Dry Meat Research Articles

Influences of temperature, salinity and available food upon suspended culture of the Pacific oyster, Crassostrea gigas: I. Absolute and allometric growth

Growth of oysters was measured at 10 locations in British Columbia, Canada, over a 14-month period. Three categories of site-related growth were defined by comparisons of growth curves for different body variables. In high growth sites, oysters had greatest increases in shell height and weights of whole oyster, shell and dry meat which were attributed to high phytoplankton biomass (chlorophyll a) and suitable temperature and salinity regimes. Oysters in medium growth sites had significantly lower growth in shell height and dry meat weight but equivalent whole and shell weight growth to high growth sites. Temperature and salinity regimes were suitable for oysters at these sites but overall phytoplankton biomass was low. At low growth sites, growth in all body variables was reduced because periods of high food availability coincided with suboptimal salinity conditions (< 20 ppt). Comparisons of site-specific allometric regression equations fitted to log 10 transformed dry meat weight and shell weight data were not different between low and high growth sites, however, oysters at medium growth sites had significantly less dry meat weight in relation to shell weight. We suggest that under prolonged periods of low food supply, oysters preferentially partition energy resources toward increasing shell weight and thickness over body tissue weight. This response may be inhibited under conditions of low salinity because of reduction of assimilated ration and possible limitations upon the supply of minerals essential to shell formation.

Influences of temperature, salinity and available food upon suspended culture of the Pacific oyster, Crassostrea gigas: II. Condition index and survival

Condition indices, dry meat weight:dry shell weight ratio and dry meat weight:internal volume ratio, and survival rate were determined for a common broodstock of oysters grown in 10 locations in British Columbia, Canada, over a 14-month period. Year 0 oysters (20–30 mm initial shell height) had lower overall survival rates (31.5–57.3%) than Year 1 oysters (40–50 mm shell height) (63.2–89.7%) although for a given age-class, differences in survival between most sites were not great. Most oyster mortalities occurred in the initial 2–3 months according to seasonal and annual instantaneous mortality rates. Monthly dry meat weight:internal volume condition index values did not appear to be related to site-related trends in growth rate. Dry meat weight:dry shell weight ratio was a more suitable index for assessing the condition of oysters provided available food and water temperature were the principal factors affecting growth. Slow growing oysters from areas with low salinity (< 20 ppt) had dry meat weight:shell weight ratios equivalent to those of rapidly growing oysters from areas with conditions of high salinity and abundant food supply. Intra-site correlations between the two condition indices were poor. Multiple regression analysis revealed that dry meat weight:internal volume ratio was primarily correlated to whole weight and secondarily to water temperature, salinity and chlorophyll a concentration ( r 2 = 0.39, P ≤ 0.001). Dry meat weight:dry shell weight ratio was correlated to the same environmental factors but not whole weight ( r 2 = 0.41, P ≤ 0.001). Ecophysiological studies of oysters should not rely extensively upon results of condition index analysis, particularly involving volume measurements, unless there are collaborating growth and environmental data.

Enzyme Immunoassay for Detection of Salmonella in Low-Moisture Foods: Collaborative Study

A collaborative study was performed in 15 laboratories to evaluate a modification of the enzyme immunoassay (EIA) method for detection of Salmonella in foods (46.B21-46.B29). The modified EIA requires 18-24 h pre-enrichment, 6-8 h selective enrichment, and 14-18 h M-broth post-enrichment prior to performing the assay, which requires 1-2 h. Total assay time is 40-52 h. The modified method was compared with the standard culture method for detection of Salmonella in 5 low-moisture foods: nonfat dry milk, milk chocolate, meat and bone meal, dry whole egg, and ground pepper. The modified method has been adopted official first action for use with low-moisture foods.

Condition index, meat yield and biochemical composition of Crassostrea brasiliana and Crassostrea gigas grown in Cabo Frio, Brazil

Samples of tray-grown Crassostrea gigas from imported seed and of the closely related Crassostrea brasiliana from a local natural population in tropical waters of Brazil were examined monthly during a 4-year period. Parameters of condition, including the condition index, wet meat yield and gross biochemical composition, were determined and seasonal and annual differences assessed. It was concluded that C. gigas harvested in their first year of growth compared favourably in quality with the native species. Condition varied seasonally and in both species highest values were during the summer when coastal waters were influenced by the upwelling of relatively nutrientrich water. Median condition indices were 79.4 for the native oyster and 72.3 for C. gigas. The lower median value for C. gigas was related to the predominance of larger animals in samples; there being a significant relationship between animal size and condition index ( P<0.001). C. gigas which grew to 100 g live weight in 1 year yielded about 11 g wet meat whereas the largest C. brasiliana at 42 g live weight yielded 5.3 g wet meat. Glycogen values as a percentage of dry meat weight peaked at 16% in October in the native species and 12.5% in December in C. gigas. The potential for the culture of C. gigas in the tropical region of Brazil is discussed.

Quality characteristics of ostrich meat

The quality of ostrich meat was evaluated according to final pH value, histological sections, collagen content and solubility, muscle-fibre diameter and sarcomere length, pigment content, cooking loss and water-binding capacity, shear-force value and taste-panel evaluation. Where possible, these values were compared with comparable values obtained from beef. The average final pH value of the ostrich meat was 6,06, indicating Dark, Firm and Dry (DFD) meat which may have resulted from the slaughtering of exhausted animals. Large intracellular vacuoles were found in histological sections, probably due to the slow freezing of the meat.

Condition and variability in Mytilus edulis (L.) from different habitats in Ireland

Twenty-one samples of Mytilus edulis L., taken from three habitats; commercial rafts, commercial subtidal beds, and non-commercial intertidal regions, were examined. Three condition indices: dry meat weight/internal volume, shell weight/internal volume, and dry meat weight/shell weight; and two morphological ratios: internal volume versus length and shell weight versus length, were calculated for each sample. The relative weight of the shells increased and the meat weight decreased, as we examined samples from rafts, subtidal, and intertidal regions, in that order. The size-related increase of shell weight was relatively greater than the increase of volume in intertidal mussels, in contrast to raft mussels. These findings agree with the commercial practice of relocating mussels to subtidal beds to improve their meat yield. There were no significant clines in the data associated with geographical location, although there were very marked local variations in all factors measured. Variability was as great in raft mussels as in wild intertidal ones. Meat weight was consistently more variable than shell weight, and these two variabilities were not correlated. Because of the strong local variation reflected in the significantly different values for the ratio meat weight/shell weight, in virtually all populations, we concluded that comparisons of stocks or growth must be carried out in the same location to have any validity.

EFFECTS OF FASTING AND WATER RESTRICTION ON CARCASS SHRINK AND PORK QUALITY

One hundred and twenty market weight (90 kg) pigs were allocated at random to one of three treatments: immediate slaughter and 24 h or 48 h without feed or water after arrival at an abattoir. All pigs were removed from feed 17 h before arrival at the abattoir. Weights of body organs and the digestive tract full and emptied of digesta were recorded along with warm carcass weight. After chilling for 24 h a pork chop 25 mm thick was removed along with the commercial ham and belly from the left carcass side and frozen for later quality determinations. Live weight shrink over 48 h amounted to 6.8 kg with 75% (5.1 kg) of this loss being attributed to loss in carcass weight. The 24-h holding period also resulted in a significant loss in carcass weight (3 kg). Approximately 20% of the total shrink over 48 h was due to a reduction in digestive tract contents. Body organs showed little change in weight over the 48-h holding period apart from the liver which was reduced in weight by 14.6%. Final longissimus muscle pH was increased and muscle luminosity (fresh longissimus, cured m. semimembranosus and m. biceps femoris) decreased for both the 24-h and 48-h holding treatments but did not result in any dark, firm and dry meat. Drip loss in pork chops decreased with increased ante-mortem holding time. However, processed yields for hams and bacon were not significantly influenced by the holding period pre-slaughter. It was concluded that the time from last feeding to slaughter should be minimized to avoid losses in carcass weight and slightly darker fresh and processed meat. Key words: Fasting, carcass shrink, carcass quality, processed yield

DIMENSIONING OF A MASS ALGAL CULTURE FACILITY FOR THE TEMPERATE ZONE NURSERY CULTURE OF BIVALVE MOLLUSCS

ABSTRACTAquacultural Research Corporation (ARC) has operated a continuous mass algal culture facility for the nursery culture of the hard clam (Mercenaria mercenaria) for twenty years. Procedures have been developed for the mass culture of selected species of microalgae that are of proven nutritional value for rearing bivalve spat. Within the past three years a 60% increase in algal yield has been achieved by selection of small centric diatoms for mass culture and by empirical determination of optimum depths and seasonal dilution rates for the light limited 40 m3 continuous cultures. Cell densities of the diatoms Thalassiosira pseudonana (3H) and Skeletonema sp. have averaged over 109 cells/liter from March through November. The algal pond surface area necessary to support a hypothetical nursery with a monthly average clam biomass of 8 kg dry meat weight (ca 13 × lo6 clam seed) was calculated for latitude 41°N during the four seasons of the year. These calculations were based on 1982–1983 algal yields and an assumed food chain efficiency of 10%. The required minimum algal pond surface area ranged from 192 m2 in summer to 750 m2 in winter. The current ARC nursery operation is compared with this hypothetical model. Costs of nursery seed production and a proposed strategy for minimizing the seasonal algal areal requirements of a temperate zone bivalve nursery are discussed.

Effects of reaction variables on the hydrolysis of lean beef tissue by alcalase

The effects of the reaction variables, pH, time, temperature, enzyme: meat ratio and meat concentration, on the hydrolysis and solubilisation of lean meat protein by Alcalase have been determined. Experiments were performed with both dilute meat suspensions and undiluted ground meat. Reaction progress curves were similar to those for the enzymic hydrolysis of other proteins, with rapid initial reaction rates followed by a gradual decline in rate. The optimum reaction pH was 8·5. Optimum temperatures were found to be 55°C for the hydrolysis reaction and 60°C for meat solubilisation. Both solubilisation and degree of hydrolysis increased with increasing enzyme concentration. At an enzyme: meat ratio of 80 mg Alcalase 0·6L per gram of dry meat, a solubilisation of 94% and a degree of hydrolysis of 18% were achieved after a 3-h reaction period. As meat concentration was increased, degree of hydrolysis decreased slightly and solubilisation decreased markedly.

The effects of sediment type on growth rate and shell allometry in the soft shelled clam Mya arenaria L

Hatchery-reared juvenile Mya arenaria L. were grown for 11 wk in replicated gravel, sand, mud, and pearl net treatments under flow-through sea-water conditions in Maine. Analyses of variance showed significant differences between sediment treatments for final shell length, dry meat weight, chondrophore growth increment, and percent shell weight. Growth of juvenile M. arenaria was more rapid in fine sediments than in coarse sediments or nets. Regression slopes of shell length-shell height and shell length-shell depth varied significantly between sediment treatments. Slower-growing clams from nets and gravel were more globose than clams from sand or mud treatments. Clams grown in sand were longer and narrower than those from mud. Differences in growth rates and shell form were attributed primarily to the physical properties of the substrata, and their effects on the scope for growth of M. arenaria.

Detection of glucose oxidation products in chilled fresh beef undergoing spoilage.

The fate of nutrients during storage of longissimus dorsi muscle at 4 degrees C was examined. Glucose concentrations in meat were shown to decrease concomitantly with an approximately fourfold increase in the activity of glucose dehydrogenase. Gluconate concentrations in meat were determined by an enzyme assay and shown to increase from 2.1 to 40.6 microgram/g upon storage of the meat from day 0 to day 6. At day 12, gluconate concentrations had decreased to 5.8 microgram/g. Dark firm dry meat, which contains little or no glucose, did not exhibit the same rise and fall in gluconate concentration. Thin-layer chromatographic analysis confirmed the presence of 2-ketogluconate in 6- and 12-day-old longissimus dorsi muscle that had been stored at 4 degrees C. Gluconate concentrations in irradiated sterile meat inoculated with Pseudomonas fluorescens increased from 4.2 to 77.8 microgram/g during the first 6 days of storage at 4 degrees C. Therefore, glucose in meat stored at 4 degrees C appeared to be converted to gluconate, 2-ketogluconate, or both extracellularly by one of the main meat spoilage organisms, most likely the pseudomonads.

Seasonal Variation in the Chemical Composition and Condition Indices of Pacific Oyster, Crassostrea gigas, Grown in Trays or on the Sea Bed

Chemical composition and condition indices of tray and bottom-cultured Pacific oyster, Crassostrea gigas, were measured and compared over a 13-mo period. Tray oysters were less dense than bottom oysters as a result of increased porosity of shells. Dry meat condition indices were slightly higher in oysters grown in trays. Chloride and iodide levels peaked in early spring. Minor seasonal deviations occurred from the mean 61.0% polymeric matter, 31.5% hydrophilic matter of low molecular weight, and 7.5% lipid matter in both groups of oysters. Nonprotein to protein nitrogen ratio in tray and bottom oysters averaged 0.37 and 0.35, respectively, throughout the season. A procedure was developed to assess glycogen in situ in polymeric material fractionated from meat. Glycogen averaged 79.5 and 79.0% of the total glucose in tray and bottom oysters, respectively; the remainder consisted of the homologous series of α(1 → 4)-linked D-glucose oligomers. Degree of polymerization of oligosaccharides in tray and bottom oysters averaged 2.93 and 2.91, respectively. Dry meat condition indices correlated predominantly with protein condition indices, only secondarily with glycogen condition indices and insignificantly with the remaining constituent condition indices of tray and bottom oysters.Key words: Crassostrea gigas, tray and bottom cultures, chemical composition, nitrogen, carbohydrates, halides, density, condition indices, seasonal variations

Changes in the colour and opacity of meat

On exposure to oxygen the purple ferrous haem pigment, myoglobin, forms the bright red covalent complex, oxymyoglobin. In fresh meat oxidation of oxymyoglobin to metmyoglobin, the unattractive brown pigment, is affected principally by the reducing capacity of the muscle, oxygen availability and temperature. In frozen meat, light is the major factor affecting the oxidation rate. Oxidation of nitric oxide myoglobin, the ferrous pigment in cured meats, is prevented by excluding oxygen but proceeds rapidly in light, if oxygen is present. Stress, pre-slaughter handling of the animal and post-slaughter treatment of the carcass affect the light scattering properties of the meat. Glycogen depletion in the live animal results in translucent, dark firm and dry (DFD) meat with high pH and high oxygen uptake. Rapid post-mortem glycolysis causes structural changes in muscle which becomes opaque, pale soft and exudative (PSE). Electrical stimulation of the carcass and the rate of chilling also affect light scattering of meat. On storage, increase in light scatter is accompanied by a decrease in colour stability.

MARICULTURE POTENTIAL OF SHALLOW‐WATER BAHAMIAN BIVALVES

ABSTRACTA survey of shallow‐water bivalves of the Bahamas has revealed numerous under‐utilized species. This study investigates the general ecology and mariculture potential of two large species, Asaphis deflorata and Codakia orbicularis.Population studies indicate patchy but often dense (28/.25 m2) assemblages of C. orbicularis in muddy intertidal creeks and turtle grass beds. A. deflorata is found in concentrations up to 64/.25 m2, usually in sandy gravel.Linear relationships of shell dimensions are correlated with total wet weight for both species over a range of shell sizes. Measurements of shell weight, meat plus liquor, and dry meat are related to shell length and total wet weight for C. orbicularis. Compositional analysis of C. orbicularis shows meats high in protein, carbohydrate, and calories, but very low in cholesterol.C. orbicularis exhibits peaks of gonad ripeness in spring and late fall, with a large percentage of the population remaining ripe throughout the summer. Maximum periods of gonad ripeness occur in July for A. deflorata. Adults of both species were induced to spawn in the laboratory and these larvae reared through metamorphosis.Deposit‐feeding bivalve clams are suggested as mariculture candidates due to the lack of phytoplankton biomass in Bahamian coastal waters. The discovery of clams having potential for chemoautotrophic nutrition through a relationship with procaryotic cells within the gill tissue introduces exciting possibilities for mariculture.

The Determination and Use of Condition Index of Oysters

Oyster condition measures should be standardized through use of Hopkins’ formula: Condition Index = (dry meat weight in g) (100)/(internal cavity volume in cm3). Cavity volumes, previously measured chiefly as capacity by a water displacement method, may be determined by subtracting the weight in air of the oyster’s valves from the weight in air of the intact oyster (both in g). This method is valid because the effective density of cavity contents is close to 1g per cm3. The technique is simple and time-efficient and could promote more widespread use of oyster condition studies.

The American Oyster as a Coastal Zone Pollution Monitor: A Pilot Study

The Condition Index [(dry meat weight)(100)/(internal cavity volume)] has been analyzed and compared in the American oyster,Crassostrea virginica, from two South Carolina estuaries, one of which was considered polluted by coliform bacteria standards. During the warmer months, oysters from the unpolluted habitat showed a consistently and significantly higher Condition Index. Best fit and power function regressions of Condition Index on total coliform bacteria levels conform with previously cited effects of pollutants on oysters. Condition Index droped markedly as the incidence of total coliforms increased toward levels of 100 per 100 ml of water. Our results and the known sensitivity of oysters to a spectrum of pollutants suggest that their condition could be used to monitor waterborne pollution in coastal zone areas.

The microbiology of DFD fresh meats: A review

Muscle which is deficient in glycogen because of exercise or stress prior to slaughter produces dark, firm, dry (DFD) meat. Such meat is characterized by a high ultimate pH (>6·0) and deficiencies in glucose and glycolytic intermediates. These factors can result in bacterial spoilage becoming evident at an early stage of growth of the meat flora. Spoilage becomes apparent when bacteria attack amino acids. This does not occur under aerobic conditions until bacteria exhaust the glucose at the meat surface. However, since glucose is absent in DFD meat, amino acids are utilised without delay and spoilage becomes evident at lower cell densities than in normal meat. The absence of glucose also allows the anaerobic flora to produce spoilage odours at an early stage. Additionally, the high pH of DFD meat allows growth of potent spoilage organisms which are inhibited at the usual ultimate pH of meat. Early aerobic spoilage can be prevented by the addition of glucose, but prevention of early anaerobic spoilage requires the addition of a citrate buffer which reduces the surface pH, as well as providing a carbohydrate substrate which is utilised in preference to amino acids. Comparisons can be made between spoilage of DFD red meat and spoilage of white meats from poultry and fish, which normally have a high ultimate pH.

Growth of the bay scallop, Argopecten irradians, in a waste recycling aquaculture system

Growth of the bay scallop Argopecten irradians in a pilot scale waste recycling aquaculture system was examined over a 32-week-period at 14°C. A. irradians increased from initial live and dry meat weights of 1.15 g and 0.043 g, respectively, to terminal values of 9.08 g and 0.599 g, respectively. This corresponds to instantaneous growth rates for live weight ( G) and dry meat weight ( M) of 0.009 and 0.013, respectively. High mortalities were evident towards the end of the experiment with a terminal value of 33% giving an instantaneous mortality rate ( Z) value of 0.0016. In laboratory experiments of 12 weeks duration at, 12, 15, 18 and 21°C juvenile A. irradians gave values of 0.01, 0.013, 0.018 and 0.016 for G; 0.015, 0.015, 0.016 and 0.013 for M; and 0.038, 0.038, 0.037 and 0.040 for Z at the respective temperatures. Shell deformities were evident in laboratory grown individuals. A. irradians exhibits specific growth rates comparable to or higher than those previously recorded for other bivalve species cultured in waste recycling systems; however, a considerable reduction in the presently high mortality rate will be required to make A. irradians a prime candidate for practical application.

Efeitos do caranguejo Pinnotheres ostreum em ostras Crassostrea rhizophorae

Some biological parameters of the oyster (Crassostrea rhizopharae), during the spawning and post-spawning periods, were analised in relation to the infestation by the pea crab (Pinnotheres ostreum) The biological parameters considered were: size, total weight, wet and dry meat weight, and condition index. Utilizing the χ2 test these parameters and infestation by the pea crab were shown to to be associated. The incidence of pea crabs was higher during the spawning period than in the post-spawning period, reaching a maximum (20.3% infestation) in oysters with a size of 6 to 7 cm. The values of the condition index and percent of meat (wet and dry weight) for these oysters were significantly (P < 0.05) lower than for uninfested oysters. From these results there seems to be no doubt that the pea crab (V. ostreum) injures the mangrove oysters which supports the conclusion that these crabs are true parasites for C. rhizophorae.

Control of spoilage in vacuum packaged dark, firm, dry (DFD) meat

SummaryEarly spoilage of vacuum‐packaged DFD meat, due to green discoloration and development of undesirable odours and flavours, can be prevented by addition of small quantities of citrate buffer to the meat before packaging. This treatment extends the storage life to that of vacuum‐packaged normal meat, both appearance in the pack and flavour being acceptable after 12 weeks storage at –1°C. However, steaks cut from the vacuum‐packed primal cuts remained darker in appearance than normal pH controls and spoiled more rapidly during aerobic storage.