Lighting in meat processing areas May 1997 - Red Meat Innovation

Meat technology update97/3 – May 1997Reprinted November 2006Lighting in meat processing areasIncreasing emphasis on meat hygiene assessment, including zero faeces and ingesta,and on good processing procedures, means that an understanding of lighting isbecoming more important.The AQIS and Australian Standard regulations for construction give the minimumrequirements for the meat industry. For areas where better than the minimum lightingrequirement is desirable, a person suitably qualified in lighting should be consulted.Quality of lightAdequate quantity of light (or illuminance)is only one of the necessary elements ofa satisfactory lighting system, particularlyfor such tasks as inspection for meatclassification, prevention of defects,detection of contamination, disease,colour and the like. Failure to achieveadequate light quality can reduce theefficiency of assessment and thereby,enhance the possibility of complaint.Poor quality lighting, even though there isenough of it, can also cause visualdiscomfort to meat processing operators.Australian Standard® “Interior Lighting”AS.1680.1 - 1990 and AS.1680.2 - 1990will reveal what the important qualityrequirements are. If a new plant is beingplanned, an existing one is beingextended, or lighting installation is beingrenewed, reference should be made tothe Standard.Another important aspect is the vision ofemployees carrying out the tasks that arevisually important. Good lighting will notnecessarily compensate for deficientvision.Direct glareDirect glare occurs when there is anover-bright source of light directly in thefield of view. Factors that determine itsseverity are its inherent degree ofbrightness, its apparent area or size tothe eye, its angular displacement fromthe general direction for the task, and therelative brightness of the backgroundimmediately surrounding it. An overbrightlamp in a meatworks should not beclose to the line of sight. If it is, stepsshould be taken to shade it or otherwiselimit the glare effect as the Standardadvises.The Australian Standard gives guidanceon the assessment of whether aparticular luminaire (the internationalterm for light fitting), by rating and type, istoo bright, and gives appropriatemethods of controlling its brightness.These include the provision of luminance(brightness measured by instrument)limits on the luminaire and suitableshielding angles for shades and louvres.Unfortunately, the Australian Standard1680 - 1990 has proven much harder toapply to the letter of the law thanoriginally intended and some dischargeluminaires with metal halide, mercury

vapour and high pressure sodium lamps, i.e.light sources of sufficient power toeconomically illuminate large processingareas, may have difficulty meeting glare testcriteria.Reflected glareIn a survey, luminaires were seen inpositions where possible troublesomereflections were directed to operators’ eyesfrom wet surfaces of offal on the visceraconveyor, from polished stainless steelworking surfaces, or from glossy wall tilesand even water laying on the floor. TheStandard gives guidance on the ways ofeliminating or minimising such effects. Inmany cases the solution is once again apractical one such as use of a matt surfaceinstead of a highly polished or glossy one or,minor relocation of luminaires, addition of adiffusing refractor or visor, or simply, use ofcoated or diffuse lamps.Brightness distributionBrightness distribution (the pattern ofbrightness that appears in the field of vision)is an important factor for visual efficiencywhen undertaking demanding tasks inlocations such as the boning room and theslaughter line.It is important that the brightness of theobject examined (the luminance) is greaterthan the remainder of the field of view. Thebackground should present a comfortablebrightness distribution. However, if thedifference in luminance between the objectexamined and the immediate background istoo great (i.e. greater than about four to one),the worker could have problems of adjustingback and forth between the two light levels,thus affecting visual performance.Uniformity of illuminationUniformity refers to the variation inilluminance (level read directly by a lightmeter in lux) which appears over worksurfaces, and the total work space, e.g. the‘pooling’ pattern created by the spacing oflight fittings. Again, this can contribute toeye strain. Closer spacing of luminaires canimprove uniformity. Luminairemanufacturers provide guidelines for spacingto mounting height ratios.For example, as well as the concentrateddirectional light on the slicing and inspectionoperations of the boning room, it is importantto have an adequate level of generalillumination (illuminance), making ceilingsand walls comfortably bright for those whoglance up from task areas of high brightness.ColourThe employees’ reactions to theirsurroundings - how they feel when working inan area - can be very important inmaintaining productivity. Colour, as alreadyindicated, plays an important part in creatinga good working environment and incontributing to the quality of the lighting.Apart from the finish on work surfaces,ceiling and walls, the correct choice of lampscan contribute in this regard.Consideration of two light sourcecharacteristics - colour temperature andcolour rendering - will provide someassistance in the achievement of optimuminterior colour appearance of objects andsurfaces. They are important criteria in theselection of the most appropriate source forthe particular visual requirements of the task.Colour temperatureColour temperature is a figure that givesa measure of the colour appearance ofthe light from the lamp itself.The colour appearance of near white lightsources is normally expressed in DegreesKelvin (K). The higher the figure, the coolerthe appearance of the source; the reddishyellowflame of a candle is about 1900K, theordinary incandescent lamp, about 2800K,and cold bluish-white southern sky daylight,over 6500K. Thus the colour of lightchanges from having mainly red/yellowcomponents at about 2500K to light havingmainly blue components at about 6500K,which approximates natural daylight with ablue sky.2

Lamps with colour temperatures in the range3500K to 5000K are generally preferred forcommercial and industrial applications, thehigher colour temperature lamps being usedwhere a lively/cool environment is required.Colour temperatures in the region of 4300Kare most suitable for tasks in abattoirs,especially where visual efficiency is critical,e.g. inspection. These lamps may be called‘white’ or ‘cool white’. Higher colourtemperatures may be called ‘daylight’. Thecolour temperature of ‘warm white’ lamps(below 3500K) is generally considered to besuited to comfortable/warm environments(residences) and does not suit the criticalvisual tasks in processing areas.Colour temperature does not affectillumination. However, many people willperceive an identical illumination level undera low colour temperature lamp, e.g. highpressure sodium, as being much lower thanthat provided by the high colour temperaturelamp, e.g. metal halide. Also, in a warmclimate, a low colour temperature lamp cancreate a feeling of warmth. At inspectionpoints a colour temperature of 4000K-5000Kis recommended, provided that the lamp hassuitable colour rendering properties.Colour RenderingColour rendering is the ability of a lightsource to reproduce colours of objectsaccurately, e.g. the meat and fat colour, orcontaminants on a carcase. To determinethe colour rendering index (CRI), a series oftests is conducted with the light source inquestion compared with reference sources oflight with known or calibrated colourrendering properties. This is determinedover a set of eight standard colours. TheCRI is, in fact, an average colour rendering.Lamps with identical CRI values of 85 fromtwo different manufacturers may, in fact,have widely differing spectral distributions inspite of the common CRI value of 85, i.e. onemake might have a high CRI in the red bandand a low CRI in the blue band, and theother make vice versa.Field tests are necessary to determine if thelamps are suitable for specific tasks. Aweakness in one lamp in a particular colourband may be a strength in the other lamp.We must remember that an average is a‘mean’ and very high results in, for example,six out of the eight tests may give the lamp avery high CRI and yet the colour band mostimportant to your visual task may fall into thepoor area of colour rendition.Lamps which are highly efficient for colourrendering (say, CRI equal to or greater than90), by comparison, often have lowerefficacy, i.e. are lower in lumen or lightoutput. As an example, a typical coatedmetal halide lamp with a CRI of 65 has anoutput of 38,000 lumens; a lamp with a CRIof 80 produced by the same manufacturerhas an output of 24,500 lumens.That is to say, a lamp that is necessary toensure that defects and diseases aredetected as a result of faithful colourrendering of these elements to the inspectorwill be more costly to purchase and runbecause for a given light output (lumens) itconsumes more power.General production areas could beilluminated by lamps with a reasonablecolour rendition ability and with high lumenoutput (efficacy), whereas areas with verystringent inspection needs could be locallyilluminated by lamps with a very high CRI orcolour rendering ability. This is much easierif the colour-sensitive tasks are isolated inseparate rooms or sections of the building.Quantity of light (illuminance)This Update has made reference toluminance (brightness measured with aninstrument). Unfortunately, luminancecannot be measured with a normal lightmeter as the latter measures the amount oflight falling on a surface (illuminancemeasured as lux). A luminance metermeasures the brightness of an object as itappears in the field of view (reflected light).It is similar to a photographic exposurephotometer used to measure reflected light;however, the luminance meter is calibratedin candelas per square metre. Theluminance meter would measure ‘brightnessdistribution’ or difference.3

The accurate field measurement ofthe luminance of existing luminaires orinterior surfaces is generally notpractical. It requires a very expensivelaboratory-type instrument. It is farmore appropriate to do this workbefore the installation is complete.It is important to remember thatilluminance readings, taken with alight meter, should be taken in theplane (horizontal, vertical or inclined)of the object being examined, asviewed by the operator and as closeto the object as practicable. Hence, alight meter reading on a meat carcasehanging on the slaughter line shouldbe taken with the meter lying in thevertical plane of the carcase, becauseit is the illuminance on the verticalsides of meat as seen by theoperators that determines visibility.representative average illuminancevalue, and allow assessment of theuniformity.MaintenanceMaintenance of lighting systemskeeps the performance of the systemwithin the design limits, promotessafety, and, if considered at thedesign stage, can help to minimise theelectrical load and capital costs.Lighting systems deteriorate withoutregular maintenance. The output ofthe lamp decreases as the length oftime it has been in operationincreases. Different lamp typesdeteriorate at different rates.Further, dirt deposition will occur onlamps, luminaires and other surfaces.Unfortunately, most of the meatindustry regulations refer toilluminance values (lux) on a planeone metre above the floor or on animaginary horizontal work plane,which is often not where the operatoris viewing the task. Using computertechnology, the lighting engineer cancomply with this requirement, yet doadditional vertical or slope planeilluminance calculation checks todetermine if the illuminance in theseplanes is of sufficient quantity anduniformity.A sufficient number of illuminancemeasurements should be made overthe task area to provide aContact us for additional informationMeat Industry Services is supported by the Australian Meat Processor Corporation (AMPC) and Meat & Livestock Australia (MLA).Brisbane: Sydney: Adelaide:Food Science Australia Bill Spooncer Chris SentancePO Box 3312 PO Box 181 PO Box 178Tingalpa DC QLD 4173 KURMOND NSW 2757 FLAGSTAFF HILL SA 5159Ian Eustace Neil McPhail Alison SmallT +61 7 3214 2117 T +61 7 3214 211 T +61 7 3214 2109 T +61 2 4567 7952 T +61 8 370 7466F +61 7 3214 2103 F +61 7 3214 2103 F +61 7 3214 2103 F +61 2 4567 8952 F +61 8 8370 7566M 0414 336 724 M 0414 336 907 M 0409 819 998 M 0414 648 387 M 0419 944 022