Determination of the cooking degree for bulgur production using amylose/iodine,centre cutting and light scattering methods

In the present study, the amylose/iodine and light scattering methods were used to determine the cooking degree based on starch gelatinization for the production of bulgur as alternative to traditionally used centre cutting method. Cooking operation was carried out at boiling temperature (97 °C) using Triticum durum wheat for 130 min. The cooking degree was controlled using the three methods and the deformation degree of the intact wheat kernels. It was found that the gelatinization values obtained from the amylose/iodine method were higher than the others up to reaching 100% cooking degree. The results for the cutting method were same with the light scattering method. The optimum cooking time was determined as 40 min. Excess cooking caused significant deformation on the intact wheat kernel during the cooking operation. Both alternative methods i.e. amylose/iodine and light scattering can be used to the control of cooking system. In addition, the light scattering method can be preferred in the automation having bulgur production systems.     

Thermal inactivation of Listeria monocytogenes from alheiras,traditional Portuguese sausage during cooking

D values were calculated at 55, 60 and 65 °C for five Listeria monocytogenes isolates using alheira (traditional Portuguese sausage) food matrix as heating menstrum. z values were also calculated and combined with internal alheiras temperature profiles during cooking in multiple ways, allowed estimations of percentages of L. monocytogenes survival.Survival percentages estimations showed that except for roasting, the remaining evaluated cooking methods might not be sufficient to inactivate this foodborne pathogen in alheiras at the minimum temperature profiles. However, it is important to note that all evaluated cooking methods were able to inactivate L. monocytogenes in alheiras at their maximum internal temperature profiles.     

Influence of noodle processing (industrial protocol) on deoxynivalenol

The effects of processing for two types of Asian noodles production (yellow alkaline and instant) on DON levels were investigated. Deoxynivalenol (DON) level at each step of processing was determined using high performance liquid chromatography (HPLC) with a PDA (photodiode array) detector at 218 nm. An acetonitrile: water (17:83 v/v) mixture was used as mobile phase and a MycosepTM #225 column as clean-up method. Significant reductions of the initial DON levels were found, 43.2% and 66.6% in yellow alkaline and instant noodles, respectively. The presence of alkaline salt as an ingredient appeared to be the primary factor influencing the extent of reduction in the two types of noodles. The data indicated that significant reduction of DON have occurred during cooking and frying of both yellow alkaline and instant noodles, respectively. The mechanism of reduction due to cooking is probably a leaching of DON out of the noodle into the cooking medium.     

Influence of various cooking processes on the concentrations of PCDD/PCDFs,PCBs and PCDEs in foods

The effects of several cooking processes commonly used by the population of Catalonia (Spain) on the total concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/PCDFs), polychlorinated biphenyls (PCBs), and polychlorinated diphenyl ethers (PCDEs) were assessed in various foodstuffs. The levels in raw and cooked samples were determined by HRGC/HRMS. Cooking processes (fried, grilled, roasted, and boiled) had different effects on the levels of PCDD/PCDFs in fish, while in meats cooking reduced PCDD/PCDF concentrations in veal and pork. In the remaining foodstuffs, the differences were only relevant for fried potatoes. Cooking showed also different effects on the levels of PCBs in fish, while in meats cooking enhanced PCB concentrations. Cooking processes enhanced ΣPCDE levels in most fish and meat samples. These results show that, in general terms, cooking processes are only of limited value as a means of reducing concentrations of PCDD/PCDFs, PCBs and PCDEs in food.     

Effects of cooking and freezing practices on the distribution of cadmium in different tissues of the brown crab (Cancer pagurus)

Increased cadmium concentrations in claw meat were demonstrated after cooking and freezing practices of whole brown crabs. This was investigated in crabs from two different locations along the Norwegian coast, one with normal and one with high cadmium concentration. For both locations, in whole crabs, samples of fresh raw claw meat showed lowest values followed by raw-boiled and frozen-thawed-boiled. Cadmium levels in separately cooked claws were comparable to the low values in claws from raw whole crab. Claws taken from frozen crabs before thawing had low values compared to claws taken off the carapace after thawing. This clearly indicates a transfer from hepatopancreas to claw meat, which potentially induces biases when measuring and monitoring Cd levels in crabs. Further, different cooking and storing practices might have profound effects on cadmium intake from eating crabs since concentrations above regulatory limits were found following common household and commercial practices.     

Duplex real-time PCR assay for the simultaneous determination of the roe deer (Capreolus capreolus) and deer (sum of fallow deer,red deer and sika deer) content in game meat products

Due to the high price of game meat, food producers may be tempted to adulterate their products with cheaper meat. This paper presents a duplex real-time PCR assay which allows the simultaneous determination of the content of roe deer (Capreolus capreolus) and deer* (the sum of fallow deer (Dama dama), red deer (Cervus elaphus) and sika deer (Cervus nippon)) in food products to detect food adulteration. Relative quantification is carried out by using a reference (“all meat”) PCR assay based on the myostatin gene. The quantification approach was validated by analyzing binary meat mixtures with pork, “all game” meat mixtures containing each of the four game species in pork and a model game sausage. Compared to singleplex assays the duplex assay is time and cost saving. Thus, it is highly applicable to routine analysis in order to verify the authenticity of game meat products.     

Thermal profiles of domestically baked leg-of-lamb roasts and implications for microbiological safety

The measurement of the effectiveness of cooking in the real world has received little attention in the scientific literature. In this study the core temperatures of 16 leg-of-lamb roasts were measured during baking in 14 electric or gas-fired domestic ovens in order to assess the adequacy of cooking relative to recommendations of food authorities to minimise foodborne illness due to microorganisms. The mass of the roasts was 1.80 ± 0.33 kg (mean ± s.d.). The intended extent of cooking indicated by volunteer cooks who were selected from a range of cultural backgrounds ranged from rare to well done, with most preferring greater than medium rare, but the actual degree of doneness achieved was slightly more than intended. One roast was unevenly cooked, with parts well done and other parts medium rare. Ovens reached peak temperature over a variable period ranging from 5 to 25 min. However, there was substantial variation between the oven set temperature and the actual maximum oven temperature recorded. Only five of 14 ovens provided an actual maximum temperature within 10 °C of the set temperature and some were as much as 50 °C below the set temperature. Peak temperatures at the core of the majority of roasts were attained after about 1.5–2.5 h. The maximum core temperatures recorded among roasts ranged from 59.6 °C to 98.3 °C; three roasts had maximum core temperatures less than 70 °C. The least well-cooked roast reached 59.6 °C at one probe site and 65.9 °C at the other. The variables observed in this study support recommendations for use of meat thermometers during baking of red meat and should stimulate further evaluation of domestic cooking practices.     

Comparison of real-time PCR and ELISA-based methods for the detection of beef and pork in processed meat products

Two commonly used methodologies for species detection within processed meat products are real-time polymerase chain reaction (PCR), a DNA-based method, and enzyme-linked immunosorbent assay (ELISA), a protein-based method. In this study, a real-time PCR assay was compared to a commercial ELISA kit based on sensitivity, specificity, agreement among duplicate samples, cost, time, and ease of use. Fifteen reference samples containing known percentages (0.1–99.9%, w/w) of pork and beef were analyzed in duplicate using both methods. Thirty commercial products, including sausages, pet treats, and canned meats, were also tested in duplicate with each method. Reference sample analysis showed real-time PCR was able to detect pork in duplicate samples at 0.10% and beef at 0.50% in the binary mixtures. ELISA detected pork in duplicate samples at 10.0% and beef at 1.00% in the binary mixtures. When the results of reference and commercial samples were combined, real-time PCR demonstrated the greatest agreement among duplicate samples, at 96.7%, compared to 95.6% agreement for ELISA. The real-time PCR assay used in this study was found to be less expensive, while ELISA was less time-consuming and easier to perform. Both methods were successful at identifying species in ground meats, sausage, and deli meat samples; however, pet treats and canned meats proved more challenging. Overall, it was determined that the real-time PCR assay was optimal for species identification in processed meat products when a low detection limit is required; however, the ELISA kit may be advantageous in other situations due to its ease of use.     

A risk assessment of salmonellosis linked to chicken meals prepared in households of China

A quantitative microbiological risk assessment model was used to quantify the risk of salmonellosis caused by bacterial growth and cross-contamination of chicken meals prepared in households of China. Chinese data on initial loads of Salmonella in chicken carcasses sold at retail, storage time and handling of raw chicken meat in household kitchens and confirmatory transfer rates of Salmonella among different kitchen objects were collected. Only one third of Chinese families in our sample separated the cutting board between raw and ready-to-eat foods. The cross-contamination of ready-to-eat foods from chicken meals via the cutting board, the knife and cooks’ hands increased the frequency of pathogen ingestion and the risk of salmonellosis. A significant decrease in the risk of salmonellosis could be achieved by reducing the cross-contamination when handling raw chicken meat and ready-to-eat foods. Decreasing the prevalence of Salmonella contamination to 8.8% or removing chicken carcasses with contamination densities higher than 100 MPN/100 g at retail was less effective. Using transfer rates of Salmonella from raw chicken meat to the wooden cutting board instead of that from references, a statistically higher risk of salmonellosis per serve due to the cross-contamination in households was observed. The present study validated values of hygiene practices in China to reduce the risk of salmonellosis from contaminated raw chicken meat at retail. Deliberate surveys for cooking behaviors and transfer rates of Salmonella from and to different objects including wooden cutting boards were needed.     

Thermal flame spectroscopy of various diesel fuels and their blends with waste cooking oil through using coaxial burner

Flame spectroscopy for conventional fuels and their blends with waste cooking oil (WCO) wasn’t carried out yet. In this research, WCO was blended with both light diesel oil (LDO) and heavy diesel oil (HDO) by 20% by mass, B1 and B2 respectively where no chemicals were added. Combustion processes were done by swirled vane burner inside and outside the water boiler at different heat loads. Axial plane flame temperatures were measured. The results showed that the highest peak thermal energy was achieved by HDO at all heat loads. Blend B2 produced lower heat energy than HDO by nearly average 7.5%. B2 produced lower heat energy transferred to water boiler than HDO by nearly 12.2%, 2.1%, 8.2 and 7.6% while B1 supplied 17%, 13.6%, 29.4% and 6.1% lower compared to LDO. LDO atoms are excited for long period along the flame length while WCO took short one. Both flame temperature and emission radicals of B1 were lower than that of LDO at the same condition and position. Fuel droplets size controlled the absorption of radiation energy for atom excitation.     

A control strategy to assure safety conditions in the thermal treatment of meat products using a numerical algorithms

A finite element computational code was programmed in Matlab language to establish time–temperature specifications, in order to assure thermal inactivation of Escherichia coli O157:H7 in black sausages, produced in small scale plants. Even though the heating system in these plants may have a temperature control operating on the gas burners, the immersion water temperature can decrease significantly if the load ratio (sausage/water mass) increases; the thermal inertia of the system makes it difficult to re-establish this temperature instantaneously. The effect of the ratio between the amount of thermally treated sausages and the heat capacity of the system, on the temperature drop in the water bath, was mathematically simulated and experimentally validated. Computer simulations were performed by coupling the numerical solution of the microscopic heat conduction equation in the product with the macroscopic heat balance, which considers the heat flux of the gas burners. The model satisfactorily predicted experimental time–temperature results (mean error less than 5%) and constitutes a useful tool for meat processors and plant operators since it allows to determine adequate time–temperature conditions as a function of load ratio and initial water temperature, combining the microbial lethality kinetics with the main program.     

Effect of quenching on cookability of some food legumes

The cooking time of three varieties of cowpea (Vigna unguiculata) were determined by sudden and rapid decrease in the temperature (quenching) of boiling cowpea seeds, by the addition of water at a lower temperature. The varieties of cowpea used were, ‘Sokoto white’, ‘Potesco white’ and ‘Ife brown’. The results showed that quenching with water at a temperature of about 62 °C produced the maximum reduction in the cooking time for all the varieties. ‘Sokoto white’ which exhibited the longest cooking time among the cowpea varieties considered showed about 29% reduction in total cooking time while ‘Ife brown’ with the shortest cooking time showed a percentage reduction of about 13%. When the study was extended to another legume, pigeon pea (Cajanus cajan) which has a very long cooking time relative to most cowpea varieties, a 40% reduction in cooking time was observed. However, cooking the varieties with trona, ‘Sokoto white’ and ‘Ife brown’ showed 26% and 30% reduction in cooking time respectively, while the pigeon pea showed 25% reduction.     

On-line system identification and control design of an extrusion cooking process: Part I. System identification

A systems analysis of an extrusion cooking process for puffed corn snack products revealed that the specific mechanical energy (SME) and screw speed (SS) was a desirable pairing of measured and manipulated variables, respectively for regulating extrudate density. To facilitate the design of an SME model-based control system, a discrete-time transfer function that depicts the dynamic response of motor load (ML) to changes in SS is required. The research literature describes several off-line techniques for developing such transfer function models but no methods for on-line system identification were found. This paper represents the first of two articles that describe our investigations into the use of on-line system identification for automatic tuning and adaptive control of a high-shear twin-screw extrusion process. This paper reports results for using various system identification schemes in combination with relay-feedback as a way to derive, in real-time, a transfer function model that accurately depicts the dynamical behavior of an extrusion cooking process. A Wenger TX-52 co-rotating twin screw extruder was subjected to relay feedback during the processing of cornmeal for a breakfast cereal formula under different moisture and screw speed conditions. The data obtained from these experiments were used to derive first-, second- and third-order discrete-time transfer functions. An analysis of the resulting transfer functions revealed that a first-order lead-lag transfer function structure adequately described the dominant dynamic behavior of the process in all cases. Next, batch and recursive implementations of least-squares, extended least-squares, output error, maximum likelihood, Box–Jenkins and predictive error algorithms were used to derive parameters for the first-order transfer function. Overall, the batch output error method provided good transfer function estimates over the range of product and process conditions studied.     

蒸汽驱井下温度压力连续监测采油技术研究与试验——以曙光油田杜229区块为例

针对辽河曙光油田杜229区块蒸汽驱开发先期转驱区域观察井少,指导调驱依据的温度压力监测资料不足等问题,开展井下温度压力连续监测采油技术研究。采用集热电偶测试温度和毛细管测试压力于一体的温度压力监测技术,对井下油层实现多点温度压力连续动态实时监测。现场优选试验井杜32–53–33井,进行施工方案及相关参数设计,对井下油层分两层进行两点监测温度和压力,以此监测资料作为依据,及时调整井组注采参数,取得了较好的应用效果,达到了指导蒸汽驱开发动态调控的目的。     

Development of an efficient real-time PCR assay to quantify enterotoxin-producing staphylococci in meat products

A SYBR Green-based real-time PCR (qPCR) procedure for the rapid and specific detection of enterotoxin-producing Staphylococcus spp. in meat products has been developed. For this, a specific primer pair based on conserved regions of enterotoxin genes was designed for detecting most of the described staphylococcal enterotoxins. No cross-reactivity with other microorganisms or non-enterotoxin-producing Staphylococcus spp. was detected. The detection limits of the assay were about 2–40 cfu/g for artificially contaminated meat products after 8 h enrichment period at 30 °C. Total time for assay completion was approximately 12 h. Thus, the qPCR method offers a useful, rapid and efficient tool for screening enterotoxin-producing Staphylococci in meat products. This tool could be also used for monitoring these foodborne pathogens in food safety preventive programs.     

Investigation of performance and emission characteristics of waste cooking oil as biodiesel in a diesel engine

Biodiesel is one of the most popular prospective alternative fuels and can be obtained from a variety of sources. Waste frying oil is one such source along with the various raw vegetable oils. However, some specific technical treatments are required to improve certain fuel properties such as viscosity and calorific value of the biodiesel being obtained from waste cooking oil methyl ester (WCOME). Various treatments are applied depending on the source and therefore the composition of the cooking oil. This research investigated the performance of WCOME as an alternative biofuel in a four-stroke direct injection diesel engine. An 8-mode test was undertaken with diesel fuel and five WCOME blends. The best compromise blend in terms of performance and emissions was identified. Results showed that energy utilization factors of the blends were similar within the range of the operational parameters (speed, load and WCOME content). Increasing biodiesel content produced slightly more smoke and NOx for a great majority of test points, while the CO and THC emissions were lower.     

The effects of washing and cooking on chlorpyrifos and its toxic metabolites in vegetables

The effect of household processing on removal of chlorpyrifos residue from vegetables, and the formation of metabolite during processing were studied. Many factors: washing solutions, pH value, cooking mode, processing time were investigated. Analysis of chlorpyrifos and its metabolites was carried out by gas chromatography coupled to triple quadrupole mass spectrometry. Hydrolysis of chlorpyrifos affected the removal of residue from leafy vegetable during washing. Cooking on removal of chlorpyrifos residue was more effective than washing. Chlorpyrifos degraded into 3,5,6-trichloro-2-pyridinol during cooking, while chlorpyrifos did not degrade into chlorpyrifos oxon in all experiments.     

Growth behavior prediction of fresh catfish fillet with Pseudomonas aeruginosa under stresses of allyl isothiocyanate,temperature and modified atmosphere

Pseudomonas aeruginosa, an opportunistic pathogen which can be found on fresh catfish fillet, grows rapidly when temperature rises above 4 °C. The combination of allyl isothiocyanate (AIT) and modified atmosphere (MA) was applied and proved effective to retard the growth of P. aeruginosa. The objective of this research was to develop simple mathematical models to predict the growth behavior of P. aeruginosa in catfish fillet and its potential storage time (in abuse temperature condition) as a function of AIT and temperature with/without MA treatment. The antimicrobial effect of gaseous AIT (0, 18 and 36 μL/L) on the growth of P. aeruginosa cocktail was evaluated at 8, 15 and 20 °C. Furthermore, the effects of MA (49% CO₂, 50.5% N₂ and 0.5% O₂) alone and AIT/MA combination were also investigated. These data obtained through an experimental design were used for model development. The regression models for lag phase, growth rate and “shelf life” (based on P. aeruginosa which closely related to Pseudomonas fluorescens and Pseudomonas pudita and all belong to the same RNA group used to classify the Pseudomonas at the subgenus level) were validated experimentally. Surface plot of models was also drawn to lucidly represent the interaction of AIT and temperature. The developed models may provide useful information for food industry in designing or selecting the proper packaging system with incorporation of AIT to attain the food safety with acceptable “shelf life” of fresh fish products under specified and potential abuse (with temperature deviation) distribution and storage conditions.     

Modelling of the microbiological quality of meat

An alternative to challenge tests for the assessment of the shelf-life of food products is predictive microbiology, the development of mathematical models that describe the influence of predominant controlling factors (such as temperature, water activity and pH) on the lag phase and the growth rats of microorganisms. In this paper, modifications of the square-root model are tested to predict the relationship between growth rate and temperature, and between lag phase and temperature, of spoilage organisms growing in a vacuum-packed, cooked meat product and on aerobically packed fresh meat. The emphasis of the study was on examining the growth behaviour of the spoilage flora in the meat product, and on fresh meat rather than in liquid media. Results show that the square-root model in its modified forms can indeed be used to describe the effect of storage temperature on the growth rate and the lag phase of the organisms involved. Although predictions of the models have to be validated in practical situations, predictive microbiology has been shown to be a promising technique for the estimation of a product's shelf-life and the impact of any modification of a product's formulation on both its safety and its shelf-life.