repaPetihWContents1 Why Submit Foods to X-ray Inspection?2 How Does an X-ray System Catch Contaminants?3 Factors Affecting the Sensitivity of X-ray Inspection2W h i t e P a p e rFood manufacturers are under increasing consumer and legislative pressure to provide safe food. One of the tools that helps to maintain food safety is x-ray inspection.This white paper looks at the use of x-ray inspection systems to eliminate physical contaminants on pumped food lines. It begins with a short introduction to x-ray inspection and why it’s used in the food-processing industry. It goes on to consider the factors that affect the sensitivity of x-ray inspection, the effectiveness of x-ray inspection at different points on the production line, and the ease with which the technology can be applied to production lines based on pumped product.After reviewing the factors that production line managers should take into account when considering installing an x-ray inspection system, the white paper suggests typical applications, and then looks at points to consider when using x-ray inspection for processed meat and poultry lines and for lines involving slurries, semi-solids, and fluids.Contamination Detection in Pumped Foods1. Why Submit Foods to X-ray Inspection?X-ray inspection systems keep foods safe by offering unsurpassed detection of physical contaminants. No other technology detects such a wide range ofcontaminants such as stone, metal, glass, bone, and high-density plastic and rubber.Incorporating x-ray inspection systems into a company-wide product-safety program helpsmanufacturers comply with national and international regulations - such as HACCP (Hazard Analysis Critical Control Point) - as well as standards set by retailers.Typical contaminants2. How Does an X-ray System Catch Contaminants?An x-ray system is essentially a scanning device. When a product passes through the x-ray system, the internal sensors capture a grey-scale image of the product. The software within the x-ray system analyzes the image and compares it to a predetermined acceptance standard.On the basis of the comparison, it accepts or rejects the image. In the case of a rejection, the software sends a signal to an automatic reject system/valve which removes the product from the production line.X-ray image of processed chickenWhite PaperMETTLER TOLEDO3Fig 1: X-ray image of a ready meal - lots of varities of greys make it more difficult to detect a contaminantFig 2: X-ray image of pumped caramel - it is easier to detect a contaminant in a homogenous product4. Establishing Critical Control Point for an X-ray System on a Production LineTo be fully effective, x-ray inspection should be part of a company-wide approach to product safety and part of a product inspection program. Implementing x-ray inspection into such a program helps foodmanufacturers to achieve compliance with standards such as HACCP .HACCP consists of seven steps known as principles.1. Conduct a hazard analysis2. Identify critical control point (CCP)3. Establish critical limits for each CCP4. Establish CCP monitoring requirements5. Establish corrective actions6. Establish record-keeping procedures7. Establish procedures to verify the system is workingas intended The second of those principles – identifying the critical control point (CCP) – helps to choose the best location to apply x-ray inspection on a production line. A CCP is a step or process that’s essential to product safety. It’s the point at which control must be applied to reduce the risk of contamination to acceptable levels.To find out more about selecting CCP, please read the white paper “How to select CCP for x-ray systems” (/usxray-ccp).White PaperMETTLER TOLEDO3. Factors Affecting the Sensitivity of X-ray InspectionThe ease with which food contaminants can be identified by x-ray inspection depends on various factors such as product density, product thickness, and product homogeneity.Product DensityProduct density determines the depth of grey in the grey-scale image. The denser the product, the darker the grey.To be detectable to x-ray inspection, a contaminant has to be denser than the product in which it’s embedded. That means it will absorb more x-rays than thesurrounding product, and show up on the grey-scale image as an area that’s darker than its surroundings. In other words, any contaminant with a density similar to, or less than, that of the product in which it’s embedded is incapable of being detected by x-ray inspection.Product ThicknessAs the product thickness in the path of the x-ray beam increases, so does its overall level of absorption. That makes detection more difficult. A contaminant in ashallow layer of product flowing through a pipe is easier to detect than a contaminant hidden inside a finished sealed pack. In general, the shallower the depth of product, the better the sensitivity of x-ray inspection.Product HomogeneityThe texture and consistency of a food product has an effect on x-ray sensitivity. A product with components of varying density, such as a ready meal, shows up in a greyscale image as a variety of greys (Fig 1). The more components there are, the wider the range of greys. Analyzing the image for contaminants is harder because the software has to pick out the tell-tale dark speck of a contaminant from an image containing numerous shades of grey. The more homogeneous the product, such as liquid caramel, the easier it is to spot contaminants (Fig 2).Many other factors can affect the sensitivity of an x-ray system. To find out more about the factors limiting the sensitivity of detection, please read “The X-ray Inspection Guide” (/usxray-guide).44.2 X-ray Inspection of Processed FoodWhen installed during or after the food processing or before the filling process, x-ray inspection of pumped products is ideal as they tend to be homogeneous - their texture and density are much more uniform. And since the product is already flowing through a pipe, it can easily be presented for inspection in shallow depths by narrowing the gauge or altering the cross-section of the pipe.X-ray systems for pumped products can be used at different stages on a production line depending on the identified CCPs.5. Applying X-ray Inspection to Pumped Food ProductsPumped products typically include meat and poultry as well as slurries, semi-solids and fluids at any stage prior to final packaging.Connecting x-ray inspection equipment to an existing piped production line isn’t complicated. Standard fittings are used to attach the pipe through which the pumped products passes to the manifold of the x-ray machine. The manifold typically tapers the round production-line pipe to a rectangular-shaped inspection window with an equivalent throughput volume. The rectangular section is where the x-ray beam scans the flowing product. The depth of product at this point is typically between 35mm to 50mm. When the software detects a contaminant, it diverts the product from the pipe via a reject diverter valve.A typical x-ray pipeline systemW h i t e P a p e rOnce the CCPs on a production line are identified, other factors such as practicality and cost-effectiveness need to be taken into account to select the ideal location for an x-ray system. There are occasions where it would be necessary to install more than just one x-ray system on the production line and that’s why there is no single solution that’s right for every production line.For this white paper, we will only focus on the inspection of pumped food products.4.1 X-ray Inspection at the Beginning of the Production LineDetection levels are typically better in the early stages of the production process where unprocessed pumped product can be presented in a shallower depth and with a more uniform texture. As the line progresses, thenature of contaminants can change too. Each processing step can introduce new contaminants, or break existing contaminants down into smaller, less detectable pieces.X-ray inspection of ground meatAt each stage of the production process, the value of the product increases. For that reason, food manufacturers find it more cost-effective to reject contaminated product before it’s been processed or sealed in its final packaging.Catching contaminants early is not just more efficient in reducing product waste and costs, it also helps prevent damage to processing equipment caused by big contaminants, which could in turn introduce more contaminants. Additionally, when installed early in the production process it can serve as a check on suppliers’ quality control.White PaperMETTLER TOLEDO6. Factors to Consider When Installing X-rayInspectionProduct passing through a pipe performs slightly differently to product travelling on a conveyor. To make the most of x-ray inspection, you need to take the following factors into account:Air BubblesAir bubbles in a pumped product are tiny voids – zones containing no product. Voids absorb fewer x-rays so they appear as lighter areas on grey-scale x-ray images. The contrast at the edges of these lighter areas can trigger the x-ray software into thinking that it detected a contaminant, causing false rejects. Since air bubbles reduce the depth of grey, they could lighten the color of any contaminants directly behind or in front. That makes the contaminants harder to detect.Air bubbles are common in pumped meat and poultry appications but are not difficult to eliminate with the right x-ray system design. A vacuum filler pump, for example, generates a constant, homogeneous flow with minimal air bubbles.Slurries and other viscous products do not normally contain air bubbles when pumped through a pipe. Speed VariationsA well-designed x-ray system will automatically adapt to changes in the flow rate of the customer product. It adjusts the scan speed and the associated reject timing in accordance with a speed signal from the production-line pump.Location on the Production LineAs mentioned previously, x-ray inspection can be applied anywhere on a production line containing pumped products. But the earlier you apply it, the better. The value of rejected product is lower, plus you may be able to recover the product and feed it back into the line after removal of the contaminants.A very common location is at the start of the production process when product value is low and the risk of contaminants from incoming raw product is at its highest. Using x-ray inspection at this stage also lets you monitor suppliers’ quality control.7. Typical ApplicationsA huge range of processed food products pass through pipelines. Typical applications could be:Meat andPoultrywhole muscle, minced meats forsausages, pies, pâtésBakery jams, syrups, cake mix and fillings Dairy butter, ice cream, yogurt, cottagecheeseFruit andVegetablespurées, mousses, juices,smoothies, chopped fruit andvegetablesFish andSeafoodfish spread, processed fish forready-mealsConfectionery melted chocolate, nougats, toffees Ready-Meals sauces, soups, pie fillingsWe can divide these food products into two broad classes: (1) meat and poultry, (2) slurries, semi-solids, and fluids. We’ll look at them separately.7.1 Meat and Poultry ApplicationsTypical pumped meat and poultry products include ground meat, sausage meat, and poultry trims such as breast fillets and thigh meat. Bone contaminants are by far the most common ones, although lead or steel shot (buck shot), needles, and teeth are also common. Depending on the pumped meat or poultry application, x-ray inspection can detect metal down to 0.8mm, and calcified bone and tooth down to 2mm. The maximum pipe diameter for meat applications is 75mm (3 inches) because narrower pipes make it easier to identify fragments of bone.White PaperMETTLER TOLEDO56W h i t e P a p e rSince chicken bones are less dense than red meat bones, they’re harder to detect. The density of chicken bone tends to be closer to that of the chicken meat in which it lies. On a grey-scale image, the difference between the grey of the meat and the grey of the bone is less obvious.Let’s look at some important points to consider when using x-ray inspection for pumped meat and poultry applications:• High volume throughput of up to 10 tons an hour • Contaminants will be removed before adding further value to the product through processing• Rejected product could be reworked and reused (depending on the application)•Reject portion sizes are larger than for aconveyorized x-ray system because the pipeline reject mechanism can’t isolate a single item such as a chicken breast fillet•Faster flows increase reject portion sizes – up to 2lb to 3lb of rejected product when running at 10 tons an hour through a 76mm (3-inch) pipe •High rejection rate due to frequency of bone contaminants in meat and poultry products – an acceptable reject level needs to be defined7.2 Slurries, Semi-solids and FluidsX-ray inspection is especially useful for products that cannot be sieved. These are products such as textured fruit purées and yogurts containing fruit chunks. Sieving removes physical contaminants by catching anything that’s too big to fit through the sieve mesh and is used mainly for liquid applications like milk. X-ray inspection of pumped products is a good alternative for catching physical contaminants where sieving can’t be used.The contaminants within slurries, semi-solids, and fluids are varied. Depending on the application, x-rayinspection can detect metal down to 0.8mm, glass and stone down to 2mm, and dense plastic down to 4mm. The maximum pipe diameter for these more fluid applications is 100mm (4 inches).Contaminated slurries, semi-solids, and fluids are typically rejected from the pipe through a diverter ball valve. The ball valve automatically removescontaminated product without creating a back pressure in the system.The sanitary design of an x-ray system inspecting slurries, semi-solids, and fluids is very important. For more efficient cleaning, aseptic x-ray inspection systems are available. An aseptic design incorporates steam-cleaning ports for destruction of pathogenic bacteria growth. For dairy applications, there are x-ray inspection systems that are certified to AMI and 3-A Sanitary Standards.Let’s look at some important points to consider when using x-ray inspection for slurries, semi-solids and fluids:•High volume throughput of up to 20 tons an hour – larger than for meat and poultry because pipeline diameters are typically greater and fluids can travel faster through pipes• Contaminants will be removed before adding further value to the product through processing• Rejected product can be reworked and reused (depending on the application)•Faster flows increase reject portion sizes – up to 5kg or more of product when running at 20 tons an hour through a 100mm (4-inch) pipeWhite PaperMETTLER TOLEDO8. ConclusionFor many years, x-ray inspection has proven itseffectiveness at eliminating contaminants fromprocessed and packaged food products. Theeffectiveness of x-ray inspection systems dependson the product density, thickness and homogeneityof the inspected product.Since pumped products tend to be more homogeneous,it’s easy to adjust their depth by altering the size orshape of the pipe through which they flow. That makespumped products an ideal application for x-rayinspection, offering food manufacturers excellentlevels of contaminant detection.Pumped products on a food processing line tendto occur early in the production process before amanufacturer has added further value to the productthrough processing and packaging. Since product valueis lower at this point, this location is very common forx-ray inspection system for removing contaminants.Early removal of contaminants has two otheradvantages: it protects valuable processing equipmentfrom damage further downstream, and it serves asa check on suppliers’ quality control.Installing x-ray inspection equipment on a pumpedproduction line is a simple process. A pressure vacuumpump will eliminate air bubbles especially in meat andpoultry applications. A well-designed x-ray inspectionsystem can also automatically change the scanningspeed and the reject timings to match the customer’sflow rate.X-ray inspection is a versatile technology that’s suitablefor the inspection of a wide range of pumped foodproducts at CCPs on a food processing line. It helpsmaintain product safety and brand reputation, andcan protect valuable equipment from damage.7White PaperMETTLER TOLEDOFor more informationMettler Toledo Safeline 6005 Benjamin Road Tampa FL 33634 USATel. 813-889-9500Toll Free 800-447-4439Fax. 813-881-0840Email:*********************Subject to technical changes©05/2011 Mettler-Toledo Safeline Printed in the US/safelineusOn-Demand X-ray Webinars 24/7Our on-demand webinars give you the opportunity to learn more about x-ray inspection - at your own convenience!To view all our on-demand webinars please visit:/pi-ondemandFurther Information about X-ray InspectionFREE Technical Guide Make an informed decisionMETTLER TOLEDO has published an authoritative product inspection guide for x-ray inspection systems.The 73 page guide enables you to select the right x-ray inspection system for your production line. It supports you to install an all-encompassing product inspection program and to achieve compliance with standards, regulations and legislation.Register today for your FREE copy:/pius-guidesFREE White PapersHow Safe is X-ray Inspection of Food?Some of the most popular misconceptions about x-ray inspection of food are tackled in this White Paper. It is an indispensable white paper for food manufacturers who consider x-ray inspection to comply with food-safety regulations and legislations.Register today for your Free copy: /xrayus-safetyX-ray Inspection: More Than Just Contamination DetectionX-ray inspection can detect numerous quality shortfalls that lie hidden within product packaging or deep within the product itself. This white paper explains that x-ray inspection is no longer just a technique for catching contaminants; its become a wide-ranging tool for defending brand values and keeping customers happy.Register today for your Free copy:/xrayus-integrity。
