电导法快速检测淡水鱼新鲜度的方法研究

水产品新鲜度检测的常规方法是测定挥发性盐基氮ＴＶＢＮ、ｋ值和细菌总数等。ＴＶＢＮ是判定水产品新鲜度的国家指标。但是这些方法操作繁琐、费时。基于电化学理论，本文研究了用电导法快速检测淡水鱼新鲜度的方法。实验以白链为样品，研究其电导率与ＴＶＢＮ的相关性。结果表明，电导率与ＴＶＢＮ有很好的线性相关性。相关系数ｒ＝０．９９。说明可以用电导率作为判定其新鲜度的指标。     

牛肉新鲜度检测与指标分析

本文在测定市场牛肉的新鲜度卫生指标（ＴＶＢ－Ｎ、菌落总数、ｐＨ）的基础上，利用统计方法分析了主要指标间的相关性，结果表明未包装的市场牛肉的ＴＶＢ－Ｎ和ＴＮＢＣ两指标间有显著性相关关系。利用ＴＶＢ－Ｎ、菌落总数、ｐＨ、水分含量结合感官评定，能准确地检测牛肉的新鲜度。而不同处理的小包装牛肉，ＴＶＢ－Ｎ和菌落总数间的相关性不显著，认为应研究建立针对小包装牛肉的新鲜度卫生指标及标准。     

电化学法快速检测肉品新鲜度之研究

肉新鲜度检测的常规方法是挥发基盐基氮ＴＶＢ－Ｎ测定和细菌总数检测，ＴＶＢ－Ｎ是判定肉品新鲜度的国家指标。但这些方法实验操作比较繁琐，试剂配制的条件要求较高且费用很大。基于电化学的理论，本文提出一种新的快速检测肉品新鲜度的－－电导法。实验表明，肉品浸出液的电导率与其ＴＶＢ－Ｎ、细菌总数及其它综合制定指标有良好的相关性。因此，电导可以代替这些指标来判定肉品的新鲜度。     

电流型酶电极检测鱼具类新鲜度的方法研究

提出一种新的快速而又准确的检测鱼具类新鲜度的方法-电流型酶电极法。实验表明,在ＴＶＢ-Ｎ和次黄嘌呤（ＨＸ）的量之间有良好的相关性。ＴＶＢ-Ｎ是目前常规的国家检测标准因此,可将次黄嘌呤的量作为指标来判别鱼具类的新鲜度,新型的生物传感器快速检测很快可以取代繁杂的ＴＶＢ-Ｎ测定及细菌总数检测方法。     

单冻带鱼保鲜技术研究

采用不同浸渍液浸渍带鱼段，冻结合冷藏于－１８℃环境中，定期测定其Ｋ值，ＴＶＢ－Ｎ值和ＴＢＡ值。结果表明，５种保鲜剂配方均有保鲜作用，尤以 多酚与植酸的复合保鲜剂保鲜效果最佳。经８个月苎藏ＴＢＡ高峰才到达，此时的Ｋ值及ＴＶＢ－Ｎ值仅为３０．９％和１４．２ｍｇ／１００ｇ。     

乳酸发酵对中式香肠贮藏性的影响

本课题对接种乳酸菌的中式香肠贮藏期间乳酸菌数、活菌总数、ＴＶＢ－Ｎ值及ＴＢＡ值的变化进行了研究。结果表明：试验组乳酸菌数占总菌数的比例随着贮藏期的延长急剧增大，一个月即达９０％以上。而对照组只是缓慢增加，到贮藏结束时只达５０％左右。试验组的ＴＶＢ－Ｎ值和ＴＢＡ值贮藏期间始终以缓慢的速度递增，试验结束时分别达到６７ｍｇ／ｋｇ和０．７１ｍｇ／ｋｇ。而对照组的ＴＶＢ－Ｎ和ＴＢＡ值分别在后两个月和前一个月以较快速度增加，最高值分别为１５８ｍｇ／ｋｇ和０．８２ｍｇ／ｋｇ。     

台湾省烟草病毒病害简要综述

台湾省烟草病毒病害简要综述＊陈瑞泰为了解台湾省烟草病害发生种类和研究工作情况，查阅了１９６４～１９９３年《烟草文摘（ＴＯＢＡＣＣＯＡＢＳＴＲＡＣＴ）》，现综合简介如下。１烟草脉带花叶病毒病（ＴＶＢＭＶ）１．１症状ＴＶＢＭＶ侵染的烟叶，沿叶脉呈窄狭、深...     

冷却肉质量的研究

在冷却肉生产企业的实际加工流水线上及销售环节中选取五个时间点进行随机取样,对冷却肉的ｐＨ、持水力（ＷＨＣ）、嫩度（切断力）、鲜味（ＩＭＰ含量）、新鲜度（挥发性盐基氮ＴＶＢ－Ｎ、Ｋ 值）等理化指标及微生物指标（细菌总数）进行测定。并对冷却肉的感官作定性描述。实验结果表明,超市中放置第三天的冷却肉处于僵直后期,其新鲜度符合国家规定的一级鲜猪肉标准;与僵直初期相比,嫩度变化不十分明显,但鲜味物质增加,风味有较大改善。     

克氧灵在火腿保藏方面的应用研究

火腿易氧化与霉变，克氧灵是一种新型的复合抗氧防霉剂，将它用于火腿的保藏并与真空、气调包装工艺结合或对照，测定贮藏过程中火腿的ＴＶＢＮ（挥发性盐基氮）、ＰＯＶ（过氧化值）、Ａｗ（水份活度）等理化指标并进行感官评定。实验结果表明，贮藏６６天时对照组ＴＶＢＮ（ｍｇＮ／１００ｇ样品）上升了５３．１，ＰＯＶ（ｍｅｑ．ｋｇ－１样品）上升了２．４２，喷克氧灵组的ＴＶＢＮ仅上升了１８．６，ＰＯＶ升高了０．７６，而喷克氧灵真空装的ＴＶＢＮ仅升高了８．５，ＰＯＶ升高了０．１２。说明克氧灵有很强的抗火腿氧化能力，并能较好的防止火腿发霉变质。当与真空包装结合时，不仅提高了抗氧化防变质效果而且具有明显的护色作用保持产品色泽鲜红。     

TEAM实验及应用

ＴＥＡＭ实验及应用郑秀歧，魏新章，郭顺一、关于ＴＥＡＭ实验八十年代以来，澳大利亚羊毛研究开发理事会通过了一项关于羊毛附加测试评定（ＴＲＩＡＬＳＥＶＥＡＬＵＡＴＩＮＧＡＤＤＩＴＩＯＮＡＬＭＥＲＳＵＲＥＭＥＮＴ）项目的计划，简称“ＴＥＡＭ”项目。以使毛丛...     

鱼类腐败菌腐败能力测定方法

通过分析比较接种腐败菌的大黄鱼无菌鱼块和灭菌鱼汁,在贮藏中感官、挥发性盐基氮(total volatile base nitrogen,TVBN)、三甲胺(trimethylamine,TMA)和腐败菌的变化,以及腐败菌生长动力学参数和腐败代谢产物的产量因子(YTVBN/CFU 和YTMA/CFU),探讨无菌鱼块和灭菌鱼汁两种腐败能力的测定方法。结果表明：接种腐败希瓦氏菌的无菌鱼块和灭菌鱼汁的货架期分别为162h 和132h,此时的TVBN 含量分别为32.16mg/100g 和29.64mg/100mL,TMA含量为9.31mg/100g 和0.99mg/100mL,腐败希瓦氏菌菌数为8.67 lg(CFU/g)和8.56 lg(CFU/mL),产量因子YTVBN/CFU为2.58 × 10-10mg TVBN/CFU 和1.98 × 10-10mL TVBN/CFU,产量因子YTMA/CFU 为2.12 × 10-10mg TMA/CFU 和1.27× 10-11mL TMA/CFU。TMA 作为接种鱼汁的理化指标是不可靠的,而TVBN 可以作为接种鱼汁的理化指标。接种腐败希瓦氏菌的无菌鱼块和灭菌鱼汁产量因子YTVBN/CFU 的相对误差为23.64%,因此灭菌鱼汁作为腐败菌腐败能力测定方法具有一定的可靠性。     

Biogenic and volatile amine-related qualities of three popular fish species sold at Kuwait fish markets

Three fish species commonly consumed in Kuwait were studied for their total volatile base nitrogen (TVBN) and biogenic amine composition during normal commercial activities at the fish markets. Samples of the fish species Zubaidi or silver pomfret (Pampus argenteus), Hammour or orange–spotted grouper (Epinephelus coioides), and Negrule or grunt (Pomadasys kaakan) were analyzed using steam distillation and high performance liquid chromatography (HPLC) procedures. Fish samples collected in the morning had lower levels of TVBN, ranging from 25.9 mg/100 g to 30.2 mg/100 g compared with the range of 31.2 mg/100 g to 40.9 mg/100 g for samples collected in the evening. Among all three fish species, Zubaidi (Pampus argenteus) showed the lowest TVBN content while Negrule (Pomadasys kaakan) had the highest. Biogenic amine levels were also low in the fish species. The data suggest that fish handling practices at the fish markets in Kuwait do not result in significant abuse of fish temperatures, and that the amounts of volatile and biogenic amines produced during normal activities did not rise to levels indicating fish decomposition.     

Mathematical models for the trimethylamine (TMA) formation on packed cod fish fillets at different temperatures

The microbial formation of trimethylamine (TMA) can be used as a quality indicator compound to predict the freshness of fish during its shelf life. In a supply chain with fluctuating temperatures, mathematical models will be valuable tools to simulate this formation as a function of temperature and time. These models are essential to link sensor data on the formation of TMA to the actual freshness of fish. Existing models for the formation of TMA in fish needed improvements and secondary models for the effect of temperature on the formation of TMA are lacking in the literature. Three different approaches were evaluated on their ability to simulate the experimental observed TMA formation at 4 different temperatures (0, 5, 10 and 15 °C). In the first approach the existing models were improved and the temperature effect was modelled by an empirical model using four parameters. This model is able to simulate the TMA formation at static temperatures. Since TMA is produced on fresh cod fillets by the micro-organisms Shewanella putrefaciens and Photobacterium phosphoreum the microbial Baranyi–Roberts model was initially used for modelling the TMA formation, but this model was found to be too complex (too many correlated parameters that could not be estimated). In the third approach it was seen that a simplified Baranyi–Roberts model with only three parameters could be used to predict the TMA formation with equal accuracy. The influence of the temperature on the parameter μ_max was modelled using the extended square root model of Ratkowsky and the differences in TMA formation profiles of different batches could be described by the batch specific parameter N₀ representing the initial quality. The presented dynamic model is valuable in predicting the formation of TMA in a fresh fish supply chain with dynamic temperatures. This model has the potential to be used to link sensor data of TMA in the headspace to the actual freshness status of the fish.     

CHANGES IN FRESHNESS OF CHILIPEPPER ROCKFISH (SEBASTES GOODEI) DURING STORAGE AS MEASURED BY CHEMICAL SENSORS AND BIOSENSORS

ABSTRACT Trimethylamine (TMA) and ammonia contents in Chilipepper rockfishes were determined by ion specific electrodes, as a late indicator of fish freshness. After 9 days of storage in ice, TMA contents significantly increased, indicating that bacterial spoilage was in progress. The pattern of changes in ammonia contents was similar to that of TMA. Determination of ATP degradation products in Chilipepper rockfish by HPLC showed that AMP and hypoxanthine levels were low and did not change much during storage. The concentration of IMP initially increased and then continuously decreased as inosine accumulated. Only trace amounts of hypoxanthine were detected in rockfish tissues. Chilipepper rockfish appears to differ from other Sebastes species in that ATP degradation results in inosine accumulation rather than hypoxanthine.     

Atlantic Mackerel (Scomber scombrus, L.): Shelf Life in Ice

Spoilage pattern of ice stored Atlantic Mackerel was monitored by determining trimethylamine (TMA), total aerobic plate counts and histamine levels. Hypoxanthine accumulation was used as the freshness index, coupled with sensory evaluation of fresh fish. These tests indicated that mackerel can be stored fresh in ice up to 9 days, after which the accumulation of bacteria, TMA and histamine was rapid. Hypoxanthine levels increased between 0–10 days and appeared to increase at a slightly slower rate until day 16, then it declined.     

Determination of the quality of fish by measuring trimethylamine oxide reduction

The sanitary quality of perishable food products can be evaluated through an assessment of the bacterial microflora or by chemical tests such as the determination of total volatile basic nitrogen (TVBN). For deep frozen fish fillet, a method was developed based on the reduction of trimethylamine oxide (TMAO) to trimethylamine (TMA), as measured by a pH change in the cultured medium. The technique is rapid (8 h incubation at 25°C) and can be easily applied in laboratories. Comparison of the results obtained by this method with those based on TVBN and TMA determinations gave good correlations.     

Influence of different storage conditions on production of trimethylamine and microbial spoilage characteristics of mackerel products

Gradual accumulation of the fishy-odor compound trimethylamine (TMA) from bacterial reduction of trimethylamine oxide (TMAO) is one of the characteristic chemical changes attributed to fish spoilage. Changes in TMA values were correlated with sensory testing results, storage temperature, storage time, and viable bacteria counts. TMA contents were determined under different storage conditions. Headspace solid-phase micro extraction analysis with gas chromatography using flame ionization detection was used with different storage times and temperatures. Mackerel samples were inoculated with Pseudomonas fragi to monitor changes in the TMA content and pH. The TMA content increased proportionally with time during storage, and pH values and the microbiological quality were evaluated to analyze correlations with the TMA content in fish products. The TMA content increased with an increasing number of P. fragi with good linearity (R ²=0.997). Basic data are provided for developing a freshness indicator for fish spoilage.     

Colorimetric assay for determination of trimethylamine-nitrogen (TMA-N) in fish by combining headspace-single-drop microextraction and microvolume UV–vis spectrophotometry

In this work, headspace-single-drop microextraction has been used in combination with microvolume UV–vis spectrophotometry to enhance the determination of trimethylamine-nitrogen (TMA-N) in fish samples. TMA-N is often used for monitoring fish freshness, but due to the low analytical sensitivity usually achieved, its determination must be performed after certain time of storage in some fish species. The proposed methodology, based on the extraction and subsequent complexation of volatile TMA-N onto a picric acid-containing xylene microdrop exposed to the headspace, involves an important improvement of sensitivity (detection limit 6 × 10⁻⁴ mg TMA-N per 100 g of fish), a miniaturization of the AOAC Official Method (971.14) and a simple approach for routine labs. This method is well suited to determination of TMA-N in different species of frozen and fresh fish samples from markets and to study the evolution of TMA-N concentration in farmed turbot at the earliest stages of deterioration.     

Histamine production by Enterobacter aerogenes in sailfish and milkfish at various storage temperatures

Enterobacter aerogenes was studied for its growth and ability to promote the formation of total volatile base nitrogen (TVBN) and histamine in sailfish (Istiophorus platypterus) and milkfish (Chanos chanos) stored at various temperatures from -20 to 37 degrees C. The optimal temperature for bacterial growth in both fish species was 25 degrees C, whereas the optimal temperature for histamine formation was 37 degrees C. The two fish species inoculated with E. aerogenes, when not properly stored at low temperatures such as 15 degrees C for 36 h, formed histamine at above the U.S. Food and Drug Administration hazardous guideline level of 50 mg/100 g. Milkfish was a better substrate than sailfish for histamine formation by bacterial histidine decarboxylation at elevated temperatures (> 15 degrees C). Although higher contents of TVBN were detected in the spiked sailfish than milkfish during the same storage time at temperatures above 15 degrees C, the use of the 30-mg/100 g level of TVBN as a determination index for fish quality and decomposition was not a good criterion for assessing potential histamine hazard for both fish species. Bacterial growth was controlled by cold storage of the fish at 4 degrees C or below, but histamine formation was stopped only by frozen storage. Once the frozen fish samples were thawed and stored at 25 degrees C, histamine started to accumulate rapidly and reached levels greater than the hazardous action level in 36 h.     

液氮/液氨速冻鮰鱼片理化性质与组织结构变化

研究分析液氮与液氨速冻对斑点叉尾鮰鱼肉品质的影响。新鲜斑点叉尾鮰分割鱼片后分别进行工业隧道式液氮喷淋速冻（－90 ℃、35 min）、隧道式液氨速冻（－35 ℃、90 min）,速冻样品置于－18 ℃下贮藏90 d。分析比较新鲜鱼肉以及速冻鱼肉在不同冻藏时间解冻损失率、蒸煮损失率、加压失水率、剪切力、pH值、K值、挥发性盐基氮（total volatile basic nitrogen,TVB-N）含量、三甲胺（trimethylamine,TMA）含量与硫代巴比妥酸反应物（thiobarbituric acid reactive substance,TBARs）值,应用荧光显微镜观察鱼肉组织微观结构变化。结果表明：与新鲜鱼肉相比,速冻鱼肉蒸煮损失率增加,加压失水率、剪切力、pH值降低,K值、TVB-N含量、TMA含量、TBARs值均呈上升趋势;随着冻藏时间延长,速冻鱼肉理化性质发生劣变;鱼肉速冻后肌肉细胞面积减小,细胞间隙增大;相比液氨速冻,液氮速冻更有利于保持鱼肉持水性、新鲜度以及组织结构完整性,可有效抑制鱼肉冻藏期间的品质劣变。综上,液氮速冻可以有效保持冷冻鱼肉品质,冻藏30 d内,液氮速冻鱼肉品质特性更接近于新鲜鱼肉。