Post-mortem Degradation of Adenine Nucleotides in Muscle of the Lobster, Homarus americanus

SUMMARY— Thin-layer chromatography showed that postmortem degradation of adenine nucleotides in the tail muscle of lobster (Homarus americanus) followed the route: adeno-sine 5'-triphosphate (ATP) → adenosine 5'-diphosphate (ADP) → adenosine S'monophosphate (AMP) → inosine 5'-mono-phosphate (IMP) + inosine (Ino) → hypoxanthine (Hx). KCI extracts (0.6M) also degraded ATP by this route. Such extracts contained a weak AMP-aminohydrolase activity that was activated by ATP, but no adenosine aminohydrolase could be detected. Neither of these aminohydrolases were found in extracts made with water or 0.0244 K-succinate.     

冻结方式对不同部位草鱼呈味物质的影响

以草鱼腹肉、背肉和红肉为研究对象,采用－40?℃速冻、－20?℃乙醇液体冻结和－20?℃静止空气冻结对草鱼进行冻结处理,采用高效液相色谱法、氨基酸自动分析法以及电子舌测定不同冻结方式的鱼肉中呈味物质含量变化,并测定各部位鱼肉的乳酸含量。结果表明,冻结方式对鱼肉的鲜度和呈味物质含量有一定影响。肌苷酸（inosine monphosphate,IMP）和一磷酸腺苷（adenosine monophosphate,AMP）含量、游离氨基酸总量与冻结速率呈正相关,但乳酸、次黄嘌呤核苷（insoine,HxR）和次黄嘌呤（hypoxanthine,Hx）的含量与冻结速率呈负相关,在－20?℃冻藏条件下贮藏3?d后,－40?℃速冻组K值最小,－20?℃静止空气冻结组K值最大。红肉部分IMP、AMP含量低,而HxR和Hx含量较高,其滋味和鲜度较差,3?种冻结方式中红肉的K值分别为28.99%、40.92%、46.58%;腹肉与背肉中游离氨基酸含量相近,且高于红肉部位,但红肉中天冬氨酸、谷氨酸含量明显高于腹肉和背肉;红肉中乳酸含量显著高于腹背肉,且不同冻结方式对其影响较大。电子舌能有效区分不同冻结方式和不同部位的草鱼肉。     

不同贮藏条件下鸡肉肌苷酸含量的变化规律

为了探讨肌苷酸在冷藏和冷冻期间产生和降解规律,以70日龄黄羽肉鸡为实验材料,连续7 d测量4 ℃冷藏期间胸肌IMP、HxR、Hx、ADP、AMP和IMPc含量以及-20 ℃不同冷冻时间鸡肉IMP及其代谢物含量。结果显示:冷藏第2 d和第5 d IMP含量有显著降解,分别为屠宰后4 h的66%和45%。Hx含量在第2 d和第5 d极显著增加,分别为屠宰后4 h的2.6倍和4.6倍。HxR含量第4 d达到最大值,之后快速下降。IMPc含量从第5 d开始降解趋势明显。冷冻1周内IMP、Hx和HxR含量变化均不大。IMP含量冷冻1个月、210 d和540 d后分别为屠宰后4 h的65%、41%和6%,冷冻1个月到4个月之间变化不大。Hx和HxR含量分别在冷冻30 d和300 d时最高。IMPc含量冷冻210 d和540 d时下降极显著,分别为屠宰后4 h的84%和42%。因此,建议鸡肉4 ℃冷藏保存时货架期4 d为宜;-20 ℃冷冻保存时1周最宜,鸡肉冷冻保存时间最好不超过4个月。     

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.     

Inosine Monophosphate and Hypoxanthine as Indices of Quality of Shrimp (Penaeus Merguensis)

Changes in inosine-monophosphate (IMP) and hypoxanthine (Hx) concentrations in shrimp muscle stored in ice for up to 20 days were correlated with taste panel evaluations of the sensory quality. A good correlation exists between IMP concentrations and flavor as well as total sensory scores. Absence of IMP in shrimp muscle and values of 2 micromole Hx, and over, per gram of shrimp muscle indicate doubtful quality. Measurement of Hx shows potential value as an index in assessing quality of ice-stored shrimp.     

A review of the kinetics of degradation of inosine monophosphate in some species of fish during chilled storage

A literature search was made for data on the concentrations of inosine monophosphate (IMP) and its degradation products, inosine (Ino) and hypoxanthine (Hx), in the flesh of vertebrate fish during storage in ice. Twenty‐one publications containing data for forty‐five species were selected for review. A mathematical model was developed for analysing the data by assuming that the kinetics of degradation of IMP could be modelled as consecutive first order reactions. The model was fitted to the data and in about half of the cases examined in the review the data suggested that IMP and degradation products were lost by leaching and the kinetic model was extended to allow for this loss. In all of the cases reviewed the mathematical model was a good fit to the experimental data and the reaction rates for the reactions are tabulated in the paper. In all species the concentration of IMP decreased as a first order reaction, but for thirteen of the species examined the enzyme model of IMP to Ino to Hx did not fit the data in that either Ino or Hx did not accumulate in the muscle. There were only a few examples of replications of storage trials within species and comparison of the outcomes of these replications suggested that season or, in the case of farmed fish, genetic stock or cultural practices might influence initial IMP concentrations or reaction rates.     

NUCLEOTIDE CATABOLISM IN COLD STORED ADDUCTOR MUSCLE OF SCALLOP (ZYGOCHLAMYS PATAGONICA)

The postmortem catabolism of adenosine triphosphate (ATP) in cold stored scallop adductor muscles was examined. The change In the pH of stored muscles was also investigated. The ATP content increased for a short time after death and afterwards decreased up to 24 h of storage. Thereafter, the nucleotide level remained unchanged up to 120 h of storage. The ADP content slightly decreased up to 48 h and after that remained unchanged. The AMP slowly accumulated to around 15% of the total nucleotide concentration when the ATP decreased. Small amounts of IMP were detected in all samples. Conversely, adenosine (Ado) was not detected. Inosine (HxR) slightly increased after 48 h of storage and hypoxanthine (Hx.) significantly increased after 24 h. The 260/250‐absorbance ratio of muscle extracts and the pH of stored muscles fell sharply up to 24 h and then decreased slowly. The Hx contents were positively correlated (P < 0.01) with both the Hx/AMP ratios and the K values.     

草鱼冷藏期间ATP关联物含量及新鲜度变化

目的：分析草鱼冷藏期间腺嘌呤核苷三磷酸关联物含量的变化,研究草鱼肉中各核苷酸的含量与其新鲜度的相关性。方法：利用强碱将不稳定的核苷酸关联物反应生成其钠盐形式,通过高效液相色谱法检测核苷酸含量,并通过总挥发性盐基氮含量和感官性状的变化进行鲜度评价。结果：生成钠盐形式的腺嘌呤核苷三磷酸关联物能通过色谱很好地分离。新鲜鱼肉中含有高含量的肌苷酸,达504.34 mg/kg。冷藏2 d内草鱼腺嘌呤核苷三磷酸、肌苷酸含量快速下降,次黄嘌呤含量则迅速增加。冷藏后腺嘌呤核苷三磷酸未检出,肌苷酸下降幅度达92.77%,次黄嘌呤增加幅度达89.82%。冷藏期间挥发性盐基氮含量一直上升,冷藏6 d后超出最大值限度,冷藏草鱼的贮藏期限为6 d。     

Hypoxanthine Ratio Determination in Fish Extract Using Capillary Electrophoresis and Immobilized Enzymes

Fish freshness was assessed using capillary electrophoresis and an immobilized enzyme procedure to monitor degradation of inosine-5′-monophosphate (IMP), inosine (HxR) and hypoxanthine (Hx). The enzymatic method used an amperometric probe at + 0.7 V (platinum vs silver/silver chloride) with immobilized xanthine oxidase, catalase, nucleoside phosphorylase, and nucleotidase for converting Hx, HxR or IMP to uric acid. Capillary electrophoresis resolved IMP, inosine and Hx by migration rates resulting from an applied electric field (416 V/cm, 50 μA). Components were detected at 250 nm. The H ratio of Hx/[IMP + HxR + Hx] and simplified K value of [HxR + Hx]/ [IMP + HxR + Hx] were determined in cod, salmon and trout stored on ice (0-4°C) and at 20°C. The two procedures agreed and for all species H ratio and K values increased with storage time.     

Effect of pH and prefreezing treatment on the texture of yellowtail rockfish (Sebastes flavidus) as measured by the Ottawa Texture Measuring System

Texture is very important to the organoleptic quality of fish products. Poor frozen storage conditions or improper prefreezing treatment can result in unacceptably tough fillets. With some species, undesirable soft, mushy texture develops during chill storage.
This study is concerned with the influence of treatment prior to freezing (samples were frozen pre-rigor, in-rigor, post-rigor and after 6 days' chill storage in ice or refrigerated sea water) on the texture of yellowtail rockfish stored frozen as whole gutted fish or as fillets. The effect of pH was also studied. Texture was measured objectively using the Ottawa Texture Measuring System on samples stored for 6 months at −28°C.
A very good negative correlation was found between pH level and toughness as measured using a Kramer shear-compression cell in the Ottawa Texture Measuring System. Fish stored in refrigerated sea water prior to freezing were appreciably more tender. There was no statistical difference in texture (shear press force) values between samples stored as whole fish versus samples stored as fillets.     

Effect of Adenosine-Nucleotides and Their Derivatives on the Denaturation of Myofibrillar Proteins in vitro during Frozen Storage at −20°C

To investigate the effect of adenosine-nucleotides and their derivatives on the denaturation of myofibrillar proteins, 235 nmoles/mL adenosine-5′-diphosphate (ADP), adenosine-5′-monophosphate (AMP), inosine-5′-monophosphate (IMP), inosine (HxR), or hypoxantine (Hx), was added to 3 mg/mL actomyosin (AM) solution suspended in 0.10M KC1 solution and stored at ?20°C for 12 wk. The AM was extracted from milktish dorsal muscle. Protein denaturation was evaluated by measuring solubility, Ca-ATPase and Mg(EGTA)-ATPase activity of AM, by analyzing changes in electrophoretic profiles and transmission electron microscopy. Inosine and hypoxanthine accelerated protein denaturation compared to control samples. Infrared spectrum analyses indicated that negatively charged groups of these nucleotides interacted with amino or imino groups on AM after addition. ADP, AMP, and IMP had a protective effect on denaturation of AM during frozen storage at ?20°C.     

Comparative Rates of IMP Degradation in Unfrozen and Frozen-and-Thawed (Slacked) Fish

SUMMARY— The comparative rates of IMP degradation between fresh and frozen-and-thawed (slacked) fish were compared on six different species of fish. Several factors that could contribute to a rate change of IMP degradation were evaluated. These included freezing temperatures, time in frozen storage, pre- and post-rigor freezing, and method of killing the fish.
English sole and rainbow trout showed slight increases in the rate of IMP degradation when they were frozen and then thawed within 48 hr. Silver salmon and halibut that were frozen and then thawed within 48 hr showed no change in the rate of IMP degradation. Halibut, however, that was frozen and stored at −20°F for 3 months showed a slight decrease in the rate of IMP degradation after it was thawed; but king salmon handled under the same conditions did not.
The method of kill or freezing the fish either pre- or post-rigor did not alter the rate of IMP degradation after the fish was thawed.
No loss of IMP occurred in fish (halibut) stored at −20°F. Over one-third of the original IMP content was lost in halibut stored at +15°F after 3 months of storage.
These results show that there is no significant difference in the rate of IMP degradation between fresh and slacked fish. The flavor-contributing effect of IMP in slacked fish therefore should be the same as in fresh fish, provided the fish was frozen and stored at or near a temperature of −20°F.     

Muscle High-Energy Phosphates and Stress Affect K-Values during Ice Storage of Atlantic Salmon (Salmo salar)

Initial levels of white muscle high-energy phosphates, IMP, ATP:IMP-ratio, adenylate energy charge and pH were used as indicators of handling stress when Atlantic salmon were slaughtered. Ante-mortem handling included fish that were either anesthetized (baseline), quickly netted and killed by a blow to the head (unstressed) or chased to exhaustion in the holding tank (stressed). During subsequent storage in ice, freshness was evaluated in terms of IMP, HxR, Hx and K-values. HPLC showed initial differences in distribution of metabolites induced by struggling gradually fell during storage. K-values were different only for 2 days post mortem, but the effect of handling stress was discernible as higher mean K-values and different IMP and HxR contents for up to 7 days post mortem.     

Onboard processing of deepwater pink shrimp (Parapenaeus longirostris) with liquid ice: Effect on quality

This study investigated the effect on the quality of deepwater pink shrimp (Parapenaeus longirostris) of onboard chilling with liquid ice versus the traditional chilling with flaked ice. Quality was estimated by physical, chemical, microbiological and sensory parameters after 24 h and 4 days of chilled storage. Application of liquid ice immediately after catch for the fast chilling of pink shrimp reduced the formation of nitrogenous compounds and slowed down the increase in pH and the development of microorganisms during iced storage. On the other hand, texture (breaking force, hardness and elasticity) showed only minor changes. Pink shrimp chilled with liquid ice showed, however, loss of characteristic bright colours and development of dull tones in the carapace that depreciates the product's commercial value. Nevertheless, application of liquid ice onboard was advantageous over the utilization of the traditional type of ice, and seems particularly applicable when shrimp is to be used as a raw material for the type of processing that requires elimination of the carapace.     

Comparison Of Air-blast And Pressure Shift Freezing On Norway Lobster Quality

Pressure shift freezing (PSF, 200 MPa, –18 °C) of whole Norway lobster was compared with air-blast freezing and with pressurized samples (200 MPa, 5 °C) without freezing for its effect on the quality in texture, structure, water, and salt soluble protein extractabilities. For the pressurized Norway lobster meat either with PSF or without freezing, toughness increased while salt soluble protein extractability decreased. Conversely, air-blast freezing did not affect the textural quality of the meat. Scanning electron micrographs showed that PSF yielded smaller ice crystals than air-blast freezing.     

Sensory,microbiological, and chemical spoilage of cultured common sea bass (<Emphasis Type="Italic"> Dicentrarchus labrax</Emphasis>) stored in ice: a seasonal differentiation

Common sea bass ( Dicentrarchus labrax) of a Greek cage-culture origin, sampled in December and July, were stored in ice, and their sensory, microbiological and chemical spoilage patterns were studied as well as their seasonal differentiation. The sensory storage life was determined at 15 days of ice storage. The microbial population in the muscle reached levels of 10⁵ at the acceptability limit. The ATP breakdown pattern showed a quick depletion of inosine-monophosphate (IMP) in the first 8–9 days of ice storage and slower depletion thereafter. Inosine (INO) and hypoxanthine (Hx) were formed at significant quantities. TVBN and TBA, as indicators of protein breakdown and lipid oxidation, respectively, showed low and delayed increase. A seasonal effect was observed with summer fish showing higher rates of K-value increase during early spoilage, while winter fish showed higher K-values, microbial populations and TVBN at late spoilage stages.     

Spoilage changes in the deep water fish, smooth oreo dory during storage in ice

Smooth oreo dory ( Pseudocyttus maculatus ), a deep water fish, was monitored for changes during storage in ice. Based on the sensory evaluation of the cooked flesh the storage life was 8 days for acceptable quality fish.
Bacterial counts of flesh and surface, the loss of inosine monophosphate (IMP) and the K value showed significant changes during the storage life. Therefore these were found to be useful for monitoring loss of freshness and development of spoilage. After 13 days there were off flavours in the cooked fish, dephosphorylation of IMP had levelled off, and the K value had reached 70%.
The changes that occurred during storage of this deep water species in ice were similar to those changes commonly observed in demersal species from shallow temperate coastal waters.     

Effect of pre-freezing icing duration on quality changes in frozen Nile perch (Lates niloticus)

Deterioration of fish during frozen storage entails change in texture, loss of protein functionality, lipid hydrolysis as well as biochemical changes. These changes were monitored in Nile perch frozen after 3, 6, 9, 12, 24, 48 and 72 h on ice, with the aim of establishing the effect of pre-freezing icing on deterioration of fish during frozen storage. During the icing duration, the expressible moisture (EM) was found to reduce while protein solubility (PS), thiobarbituric acid (TBA), trimethylamine (TMA), hypoxanthine (Hx), and free fatty acids (FFA) concentration increased. During frozen storage, PS decreased while EM was found to increase. Hx, TBA and FFA increased, while texture was found to deteriorate. TMA remained constant during frozen storage. The extent of texture deterioration was correlated negatively to PS and positively to EM. It was concluded that holding fish on ice for about 9 h deterred the negative changes that occur during frozen storage.     

油爆工艺对上海熏鱼风味物质的影响

以上海熏鱼为研究对象,利用固相微萃取-气相色谱-质谱法、感官评定、高效液相色谱法和氨基酸自动分析仪,采用单因素方法研究油爆工艺对熏鱼风味的影响。结果显示：草鱼第1次浸渍、温度140、155、170、185、200?℃油爆8?min及温度170?℃油爆4、6、8、10、12?min后检测到挥发性物质分别为58、64、79、78、75、76?种及75、75、78、74、74?种。油爆温度升高和时间延长时,1-辛烯-3-醇、己醛等土腥味物质含量减少,关键风味物质为1-辛烯-3-醇、己醛、壬醛、癸醛、2-壬烯醛、2-癸烯醛、2,4-壬二烯醛、2,4-癸二烯醛等。油爆后,一磷酸腺苷（adenosine monophosphate,AMP）和肌苷酸（inosine monphosphate,IMP）含量增加,次黄嘌呤（hypoxanthine,Hx）含量减少;鲜甜味氨基酸含量增加,苦味氨基酸含量减少。温度185 ℃和时间10 min时,AMP和IMP含量较高,Hx含量较低;谷氨酸和组氨酸的味道强度值最高,呈味氨基酸总量最高,更好地保留鱼肉鲜甜味。此时,鱼肉口感佳,香味浓,表面呈金黄色,感官最好。     

Hydrophilic interaction chromatographic determination of adenosine triphosphate and its metabolites

A new HPLC method based on hydrophilic interaction chromatography (HILIC) has been developed for the simultaneous analysis of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine (Ino), hypoxanthine (Hx) and nicotinamide adenine dinucleotide (NAD⁺) in pork loin muscle. The chromatographic analysis has been developed using a zwitterionic polymeric column and it has been optimised in terms of linearity, repeatability, reproducibility and recovery. Detection limit values of 0.10, 0.15, 0.05, 0.16, 0.16, 1.72 and 0.15 μg/mL for ATP, ADP, AMP, IMP, Ino, Hx and NAD⁺ respectively were achieved. A comparison between the pork meat concentrations of the compounds analysed by hydrophilic interaction chromatography (HILIC), using a ZIC®-pHILIC column, and ion-pair reversed-phase chromatography (IP-RP-HPLC), using a Zorbax Eclipse XDB-C18 column, has been done, concluding that the new chromatographic methodology constitutes a valid and reliable alternative to the existing methods. Finally, this method has also proved to be very effective in the isolation of guanosine, guanosine monophosphate (GMP), guanosine diphosphate (GDP), guanosine triphosphate (GTP), creatinine (Cn) and uric acid (UA) from a standards mixture.