Freshness assessment of cultured sea bream (Sparus aurata) by chemical,physical and sensory methods

The quality changes of cultured sea bream (Sparus aurata) stored in ice for a period of up to 23 days were determined by K and related values, sensory assessment and texture by texturometer. Sensory schemes, based on the Tasmanian Food Research Unit (TFRU) scheme for raw fish and on the Torry scheme for cooked fish were modified to be appropriate for whole cultured sea bream, according to the trained panellists’ perceptions, during the storage period in ice. The TFRU sensory score of fish showed good agreement with K value and texture results throughout the storage period. The limit for acceptability of cultured sea bream stored in ice was about 17–18 days. Generally, K, K_i and G values had good correlation with the degree of freshness and can be used as freshness indicators.     

The effects of gamma-irradiation on the nucleotide degradation compounds in sea bass (Dicentrarchus labrax) stored in ice

The effects of two irradiation doses (2.5 and 5 kGy) on nucleotide breakdown compounds in sea bass stored in ice were investigated. Nucleotide degradation was slower in sea bass irradiated at 2.5 and 5 kGy than untreated samples. Irradiated samples had lower hypoxanthine and inosine content than the control group. Significant differences (p < 0.05) in K and related values were found between control groups and irradiated samples (2.5 and 5 kGy). H and G values showed a good correlation with storage time (r² ? 0.98) while linear regressions of K and Ki ranged from 0.95 and 0.93 to 0.98 and 0.97, respectively. A dose of 5 kGy seemed to be more effective than that of 2.5 kGy to reduce nucleotide breakdown in sea bass. The best linear correlation was obtained from G and H values; thus, they might be used as freshness indicators for non-irradiated and irradiated sea bass.     

白鲢鱼片在冷藏和微冻条件下的鲜度和品质变化

以白鲢鱼为实验对象,通过测定菌落总数、挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、pH值、K值、三甲胺（trimethylamine,TMA）值、2-硫代巴比妥酸（2-thiobarbituric acid,TBA）值等鲜度指标,结合感官评价,以期探究冷藏以及微冻条件下鲢鱼片的品质变化规律。结果表明,在4 ℃冷藏和－2 ℃微冻条件下贮藏的鲢鱼片TVB-N值、TMA值、菌落总数值均随贮藏时间的延长而呈增长趋势;pH值先降低后增高;感官分数值呈降低趋势。综合各项指标变化,4 ℃冷藏条件下鲢鱼片的货架期为6 d,－2 ℃微冻条件下货架期为18 d,与冷藏相比,微冻能明显延长白鲢鱼片的货架期。     

Effects of aluminium foil and cling film on biogenic amines and nucleotide degradation products in gutted sea bream stored at 2±1 °C

Biogenic amines and nucleotide degradation products of sea bream stored in ice, wrapped in aluminium foil (WAF) and in cling film (WCF) at 2±1 °C were investigated by using a rapid HPLC method. Results obtained from this study showed that for household purposes packing fish in different materials has a little effect on the biogenic amines formation and nucleotide degradation products. The highest decrease of IMP content was observed for sea bream in WAF, followed by WCF. INO values showed a fluctuation and remained below the levels of 5.5 μmol/g for all storage conditions. Hx value constantly increased with the storage time during chilled storage. For all of the storage condition, K and Ki value increased linearly with storage time. At the end of the storage period, K, Ki, H and G value reached 60–76%, 65–81%, 30–54% and 89–173%, respectively. Among biogenic amines, (trimetylamine) TMA, putrescine, cadaverine, spermidine, spermine, tryptamine, tyramine, β-phenylalanine and histamine were detected during storage period. TMA and putrescine were observed to increase linearly during storage period. Histamine production was only found at the end of storage period. The highest histamine values for fish wrapped in aluminium foil were 6.4 mg/100 g and fish wrapped in cling film was 4.6 mg/100 g.     

Nucleotide degradation products of gamma‐irradiated sea bream (Sparus aurata) stored in ice

Nucleotide degradation products of irradiated sea bream stored up to 19 days in ice were investigated. Irradiation had significant effect on the nucleotide concentrations in sea bream muscle (P < 0.05). The results showed that the highest value of inosine monophosphate (IMP) was observed in irradiated sea bream at 5 kGy, followed by at 2.5 kGy. Initial inosine (INO) concentration in irradiated sea bream at 5 kGy was 4.26 μmoles g^?1, which reached maximum value of 8.83 μmoles g^?1 when fish completely spoiled (19 days). When the fish reached the limit of acceptability, the mean values of K, Ki, H and G were 86.8%, 90.3%, 59.8% and 213.9% for unirradiated sea bream, 85.2%, 87.8%, 56.8% and 197.8% for irradiated sea bream at 2.5 kGy and 88.4%, 90.9%, 57.8%, 211.5% for irradiated sea bream at 5 kGy, respectively. The results of this study indicated that nucleotide degradation was more rapid in unirradiated sea bream than those irradiated. K, Ki, H and G value in irradiated fish can be used as a freshness index because there is a good linear relationship between values and storage time of fish.     

Comparison of selected methods of assessing freshness quality and remaining storage life of iced gilthead sea bream (Sparus aurata)

Quality changes of whole, iced gilthead sea bream were monitored by sensory evaluation, k₁ value, GR Torrymeter, and bacterial counts. The methods were tested for their suitability to determine freshness quality and remaining storage life in ice. Depending on the measured parameter, post-mortem age of the iced fish could be predicted with an accuracy of ±1.5–3.6 days. Although assessment of cooked fish flavour is the underlying basis for establishing the state of the fish, the quality index method can be more effective for routine freshness evaluations. The k₁ value provides a useful means of monitoring early storage change, resulting primarily from autolytic reactions. Counts of sulphide-producing bacteria can be used to determine the time to rejection, while total counts at 20 °C are only poor measures of freshness quality. The GR Torrymeter offers a unique practical tool for assessing freshness quality and remaining storage life of iced gilthead sea bream.     

Establishment of a Freshness-Evaluating Standard for Chilled Yellow Chicken Meat

There is still no uniform criterion to evaluate the freshness of chilled yellow chicken meat in China. Here, we combined traditional methods, which were sensory evaluation, adenosine triphosphate (ATP) and inosine monophosphate (IMP) contents with a novel technology, electronic nose analysis, to determine the freshness of chilled yellow chicken meat. The contents of ATP and IMP in meat were detected by portable ATP detector and high-performance liquid chromatography (HPLC), respectively. In the first 3 days post-slaughter (dps), sensory evaluation scores were greater than or equal to 4, which indicate freshness. Chicken meat was deteriorated at 6 dps. As chemical indicators, IMP content was higher than ATP content, and both gradually decreased, with fluctuations. The most significant differences appeared at 3–5 days, similar to sensory evaluation results. All indicators above were different between male and female, the same rule was available between breast and thigh. We were able to distinguish the storage time, different body regions, and odors of samples using electronic nose. In the first 3 dps, few changes were found in the G ₀/G eigenvalues for each sensor, which all reached a minimum at 4 dps. In conclusion, the traditional methods and novel technology are fit for evaluating freshness, and the electronic nose is recommended to evaluate the freshness of chicken meat owing to greater speed, ease, and accuracy. To summarize the results of the three tests, we rank meat at or before 3 dps stored at 4 °C as “fresh grade,” from 3 to 5 dps as “second fresh grade,” and 6 dps and later as “non-fresh grade.”     

Establishment of quality predictive models for bighead carp (Aristichthys nobilis) fillets during storage at different temperatures

Quality predictive models were developed to predict the freshness of bighead carp (Aristichthys nobilis) fillets during storage at different temperatures. Quality indices [sensory score, total volatile base nitrogen (TVB‐N), total aerobic counts (TAC) and K value] at ?3, 0, 3, 9 and 15 °C were estimated and kinetically modelled by the Arrhenius equation. The activation energy (E_A) of sensory score, TVB‐N, TAC and K value was 78.17, 75.93, 106.53 and 76.21 kJ mol^?1, and the corresponding rate constants (k₀) were 1.16 × 10¹⁵, 2.60 × 10¹⁴, 4.05 × 10¹⁹ and 1.36 × 10¹⁵. The high regression coefficients (R² > 0.87) indicated the acceptability of the zero‐order reaction for sensory score, TVB‐N, TAC and K value. Relative errors between predicted and observed freshness indicators values of sensory score, TVB‐N, TAC and K value were all below 10% except the values at 6th day of K value, 3rd day and 9th day of TVB‐N. These results indicated that the models based on sensory score, TVB‐N, TAC and K value could effectively predict the freshness indicators of bighead carp fillets at the range of ?3 to 15 °C.     

Evaluation of Shelf Life of Superchilled Cod (Gadus morhua) Fillets and the Influence of Temperature Fluctuations During Storage on Microbial and Chemical Quality Indicators

Quality changes of aerobically packed cod fillets stored under superchilling and abusive temperature conditions were characterized by the growth of specific spoilage organisms (SSO) and the production of microbial metabolites measured by an electronic nose along with traditional sensory and chemical analysis (total volatile basic nitrogen [TVB‐N], pH). A new process based on quick contact freezing and cold air blasting was used to achieve superchilling of fillets before chilled (0.5 °C) or superchilled (‐1.5 °C) storage. Photobacterium phosphoreum dominated under temperature abusive conditions coinciding with high levels of TVB‐N and increased electronic nose responses indicating increased levels of alcohols and aldehydes at sensory rejection. Dominating growth of Pseudomonas spp. in 1 batch was associated with the origin, the catching method, and the cooling conditions during processing. The superchilling process followed by superchilled storage (‐1.5 °C) extended the sensory shelf life of the fillets for at least 3 d compared with traditional process, resulting in a total shelf life of 15 d. High content of TVB‐N was observed in superchilled fillets at sensory rejection. P. phosphoreum counts were lower under superchilling conditions (6.0 to 6.8 log colony‐forming units [CFU]/g), compared with the traditionally processed chilled fillets (7.2 log CFU/g). However, H₂S‐producing bacteria appeared to grow steadily under superchilling conditions reaching counts as high as 7.6 log CFU/g at sensory rejection.     

真空包装鲈鱼片在冷藏与微冻贮藏过程中的新鲜度评价

以淡水鲈鱼为对象,采用真空包装方法,研究鲈鱼片在冷藏（4 ℃）和微冻（－2 ℃）条件下的新鲜度变化情况。以菌落总数、pH值、挥发性盐基氮（total volatile basic nitrogen,TVB-N）值、K值为指标,结合电子鼻对冷藏和微冻鲈鱼片的气味进行检测,并对所获得信息进行主成分分析,综合评价其新鲜度。结果表明,随着贮藏时间的延长,不同温度贮藏的鲈鱼片其菌落总数和K值均呈上升趋势,温度越低,上升越慢;贮藏初期pH值呈先下降后升高的趋势;电子鼻分析结果与菌落总数、K值结果保持一致,能有效区分不同新鲜度的鲈鱼片。综合各指标变化,与冷藏相比,真空包装鲈鱼片微冻贮藏能保持较好新鲜度,货架期更长。     

Biochemical,sensory and microbiological attributes of wild turbot (Scophthalmus maximus), from the Black Sea,during chilled storage

Freshness of wild turbot (Scophtalmus maximus) stored in ice was assessed by chemical, sensory and microbiological methods. The limit for sensory acceptability of wild turbot stored in ice was ∼12–15 days. The quality of turbot decreased on day 15 (B) and they were no longer acceptable on day 19 (C). The TVB-N level showed fluctuations during storage, indicating that TVB-N could not be a good indicator of turbot quality. The release of FFA increased from an initial value of 6.33 (expressed as % of oleic acid) to a final value of 20.6 during the storage period. The initial PV value was 5.60 meq/kg for turbot stored in ice and it started to increase to 21.6 meq/kg on day 12 and then started to decrease to 13.6 meq/kg at the end of storage period. The level of TMA in wild turbot increased sharply from an initial value of 9.36 mg/kg to a final value of 38.9 mg/kg. Linear regressions (r²) obtained from K, K_i, G, P, H and F_r were 0.92, 0.89, 0.99, 0.89, 0.96 and 0.89, respectively, for the wild turbot stored in ice. Turbot maintained high (E) and good quality (A) during the first 12 days of chilled storage when the average K, K_i and P values were ∼78–85%, and H, F_r and G values were ∼45%, 15% and 149%, respectively. Eight biogenic amines were investigated, namely, histamine, putrescine, cadaverine, spermidine, spermine, tryptamine, tyramine, and 2-phenylethylamine, three amines (histamine, tyramine, and tryptamine) were not detected in any of the fish samples during the storage period. As storage time progressed, putrescine and cadaverine became the dominant amines, reaching 22.7, and 16.9 mg/kg, respectively, at 19 days of storage in ice. Total viable counts of whole gutted turbot increased from the initial value of 3.3 log cfu g⁻¹ (day 0) to 7.87 log cfu g⁻¹ (day 19) over the period of storage. If 10⁶ microorganisms/g are considered to be the TVC limit of acceptability, the shelf life of turbot was approximately ∼13–14 days.     

南美白对虾在微冻保藏期间的鲜度变化

以南美白对虾(Penaeus vannamei)为研究对象,在-3℃的微冻条件下对其进行保藏试验。通过高效液相色谱法对不同保藏期间虾肌肉中的腺苷三磷酸(ATP)及其降解的关联产物如肌苷酸(IMP)、肌苷(HxR)和次黄嘌呤(Hx)等进行分析,进而了解鲜度指标K值的变化趋势;另一方面,结合细菌总数和总挥发性盐基氮(TVBN)的测定以及感官评分的结果,对南美白对虾在微冻保藏条件下的鲜度和品质变化的规律进行考察,旨在为其保鲜提供理论依据。结果表明:微冻保藏至18 d时虾肌肉中IMP达到最高值、Hx和HxR仍维持在较低水平,而K值为23.5%,证明微冻保藏至18 d时,南美白对虾仍能保持其原有的风味和鲜度。根据细菌总数及其相关的TVBN测定和感官评分的结果,发现微冻保藏至26 d时,虾肌肉中的细菌总数、TVBN值和感官评分仍未超过腐败临界值;而保藏至26～30 d时,虽然细菌总数和TVBN值尚未超标,但感官上已失去食用价值,据此,可以认为南美白对虾在微冻保藏条件下的保质期约为26 d。     

Effect of ungutting on microbiological, chemical and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice

The effect of ungutting on microbiological, chemical and sensory properties of aquacultured sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax) stored in ice were studied. The total viable mesophilic and psychrophilic bacterial counts increased throughout the storage period of ungutted sea bream and sea bass. Mesophilic counts of ungutted sea bream and sea bass reached 7.39 log cfu/g and 7.26 log cfu/g after 9 days. At the end of the storage period of 14 days; TVB-N, TBA, TMA-N values of ungutted sea bream were determined as 37.5±0.51 mg/100 g, 3.82±0.03 mg MA/kg, 7.73±0.25 mg/100 g, respectively. TVB-N, TBA, TMA-N values of ungutted sea bass were reached 35.4±0.9 mg/100 g, 3.75±0.81 mg MA/kg, 6.94±0.08 mg/100 g on day 14th, respectively. Result of this study indicates that the shelf life of whole ungutted sea bream stored in ice as determined by the overall acceptability sensory scores, chemical quality and microbiological data is 12, 9 and 9 days, respectively. Each chemical, sensory and microbiological results for sea bream showed us that there was a correlation and similarity, and day 9 was the beginning of spoilage. Whole ungutted sea bass stored in ice as chemical results for sea bass showed us that day 7 was the beginning of spoilage and for sea bream day 9 was the beginning of spoilage.     

Application of Electronic Nose for Measuring Total Volatile Basic Nitrogen and Total Viable Counts in Packaged Pork During Refrigerated Storage

The objective of this study was to predict the total viable counts (TVC) and total volatile basic nitrogen (TVB‐N) in pork using an electronic nose (E‐nose), and to assess the freshness of chilled pork during storage using different packaging methods, including pallet packaging (PP), vacuum packaging (VP), and modified atmosphere packaging (MAP, 40% O₂/40% CO₂/20% N₂). Principal component analysis (PCA) was used to analyze the E‐nose signals, and the results showed that the relationships between the freshness of chilled pork and E‐nose signals could be distinguished in the loadings plots, and the freshness of chilled pork could be distributed along 2 first principal components. Multiple linear regression (MLR) was used to correlate TVC and TVB‐N to E‐nose signals. High F and R² values were obtained in the MLR output of TVB‐N (F = 32.1, 21.6, and 24.2 for PP [R² = 0.93], VP [R² = 0.94], and MAP [R² = 0.95], respectively) and TVC (F = 34.2, 46.4, and 7.8 for PP [R² = 0.98], VP [R² = 0.89], and MAP [R² = 0.85], respectively). The results of this study suggest that it is possible to use the E‐nose technology to predict TVB‐N and TVC for assessing the freshness of chilled pork during storage.     

基于电子鼻技术判定冷鲜罗非鱼片品质劣变进程

应用电子鼻采集贮藏过程冷鲜罗非鱼片顶空挥发性气味,同步进行感官评价、微生物和理化分析。结果表明：传感器响应信号随着鱼片气味浓度增大而增大,且对不同新鲜度气味有良好响应。线性判别(LDA)比主成分分析(PCA)更能有效区分鱼片的不同新鲜度、微生物及挥发性盐基氮含量,表明电子鼻可快速检测鱼片的品质劣变进程。通过负荷加载分析和相关分析表明,W2W、W1W、W1S、W2S对区分冷鲜罗非鱼片不同新鲜度的贡献较大,并与感官可接受性、菌落总数和挥发性盐基氮的相关性良好,可作为今后研制鱼用电子鼻系统精选传感器的理论参考。     

Effects of previous frozen storage on chemical, microbiological and sensory changes during chilled storage of Mediterranean hake (Merluccius merluccius) after thawing

The present work aimed to investigate the influence of freezing (−20 °C for 6 months) on the susceptibility of hake to chemical, microbiological and sensory spoilage once thawed and stored in ice. Thus, volatile and biogenic amines, counts of psychrotrophic and mesophilic bacteria, enterobacteria, pseudomonads and Shewanella together with sensory evaluation (of raw and cooked samples) were monitored during 14 days of iced storage in both fresh and frozen-thawed hake (Merluccius merluccius). At the beginning of ice storage, freshness parameters were equivalent in both batches (fresh and frozen-thawed hake), but different behaviour was observed during the iced storage. Overall, levels of volatile and biogenic amines increased much later and then decreased to lower values in frozen-thawed hake in accordance with the delay of microbial development in comparison with fresh hake. On the contrary, sensory spoilage occurred earlier in frozen-thawed hake. Therefore, the usual accepted or regulated limits of acceptability of chemical and microbiological parameters would not be suitable for freshness assessment of frozen-thawed hake.     

Autolytic degradation and microbiological activity in farmed Coho salmon (Oncorhynchus kisutch) during chilled storage

Two deteriorative pathways (autolysis and microbiological activity) were studied in farmed Coho salmon (Oncorhynchus kisutch) for 24 days during chilled storage. These changes were assessed by nucleotide degradation (determination of adenosine 5′-triphosphate and its degradation compounds) and biochemical (pH; content of total volatile base-nitrogen; trimethylamine-nitrogen, TMA-N; histamine) and microbial (total aerobe mesophiles, TAM; coliforms) indices related to bacterial activity. An important nucleotide degradation could be assessed according to the fast inosine 5′-monophosphate formation, followed by degradation into inosine and hypoxanthine; the K value was found to be an accurate tool for the measurement of quality loss throughout the whole experiment. Regarding bacterial activity, contents of TMA-N and histamine and TAM counts assessment showed sharp increases after the end of the microbial lag phase (12–17 days); however, values obtained for histamine content and TAM growth remained below acceptable security limits throughout the whole experiment.     

Comparative studies of quality changes in white and dark muscles from common carp (Cyprinus carpio) during refrigerated (4 °C) storage

Differences between white and dark muscles from common carp (Cyprinus carpio) in sensory assessment, total viable counts (TVC), total volatile basic nitrogen (TVB‐N), pH, electrical conductivity (EC), biogenic amines (BAs), nucleotide degradation products and colours were investigated under air and vacuum conditions during refrigerated (4 °C) storage. Compared with white muscle, dark muscle had a higher lipid content, but lower crude protein and moisture content. TVC, TVB‐N, pH, and L* value were higher in white muscle, while K value and a* value were higher in dark muscle. Under both conditions, white and dark muscles had significant (P < 0.05) differences in tyramine and cadaverine content. Although dark muscle was significantly (P < 0.05) lower in ATP content, it had higher rate of IMP degradation and K value increase. Taking sensory and microbial indexes into consideration, dark muscle appeared to have a longer shelf life than white muscle under both conditions.     

Postmortem changes in yellow grouper (Epinephelus awoara) fillets stored under vacuum packaging at 0 °C

The freshness of yellow grouper (Epinephelus awoara) stored under vacuum-packing at 0 °C was assessed by physicochemical, sensory and microbiological methods. No significant differences were found in pH and thiobarbituric acid (TBA) values during the storage, while TVB-N, TMA-N, HxR, Hx and K values increased significantly with time. The content of IMP was decreased significantly with the storage time. The texture profile, hardness and chewiness were significantly decreased with the time. L∗ values, the values of chroma and hue were all decreased. However, the increased b∗ values were observed. Furthermore, the significant variations and correlations of sensory attributes were shown with the storage time. A regression analysis for total viable counts yielded a shelf life of 26 days. This suggested that the TMA-N, IMP, HxR, Hx, K value, hardness, chewiness, colour, sensory attributes and microbiological counts may be considered suitable indicators for evaluating yellow grouper fillets spoilage during refrigerated storage.     

Quality assessment of wild European eel (Anguilla anguilla) stored in ice

The quality assessment of wild European eel (Anguilla anguilla) stored in ice and in boxes without ice (3 ± 1 °C) was investigated by the sensory analysis, levels of nucleotide breakdown products and biogenic amines for up to 19 days. Sensory analysis was assessed using the Tasmanian Food Research Unit Scheme. K and related values (K_i, G, P, H and F_r) were used as freshness indicators. Linear regressions (r²) obtained from K, K_i, G, P, H and F_r were 0.95, 0.96, 0.83, 0.96, 0.99 and 0.96, respectively, for eel stored in ice whereas, for eel kept in boxes without ice, the values were 0.86, 0.86, 0.96, 0.91, 0.98 and 0.86, respectively. When eel stored in ice and in boxes without ice were considered at the limit of acceptability by assessors at ∼12–14 days and ∼5–7 days, respectively, the average K, K_i and P values were ∼70–85%, H values were ∼60% and F_r values were ∼10% for both storage conditions. The level of histamine exceeded the legal limit (5 mg/100 g fish) in eel stored without ice after 6–7 days and, in ice, after 13–14 days of storage, at which time eels were rejected by the sensory panel. The concentrations of biogenic amines were higher in eel stored in boxes without ice than in eel kept in ice. The levels of histamine in the muscle of eel kept in boxes without ice and in ice increased to the maximum levels of 17.9 mg/100 g on day 12 and 12.6 mg/100 g on day 19, respectively.