REMOVAL KINETICS OF BACILLUS CEREUS SPORES FROM STAINLESS STEEL PIPES UNDER CIP PROCEDURE: INFLUENCE OF SOILING AND CLEANING CONDITIONS

Cleaning efficiency is of prime importance for food industries to ensure both the quality and safety of the products. The removal kinetics of Bacillus cereus spores adhering to unheated stainless steel pipes was studied under turbulent flow conditions (Reynolds’number of 77500 and 116300) in order to be close to those encountered in industrial practice. The experimental data was fitted using a hyperbolic tangent model. Variance analysis was then performed to underline any potential effects on the kinetics of the processing parameters, such as soiling conditions, soiling media and mean walls shear stress during cleaning. A significant influence of the adhesion medium (milk or saline) is shown at the level of spore removal (P < 0.001). This trend could probably be explained by the change in the surface properties of spores and stainless steel surfaces when covered by milk macromolecules. After milk soiling in turbulent flow conditions, removal efficiency was enhanced by a factor of 2.5 to remove 50% of the initial spore contamination and by a factor of 2 for the remaining spores after 30 min of cleaning. No effect of the two mean wall shear stresses (9.4 and 19.1 Pa) has been identified. The removal kinetic model proposed here could now permit the effect on the cleaning efficiency of a wide range of CIP conditions to be tested.     

Application of turbulent pulsating flows to the bacterial removal during a cleaning in place procedure. Part 1: Experimental analysis of wall shear stress in a cylindrical pipe

The effects of pulsating turbulent flows on wall shear stress components were investigated in a straight pipe using the non-intrusive electrochemical method. Experiments were made using a new pulsation generator system which allows high amplitude pulsations in addition to a perfect stability of the installation. Maximum pulsation frequency equal to 2.86 Hz is used, above which fluid inertia dominates over most part of the flow field.Analysis showed that pulsating flows induce an increase of local velocity gradient at the wall pipe. This result is explained by the periodic renewal of the boundary layers. Spectral analysis showed high increasing rates of the fluctuation energy for the different pulsating conditions in comparison with a steady flow. The tested condition involving a recirculation flow induced a modification in the energy dissipation cascade, which can be explained by the redistribution of eddies size near the wall.     

AN APPROACH to STUDY and MODEL the HYDRODYNAMIC CLEANING EFFECT

A sensor has been developed for continuous measurements of the removal of deposit. the sensor, which was based on heat transfer measurements, was also able to measure the wall shear stress. The device was used to study the mechanical effect during cleaning. It was found that the removal rate of deposits, at a surface, could be scaled by the mean wall shear stress. Measurements were performed under both laminar and turbulent flow conditions. the turbulent fluctuations did not influence the removal rate.     

鼓泡式鱼类清洗机管路湍流数值模拟与优化

采用Fluent软件对鼓泡管路中的分流管内部流场进行数值模拟,选用标准k-ε湍流模型模拟分流管上每个喷气口气体的流速分布图,当分流管长为40cm时,每个喷气口气体的流速相近,产生的气泡均匀、可控。通过对分流管上的喷气孔径、孔距等相关参数进行数值模拟,使用Mixture多相流模型、扩展的标准k-ε湍流模型模拟不同气流速度对气体体积分数、湍流动能、湍流耗散率的影响。结果表明:气流流速与气体体积分数、湍流动能、湍流耗散率具有正相关性,当鼓泡管路中参考气流速度8m/s、喷气孔径6mm、喷气孔径间距70mm时,湍流动能转化比最高(67.7%)。验证实验表明:清洗时间、气流流量、清洗量对鲫鱼表面和腹腔的清洗效果影响显著,当清洗时间170s、气流流量145L/min、清洗量1.5kg时,清洗效果达92分。     

Cleaning of dairy HTST plate heat exchangers: optimization of the single-stage procedure

The influence of detergent concentration, temperature and flow rate on the time to remove milk deposits from the heated surfaces of a plate heat exchanger was studied. The results indicate that the main reduction in cleaning time was produced by small increases in the passage mean velocity of flow in the range 0.2 to 0.5 m/s. Increasing the temperature to 75 °C also resulted in substantial reductions in cleaning time. Variations in concentration, for which there was an optimum, had the least effect on cleaning time of the parameters investigated.     

Circulation cleaning of a plate heat exchanger fouled by tomato juice

The effect of a change in flow rate of a 2% w/w caustic soda solution on the circulation cleaning of a plate heat exchanger fouled with diluted tomato paste has been investigated at a temperature of 90°C and fixed circulation cleaning times of 5 and 10 min.
For both circulation cleaning times a transition point was noted in the range 2.75–2.86 1/min (Reynolds number range 6600–6300, shear stress range 0.77–0.82 N/m²). Below the transition point the effect of flow rate on cleaning efficiency was minimal, but at flow rates above the transition point there was a marked increase in cleaning efficiency as the flow rate (and hence shear stress at the surface) increased.     

Laminar flow cleaning of gelatinised,partially hydrolysed starch

The cleanability of food contact materials is, among others, determined by the physico-chemical properties of the soiling material. In the current study, starch of different origin was gelatinised and partially hydrolysed with diastase. The degree of hydrolysis was determined as the reducing capacity in terms of dextrose equivalents, and by the changes in apparent viscosity and surface tension. After spreading the starch paste on electropolished stainless steel coupons and subsequent drying, the removal was studied with a laboratory flow cell. These cleaning tests revealed a higher cleaning effectivity for smaller dextrins, which can be attributed to corresponding changes in solubility. Furthermore, the addition of commercially available diastase to demineralised water increased the cleaning effectivity of starch and dextrin soils at 25 °C. The results indicate that smaller starch breakdown products require reduced energy for removal so that cleaning processes can be adequately adjusted.     

STUDIES ON FLOWDYNAMICS OF FALLING FILMS OF WATER AND ITS EFFECT ON CLEANING OF STAINLESS STEEL

SUMMARY— Factors such as inclination angle of the test surface, flow rate and temperature and composition of cleaning solutions were examined for their influence on cleaning an 18-in.-wide sheet of No. 4 finish stainless steel by gravity flow of falling films of water and detergent solutions. A suspension of B. subtilis spores was used to contaminate the test surface. After a cleaning treatment, the percentage of spores remaining as measured by a direct surface agar plate method IDSAPI was used to calculate cleaning efficiency. Flows of water and cleaning solutions ranged from 50 to 250 lb/min. After detergent solutions, a post-rinse with water at 100°F for 5 min was used. Another setup with a smaller plate and a constant flow rate of 45 lb/min was used to study the effect on cleaning of varying plate angle between the limits of 60 degrees either side of vertical. Washing time was standardized at 10 min for the large plate and 15 min for the smaller one. Results indicated that cleaning improved with temperature, flow rate and with the presence of acid or alkaline cleaning agents. Cleaning was most effective when the plates were in the vertical position.     

Facilitation of cleaning of alumina surfaces fouled with heat-treated bovine serum albumin by ozone treatment

Facilitation of cleaning of alumina (A12O3) particles fouled with heat-treated bovine serum albumin (BSA), which contains sulfhydryl groups on the molecule, by gaseous ozone was studied. With increasing temperature of heat treatment, the amount of adsorbed BSA onto A12O3 surfaces increased, whereas the rate of BSA desorption during alkali cleaning decreased markedly, resulting in the larger amounts of BSA remaining on 12O3 surfaces. No significant amounts of BSA were removed from A12O3 surfaces by alkali cleaning alone when treated at temperatures above 120 degrees C. Before alkali cleaning, the heat-treated, BSA-fouled AI2O3 at 150 degrees C were treated with 0.05 to 0.30% (vol/vol) gaseous ozone at room temperature. Ozone pretreatment markedly accelerated the rate of BSA desorption during subsequent alkali cleaning. The effect of ozone pretreatment on BSA removal depended on the concentration of ozone and treatment time and hence on the total amount of ozone supplied. The molecular weight (MW) of desorbed BSA during alkali cleaning without ozone pretreatment coincided with the MW of the native BSA, whereas the MW of desorbed BSA during the combined ozone-alkali cleaning was lower than the MW of the native BSA. This indicated that the heat-treated BSA molecules adsorbed on A12O3 were partially decomposed into some fragments by ozone pretreatment, resulting in the facilitation of the removal of BSA during alkali cleaning.     

油茶籽粕鸭蛋去污除菌清洗剂应用效果的研究

目的 研究油茶籽粕去污除菌清洗剂的应用效果。方法 分别用人工污染鸭蛋和鲜鸭蛋为试验材料, 采用油茶籽粕鸭蛋去污除菌清洗剂(CX)、氧净洗液(YX)、自来水(SX)进行清洗处理, 比较其白度提高率、重量减轻率、除菌率和蛋新鲜度品质指标, 并以未加清洗处理作为对照(CK), 进行去污除菌效果的评价。 结果 CX清洗人工污染蛋的感官评分(88±3)分、白度提高率(18.59±0.18)%、重量减轻率(0.44±0.03)%, 菌落总数仅有(3.87±0.32) lg CFU/蛋壳(除菌率99%), 其去污除菌效果优于CK和SX清洗。CX清洗鲜鸭蛋, 其白度提高率(14.568±4.309)%, 重量减轻率(0.6112±0.0032)%, 洁蛋清洗水培养物的OD660为0.178±0.0054。清洗后的鸭蛋其保藏期内气室高度、哈夫值单位、蛋黄指数指标均优于YX、SX。结论 本研究所用的油茶籽粕鸭蛋去污除菌清洗剂清洁效果强, 保鲜力度高, 可延长鸭蛋的货架期     

Predicting cleaning time of ventilation duct systems in the food industry

The quality of air within factory buildings is controlled by many food manufacturers. Ventilation system hygiene must be regularly cleaning to prevent the build up of dust, product or condensate that may provide a focus for microbial growth. In the present study we predict the particle deposition velocity in ventilation ducts of three different food factories. At these locations, during several days, aerosol particle number and mass size distribution were measured using optical particle counter and cascade impactor, respectively. The concentration of particulate matter of aerodynamic diameters in the size range 0.3-20 μm varied from 0.2 to 1.7 μg m⁻³. The measured mass concentration and the predicted particle deposition velocity were used to calculate the deposited particle mass flux (DMF) in the ventilation ducts of each site.The results indicate that the DMF at the floor is about 2-20 times larger than that at vertical walls. Thus, the deposited particle mass on the floor is sufficient to check whether a ventilation duct should be cleaned. According to the chosen cleaning initiation criteria for ducts, ventilation systems would take approximately 1-9 years to meet the cleaning time. So, cleaning procedures and maintenance intervals are strongly influenced by several parameters, such as flow conditions, particle concentration, characteristics of the ventilation duct and the filter efficiency. The modeling approach combined with mass concentration measurements enables the analysis and the quantification of the influence of these parameters.     

Influence of different cleaning and sanitisation procedures on the removal of adhered Bacillus cereus spores

The effectiveness of nine different sanitation procedures for the removal and control of adhered Bacillus cereus spores isolated from the dairy industry was evaluated. Four sets of experiments were produced by varying the conditioning matrix (water and UHT whole milk) and the inoculation medium of the pool of B. cereus spores (water and UHT whole milk), resulting in E_water/water, E_water/milk, E_milk/water, and E_milk/milk. The experiments were repeated three times and evaluated by ANOVA and Tukey's test. Sanitisation with sodium hypochlorite was more effective than peracetic acid for removal of adhesion, especially when associated with a cleaning procedure, with counts below the limit of detection (<0.7 log cfu cm⁻²). The experiments formed when the pool of spores was inoculated on water (E_water/water and E_milk/water) presented greater resistance against the sanitation procedures studied. These results highlight the importance of the water quality used in the industries for sanitation of equipment.     

Determination of cleaning end of dairy protein fouling using an online system combining ultrasonic and classification methods

Fouling and cleaning of heat exchangers in food industry are severe and costly issues and of high importance. In this study, a planar heat exchanger was constructed to produce and clean milk protein fouling similar to industry. Using a combination of an ultrasonic measuring method and classification machines cleaning should be monitored online to adapt cleaning time. After reproducible fouling deposit was built, cleaning started which was monitored using an ultrasonic measuring unit. The measured ultrasonic signal was analyzed for seven acoustic features and fed together with temperature and mass flow rate (both measured) into a classification method for decision of fouling presence or absence. For classification, artificial neural network (ANN) and support vector machine (SVM) was applied displaying detection accuracies of more than 80 % (ANN) and 94 % (SVM), respectively. Besides, the slope change of the seven acoustic features was monitored with time resulting in a cleaning time of at least 21?±?4 min. The cleaning time determined by the new sensor system is comparable with previously determined cleaning times for this setup. This study demonstrated that ultrasound based sensor systems offer a new tool to determine presence or absence of fouling and to monitor cleaning processes in the food industry with high accuracy.     

Removal of Pseudomonas putida biofilm and associated extracellular polymeric substances from stainless steel by alkali cleaning

Alkali (NaOH)-based compounds are commonly used in the food industry to clean food contact surfaces. However, little information is available on the ability of alkali and alkali-based cleaning compounds to remove extracellular polymeric substances (EPS) produced by biofilm bacteria. The objectives of this study were to determine the temperature and NaOH concentration necessary to remove biofilm EPS from stainless steel under turbulent flow conditions (clean-in-place simulation) and to determine the ability of a commercial alkaline cleaner to remove biofilm EPS from stainless steel when applied under static conditions without heat. Biofilms were produced by growing Pseudomonas putida on stainless steel for 72 h at 25 degrees C in a 1:10 dilution of Trypticase soy broth. The biofilms were treated using NaOH at concentrations of 1.28 to 6.0% and temperatures ranging from 66 to 70 degrees C. Other biofilms were treated with commercial alkaline cleaner at 25 or 4 degrees C for 1 to 30 min. Removal of EPS was determined by direct microscopic observation of samples stained with fluorescent-labeled peanut agglutinin lectin. Treatment with 1.2% NaOH at 66 degrees C for 3 min was insufficient to remove biofilm EPS. A minimum of 2.5% NaOH at 66 degrees C and 2.0% NaOH at 68 degrees C for 3 min were both effective for EPS removal. Commercial alkaline cleaner removed over 99% of biofilm EPS within 1 min at 4 and 25 degrees C under static conditions. Selection of appropriated cleaning agent formulation and use at recommended concentrations and temperatures is critical for removal of biofilm EPS from stainless steel.     

牡蛎超声波清洗工艺的初步研究

牡蛎经过漂洗后进行超声波清洗,以去除杂质比重为主要指标,探讨了超声波频率、处理时间、超声方式对牡蛎清洗效果的影响。结果表明:牡蛎超声波清洗的最佳工艺条件为低频(26kHz),处理时间5min,去除杂质比重能够达到3.73%(占清洗前牡蛎重)。该工艺条件下牡蛎无死亡,生态冰温保活9d后,存活率依然达到95%以上。     

基于EDEM的组合清理筛筛分仿真和性能分析

为优化平面回转筛的结构和工艺参数，提高组合清理筛的筛分处理量和筛分效率，采用离散元软件EDEM对组合清理筛的平面回转筛分过程进行模拟仿真，探究颗粒在筛分过程中的运动规律，并仿真分析了回转半径、回转速度和筛面倾角对组合清理筛筛分处理量和筛分效率的影响。结果表明，提高回转半径、回转速度和筛面倾角均可提高组合清理筛筛分处理量，但会降低筛分效率（物料提取率和除杂率）。在回转速度为420 r/min左右、回转半径为20 mm左右、筛面倾角为7°~ 9°时，组合清理筛的筛分效率较好，筛分处理量也较大。     

Application of an ultrasound field in chemical cleaning of ceramic tubular membrane fouled with whey proteins

Chemical cleaning of a severe in-pore-fouling may be improved by applying an ultrasound (US) field in a cleaning-in-place (CIP) system, under both the batch and flow conditions. This study is concerned with the cleaning of a 200-nm ceramic membrane, fouled with whey proteins, in an US field of relatively low frequency of 35 kHz, without applying a transmembrane pressure (TMP) and cross-flow velocity. Two types of cleaning agent solutions of different concentrations were applied: alkali (NaOH) and a mixture of commercial detergents (P3-Ultrasil 67 and 69) at a sonication time of 30 min. It was found that the application of US was less effective in the combination with sodium hydroxide than with the mixture of commercial detergents. Using US in a mixture of 0.25% w/w P3-Ultrasil 67 and 0.4% w/w P3-Ultrasil 69 resulted in the highest flux recovery of 86.5 ± 2.9%, after 30 min of sonication, and produced an overall efficiency of 96.3 ± 0.4%, after the second sonication. It was concluded that the application of the US field in a batch mode, combined with the mentioned chemical agents, can significantly improve the cleaning efficiency.     

滚筛式自动除杂选果装置的设计

研制了番茄酱生产线自动除杂选果装置,由支架、链轮、链条滚筛网带、出料托盘、减速电机、光电传感器及自控系统构成。通过试验分析,该自动选果装置平均选果率高达97%和块状杂质除杂率平均为78%,尤其是对带状杂质几乎可以达到99%的除杂率,适合连续处理大量含杂质原料,满足生产实际需求。     

Wet electroscrubbers for state of the art gas cleaning

Current trends observed in air pollution control technology are closely related to the development of new, more efficient hybrid systems, i.e., those, which simultaneously utilize two or more physical mechanisms for dust or gaseous contaminants removal. These systems can operate more economically than conventional devices, especially in the removal of PM2.5 particles. The electrostatic scrubber (electroscrubber), discussed in this paper, is one of such types of devices, which combines advantages of electrostatic precipitators and inertial wet scrubbers, and removes many shortcomings inherent to both of these systems operating independently. The electroscrubber is a device in which Coulomb attraction or repulsion forces between electrically charged scrubbing droplets (collector) and dust particles are utilized for the removal of particles from a gas. Unlike wet electrostatic precipitators in which particles are precipitated only on the collection electrode, in electroscrubbers, the collection of dust particles takes place in the entire precipitator chamber. Compared to inertial scrubbers, the electroscrubbers can operate at lower droplet velocities, but the collection efficiency for a single droplet can be larger than 1. The paper reviews the state-of-the-art of wet electrostatic scrubbing (electroscrubbing) technique used for gas cleaning from dust or smoke particles. Three groups of problems are discussed: (1) The fundamental problems concerning the charged dust particle deposition on a charged collector, usually a drop, with a focus on different models describing the process. (2) The experimental works of fundamental importance to our knowledge referring to the scrubbing process, which can be used for validating the theory. (3) The laboratory demonstrations and industrial tests of different constructions of electroscrubbers designed for effective gas cleaning. The electroscrubber is not designed to replace wet or dry electrostatic precipitators but can be used as a complementary device following the last stage of conventional electrostatic precipitator, which helps to remove submicron particles. It was shown in the paper that a higher collection efficiency of an electroscrubber could be obtained for higher values of Coulomb number (i.e., higher electric charges on the collector and particle), and for a Stokes number lower than5 (i.e., low particle-collector relative velocity).     

电捕集原理在空气净化技术中的应用

分析了电捕集除尘原理用于空气净化的可行性，指出了空气净化与工业除尘的异同点，根据捕集效率方程，讨论了有效驱进速度、集尘面积、气流流量对空气净化器工作效率的影响，给出了空气净化器的设计要点。