1 4 . 3A unit operations approach of the technology of comminuted meat products with special interest to fixing and grinding

Abraham e . wijlhujzen and ernst j .c . paardekooper

Netherlands Centre for Meat Technology, Dept, of Central Institute for Nutrition and Food Research TNO,Zeist, Netherlands

in the processed meat industry research is mainly focussed on the phenomenological study of product Manufacture. In contrast in the chemical industry the impressive progress has been the result of fundamental Research with special attention to the unit operations. The know how obtained in this way could be implemented in the meat process research. The aim will be the optimization of current processes and aPparatU8 .in this study an investigation has started into the unit operations mixing and grinding by bowl choppers common in meat manufacture. For this purpose model systems were selected to determine the influence of Process parameters thereby enabling the comparison with the comminuted meat system. The mixing rates were Measured in choppers of different sizes and geometries as well as with variable velocity of rotation and consistency of the batter. To compare the mixing efficiency of choppers with other types of mixing devices the mixing rates were described by a mathematical model.*n order to quantify the grinding efficiency an empirical relation was established between the number of Particles and the chopping time. For a number of working conditions the particle size distribution ln relation to the time was determined. Special attention was paid to the influence of the space between the knives and the bowl of the chopper.

Si^Prozesserundvorgänge Mischen und Verkleinern in der Fleischwarentechnologie

a®Raham e . wijlhuizen und ernst j .c . paardekooper

ländisches Zentrum für Fleischtechnologie, Abteilung des Zentralinstituts für Ernährungsforschung TNO, ' Zeist, Niederlande

le ^ieischwarenforschung hat sich bis jetzt hauptsächlich mit den phänomenologischen Aspecten der Produkt-^tatellung befasst. Die eindrucksvolle Entwicklung der chemischen Industrie ist dagegen das Ergebnis einerilJadlagenfor8 chung der Prozesse, wobei besonders die verfahrenstechnischen Grundvorgänge der Prozesse,

besonders die verfahrenstechnischen Grundvorgänge st idiert wurden. Die auf diese Weise erhaltenenei*ntnis8 e sollten in der Fleischwarenforschung verwertet werden, nit dem Ziel eine Optimalisierung

der prrozesse und Apparate zu erreichen.8 diesem Grunde wurden die Grundvorgänge Mischen und Verkleinern untersucht in Schüsselkuttern wie sie der Fleischwarenindustrie gebraucht werden. Dazu wurden Modellsysteme gewählt um den Einflusz der Prozess- taMeter zu bestimmen und doch der Vergleich mit dem komplizierten Brätsystem möglich blieb. Die Mischungs- Aktivität wurde bestimmt in Kuttern verschiedener Grosze und Form in Abhängigkeit der Umdrehungs- 8chvindigkeit und der Viskosität des Brätes. Um die Mischungseffektivität der Kutter mit andern spezi-

g 8c^en Mischungsgeräten zu vergleichen wurde diese beschrieben mit einem mathematischen Modell.^ antifizierung des Verkleinerungsgrades wurde eine empirische Beziehung abgeleitet zwischen der Anzahl

^ Milchen und der Kutterzeit. Für einige Prozessumstände wurde die Verteilung der Teilchengrösze inian8 igkeit der Kutterzeit bestimmt. Besondere Aufmerksamkeit wurde dem Einflusz des Abstandes zwischen MeS8 ern und der Schüssel gewidmet.

E d e llin en sivu tyhjä

1 4 . 3La technologie des produits de viande réduits considérée du point de vue des "unit operations", particulièrement au mélanger en au hachage

ABRAHAM E. WIJLHUIZEN et ERNST J.C. PAARDEKOOPER

Centre Néerlandais pour la Technologie de Viande, Dépt. de l'Institut Central de la Nutrition etde 1* Alimentation TNO, Zeist, Pays Bas

Les recherches effectuées par l'industrie de charcuteries sont concentrées â l’étude phénomélogique de la fabrication des produits, tandis que le progrès spectaculaire dans l'industrie chimique est le résultat de recherches fondamentales spécialement quant aux "unit operations". La connaissance obtenue de cette manière doit etre appliquée â la recherce de la technologie des produits de viande réduits.Le but en est d'obtenir une perfection des procédés et de l'outillage.Dans le cadre de cet étude on a commencé une recherche sur les "unit operations",le mélanger et la réduction par le hache-viande. Pour rëliser cela on a choisi des systèmes modèles pour déterminer 1 influence des paramétrés des procédés et en même temps autorisant la comparaison avec le système de la viande réduite. La vitesse de mélange a été mesurée dans des haches-viandes de dimensions et de formes différentes, avec des vitesses de rotation variables et des consistences différentes de 1a pSte. Les capacités de mélange ont été comparées avec celles d'autres appareils de mélange en décrivant la vitesse de mélange à l'aide d'un modèle mathématique.Pour quantifier la capacité de hachage une relation empirique a été établie entre le nombres des particuleS et la durée. Pour certaines conditions de la procédure on a déterminé la distribution des dimensions i eB particules. On a observé tout spécialement l'influence de la distance entre les couteaux et la jatte de hache-viande.

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1029A ", 1 4 . 3

iüllL_gP«-ration" approach of th„ _____Xefer^ to ,, x «Pedal

ABRA,,AM E - WIJLHUIZEN and ERNST J.C. PAARDEKOOPER

^ t h e r l a n d s Centre lor Meat Technology, Dept of Centr . r °'>d Research TNO, Zeist, Netherlands institute for Nutrition and

oduct 1 on

::::;mainiy ^ t,adi— — - — e. ^ -oduction p e ;hier; m: ;y confined to t„.

- i t oP:r . t i ” : j : ar;cess r ustry fundamentn' — — —The meat „ rof.p _ impressive progress of this industry (F„rkas 1 9 7 7 ).U n c e a s i n g steps to » " r l . t r i ^ d SJnilar,y introduce this method of grouping the numerous

exi«ti„g knowledge of c h e m i d 1 ̂ e nglnelring e’lablln« tbe comparison » 1 th

; erogeneous and compte, composition of meat products l l i t the u

T les of unit °perations which - — — *» i v- i d ! and " tha ChemlCal ind’— - — — — ins. terming.

ThiPrAutomated "" " 1C Cn" th'" * * e l l m l n a t e d - Thls adds to possibilities for®nd q n a i i t d d r : C° T 0 1 tD C°mPly Mlth the COntlnUing ^ ed to - « i - i - material yie.d A , y t 0 reduce «nergy consumption and effluent flows.’*1 th am CharaCterl9tlc of Pcocess research is the use of model systems in combination

the in ; U SCale e X P e r l m e n t S - These »"'-Id be selected in such a way that««opgh U6nCe ° f P r °CeSS Parameters Can be d — tned, where as they should remain close T h ' * tQ practice reality.

" o d 7 POrt describes the 9tudy °f tba nnlt operations mixing and grinding of meat in h o p p e r s .

‘" d T ^ PIaCtlCe theSe tW° unlt operations are performed simultaneously, experimental tnflul °Uld deal With b ° th Unlt operatlons separately. By using model systems the The o : r e °f * nUmber °f P r °CeSS pa r n m et ers on mixing as well as grinding has been shown.

J«ct of this investigation is to optimalize the preparation of batters in such aCnat «an r e a r ____ _______•

w^y th v ' cue prepara t energy consumption and noise production are reduced

■gL_and materials

K sy«tlt ls em °f solld particles is taken as a model for comminuted meat in a bowl chopper.8ased " PCessory to have the disposal of a method for establishing the extent of mixing.Ahd p °n s t a tlstical concepts, a mixing coefficient M is defined as follows(Lacey, J9 5 A

errv 1 0 0 1 . 1

«fe a2

M =2

ao - (12 -

variance of the concentration« of a specific component, added at t = 0 and determined in a number of samples taken at time t. initial variance at t = 0

variance in the completely homogenized batter.

«14.3 1 0 3 0

for a h o ™ o ge„,ou» mixture S c.„ be con.idered «, equal to zero. Tt can be .„own thata complately unfixed material »£ . c (1 -e), where c la the mean concentration of tb. tracer component ( La c e y , 1 9 5 1 ,) .From equation (1) It can be seen that for * ,n _ 2 . 2. 2 2 ’ **0 and consequ®ntly M= 0 . When mixinga completed a .«r „„d M - l . Since M approach«» thla latter value aaymptotica1 ly ita

time dependence i. likely to be of the form:

1 - e -ktor In(l-M) = -kt (2)

where k the mixing rate constant (a- 1 ).

A plot of m ( l - M ) against time should produce a straight line with a slope k, which is characteristic for the mixing process.

As the material for preparing the mixed systems, bacon backs or greaves were used. It w.a ground in a chopper to particle dimensions usual in a meat hatter system. Then a tracer c o m ponent, Sudan Black B or N « C l , was added to a small sector of the doughnut-shaped contents of the bowl. For specific speeds of knives and bowl, the mixing was followed by determining the distribution of the tracer in the tangential direction by taking samples from different predetermined positions in the bowl at each sampling time. For each sampling time the M-value was calculated by means of formula (l).

Gr^mlirigThe grinding process in types of bowl choppers was studied in a system of highly viscous gelatine gel (concentration 15%) cubes of known size and weight. The progress of the grinding process was followed by counting the number of particles in a sample at different times. Assuming that the original cubic geometry is maintained, an apparent particle size d can be calculated from equation ( 3 ).

p N

1/3(3>

where m = total mass of the particles (kg), p = density of the gelatine gel < k g / m ’) and N = number of particles.

Hesults and discussion MixingExperimental work was performed with various types of bowl choppers of a wide range of sizes (laboratory as well as industrial scale), in figure 1 the relation between mixing coefficient and time is given for two systems. The different types of bowl choppers are encoded by a capital letter, while the index indicates the size of the bowl in litres.The results of chopper A ^ Q show an acceptable repet a b i l i t y . Chopper C /n also meets the mathematical model of the mixing process. The slower mixing of bacon backs (system l) ** due to the less firm consistency of the material in comparison with the greaves (system 2 > Table 1 shows the effect of the degree of filling and the velocity of rotation of the knives and the bowl. Two values of the mixing rate constant are given: is defined a«the calculated slope abtained from a plot of In(l-M) against the number of bowl rotati011' and k 2 is obtainGd similarly from a plot of ln(l-M) versus time.From these measurements it can be seen that, as known, the degree of filling influence« the mixing rate. When the degree of filling of the b wl is halved, the mixing rate i* doubled due to an increase in the number of strokes by the knives per unit of weight*When the velocity of rotation of knives and bowl is increased to the rate common f o r wo* of the bowl choppers, the number of strokes per unit of weight remains constant.As can be seen in table 1 , doubling the speed of

1031 I4.3Thl i

ra knives brings on anbs due to a certain restraining

r " u i t * in - m o r * than ,”" f° ,d »f th. .i*i„g r . t. k ,f M t “ dua 4 0 »he higher rotational .peed of th. knives. 2

P ; r ; ; b l ; 2 *h v ffect of th* n u m b *r of knives on the miitin* *« th,.ticular bowl chopper it la clear that addition of extr n*ffeciency in the mixing process. This is supposed to b

*rr»ct on th# flow of the batter.

^ f i g u r e 2 the m i x i n g rate, of « number of industrial scale bowl chopper, are compared.

of . / * th° •fi* Ct ther' l m 8 •IfftifiMnt difference between bowl chopper,• same e l M , due to the geometry of bowl, knives and cover.

b i n d i n g

experiments also included laboratory as well as indu.trial scale bowl choppers. In „ “r * 3 th* P a r t l C l * •lBS "* '’«fined by equation (3 ) t. giv .n a , „ functi„n of thefu *r ° f r o t a t l o n * of th« f o r two bowl choppers. The influence of the degree of theof .. "* a n d _*he 8p8ed ° f rotation is shown. At low speed (see curve 1 ) a particle sice th 4 * 1 0 m 1 8 r8ach8d * « s r 8 0 bowl rotations. When th. speed is doubled (curve 2 ) d,c* P* rtlCla * i” * 1 8 " lr*“d y reached after 2 0 rotations. This more than proportional Th ' r * " 8 8 ° f tH* r0<lUlr8d *r l n d l n * **«• i» due to th. higher rotational speed of th. knives. b 0 effect of the degree of filling can be seen by comparing curves 2 and 4 . When th#

,0 ** C h °PP8r 1 8 C°m p l 8 t 8 l y fill8d ̂curve 2 ) « particle six. of 3 * l O ^ m is reached after »vl rotation.. However et . filling rate of 5 0 % the same particle size 1 . reached*ft•r only 2 0 bowl rotations.

^ • 3 shows the influence of the distance between knives and bowl on the grinding effect,„j'*** r88ulta »re quite remarkable because the particle sis# is decreasing at increasing

*n C * UP tC * C 8 r t " ln value. When the distance between knives and bowl lel, * * 1 in relation to the particle alee the comminution is retarded. This effect might

to the development of bowl choppers of which the distance between knives and bowl 8 reduced during the grinding process. In figure 4 the grinding by different

th U *trlal aeala bowl choppers is compared. It can be seen from the slopes of the lines *t there is not much difference in grinding between these bowl choppers.

the literature little is known q u antitatively about the unit operations mixing and th ndl"* of products in bowl choppers. Attention was paid mainly to the effects on^ Product (C h e s n e y ,1978 and C r o s s , 1 9 7 8 ). More information about unit operations as

'**» given by Thamm,1966 and G o r b a t o v , 1 9 7 0 , The aim of this study was to find a way •ff # m °r« systsmatlc approach of unit operations in meat processing. Th# quantitative ^ ®ct. 0 f process variables on both mlxli.g and grinding have been demonstrated. The

process is dssoribed by a mathematical model. In this way bowl choppers may be pr Par*d with other m i x i n g machines. To come to a complete understanding of the grinding 0 j, *** cere experimental research will be necessary. Energy consumption and the geometry

0 ,,1 , knives and cover will have to be taken into account and attention should be paid li\ n°l8a reduction. In this way an optimalixation of the mixing and grinding operations

"’«at p r o c e s s i n g m a y be achieved.

n*y. M.S. 1 9 7 8 . Properties of restructured pork products as Influenced by meat C particle else, temperature and comminution method. J. Food Sci. 1»3* 1535

* ’ ***R. 1978. Effect of d e s inewing versus grinding on textural properties of beef.

'^a. J .Food Sci. I,3il507' O.F. 1 9 7 7 . Unit operations concept optimize operation«. Chemtech 7 * 1« 2 8

103214.3.... , „ o . F l ..... . Fl.i.chbrat...

Dl» Tleiechwirtschaft, 2 2 1 2 9 7

LaC*y ’ P -M *C - 1 9 H - ° — ™ , in th. theory of partie,. mixing.J- Appl. Chem. 4¡257

T k I Z Fl.bdb.rt, , lh „b.0r„ _ „ l u.... .. W M . IrbSh„„, « „ ...... U..-»,.,,.,,,.,Die Tleischwirtschaft 1 R t 2 5

Table 1. Th. effect of the decree of filling and the .p..d ofrotation on the mixing r B t. of a bowl chopper (type A ).

50degree of apeed of rotationfilling „f the bowl

(k* ) (rpm)

k *Ki

(a)k 0 »100* k 02020

10201020

0.170.230.310.40

aee text page 3 for explanation

u - 1 )0 . 0 2 8

0 . 0 7 6

0 . 0 5 10 . 1 3 2

Table 2 The effect of the number of knivea on th. mixingrate of a bowl chopper (type

S o o * *number of speed of rotation k , * k •

knives of the bowl 2

(-) ( rpm ) (s) (s'1 )3 8.5 0 .1 , 2 0 . 0 6 0

6 B . 5 0 . 2 5 0 . 0 3 63 1 7 . 0 0 . 6 8 0 .1 9 1 ,

6 17.0 0.1,7 0 .1 3 1 ,

aee text page 3 for explanation

Table 3 . The effect of the of a gelatine gel

apeed of rotation of the bowl

(rpm )

distance between knives in- a bowl chopper.

distance between knives and bowl

(I0'3m)

and bowl on the grinding

particle size after 50 rotations of the bowl

(10~3m)

1033 I4.3

and the time for two different bowl choppers types of industrial bowl choppersand systems.System I bacon backs; system 2 greaves

pig. 3. Particle sire as a functionof the number of bowl rotations for two bowl choppers with different rotationspeed and degree of filling.

Fig. 4. The relation between the number of bowl rotations and the number of particles for different industrial bowl choppers