186

COMMERCIAL FREEZING SYSTEMS FOR THE FOOD INDUSTRY*

P . L . MILLER KANSAS STATE UNIVERSITY

In t h e preservat ion of food, t h e purpose of f r eez ing is t h e r educ t ion of microbial , enzymatic and chemical a c t i o n a s s o c i a t e d with t h e d e t e r i o r a t i o n o f t h e food material.

My purpose he re t h i s af ternoon is t o d i s c u s s with you some of t h e systems which have been used i n t h e f r e e z i n g of a v a r i e t y of food products. systems and t h e problems a s s o c i a t e d with t h e i r use! t h e b i o l o g i c a l and enzymatic problems I w i l l leave t o you,

As an engineer I w i l l d i s c u s s t h e r e f r i g e r a t i o n

k e e z i n g systems may be divided i n t o f o u r basic c a t e g o r i e s ,

I. Immersion.

2. I n d i r e c t con tac t .

3, A i r blast or f l u i d i z a t i o n .

4. Freeze (vacuum) drying.

Our primary i n t e r e s t t h i s af ternoon w i l l be i n t h e immersion category.

Heat Transfer

So t h a t we have a common ground for t h i s discussion, I t h i n k t h a t I ahould d i s c u s s t h e basic heat t r a n s f e r r e l a t i o n s h i p s t h a t a r e involved i n t h e coo l ing and f r e e z i n g of foods. t h e ra te of heat t r a n s f e r *om t h e product. funct ion of t h e freezing system and has e s s e n t i a l l y nothing t o do with t h e product i t s e l f ,

The first q u a n t i t y i s This q u a n t i t y is a

Q = h A (Tp - T,) The Q i n t h i s equation is t h e rate a t nhich heat is removed from

t h e food product and t h i s is proport ional t o t h e convection c o e f f i c i e n t of hea t t r a n s f e r (h) times t h e s u r f a c e area of t h e product ( A ) times t h e temperature d i f f e r e n c e between t h e product and t h e surroundings. To have t h e h ighes t rate of heat transfer it is obvious t h a t t h e product ahould have t h e highest poss ib l e r a t i o o f surface area t o

* Presented at t h e 24th Annual Reciprocal Meat Conference of t h e Amerioan M e a t Scienae Association, 1971.

volume, t h e temperature d i f f e rence between t h e product and t h e coolant should be l a r g e and t h e convection heat t r a n s f e r coe f f i c i en t . ~ h o u l d be l a r g e . The convection c o e f f i c i e n t and t h e temperature d l f f e r e n t i a l are t h e items over which w e have t h e most c o n t m l . The u s e of cryogenic materials as coo lan t s has proven popular because of t h e large temperature d i f f e r e n t i a l a v a i l a b l e between t h e cryogens m d t h e normal product f r eez ing temperatures. The heat t r a n s f e r e n e f f i c i e n t 13 an extremely d i f f i c u l t q u a n t i t y f o r which t o obtain a numerical value, This q u a n t i t y v a r i e s g r e a t l y between types o f f r e e z i n g systems, and unfortunately, does not remain cons t an t throuEh t h e f r e e z i n g process f o r any s i n g l e system, and it is also somewhat dependent on t h e magnitude of t h e temperature d i f f e r e n t i a l .

The next heat t r a n s f e r q u a n t i t y which is important is expressed I n t h e following equation.

This is t h e q u a n t i t y of heat per pound of product which must be removed from t h e product t o reduce Its temperature from t h e i n i t i a l condi t ion t o t h e f i n a l s t o r a g e cond i t ion , s p e c i f i c heat of t h e unfrozen product times t h e temperature change necessary t o get t h e product t o t h e f'reezing temperature, t h e second +.em is t h e l a t e n t heat of f r eez ing , and t h e t h i r d term is t h e s p e c i f i c heat o f t h e frozen product times t h e temperature d i f f e r e n t i a l between freezing temperature and s to rage temperature.

The first term is t h e

The temperature of t h e product appears i n both o f t h e above equat ions and it should be recognized t h a t t h e product does not have a s i n g l e temperature. The o u t e r surface of t h e product is t h e first t o f e e l t h e effects of t h e coolant and t h e su r face may pass very r a p i d l y throuqh t h e f r eez ing temperature while t h e c e n t e r port ion of t h e product is hardly a f f e c t e d at a l l u n t i l some later time. For example, i n f r eez ing a t h i c k piece of beef using a l i q u i d ni t rogen d i p i t may be t h a t t h e o u t e r s u r f a c e of t h e beef would be at -3000F before t h e center temperature of t h e beef even began t o change. O f course, I have chosen an extreme example.

In designing any kind of a f r eez ing system both o f these heat t r a n s f e r q u a n t i t i e s must be taken i n t o account. You must know t h e t o t a l amount of heat which m u s t be removed from a product and you m'tst be a b l e t o estimate t h e f r e e z i n g time o f t h e product. t h e most d i f f i c u l t q u a n t i t y t o estimate is t h e cenvection h e a t t ransfer coeff ic ient , and I would l i k e t o spend R f e w R i n n u t e s

s cuss ing t h i s quantity. The convec+i,on cneffic.j.ent is least when t h e surrounding medlum is gaseous and when t h e medlum is a l l w e d t o n l w e n a t u r a l l y , t h a t is, not f w c e d by fans. A typi.ca1 s i t u a t i o n w h ~ e t - h i s would ccr~11r would be j.n cold s t .o rare room?, 07 so c a l l e d "shar~ f r e e z e r s " which are not sharp a t a l l In t h e sense of being pas+. Perhaps a times four increase 1.n t h e cenvection c o e f f i c t e n t can he obtained by forcine: t h p p s e o u s cnolant over t h e Froduct with fane.

Probably

TyFical o f t h l s s i t u a t i o n is t h e a i r h l a s t f r e e z e r where l a r g e

188

f a n s f o r c e t h e air over t h e product at very high v e l o c i t i e s , perhaps up t o 3500 f t per minute (about 40 mph). A f u r t h e r o r d e r of magnitude inc rease i n t h e convection c o e f f i c i e n t may be obtained by spraying l i q u i d coo lan t d i r e c t l y on t h e product which resul ts i n localized b o i l i n g heat t r a n s f e r as t h e coo lan t changes from a l i q u i d t o a vapor while on t h e surface of t h e product, vapor is recirculated over t h e product i n another part o f t h e f r e e z i n g . compartment t o o b t a i n a d d i t i o n a l cool ing as t h e vapor temperature increases . One f u r t h e r o rde r o f magnitude may be obtained i n t h e heat t r a n s f e r c o e f f i c i e n t by direct con tac t between t h e product and t h e l i q u i d coo lan t , b o i l i n g which t a k e s place at t h e surface o f t h e product which causes vigorous c i r c u l a t i o n of t h e l i q u i d over t h e surface and t h u s a very high hea t t r a n s f e r c o e f f i c i e n t , used wi th a c o l l a n t with an extremely low temperature such as l i q u i d ni t rogen because t h e ou te r s u r f a c e temperature of t h e product would decrease far below w h a t was necessary o r d e s i r a b l e i n t h e product, It can very w e l l be used with a c o l l a n t such as carbon dioxide or Freon where t h e b o i l i n g temperature is not so extremely low. t h e product i n t h e l i q u i d coolant does have one s p e c i f i c advantage which I t h i n k I should mention here , and t h a t is i n case t h e product has a ve ry s o f t or e a s i l y malformed surface, such as strawberries, an i n i t i a l d i p freezes t h e o u t e r surface immediately so t h a t t h e product may be more roughly handled during t h e later s t a g e s of t h e f r e e z i n g process and still not l o s e i ts ve ry important shape, o r be bruised during t h a t process.

I n most cases t h e

I n t h i s s i t u a t i o n t h e r e is extremely r a p i d

This last s i t u a t i o n would not be

Dipping

I t h i n k I should warn you t h a t t h e f i e l d of heat t r a n s f e r is a very extensive one, and t h e remarks t h a t I have made here a r e , i n general , g r e a t l y s i m p l i f i e d and can i n no way be used f o r detailed design purposes.

Cryogenic Freezinq

Cryogenic f r e e z i n g may be def ined as f r e e z i n g a t ve ry low temperatures, t h a t is below approximately -5OOF.

"The advantages of very r a p i d f r eez ing of foods have long been recognieed. Most foods g ive s a t i s f a c t o r y products when "quick frozen" by methods commonly used, v i s a i r blast, double p l a t e , and b r ine immersion, but a few products r e q u i r e u l t r a - f a s t f r eez ing i n o rde r t o obtain a product of exce l l en t q u a l i t y . sliced tomatoes, whole strawberries and r a s p b e r r i e s , 'I

Some of t h e s e are mushrooms, (1 )

There a re three " l i q u i f i e d gases" which can be manufactured cheaply enough for poss ib l e use i n food freezing syetemst t h e s e a r e ni t rogen, carbon dioxide and a i r , These materials are e i t h e r manufactured at t h e f r e e z i n g l o c a t i o n o r purchased i n bulk f o r use i n t h e k e e z i n g system and t h e gasea, after use i n t h e f r e e z i n g process, axe allowed t o escape t o t h e atmosphere, Two o t h e r r e f r i g e r a n t materials a re used

i n t h e l i q u i d o r sp ray form; t h e s e are n i t r o u s oxide and *'Weon", a product o f t h e DuPont Company. product f r eez ing process must be c o l l e c t e d by condensation on c o i l s , c3oled by mechanical r e f r i g e r a t i o n t o below t h e condensing temperature, so t h a t t h e coolant may be reused. It would be far t o o expensive t o r e l e a s e t h e s e gases t o the atmosphere,

The gases released during t h e

F!reezing Considerations

There are a number of t h i n g s which must be taken i n t o cons ide ra t ion i n t h e design o r purchase of a food f r eez ing system. Among t h e s e are;

1. Minimum cos t added t o t h e product,

2. Rapidi ty of t h e f r e e z i n g process.

3. Minimum of product dehydrat ion,

4. Minimum c a p i t a l investment.

5. Minimum maintenance,

6, Minimum space requirement.

7. Simple operat ion and automatic c o n t r o l .

8, Minimum o f off-stream time f o r c leaning, maintenance, cooldown, d e f r o s t i n g , and s t a r t - u p ,

9. Maximum product v e r s a t l b i l t y .

10. The p o s s i b i l i t y of under-load/over-load without excessive added c o s t .

"It is an economic fact, r e a d i l y c a l c u l a b l e , that t h e c o s t of removing heat from food by means of l i q u i d n i t rogen , (o r any cryogen) considered alone, is more expensive than w i t h conventional e l e c t r o - mechanical systems. However, when d i f f e r e n c e s i n dehydration, d r f p lo s s , ope ra t ing labor, maintenance, o v e r a l l q u a l i t y , v e r s a t i l i t y , e t c , , a r e adequately reflected i n t h e complete c o s t a n a l y s i s , cryogenic f r eez ing I s of t en less expensive, t h e more pronounced are t h e savings.**

The h ighe r t h e value of t h e food, (2)

In gene ra l , f r eez ing with cryogenic f l u i d s is a n extremely r a p i d process , It is often poss ib l e t o obtain as much as two orde= o f magnitude decrease i n f'reezinq t imes uslnp cryoqenic systems when compared t o conventional mechanical r e f r i g e r a t i o n systems.

The manufacturers of cryogenic f r eez ing systems claim that dehydration l o s s e s , i n general , should be on t h e order of 0.1%. This compares with 3 t o 15% weight l o s s of products which occurs i n conventional a i r - b l a s t f r e e z i n g systems. dehydration o f t e n can result i n improved product texture, t a s t e and appearance, and of course, r e s u l t s i n a higher produet y i e l d ,

This reduct ion i n

It was previously mentioned that cryogenic f r eez ing system usua l ly can be counted on t o have considerably less c a p i t a l c o s t t han a oonventional system, Both systems, of course, r e q u i r e the freezing compartment or t unne l but t h e cryogenic system r e q u i r e s considerably less mechanical r e f r i g e r a t i o n and its a s s o c i a t e d problems of space, maintenance, piping and c o n t r o l systems. O f course, t h e c o s t of providing t h e r e f r i g e r a t i o n capac i ty is included i n t h e c o s t of t h e cryogenic coo lan t , I might add a t this point t h a t t h e r e is at least one company promoting t h e use of " l i qu id air" as a cryogenic f r eez ing medium, and they claim a s i g n i f i c a n t reduct ion i n t h e c o s t of t h e cryogen because it need not be purchased, but can be made l o c a l l y with a r e l a t i v e l y simple and re l iable " l iqu id a i r" manufactwing p l an t . O f course t h i s plant r e q u i r e s c a p i t a l investment i n space and machinery but " l i qu id air" is considerably cheaper and easier t o manufacture than l i q u i d ni t rogen o r carbon dioxide. A l l o f t h e r ami f i ca t ions of c a p i t a l out lay and operat ing c o s t s must be taken i n t o account i n a complete and d e t a i l e d economic a n a l y s i s when consider ing e i t h e r t h e design o f a new p lan t o r t h e a d d i t i o n of f r eez ing capac i ty t o an e x i s t i n g plant .

A cryogenic freezer i s a great d e a l s impler t o operate and maintain than a mechanical r e f r i g e r a t i o n system. are f u l l y automatical ly c o n t r o l l e d and can i n gene ra l be operated by unsk i l l ed persunnel or at least by those with a very m i n i m u m of on-the-job t r a i n i n g ,

The newer systems

Perhaps one of t h e most unique and use fu l , but least recognized, features of a cryogenic f r e e z i n g system is its a b i l i t y to operate e i t h e r above or belon its design capac i ty and still maintain reasonable e f f i c i e n c y . maximum productive capac i ty which cannot be exceeded without producing inadequately frozen food. Most cryogenic f r e e z e r s have a s i g n i f i - c a n t l y greater c a p a c i t y than t h e i r nominal r a t i n g . O f course, l i q u i d ni t rogen consumption p e r pound of product i n c r e a s e s as nominal capac i ty i s exceeded, circumstances d i c t a t e , , . . . S imi l a r ly , a cryogenic freezer may be operated s i g n i f i c a n t l y below t h e nominal capac i ty . consumption i n t h i s mode o f operat ion is not adversely a f f e c t e d but r a t h e r reduced somewhat ,'I (3)

"A conventional f r e e z e r has a d e f i n i t e

But it is poss ib l e t o exceed it when s p e c i a l

Nitrogen

19!

Cryogenic Freezing Systems

Most cryogenic f r eez ing systems operate as "tunnels" o f a v a r i e t y o f shapes. These may be e i t h e r l i n e a r , that i s s t r a i g h t - l i n e operat ion, or t h e belt c a r r y i n g t h e product may be spiral o r c i r c u l a r i n shape which adds t o t h e v e r t i c a l height but decreases t h e necessary f l o o r space. For most e f f i c i e n t operat ion, t h e product and t h e cryogenic material flow i n opposi te d i r e c t i o n s i n s i d e t h e tunnel and gene ra l ly t h e a c t i v e port ion o f t h e tunne l is lower than t h e entrance and e x i t has a tendency t o "set t le" i n a low space. It goes without saying t h a t t h e tunnel , no matter w h a t i ts shape, must be w e l l i n s u l a t e d , Recent developments i n i n s u l a t i n g materials, both i n c o s t and a b i l i t y t o reduce heat t r a n s f e r l o s s e s , have increased t h e p r a c t i - c a l i t y of using cryogenic fYeezing systems,

because t h e cold cryogenic m a t e r i a l

A t t h e product entrance t o t h e tunne l , which is a l s o t h e e x i t l oca t ion o f t h e cryogenic gas, t h e product comes i n t o con tac t with E a s at roughly 500 below product temperature. down t h e tunne l , t h e gas and product temperatures progressively decrease u n t i l about t h e th ree -qua r t e r s point i n t h e tunne l where product is i n con tac t w i t h t h e c o l d e s t gas. A t t h a t point , depending on t h e manufacturer o f t h e tunne l and t h e product, t h e product may be s?rayed with l i q u i d cryoyen. There follows a "equ i l ib ra t ing sec%ion" of t h e tunne l w i t h no a d d i t i o n a l r e f r i g e r a t i o n where t h e product is allowed some time t o come t o thermal equi l ibr ium within i t s e l f . ou te r s u r f a c e temperature w i l l be inc reas ing while t h e c e n t e r temperature w i l l be decreasing during passage through t h i s p a r t o f t h e tunne l .

As t h e product proceeds

?he

There a r e a l l s o r t s of v a r i a t i o n s i n t h e process which may be msde t o handle c e r t a i n products. i n i t i a l l i g h t spray of t h e l i q u i d k e e z a n t a t t h e beeinning of t h e tunnel ; t h e r e may be, f o r thermal e f f i c i e n c y purposes, s e c t i o n s a t t h e beginning and end of t h e tunne l which are cooled by mechanical refrigeration r a t h e r than using t h e " l ique f i ed gas" f o r t o t a l r e f r i g e r a t i o n ; t h e r e may be c i r c u l a t i n g fans t o inc rease t h e convection heat t r a n s f e r c o e f f i c i e n t ,

For example, t h e r e may be an

In tunne l s using l i q u i d ni t rogen of carbon dioxide t h e r e must be an exhaust system t o remove t h e gases *om t h e system and away from t h e area occupied by operat ing personnel. Although t h e s e gases are not t o x i c they axe s u f f o c a t i n g i n hich percentages. In t h e case of " l iquid air" t h i s exhaust system is not necessary except t h a t t h e gas is usua l ly considerably c o l d e r than t h e ambient air . n i t r o u s oxide or Freon t h e r e must be a u x i l l a r y mechanically r e f r i g e r a t e d condensing c o i l s within t h e system t o recondense t h e vapors s o t h a t thn r e f r i g e r a n t may be reused. To operate e f f i c i e n t l y t h e vapor recovery system m u s t r ecap tu re about 99% o f t h e r e f r i g e r a n % ,

In t h e case o f

192

It goes without saying t h a t ambient a i r must be prevented from en te r ing t h e system, This is usua l ly done by providing doors with v a r i a b l e sized openings at t h e entrance and e x i t and ope ra t ing t h e tunne l s l i g h t l y above atmospheric pressure. This is q u i t e easy t o do, and i n fact may be considered an inhe ren t property of t h e system s i n c e t h e r e is a tremendous volume inc rease due t o change o f t h e cryogen from l i q u i d t o vapor. It is q u i t e easy t o a l low a small amount of t h i s gaa t o l eak from both entrance and e x i t doors of t h e tunnel , keeping t h e ambient a i r out .

There are several o t h e r i nhe ren t advantages of a cryogenic freezing tunne l t h a t should be mentioned at t h i s time. if t h e tunne l is properly designed so that no air may e n t e r t h e tunne l during operat ion t h e r e is no d e f r o s t cyc le r equ i r ed during t h e operat ion of t h e tunnel . This is t r u e simply because no moisture is allowed t o e n t e r t h e system, "plain" i n t h e sense t h a t t h e only surfaces t o become contaminated during use are flat walls, t h e moving be l t , t h e spray nozzles, and perhaps a few f a n s and instrumentat ion probes. Thus t h e tunne l is q u i t e easy and simple t o c l ean nhenever it is necessary. One o t h e r unique feature of t h e cryogenic tunne l is i ts p o s s i b i l i t y o f being a "portable" f r e e z i n g system. The e n t i r e t unne l can be t r u c k mounted and moved t o t h e f ie ld for Immediate f r e e z i n g of harvested products , The refrigerant can be c a r r i e d on t h e same o r separate t r u c k s and t h e frorten product can be trucked immediately t o market o r s t o r a g e as necessary,

One is that

The i n t e r i o r of t h e tunne l is q u i t e

Summary

There is much t o consider i n comparing cryogenic f r e e z i n g with conventional f r e e z i n g methods. considered is, unfortunately, as y e t unknown. It is obvious that t h e r e is a place for and a need f o r cryogenic f r eez ing systems i n t h e food industry. be used i n a p r t i c u l a r s i t u a t i o n must be decided on t h e basis of economics, heat t r a n s f e r engineering, and q u a l i t y and q u a n t i t y o f food products t o be frozen. decide whether q u a n t i t y and q u a l i t y cons ide ra t ions are o f paramount importance. then by a l l means use it. f r eez ing systems, then heat t r a n s f e r and economic cons ide ra t ions must be taken i n t o account ,

Much of that which needs t o be

Whether or not cryogenic systems could o r should

You are t h e people who w i l l have t o

If a cryogenic system is necessary f o r q u a l i t y products If it is simply "as good as" conventional

If t h e problem is one of hea t t r a n s f e r and/or design of t h e f r eez ing system, then by a l l means get your se l f a n engineer who knows something about f r e e z i n g systems. You should e i t h e r have your own engineer or h i r e your se l f a consu l t an t . an e n t i r e f r eee ing system o r even t h e a d d i t i o n of c a p a c i t y t o an e x i s t i n g p l an t , t h e c o s t of an engineer should be only a small

In cons ide r ing t h e c o s t of

f r a c t i o n of t h e t o t a l c o s t and i f he is a t r u e p ro fes s iona l w i l l more than pay for h i s services in t h e form of increased e f f i c i e n c i e s , e t c .

Economics is a f u r t h e r cons ide ra t ion t h a t m u s t r e c e i v e very s p e c i a l s c r u t i n y , It is claimed by some manufacturers of cryogenic f r eez ing systems t h a t product added c o s t due t o f r eez ing may be as l i t t l e as, o r perhaps less than, one cen t per pound of product, It is c e r t a i n t h a t c o s t s of producing t h e cryogenic f r e e z i n g materials is decreasing with time and t h e s e changes m u s t be taken i n t o account i n economic dec i s ions .

It is my opinion t h a t a great d e a l of researck needs t o be done, both by engineers and product s c i e n t i s t s , So far as I can a c e r t a i n , v i r t u a l l y t h e only a v a i l a b l e d a t a on t h e e f f e c t s of cryogenic f r eez ing on products, and t h e c o s t s , e f f i c i e n c y , design a n d operat ion of cryogenic f r eez ing systems comes from t h e manufacturers o r s e l l e r s o f such systems, d a t a , but you c e r t a i n l y must ag ree that i t comes from a p o t e n t i a l l y biased source, Independent and unbiased d a t a are needed i f cryogenic f r eez ing systems are t o develop t o t h e i r f u l l p o t e n t i a l . I be l i eve t h a t p o t e n t i a l i s very p e a t and I intend t o follow very c l o s e l y t h e yrogress made i n t h e f i e l d o f cryogenic freezing.

I do not imply t h a t t h e r e i s anything wrong with such

References

1. Tressler, D . K,, e t a l . 1968. ""he Weezing Preservat ion o f Foods'; Vol. 1, p. 153.

2. Brown, D . C , 1967. "The Application of Cryogenic Fluids t o t h e Freezing o f Foods", Advances i n Cryo,oenic Sngineering, Vol. 1 2 , p. 11.

3. . ASHRAE Guide and kt .a Book, Applications, 1968. American Society o f Heating, Re f r i ae ra t ion and Air-Conditioning Engineers,

H. J . TUMAI Thank you, P a u l . Next I would l i k e t o c a l l on R r , d i l l S t r i n g e r t o lead OUT d i scuss ion . B i l l .

W, C , STRINGLSt You know we had t o drop out one part of t h e program and Don Kropf said, "Now whatever you do, don't make a speech. Paul s ays , "Say anything you can t o impress Mr. Thomas." I ' m not going t o make a speech and they've almost used up all our time, but we do have a few minutes f o r ques t ions , s o s t a n d , g i v e your a f f i l i a t i o n and state your quest ions. s o please use them.

We do have microphones

CHARLIE COOK, CENTRAL SOYA COMPANY1 I would l i k e t o d i r e c t a quest ion t o Don. In your r e c e n t experiments have you eve r experienced s h a t t e r i n g over a c r i t i ca l temperature? some work i n this area and we f i n d a very f i n e temperature l i n e between s h a t t e r i n g and not s h a t t e r i n g i n meat c u t s ,

We have done

D . H . KROPFr Yes, sir. There is a p o s s i b i l i t y of t h i s , p a r t i c u l a r l y when we use Immersed l i q u i d n i t rogen , cracking and p o t e n t i a l s h a t t e r i n g and, of course, t h e product is extremely fragile i n t h i s state after i t 's been put i n t h e f r e e z e r .

We might f i n d

P. MILLER; I l i k e d h i s comment that t h e immersed l i q u i d ni t rogen is r a r e l y used because t h e o u t e r temperature goes down s o far s o fast that s h a t t e r i n g w i l l occur. Usually i t 's only a very l i g h t and ve ry quick d i p o r s p r a y that drops t h e temperature down below t h e flreezing po in t and t h e product w i l l be b e t t e r u sua l ly , What I ' m saying is you have a much g r e a t e r p o t e n t i a l i n t h e l i q u i d ni t rogen 3200 temperature d i f f e r e n c e than i n o t h e r s ,

UNIDENTIFIED SPEAKER1 Question not recorded,

D . H . KROPFI H e asked i f some oxygen was needed i n t h e package t o develop t h e b r i g h t c o l o r ? of d e t e r i o r a t i o n , p a r t i c u l a r l y i f t h e product was thawed--some micro-biological d e t e r i o r a t i o n , We are aware of t h i s p o s s i b i l i t y and, of course, w e c a r r i e d our tests through t o q u i t e a few taste panel t es t s as well, after va r ious periods of d i s p l a y and s to rage . And here a l s o w e might add, o t h e r c r i t i c a l element is l i g h t i n g , which could f u r t h e r a c c e l e r a t e oxidat ion and d e t e r i o r a t i o n . In our taste panel work after d i sp lay f o r long periods of time, we have not reached t h a t unacceptable po in t , It's our opinion t h a t w e don't want t o l e t oxygen go through a t a n uncontrol led rate, i n o t h e r words, t h e more t h e merrier. We're not t ak ing t h i s road a t a l l . We would l i k e t o f i n d out w h a t l e v e l we need t o keep t h e c o l o r b r igh t and limit it t o t h a t l e v e l .

Is t h e r e not a p o s s i b i l i t y w i t h t h i s

It appears t h a t t h e enzyme r e a c t i o n s involved here are a c c e l e r a t e d a t c e r t a i n po in t s as we are going through t h e removal of heat and t ak ing water from t h e l i q u i d phase t o t h e s o l i d phase, Now t h e r e have a l s o been some o t h e r meat programs i n t h e Southeast that I ' m aware of where they s o l d meat i n t h e purple-red s t a t e , I don't know i f this was f r e s h o r f rozen. It could have been a fresh system and this is a f a i r l y s u c c e s s f u l program. ano the r approach, but our darkening is q u i t e a s e r i o u s problem and I t h i n k first w e have t o s e l l t h i s s t u f f and then a l s o have t o avoid a new d e t e r i o r a t i o n .

Now t h a t is

Does that answer your ques t ion?

P , MILLER1 Personally, I might relate a n i n t e r e s t i n g conver- s a t i o n I had yesterday evening, I was wandering around looking f o r someone familiar and d idn ' t f i n d anyone, but t a l k e d t o John Bird of Hutgers University, He is a muscle micro-biologist and would come

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t o words I can ' t even pronounce, but it's g o t something t o do with i s o l a t i o n and p r o p e r t i e s o f muscle lysosomes, Now he t a l k e d f o r about t e n minutes, and w e f i n a l l y got down t o t h e ground where w e understood each o t h e r ' s language and what he f i n a l l y t o l d me was that t h e f r eez ing ra te w a s v e r y important i n c o n t r o l l i n g t h e release of t h e s e bad l i t t l e t h i n g s t h a t eat up t h e meat, Mow i f t h i s is so, this is c e r t a i n l y a n area of r e sea rch t h a t needs t o be c a r r i e d on among meat scient is ts--people l i k e him and myself, who know about f r eez ing rates and how t o c o n t r o l them.

DALE H U F " : Don, I wonder i f t h i s oxygen demand you have is immediate during f r eez ing o r is t h i s during s t o r a g e ?

D . H . KROPF: Isle, I t h i n k it depends on t h e t i g h t n e s s of t h e package and we're t a l k i n g about t h i s type of packaging film, t h i n k t h a t t h e demand occurs very r a p i d l y , mckage f r e s h meat i n t h i s system we have a s e r i o u s problem. got t o g e t it r i g h t i n t h e f r e e z e r o r we w i l l have t h e same darkening occurring here , so i t would be r a p i d ,

We

We've For in s t ance , i f we

D . HUFFMAN: Don, I guess t h a t quest ion is--Do you observe t h e c o l o r d i f f e r e n c e immediately after it is f rozen o r a f t e r a period of s t o r a g e ?

D . H . KROPF: Yes, we d i d observe t h e c o l o r d i f f e r e n c e s immediately a f t e r f r e e z i n g and i n most cases, Dale, a f te r 1 day, 3 days, 7 days, 21 days and e i t h e r 35 or 42 days of d i s p l a y o r dark s t o r a g e ,

rJ. C . STiUNGER: Another ques t ion?

CHARLIE COOK: I would l i k e t o make a comment on t h e quest ion of Dale's. I n t h a t o t h e r muscle indus t ry , we had b a s i c a l l y t h e same problems with frozen f r e s h pou l t ry , After much experience, much f r u s t r a t i o n i n consumer acceptance of the product , t h e r e h a s been a compromise a t t a i n e d i n t h e fonn of deep-ch i l l ed pou l t ry , During t h e scope of your i n v e s t i g a t i o n , Don, d i d you l o o k a t t h e p o s s i b i l i t y of deep c h i l l e d meat i n terms of t h i s and w h a t advantages can be gained?

'rl. C . STilINGEFi: The quest ion is t h e advantages of deep c h i l l i n g r e d meat,

D. H. KROPF; d e l l , we've t a l k e d about i t but we haven't r e a l l y looked at it . I th ink , Charl ie , t h a t t h e one thing t h a t concerns me is with t h e deep-chi l l , a c t u a l l y we're s t a r t i n g t o f r e e z e a l i t t l e b i t probably and we're starting t o g e t i n t h i s area uhere w e n igh t maximize some of t h e s e enzymes r e a c t i o n rates, Ne are very c l o s e t o t h a t l i n e and I th ink some poss ib l e d e t e r i o r a t i o n o r maybe speeding up oxygen demands and t h i s kind of t h i n g could occur. We do want t o work w i t h tempering and hard c h i l l because we th ink they w i l l adapt o u r whole process t o shaping and t o port ioning. machinery t h a t has come around, T t n ink , w i l l l e s sen OUT c o s t and i t 's worthwhile looking at it .

Some o f t h e new

DON NAUMANN: Don, you s a y your people have been working with W h a t economists as well as engineers and you j u s t mentioned c o s t .

do t hey p ro jec t as t h e c o s t of t h i s process as compared t o t h e c o s t of t h e t r a d i t i o n a l t ype o f merchandising?

D. H . KROPF: Harold, you may have t o h e l p me out o f t h i s , but I th ink t h e f igu res I s a w on t h e s e c o s t s would be something l ike-- what was it--0.6 c e n t t o 0.7 c e n t per package and f i lm c o s t of 3 c e n t s , Maybe I had be t te r l e t Harold answer that.

H . J . TWi: I w a s going t o lump them toge the r . I s a w some f igu res j u s t r e c e n t l y t h a t our accountant came up with, not published y e t , you may have your own comparison and your r e t a i l c o s t w i l l vary a g r e a t deal,

These are To ta l l abo r , equipment was roughly 16 c e n t s and

W . C . STRINGER: Sixteen f o r what?

H . J . TUEIAt Sixteen cents p e r pound f o r f r eez ing , packaging.

W . C . STRINGER: We have time f o r one more quest ion.

DON KINSMAN: What's t h e temperature you r e a l i z e from l i q u i d a i r and l i q u i d COz?

P. MILLER: I had those f i g u r e s a l l w r i t t e n down and somehow I l e f t them at home, Liquid air is j u s t l i q u i d a i r and l i q u i d n i t rogen mixed toge the r . C02 I t h i n k is around minus 1000 o r l O 9 O , p r e t t y c l o s e . Weon is a l i t t l e h o t t e r ,

Liquid air is t h e same as l i q u i d n i t rogen ,

'i, C . STHINGEii: Thank you, Paul, and we do a p p r e c i a t e Don and you being with us.

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