Molecular Detection of a Histamine Former, Morganella morganii, in Albacore, Mackerel, Sardine, and a Processing Plant

ABSTRACT: Testing for Morganella morganii , a prolific histamine former, was carried out in fish and processing plant to determine its origin and contamination source using PCR assay coupled with Southern hybridization. M. morganii was mostly found in mackerel and sardines but rarely in albacore. It was most frequently present in the gill followed by the skin but rarely in the intestine and cavity. No M. morganii was found in the processing plant but was detected on the surfaces of conveyer belts and plastic totes during processing. The compiled results indicated that histamine-forming bacteria are endogenous to fish and pointed out the importance of sanitation in the processing plant to prevent cross-contamination.     

Occurrence of Histamine-Forming Bacteria in Albacore and Histamine Accumulation in Muscle at Ambient Temperature

Distribution of histamine‐producing bacteria in fresh albacore and their proliferation in muscle during storage at 25 °C were monitored. Histamine formers constituted a minor portion of the bacterial flora in albacore. Only weak histamine formers were detected in the gill and skin of fresh fish after enrichment. Histamine formers were isolated from the muscles when APC reached >10⁷ CFU/g during storage. Hafnia alvei was most prevalent in both fresh and temperature‐abused fish. The most prolific histamine former, Morganella morganii, was rarely isolated even from spoiled muscles. The prevalence of weak histamine formers resulted in low levels of histamine accumulation in muscle, 67.1 mg/100 g, for 6 d of storage.     

Histamine Formation in Albacore Muscle Analyzed by AOAC and Enzymatic Methods

Histamine formation in fresh albacore was studied. Whole albacore left on deck up to 1 d contained negligible levels of histamine (<0.4 mg/1 00g muscle). When they were abused at ambient temperatures for 1–4 days, 2 of 9 samples showed histamine levels >5 mg/100g. Histamine level was not affected by on-board handling techniques studied, i.e., bleeding and spiking. Enzymatic assay was compared to the AOAC fluorometric method for histamine analysis. Enzymatic results showed a good correlation with those of the AOAC method (r²=0.829). Although the enzymatic method tended to overestimate histamine at levels <1 mg/1 00g, it was rapid, simple, and suitable as a screening method for routine analysis.     

Histamine Formation and Bacterial Spoilage of Albacore Harvested off the U.S. Northwest Coast

Iced and previously frozen albacore were monitored for histamine formation and bacterial growth during storage at 0–37°C. The optimum temperature for histamine formation in albacore tuna (Thunnus alalunga) was 25°C, and whole fish were more susceptible to histamine formation than dressed fish at that temperature. Storage at 25°C resulted in the highest histamine level, 60.4 mg/100g in whole fish stored for 7 days. When albacore were frozen prior to storage, reduced amount of histamine was found at 7.14 mg/100 g after 7 day storage at 25°C, only after decomposition became obvious. No histamine was found in any of the albacore samples stored in ice for 18 days.     

Mercury and Fatty Acids in Canned Tuna, Salmon, and Mackerel

ABSTRACT: Canned tuna ( n = 240), salmon ( n = 16), and mackerel ( n = 16) were analyzed for mercury and fatty acids. Average mercury levels were 188, 45, and 55 ppb, respectively, and below the FDA Action Level of 1000 ppb. "Light tuna in water" contained lower mercury (x = 54 ppb) compared with "white/albacore tuna in water," which contained higher eicosapentaenoic acid/docosahexaenoic acid (EPA/DHA) x= 711 mg/100 g wet tissue). Mercury residues in salmon (x = 45 ppb) and mackerel (x = 55 ppb) were lower than in tuna products, but the EPA/DHA levels were higher (salmon, ×= 1623 mg/100 g wet tissue; mackerel, ×= 851 mg/100 g wet tissue). Information from this study will help women of childbearing age to limit their intake of mercury while obtaining healthy fats from fish.     

Potential Application of the Electronic Nose for Quality Assessment of Salmon Fillets Under Various Storage Conditions

ABSTRACT: The feasibility of using an electronic nose (AromaScan^TM) to assess seafood quality was studied with salmon fillets stored at -20, 4, and 10 °C for 14 d. AromaScan mappings of these fillets were compared to their timerelated changes in microbial counts, histamine contents, and sensory panel evaluations. Fillets stored at 10 °C had respective bacterial counts of 8.90 and 9.06 log¹⁰ CFU/g after 7 and 9 d. The mappings for the 10 °C fillets were separated from those of fresh fillets by Day 3, and continued to separate further as storage time increased. An electronic nose can be used as an assisting instrument to a sensory panel in evaluating seafood quality.     

鲭鱼生物胺生成菌的分离与鉴定

从鲭鱼体内分离7 株生物胺产生菌,其中3 株菌可以产生色胺,4 株菌可以产生2-苯乙胺,4 株菌可以产生腐胺,1 株菌可以产生尸胺,3 株菌可以产生组胺,1 株菌可以产生酪胺。组胺生成量较高的No.1菌株形态学、生理生化分析及菌种鉴定结果表明该菌株极有可能为侵肺巴斯德氏菌,可信度为99.9%。     

介质阻挡放电低温等离子体在鲐鱼杀菌及组胺含量控制中的作用

为探究介质阻挡放电低温等离子体(atmospheric cold plasma,ACP)处理鲐鱼的杀菌效果以及在控制组胺含量中的作用,分别采用ACP直接处理和间接处理两种方式,分析鲐鱼菌落总数的变化,并通过响应面法中心组合设计优化了ACP杀菌的最佳处理电压和时间;在此基础上,探索ACP对鲐鱼贮藏过程中组胺含量以及与组胺产生有关的假单胞菌、肠杆菌、弧菌的影响。结果表明:直接处理对鲐鱼的杀菌效果更优,菌落总数降低率比间接处理高35.88%;最佳处理条件为处理电压59.9 k V、处理时间71.5 s;在优化条件下,鲐鱼菌落总数为1.83(lg(CFU/g)),与预测值1.86(lg(CFU/g))相差不大,所建模型与实际拟合较好;经ACP处理后的鲐鱼在贮藏期(14 d)内,假单胞菌、肠杆菌、弧菌的生长速率明显低于对照组;贮藏第8天时,假单胞菌、肠杆菌、弧菌的菌落数比对照组分别降低25.89%、46.23%和45.23%;组胺含量在贮藏期内增长较慢,第14天时含量为72.34 mg/100 g,低于国标限量。     

Pediococcus pentosaceus L and S Utilization in Fermentation and Storage of Mackerel Sausage

ABSTRACT During 72 h fermentation at 37 °C, rapid increase in lactic acid bacteria count (LAB), dramatic decline in pH and suppression in the growth of contaminating Pseudomonas, Staphylococcus, and Enterobacteriaceae of mackerel minces with Pediococcus pentosaceus strains L and S were observed (p < 0.05). When the mackerel mince was processed into Chinese style sausage with 4% sucrose, no significant changes in pH, growth of LAB, Aerobic Plate Count, and Pseudomonas of the fermented mackerel sausage with Pediococcus pentosaceus strains L and S were obtained (p > 0.05) during 3 wk storage at 4 °C, however, the growth of Enterobacteriaceae and Staphylococcus were effectively suppressed. The residual nitrite in sample decreased during processing and fermentation, and was minimally detected after 72 h fermentation. Suppression of VBN and psychrophilic microflora, and lowering residual nitrite suggest the potential of using these 2 strains in the fermented fish products.     

Solubility of Salmon Myosin as Affected by Conformational Changes at Various Ionic Strengths and pH

The relationship between solubility and conformational changes of salmon ( Oncorhynchus tshawytscha ) myofibrillar proteins at various ionic strengths and pH was investigated using myosin as a model system. Solubility of myosin increased with increased KCl concentration up to 0.5M. Further increasing salt concentration resulted in a gradually reduced solubility. In the absence of salt, myosin was slightly soluble at pH>7 or <4. The increased solubility correlated with the increased surface hydrophobicity and relative sulfhydryl content as well as the decreased α-helicity. At KCl >1.0M, myosin regained its helix structure with a concomitant loss of solubility due to the dominant hydrophobic interaction among nonpolar amino acid residues.     

Chemical Changes After Irradiation and Post-Irradiation Storage in Tilapia and Spanish Mackerel

Influence of gamma irradiation (1.5–10 kGy) and post-irradiation storage up to 20 days at 2 ± 2°C on some chemical criteria of tilapia and Spanish mackerel were studied. Total volatile basic nitrogen formation was lower in irradiated fish than in the unirradiated. Irradiation also caused a larger increase in thiobarbituric acid values which continued gradually during storage. Some fatty acids decreased by irradiation treatments at all doses. Thiamin loss was more severe at higher doses (≥4.5 kGy), whereas riboflavin was not affected. Alpha and gamma tocopherols of tilapia and alpha, beta, gamma, and delta tocopherols, in Spanish mackerel, decreased with increased dose and continued to decrease during 20-day post-irradiation storage.     

Vacuum Packaging, Ascorbic Acid and Frozen Storage Effects on Heme and Nonheme Iron Content of Mackerel

Vacuum packaging and ascorbic acid were tested for their ability to prevent heme iron loss in mackerel (Scomber scombrus). Vacuum packed samples had less heme breakdown than air packed samples at frozen storage temperatures above ?20°C. Ascorbic acid protected the heme at all temperatures when compared to air or vacuum packed samples.     

Determination of trans‐ and cis‐Urocanic Acid in Relation to Histamine,Putrescine, and Cadaverine Contents in Tuna (Auxis Thazard) at Different Storage Temperatures

Scombroid fish poisoning is usually associated with consumption of fish containing high levels of histamine. However, reports indicate that some cases have responded to antihistamine therapy while ingested histamine levels in these cases were low. Potentiation of histamine toxicity by some biogenic amines, and release of endogenous histamine by other compounds such as cis‐urocanic acid (UCA) are some hypotheses that have been put forth to explain this anomaly. Very little is known about the effects of storage conditions on the production of both UCA isomers and biogenic amines in tuna. Thus, the production of trans‐ and cis‐UCA, histamine, putrescine, and cadaverine in tuna during 15 d of storage at 0, 3, and 10 °C and 2 d storage at ambient temperature were monitored. The initial trans‐ and cis‐UCA contents in fresh tuna were 2.90 and 1.47 mg/kg, respectively, whereas the levels of putrescine and cadaverine were less than 2 mg/kg, and histamine was not detected. The highest levels of trans‐ and cis‐UCA were obtained during 15 d storage at 3 °C (23.74 and 21.79 mg/kg, respectively) while the highest concentrations of histamine (2796 mg/kg), putrescine (220.32 mg/kg) and cadaverine (1045.20 mg/kg) were obtained during storage at room temperature, 10 and 10 °C, respectively. Histamine content increased considerably during storage at 10 °C whereas trans‐ and cis‐UCA contents changed slightly. The initial trans‐UCA content decreased during storage at ambient temperature. Thus, unlike histamine, concentrations of trans‐ and cis‐UCA did not result in elevated levels during storage of tuna.     

鲭鱼品质评价及品质变化与组胺含量研究进展

海水鱼类的新鲜度体现了鱼肉的可食用价值,海水鱼中的青皮红肉鱼类含有较高的组氨酸,会因保存不当导致体内组胺含量升高,对消费者健康产生危害。组胺是一种食源性化学危害,易导致过敏人群产生中毒现象。组胺中毒又称为鲭鱼中毒,是组胺引起毛细血管扩张和支气管收缩所致,研究表明鲭科鱼类的组氨酸含量高,组氨酸会在产组胺微生物的组氨酸脱羧酶的作用下产生组胺,判定组胺中毒的最有效的方法是检测鲭鱼体内的组胺含量,低水平的组胺并不会对人体产生危害,组胺摄入量过多会对人体产生危害,组胺已成为评价鲭鱼品质的标准之一。本文主要对鲭鱼品质的感官评定和理化评定(组胺、K值、挥发性盐基氮等)方式进行综述,并对组胺产生的影响因素如微生物、温度、鱼的种类等进行综述,为鲭鱼品质鉴定和组胺含量的控制提供依据。     

Lipid Oxidation Is Inhibited by Isoeugenol Exposure in Chinook Salmon (Oncorhynchus Tshawytscha) Fillets during Storage at 15 °C

ABSTRACT:  The method of harvest for farmed fish and the postharvest tissue metabolism can have a significant effect on the quality and storage stability of the resulting fillets. We have examined the effects of rested harvesting and isoeugenol exposure on tissue oxidation and the loss of tissue antioxidants in fillets of chinook salmon ( Oncorhyncus tshawytscha ) during storage at a normal metabolic temperature of 15 °C. Isoeugenol is a lipid soluble phenolic antioxidant used as an anesthetic in the aquaculture industry (AQUI-S™). Fillets from salmon harvested in rested and exhausted physiological states with and without isoeugenol were prepared and stored in air at 15 °C for 96 h. Exposure to isoeugenol resulted in significantly decreased late-stage lipid peroxidation (TBARS) levels in the fillets during storage regardless of the harvest method. Protein carbonyl concentrations increased 73% in the fillets during storage (from 406 to 703 nmol/g wet weight) and were not affected by the harvest method. Fillet vitamin C concentrations decreased 92% (from 49 to 4 nmol/g wet weight) but were also not affected by the harvest method. Although significant late-stage lipid oxidation was observed with exhausted harvesting, no significant vitamin E loss was observed in any of the fillets during storage. Our results show that rested harvesting of chinook salmon does not affect their oxidative stability immediately postharvest and that isoeugenol can function as an antioxidant in fish fillets as it prevented late-stage lipid oxidation.     

Lipolysis and Lipid Oxidation in Frozen Minced Mackerel as Related to Tg', Molecular Diffusion, and Presence of Gelatin

We determined the sub-zero temperature dependencies (TD) of lipid hydrolysis (LH), lipid oxidation (peroxide value [PV]), and diffusion of ¹⁴C-fructose in minced mackerel (MM) and how these rates are influenced by gelatin (G) and MM Tg'. When 1 % G was added, the rate of LH at ?10°C decreased as compared to that in controls, whereas the rate of PV and TBARS increased (-5, -15 and -20°C). The TD of 14C-fruc-tose diffusion was similar to that of TBARS, but not to those for LH or PV. Just below Tg', the rate decrease for TBARS was abrupt, whereas rate decreases for LH and PV were moderate to small, respectively.     

Histamine, Putrescine and Cadaverine Formation in Spanish Semipreserved Anchovies as Affected by Time/Temperature

We studied the changes in counts of mesophilic, psychrotrophic, entera-bacteria, sulphite-reducing and Vibrio microorganisms in commercial samples of Spanish semipreserved anchovies. The influence of NaCl, oxygen concentration and pH on bacterial growth and histamine, putrescine and cadaverine formation were also studied. Notable histamine formation was detected in samples incubated at 20°C and preserved in olive oil (443.68 ppm-3012.13 ppm). This accumulation was probably caused by the conditions of the product, pH 5–6, relatively low NaCl (< 15%), and permissive temperature (product not refrigerated). Correlation between the microorganisms and histamine formation was not clear. Histamine was produced by too high storage temperatures but not by the ripening process.     

Viability of Two Freeze-dried Strains of Bifidobacterium and of Commercial Preparations at Various Temperatures During Prolonged Storage

ABSTRACT: Viability of bifidobacteria in freeze-dried probiotic products at various temperatures during prolonged storage was assessed. Bifidobacterium longum 1941 and B. longum 536 were freeze-dried and capsules were manufactured. Five commercial probiotic capsule products were also tested. The capsules were stored at -18 °C, 4 °C, and 20 °C. Cell counts were enumerated using MRS-NNLP agar at 37 °C for 72 h under anaerobic conditions at 0, 1, 2, 5, and 8 mo (commercial capsules) and at 0, 1, 2, 5, 8, 11, 14, 17, and 20 mo (laboratory capsules). Storage at 20 °C showed the greatest decline in the viability of bifidobacteria, whereas that at -18 °C showed the least decrease.     

Headspace Gas Chromatography-Mass Spectrometry and Electronic Nose Analysis of Volatile Compounds in Canned Alaska Pink Salmon Having Various Grades of Watermarking

Volatiles in canned pink salmon, produced from different degrees of skin watermarked raw material and stored for 2 and 9 mo, were characterized and compared using static headspace gas chromatography analysis coupled to a mass spectrometer (SHGCMS). Sulfur‐containing compounds comprised 30% to 50% of the total volatiles and tended to decrease with increasing degrees of skin watermarking, and dimethyl sulfide was the most abundant compound of this class of molecules. A few alcohols, aldehydes, ketones, and furans were also identified. Forward stepwise general discriminant analysis (FSGDA) was used to investigate prediction models based on degree of skin watermarking. The 2‐ and 9‐mo models using SHGCMS showed 92.5% and 93.75% correct classifications, respectively. The ability of the Cyranose 320, a hand‐held electronic nose (EN), to differentiate these grades of watermarking in the canned samples was also tested. EN analysis using FSGDA resulted in models with 90% and 92.5% correct classifications for the 2‐ and 9‐mo samples, respectively. Overall, results indicate that the watermarking grades studied are not readily distinguishable from each other by either method of analysis.     

进出口食品中组胺的ELISA快速测定

本文建立了一种进出口食品中组胺的酶联免疫快速测定方法。针对目前国内市场常见的Abraxis、r-Biopharm和Neogen三种试剂盒,进行比较选择最优试剂盒,并对酶联免疫分析定量检测组胺残留试剂盒进行选择性(交叉反应)测试、特异性与检测限测试以及对进出口食品样品组胺的回收率和精密度测试。结果显示,选择r-Biopharm试剂盒来检测样品中的组胺准确性较好,其对N-酰基-组胺交叉性为100%,对N-甲基-组胺、5-羟基吲哚乙酸、咪唑乙酸、L-组氨酸、N-甲基咪唑乙酸及血清素等组胺类似物交叉反应都小于1%,进出口食品中红葡萄酒的检测限(LOD)为250μg/kg,牛奶的LOD为100μg/kg,奶酪的LOD为2.5 mg/kg,鱼粉的LOD为100 mg/kg,样品的平均回收率在86.4%～95.6%,相对标准偏差2.7%～3.9%,经五个试验室的回收验证均具有较好的回收率,经HPLC确证假阳性率≤2.5%,表明酶联免疫分析定量法可快速、准确实现对食品中组胺残留量的快速筛选。