CHARACTERISTICS OF TMAO DEGRADING SYSTEMS IN ATLANTIC SHORT FINNED SQUID (ILLEX ILLECEBROSUS)

The decomposition of trimethylamine oxide (TMAO) to dimethylamine (DMA) was studied in the mantle of squid, Illex illecebrosus. The production of DMA in either whole or ground mantle stored at – 20°C was low or nonexistent. However, significant DMA was produced from TMAO during heating of squid or squid extracts. Conversion of TMAO to DMA was shown to reside in the soluble fraction of the squid mantle which catalyzed the breakdown of TMAO in an assay system consisting of FeCl₂ and ascorbate at room temperature. On the average, some 10–15% of the activity was accounted for by a high molecular weight, thermolabile substance, presumably an enzyme. The rest of the activity was in a small molecular weight, thermostable fraction. The low molecular weight fraction produced significant quantities of TMA as well as DMA, had low activity with flavin-NADH, and was not activated by methylene blue.     

DISTRIBUTION AND SOME CHARACTERISTICS OF TRIMETHYLAMINE N-OXIDE (TMAO) DEMETHYLASE ACTIVITY OF RED HAKE MUSCLE

It has been suggested by some workers that decomposition of trimethyl N-oxide (TMAO) to dimethylamine (DMA) and formaldehyde in gadoid fishes occurs via enzymic processes while others have suggested a nonenzymic pathway. DMA production in frozen red hake muscle is shown in this study to be enzymic by the necessity of the high molecular weight soluble or insoluble fraction from red hake to convert the low molecular weight components of flounder muscle to DMA. In red hake muscle the TMAO demethylase activity is approximately evenly divided between the high molecular weight soluble and the insoluble fractions: the amount of potential activity in either fraction is 60–100 times that required for the production of DMA that normally occurs during frozen storage of the muscle tissue. The K_m for TMAO of the soluble enzyme was approximately 3 mM; the concentrations of TMAO in red hake muscle range from 60 to 140 mM (calculation based on water content of 80%). Thus, it seems unlikely that TMAO or TMAO demethylase limit the rate of the reaction. On the other hand, the K_m values for flavin mononucleotide and NADH are higher than the concentrations of these components found in the tissue suggesting that the cofactors limit the rate of TMAO breakdown to DMA and formaldehyde in the stored muscle. This supports other studies (Landolt and Hultin 1982; Banda and Hultin 1983) in which the same conclusion is reached based on other considerations.     

Shelf life of ice-stored redfish, Sebastes marinus and S. mentella

Redfish ( Sebastes marinus and S. mentella ) were caught by an Icelandic trawler, stored at about 0°C in boxes in the hold and landed in a German fishing harbour. Boxed redfish, differing in storage time on board, were subsequently stored in melting ice in the chill store of the laboratory at a temperature of +4°C until the borderline of saleability was reached. the quality loss of the ice-stored redfish was monitored by a number of chemical, physical and microbiological parameters including volatile base nitrogen (TVB-N), trimethylamine (TMA), trimethylamine oxide (TMAO), creatine, ethanol, Fishtester readings and number of cfu. AH parameters were correlated with sensory analysis and time in ice.
The rate of deterioration of iced redfish depended on the conditions of storage. Sensory analysis was the most accurate indicator of the limit of saleability of redfish. Iced redfish, stored mainly in a chill store (4–5°C) onshore, had a shelf-life of 16 to 19 days from catching. Fish stored at 0.5°C in the hold of the fishing vessel had a shelf-life of 22 days: These results reflect the different storage temperatures and the effects of handling, transport and storage damage on the quality of the fish. the Fishtester proved to be very useful for the determination of deterioration. Measuring ethanol, TVB-N and TMA gave no information about quality changes during the first 12 days of storage.     

ESR studies on the thermal decomposition of trimethylamine oxide to formaldehyde and dimethylamine in jumbo squid (Dosidicus gigas) extract

The effects of ferrous iron, heating temperature and different additives on the decomposition of trimethylamine oxide (TMAO) to formaldehyde (FA) and dimethylamine (DMA) and generation of free radicals in jumbo squid (Dosidicus gigas) extract during heating were evaluated by electron spin resonance (ESR). The thermal decomposition of TMAO to TMA, DMA and FA and free radical signals was observed in squid extract, whereas no DMA, FA and free radical signals were detected in cod extract or in aqueous TMAO solution in vitro at high temperatures. Significant increase in levels of DMA, FA and radicals intensity were observed in squid extract and TMAO solution in the presence of ferrous iron with increasing temperature. Hydrogen peroxide stimulated the production of DMA, FA and ESR signals in squid extract, while citric acid, trisodium citrate, calcium chloride, tea polyphenols and resveratrol had the opposite effect. Similar ESR spectra of six peaks regarded as amminium radical were detected in the squid extract and TMAO–iron(II) solution, suggesting that the amminium radical was involved in the decomposition of TMAO.     

Chemical Changes and Visual Appearance of Albacore Tuna as Related to Frozen Storage

Fresh albacore tuna (Thunnus alalunga) were frozen and stored at –18°C and –25°C for 1 yr. Chemical and visual analyses were carried out at 1, 3, 6, 9 and 12 mo storage. Storage time correlated (P<0.05) with the low loss of moisture at –18°C, slight reduction of TVBN at –25°C and low increases of DMA, TMA, and TBARS at both temperatures. TMAO concentration (p=0.07), drip loss on cooking (p=0.52), peroxide value (p=0.059), FFA concentration (p=0.33) and pH (p=0.20)did not change significantly with period of storage but ?25°C resulted in a lower production of DMA and FFA than ?18°C. Results from chemical analyses correlated well with basic visual appearance.     

Optimum Postmortem Chilled Storage Temperature for Summer and Winter Acclimated, Rested, Chinook Salmon (Oncorhynchus tshawytscha) White Muscle

Chemical anaesthesia (AQUI‐S^TM) was used to harvest 2 groups of tank‐reared chinook salmon (Oncorhynchus tshawytscha), naturally acclimated to summer (18.8 °C) and winter (10.7 and 12.4 °C) temperatures, in a “rested”state. Carcasses were stored in 35% seawater at temperatures between approximately 2 and 19 °C to investigate the effects of acclimation and storage temperature on the postmortem metabolic rate of rested epaxial white muscle tissue. Muscle pH, [lactate], and adenosine triphosphate/inosine monophosphate measurements made 20 h postharvest indicated that winter acclimated fish were 2.2 times more sensitive to temperature than summer fish. A 3^rd group of winter acclimated fish, stored between –1.2 and 6 °C, indicated that significant cold injury only occurred on freezing.     

EFFECTS OF SOY PROTEIN AND FREEZING TREATMENTS ON COOKING LOSS AND COMPOSITION OF BEEF PATTIES

All-beef and soy-extended patties were frozen to −18°C in either 24, 48, 72 or 96h and stored at −23, −18 or −7°C for 6, 9, 12, 18 or 24 months. The addition of soy resulted in a substantial reduction in cooking loss for patties cooked from the frozen state with a greater retention of moisture in cooked patties. Freezing reduced cooking loss for soy-extended patties, but increased cooking loss for all-beef patties. Faster freezing (-18°C in 24 h vs. −18°C in 96 h) reduced cooking loss and produced higher moisture values in all-beef patties. Patties stored at –7°C lost more moisture during cooking. Increased frozen storage time had a minimal effect on cooking losses, moisture and fat levels. Where it is essential for frozen patties to sustain minimal cooking losses with maximal moisture in cooked patties, the inclusion of soy protein concentrate, faster freezing, and storage at –18°C or colder are suggested.     

The occurrence of volatile amines in uncured and cured pork meat and their possible role in nitrosamine formation in bacon

The concentrations of volatile amines were determined in the eye muscle of 10 pork carcasses at the following stages of curing: immediately after slaughter, before curing, after maturation and after vacuum-packed storage of the bacon. Methylamine (MA), dimethylamine (DMA), trimethylamine (TMA), ethylamine (EA), diethylamine (DEA), n-propylamine (n-PA) and isopropylamine (iso-PA) were detected by gas chromatography; MA was present in greatest concentration [up to 1900 μg/kg (1 part/10⁹)], the concentration of the others being considerably less. During the course of bacon manufacture, the concentrations of DMA, TMA, n-PA and iso-PA increased consistently up to the end of the maturation period, despite the presence of nitrite both in the brine and in the bacon; in subsequent storage, only DMA and TMA continued to increase. MA decreased during curing and maturation, and thereafter remained unchanged; EA and DEA were unchanged throughout at very low levels. The mean value for the concentration of DMA was below 200 μg/kg before curing; higher values (maximum 520 μg/kg) were found in vacuum packed stored bacon. No nitrosamines were found above the detection limit (1 μg/kg) in any of the uncooked pork or bacon.     

Physicochemical Properties of Pacific Whiting Surimi as Affected by Various Freezing and Storage Conditions

ABSTRACT: Effects of various freezing methods of surimi on the biochemical and physical properties, were examined. Stress values increased up to 3 mo and then decreased. Strain values significantly decreased over time, except freeze-dried surimi stored at -18 °C. Yellowness (b*) of the freeze-dried surimi stored at 22 °C increased significantly during storage. In addition, salt-extractable proteins (SEP) decreased while dimethylamine (DMA) increased. Freeze-dried surimi showed the highest SEP and the lowest DMA values after 9 mo storage. Electrophoretic patterns did not show any apparent damages to the MHC until 6 mo. At 6 and 9 mo, development of proteins with smaller molecular weights was observed, indicating proteolytic degradation during frozen storage.     

QUALITATIVE AND QUANTITATIVE CHANGES IN AEROBIC MICROFLORA FROM INTESTINAL CONTENTS OF SOUTH-BALTIC COD DURING STORAGE AT 1-2°C

SUMMARY— The bacterial flora of the intestinal content of cod (Gedus morrhua L) were investigated during a period of 1 year. The quantity of bacteria in recently caught fish was studied during the full period. the quality during only 6 months. 3 groups of fish from the same capture and fishing grounds were analyzed: fresh, and stored at 1–2°C for 5 and 10 days. It was seen that in general gram-positive bacterial flora dominated in recently caught fish, while after 5 and 10 days of storage gram-negative flora our numbered the former. In the intestinal contents of fresh fish the Vibrio species dominated, whereas at storage, Pseudomonas spp. became dominant. In fresh fish, the bacterial flora of stored fish amounted to 3.10% of the total initial quantity after 5 days of storage and 1.5% after 10 days. Also, the gram-positive flora decreased comparatively more rapidly than gram-negative flora. The authors believe that the temperature of 1–27°C may play a part in the decreasing number of flora, as well as some other factors not investigated in the present research.     

Semiconductive Trimethylamine Gas Sensor for Detecting Fish Freshness

Characteristics were studied on In₂O₃ treated with 5 mol% MgO responses to 300 ppm trimethylamine (TMA), dimethylamine (DMA), ammonia and other gases evolved from several different fish muscles stored under different conditions. Sensitivities of the In₂O₃-MgO sensor element were higher in order of TMA, DMA and ammonia over the operating range 330–620°C. Sensor responses were directly proportional to concentrations of TMA in fish muscle in the presence of other evolved gases, irrespective of types of fish muscle or storage time.     

Extension of the chilled storage life of smoked blue cod (Parapercis colias) by carbon dioxide packaging

Commercially prepared smoked blue cod ( Parapercis colias ), packaged aerobically, under vacuum and in carbon dioxide controlled atmosphere packs, was stored at + 3°C and - 1.5°C. Product stored aerobically on overwrapped polystyrene trays spoiled by 14 and 28 days respectively, and that in vacuum packs spoiled by 14 and 35 days respectively, when held at 3°C and - 1.5°C. In contrast, product in carbon dioxide packs remained acceptable until the 3°C and - 1.5°C storage trials ended after 49 and 113 days respectively. Microbial spoilage was first evident in overwrapped product stored aerobically and in vacuum-packed product as offensive putrid amine-like odours on pack opening. These odours were associated with the development of a predominantly Gram-negative spoilage microflora. Extension of product life afforded by the use of carbon dioxide controlled atmosphere packaging is attributable to a significant extension of the lag phase before spoilage microflora proliferation commenced and to the selection of a low-spoilage-potential lactic-acid-bacteria-dominated flora. Although the use of carbon dioxide packaging offers an export potential for chilled smoked blue cod, caution must be advocated until product safety, in respect to the growth of cold tolerant pathogens in the case of temperature abuse (>3°C), can be more fully evaluated.     

Subcellular Membrane Integrity of Atlantic Cod (Gadus morhua) Myotomal Tissue: Effects of Frozen Storage

The influence of frozen storage on the ultrastructural integrity of Atlantic cod muscle tissue membranes was investigated following three methods of freezing and retention for 12 wk at - 12°C and - 35°C. In comparison to controls (0 wk), extensive membrane condensation associated with sarcoplasmic reticulum was apparent in samples stored for 12 wk at - 12°C. The effects were observed to a much lesser extent in samples retained for 12 wk at – 35°C. It was apparent that cryogenic, plate or blast freezing techniques showed no measurable influence on the observed membrane condensation and that such ultrastructural changes resulted as a consequence of relatively high (–12°C) subfreezing temperatures.     

Shelf-life extension of cod fillets with an acetate buffer spray prior to packaging under modified atmospheres

Fresh cod fillets (Gadus morhua) were sprayed with a 10% acetate buffer (pH 5.6), packed with an industrial gas-flushing packaging machine under modified atmospheres (50% CO₂-45% O₂-5% N₂, 2cm³/1g gas/ product ratio) and stored at 7^oC for 12 days. Control cod fillets were directly packed and stored under the same conditions. A reduction of the aerobic plate counts was observed immediately after the cod fillets had been sprayed. During storage under modified atmospheres, there was complete inhibition of H₂S-producing bacteria and Enterobacteriaceae in the treated cod fillets. Production of total volatile bases and trimethylamine (TMA) was inhibited in treated fillets for 10 days' storage under modified atmospheres. Inhibition of TMA production can be attributed to growth inhibition of H₂S-producing bacteria, inhibition of the trimethylamine oxide (TMAO)-dependent metabolism of TMAO-reducing bacteria and the stable pH during storage. The shelf-life, at 7^oC, of treated cod fillets, based on cooked flavour score, was almost 12 days, ca 8 days more than shelf-life of the control fillets.     

SOME OBSERVATIONS ON MYOGLOBIN AND LIPID OXIDATION IN FROZEN BEEF

SUMMARY –The observed curvilinear correlation between metmyoglobin formation and lipid oxidation in beef gluteus medius samples (3 mm thick) stored in polyethylene at -5°C was dependent (P < 0.001) on initial treatment, namely freeze-thawing, delayed freezing or mincing. However, these initial treatments accelerated both metmyoglobin formation and lipid oxidation. In slices initially held in 1% oxygen at 0°C to increase the relative amount of metmyoglobin, the concentration of this pigment was first reduced during frozen storage at -5°C before increasing again. High initial metmyoglobin concentrations had no effect on the rate of lipid oxidation.     

不同贮藏温度下阿根廷鱿鱼内源性甲醛及相关物质的变化规律

探究不同贮藏温度下阿根廷鱿鱼内源性甲醛及相关物质的变化规律,研究了4 ℃、0 ℃、-20 ℃贮藏条件下鱿鱼体内甲醛(FA)、二甲胺(DMA)、三甲胺(TMA)、氧化三甲胺(TMAO)、氧化三甲胺脱甲基酶活性(TMAOase)、肌原纤维蛋白溶解度、菌落总数的变化。结果表明,随着贮藏时间的延长,鱿鱼体内FA、DMA、TMA和菌落总数呈现上升趋势;TMAO和蛋白溶解度呈现下降趋势;在4 ℃和0 ℃下TMAOase活性呈先上升后平缓的趋势,-20 ℃下TMAOase活性呈先上升后略微降低的趋势;各温度下的甲醛含量和氧化三甲胺脱甲基酶(TMAOase)酶活之间具有显著相关性(r4 ℃=0.791,r0 ℃=0.863,r-20℃=0.825)。本研究为不同贮藏条件下甲醛的控制提供了理论基础。     

秘鲁鱿鱼丝加工中回潮工艺的作用机理研究

回潮过程是鱿鱼丝加工中的重要工序,即将经过水煮、一次调味、渗透、干燥的鱿鱼板放入-10～-5℃的冷库冻藏,但此工序在秘鲁鱿鱼丝加工中的作用机理并不清楚,工艺参数无理论依据。本研究以盐溶性蛋白质含量、扫描电镜观察、光学显微镜观察,氧化三甲胺的变化为指标,研究了秘鲁鱿鱼丝加工半成品在-10℃回潮过程中的变化机理,结果表明,在回潮0～6d过程中,蛋白质变性明显,肌原纤维蛋白质空间结构发生改变,形成了稳定的网络结构;氧化三甲胺主要降解产生三甲胺(TMA),只产生少量的二甲胺(DMA)和甲醛(FA)。回潮最佳的时间确定为3～6d,从而为秘鲁鱿鱼丝生产提供理论依据。     

β-Carotene and Ascorbic Acid Retention in Fresh and Processed Vegetables

Broccoli, carrots, and green beans (grown in 2 consecutive years) were randomly divided into 3 treatments: fresh-refrigerated (F-R), frozen (FZ) or canned (C) (carrots only). FZ or C vegetables were processed within 24 h and stored for up to 1 yr. F-R vegetables were held at 4 °C for 3 wk (broccoli and green beans) or 6 mo (carrots). Trans b-carotene (Tb-C) and total ascorbic acid (AA) were determined at specified times, before and after microwave cooking. Vitamin content differed between years due to environmental conditions. Blanching resulted in AA loss, but retention remained stable after freezing broccoli and green beans. F-R green beans lost >90% AA after 16 d storage. Linear decreases in AAwere found in most F-R or FZ vegetables. Tb-C decreased slightly during freezer storage. Reductions in Tb-C occurred in canned carrots. Microwave cooking had minimal effects on AA or Tb-C.     

Sarcoplasmic Reticulum Ca2+-ATPase and Cytochrome Oxidase as Indicators of Frozen Storage in Cod (Gadus morhua)

ABSTRACT: Activities of 2 membrane-bound enzymes, Ca²⁺-ATPase from the sarcoplasmic reticulum and cytochrome oxidase from the inner mitochondria membrane, were measured during frozen storage of cod. Enzyme activities were higher in cod muscle samples frozen at −30°C than at −20°C. Freezing-induced activation of both enzymes was observed and the activation was amplified by ice storage prior to freezing. Sensory evaluation conducted at 9 mo of frozen storage showed differences between the sensory properties of cod frozen immediately after catch and frozen after 3 d of storage on ice. These results indicated that the enzymes might be useful as indicators of quality changes by frozen storage.     

Freezing tilapia by airblast and liquid nitrogen – freezing point and freezing rate

Processing data was obtained for the freezing of tilapia meat. The initial freezing point of tilapia meat was measured by differential scanning calorimetry (DSC), and also by measuring the centre temperatures of meat chunks during cooling. the freezing point was −1.03°C by DSC, and between −0.81 and −0.90°C by the cooling method, determined at the point where the standard deviation of the mean temperature was close to zero, i.e. a minimum.
Tilapia chunks, 0.95 to 1.45 cm thick, were frozen in an airblast freezer at −7, −20 and −36°C, and in a liquid nitrogen freezer at −87 and −128°C.
Freezing rate, defined as the half thickness of a meat chunk divided by the time for the centre temperature to decrease from 0 to −5°C, was 0.09 cmh⁻¹ at −7°C. At freezing temperatures of −20, −36, −87 and −128°C, the rates were respectively 4, 19, 158 and 331 times faster than that at −7°C, and correlated with freezing temperature ( r = 0.99) regardless of the freezing method.