Development of an amperometric hypoxanthine biosensor for determination of hypoxanthine in fish and meat tissue

A hypoxanthine (Hx) biosensor based on immobilized xanthine oxidase (XO) as the bio-component was developed and studied for the rapid analysis of fish (sweet water and marine) and goat meat samples. The biosensor was standardized for the determination of Hx in the range of 0.05 to 2 mM. Crosslinking with glutaraldehyde in presence of BSA as a spacer molecule was used for the method of immobilization. One layer of gelatin (10%) was applied over the immobilized enzyme layer to reduce the leaching out of enzyme from the membrane (cellulose acetate) matrix. The optimum pH of the immobilized system was determined to be 8.5 at 25 degrees C instead 7.0-7.2 for free enzyme system. Km and Vmax values were determined for the immobilized system. The developed sensor was applied to determine the amount of Hx present in fish and meat over a period of time. The stability of the enzyme immobilized membrane was also tested over a period of 30 days.     

Development of quality evaluation sensor for fish freshness control based on KI value

Recently, raw fish, sashimi, is becoming a popular dish in countries other than Japan. Therefore, in order to assure that the raw fish and shellfish are safe for human consumption, a quality evaluation sensor, which shows, at a glance, the quality of sashimi, was developed. The proposed sensor is based on the principle that the freshness of sashimi, which is judged from the KI value, can be determined from the degree of color change of thiazole blue (MTT: 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) due to the redox reaction of MTT accompanying the oxidation of hypoxanthine (Hx) by xanthine oxidase (XOD). The proposed sensor consists of 5 ml of 80% ethanol-1 M Tris-HCl buffer (pH 7.8) containing 2.0 mg of Hx, 2.0 mg of MTT and 0.38 unit of XOD. The proposed sensor and fish were kept together at 5, -10 and -20 degrees C, and the freshness of sashimi stored at each temperature was determined from the color change of the sensor. The concept "freshness of sashimi" can be expressed as remaining of validity (RDV), which is described in our previous study. A good relationship was obtained between the KI value and the RDV determined by the proposed sensor. From these results, the proposed sensor system can be used to non-destructively determine the fish freshness and RDV.     

Antibacterial activity among Pseudomonas strains of meat origin

Almost 750 Pseudomonas strains from meat, fish, milk or plant were screened for inhibitory potential towards 10 selected Pseudomonas fragi isolated from meat. Only strains of fish origin and a reference Ps. putida strain produced an inhibitory substance which was either a siderophore or a bacteriocin-like substance. The two systems were efficient in meat extract medium suggesting potential use for controlling meat quality.     

Bacterial protein meal produced on natural gas replacing soybean meal or fish meal in broiler chicken diets

The effects of replacing soybean meal or fish meal with 2, 4 or 6% bacterial protein meal (BPM) on growth performance, ileal digestibility of amino acids and sensory quality of meat, were examined using 630 broiler chickens. Weight gain from 7-32 days of age did not differ significantly among the treatments. Efficiency of feed conversion was increased when BPM replaced soybean meal, and abdominal fat deposition tended to decline. Feed conversion was not affected when BPM replaced fish meal. Amino acid digestibility was unaffected or improved when BPM replaced soybean meal, whereas replacement of fishmeal with BPM resulted in similar digestibility. Sensory quality of fresh thigh meat was similar among treatments, but for freeze-stored chest meat replacement of fish meal with BPM reduced off-odour and off-flavour and increased juiciness. It was concluded that 6% BPM can replace soybean meal or fish meal protein in broiler chicken diets.     

Iron status biomarkers in iron deficient women consuming oily fish versus red meat diet

Specific recommendations for anemic individuals consist in increasing red meat intake, but the population at large is advised to reduce consumption of red meat and increase that of fish, in order to prevent the risk of developing cardiovascular disease. This study aimed to determine the effects of consuming an oily fish compared to a red meat diet on iron status in women with low iron stores. The study was designed attending the Consolidated Standards of Reporting Trials (CONSORT) statement guidelines. It was a randomised crossover dietary intervention study of two 8-week periods. Twenty-five young women with low iron stores completed the study. Two diets containing a total of 8 portions of fish, meat and poultry per week were designed differing only in their oily fish or red meat content (5 portions per week). At the beginning and the end of each period blood samples were taken and hemoglobin, hematocrit, serum ferritin, serum iron, serum transferrin, serum transferrin receptor-2 and the Zn-protoporphyrin/free-protoporphyrin ratio were determined. Food intake and body weight were monitored. During the oily fish diet, PUFA intake was significantly higher (p=0.010) and iron intake lower (mean±SD, 11.5±3.4 mg/dayvs. 13.9±0.1 mg/day, p=0.008), both diets providing lower mean daily iron intake than recommended for menstruating women. Although there were no significant differences after 16 weeks, serum ferritin moderately decreased and soluble transferrin receptor increased with the oily fish, while changes with the red meat diet were the opposite. In conclusion, an oily fish diet compared to a red meat diet does not decrease iron status after 8 weeks in iron deficient women.     

Impact of season and sex on calcium and phosphorus content in the meat of roach (Rutilus rutilus L.) from the Brda River (Poland, Bydgoszcz)

The aim of this work was to compare the concentrations of calcium and phosphorus and Ca/P ratio in the meat of females and males of the roach (Rutilus rutilus L.) caught from the Brda River. The study involved 40 roach individuals caught in fall and spring (10 females and 10 males from each season). The muscle samples for analyses were taken from the large side muscle of the fish body above the lateral line. Ca concentrations were determined by atomic absorption spectrophotometry; P content was analyzed by the colorimetric method. Calcium concentration in the meat of analysed roach was higher in samples collected from fish caught in spring and equaled 1.82 g kg(-1) in females and 1.93 g kg(-1) in males. Values for individuals from autumn amounted to 0.83 and 1.10 g kg(-1), respectively. Statistically significant differences in calcium content were detected between individuals caught in different seasons, but samples taken from females and males caught within one season did not differ substantially. The mean value of P in the meat of analysed roach caught in spring was higher than in fish from autumn, and it was respectively 2.24 g kg(-1) in females and 2.30 g kg(-1) in males from spring, and 1.89 g kg(-1) in the tissue of females and 2.01 g kg(-1) in males in fish from autumn. The ratio of calcium to phosphorus in the meat of analysed wild roach ranged from 0.43:1 to 0.82:1. A negative and statistically significant correlation between Ca and P concentrations was found in the meat and the body length of analysed roach from the Brda River.     

Bacterial protein meal produced on natural gas replacing soybean meal or fish meal in broiler chicken diets

Abstract

The effects of replacing soybean meal or fish meal with 2, 4 or 6% bacterial protein meal (BPM) on growth performance, ileal digestibility of amino acids and sensory quality of meat, were examined using 630 broiler chickens. Weight gain from 7 – 32 days of age did not differ significantly among the treatments. Efficiency of feed conversion was increased when BPM replaced soybean meal, and abdominal fat deposition tended to decline. Feed conversion was not affected when BPM replaced fish meal. Amino acid digestibility was unaffected or improved when BPM replaced soybean meal, whereas replacement of fishmeal with BPM resulted in similar digestibility. Sensory quality of fresh thigh meat was similar among treatments, but for freeze-stored chest meat replacement of fish meal with BPM reduced off-odour and off-flavour and increased juiciness. It was concluded that 6% BPM can replace soybean meal or fish meal protein in broiler chicken diets.     

Proof of concept: predicting the onset of meat spoilage by an integrated oxygen sensor spot in MAP packages

During storage of modified atmosphere packaged (MAP) meat, the initial microbiota grows to high cell numbers, resulting in perceptible spoilage after exceeding a specific threshold level. This study analyses, whether elevated oxygen consumption in the headspace of MA-packages would enable a prediction method for meat spoilage. We monitored the growth of single spoiling species inoculated on high-oxygen MAP beef and poultry, performed sensorial analysis and determined oxygen concentrations of the headspace via a non-invasive sensor spot technology. We detected microbial headspace oxygen consumption occurring prior to perceptible meat spoilage for certain species inoculated on beef steaks. However, headspace oxygen consumption and cell counts at the onset of spoilage were highly species-dependent, which resulted in a strong (Brochothrix thermosphacta) and moderate (Leuconostoc gelidum subspecies) decrease of the headspace oxygen content. No linear decrease of the headspace oxygen could be observed for Carnobacterium divergens and Carnobacterium maltaromaticum inoculated on poultry meat. We demonstrate the applicability of an incorporated oxygen sensor spot technology in MAP meat packages for detection of spoilage in individual packages prior to its perceptible onset. This enables individual package evaluation and sorting within retail, and consequently reduces meat disposal as waste.     

Enzyme sensor for hypoxanthine and inosine determination in edible fish

Summary An enzyme sensor for hypoxanthine (Hx) and inosine (HxR), consisting of an enzyme membrane and an oxygen electrode, was constructed, Xanthine oxidase (XO) and nucleoside phosphorylase (NP) were both immobilized on a membrane prepared from cellulose triacetate, 1,8-diamino-4-aminomethyloctane and glutaraldehyde. The enzyme sensor responded to Hx and HxR in the presence of phosphate, while it responded only to Hx in the absence of phosphate. A linear correlation was observed between current decrease and the concentrations of Hx and HxR in the range 0.5–2.0 mM respectively. Correlation coefficients between the present enzyme sensor and a conventional enzymatic method were 0.98 and 0.94 for Hx and HxR respectively. The standard deviation was +-1.5 M and 0.75 M for Hx and HxR respectively in 100 experiments. A simple and rapid determination of Hx and HxR in fish meat was possible within 3 min with the enzyme sensor.     

Evaluation of a new model system for studying the formation of heterocyclic amines

Heterocyclic amines (HAs) are an important class of food mutagens and carcinogens, which can be found in cooked meat and fish. Increasing heating temperatures and times usually increase mutagenic activity in meat and meat extracts during cooking. We developed a model system, which allows to examine the effects of precursor composition and heating conditions (time and temperature) on the formation of HAs in meat. Homogenized and freeze dried meat samples (beef, pork chops, chicken breast and turkey breast) are heated with diethylene glycol in closed vials under stirring in a thermostated heating block. After an appropriate sample preparation (extraction and clean-up) ten different HAs were measured by HPLC analyses with gradient elution and mass selective detection. The time courses of HA-formation in the different kinds of meat at varying heating temperatures were determined up to heating times of 30 min. 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) was the most abundant HA in these experiments and reached the highest concentrations in the beef meat samples, as did the other HAs (MeIQ, AalphaC) at 220 degrees C in the heating block under stirred conditions. Additionally the influence of the antioxidant TBHQ (t-butylhydroquinone) on the formation of HAs in the model system was tested. However TBHQ effected only slight reductions of HA formation in all kinds of meat.     

A recombinant Fab fragment-based electrochemical immunosensor for the determination of testosterone in bovine urine

This work describes the development of an electrochemical, recombinant Fab fragment-based immunosensor for the detection of testosterone in bovine urine. The sensor comprised of a testosterone conjugate on the surface of screen-printed electrodes, and recognition followed by an anti-testosterone Fab fragment. The use of an IgG-horseradish peroxidase conjugate determined the degree of competition. Chronoamperometry at a potential of +100 mV, was chosen to reductively measure the product of the catalysis of 3,3',5,5'-tetramethylbenzidine catalysis. ELISA was primarily used to investigate the assay system, prior to transferring to SPEs. The final Fab-based sensor exhibited the linear range of 300-40,000 pg/ml with limit of detection of 90+/-13 pg/ml. Furthermore, the developed Fab sensor allowed for the determination of testosterone in bovine urine directly after dilution, omitting the necessity of extraction and hydrolysis. Comparison of administrated bovine urine samples between the developed Fab sensor and GC-MS data showed quantitative or semi-quantitative results and enabled identification of suspicious samples for further extensive analysis by established analytical techniques. With simple sample preparation, low limit of detection, and good repeatability, the proposed method can offer alternative advantages as a primary screening tool for meat quality control.     

Untrained consumer assessment of the eating quality of beef: 1. A single composite score can predict beef quality grades

Quantifying consumer responses to beef across a broad range of demographics, nationalities and cooking methods is vitally important for any system evaluating beef eating quality. On the basis of previous work, it was expected that consumer scores would be highly accurate in determining quality grades for beef, thereby providing evidence that such a technique could be used to form the basis of and eating quality grading system for beef. Following the Australian MSA (Meat Standards Australia) testing protocols, over 19 000 consumers from Northern Ireland, Poland, Ireland, France and Australia tasted cooked beef samples, then allocated them to a quality grade; unsatisfactory, good-every-day, better-than-every-day and premium. The consumers also scored beef samples for tenderness, juiciness, flavour-liking and overall-liking. The beef was sourced from all countries involved in the study and cooked by four different cooking methods and to three different degrees of doneness, with each experimental group in the study consisting of a single cooking doneness within a cooking method for each country. For each experimental group, and for the data set as a whole, a linear discriminant function was calculated, using the four sensory scores which were used to predict the quality grade. This process was repeated using two conglomerate scores which are derived from weighting and combining the consumer sensory scores for tenderness, juiciness, flavour-liking and overall-liking, the original meat quality 4 score (oMQ4) (0.4, 0.1, 0.2, 0.3) and current meat quality 4 score (cMQ4) (0.3, 0.1, 0.3, 0.3). From the results of these analyses, the optimal weightings of the sensory scores to generate an ‘ideal meat quality 4 score (MQ4)’ for each country were calculated, and the MQ4 values that reflected the boundaries between the four quality grades were determined. The oMQ4 weightings were far more accurate in categorising European meat samples than the cMQ4 weightings, highlighting that tenderness is more important than flavour to the consumer when determining quality. The accuracy of the discriminant analysis to predict the consumer scored quality grades was similar across all consumer groups, 68%, and similar to previously reported values. These results demonstrate that this technique, as used in the MSA system, could be used to predict consumer assessment of beef eating quality and therefore to underpin a commercial eating quality guarantee for all European consumers.     

家蝇作为饲料添加剂对清远良种鸡肉质和风味的影响

测定蝇蛆和蝇蛹作为饲料添加剂对清远良种鸡肉质和风味的影响,为家蝇Musca domestica L.作为添加饲料改善鸡的肉质和风味,以及代替鱼粉成为新的蛋白质来源提供数据。150只清远鸡雏鸡随机等分成5组,以鱼粉或商业饲料加入不同比例的家蝇幼虫或蝇蛹作为添加饲料加以饲养。结果显示,饲喂不同食料的清远鸡的增重、脾重和法氏囊重影响差异不显著,但饲喂蝇蛆和蝇蛹的鸡群的死亡率明显低于仅饲喂鱼粉或商业饲料的鸡群;饲喂蝇蛆或蝇蛹的鸡肉的系水力(用失水率表示)和风味评价明显提高,氨基酸含量差异显著。说明家蝇幼虫作为动物蛋白可提高鸡的抗疾病能力及改善鸡肉风味。     

Preliminary evaluation of COBRA, an automated DEFT instrument, for the rapid enumeration of micro-organisms in cultures, raw milk, meat and fish

A preliminary evaluation of an automated direct epifluorescent filter technique instrument, COBRA, showed that it enumerated rapidly bacteria in cultures, raw milk, meat and fish. The correlation coefficients of regression lines with corresponding pour plate counts were 0·99 (pure cultures), 0·81 (raw milk) and 0·91 (raw meat and fish), respectively. The system was simple to use, one operator could process > 100 samples/h and results were available in < 1 h.     

Bioerosion of corals and the influence of damselfish territoriality: A preliminary study

Summary Samples of the staghorn coral Acropora were taken from within territories defende by damselfish (Pisces: Pomacentridae) and from undefended areas. The fish utilized in this experiment were Hemiglyphidodon plagiometopon Bleeker and Pomacentrus bankanensis Bleeker. The extent of bioerosion was determined by randomly selecting pieces of coral substrate from treatment and control areas, cutting transverse sections, and determining total eroded area with the aid of enlarged photographs. Boreholes within the photos were traced with a digitizing sensor and area was integrated with the aid of a computer.Corals inside territoties were significantly more bioeroded (p<0.001) than corals outside areas. Most of the destruction was caused by boring sponges (Cliona sp.) and sipunculids (Cleosiphon). It is suggested that bioerosion is accelerated within territories as a result of reduction in grazing by fish.     

Wireless enzyme sensor system for real-time monitoring of blood glucose levels in fish

Periodic checks of fish health and the rapid detection of abnormalities are thus necessary at fish farms. Several studies indicate that blood glucose levels closely correlate to stress levels in fish and represent the state of respiratory or nutritional disturbance. We prepared a wireless enzyme sensor system to determine blood glucose levels in fish. It can be rapidly and conveniently monitored using the newly developed needle-type enzyme sensor, consisting of a Pt-Ir wire, Ag/AgCl paste, and glucose oxidase. To prevent the effects of interfering anionic species, such as uric acid and ascorbic acid, on the sensor response, the Pt-Ir electrode was coated with Nafion, and then glucose oxidase was immobilized on the coated electrode. The calibration curve of the glucose concentration was linear, from 0.18 to 144mg/dl, and the detection limit was 0.18mg/dl. The sensor was used to wirelessly monitor fish glucose levels. The sensor-calibrated glucose levels and actual blood glucose levels were in excellent agreement. The fluid of the inner sclera of the fish eyeball (EISF) was a suitable site for sensor implantation to obtain glucose sample. There was a close correlation between glucose concentrations in the EISF and those in the blood. Glucose concentrations in fish blood could be monitored in free-swimming fish in an aquarium for 3 days.     

Electronic Nose with an Air Sensor Matrix for Detecting Beef Freshness

China is one of the largest meat producing countries in the wodd. With the growing concern for food safety more attention has been paid to meat quality. The application of conventional test methods for meat quality is limited by many factors, and subjectiveness, such as longer time to prepare samples and to test. A sensor matrix was constructed with several separate air sensors, and tests were conducted to detect the freshness of the beef. The results show that the air sensors TGS2610, TGS2600, TGS2611, TGS2620 and TGS2602 made by Tianjin Figaro Electronic Co, Ltd could be used to determine the degree of freshness but TGS2442 is not suitable. This study provides a foundation for designing and making an economical and practical detector for beef freshness.     

Evaluation of the sustainability of contrasted pig farming systems: development of a market conformity tool for pork products based on technological quality traits

A market conformity tool, based on technological meat quality parameters, was developed within the Q-PorkChains project, to be included in a global sustainability evaluation of pig farming systems. The specific objective of the market conformity tool was to define a scoring system based on the suitability of meat to elaborate the main pork products, according to their market shares based on industry requirements, in different pig farming systems. The tool was based on carcass and meat quality parameters that are commonly used for the assessment of technological quality, which provide representative and repeatable data and are easily measurable. They were the following: cold carcass weight; lean meat percentage; minimum subcutaneous back fat depth at m. gluteus medius level, 45 postmortem and ultimate pH (measured at 24-h postmortem) in m. longissimus lumborum and semimembranosus; meat colour; drip losses and intramuscular fat content in a m. longissimus sample. Five categories of pork products produced at large scale in Europe were considered in the study: fresh meat, cooked products, dry products, specialties and other meat products. For each of the studied farming systems, the technological meat quality requirements, as well as the market shares for each product category within farming system, were obtained from the literature and personal communications from experts. The tool resulted in an overall conformity score that enabled to discriminate among systems according to the degree of matching of the achieved carcass and meat quality with the requirements of the targeted market. In order to improve feasibility, the tool was simplified by selecting ultimate pH at m. longissimus or semimembranosus, minimum fat thickness measured at the left half carcass over m. gluteus medius and intramuscular fat content in a m. longissimus sample as iceberg indicators. The overall suitability scores calculated by using both the complete and the reduced tools presented good correlation and the results obtained were similar. The tool could be considered as robust enough to discriminate among different systems, since it was tested in a wide range of them. It also can be used to detect improvement opportunities to enhance sustainability of pig farming systems. The final objective of the study was achieved, since the market suitability tool could be used in an integrated sustainability analysis of pig farming systems.     

Determination of adenosine 5′-monophosphate in fish and shellfish using an enzyme sensor

An enzyme sensor for the determination of adenosine-5′-monophosphate (AMP) concentration in the muscle of fish and shellfish has been developed. The AMP sensor consisted of two immobilized enzyme membranes and an oxygen probe. AMP was oxidized to uric acid by AMP-deaminase, 5′-nucleotidase, nucleoside phosphorylase and xanthine oxidase, and oxygen consumed was monitored amperometrically by an oxygen electrode. The optimum conditions for the enzyme electrode were pH 7.8 and 30°C. Output current was reproducible within 4% of the relative error when a solution containing 10 mm AMP was used. One assay could be completed within 4 min and the sensor was stable for 100 assays over 30 days at 5°C. The sensor was used to determine AMP concentration in bream, Pagrosomus unicolor Quoy and Gaimard; sea bass, Lateolobrax japonicus; flounder, Lepidopsetta bilineata; abalone, Haliotis discus hannai; and arkshell, Anadara broughttoni (Shrenk). AMP in a sample solution was also determined by a conventional method, giving satisfactory comparative results.