crucialfor determininghowit can best be removed.Moreover, understanding
soil typeis a requirement for properly specifying the quantity of soil that must
be removedin orderto achieve the cleaningobjectives.For example, if the soil
type underconsiderationis known to be a goodmicrobiologicalgrowth medium,
thenit wouldbe prudent, at this step, to reduce its residuals to the absolute
minimum.
Rinsewatertemperatureand pressureare alsoimportantto achievingsoil
removal. The physicaland chemical natureof the targetedresidues will dictate
the force(waterpressureor agitation) and temperature of the rinse waterstream.
Excessivelyhot or coldwater,depending on soil type,maygiverise to film
formation or other conditionsthat maycomplicatethe cleaningprocess. Force
and temperature requirementsfor removing emulsifiedfats and oils will differ
radically fromthose required to removediscretepiecesof vegetablematter.
Moreover, whendefining the pre-rinseparametersit is importantto specify,
qualitatively,the amount of residual matterthat may remain attached to the food
contactsurface.For example, the specification might simplyread`no visible
residual matter'. An effectivepre-rinseis critical to achieving the specified
cleaning objective. Failure to deliveran effective pre-rinse may limit or
compromise the performance of the entireCOPprocess.
28.4.2 Washing
Washing is the systematic detergent-aided scouring, scrubbing, or other
procedures that are intendedto render the elementof foodprocessingequipment
free from offensive odors, residual food and other extraneous materials.
Arguably, washing is the most important step of a COPwet-cleaningprocess. It
is also the most complex.Its complexityarises fromthe numberof critical-to-
cleaning factors that are associatedwiththis step in the process.The critical-to-
cleaning factorsincludethe following:soil type;waterchemistry;detergent type
and concentration;surface finish; temperature; agitation; and exposure time.
Soil type
The issue of soil typewas introduced and discussedbrieflyin the preceding
section. Becauseof its importanceto the overallprocess,a morerobustand in-
depthdiscussion of the subject is providedhere.Foodsoilsvaryconsiderablyin
theircompositionand complexity.They are the unwanted residues of food
processing that adhereto the surfacesof the processingmachinery, its appur-
tenances and the other implements of production. Soil may be visibleor
invisible. Theresidues maybe moist and malleable or dry and brittle.The
residues mayexistas discrete particles or as a fine film withimbeddedbacteria.
For purposes of discussionit is convenient to assignfoodsoils,broadly, to one
of fourcategories: fat-based;carbohydrate-based; protein-based;and mineral-
based.
Fat-based residues are usually presentin food processingoperationsas
emulsions. Edibleoils,lard,and other hydrogenatednut and vegetableoils are
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