Integrating statistical process control to monitor and improve carcasses quality in a poultry slaughterhouse implementing a HACCP system

In meat slaughterhouses, the enumeration of certain microorganisms as microbiological quality indicators is very important for verifying effectiveness of the Good Hygiene Practices (GHP) and Hazard Analysis Critical Control Points (HACCP) systems. Microbiological testing of final products as part of the HACCP verifying process may provide information that a process is in control. The aim of this work was to exploit the data from a poultry slaughterhouse implementing HACCP and demonstrate an alternative approach to the conventional statistical analysis using the principles of the Six Sigma quality. The data collected on Total Viable, Total Coliforms and Staphylococcus aureus counts were used to construct control charts (X bar–R control chart) and perform process capability analysis. Based on X bar–R control charts, the process was in a statistical control state but this before its automation was not capable since process capability and process performance indices were below 1.00, indicating the production of poultry carcasses with poor microbiological quality. After process automation, the indices were much higher than 2.00, indicating that the process was capable of producing poultry carcasses within the specification limits.     

Application of the magnetic induction technique for the non-destructive assessment of salt gain after the salting process of Parma ham

The fast and non-destructive inspection of salt uptake after the salting phase of dry-cured ham process still remains a goal to allow the optimization of the salting process.This work aims to show the capability of a single frequency, magnetic induction (MI) system, to predict salt (NaCl) content of whole hams after the salting stage. MI system is based on the measurement of the perturbation caused by an alternating excitation magnetic field on a conductive sample; the perturbation is typically detected by measuring the current induced in a suitable receiver coil. One hundred and fifty-nine hams were scanned by the MI scanner before and after the salting phase. Hams were dissected, separated into muscle and fat parts, and analysed for salt content (potentiometric method). Predictive models (multi-linear regression analysis) of the salt gain in hams were developed, based on output signals generated by the MI system. The model including independent variables given by scanning ham when raw and after the salting, achieved the best accuracy (R² = 0.89; RMSEC = 0.19%). It was concluded that variations in electrical conductivity originated by different salt content and revealed by magnetic induction have potential application to predict the salt content inside entire bone-in hams after salting process.     

A neural network for predicting moisture content of grain drying process using genetic algorithm

This paper is concerned with optimizing the neural network topology for predicting the moisture content of grain drying process using genetic algorithm. A structural modular neural network, by combining the BP neurons and the RBF neurons at the hidden layer, was proposed to predict the moisture content of grain drying process. Inlet air temperature, grain temperature and initial moisture content were considered as the input variables to the topology of neural network. The genetic algorithm is used to select the appropriate network architecture in determining the optimal number of nodes in the hidden layer of the neural network. The number of neurons in the hidden layer was optimized for 6 BP neurons and 10 RBF neurons using genetic algorithm. Simulation test on the moisture content prediction of grain drying process showed that the SMNN optimized using genetic algorithm performed well and the accuracy of the predicted values is excellent.     

CRC技术在大港石化公司催化裂化装置的工业应用

介绍了CRC(冷再生催化剂循环)专利技术在大港石化公司1400kt/a催化裂化装置的应用情况。结果表明,催化裂化装置实施CRC技术改造后,装置运行正常,操作平稳,调节灵活。在原料性质相同的情况下,与改造前对比,汽柴油液化气收率增加1.99%,轻油收率增加0.31%,装置总能耗降低6.73kgEO/t原料。汽油烯烃含量降低8.72%,芳烃含量增加5.96%,汽油硫含量降低27mg/L。由此可见,催化裂化装置经过CRC技术改造后,产品分布得到优化,产品质量得到明显改善,节能效果显著,产生可观的经济效益。     

HACCP with multivariate process monitoring and fault diagnosis techniques: application to a food pasteurization process

Multivariate statistical process monitoring (SPM), and fault detection and diagnosis (FDD) methods are developed to monitor the critical control points (CCPs) in a continuous food pasteurization process. Multivariate SPM techniques effectively use information from all process variables to detect abnormal process behavior. Fault diagnosis techniques isolate the source cause of the deviation in process variable(s). The methods developed are illustrated by implementing them to monitor the critical control points and diagnose causes of abnormal operation of a high temperature short time (HTST) pasteurization pilot plant. The detection power of multivariate SPM and FDD techniques over univariate SPM techniques is shown and their integrated use to ensure the product safety and quality in food processes is demonstrated.     

Statistical process control with several variance components in the dairy industry

A typical problem of the application of statistical process control is that of the several variance components of the variable. We can encounter it, for example, in the control of the dry matter content in buttercream. This production is a batch process since the buttercream is mixed in a cutter. The variation of the dry matter content comes from the deviation of the compound, of the sample units and of the measurements of the same sample unit. The variance of the process is estimated from these components and three control charts are presented for monitoring the average, the sample-to-sample variability and the within-sample variability.     

低压富气乙烷回收工艺改进

目的国内油田伴生气乙烷回收均采用液相过冷工艺(LSP),解决该工艺在乙烷回收运行工况中存在的能耗较高、回收率较低的问题。 方法基于LSP工艺流程和气相过冷、气液相混合过冷的原理,提出气液两相过冷改进工艺(GLSP)、原料气分流过冷工艺(FGSP),并进行工艺流程对比分析,重点研究改进工艺的特性和对原料气中CO₂的适应性。 结果①GLSP工艺适用于外输气压力低的油田伴生气乙烷回收,具有乙烷回收率高、CO₂适应性强(CO₂摩尔分数为0.5%~2.5%)等特点;②GLSP工艺流程最优增压压力范围为4.0~4.5 MPa,乙烷回收率不宜超过95%;③在原料气中CO₂含量相同的条件下,随着气质变富,脱甲烷塔控制CO₂冻堵的能力不断增强;④在同一气质条件下,装置总能耗随着原料气中CO₂含量的增加而增大。 结论提出的改进工艺提高了乙烷回收率,确定了最优增压范围,并提高了对原料气中CO₂的适应性,为实际低压富气乙烷回收装置设计提供参考。      

成型和焊接对高强管线钢管焊缝及热影响区冲击韧性的影响

为了提高高强管线钢管焊缝及热影响区冲击韧性性能,综述了高强管线钢管成型和焊接对焊缝及热影响区（HAZ）冲击韧性的影响。结果表明,提高高强管线钢管焊缝及HAZ冲击韧性的有效方法是,根据原料特性、生产要求、产品规格及性能指标等制定合理成型工艺和焊接工艺,精确控制成型合缝质量和焊接热输入,合理匹配线能量和预热温度,正确选用焊丝和焊剂。     

On-line system identification and control design of an extrusion cooking process: Part II. Model predictive and inferential control design

A non-linear model-based predictive control law to regulate specific mechanical energy (SME) using screw speed is developed. Operating variable setpoints are determined using an inferential model that correlates SME with product density and melt moisture content. Additionally, a ratio control strategy is used to regulate melt moisture content and an output noise filter is added to attenuate sensor noise. When combined with an on-line system identification procedure, the resulting system provides good servo and regulatory control response that is robust to modeling errors and disturbances. This paper represents the second of two papers that describe our investigation into the use of on-line system identification for automatic tuning and adaptive control of high-shear twin-screw extrusion processes. The resulting control design addresses the need for a comprehensive system that can be used to regulate extrudate density in extrusion cooking and puffing processes.     

响应面法优化聚甲醛二甲醚的合成工艺

选择一种催化效果较好的功能化离子液体作为催化剂,研究了甲醇(MeOH)与三聚甲醛(TOX)合成聚甲醛二甲醚的工艺。在单因素实验基础上,采用响应面分析法的中心组合设计原理,利用软件Design-Expert 8.05b考察了反应温度、反应釜压、原料摩尔比(n_MeOH/n_TOX)、催化剂用量,以及因素间的交互作用对聚甲醛二甲醚产率的影响,建立了聚甲醛二甲醚产率的二次线性回归方程,获得了最优工艺条件。在反应温度100℃、N₂压力2.061 MPa,n_MeOH/n_TOX=1.687,催化剂质量分数1.751%的最优工艺条件下,聚甲醛二甲醚产率为56.49%,与响应面模型预测值56.82%非常吻合,说明采用响应面法得到的优化方案有效、可靠。     

Influence of technological parameters and hydrogen-containing gas consumption on the efficiency of middle distillates hydrodesulphurization process

This paper presents the results of a study of the influence of process parameters (contact time, temperature and pressure) and hydrogen-containing gas consumption on the efficiency of catalytic hydrotreating of middle distillate fractions, performed using a mathematical model of the process. It was found that with the increase in the contact time of the raw material with the catalyst, the concentration of sulfides decreases more rapidly than the concentrations of benzothiophenes and dibenzothiophenes. The degree of conversion of sulfides, benzothiophenes and dibenzothiophenes increases with the process temperature in the range from 350 to 425?°C by 39.9; 37.5 and 19.4%, respectively. The greatest degree of desulfurization is achieved by simultaneous increase in pressure and temperature. Thus, at a temperature of 430?°C, an increase in pressure from 2.0 to 4.0?MPa leads to a decrease in the residual sulfur content from 230 to 13.5?ppm. With an increase in the consumption of hydrogen-containing gas from 42,000 to 50,000 m³/h, the efficiency of the hydrotreating process of the middle distillate fractions increases (the residual content of total sulfur in the hydrotreating product decreases from 55.9 to 24.8?ppm).     

炼油工业:市场的变化与技术对策

经济新常态下,中国主要成品油消费仍呈增长趋势,汽油和煤油刚性需求增长较快,而柴油需求增速大幅减少,市场需求的柴/汽比明显下降。环保压力增大,国Ⅴ柴油标准和国Ⅴ汽油标准相继推出,油品质量升级步伐必须加快。乙烷制乙烯技术的大规模市场化使石脑油蒸汽裂解生产低碳烯烃受到挑战,开发具有竞争力的丙烯生产技术受到关注。面对市场的变化,为更加高效、清洁地利用宝贵的石油资源,为满足市场需求多产汽油和喷气燃料,为提供更具竞争力的丙烯等基本化工原料,炼油研发部门近年来主动积极地开发一系列新的关键技术,包括更高效的固定床渣油加氢技术(RHT)、多产轻质油的催化裂化蜡油选择性加氢与选择性FCC集成技术(IHCC)、第三代催化裂化汽油选择性加氢脱硫技术(RSDS-Ⅲ)、柴油超深度加氢脱硫技术(RTS)、催化柴油加氢裂化生产高辛烷值汽油技术(RLG)、低压喷气燃料加氢RHSS技术、多产化工原料的催化丙烯技术(SHMP)。这些技术或技术组合将对支撑未来炼油工业的发展和应对市场变化发挥重要作用。     

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.     

Process control based on principal component analysis for maize drying

Producing the grain with equilibrium moisture content is an important process control objective. However, achieving this objective can be very difficult in grain drying process because of its multi-variables, nonlinearity and long delay. In this paper, a control approach based on principal component analysis (PCA) is presented to achieve this objective. A PCA model which incorporates time lagged variables is used, and the control objective is expressed in the score space of this PCA model. A controller is designed in the model predictive control framework, and it is used to control the equivalent score space representation of the process. The score predictive model for the model predictive control algorithm is built using neural network partial least squares (NNPLS). The process control system with NNPLS was tested on a commercial mixed-flow dryer and showed excellent accuracy and stability.     

Microbial composition of turbid rice wine (Makgeolli) at different stages of production in a real processing line

The aim of this study was to examine for changes in microbial populations during the production of turbid rice wine (also known as Makgeolli) at different production plants and to identify critical points for the control of microbial quality. Samples from raw ingredients (water, rice and wheat flour), materials from different production stages (steamed ingredients, the base of fermentation, primary and secondary fermentation stages at different time points), and the final rice wine products (non–sterilized and sterilized) were analyzed. The microbiological content of samples was assessed by quantitative (aerobic plate counts, lactic acid bacteria, fungi, acetic acid bacteria, coliforms and Bacillus cereus) and qualitative (Escherichia coli and eight foodborne pathogens) analyses. Aerobic plate counts for rice and wheat flour were relatively low (3.1 and 1.9 log CFU/g, respectively), as were those for lactic acid bacteria (1.6 and 2.1 log CFU/g), and fungi counts (2.2 and 0.7 log CFU/g). All counts increased to 7.8–7.9 log CFU/ml in the base of fermentation after the addition of Nuruk and Koji, and these counts were maintained at 8–9 log CFU/ml during fermentation. Acetic acid bacteria were not detected in the ingredients, but were isolated from the base of fermentation (1.2–2.8 log CFU/ml). Heat sterilization reduced aerobic pate counts significantly from 8.4 to 2.1 log CFF/ml, and lactic acid bacteria, fungi and acetic acid bacteria were reduced to non-detectable or negligible levels. Isolated microorganisms were considered as autochthonous to the environment or were artificially introduced with the starter culture. B. cereus was widely distributed throughout the manufacturing process, and may have been introduced from the raw material (present in 100% rice and 41.7% wheat flour samples). B. cereus counts were not significantly affected by sterilization, suggesting that it may exist at low levels as spores in the final products. No coliforms and other pathogens were detected in any samples. The raw materials, the base of fermentation, and sterilization stage were identified as important points for the control of microbial quality during the fermentation process.     

Rheological,physicochemical and authenticity assessment of Minas Frescal cheese

This study was carried out to assess physicochemical (color, moisture, protein and fat content) and rheological properties (fracture stress, fracture strain, degree of solidity and stress decay), as well as to assess the authenticity (using SDS-PAGE) of Minas Frescal cheese in 21 commercial samples acquired in Southern Brazil. Large differences among the samples, which tended to present a yellowish white color were observed. Moisture and protein influenced on the rheological properties and cheeses showed a tendency to being viscous and firm. SDS-PAGE revealed a wide unexpected variability in their proteins profiles and a densitometric casein/β-lactoglobulin ratio allowed to distinguish authentic cheese from adulterated ones. The profiles suggest the irregular presence of whey in the composition of these products, contrary to the enzymatic process legally required. These results emphasize the need for a more effective control, mainly in the selection of raw material, aiming to offer consumers authentic products.     

利用吸附余压预冷的煤层气氮膨胀液化流程

煤层气液化是对煤层气进行开发利用的一种有效方式。而由于受抽采技术的限制,煤层气中常含有较多的氮气。因此在预净化处理后,还须在液化前进行变压吸附或液化后进行低温精馏实现氮和甲烷的分离,从而提高甲烷浓度。为此,构建了一种新型的吸附-液化一体化的氮膨胀液化流程,将吸附后排出的带余压氮气直接膨胀对浓缩后的煤层气进行预冷。通过HYSYS模拟计算考察了不同含氮量和不同吸附余压下系统单位产品液化功的变化情况,并与不带预冷的普通氮膨胀液化流程及丙烷预冷氮膨胀液化流程进行比较。结果表明,高含氮量下,一体化的流程能够大大降低系统功耗。     

Monitoring the moisture reduction and status of bioactive compounds in extra-virgin olive oil over the industrial filtration process

The aim of this study was to evaluate extra-virgin olive oil (EVOO) moisture and phenolic compounds content during industrial filtration, which is widely applied in the most olive-oil industries of the main producing countries of the Mediterranean as a final step prior to selling the oil. For this purpose, conventional filtration process was performed in duplicate using two lots (lot 1 and lot 2), for a total amount of 45,000 kg of EVOO each. The EVOOs were from the main Spanish olive varieties (Hojiblanca, Manzanilla, Picual, and Arbequina). Cloudy EVOOs were filtered using Vitacel^® L-90 and Filtracel^® EFC-950 as filter aids together with filtration tank. The moisture content was determined in unfiltered and filtered EVOOs. In addition, the individual phenolic compounds were qualitatively and quantitatively characterized by HPLC–ESI-TOF/MS. The results clearly showed that filtration sharply decreased moisture. Nevertheless, the time course of phenolic compounds during filtration differed for each family. Whereas phenolic alcohols and flavones decreased during filtration, secoiridoids tended to increase, while lignans were the least affected group. Although filtration can make EVOO brilliant and can increase its shelf life by reducing its moisture content, filtration sacrifices certain phenolic compounds which could affect EVOO oxidative stability and its nutritional quality. Consequently, to maintain olive-oil quality, producers need to take into account both moisture loss as well as the antioxidant content during EVOO filtration.     

Ochratoxin A contamination of the autochthonous dry-cured meat product “Slavonski Kulen” during a six-month production process

The aim of the study was to investigate OTA contamination of “Slavonski Kulen” during a six-month production process. Raw meat & spices (n = 7) used with the production and final products with either intact or damaged casings (n = 99) were sampled on the production day 30, 60, 90, 120, 150 and 180, and analysed for OTA presence using an enzyme-linked immunosorbent assay (ELISA) and high performance liquid chromatography with fluorescence detection (HPLC-FLD). No statistically significant differences (p > 0.05) were observed among the intact samples on any above-given production day, the maximal OTA value attributable to raw material contamination thereby being 3.18 μg/kg. As for the damaged samples, the mean OTA concentration established on the production day 180 was 7.92 ± 6.50 μg/kg, while the maximal observed OTA value equalled to 17.0 μg/kg. The results demonstrated that casing damaging witnessed during a long-term dry-cured meat products' ripening can result in OTA entry from the surface into the product, causing a significant OTA contamination.     

Sensibility analysis of propane deasphalting process variables

The deasphalting process with liquid propane is a process aimed at the use of oil waste, which is still present in the composition light fractions of hydrocarbons. The study makes use of the chemical process simulator Aspen Plus, through which the authors studied the influence of certain process variables. Through simulation the authors obtained two output streams, the top stream (deasphalted oil) and the background stream (asphaltic residue). The sensitivity analysis allows the verification of the influence of variables such as temperature, pressure, and mass flow rate of solvent in the process. The results show that temperature has an influence on the quality of the top product, with the increase of temperature the stream API degree increases, indicating the presence of mostly lightweight components. The oil-solvent ratio was shown to be an important variable in the process, because depending on this ratio the yield and the API degree of the top stream changes. However, it is important to note that the influence of these variables will depend on the physical characteristics of the waste fed.