武昌鱼宰后4℃冷藏条件下品质变化规律

通过对武昌鱼宰后4?℃冷藏条件下72?h内僵直指数、质构、pH值、持水力、白度、5'-三磷酸腺苷(5'-adenosine triphosphate,ATP)及其关联物含量的测定和分析,探究武昌鱼的品质变化规律.结果表明:武昌鱼宰后6?h的硬度、僵直指数明显高于其他时间点,之后开始下降;武昌鱼宰后pH值迅速下降,宰后6...     

Changes in baseline levels of nucleotides during ice storage of fish and crustaceans from the Portuguese coast

Adenine nucleotides and related compounds were measured in North Atlantic hake, monkfish, rockfish, Norway lobster, and red shrimp from the South of Portugal immediately after catch and after a 72-hours ice storage period. To preserve the samples until analysis, a freezing technique with liquid nitrogen was developed and data compared with those from immediate extraction. The use of plastic vials in liquid nitrogen freezing gave similar data as when immediate post mortem extraction was done. Inosine monophosphate (IMP) was the main nucleotide present in the fish species, whereas adenosine monophosphate (AMP) was the major component of crustaceans. During ice storage of fish, adenine nucleotides were almost completely converted to IMP. Rockfish showed a significant catabolism of IMP with conversion to hypoxanthine (Hx). Red shrimp and, especially, Norway lobster presented an important transformation of AMP into IMP. In general, Hx was either not detected (crustaceans) or was present in very low amounts, the highest levels being detected in rockfish after ice storage. This species presented also after 72 h the highest K value (58%), whereas in the other cases the values ranged between 7% and 11%. Trigonelline (Trigo), a UV-absorbing betaine, was also present in both crustacean species together with adenosine triphosphate (ATP) and related compounds.     

缺氧诱导因子对滩羊肉宰后初期能量水平及肉色的影响

为研究缺氧诱导因子（hypoxia-inducible factor 1，HIF-1）对滩羊肉宰后成熟48 h内糖酵解关键酶、能量水平、pH值及肉色的影响，本实验以4 ℃成熟2、6、12、24、48 h的滩羊背最长肌为研究对象，测定不同成熟期HIF-1表达量，磷酸丙糖异构酶（triose-phosphate isomerase，TPI）活力，能量物质三磷酸腺苷（adenosine triphosphate，ATP）、二磷酸腺苷（adenosine diphosphate，ADP）、单磷酸腺苷（adenosine monophosphate，AMP）水平，肌肉pH值及肉色的变化，并对HIF-1表达量与TPI活力，ATP、ADP、AMP含量，pH值及肉色进行相关性分析。结果表明，宰后2～24 h内HIF-1表达量迅速升至最高值，24 h后有所下降；TPI活力于宰后6 h升至最高，随后逐渐降低；宰后48 h内能量物质ATP、ADP、AMP水平均随成熟时间延长逐渐降低；宰后48 h内pH值显著降低（P＜0.05）；肉色指标L*、a*值及b*值均随成熟时间延长显著升高（P＜0.05）。宰后成熟2～48 h内滩羊肉HIF-1表达量与TPI活力、能量物质水平、肉色及pH值均显著相关（P＜0.05、P＜0.01），可能是由于受宰后缺氧信号诱导，HIF-1表达量于宰后6 h内迅速升高，HIF-1复合体转移至细胞核与糖酵解基因结合，促进糖酵解相关基因表达，促使糖酵解途径增强，提高了糖酵解相关酶活力，并降低肌肉pH值。综上，HIF-1可能通过调控宰后糖酵解及肌肉pH值影响肉色。     

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。     

Color Development of Squid Skin as Affected by Oxygen Concentrations

ABSTRACT:  Color development of squid skin was controlled by O₂ concentration for storage. When stored above 10% O_2, the color index (CI) as an index of color development of skin increased in 24 h, and decreased gradually with further storage. The CI profile at 10% O₂ was practically identical to that in air. When stored at 0.1% O₂, in the presence of N₂, the CI increased partly in 6 h and decreased. Morphological observation of chromatophore distinguished the CI increase at 0.1% and 10% O₂ by their shape and size distribution. However, the storage of squid at O₂ concentration between 2.5% and 7% practically did not change the CI for at least 48 h. ATP content of skin was kept unchanged when the storage atmosphere contained O₂ concentration at 2.5% up to 48 h, while the content decreased rapidly with a half decrease in 6 h when stored at 0.1% O₂. It was demonstrated clearly that ATP is regenerated in the presence of O₂, but the ATP concentration did not determine the CI change during the storage. Exposure to high concentration of O₂ might induce a full color development of squid skin.     

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.     

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。     

宰后僵直及成熟过程中羊背最长肌理化性质的变化

动物宰后从肌肉到肉品经过僵直、成熟等一系列复杂的生理生化反应。僵直及成熟过程的研究可为肉品质改善及肉制品加工提供理论依据。选取杂交公羊(小尾寒羊×北京本地羊)双侧背最长肌在4℃成熟0.5、2.0、6.0、12.0、24.0、48.0、72.0、120.0、168.0 h,测定不同时间的pH值、剪切力、肌节长度、ATP含量、肌原纤维小片化指数(myofibril fragmentation index,MFI)、钙蛋白酶活力。结果表明:宰后成熟过程中,pH值先下降后逐渐趋于稳定,从第24小时后变化不显著(P0.05);剪切力先上升后下降,在第24小时达到最大值;肌节长度在宰后先缩短后逐渐变长,且在第48小时缩至最短;ATP含量先上升后下降,48 h后趋于稳定;μ-钙蛋白酶80 kD大亚基在宰后24 h基本降解完全,其降解的78 kD大亚基在第48小时降解完全;肌间线蛋白和肌钙蛋白T作为μ-钙蛋白酶的降解底物,在成熟过程中发生降解,第168小时几乎观察不到完整的蛋白条带;随着宰后时间的延长,羊背最长肌从第2小时开始僵直,到第24小时程度达到最大,从第48小时开始解僵,解僵后肉的嫩度逐渐改善。     

THE EFFECT OF TRINITROPHENYL NUCLEOTIDE DERIVATIVES ON THE ADENOSINE TRIPHOSPHATASE ACTIVITIES IN MAIZE TONOPLAST VESICLES

The effects of trinitrophenyl (TNP) derivatives of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and adenosine monophosphate (AMP) on the coupled activities of the tonoplast ATPase in corn roots were investigated. The addition of TNP-ATP at micromolar concentrations (0.5–0.25 mM) significantly decreased both the ATP hydrolytic activity and the coupled proton pumping activity. The presence of TNP-ATP resulted in an increased Km for ATP and a reced maximum enzyme velocity. Unlike TNP-ATP that strongly inhibited proton transport at low concentration, TNP-ADP inhibited this activity only slightly. TNP-AMP stimulated proton transport at low concentrations. ADP and AMP inhibited the initial rate of proton transport in a different manner. The concentrations required to inhibit half of the initial rate of proton transport activity for ADP and AMP were 80 μM and 2 mM, respectively. The results suggest that tonoplast vesicles may contain at least two kinds of nucleotide binding sites.     

BIOCHEMICAL PROPERTIES OF ACTOMYOSIN AND EXPRESSIBLE MOISTURE OF FROZEN STORED ADDUCTOR MUSCLES OF PATAGONIAN SCALLOP (ZYGOCHLAMYS PATAGONICA)

The biochemical properties of actomyosin and the expressible moisture of frozen stored adductor muscles of scallop (Zygochlamys patagonica) were investigated. After freezing (zero time of storage) both the enzymatic activity and the reduced viscosity of actomyosin remained unchanged with respect to those corresponding to actomyosin from unfrozen muscles. Both parameters significantly decreased (P < 0.01) at 4 months of frozen storage and thereafter gradually decreased. No significant differences (P > 0.01) were observed in the relative percentages of myosin, actin, and in the myosin/actin ratio up to 4 months of storage. Thereafter myosin significantly decreased (P < 0.01) up to the end of storage. The decrease in the biochemical properties of actomyosin was accompanied by a loss in the water holding capacity of the muscles.     

Physicochemical Changes of Starch in Maize Tortillas During Storage at Room and Refrigeration Temperatures

Physicochemical changes of starch and loss of texture were determined in maize tortillas during 72 h storage at room and refrigeration temperatures. Properties analyzed included apparent amylose content, content of enzyme resistant starch (RS) type III, and thermal properties determined with differential scanning calorimetry (DSC) and X‐rays diffraction. In addition, tortilla firmness was assessed using an uniaxial compression test with a texture analyzer. Storage temperature did not significantly affect firming rate or starch properties, except from thermal properties. Firmness was developed mainly during the first 24 h storage, remained nearly the same during 24—48 h and slightly increased after 72 h storage. Resistant starch (RS) formation followed the same trend as development of firmness. A first order endothermic transition that can be attributed to amylopectin retrogradation was observed after 2 h storage at both temperatures. This transition shifted to higher temperatures during storage, the effect was specially evident for refrigerated tortillas. X ray diffraction patterns of stored tortillas suggested that crystallinity slightly increased during storage. Most of the loss of tortilla texture, determined as firmness, occurred during the first 24 h storage at room and refrigeration storage conditions. This loss of texture was likely due to starch retrogradation and the latter possibly increased content of resistant starch.     

暂养净化及无水保活中太平洋牡蛎活力品质与呈味物质分析

为探明太平洋牡蛎(Crassostrea gigas)采捕后不同流通阶段活力品质与呈味物质的变化规律，模拟产业流通实际，将活体太平洋牡蛎进行暂养净化、诱导休眠和无水保活，并在不同时间段取样，以腺苷三磷酸(adenosine triphosphate,ATP)关联物、核苷酸能荷值(adenylate energy charge,AEC)及游离氨基酸变化分析牡蛎活力品质的变化；以呈味化合物含量结合呈味强度值评价流通过程中牡蛎风味品质变化。结果显示，采捕后运输及环境胁迫对其活力、呈味物质有显著影响，通过24 h暂养净化，牡蛎活力品质均呈明显恢复，其中ATP、AEC、游离氨基酸总量较净化前明显上升(P<0.05)，机体活力达到新水平；诱导休眠至保活流通阶段，牡蛎受到低温、缺氧胁迫需调动更多能量物质以维持机体平衡，各项活力品质指标较净化前明显降低(P<0.05)，处于稳定的较低水平。呈味化合物中，牡蛎在暂养净化后鲜甜味氨基酸增加，苦味氨基酸下降，随着保活时间的延长，呈味氨基酸缓慢下降；鲜甜味核苷酸肌苷5’-单磷酸(inosine 5’-monophosphate,IMP)、单磷酸腺苷...     

Staling of cake prepared from rice flour and sticky rice flour

MiGao, prepared from rice flour and sticky rice flour, is a kind of steam cooked Chinese cake. Staling of MiGao resulted in loss in texture and eating quality. Moisture content, water activity, texture, differential scanning calorimetry thermograms and sensory quality of MiGao, were monitored and were found to be significantly affected by cake staling when stored at room temperature for up to 5 days. The moisture content decreased after 2 days of storage and during the following days the crumb moisture content remained practically unchanged. Firmness was developed mainly during the first day of storage, remained at a similar level from day 2 to 3 and increased slightly after the third day of storage. A decrease in sensory quality and acceptability of the MiGao was observed during storage. Differential scanning calorimetry was used to follow changes of starch retrogradation in MiGao crumb. Amylopectin recrystallisation in MiGao continued to increase during storage.     

Effect of electrical stimulation on the rheological properties of rabbit skeletal muscle

The effect of electrical stimulation on the rheological properties of rabbit skeletal muscle after death was investigated. The extensibility of electrically stimulated psoas muscles decreased more rapidly than that of non-stimulated muscles. For raw non-stimulated longissimus thoracis muscles excised from the carcasses immediately after slaughter, the penetration force required was greatest 24 h after slaughter and then decreased slightly after 168 h. The corresponding force for stimulated longissimus thoracis muscles increased to a maximum in 12 h and then decreased to values less than non-stimulated muscles. However, in the case of raw longissimus thoracis muscles whichhad been attached to the skeleton until measurement, there was no significant difference in penetration force between stimulated and non-stimulated muscles. In cooked muscles, electrical stimulation resulted in lower penetration forces at 24 h post mortem, but on further storage the differences decreased.     

Changes in flavor precursors, pungency, and sugar content in short-day onion bulbs during 5-month storage at various temperatures or in controlled atmosphere

Short-day onion bulbs (cv. TG 1015Y) were stored in 1% O(2,) 99% N(2) air at 5 °C (controlled atmosphere [CA]), or in ambient air at 5, 24, or 30 °C, for 5 mo. Changes in flavor precursors, pungency, and sugar content were investigated. After 5 mo of storage, 1-propenyl-L-cysteine sulfoxide concentrations increased continuously at 5 °C, gradually decreased in CA, slightly increased for 3 mo, and returned to initial levels at 24 °C and decreased below initial levels at 34 °C. Methyl-L-cysteine sulfoxide concentrations remained unchanged in all storage conditions. Onion pungency levels significantly increased at 5 °C, and decreased at 30 °C. Storage in CA and at 24 °C resulted in some fluctuations in pungency but the levels remained similar to initial levels. The calculated pyruvic acid concentrations were approximately 1.0 μmole/mL higher than the measured concentrations, and showed an increase at 5 °C and a slight reduction at 30 °C, consistent with the pungency results. Storage at 5 °C and in CA resulted in slight increases in fructose and glucose concentrations for 3 to 4 mo with subsequent rapid decreases, while sucrose concentrations remained unchanged. However, at 24 and 30 °C, fructose and glucose concentrations continuously decreased, accompanied by a continuous increase in sucrose concentrations. Storage in CA maintained the quality of onions best, as evidenced by the smallest changes in flavor precursors, pungency, and sugar concentrations, while storage at 5 °C resulted in increased pungency. Storage at 24 and 30 °C was tested for the purpose of comparison only; these temperatures are not recommended for commercial storage.     

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.     

Influence of temperature on the rate of post-mortem metabolism and water-holding capacity of bovine neck muscles

Strips of forty bovine neck muscles were placed at temperatures in the range -1° to +30°C within 45 min of slaughter and stored for up to 24 h. Strips were taken at various times during storage and assayed for pH, 'R' value (degree of transformation of ATP to IMP) and ATP concentration. The water-holding capacity (WHC) of the intact muscle was compared with the WHC of a salted muscle homogenate prepared at each sampling time. The rate of pH fall post mortem was relatively low around +5°C and increased at lower or higher temperatures. ATP concentration showed a delay phase dependent on storage temperature and a subsequent rate of depletion which was also temperature dependent. The patterns of change in WHC of the muscle samples and the salted homogenates differed, the former showing a rapid fall to a fairly steady level shortly after initiation of storage, the latter showing no appreciable change until the onset of rigor. It is suggested that salting meat at any time prior to the onset of rigor will confer improved WHC and that the temperature of storage post mortem should be chosen to induce low rates of ATP turnover so as to prolong the feasible delay between slaughter and salting.     

冷藏时间对冷却猪背最长肌品质的影响

以宰后24 h的猪背最长肌为研究对象,研究4 ℃条件下冷藏0、12、24、36、48 h对猪背最长肌pH值、色 差、冷藏损失、蒸煮损失、剪切力和水分迁移状态的影响。结果表明：随着冷藏时间的增加,猪背最长肌的pH 值、黄度值（b*）、冷藏损失率和蒸煮损失率均显著提高（P＜0.05）;亮度值（L*）和红度值（a*）在冷藏24 h 内差异不显著（P＞0.05）;冷藏48 h时,猪背最长肌的pH值、L*、b*、冷藏损失和蒸煮损失最大,剪切力最小; 低场核磁共振结果表明,随着冷藏时间的增加,T2b、T21和T22起始弛豫时间显著延长（P＜0.05）,T21的峰面积比例 降低,T22的峰面积比例增加。综上所述,4 ℃条件下冷藏24 h以内有利于保持猪背最长肌的品质。     

Induction of bovine sperm capacitation by TEST-yolk semen extender

Ejaculated bull semen was diluted 1:10 in the TEST-yolk buffer, cooled slowly to 4 degrees C, and stored for up to 48 h. Aliquots were taken at 0, 4, 8, 16, 24, and 48 h and washed once or three times in bovine serum albumin-saline and the sperm pellets resuspended in this saline. Fertilization of zona-free hamster oocytes was used to assess sperm capacitation. Motility differed between samples washed once or three times (53.7 vs. 21.7%). Motility was highest at 4 h storage but did not differ between 16, 24, or 48 h of storage. More sperm without intact acrosomes were found at 4 h than at 0 h, but the percentage did not change further until after 24 h. Penetration of oocytes was not different between sperm washed once or three times (28.5 vs. 26.9%). No penetration occurred at 0 h, and highest penetration rates occurred at 4 and 8 h of storage (32.1 and 33.4%). Penetration rates at 16, 24, and 48 h were not different (25.3, 25.2, 22.5%). In conclusion, storage of bull sperm in TEST-yolk buffer for 4 to 48 h resulted in capacitation. Even though capacitation was induced by 4 h, at least 71% of the sperm population had not undergone an acrosome reaction by 48 h of storage. This may explain why penetrability was maintained over this period.     

面包面团玻璃化贮存与非玻璃化贮存的品质比较

面包面团分别贮存在家用冰箱(-18℃,非玻璃态贮存)和超低温冰箱(-88℃,玻璃态贮存)中,采用质构仪分析面团在贮存0、7、30、90 d后的面团质构特性,并测定面包比体积。结果表明:(1)非玻璃态贮存面团的黏度、延展性先升高后降低,变化幅度大,而面团弹性、弹性恢复比快速下降;(2)玻璃态贮存面团的黏度、延展性先降低,而后缓慢升高,面团弹性随贮存时间小幅下降、弹性恢复比基本无变化;(3)面包比体积变化情况与面团弹性变化情况相似,说明面团的弹性能较好地反映面包的比体积。玻璃态贮存可以降低重结晶反应速率,减少大冰晶生成,降低面团在贮存过程中的面筋网络破坏;可以降低面团中水分活性,减小水分迁移速率,防止淀粉过度水化。