The development of a chemical analogue of thermal destruction of bacterial spores : a thesis presented in partial fulfilment of the requirements for the Degree of Doctor of Philosophy at Massey University

Copyright is owned by the Author of the thesis. Permission is given for

a copy to be downloaded by an individual for the purpose of research and

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

'lhe Development of ^a Chemical Analogue of Thermal Destruction of Bacterial Spores

A 'lhesia Presented in Fartial I!'ulfilment

ot the Requirements for the Degree of Dootor of ibilosoph7

at 1fasse7 Uni ^{versi t7}

Gordon John _Ki toh Packer

1967

'·

MRSSEY UNIVERSITY

11111111111111111111111111111

1061258282

·.:

; :·

I ^•

.�

uHd : • • ·, to J : evalua^te the . ^total 'f." ^lethal.. . e^ffeot ^{of. heat on •} the b^aot^eri• al

.

^{F. ,pop,. , • • ·}

ulatioa in .a sealed

oon

^taine

.r

^of

�ood.

^{material. _The ohemi.oal}

r��·��

,

��que

^{has. &180}

�

^{led a atud,y to be made of}

tl;le,.,

^ef

�

^{eot .that,}

�

^··"'·�

.lll:OVement " '" • ·• • .or. the material. 1li • ^{thin th}; ^e container haiJ en. l( . the, ' ].etb8:J.1 ; o I • t;y . -.;.-� ^{. _} • .,

the .. applied heat. _·-�

. _,:..

the 4egree ot deatruootian ot baotarial spores is shown to depend

�

on the ^aoti_• v^{ation energies and.} deoimal reduotion times of ' "' . the :-·.:

ohemioal

"" t.'. · and bacterial qstema, and on the �heat penet�tion� J charaoter18t1Qa ot the material being prooeased •.

Aaid �· ot IIUO�, iD'buf't'ere4 solution, waa ohotlell u-:

the model obeld.o� ^reacti^on eyateu. · It -.. used in the exper1.melltal

:·at� ot no ^twe• of. ^prooeaa, a with cans .tatic:mary, ... in.��

oCU�Hroial batch retorta, m4 the other with the oana -rota'*l "•5P�wa4"

aa in _some c_ommercial agitating batoh retort a and oontim10WI

��� ..

� ^{etteat ot} convection oil the extent ^{of suoroee .bJ4r}ali'd^• bae

·been ime^ati^gated. By cambin1ng recorda of oan t•peratun · )11. th 4at& -.,,,:.

1:be

r

^{ate ot suoro• �·• the f'in.al} canosntraticm ot acl"O.,. hae' "� �· -

been oaloulatea. for a raage of proceaeea. 'fbeae caloulated�...:tuea·b&ve been oc:a.pared ^with tho^se actuall;y obtaine4 in the oan.

!heoretioal oonld.derationa ahc)y. th^{at the} etreat of ^ho^t

ili'\�al

. Ana ohelllioal ^' e1steu ^•• caioulated from . temperature a ^iAeaaUred at

'Pollti:-::

fiXe4 with re

sPec

^{t to the} OCI1taiMr, _i1 not Moessal'U7 the _{.... M}

�

aotual.l7 obtained ⁱⁿ the _container if OOilYMUGD: taa^a: p1aoe ^{· ·}c111Z'iag LtM 'f!'3r

· proo•••• ^· Simp^le oOUYeoticm. aoclela han-been _{ue4 to} relate th* utlllt ^.-,r ot!·IUOron �� o�oulatecl tram the te��paoat1ire 4&1:&:,> .to :tU.t ^'· ·

1Gtual.l.7 obtained iJl the ^{OeDe ·} 'lhl80 OOD.Y80tiCI11101el8 mow that the � erature at the gecaetrioal centre ot t4e can could be oCDid.clered tpoal

ot the whole oan tar b^oth ^statio and. a.gi tated can prooeaMs.

�

!be degreea ot destruot1CII1 _at two mioro-orgam •• 1d. th 41t'h1111l\

"beataoreaiataDoea" ^hll9'8 al110 been oaloulated. trca the oen temperatuN c1Ata.

The .. haft enabled relationabipa between the auaro• ^�· ^aDil the apore 4estruaticn _to be e.tabllab.e4. !be etteota ot -the _Tarioua Pl'Oit...U.C taotora OD the .. relatiCIIlllld.pa, ^· an4 OD tt. rate ot beat tranaf'er to ti­

oan ha're been lltl141ed. !he hotara 111Y8atigate4 wre pl'OMaliDg p:N�

Ul4 length ot prooeaa, tar statio oa aD4 agitate4 ^ea runs, Ul4 type.'IID4'.

apeecl ot I'Otation tor agitated. om ^ruu ODly. 'lhe prooeallbg pre.aura·ta tbe qUated oan runa, an4 ttaa· J.eDath ot the prooeaa in MtJl· agS. tate&.ua

atatia oa runa cSo DOt appea- to ban lligld.fioant etteota, but _the ethota

ot all other taotora studi.e4 are aigDitioant.

•' ·

!he ocmaept ot equin.lent t1ae c!itterenoe, wbioh arises t'roll the relationllbip betwen the extent ot a ohemioal reaotian ^{and the} degree ot spore destruction haa been defined and examined. Jloclel temperature Ta

tiu ourna for a greater rauge _at prooesaea and oan siaea than _that uaecl in the experiments have been oaloulate4 uld.ng heat tranater rate data baae4 on the agitated oan runs, en4 the 4qen4enoe ot ^the eqalftl.elrl tiae 41tterenoe on the tn>e _ot prooeaa an4 on the ld.se _at oan ia aiaouaaecl.-. ^{· ·}

*ltiple reaction �tema in 11hiah llleatrurementa ot the matl ot

HTeral ohemloal reactions, eaoh with titt

erdf

^{aotintiOD aerglea, an}

UM4 to eatiaate _the degree ot destruoticn ot QOrea haTe bee lDnftlgatecl.

!be moclel tn;perature n t1llle ournt�, deri� _{tar the} �· ot the ecpt..­

alat U. clitfer.moe ocmaept, were uee4 with data ^cm the atea ot the

OUOl'OM �a·roootiCXl, _'liliah hu c·llllti.,..tiai>. -- ftr 22.35

��

ID4 ^cm the rates ot two hypothetical reaotiou llith aoti.T&ticll eMI'Sl•• ot 30 an4 ₄₅ kaal/IIOle. latillatiCil ot th• degree ot .ore deatruotica ^wd.»,a reaotiona in pelra ^or in ^groups ot three ia daouan4.

It a pair ot reaotiona ia uaed, a kncnddge ot rates ot hea� trauter

to the oan ia required far aat1ataot017 eatilllaticm ot the lethal etteot _ot heat. _It three reaotiona are U88d, the lethality _ot the prooeaa oen _be

e8tiaate4 111 thottt heat transfer rate _data.

iv

"

Errors arising in the estim:ition of the lethal eff_{ect of heat an}

baoterial spores using chemical reactions singl^{y 1} in pairs, or in groups of three are dieoussed. 'lhe maximum errors in the letha.ll ty of the process as estimated using the various chemical reaction techniques were fOWld to be leas than one qUArter of those arising from the same sources in traditional process calculation methods, in quite a number ot instances much less. It is also shown that unaertainties arising from the necessary experimental measurements can be evaluated much more readily _1'li th a ohem- ical reaction technique, especially the three reaction system, than they oan in other methods of prooess evaluation.

'lhe author 1t'iahes to reoord his gratitude to the following;

Professor R. L. Earle, his supervisor, for his guidance and _con­

tinual encouragement ;

Jlrs

s.

^{F. Rabc:me,} and llise _K. 'lard,'Who typed the draft and final

oopies respectively of this thesis, wQ.ioh, 1t'i th its numerous equations and formulae ^has been far frcm straightforward;

'lhe

Dairy

Production and Marketing Board for financial assistanoe during the early stages of the work; and

Jlr William H. Terry ot William H. Terry and _{Co. ,} Ltd. , WelliDgton, for assistanoe with the oosta of preparation of this thesis.

'!he author aleo wishes to thank his parents for their encouragement throughout, and their tinanoial help, espeoially during the l ater stages

ot the wark.

?i''f

^or

pcm;sqs

THE DmulJ?MENI _OP CANND!G !QUIPWI$T AND P.ROOJit3SING _METHOOO

MIOROBIOI.OO'ICAL IlEVELOiKKN't IlC CANNING _PRACTICE

p1WRlqP!(PT ^OF QAIPULATICif KE'mODS OP PROCESS EVA.LUATICN

(a) Ballio Beoter1olog1oal Data

(1) Heat _{a ..} iatanoe Determ.in&ti_on Kethoda (11) Haat Reai.tanae Data Interpretaticn (b) Basio Beat Penetration Data

(1) �tal Temperature lleuurement lLethocla

1 2

s s 5 9 1)

1lt.

(11) �tal Heating Ourna and Heating Cum Parameters 18

(ill) Appliaaticn ot Heat 'l'ranater 'lheory to Beating Ourna ₂₀

(o) Proaeaa Caloulaticn

2S

(1) B&aea ot Prooeu

Calculation

²⁵

(U ) Teohniquea ot Proaeas caloulaticn 29

(ill) Ncn-m.a._thematioal l4etb.oda of .Prooeae EvalUAticn ₃₅

D�

^{OP mB CHEKICAL} ANALOOUE OF SPORE

DBSTROO'l'I<Jf

J.8

INmJDUCTION 39

DeTelOl!!!ent of th9 ;tn.vczptip;atiop 39

Develqpment

^ot the Qhemioal. Anal.qgue Cone!l)t ³⁹

!x;eerimental _{.Plan l.o}

D�

^OF ,BASIQ gmgc.u, .Al(AWGUE THEORI ltO

NanenoJ.atun ^l.o

Detinitiog ot 'l'!lly and, Integral• ⁴¹

pPore Deat�Wticn JltiaatiC!l t;na cqemioal Reaction (I) lt2

(a) Integration ot lethal rate _with respeat to time at a

single po1nt ₄₂

(b) Integraticn _nth reapeot to vol\llle ₄₃

I?BJELOiKliiRT Of :BAffl'O grpqc.u, ANAitXiUE 'lHEORY- oant.

Spore Deatruetian letimation mn Ohemioal Reaction (II) (a) Integration at lethal rate with re^speot to time at a

single point ₄₄

(i) 'lhe 0 vs _EA funotion for a general process 45 (11) 'lhe ₀ vs _BA f\motion for processes of knoWl. ^or

assumed fona ₄₇

1.

^{!%he 0 vs BA funatian 47}

2. ^{Number or} parameters for standard heat

penetraticn ourna 48

(lli) 'lb.e _{e bact vs} ( 0 ahem (

1)'

⁰ ohem (2)) funotion 50

(b) Integration at e nth re8})80t to volume 51 (i) General unknown ebact s v end· :_,·0Che ^: v

dis_trib^utions. ^{! .. : -. · • •} m ₅₁

(ii) .Known 0baot s T and eohea : v dis1;ributicnas

development at canveotion models.

54

1.

Stationary oan

54

2. Agitated oan 58

INTRODW!'I Cif 60

AiJa at the Project ₆₀

Resume of _{the work 60}

qrwqrw, waax ^6o

Chemioal Sntem Developnent 6o

(a) 'lhe ideal system 60

(b) Selection of _the ahemioa.l. system 61

(i) Iinetio oh.aracteristios of suo rose hydrolysis 61 (11) Anal.ytioal oharaoteristioa of sucrose hydrolysis 62

1. �· 62

2. Ett'eot of temperature 62

3. KutarotatiCil 62

(111) Stability of the system 63

Cbemioal

^S:rstem Deyelopment cont.

(

^{o) Measurement technique}

(d) Rate of hydrolysis determination (i) _low temperatures

(11) High temperatures

vill

6S 67 67 67 (e) Oaloulation of the speoifio rate vs temperature tables 69 (1) Unbuffered suoroae 1

0.00101

^{NHCI, o. 750 )(} sucrose 69 (U ) Buttered suo rose solution t pH 3. 5 70

Temi?erature Me^8.8Ur8Dlent 72

(a) Inatn11umta 72

(b) Calibration of thermooou;ple 11ire 74.

{o)

'lhermooouple oiroui ts 74.

(i) Can thermocouple junctions 74.

(ii) _Sta tic::Da.r7

oan

^{oiroui ts 76}

(ill) Rotating oan oiroui ts 80

(cl) Solmles of error in temperature measurement _a, (i) Cond.uotion errors in thennooouplea _a,

( U ) Electrolytic e_rrors 86

Processing .Experiments ₈₈

{a)

^{Equipment 88}

(1) Steam supply 88

(11) _Experimental retort 88

1. Instrumentation 91

2. Steam supply 91

3. Canpressed air supply 91

4. Cold water supply 91

5. Revolving crate drive 91

(b) P.reparaticn of the retort for prooessing experiments 9'

(1) Instrunenta 93

(U) 'llring �md filling of oana 9'

(111) Arrangement or retort thermooouples 95

(iv) Closing 95

Processing !:J;?eriaent^{a ccat.}

(o) Process o,ale

(i) HolcU.Dg period (ii} Cool 1 ng period

(Ui)

^Sampling

(d) hooessiug experillenta

(i) Suorose hydrol1sis rate determination 1. H,ydrolysis rate determination at

212�

2. Rate ot h1drol711is determinaticn at retort temperature

(ii) Statio oan runs

1.

Temperature distribution runs 2. Suorose h,yd.rolysia runs

3. Suorose, milk, and water oompariscn (iii) Rotating oan runs

Calculation Data

(a) Chemical reaoticn ra.te data (b) Bacterial destruction rate ^data

ix

"

95 96 96 96 96 96 97

97 99 99 99 99

99

103 103 103 103 (1 ) Lethal rate vs temperature 1 B.stearothennopbilua ¹⁰⁵

(11)

^{Lethal rate} vs temperature 1 B. subtilis ¹⁰⁵

Tabulaticn 10S

Plotting ^and Integraticn ¹⁰⁷

Calculation of EQuivalent Retort ^{Times 109}

(a) Equivalent retort time ^from temperature data ^1�

(b) Equivalent retort time ^from suorose hydrolysis data ¹⁰⁹ (o) Calculation of

Ha

^from measurement of suorose hydrolysis

in ag:l. tated ^tubes ¹¹⁰

RESULTS AND DISCUSSION

Statio Cans

(a) Temperature distri butiCD runs (i) Ccnveotion pattern

(ii) Heat ^transfer oaloulations

112 112 112 112 114

�

Statio Cans oc;mt.

(b) Sucrose hydrol.yaia runs 116

116 (1) EquiTalent point determination

(ii) Equivalent retort time correlation (®baot vs0ohe

.>

¹²⁴

(Ui) Equivalent time �fferenoes 126

(c) _Yilk, water, and sucrose solution comparison 128 Agitated _Oans

(a) Temperature distribution runs (b) Suoroae hydrolysis runs

130 133 1.33 (1) _Heat transfer coefficient.

1. Calculation of OYere.l.l heat tr^ansfer coefficients 133

2. C_aupariaon of agitated _can and statio can

overall heat transfer coefficients 136 (ii) Comparison of calculated and measured sucrose

hydrol,yaia oqui valent retort times 137 (iii) Baoterlal equivalent retort times and equivalent

time ditterenoea 139

1 • Effect ot type of' organism (B) 145 2. Etf'ect of speed of' rotation (s) 147 3. Ef'tect of type of rotation (R) 148

4e Effect of length of process (T) 14S

Rgui valent Tl.me Difference Analysi a 151 (a) 'lhe specific rate differenoe f'lmotian 152 (b) Calculation of ^the model can temperature va time curves 157

(i) 'lhe model processes 157

(ii) Rates of he_at transf'er to the model cans 157

(ill)

^{Method of} calculation of the temperature vs time curves for the model cans 1.58 (c) Equivalent time differences for the model oans 16o

(i) Effect of type of organism on equivalent time

difference 161

(ii) Effect of can size and type of process on eq_uiv-

alent time difference 164

1. lf'teot ^of t^otal length of heating and cooling

periods ₁₆₇

2. Et"feot of oan size : square process 167

.,

3.

Et

^teot ot can size _s non-square process 1 68

4. ^Etteot ot length ot prooeaa 169

(4) Appllcat1Cil of equivalent time di fference analysis

conolusiona to real processes 1 70

F\l!dfl M

DE\'IWlP!III!T

^OP

THE OHEKICAL

^AHAIOOUE 1 73

IHTRODOOTICii 1 74

:KULTIPLB RBAOTI

^Cli

SYSTEMS

^{1 74}

1'!!11Perature Tl Time Curves of ^{Beat Pit} 1 74

llethod 1 76

(

^a

) Two

reaotioo systems 1 n

(

ⁱ

)

Temperature vs time curves of ^{best fit} 1n

(11)

Equivalent time d.if'terenoe correlations 1 81

(

^b

)

^�ee reaction systems 1 82

(

ⁱ

)

^{Types ot best} fit curves 1 82

1. T;ype I curve of beat f'i t 185

2. T;ype II cum ot best f'1 t 1 8"7

(U) Oanpariaon ot the

two

^{tn>ea of beat fit curve aa}

methods ot oaloulaticm ot spore d.estruotiCil 489

1 . 'lhe best tit ourvea 1 93

2. BquiTalent time differences and equivalent

retort times 1 95

(111) lloditication of' the analogue 196

(

^iv

)

^:Error in equivalent retort time due to error in

measurement of' retort temperature 1 99

(

^v

)

Integration with respect to volume 201

CONCIDSIONS

ANll POT!Jf'l]IAL APfUCA1:I<DS

^OP

m 9!ffiCAL .AlfAU,)GUJ

²⁰⁵

CONCUJSICBS 2o6

'lheoretioal Conaideratigns 206

'lhe Experiment• 207

(

^a

)

^{Statio oans 207}

(

^b

)

Agitated cans 208

CONCWSIONS oont.

Analysis of the Equivalent Time Difference Conoept 209

Multiple Reaction Systems 21 0

General Conolusioll! 212

POTEN'l'llL .APPUCATIOOS OF mE CHEMICAL Al'lALOGUE 21 3 (a) Kethod for oheoking process oaloulation assumptions 21 3

(b) Evaluation of new or modified processes 21 3 (o) Trouble shooting and control techniques 21 3 (d) Evaluation of the effect of heat on vitamin losses eto. 21 4 (e) Evaluation of the effect of heat in continuous flow

systems 21 4

(f) _low temperature applications 21 4

SDmOLS _AND DEFINITICiffi I RXPERENCES ^I AND APPENDICES SDlBOLS _AND DE.FINI TI CtiS

REFERENCES

APmmiCES

I Canpariaon ot Kass Average Surrival Ratios, Calculated

21.5 216 226

using .Fixed Pa1nt _and Koving Element Temperature Data 236 II Calculation of Equivalent Retort Time for Linear

Prooesses 242

III A Calculation of pR vs A Table 244

III B Inversion of 0.750 K Sucrose : pR vs _A Table 246 IV Caloulation of the .Aoetio acid - Sodium acetate Buffer 247 V Speoifio Sucrose Hydrolysis Rate vs Temperature Table 250 VI A Solution of the Equation ^tor Beating of the 1hermooouple

Junction by Cond\.Xltion along the Wire 2.51 VI B Calculation ot Heat Conduction Error in the 1hermooouple

fi" 2�

VII Lethal Rate vs Temperature Tables for B.stearothermo-

VIII

philua and B. subtilia 262

Sucrose Hydrolysis _{- EAz30} Reaction Speoifio Rate Difference vs Temperature Table

Suoroee Hydrolysis - EAt45 Reaction : Speoifio Rate Difference vs Temperature Table

.APPENDIC:r3 cont.

IX Calculation of Equivalent Retort Times for _Linear Semi-

xiii

loga.ri thmio Prooeaaea 265

X Coe!'tioienta a, b, t.a and 6b for Calculation of

Parameters for Type I Curve of Beat Fit 269

XI Nomenolature of Can Sizea 270