VELOCITIES OF FALLING FILMS OF WATER ON TEFLON®, GLASS AND STAINLESS STEEL SURFACES

SUMMARY— The velocities of falling films of water on a stainless steel plate (8 by 1.5 ft) with No. 4 surface finish were measured by the salt conductivity method for flows varying from 50 to 250 Ib/min. The downflow times between 2 fixed electrodes, 6 feet apart on the plate, were measured by a Solu-Bridge flow timer. The film velocity measurements were made with the plate vertical and inclined 30 degrees from vertical, with water at 70 and 140°F. Another setup with a smaller plate (4 by 1.5 ft) and a constant flow of 45 lb/min was used to study the characteristics of falling films of water on Teflon, glass and stainless steel surfaces. The plates could be positioned at any positive or negative angle. The effects on wave structures were recorded photographically. The results showed highest velocities when the plates were vertical. Velocities increased with flow rate and temperature. At a given slope, film velocities were higher for the flow clinging to the underside of the surface than for the flow down the upper side of the surface.     

Cleaning effectiveness of chlorine-free detergents for use on dairy farms

A method for evaluating cleaning effect based on Bacillus cereus spores was developed and tested in a model system designed to resemble actual farm conditions. A test rig with four removable sampling plates was mounted in a milk line. The plates were attached at the end of T-junctions protruding either 1·5 or 3-times the milk pipe diameter from the main loop to reflect different levels of cleaning difficulty. In each cleaning test, B. cereus spores were applied to the four sampling plates to simulate soil. A series of cleaning tests was conducted at 35, 45, 55 and 65°C with six commercial chlorine-free, alkaline detergents; three liquid and three powder-based products. A commercial alkaline detergent with chlorine, a sodium hydroxide solution, a sodium hydroxider/hypochlorite solution and pure water were also tested. Triplicate tests were performed with each cleaning solution, giving a total of 120 cleaning tests. The cleaning effect was evaluated by comparing the number of spores before and after cleaning. At all temperatures, the two chlorine-based cleaning solutions gave significantly greater reductions in B. cereus spores than the chlorine-free products. All six commercial chlorine-free, alkaline detergents generally gave similar cleaning effects, with no differences in the performance of powder-based and liquid forms. The mechanical spore reduction effect with water alone was greater (1·5-1·8 log-units) than the additional chemical effect of sodium hydroxide or chlorine-free detergents (0·5-1·2 log-units). The chlorine-based solutions had a considerably more powerful chemical effect (2-4 log-units depending on temperature). In general, an increase in cleaning solution temperature up to 55°C gave a greater reduction in spores. A further increase to 65°C did not improve cleaning effectiveness.     

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.     

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.     

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.     

冷冻机立式水冷器污垢的塑料螺旋齿管自动清洗技术研究

冷冻机组立式水冷器的水垢损失每年高达十多亿元。依据其特低流速的特点，研究成功具有在线、连续自动清洗功能的塑料螺旋齿管技术。其原理是由冷凝管与螺旋齿管形成螺旋流道，使冷却水作快速螺旋线流动，其反作用给螺旋齿管形成较强的自转力矩。通过理论分析和多种结构参数的试验研究表明：污垢清洗能力强；自转力矩与冷却水流量二次方正比，较大的内管直径、较小的螺旋角有利于力矩强化，其中力矩最优化的螺旋齿管的力矩强化能达到塑料扭带的241％，可以在0．4m／s以上的流速下可靠应用；传热系数平均提高50％；制造简单。虽然螺旋齿管的阻力大，但是立式水冷器的落差很大。位能充裕，因此，具有很好的工程应用价值．     

Effects of home preparation on organophosphorus pesticide residues in raw cucumber

The effects of washing with tap water and different detergent solutions, storage at different temperatures and ultrasonic cleaning on organophosphorus pesticide (trichlorfon, dimethoate, dichlorvos, fenitrothion, and chlorpyrifos) residue levels in raw cucumber was investigated. Analysis was carried out by liquid chromatography–tandem mass spectrometry. Washing with detergent solutions proved more effective than tap water. The organophosphorus pesticides reduced from 31.1% to 98.8% after washing with detergent solutions for 20 min. Among detergent solutions, 5% sodium carbonate solution caused the greatest loss in trichlorfon and dimethoate, and 5% sodium bicarbonate solution caused the greatest loss in dichlorvos, fenitrothion and chlorpyrifos. Storage at 4 °C for 48 h caused pesticides reduction by 60.9–90.2%. Ultrasonic cleaning for 20 min lowered pesticides by 49.8–84.4%. The data indicated that home preparation is effective for the reduction of organophosphorus pesticide residues in raw cucumber and it is useful for reducing the dietary exposure.     

THE ECONOMIC USE OF DETERGENTS AND SANITIZERS IN THE DAIRY INDUSTRY

The various types of detergents, detergent sanitizers and sanitizers available on the market are first discussed with specific reference to the advantages and disadvantages of certain components. The cleaning operation is then broken down into various economic factors. The use of water and reclaimed water is detailed with hints on water-saving techniques. The energy factor is discussed with the pros and cons of hot versus cold cleaning. Concentrations and the automatic control of solutions are also covered, together with correct methods of detergent application and the reclaiming and re-use of detergent solutions. Finally, the problems of effluent discharge are covered and two forms of treatment outlined.     

超声波协同微酸性电解水对小龙虾净化及品质的影响

为了探究小龙虾（Procambarus clarkii）的净化工艺,采用超声波清洗协同微酸性电解水减菌技术对小龙虾进行活体净化处理。本文以小龙虾的菌落总数、芽孢总数及清洗液浊度为评价指标,以微酸性电解水的有效氯浓度、浸泡时间以及超声波功率为单因素水平,研究了微酸性电解水对小龙虾的减菌效果和超声波对小龙虾的清洗效果。结果表明:微酸性电解水的有效氯质量浓度越高,处理时间越长减菌效果越好。当微酸性电解水有效氯质量浓度60 mg/L,处理小龙虾50 min后菌落总数和芽孢总数分别下降了4.26 lg CFU/g、500 CFU/g,减菌率分别达到了99.99%、92.61%;使用超声波技术对小龙虾进行清洗处理,超声功率50 W处理50 min后小龙虾存活率为100%,清洗液浊度为181 NTU,显著优于对照组（P<0.05）。超声波技术协同微酸性电解水对小龙虾活体净化处理后,小龙虾初始菌由7.17 lg CFU/g降到3.52 lg CFU/g,净化效果显著优于车间气泡清洗工艺（P<0.05）。小龙虾净化前后的营养价值和品质无显著性差异（P>0.05）,该工艺合理有效。     

The role of surface tension of re-used caustic soda on the cleaning efficiency in dairy plants

During the cleaning in place with recycled cleaning solutions, an increase of suspended solids (SS) and a decrease of the surface tension (γ) of caustic soda (NaOH) solutions were observed for various types of dairy equipment. The decrease of γ was shown to result from the chemical reactions of the milk protein and fat with the cleaning solutions. In this work, the respective roles of SS and γ on the cleaning efficiency, cleanliness and cleaning rate were determined. The cleaning test consisted of an ultrafiltration membrane fouled with skimmed milk and cleaned using four NaOH-based solutions: newly prepared NaOH (high γ), re-used NaOH (low γ) with and without pre-clarification and a newly prepared commercial detergent solution. In the range of γ (28.7–74.0 mJ m⁻²) and SS (0.0–1.7 g kg⁻¹) studied, the cleaning efficiency and the membrane hydraulic cleanliness were similar (0.91–0.94 and 0.69–0.71, respectively). However, it was found that solutions with a low γ resulted in a much faster cleaning rate. The presence of SS was mainly detrimental to the cleaning rate. For an efficient cleaning rate, high pH and low γ were important. A re-used NaOH solution with both low γ and SS was as fast as the commercial detergent solution at the same temperature (50 °C).     

Response surface modelling for cleaning and disinfecting materials used in milking systems with electrolysed oxidizing water

Electrolysed oxidizing (EO) water is produced by passing a DC current through a weak sodium chloride solution, resulting in alkaline and acidic EO water. The goal of this research was to determine whether EO water could be used as an acceptable cleaning and disinfecting agent for materials used in pipeline milking systems. Small pieces of materials commonly used in milking systems were soiled using raw milk inoculated with a cocktail of four bacterial cultures similar to those commonly found in raw milk, and then cleaned by soaking in alkaline EO water followed by soaking in acidic EO water at various treatment times and temperatures. Effective treatment time and temperature combinations were determined by response surface design for a temperature range of 25–60°C and a time range of 5–20 min. Treated materials were evaluated by aerobic plate counts and ATP bioluminescence to assess the disinfecting and cleaning effectiveness of EO water. Most of the treatments at 60°C and several treatments at lower temperatures successfully removed all detectable bacteria and ATP. Overall, the results of this study indicated that EO water has the potential to be used as a cleaning and disinfecting agent for materials used in milking systems.     

Lethality of chlorine, chlorine dioxide, and a commercial produce sanitizer to Bacillus cereus and Pseudomonas in a liquid detergent, on stainless steel, and in biofilm

Many factors that are not fully understood may influence the effectiveness of sanitizer treatments for eliminating pathogens and spoilage microorganisms in food or detergent residues or in biofilms on food contact surfaces. This study was done to determine the sensitivities of Pseudomonas cells and Bacillus cereus cells and spores suspended in a liquid dishwashing detergent and inoculated onto the surface of stainless steel to treatment with chlorine, chlorine dioxide, and a commercial produce sanitizer (Fit). Cells and spores were incubated in a liquid dishwashing detergent for 16 to 18 h before treatment with sanitizers. At 50 microg/ml, chlorine dioxide killed a significantly higher number of Pseudomonas cells (3.82 log CFU/ml) than did chlorine (a reduction of 1.34 log CFU/ml). Stainless steel coupons were spot inoculated with Pseudomonas cells and B. cereus cells and spores, with water and 5% horse serum as carriers. Chlorine was more effective than chlorine dioxide in killing cells and spores of B. cereus suspended in horse serum. B. cereus biofilm on stainless steel coupons that were treated with chlorine dioxide or chlorine at 200 microg/ml had total population reductions (vegetative cells plus spores) of > or = 4.42 log CFU per coupon; the number of spores was reduced by > or = 3.80 log CFU per coupon. Fit (0.5%) was ineffective for killing spot-inoculated B. cereus and B. cereus in biofilm, but treatment with mixtures of Fit and chlorine dioxide caused greater reductions than did treatment with chlorine dioxide alone. In contrast, when chlorine was combined with Fit, the lethality of chlorine was completely lost. This study provides information on the survival and sanitizer sensitivity of Pseudomonas and B. cereus in a liquid dishwashing detergent, on the surface of stainless steel, and in a biofilm. This information will be useful for developing more effective strategies for cleaning and sanitizing contact surfaces in food preparation and processing environments.     

Comparison of surface sampling methods and cleanability assessment of stainless steel surfaces subjected or not to shot peening

The cleanability of AISI 304 stainless steel surfaces, indicated by the removal of Escherichia coli cells or Aspergillus niger spores was assessed by controlled inoculation and washing treatment of samples in standardised conditions. Two systems of recapture (Rodac plate technique and swabbing technique) were compared. Four industrial finishes, subjected or not to shot peening, contaminated at low concentration (1–10 cfu/cm²), and then washed with distilled water or alkaline detergent, were examined. The Rodac plate technique detected most of microorganisms inoculated (80% for E. coli cells and 67% for A. niger spores), whereas the swabbing technique recovered only 1% of the E. coli cells and 26% of the A. niger spores. Using the Rodac plate technique E. coli cells proved to be easily detachable from samples either with distilled water (98%) or alkaline detergent (>99%). For the surfaces contaminated with A. niger spores, the cleanability increased from 34% with distilled water to 77% with alkaline detergent. In these working conditions type of finish (shot treated or not) had no significant effect on cleanability of stainless steel.     

Polymers Decrease Cleaning Time of an Ultrafiltration Membrane Fouled with Pectin

An ultrafiltration system fouled by pectin solutions was used as a model system. The fouled membrane flux was fully restored by circulating 0.5% NaOH solution for 1 hr. By adding 0.003% polyethylene oxide) in 0.5% NaOH solution, the cleaning time required to fully recover flux of the fouled membrane was reduced to 2 min. The mechanism of improving cleaning efficiency may not be wholly attributed to the scouring effect of the polymer on the membrane surface. The cleaning and rinsing results suggest that polymers in cleaning solutions convert the pectin foulant into a foulant-polymer complex which could be readily rinsed from the membrane surface by water.     

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.     

EFFECT OF HIGH HYDROSTATIC PRESSURE ON SPORES OF GEOBACILLUS STEAROTHERMOPHILUS SUSPENDED IN SOYMILK

The inactivation of Geobacillus stearothermophilus spores (ATCC 7953) inoculated in soymilk was investigated using high hydrostatic pressure (550, 585 and 620 MPa) in combination with temperature (70, 80 and 90C) for selected times (2 s to 15 min). Inactivation of spores occurred at all selected treatments. Less than 10 CFU/mL of G. stearothermophilus were observed after 7 min of treatment at 620 MPa and 90C. An increase in the inactivation rate constant, at the highest pressure, was observed, resulting in a decrease in D values at all temperatures. D values were calculated as 10.6, 6.2 and 3.5 min for 70, 80 and 90C, respectively after pressurization at 620 MPa. z_p values decreased as temperature increased with values ranging from 142 to 238 MPa. The activation energy required for inactivation of G. stearothermophilus spores in soymilk, at the selected treatments, was in the range of 37.9–57.4 kJ/mol.     

Contributions to mechanical dishwashing. III. Dynamics of removal of protein residue from glass surfaces (author's transl)

Using tracer technique the removal of protein soil--dried casein resp. skin milk--from glass plates by mechanical dishwashing was investigated. Prerinsing for 2 min with cold tap water removes 91.25 percent of the quantity of casein originally present. When this prerinse is followed by 20 min main wash, the residual casein can be removed if at least 30g of detergent has been added to 131 water. Optimum inter-relation-ships of quantity of detergent added with time and temperature of the washing and rinse cycles are given. Dry protein residues from skim milk are more easily removed than casein residues, probably because the salts and lactose dried together with the proteins facilitate the cleaning.     

脱臭系统清洗实践

在油脂精炼过程中设备触油表面会产生油垢,导致传热传质效果下降,而提高脱臭温度会造成油脂质量下降,因此需要对脱臭系统进行清洗。从清洗机制、清洗剂种类、清洗程序等方面介绍了脱臭系统的清洗实践。油脂精炼厂清洗脱臭系统可先采用碱液和高压水冲洗,再请专业公司采用溶解性清洗剂进行清洗,清洗效果要求被清洗的金属表面除垢率大于95%、无点蚀及过洗现象、腐蚀率小于或等于1.0 g/(m²·h)。在油脂精炼生产中需按照操作规程进行操作和维护,设置好预防清洗的工艺控制参数。     

生孢梭菌芽孢萌发条件的优化

本文研究了不同温度、时间和pH值条件下,生孢梭菌芽孢萌发所需的最佳条件.本研究将活化传代好的生孢梭菌菌液培养7 d,多次离心后,加入无菌水制成生孢梭菌芽孢悬浮液,处理温度为70℃～90℃,处理时间为5～25 min,处理pH值为4～8,用平板计数法观察计算不同条件处理后的芽孢萌发率,用响应面优化法对影响生孢梭菌芽孢萌发...     

Potentiation of the lethal effect of peroxygen on Bacillus cereus spores by alkali and enzyme wash

Bacillus cereus present in pipes and heat-exchangers represents a potential quality problem for dairy industry. The peroxygen-containing disinfectants investigated had only negligible sporicidal effect when applied at the recommended in-use temperature and concentration. However, cleaning agents used before disinfection potentiated their lethal activity. Pre-exposure of B. cereus spores to 1% sodium hydroxide at temperatures over 40 degrees C increased the sporicidal effect of the peroxygen-containing disinfectant. The effect was dependent on the alkali concentration and the temperature. Also, a significant potentiating activity of an enzyme-based cleaning agent was obtained, but the effect was smaller than for alkali treatment. The results indicated that disinfectants based on peroxygen can be used to eliminate B. cereus spores at non-corrosive temperatures and concentrations if the surfaces are cleaned with alkali or enzyme-based disinfectants prior to disinfection.