dissolve into the cleaningsolution. Acidcleaners are especially effectivein
removing milk stone,mineral deposits, and waterstainscausedby hardwater.
Unfortunatelymany acid-based detergentsare corrosive to metals, particularly
galvanized iron and stainlesssteel. HCl,in particular, is especially corrosiveto
stainlesssteel.The strongacidsare considerably more corrosive than theirweak
counterparts. For this reason,strongacidsare usedsparinglyand mostoftenonly
in specialcases.
Alkalinecleanerscombinewithfat to formsoapand withproteins to form
solublecompoundsthat are easilyremovedby water. Alkalis are the principal
constituent of mostcleaning formulations.The activealkalinity of a chemical is
the measure of its value as a detergent.Alkaline solutionswitha pH of less than
8.3 havelittleor no cleaning effect (Elliot, 1980;Katsuyama, 1980 ). Alkaline
cleaners are of three types:strongalkalis;mildalkalis;and soaps.
Sodiumhydroxide(NaOH),also calledlye and causticsoda,is the strongest
of the strongalkalinecleaners.It has excellentdetergency.Sodiumhydroxide
is alsohighlycorrosiveto aluminum,galvanizedmetal,and tin. It has poor
rinsing and wetting characteristic in the absence of functional additives.
Sodiumhydroxide,like otherstrong alkalis,causesprecipitatesto formin hard
water.
Mildalkalishave greaterdissolvingpower and are far less corrosivethan
strongalkalis.As mentionedpreviously, alkalis are the majoractiveingredient
of many industrial cleaning compounds.The bulkof theseare mildalkali.The
mild alkali sodium carbonate is a commonconstituent of many cleaning
compounds.
Soapsare cleaningagentsmadefromthe reactionof alkali and fats (sapon-
ification) or fattyacids.Soaps,in general, are not verysolublein coldwater.
Theyformprecipitates and difficult to removescumin hardwater. Moreover, in
solutionthey break downto fattyacidsand lose theirdetergency. Soapis seldom
usedin foodprocessing operations,except for hand-washing.
Otherimportant considerations
In the contextof defining the parameters of the washcyclethereare important
factors otherthanthosepreviouslydiscussedthat requireconsideration. These
factors includethe following: surfacefinishor surfacecharacteristics of the item
intended for cleaning; wash cycletemperatureand temperaturecontrol during
wash;exposuretimeor durationof the wash;and the appliedforceor the
amountof agitation required for cleaning.
Surfacefinish
The pointhas beenmadethat a number of the acidand alkalinecleaners are
highlycorrosive to a rangeof materials that are commonly usedas the materials
of constructionfor foodprocessing equipment.In addition to susceptibility to
corrosion, some surface finishes are vulnerable to film formation; bothmineral
and biological. Special consideration must be given to equipment that is
fabricatedfrom materials thatdo not havesmooth,polished or impervious
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