The bacteriology of fresh and spoiling Lake Victorian Nile perch (Lates niloticus)

A total of 177 bacterial cultures isolated from Lake Victorian Nile Perch (Lates niloticus) were investigated. The flora on newly caught Nile perch consisted of organisms belonging to the genera Moraxella, Alcaligenes, Acinetobacter, Pseudomonas, Aeromonas, Micrococcus and other Gram-positive organisms. 39% were identified as Gram-positive species and 61% were negative in the Gram-reaction. Three cultures out of 53 investigated caused weak rotten off-odours in sterile fish broth and one culture, an Aeromonas spp. produced strong rotten, fishy, hydrogen sulphide off-odours. From Nile perch spoiled at ambient temperature, 15 of the 42 strains isolated caused rotten, fishy, hydrogen sulphide off-odours. These specific spoilage bacteria were all identified as Aeromonas and all reduced trimethylamine oxide to trimethylamine and produced hydrogen sulphide. From spoiled iced Nile perch, 74 out of 82 (90%) of the bacteria isolated were identified as Pseudomonas. A small proportion of these (13 out of 74) produced off-odours in sterile fish broth resembling the spoiling fish. These specific spoilers could not be separated from the non-spoilers based on biochemical activities used in classical taxonomy. While the Pseudomonas spp. isolated did not produce trimethylamine or H₂S, a few of the remaining isolates (two Shewanella putrefaciens and five Aeromonas spp.) did produce these compounds. The role of Shewanella putrefaciens in the iced spoilage of Nile perch was, however, insignificant, since they only very late in the storage reached numbers where their spoilage could be detected.     

Manipulation of fatty acid composition of Nile tilapia (Oreochromis niloticus) fillets with flaxseed oil

Nile tilapia (Oreochromis niloticus) is one of the most consumed species among freshwater fish reared in Brazil. However, studies show low levels of n‐3 fatty acids in freshwater fish reared in captivity in comparison with those reared in their natural habitats. The Nile tilapia used in this study were raised in captivity for a period of 5 months and fed varying amounts (0, 1.25, 2.5, 3.75 and 5%) of flaxseed oil as a substitute for sunflower oil (control). No significant differences (P > 0.05) in total lipid (TL) content were found between fillets of tilapia fed the different diets. TL analysis of fatty acid methyl esters by capillary gas chromatography revealed a total of 50 components common to all treatments studied. The major fatty acids present were linoleic acid (18:2n‐6), oleic acid (18:1n‐9) and palmitic acid (16:0). All treatments led to significant % increases in α‐linolenic acid (18:3n‐3), eicosapentaenoic acid (20:5n‐3) and docosahexaenoic acid (22:6n‐3). Increases in both total n‐3 fatty acids and total polyunsaturated fatty acids were observed concomitantly with decreases in total n‐6 fatty acids, resulting in increases in n‐3/n‐6 ratio, with increasing level of flaxseed oil in the feed. Thus feed supplementation with flaxseed oil contributed greatly to raising the nutritional lipid value of Nile tilapia fillets. Copyright © 2007 Society of Chemical Industry     

Carcass characteristics and meat quality of broilers fed periwinkle flesh (Pachymelania aurita), palm kernel cake and oil‐based rations

The effect of supplementation of palm kernel oil in periwinkle flesh and palm kernel cake‐based diets on carcass characteristics and meat quality of broilers was evaluated. Birds were assigned to five dietary treatments in a completely randomized design. The first diet, which was the control, contained 20 mg kg^?1 fishmeal but it did not contain palm kernel cake and periwinkle flesh. The second diet contained 20 mg kg^?1 fishmeal, 250 mg kg^?1 palm kernel cake but no periwinkle flesh. The third diet contained 60 mg kg^?1 periwinkle flesh, 250 mg kg^?1 palm kernel cake and no fishmeal. Present in the fourth diet were 250 mg kg^?1 palm kernel cake, 30 mg kg^?1 periwinkle flesh, no fishmeal and 20 mg kg^?1 palm kernel oil. Similarly, the fifth diet contained 250 mg kg^?1 palm kernel cake, 30 mg kg^?1 periwinkle flesh, no fishmeal and 40 mg kg^?1 palm kernel oil. Carcass measures and cuts were significantly influenced (P < 0.05) by dietary treatments. Diets 2, 3 and 5 gave significantly higher plucked dressed weights, total edible meat and total bone weights, respectively. Also carcass cuts were significantly increased (P < 0.05) in birds on periwinkle and palm kernel oil diets, with abdominal fat being highest in diet 5 having 40 mg kg^?1 palm kernel oil. However, proximate composition, physical and sensory properties were not significantly (P < 0.05) influenced by dietary treatment. Results showed that carcass characteristics improved as compared to the control group. Copyright © 2005 Society of Chemical Industry     

美国胴体产量方程对我国牛胴体产肉量评定的适用性研究

用ＳＡＳ软件对７头商品牛的屠宰数据进行了统计分析,通过产肉率方程的估算值与实测值的相关分析,初步认为,以第１１肋后缘截面指标套用美国胴体产肉率方程估算我国牛胴体产率是不可行的。     

Carcass characteristics and meat quality of male and female foals

This research was conducted to characterize the carcass traits and meat quality of 16-month and 24-month old foals (33 males and 23 females) reared in two different livestock production systems. The carcass parameters assessed were conformation, degree of fatness, morphology, weight and carcass meat colour. The physicochemical characteristics and sensory profile of the M. longissimus dorsi (LD) were determined at 4 days of ageing. The carcass parameters and meat quality traits differed little between colts and fillies. There were significant differences between production systems. Carcasses were characterized by B conformation, 3 of fatness and high dressing percentages (>63%). Foal meat had a high myoglobin content and there were differences between the production systems in the flavour, juiciness, flourness and greasiness of the LD.     

Effect of chitosan–Jicama starch coating on changes in qualities of fresh Nile tilapia (Oreochromis niloticus) fillets during ice storage

The effect of chitosan (0.5%)/Jicama starch (0%–4%)‐based edible coating on the quality of Nile tilapia (Oreochromis niloticus) fillets was evaluated over ice storage time. All samples were periodically analysed for pH value, thiobarbituric acid (TBA), total volatile basic nitrogen (TVB‐N), electrical conductivity (EC), total viable counts (TVC), total psychrotrophic counts (TPC), drip loss, colour, hardness and sensory characteristics. Results demonstrated that the quality of Nile tilapia fillets was preserved by the film containing chitosan and/or Jicama starch. Compared with chitosan coating alone (0.5% chitosan/0.25% glycerol) (P < 0.05), T3 (0.5% chitosan/1% Jicama starch/0.25% glycerol) had a better effect on the drip loss, TBA, TVC, TPC, hardness and sensory characteristics of the samples, thus indicating that low Jicama starch concentration (1%) enriched the coating ability of chitosan in extending the shelf life of Nile tilapia fillets.     

Development of a freeze‐dried mixture of Nile tilapia (Oreochromis niloticus) croquette using a GA‐based multiobjective optimisation

BACKGROUND: The mechanically separated meat (MSM) of Nile tilapia is an example of a by‐product that can be used in the development of new foods. The aim of this study was to optimise the mixture of different flours in the development of a freeze‐dried mixture of fish croquette using Nile tilapia MSM. Flavour, texture and overall acceptance of seven formulations were evaluated by an acceptance test. A genetic algorithm (GA) with desirability functions was combined with a multiobjective optimisation of the response surface models. RESULTS: The combination of flours was chosen to minimise cost and maximise overall acceptance and fibre content. Overall acceptance showed a statistically significant correlation (P?0.05) with flavour (r = 0.67) and texture (r = 0.61). The GA‐based approach indicated that the highest overall acceptance was obtained when using wheat and rye flours in equal parts. This formulation had an overall acceptance of 7.52, a fibre content of 11.50 g kg^?1 and a cost of US$ 2.21/kg. After 24 h of freeze‐drying, the water activity of the mixture was 0.11. CONCLUSION: The GA‐based approach was able to optimise the croquette formulation. The freeze‐drying process contributed to the development of a value‐added product with high quality and long shelf‐life. © 2012 Society of Chemical Industry     

Original article: Optimisation of extraction conditions and characteristics of skin gelatin from Nile tilapia (Oreochromis niloticus)

Response surface methodology was used to optimise gelatin extraction conditions from the skin of Nile tilapia (Oreochromis niloticus), and characteristics of the gelatin were determined. Concentration of NaOH (%, X₁), alkaline treatment time (h, X₂), concentration of HCl (‰, X₃) and acid treatment time (min, X₄) were chosen for independent variables. Dependent variable was yield of gelatin (%, Y). Optimal conditions were X₁ = 3.2 (%), X₂ = 2.3 (h), X₃ = 0.7 (‰) and X₄ = 84 (min), and predicted value of response optimal conditions was Y = 20.4%. Actual value was 19.3% by verification experiments under optimal conditions. Crude protein content of the tilapia skin gelatin was 88.5%. The content of imino acids including proline and hydroxyproline in the gelatin was 185 residues per 1000 total amino acid residues. Its gel strength was 260 g. The gelling and melting points were 18.0 and 22.4 °C, respectively.     

Carcass composition and meat quality of brush-tail possums (Trichosurus vulpecula)

One-hundred-and-thirty-nine possums, balanced as far as possible for sex (68 male, 71 female) and age (1 year, 42; 2-4 years, 61; 5+ years, 36), were slaughtered and the dissected carcass composition, muscle, and cooked meat composition measured. Possums were slaughtered at time in captivity TIC 0 (n = 58), TIC 14 days (n = 20) and TIC 28 days (n = 61). Compared with the 5+ years (mature) age group the 1 year olds (juveniles) were 67% and the 2-4 year olds (immature) 96% of the live weight of the mature possums. Carcass composition was characterised by high lean (78-80%) and low fat (around 1-2%). The cooked meat from possums is very high in protein (～ 25%) and low in fat, suggesting it should be a valuable source of animal protein with a low total fat, high unsaturated fat content. In all cases cooked meat was rated as tender, based on shear force values, despite having a pH of around 6·3.     

Effects of Carcass Weight Class and Postmortem Aging on Carcass Characteristics and Sensory Attributes in Grain-Fed Veal

ABSTRACT Thirty-six Holstein bull calves were used to examine the effects of carcass weight and postmortem aging on carcass characteristics and sensory attributes of grain-fed veal. Three carcass weight classes (hide-on) included light (< 165 kg), medium (177 to 186 kg), and heavy (195 to 204 kg) with 12 animals per class. Postslaughter, longissimus (LM) and semimembranosus (SM) roasts were aged for 2, 7, and 14 d. Carcass characteristics were generally similar (P > 0.10) across weight class. Weight class did not affect (P > 0.10) tenderness in LM or SM or flavor in LM. Longissimus muscle from light weight carcasses were juicier (P < 0.07) than heavier carcasses while flavor was lower in SM for medium compared with heavy carcasses. Aging tended to increase (P < 0.100) tenderness attributes for LM and SM. Veal flavor increased (P=.014) with 7 d aging for LM. Postmortem aging should be considered for routine processing of veal to improve meat quality.     

利用罗非鱼卵黄原蛋白建立雌激素污染的检测方法

目的以尼罗罗非鱼为实验对象,以卵黄原蛋白(Vg)为生物标志物开发环境雌激素的生物检测技术。方法采用凝胶过滤与离子交换层析相结合的方法从17β-雌二醇诱导后的罗非鱼血浆中分离纯化Vg,对纯化的蛋白进行鉴定后制备多克隆抗血清,建立Vg的酶联免疫吸附测定实验(ELISA),并用于样品测定。结果建立的ELISA工作范围为15.6~1000 ng/m L,组内与组间差异分别为6.85%与6.79%,能有效检测100、500、1000μg/L双酚A对雄鱼血浆Vg的诱导效应。结论本研究建立的Vg ELISA具有较高的敏感度、特异性与精确度,可为水体环境雌激素污染检测提供重要工具。     

Carcass characteristics and meat quality of halothane negative and halothane positive pietrain pigs

One hundred and seventy-six Pietrain pigs were tested for halothane sensitivity by means of a 5-min halothane anaesthesia in two experiments. One hundred and twenty were halothane negative (HN) and 56 were halothane positive (HP). In one experiment pigs were slaughtered under commercial (stress) conditions; in the other experiment pigs were killed under minimal stress conditions.

The carcasses of HP pigs were meatier and shorter and contained 2·2% more muscle than the carcasses of HN pigs.

Halothane positive pigs gave a meat of poorer quality, as assessed in the fresh state. When the pigs were slaughtered under commercial conditions, hams from HP pigs were not inferior in curing ability and had a higher total processing yield of Paris ham due to their higher trimming yield. When the pigs were killed under minimal stress conditions, there was no difference in the total processing yield betwen HN and HP pigs, because the technological yield was markedly reduced in HP pigs. However, in both cases, HP pigs produced more cooked ham per pig.

It is suggested that different physiological mechanisms may account for either PSE (pale soft exudative) or DFD (dark firm dry) meat. The former is the consequence of an excessively high rate of post mortem glycolysis which is clearly manifest in HP pigs when they are killed under minimal stress conditions and the latter appears to be unrelated to halothane sensitivity as the ultimate pH of HP and HN pigs is similar when the animals are slaughtered under stress conditions.     

Carcass characteristics,meat quality and nutritional value of horsemeat: A review

Meat has exerted a crucial role in human evolution and is an important component of a healthy and well balanced diet due to its nutritional richness. The aim of the present review was to shed light on the nutritional composition of horsemeat and their benefits for human health. One of the reasons for such interest was the occurrence, in Europe several years ago, of dioxin, Bovine Encephalopathy and foot-and-mouth disease problems in farm animals. Therefore, consumers began to look for alternative red meats from other non-traditional species. There is no carcass classification system on horses designated to meat consumption. It would be advisable to standardize the equine meat market to reduce variations that may reflect differences in meat quality. The nutritional composition of horsemeat by comparison with pork, beef or poultry is characterized by low levels of fat and cholesterol (about 20% less), relatively high concentrations of n− 3 fatty acids and heme iron indicating that its consumption may be beneficial for health. Therefore, horsemeat may supplement the meat market with good quality products, although as in other dietary components moderation is advisable.     

Selenium fractionation from plasma, muscle and liver of Nile tilapia (Oreochromis niloticus)

This paper presents the results obtained from selenium fractionation in plasma, muscle and liver samples of Nile tilapia’s (Oreochromis niloticus) after protein separation. The plasma, muscle and liver proteome was obtained by 2D-PAGE, and selenium in protein spots was qualitatively and quantitatively determined by synchrotron radiation X-ray fluorescence and graphite furnace atomic absorption spectrometry (GFAAS). The fluorescence spectra indicated the presence of selenium in three protein spots of plasma, two of muscle and one of liver. Selenium was found to be distributed mainly in proteins with a molar mass smaller than 57.0 kDa and with pI in the range of 5.9–9.6, with one exception in the plasma sample, which presented protein with a molar mass of 60.0 kDa. After acid mineralization of the protein spots, a GFAAS determination of the concentration of selenium bound to these proteins indicated a range of 1.35–6.82 mg per g of protein.