The estimated possibilities of process monitoring in milk production by the simple thermodynamic sensors

Po a ina s o® Scien i ic Jou nal o Food Indus y Volume 10 643 No. 1/2016 INTRODUCTION The p inciple o he modynamic senso The cha ac e iza ion and moni o ing o he mal p ocesses in a ious he modynamic sys ems can be pe o med using he he modynamic senso s (TDS) ha a e based on he p inciple o balance equilib ium. These senso sys ems a e one o he newe g oup o senso s o sensing he he mal quan i ies. The basic idea, basic model and heo y o ideal he modynamic senso in eg a ion as an ideal elemen in la ge models o he modynamic sys em we e p esen ed in pa en (Indus ial P ope y O ice o he Czech Republic, 2006). The o iginal heo y o ideal he modynamic senso as a p ocess and media ene gy ac i i y moni o ing de ice was p esen ed in Reznicek e al., 2005, Reznicek e al., 2006, Reznicek e al., 2008 and Reznicek, 2014. The p inciple o hese he modynamic senso s is based on measu emen o ene gy, which is supplied o ci cui o empe a u e se ing and equilib a ion o empe a u e elemen wi h ambien . The senso elemen is e y o en in eg a ed wi h an ampli ie and a con e e o de ined elec ical signal (U, I, ), which is e y easily connec ed o o he measu ing sys ems. Th ee g oups o in luences ha e e ec on he modynamic senso s (Figu e 1). Fi s g oup o in luences is p esen ed by in luences I1. This g oup ha e e ec only on a empe a u e o sensi i e elemen T2. Va ious physical quan i ies ( empe a u e, adian hea , humidi y, low o liquid), which a e possibly ans o med o empe a u e ene gy, a e heo e ically measu ed in his g oup. Second g oup o in luences is p esen ed by in luences I2. This g oup change he empe a u e p ope ies be ween he sensi i e elemen s T1 and T2 (di e ence ene gy E1 and E2). Volume, densi y, low o liquid, p essu e and many o he quan i ies can be heo e ically measu ed measu e in his g oup. Las g oup o in luences is p esen ed by in luences I3, which ha e e ec on a empe a u e o bo h sense elemen s T1 and T2. I bo h sense elemen s ha e he same sensi i i y, his g oup does no ha e e ec on ou pu o ol age signal o he modynamic senso . Ad an ages and disad an ages o TDS A common ea u e o he modynamic measu emen sys em is he moni o ing o majo e en s. Howe e , echnological windows o p oduc ion p ocesses a e dec easing due o inc easing he demands on he eliabili y and quali y o he a ge p oduc . Acco dingly, he demands on he con olling and moni o ing inc ease up o he possibili y limi when using cu en echnologies. Po a ina s o, ol. 10, 2016, no. 1, p. 643-648 doi:10.5219/462 Recei ed: 10 Ma ch 2015. Accep ed: 14 Decembe 2016. A ailable online: 19 Decembe 2016 a www.po a ina s o.com © 2016 Po a ina s o. License: CC BY 3.0 ISSN 1337-0960 (online) THE ESTIMATED POSSIBILITIES OF PROCESS MONITORING IN MILK PRODUCTION BY THE SIMPLE THERMODYNAMIC SENSORS Ma in Adámek, Anna Adámko á, Michal Řezníček, Lenka Kouřimská ABSTRACT The cha ac e iza ion and moni o ing o he mal p ocesses in he modynamic sys ems can be pe o med using he he modynamic senso s (TDS). The basic idea o he modynamic senso is possible o use in many a ious applica ions (eq. moni o ing o ic ional hea , he mal adia ion, pollu ion o cleaning luid, e c.). One o applica ion a eas, whe e he he modynamic senso can ind he new a ea o a using, is a p oduc ion o milk p oduc s - cheese, yogu , ke i , e c. This pape desc ibes he es ima ed possibili ies, ad an ages and disad an ages o he use o he modynamic senso s in dia y p oduc ions and simple expe imen s o cha ac e iza ion and moni o ing o basic ope a ions in milk p oduc ion p ocess by he modynamic senso s. The milk p oduc s a e o en ealized by e men ing o enne ing p ocess. Final s ages o e men a ion and enne ing p ocesses a e o en de e mined on he base o senso y e alua ion, pH measu emen o by analy ical me hod. The exac ime o he e men a ion p ocess comple ion is dependen on a ious pa ame e s and is o en he company know- how. The as , clean and simple non-analy ical non-con ac me hod o moni o ing and o he de e mina ion o p ocess inal s ages does no exis in his ime. Tes s o e men a ion p ocess, enne ing p ocess and yoghu p ocess by he modynamic senso s we e cha ac e ized and measu ed in his wo k. Measu emen o ac i i y yeas s was es ed in i s se ies o expe imen s. In second se ies o expe imen s, measu emen o p ocesses in milk p oduc ion was es ed. Fi s esul s o simple expe imen s show ha he he modynamic senso s migh be used o de e mina ion o ime beha iou o hese p ocesses. The e o e, he milk p oduc s (cheese, yogu , ke i , e c.) is opened as a one o new applica ion a eas, whe e he he modynamic senso can be used. Keywo ds: he modynamic senso ; e men a ion p ocess; yeas Po a ina s o® Scien i ic Jou nal o Food Indus y Volume 10 644 No. 1/2016 The e o e, he need o moni o ing in a ea o ze o empe a u e di e ences and iden i ica ion o mino e en s (eg. an unexpec ed o unwan ed e en wi h a small empe a u e di e ence) by measu emen sys em inc eases (Reznicek, 2014). The using o he modynamic senso s ha a e based on he p inciple o balance equilib ium is one o he ways o moni o ing hese e en s on he backg ound o majo e en s (eg. empe a u e s abiliza ion). The e o e, ad an ages o TDS a e: High speed and high sensi i i y o e o he empe a u e senso s' ypes, o example he mocouples. Possibili y o hea low measu ing. Di ec ionali y o measu emen s. Possibili y o p ocess moni o ing in ze o empe a u e di e ence Possibili y o moni o ing and iden i ica ion o mino e en s. Possibili y o easy connec o he con ol and egula ion ci cui s. Howe e , TDS also has hese disad an ages: The sys em only gi es in o ma ion abou he ela i e empe a u e changes. The measu emen is highly dependen on he cons uc ion o he measu ing sys em in a speci ic applica ion. The e o e, he basic idea o he modynamic senso is possible o use in a ious applica ions - moni o ing o he b eakage o glass ibe s du ing hei p oduc ion, moni o ing o ic ional hea in engine, moni o ing ecep ion signal a he an enna, empe a u e s abiliza ion o he de ec o nanopa icles, e c. (Reznicek, 2014). The es ima ed possibili ies o p ocess moni o ing in ood p oduc ion by he simple TDS Many he mal p ocesses exis in ood p oduc ion – cooking, ying, baking, cooling, eezing, s e iliza ion, pas eu iza ion, d ying, e c. The TDS can be used o moni o a ious pa ame e s in many o hese p ocesses, which mus be e y o en con olled and eco ded o HACCP and cus ome s’ ce i ica ion. I is assumed eg. he possibili y o moni o he pu i y o he oil which is used in ying o moni o ing he pu i y o cleaning emulsion simila ly as was es ed in p ojec TAČR GAMA – TA01011754 “New me hods o he cleaning o assembled subs a es wi h highe e ec i i y and lowe ecological and ene gy comsump ion impac ”. Because he he modynamic senso is e y sensi i e and as , i is possible o measu e e y small empe a u e changes ha may be p oduced o example by g oups o yeas . The e o e, i is possible use TDS in he p oduc ion: dai y p oduc s – e men a ion p ocesses, yogu p ocesses, enne ing p ocesses, b ewe ies – e men a ion p ocesses, dis ille ies – e men a ion p ocesses, con ol unwan ed de elopmen o yeas and o he mic o lo a (s e iliza ion, canning), bake ies –con ols i abili y yeas , pickled cabbage – e men a ion p ocesses, e c. A p oduc ion o dai y p oduc s (cheeses, yogu s, ke i s, e c.) can be one o new applica ion a eas, whe e he he modynamic senso s can be used. Milk and p oduc s om milk a e one o impo an ing edien s o ood in people´s li es, especially o child en. Milk and dai y p oduc s a e sou ces o i amins, p o eins, a , mine als, lac ose, e c., which a e no ungible in people´s sus enance. The dai y p oduc ion is composed o complica ed and sophis ica ed p ocesses (Semjan, 1994). These p ocesses a e exac ing o p ecision, empe a u e s abili y and hygiene. This is a eason o close quali y checking. In he dai y p oduc ions, he he modynamic senso s can con inuously moni o , con ol and egula e he main p ocess pa ame e s – equi ed empe a u es and de ia ions om i (s e iliza ion and pas eu iza ion empe a u e o milk, dai y p oduc s, s o age empe a u e e c.). Howe e , he senso s can also moni o o he p oduc ion pa ame e s, which can be con e ed o a change o empe a u e low – pu i y and quan i y o basic aw ma e ials (milk, ma malade, ...), pu i y and he amoun o auxilia y media ( insing wa e , auxilia y gas, e c.), moni o ing and con ol unwan ed o unwan ed Figu e 1 The g oup o in luences I1, I2 and I3, which ha e e ec on he modynamic senso . Po a ina s o® Scien i ic Jou nal o Food Indus y Volume 10 645 No. 1/2016 e en – sani izing inspec ion o manu ac u ing de ices and space, wea down con ol o p oduc ion machines e c. The p oduc ion o dai y p oduc s is o en ealized by e men ing o enne ing p ocesses. The simple clean non-con ac ion non-analy ical me hod o de e mina ion o inal p ocess does no exis in his ime. Final s ages o e men ing o enne ing p ocesses a e o en de e mined on he base o senso y e alua ion o analy ical measu emen s. The di e en ways o sol ing hese p oblems a e looking o now. One o he possible ways o solu ion o his p oblem can be cha ac e isa ion and measu emen o hese p ocesses by he modynamic senso s. MATERIAL AND METHODOLOGY Chemicals Measu emen o ac i i y yeas s was es ed in i s se ies o expe imen s. D ied yeas “Ins an ní D oždí”, S. I. Lesa e, cas e suga “Cuk bílý k ys al”, Cuk o a y a liho a y TTD, a.s., Dob o ice, and dis illed wa e we e used as he ma e ial o i s measu emen . The basic ma e ial used o second measu emen s o milk p oduc s was aw milk om a m Fa ma Hole s. .o., Velké Přílepy. The yoghu “Whi e coun y yoghu wi h p obio ic BiFi cul u e”, Hollandia Ka lo y Va y a.s., Toužim, was used as s a cul u e o p oduc ion o yoghu and he enne p oces was made by he enee Lak ochym (1 : 5.000), MILCOM, a.s., P aha. Expe imen All he measu emen s we e done by using he TDS senso s, which was ab ica ed in HIT, s. .o., Nedachlebice. The senso s, a simple measu ing ci cui , powe sou ce and mul ime e Me ex 3270 D o Almemo 2390-5 (Ahlbo n Mess- und Regelungs echnik GmbH, Ge many) as ol me e , which was con olled by compu e , we e main pa s o wo kplace. The wo kplace o expe imen s wi h he modynamic senso s is shown on Figu e 2. Tempe a u e was 25 °C in case o i s expe imen s wi h wa e and 35 °C in empe a u e-con olled box in case o second expe imen s wi h milk p oduc s. S a is ical analysis The da a we e analysed using so wa e Excel 2013 (Mic oso Co po a ion, USA) and he esul s we e exp essed by g aph. Each expe imen was measu ed a leas h ee imes and he esul ing cu e was calcula ed as he mean alue o hese measu emen s. RESULTS AND DISCUSSION Measu emen o ac i i y o yeas s was es ed in i s se ies o expe imen s. Expe imen s we e made wi h wa e in oom empe a u e (25 °C). Volume o wa e was 25 mL. Fi s expe imen (Figu e 3) was ocused on e men ing p ocess, whe e he yeas s weigh was changed. The es weigh was 0.1 g, 0.5 g, 1 g and 1.25 g. Weigh o suga was 1 g. Resul s show a dependence o yeas s ac i i y on yeas s weigh in i s e men a ion phase and s abiliza ion o yeas s ac i i y on cons an alue in second phase o p ocess. The ini ial weigh o he yeas a ec s he inc ease a e o he o al yeas 's ac i i y. I is assumed ha inc ease o he yeas s numbe a ec s hea low be ween elemen s T1 and T2 (in luence I2). Nex , inc ease o he numbe o ac i e yeas s inc eases a hea , whi ch coming o he elemen T2 ( he e ec I1). A e eaching a maximum, he numbe o ac i e yeas s dec eases, he e o e he hea coming o he elemen T2 is also educed. The weigh o suga was changed (0.5 g; 1 g; 1.25 g) in nex expe imen (Figu e 4). Weigh o yeas s was 0.3 g. The yeas s ac i i y is inc eased wi h weigh o suga in i s e men a ion phase and is s abilized on cons an alue in second phase o p ocess again. Viable yeas can be used as an inoculum o many e men a ions p ocesses in he ood indus ies. The e men a ion p ocess inc eases he o al alue o he e men ed oods, eq. imp o ing he quan i y and quali y o p o eins and hei accessibili y, inc ease he diges ibili y o s a ch, inc easing he con en o i amins, especially g oup B ( ibo la in, hiamine, niacin, olic acid), inc ease he a ailabili y o mine al elemen s, e c. (A o a, Jood and Khe a paul, 2010; Cha alampopoulos e al., 2002; Ri e a-Espinoza and Galla do-Na a o, 2010; Kocko á and Valík, 2011). T adi ionally, yeas iabili y has been measu ed in colony- o ming uni s a e pla ing o cells on g ow h medium o by di ec mic oscopic coun ing using dye exclusion me hods (Jones, 1987a, b; Fung, 1994; Lloyd and Hayes, 1995; Haugland, 1996). Nex measu emen o yeas iabili y can be made a low cy ome y (Dee e e al., 1998; A ield e al., 2000) o moni o ing CO2 as p oduc o yeas ac i i y. Fo yeas iden i ica ion, PCR-RAPD and RFLP-PCR me hods (D ozdz e al., 2015) can be used. These me hods can be used o de e mina ion o yeas g ow cu e. The g ow cu e o yeas (Halasz and Lasz i y, 1990; Walke , 1998; Neal, 2004) and measu ed cu es o e men ing p ocess o yeas s in wa e wi h a change o yeas s weigh ha e a e y simila cha ac e . In acco dance wi h he weigh o he inoculum, he measu ed ol age measu ed ol age is inc eased and s abilized a e some ime. Simila ly, he cha ac e o he measu ed cu es o e men ing p ocess o yeas s in wa e wi h a change o suga weigh is also in acco dance wi h he p esen cha ac e o g ow h cu es. In second se ies o expe imen s, measu emen o p ocesses in milk p oduc ion was es ed. Expe imen s we e made wi h aw milk in empe a u e-con olled box (35 °C). Figu e 5 shows a cha ac e isa ion o yogu p ocess. S a and inal s age o his p oces is demons a ed. In he yogu p oduc ion, a mixed base s a e yoghu cul u e wi h he bac e ial s ain Lac obacillus delb ueckii subsp. bulga icus and S ep ococcus sali a ius subsp. he mophilus added o he milk. Bo h li ing o ganisms mus be in a p oduc in he op imal a io. L. delb ueckii ssp. bulga icus pa ially deg ades he casein. This eleases aline, his idine, me hionine, glu amic acid and leucine, which a e s imula ing he g ow h o S ep ococcus sali a ius subsp. he mophilus. S ep ococci o ms lac ic acid and c ea es a o able condi ions o he g ow h o lac obacilli (Cou in and Rul, 2004; Wals a, Wou e s and Geu s, 2006). I is possible o ind a hin o wo peaks on he cu e o yogu p ocess on Figu e 5. These peaks can be assigned ac i i y lac ococci and s ep ococci in he s a e cul u e. End o measu emen can also be in luenced by a change he iscosi y in he inal s age o he p ocess. The example o enne p ocess measu emen is shown on Figu e 6. Po a ina s o® Scien i ic Jou nal o Food Indus y Volume 10 646 No. 1/2016 Figu e 2 The wo kplace o expe imen s. Figu e 3 The e men ing p ocess o yeas s in wa e - a change o yeas s weigh . Figu e 4 The e men ing p ocess o yeas s in wa e . 9 10 11 12 13 0:00 0:28 0:57 1:26 1:55 Uou [V] T [hou ] 0.1 0.5 11.25 9 10 11 12 13 0:00 0:28 0:57 1:26 1:55 Uou [V] T [hou ] 0,1 0,25 0,5 1 Po a ina s o® Scien i ic Jou nal o Food Indus y Volume 10 647 No. 1/2016 The inal s age o his p oces is demons a ed again. The measu emen is in luenced by a change he iscosi y, which ha e impac o e mal p ope ies o yogu . A e adding enne ( e y o en wi h chymosin enzyme) o milk, he casein micelles s a o agg ega e and o ming a gel (Wals a, Wou e s and Geu s, 2006). Because his is a new a ea o applica ion o TDS and new me hod o measu emen , i can no ye compa e he esul s wi h o he au ho s. Resul s can only be es ima ed in compa ison wi h s anda d me hods, which a e less lexible and ime and ma e ial consuming. Al hough he numbe o measu emen epe i ion was low, he i s esul s show a possibili ies TDS in moni o ing o yeas ac i i y in e men a ion p ocesses and de e mina ion o inal s age in yogu and enne p ocesses. CONCLUSION The he modynamic senso was es ed in basic ope a ions in milk p oduc ion. Tes s o enne p ocess, yogu p ocess and e men a ion p ocess we e cha ac e ized and measu ed wi h he modynamic senso , which was bo owed om HIT, s. .o. Fi s esul s o simple expe imen s show ha he he modynamic senso s can be used o ime beha io and end de e mina ion o his p ocesses. REFERENCES A o a, S., Jood, S., Khe a paul, N. 2010. E ec o ge mina ion and p obio ic e men a ion on nu ien composi ion o ba ley based ood mix u es. Food Chemis y, ol. 119, no. 2, p. 779-784. h ps://doi.o g/10.1016/j. oodchem.2009.07.035 A ield, P. V., Kle sas, S., Veal, D. A., Van Rooijen, R., Bell, P. J. L. 2000. Use o low cy ome y o moni o cell damage Figu e 5 The yogu p ocess. Figu e 6 The enne p ocess. 3 4 5 6 0:00 2:24 4:48 7:12 9:36 Uou [V] T [hou ] End o p ocess S a o p ocess 7 11 15 19 23 0:28 0:43 0:57 1:12 1:26 1:40 Uou [V] T [hou ] End o p ocess S a o p ocess Po a ina s o® Scien i ic Jou nal o Food Indus y Volume 10 648 No. 1/2016 and p edic e men a ion ac i i y o d ied yeas s. Jou nal o Applied Mic obiology, ol. 89, no. 2, p. 207-214. h p://dx.doi.o g/10.1046/j.1365-2672.2000.01100.x Cha alampopoulos, D., Wang, R., Pandiella, S. S., Webb, C. 2002. Applica ion o ce eals and ce eal componen s in unc ional oods: a e iew. In e na ional Jou nal o Food Mic obiology, ol. 79, no. 1-2, p. 131-141. h ps://doi.o g/10.1016/S0168-1605(02)00187-3 Cou in, P., Rul, F. 2004. In e ac ions be ween mic oo ganisms in a simple ecosys em: yogu bac e ia as a s udy model. Le Lai , ol. 84, no. 1-2, p. 125-134. h p://dx.doi.o g/10.1051/lai :2003031 Dee e, D., Shen, J., Vesey, G., Bell, P., Bissinge , P., Veal, D. 1998. Flow cy ome y and cell so ing o yeas iabili y assessmen and selec ion. Yeas , ol. 14, p. 147-160. h ps://doi.o g/10.1002/(SICI)1097- 0061(19980130)14:2<147::AID-YEA207>3.0.CO;2-L D ozdz, I., Maka ewicz, M., S oka, P., Sa o a, P., Jankowski, P. 2015. Compa ison o he yeas mic obio a o di e en a ie ies o cool-clima e g apes by PCR-RAPD. Po a ina s o, ol. 9, no. 1, p. 293-298. h p://dx.doi.o g/10.5219/484 Fung, D. Y. C. 1994. Rapid me hods and au oma ion in ood mic obiology: a e iew. Food Re iews In e na ional. ol. 10, p. 357-375. h ps://doi.o g/10.1080/87559129409541006 Halasz, A., Lasz i y, R. 1990. Use o Yeas Biomass in Food P oduc ion. CRC P ess. 352 p. ISBN 9780849358661. Haugland, R. 1996. Handbook o Fluo escen P obes and Resea ch Chemicals. O egon, USA : Molecula P obes Inc. Indus ial P ope y O ice o he Czech Republic. Technique o e e en ial empe a u e and empe a u e di e ence measu emen , asyme ic empe a u e senso and asyme ic e e en ial uni o echnique applica ion. Pa en owne : Reznicek, Z. Czech Republic. Pa en no. CZ-297066. 2006-07- 19. Jones, R. P. 1987a. Measu es o cell dea h and deac i a ion and hei meaning: pa I. P ocess Biochemis y, ol. 22, p. 118-128. Jones, R. P. 1987b. Measu es o cell dea h and deac i a ion and hei meaning: pa II. P ocess Biochemis y, ol. 23, 130- 134. Kocko á, M., Valík, Ľ. 2011. Po en ial o ce eals and pseudoce eals o lac ic acid e men a ions. Po a ina s o, ol. 5, no. 2, p. 27-40. h ps://dx.doi.o g/10.5219/127 Lloyd, D., Hayes, A. J. 1995. Vigou , i ali y and iabili y o mic oo ganisms. FEMS Mic obiology Le e s, ol. 133, p. 1-7. h ps://doi.o g/10.1111/j.1574-6968.1995. b07852.x Neal, D. 2004. In oduc ion o Popula ion Biology. Camb idge, UK : Camb idge Uni e si y P ess. 394 p. ISBN 978-0521532235 Semjan, Š. 1994. Mlieká s o (Dai y echnology). Ni a, Slo ak Republic : SPU, 204 p. ISBN 80-7137-157-2. Reznicek, Z., T a ozek, Y., Reznicek, M., Szendiuch, I. 2005. Tempe a u e balanced p ocess media ene gy ac i i y moni o ing, In e na ional Con e ence EDS-IMAPS CS 2005 p oceeding. B no, Czech Republic. p. 94-100. ISBN 80-214- 2990-9. Reznicek, Z., T a ozek, Y., Reznicek, M., Szendiuch, I. 2006. Hyb id Cons an Tempe a u e Regula o . In e na ional Con e ence Eu oSimE I 2006 p oceeding, Como, I aly, p. 502- 505. ISBN 1-4244-0275-1. Reznicek, Z. S., Szendiuch, I., Reznicek, M., Reznicek Z. J . 2008. Thick Film Double The modynamic Senso Sys em. In 2nd Elec onics Sys em in eg a ion Technology Con e ence p oceedings. G eenwich, UK, 1-4 Sep embe 2008. p. 1301 - 1304. ISBN 978-1-4244-2813-7. h ps://doi.o g/10.1109/es c.2008.4684542 Reznicek, M. 2014. The modynamic senso s based on he p inciple o balance equilib ium: disse a ion heses. B no, Czech Republic : FEKT VUT B no, 93 p. Ri e a-Espinoza, Y., Galla do-Na a o, Y. 2010. Non-dai y p obio ic p oduc s. Food Mic obiology, ol. 27, no. 1, p. 1-11. h ps://doi.o g/10.1016/j. m.2008.06.008 PMid:19913684 Walke , G. M. 1998. Yeas Physiology and Bio echnology. Wiley. 362 p. ISBN 9780471964469. Wals a, P., Wou e s, J. T., Geu s, T. J. 2006. Dai y science and echnology. London, UK : CRC p ess, Taylo & F ancis G oup. 808 p. ISBN 978-0-8247-2763-5. Acknowledgmen s: The modynamic senso s ha we e bo owed om HIT, s. .o., we e used o he measu emen o expe imen s in he a ea o moni o ing ood p oduc ion ha a e p esen ed in his pape . This wo k was suppo ed by g an BD FEKT-S-14-2168. Con ac add ess: Ma in Adámek, B no Uni e si y o Technology, Facul y o Elec ical Enginee ing and Communica ion, Depa men o Mic oelec onics, Technická 3058/10, 616 00 B no, Czech Republic, E-mail: adamek@ eec. u b .cz. Anna Adámko á, Czech Uni e si y o Li e Sciences P ague, Facul y o Ag obiology, Food and Na u al Resou ces, Depa men o Quali y o Ag icul u al P oduc s, Kamýcká 129, 165 21 P ague 6 - Suchdol, Czech Republic, E-mail: ada[email p o ec ed]. Michal Řezníček, B no Uni e si y o Technology, Facul y o Elec ical Enginee ing and Communica ion, Depa men o Mic oelec onics, Technická 3058/10, 616 00 B no, Czech Republic, E-mail: eznicek@ eec. u b .cz. Lenka Kouřimská, Czech Uni e si y o Li e Sciences P ague, Facul y o Ag obiology, Food and Na u al Resou ces, Depa men o Quali y o Ag icul u al P oduc s, Depa men o Mic obiology, Nu i ion and Die e ics, Kamýcká 129, 165 21 P ague 6 - Suchdol, Czech Republic, E-mail: kou i[email p o ec ed].