the untreatedreference sample. Steam injection, steaminfusion,ohmicand
microwave heating all have the potential of reducing the heating time
dramatically.Someold approaches to the inactivation of microorganisms,such
as high-pressure(inventedin the late nineteenth century)and pulsed electric
fieldtreatment(invented in the 1960s)havebeenreassessedand, withimproved
technology,havereached or almostreached commercialapplication.
Thesedevelopmentshavepartlybecomecommerciallypossible thanks to the
improvements in the hygienic design and operation of food factories.
Improvements in hygienehavereduced the microbialburden in bothplant
and raw materials, allowingproduction run timeslongenoughand cleantimes
shortenoughto make production economicallyfeasible.In the past few years,
the movement has beentoward foodsafetyobjectives, wherea certainminimal
reductionin microbial loadis no longer the objective of a treatment (for
example, for thermal sterilisationa 12 log reduction in bacterialspores), but the
final concentrationof microorganismsin the product.If a product has a low
microbial burden, the treatment required can be much milderto render the
product safe. Hygienic design and operation thereby become crucial: if
insufficient, the concentrationof microorganismsin the product will increase
during processingor becomecontaminatedor, afterprocessing,recontaminated.
Improvinghygienemoreover decreasescleaning timeand increases production
run time,improving economy.
122 Part II