检测食品释放的VOCs来进行食品科学和技术方面的研究具有便利的优点,已成为食品检测领域的重要研究方向。质子转移反应质谱(proton transfer reaction-mass spectrometry,PTR-MS)作为一种痕量VOCs检测技术,具有灵敏度高、响应时间短、操作简单且样品无需前处理等优点,可以在几秒钟内获得VOCs的绝对浓度,因此能够实时监测食品相关过程中VOCs的变化情况,对食品安全监督、质量控制以及新产品的研发等提供有力帮助。本文首先介绍了PTR-MS的工作原理、基本结构及发展现状,然后按照PTR-MS的全谱图扫描检测和VOCs实时监测两种检测方式详细总结了其在食品领域的应用和研究现状,并对其发展前景做出了展望。     

Evaluation of the Spoilage of Raw Chicken Breast Fillets Using Fourier Transform Infrared Spectroscopy in Tandem with Chemometrics

The aim of this work was to evaluate the potential of Fourier transform infrared (FTIR) spectroscopy as a rapid and accurate technique to detect and predict the onset of spoilage in fresh chicken breast fillets stored at 3, 8, and 30 °C. Chicken breasts were excised from carcasses at 6 h post-mortem; cut in fillets; packed in air; stored at 3, 8, and 30?ºC; and periodically examined for FTIR, pH, microbiological analysis, and sensory assessment of freshness. Partial least squares regression allowed estimations of total viable counts (TVC), lactic acid bacteria (LAB), Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae counts and pH, based on FTIR spectral data. Analysis of an external set of samples allowed the evaluation of the predictability of the method. The correlation coefficients (R²) for prediction were 0.798, 0.832, 0.789, 0.810, 0.857, and 0.880, and the room mean square error of prediction were 0.789, 0.658, 0.715, 0.701, 0.756 log cfu g^?1 and 0.479 for TVC, LAB, Pseudomonas spp., B. thermosphacta, Enterobacteriaceae, and pH, respectively. The spectroscopic variables that can be linked and used by the models to predict the spoilage/freshness of the samples, pH, and microbial counts were the absorbency values of 375 wave numbers from 1,700 to 950 cm^?1. A principal component analysis led to the conclusion that the wave numbers that ranges from 1,408 to 1,370 cm^?1 and from 1,320 to 1,305 cm^?1 are strongly connected to changes during spoilage. These wave numbers are linked to amides and amines and may be considered potential wave numbers associated with the biochemical changes during spoilage. Discriminant analysis of spectral data was successfully applied to support sensory data and to accurately bound samples freshness. According to the results presented, it is possible to conclude that FTIR spectroscopy can be used as a reliable, accurate, and fast method for real time freshness evaluation of chicken breast fillets during storage.     

Evaluation of Freshness in Determination of Volatile Organic Compounds Released from Pork by HS-SPME-GC-MS

Freshness is an important parameter for evaluating the quality of pork, which has strong correlation with the characteristic volatile organic compounds (VOCs) in meat. In this study, the pork was stored at a refrigerator, and the VOCs were determined by using headspace solid-phase microextraction–gas chromatography–mass spectrometry (HS-SPME-GC-MS). The results of HS-SPME-GC-MS measurements were compared to total viable counts, total volatile basic nitrogen, and pH value to determine possible volatile spoilage markers. The pork was stored in a refrigerator up to 5 days at 4 °C and 466 days at ?18 °C. The pork became stale at 4 °C when the 2,3-butanedione, 3-methyl butyraldehyde, 3-methyl-1-butanol, and acetoin increased to 26.44, 13.72, 71.56, and 340.48 μg/L, respectively. These substances can be seen as characteristic compounds of stale pork. The VOCs such as ethyl acetate, ethyl propionate, ethyl butyrate, and ethyl hexanoate had negative correlation (P?<?0.05) with the pork freshness, which can be potentially considered as characteristic compounds of fresh pork. Therefore, the selected VOCs can be used as indicators for evaluation of pork freshness, and VOCs could be potentially applied in the development of intelligent refrigerators and refrigerated storehouse.     

Possible role of volatile amines as quality-indicating metabolites in modified atmosphere-packaged chicken fillets: Correlation with microbiological and sensory attributes

The present work evaluated the possible role of volatile amines as indicator(s) of poultry meat spoilage. Fresh chicken meat (breast fillet) was packaged in four different atmospheres: air (A), vacuum (VP) and two modified atmospheres (MAs), namely M1, 30%/65%/5% (CO₂/N₂/O₂) and M2, 65%/30%/5% (CO₂/N₂/O₂). All chicken samples were kept under refrigeration (4 ± 0.5 °C) for a period of 15 days. Of the four treatments, the VP and M1 and M2 gas mixtures were the most effective for delaying the development of aerobic spoilage microbial flora. Pseudomonas spp. in chicken samples stored under M2 gas mixture and VP were significantly lower than all the other samples after 15 days of storage. Of the remaining bacterial species examined, lactic acid bacteria (LAB), Brochothrix thermosphacta, were dominant in the microbial association of both aerobically- and MA-packaged chicken, while yeasts contributed to a much lesser extent in the final microbial flora of chicken meat. On the basis of microbiological data (TVC), shelf-life extensions of 2, 4 and 9–10 days were achieved by VP and M1 and M2 gas mixtures. Results of the present work showed that the limit of sensory acceptability (a score of 6) was reached for the aerobically, vacuum-packaged and M1 gas mixture chicken samples approximately on days 6–7 and 9–10, respectively. Based on sensory (taste) analysis and with regard to chicken spoilage and freshness, TMA-N and TVB-N limit values of acceptability, namely 10.0 mg N/100 g and 40 mg N/100 g for chicken samples stored in air, may be proposed as the upper limit values for spoilage initiation of fresh chicken meat stored aerobically. Interestingly, the M2 gas mixture sample did not reach these limit values throughout the 15 day storage period. The formation of volatile amines during chill storage of chicken meat, under the packaging conditions examined in the present study, seemed to be in good agreement with the increase in microbiological count (TVC) and sensory taste score except for the M2 gas mixture.     

Detection of poultry spoilage markers from headspace analysis with cryoadsorption on a short alumina PLOT column

A rapid and simple diagnostic tool for the early detection of meat spoilage would be invaluable to ensure meat quality during production, distribution, and retail. Recently, we developed an improved purge and trap method for sampling low volatility, as well as volatile, compounds by applying low temperature collection on short alumina-coated porous layer open tubular (PLOT) columns. This method was applied to the analysis of both fresh and spoiled poultry to identify marker compounds that could be used as indicators for poultry spoilage. Samples of chicken breast were crimp-sealed in individual autosampler vials and maintained at 25 °C for either a day or 2 weeks. Two weeks were sufficient to ensure severe spoilage. The headspace was sampled by cryoadsorption for 10, 20, or 30 min; and the analytes were then separated, identified, and quantified with gas chromatography and mass spectrometry. Six potential markers for poultry spoilage were identified in the headspace of spoiled chicken: dimethyl disulphide; dimethyl trisulphide; phenyl sulphide; methyl thiolacetate; allyl methyl sulphide; and 2,4,6-trimethylpyridine. Additionally, isophorone was detected in the headspace of both the fresh and the spoiled chicken; its origin is unknown but is suspected to come from the packaging. The applicability of this method to detect chicken spoilage in a commercial setting was tested by sampling the air above spoiled chicken breast that was maintained in its original retail packaging, as obtained direct from a commercial vendor, for 2 weeks at 25 °C. Sampling was done via a modified, room-temperature approach with an activated PLOT column and a motorised pipette filler/dispenser. Five of the above compounds were also identified with this approach: dimethyl disulphide; dimethyl trisulphide; phenyl sulphide; 2,4,6-trimethylpyridine; and isophorone.     

Application of Neural Networks and Meta-Learners to Recognize Beef from OTM Cattle by Using Volatile Organic Compounds

Cattle with age under 30 months (UTM) are usually slaughtered for human consumption to be not associated of the disease called mad cow. Though the age of the animal can generally be estimated by dentition, this method cannot be applied to a piece of meat from which the teeth have been removed. Since volatile organic compounds have been used to analyze food samples, this technique was used to recognize meat obtained from cattle aged over 30 months (OTM). The monitoring of the volatile organic compounds (VOCs) released by UTM and OTM beef were done by using gas chromatography. A dataset with more than 500 chromatograms (each one with 17 VOCs fully identified) from fresh meat, refrigerated meat and vacuum-packaged meat was used to develop a classifier by using neural networks. Neural networks were trained with backpropagation, and then further optimized by using meta-learners. Optimal configuration of the neural networks allowed discriminating between beef obtained from OTM or UTM cattle with accuracy close to 90 %. Results contrast favorably with more traditional statistical methods such as linear discriminant analysis (LDA), soft independent modeling of class analogies (SIMCA), partial least square discriminate analysis (PLS-DA), and support vector machines (SVM). In conclusion, VOCs can be used as a fingerprint to recognize OTM beef from a pool of meat obtained indistinctly from fresh meat, refrigerated, or vacuum-packaged meat.     

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 β‐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.     

Applications of Hyperspectral Imaging in Chicken Meat Safety and Quality Detection and Evaluation: A Review

Currently, the issue of food safety and quality is a great public concern. In order to satisfy the demands of consumers and obtain superior food qualities, non-destructive and fast methods are required for quality evaluation. As one of these methods, hyperspectral imaging (HSI) technique has emerged as a smart and promising analytical tool for quality evaluation purposes and has attracted much interest in non-destructive analysis of different food products. With the main advantage of combining both spectroscopy technique and imaging technique, HSI technique shows a convinced attitude to detect and evaluate chicken meat quality objectively. Moreover, developing a quality evaluation system based on HSI technology would bring economic benefits to the chicken meat industry. Therefore, in recent years, many studies have been conducted on using HSI technology for the safety and quality detection and evaluation of chicken meat. The aim of this review is thus to give a detailed overview about HSI and focus on the recently developed methods exerted in HSI technology developed for microbiological spoilage detection and quality classification of chicken meat. Moreover, the usefulness of HSI technique for detecting fecal contamination and bone fragments of chicken carcasses are presented. Finally, some viewpoints on its future research and applicability in the modern poultry industry are proposed.     

Comparison of Two Volatile Sampling Techniques Based on Different Loading Factors in Determination of Volatile Organic Compounds Released from Spoiled Raw Beef

Evaluation of meat volatiles is an increasing concern due to the development studies for spoilage sensors in order to inform consumers if meat spoiled or not. Since the reliable measuring of volatiles in headspace is important for designing a sensor, preconcentration techniques for meat matrix should be investigated. This study describes the effect of three sample amounts: total volume ratio (loading factors) with 0.025, 0.05, and 0.10 kg/L applied in two preconcentration sampling techniques: solid phase microextraction (SPME) and gas flushing on Tenax with thermal desorption to explain the interactions and relationship between sample amount and extracted analytes for spoiled beef striploin. The ratio of the sample amount of beef meat in the chamber and the total volume of chamber is called as “loading factor”. The results showed that the volatile profiles did not vary significantly, but the levels were affected with the extraction technique and loading factor. The volatile organic compounds identified in the early stages of meat spoilage include alcohols, aldehydes, ketones, esters, and amine compounds. While amines were measured only with Tenax, ethyl acetate was detected only with SPME. The total peak area of volatiles with Tenax (~390 × 10^?6 AU at 0.05 kg/L) were higher than SPME sampling (~290 × 10^?6 AU at 0.05 kg/L) in each loading factor. Although optimum loading factor depended on the type of volatile, 0.05 kg/L loading factor resulted the most efficient extraction by the two preconcentration techniques for most of the volatiles generally.     

Development of a pH indicator composed of high moisture-absorbing materials for real-time monitoring of chicken breast freshness

A colorimetric bromocresol purple dye-based pH-responsive indicator was developed to monitor the quality of chicken breast meat by direct surface contact. To prevent direct contact of the dye with the chicken breast and to improve its color change sensitivity, it was immobilized with polyvinyl alcohol and a high-absorbance material. The color of the pH indicator changes from yellow to blue and finally purple to indicate spoilage, which can be easily detected by the naked eye. The asprepared pH indicator exhibited good response to pH changes on the surface of chicken breast meat, and no migration of the dye from the indicator onto the surface of the chicken was observed. This pH indicator exhibits excellent feasibility for real-time, direct-contact monitoring of the freshness and quality of various foods.     

腐败希瓦氏菌及其与蜂房哈夫尼亚菌共培养对冷藏大菱鲆的致腐能力

本研究将腐败希瓦氏菌SP22及其与蜂房哈夫尼亚菌Ha-01混合菌液分别接种到大菱鲆无菌鱼块中,以微生 物及理化参数（菌落总数、挥发性盐基总氮（total volatile basic nitrogen,TVB-N）值、K值、Ca2＋-ATPase活力及肌 肉蛋白显微结构）为指标,探讨腐败希瓦氏菌SP22及其与蜂房哈夫尼亚菌Ha-01共培养对冷藏大菱鲆的致腐能力。 结果表明：在4 ℃冷藏过程中,随着贮藏时间的延长,各接菌组鱼块的菌落总数、TVB-N值及K值上升速度明显 高于空白对照组,且接种混合菌组的上升速度高于接种单菌组;接菌组的Ca2＋-ATPase活力下降速度明显高于空 白对照组,其中接种混合菌组下降最快;利用扫描电子显微镜可观察到接菌组肌肉蛋白质变性降解速度明显快于 空白对照组。腐败希瓦氏菌SP22能够造成大菱鲆的腐败变质,且其与蜂房哈夫尼亚菌Ha-01共培养时能够产生明 显的致腐效果。