Ideal technology for high-pressure homogenization

Short-term ther­mal treat­ment is used in the food indus­try for a wide range of prod­ucts such as milk, mixed drinks or liq­uid foods. This treat­ment kills off any path­o­gen­ic micro-organ­isms and extends the shelf life of the prod­ucts. Since high-pres­sure homog­e­niza­tion may not re-con­t­a­m­i­nate food prod­ucts after ther­mal treat­ment, it must be ensured that all com­po­nents being used have a hygien­ic or – even bet­ter – asep­tic design, mate­r­i­al selec­tion and inte­gra­tion. To date, packed plunger pumps have pri­mar­i­ly been relied upon as the type of pump tech­nol­o­gy installed in these appli­ca­tions. How­ev­er, in terms of asep­tic pro­duc­tion safe­ty, using these pumps is only the sec­ond-best choice. This is because, despite a design that accounts for plunger pack­ing com­po­nents with ster­ile bar­ri­ers and flush­ing sys­tems, there is a risk of recon­t­a­m­i­na­tion after in-process CIP/SIP clean­ing. Fur­ther­more, the ther­mal load cre­at­ed here results in increased wear on the plunger and its seal­ing sys­tem. The con­se­quence is a sig­nif­i­cant­ly reduced ser­vice life, espe­cial­ly when the food prod­uct being treat­ed con­tains abra­sive ingre­di­ents. One alter­na­tive is to use process diaphragm pumps. They fea­ture a her­met­i­cal­ly tight liq­uid end, which is her­met­i­cal­ly sep­a­rat­ed from the hydraulic cham­ber and process envi­ron­ment by a diaphragm. This pre­vents the inside of the flu­id cham­ber from becom­ing con­t­a­m­i­nat­ed, rul­ing out any con­t­a­m­i­na­tion of the process space—including the food product.

Lis­te­ria in cheese, E. Coli bac­te­ria in meat and sal­mo­nel­la in baby formula—food scan­dals and recall cam­paigns by major man­u­fac­tur­ers have become all too fre­quent in recent times, dam­ag­ing the rep­u­ta­tions of the man­u­fac­tur­ers respon­si­ble. This phe­nom­e­non has been increas­ing cus­tomer aware­ness and putting more pres­sure on the indus­try. Espe­cial­ly for sen­si­tive prod­ucts and prod­ucts with high hygien­ic stan­dards, it is absolute­ly imper­a­tive to ensure hygien­ic pro­duc­tion through flaw­less hygien­ic process steps, as this guar­an­tees micro­bi­o­log­i­cal integri­ty. In doing so, the fol­low­ing points must be kept in mind: Safe and reli­able asep­tic man­u­fac­tur­ing process­es are nec­es­sary in achiev­ing high micro­bi­o­log­i­cal qual­i­ty and last­ing sta­bil­i­ty while still meet­ing the cus­tomers’ high expec­ta­tions for aspects such as high taste qual­i­ty , health­i­ness and sus­tain­abil­i­ty of the prod­uct. Short-term ther­mal treat­ment (UHT process­es) and con­sis­tent down­stream asep­tic tech­nol­o­gy present a pos­si­ble solu­tion to this prob­lem using reli­able food-pro­cess­ing technology.

New trends in the food and bev­er­age sec­tor such as unprocessed and inno­v­a­tive ready-to-eat prod­ucts pose cer­tain chal­lenges to the food indus­try sup­ply chain with regard to food safe­ty. This applies to both increas­ing expec­ta­tions for fresh­ness and the addi­tives and preser­v­a­tives put into food, which make it nec­es­sary to invest in dif­fer­ent tech­nolo­gies than those used in pre­vi­ous pro­duc­tion process­es. The pro­duc­tion chain is fur­ther affect­ed by crossover-prod­ucts between the food and phar­ma­ceu­ti­cal sec­tors such as ready-to-drink “nutri­tion­al bev­er­ages,” as they are called, which some­times con­tain high pro­por­tions of abra­sive solids (e.g. due to cal­ci­um and nuts) or ingre­di­ents with micro­bi­o­log­i­cal sen­si­tiv­i­ty. In pro­duc­ing such crossover prod­ucts, empir­i­cal knowl­edge from the phar­ma­ceu­ti­cal GMP envi­ron­ment is advan­ta­geous. Here, nutri­tion­al sup­ple­ments with func­tion­al milk pro­tein sources, fruits and fla­vors are com­bined to form new bev­er­ages, which may require spe­cial atten­tion dur­ing pro­duc­tion depend­ing on their acid­i­ty and pH val­ues. These high require­ments must be adhered to specif­i­cal­ly when for­mu­lat­ing baby foods and high-calo­rie clin­i­cal nutri­tion (liq­uid enteral/parenteral foods). Dur­ing pro­cess­ing, there are key tasks that must be han­dled by the pump tech­nol­o­gy specif­i­cal­ly, e.g. for feed­ing raw mate­ri­als and cre­at­ing for­mu­la­tions that match the recipe, includ­ing meter­ing and mix­ing ingre­di­ents at the cor­rect pro­por­tions. Since the end prod­ucts are ide­al­ly stored at room tem­per­a­ture and are sup­posed to last for an extend­ed time in shelf, short-term ther­mal treat­ment is rec­om­mend­ed here as well. It is the opti­mal tech­nol­o­gy for killing off for­eign germs at a high rate and should be fol­lowed by asep­tic high-pres­sure homog­e­niza­tion using diaphragm pump tech­nol­o­gy. This pre­vents re-con­t­a­m­i­na­tion and ensures gen­tle prod­uct treatment.

Freedom from residue and microbial safety in high-pressure homogenization

High-pres­sure homog­e­niza­tion is an appli­ca­tion field that pos­es par­tic­u­lar chal­lenges to pump tech­nol­o­gy. The sys­tems used in this field con­sist of a high-pres­sure pump used as a pres­sure gen­er­a­tor in addi­tion to a hydraulic con­sumer, which is called the homog­e­niza­tion valve. The pur­pose of the pump is to gen­er­ate the ener­gy for dis­per­sion in the valve, to con­vey the flu­id being dis­persed and to ensure the exact flow rate in the process.

Working principles of high-pressure pumps for homogenization applications

The rec­i­p­ro­cat­ing high-pres­sure pumps that the high-pres­sure homog­e­niza­tion machines are equipped with are nec­es­sary for pump­ing the flu­id from the suc­tion side through a feed pump (usu­al­ly a cen­trifu­gal pump) by increas­ing pres­sure on the homog­e­niza­tion unit (sin­gle-stage or two-stage valve). Homog­e­niz­er pumps are equipped with three to six pump heads. Process diaphragm pumps stand out for their robust mono-block design and because of the inte­grat­ed worm gear with high hydraulic out­put thanks to very smooth run­ning. Flu­id valves with appli­ca­tion-spe­cif­ic designs that have been opti­mized for wear and hygiene ensure reli­able pump­ing on both the intake and dis­charge sides of the pump. Auto­mat­ed homog­e­niza­tion valves are con­trolled pneu­mat­i­cal­ly and hydrauli­cal­ly. The droplet size dur­ing homog­e­niza­tion is deter­mined main­ly by the cav­i­ta­tion in the cham­ber of the sec­ond stage and is depen­dent on the pres­sure-drop there. Assum­ing incom­press­ible flu­ids are han­dled, the flow rate of a rec­i­p­ro­cat­ing diaphragm process pump is reduced by a small amount as pres­sure increas­es and can be treat­ed as a near­ly con­stant val­ue. Pres­sure fluc­tu­a­tions between a rec­i­p­ro­cat­ing pump and the homog­e­niz­er valve can be coun­tered using pul­sa­tion-smooth­ing mea­sures. This includes select­ing suit­able oper­at­ing points for the pump and damp­ing mea­sures on the pip­ing. Here, very spe­cif­ic dynam­ic sim­u­la­tion pro­grams car­ried out with­in the scope of a pul­sa­tion analy­sis can pro­vide sup­port in the design.

For homog­e­niza­tion tasks fol­low­ing UHT treat­ment, the homog­e­niza­tion pump and the homog­e­niza­tion valve must con­sis­tent­ly meet asep­tic require­ments so that the integri­ty of the prod­ucts being treat­ed remains ensured. How­ev­er, many pumps still in use today are packed plunger pumps. For this type of unit, note that plunger pack­ing com­po­nents with ster­ile bar­ri­ers and flush­ing sys­tems must be incor­po­rat­ed into the design as a mea­sure of pre­vent­ing recon­t­a­m­i­na­tion after in-process CIP/SIP clean­ing. More­over, con­t­a­m­i­na­tions caused by plunger abra­sion in the pack­ing area can­not be ruled out for this pump class. The prefer­able option for asep­tic process­es is thus to equip the homog­e­niza­tion steps with her­met­i­cal­ly tight process diaphragm pumps.

Diaphragm pump technology eliminates fluid contamination

The diaphragm pump can be viewed as a suc­cess­ful evo­lu­tion of the packed plunger pump. The diaphragm pump reach­es an effi­cien­cy of up to 95 per­cent (in ref­er­ence to what are called triplex diaphragm pumps, i.e. fea­tur­ing three pump heads). The pump is set apart thanks to its low amount of wear and thanks to flow rates that are near­ly inde­pen­dent of the dis­charge pres­sure. In homog­e­niza­tion appli­ca­tions, you ben­e­fit tremen­dous­ly from the fact that diaphragm pumps are designed to oper­ate with­out dynam­ic seal­ing sys­tems. This guar­an­tees a her­met­i­cal­ly tight pump head, mean­ing zero emis­sions or sub­strate leaks from inside the sys­tem as well as zero ingress of germs from the out­side. As a result, flu­id con­t­a­m­i­na­tion can be ruled out. This means that the diaphragm pump is the per­fect solu­tion for demand­ing appli­ca­tions. It is suit­able for media that, for instance, have to be pumped with zero leaks and absolute oper­at­ing reli­a­bil­i­ty because they are haz­ardous or abra­sive and must under no cir­cum­stances be released into the pro­duc­tion envi­ron­ment, or media such as baby for­mu­la that have to remain ster­ile and free of contamination.

A hygien­ic or asep­tic appli­ca­tion requires addi­tion­al spe­cial adjust­ments to the diaphragm pump head: A suit­able pump head mate­r­i­al such as stain­less steel 1.4404 or, as an alter­na­tive, par­tic­u­lar­ly cor­ro­sion-resis­tant austenitic mate­ri­als such as 1.4439 or 1.4462 (Duplex), pol­ished sur­faces with an RA val­ue < 0.8 µm and flu­id cham­bers with min­i­mal dead space and no gaps may make it pos­si­ble to car­ry out CIP/SIP clean­ing steps repeat­ed­ly and effi­cient­ly, thus ensur­ing ster­ile oper­a­tion with­out dis­man­tling. The design and instal­la­tion of the pump should, how­ev­er, allow for the clean­ing results to be checked peri­od­i­cal­ly while still min­i­miz­ing the ster­ile inter­faces in the pipe rout­ing. Direc­tives such as those of the Euro­pean Hygien­ic Engi­neer­ing Design Group (EHEDG) – specif­i­cal­ly Doc­u­ment 17 (“Hygien­ic Design of Pumps, Homog­e­niz­ers and Damp­en­ing Devices”) – or the 3‑A San­i­tary Stan­dards 44–03 (“San­i­tary Stan­dards for Diaphragm Pumps”) and 04–05 (“San­i­tary Stan­dards for Homog­e­niz­ers and Rec­i­p­ro­cat­ing Pumps”) pro­vide infor­ma­tion on how pumps for the food indus­try are to be designed and installed. Hygien­ic design aspects regard­ing clean­ing and drain­abil­i­ty of the pumps, valves and pip­ing of ster­ile sys­tems for the design of asep­tic process con­nec­tions of diaphragm pumps can also be found in the ASME BPE Stan­dard in the ver­sion that is valid for the spe­cif­ic application.