217.
CHEHlCAt CHANGES
8 . S.
IN I R R A D I A T E D HEATS
SCHWEIOERT
.*.............-.....*..*...-..
....-......*.
A M E R I C A N MEAT I N S T I T U T E F O U N D A T I O N
Mr. Chairman, Ladles and Gentlemn: I am sure you are aware by
now t h a t t h i s potentially new processing wtbod is w i n g along with rather
significant s t r i d e s and there are many challen$es i n research r e l a t i v e t o
t h i s as well as t o any other processing method.
Fundamentally the e f f e c t of ionizing radiation i n application t o
mats i s the ionization of water, since the ionizing radiation induces free
radicals from the water in meat and, of course, mat i s e s s e n t i a l l y an
aqueous system Thus the question we ask ourselves on chemical changes comes
down basically t o w h a t effect do these free radicals have on the important
chemical constituents of meat?
These changes a r e primarily oxidative i n nature i n so far as the
wer-all studies are concerned. In our studies a t the Arcerican &%?at Ins t i t u t e Foundation we are basically interested i n detemining t h e nature
of the chemical changes that occur i n meat6 during i r r a d i a t i o n and i n
measuring the magnitude of those changes.
"he t o t a l chemical change is actually very small and it has
taken considerable ingenuity t o develop sensitive encugh methcds t o measure
sane of these changes. Ehen though the associated acceptability characteri s t i c s may be profoundly changed, the chemical change may be very small.
So I should l i k e today t o review the work t h a t is being done i n Dr. Doty's
division and i n our biochemical and n u t r i t i o n divisfon on the chemical
changes t h a t occur i n meat during irradiation.
I should like t o emphasize that we believe these studies w i l l be
of importance not only w i t h respect t o the v a r i a b i l i t y of radiation, but
with r e s p c t t o the fundamental problem of w h a t is the chemistry of meat
flavor, w h a t is the chemistry of mat color and of odors. Certainly we
have a gross inadequacy of such data on mat as w e l l as other foods and it
is a real opportunity t o understand more f u l l y the complex chemistry of
meat.
(Slide) Thla is a basic orienting slide, which t h e two previous
speakers touched on primarily, and certainly we are interested i n such
f a c t o r s a8 color, flavor, odor, texture, n u t r i t i o n s t a b i l i t y , wholesomeness
and cost. The primary study on the cheulical changes, of course, r e l a t e s t o
the f i r s t two that we are going t o discuss today.
Dr. Schultz referred t o a modest change in texture which wmld
indicate that there is sone denaturation of the protein and reduced waterholding capacity. This 8eem t o be r e l a t i v e l y minor i n magnitude.
(Slide) O n e of the first studies conducted by M r . Paher, i n
D r . Doty's division, was t o deternine the e f f e c t of radiation on one of the
218.
important tripeptides, glutathione which is glutamyl-cyetamyl-glycine, It
was one of the first chemical changes we were able t o detect associated
with i r r a d i a t i o n in which a significant amount of glutathione i s destroyed
during radiation of ground beef. I night add here froln an orientation
standpoint that we are purposely using ground beef and an i r r a d i a t i o n dosage
of 2 t o 10 million rep t o mgnify the extent of the chemical change f o r
purposes of measurements. Documenting the evidence on t h i s basis w i l l
then permit ut3 t o work back t o a lower l e v e l application o r t o situations
where less chemical change may occur. First you have t o documnt t h e
gross and then work back t o details.
You w i l l note one indication here, that I f the beef contained
more intramuscular f a t the amount of glutathione destroyed was certainly
emll. W
e have not followed up with further experiments, but we think t h i s
m y have some significance,
(Slide) Here we show another experiment, varying the radiation
dosage of gound fresh beef muscle from zero t o 10 million rep, and you can
again see the destruction of the glutathione with increased radiation
doeage. We a160 have indicated here one of the chemtcal constituents which
we are convinced is associated with the off-flavor8 and odor produced, and
we particularly a r e concentrating on odoriferous quantities here, namely,
hydrogen sulfide. 1 8 also find methyl mrcaptan produced. These I w i l l
grant you are in r e l a t i v e l y small quantities, and i n Gubsequent experiments
by D r . 8chwinsky i n Dr. Doty'e laboratory we find in the range of 1 t o 2
micrograms per gram of hydrogen sulfide produced and the amount does increase with radiation dosage and s l i g h t l y more than methyl mrcaptan.
This wa8 a real challenge a n a l y t i c a l l y but the boys w e r e s u c c e 6 ~ f'ul i n working aut some c o l o r o m t r i c mthode which seem t o work now very
well we think on irradiated mat snd, of course, I am sure of the fact
that even though it is i n the range of 1 t o 3 parts per million, those compounds can have a profound influence on acceptability.
e a l s o have looked a t the chemical c h q e s t h a t occur
(Slide) W
i n the fat. It was a surprise t o us that beef showed a greater C h a n g e
than did pork. So we were interested i n looking a t various components of
mat cuts. I n this particular caae we were studying the midative changes,
specific peraide values i n an irradiated and non-irradiated meat and then
after subsequent storage, W
e used an cfxygen-permeable casing, a regenerated cellulose casing supplied by Siakind Corporation as an example of 8
case which would permit the entrance of ocDygen and a Saran casing, a casing
impermeable t o oxygen, f o r comparative purposes, You w i l l note t h a t there
i s a sua11 increase in the peroxide formation a t 2.4 as indicated under
the radiated column, and after storagg there is a profound increase in. the
peroxide number, rancidity developing when the packaging material i s permeable t o oxygen, but an insignificant increase when the package i s impermeable t o oltygen.
W
e can make t h e broad generalization that packing material, such
a metal-sealed can o r f i l a n e n t s which do not l e t oxygen get through
minimizes these undesirable chemical changes subsequent t o and during
irradiation. The color is quite good, a8 D r , Schultz pointed out, provided
oxygen is kept away during and subsequent t o irradiation.
a6
219.
(Slide)
tJe a l s o have been loohing a t other oxidative changes
that may occur In the lean o r in the fat of meat. We can state t h a t the
primary undesirable odors t h a t are produced arise e s s e n t i a l l y from the lean
and not from the fat. However, there may be chemical changes in the f a t
that indimA;ly influence the extent of the chemical change i n the lean of
the muscle itself. Here we are attempting t o determine the carbonyl compound prcduced in ground beef a8 infl.ueaced by the o r i g i n a l intramuscular
f a t content of the beef muscle a d , 88 you will note, l e e s carbonyl i s produced and extracted by an acid salt solution here when there is a low l e v e l
of f a t in t h e meat. W
e have e m indicatione, not well documnted, t h a t
t h e higher the intremuscular fat the less the undesirable e f f e c t from an
odor standpoint in the mat. Whether t h i s l e correlated with the reduced
amount of carbonyl compound under that situation await8 f u r t h e r etmdy.
e were then intereeted In seeing what is the nature
(Slide) W
of these carbonyl corrpounds. llhis is a C double bond 0 t y p of compound,
and here we a r e attempting t o e x t r a c t with a polar solvent of acid salt
solution when f a t was irradiated and when t h e mat itself' w e irradiated.
This is r a w beef you see under the heading of fat there. You will note
that the amount of carbonyl cacrpound produced does increase with t h e irradiation dosage, and that basically most of them are e x t r a c t i b l e from the
meat and relatively small amounts were produced Pram those t h a t were ext r a c t i b l e by a higher polar solvent. This suggests t h e i r r e l a t i v e molecular weight and that they are capable of being trapped by such an acid
solvent.
(Slide) With the use of a fat-soluble solvent, such a6 benzene,
however, quite s i g n i f i c a n t amounts of carbonyl compounds are e x t r a c t i b l e
from the f a t and i n t h i s case it w l 1 1 e x t r a c t r e l a t i v e l y l i t t l e from the
meat, the point being here that the type of carbonyl produced i n an irradiated f a t is a t l e a s t in part d i f f e r e n t from that produced during irradiation of beef muscle i t s e l f , We now are p r e p r i n g the 2-4 nitrohydrogen derivatives from those carbonyl compound8, separating them on aluminum
columns and we h o p t o identify t h e m . W
e know t h a t there i 6 a s e r i e s of
them, a t least f i v e o r six d i f f e r e n t d i s t i n c t e n t i t i e s produced i n the
oxidation presumably of the unsaturated f a t t y acid i n the case of those
t h a t are benzene soluble and from an unknown precursor i n the lean
portion, part of which may be from f a t , of course.
(Slide) Now that gives you up t o date the specific data. Here
I would l i k e t o show them graphically f o r tbe amounts of carbonyl compound
produced during i r r a d i a t i o n a8 measured by determining the absorption
s p c t n t of the 2-4 nitrohydrogen derivatives a t various irradiation doses.
You w i l l note on the lower curve, which is no irradiation, there
are S m a l l traces of carbonyl compound that we can form with t h i s reagent
and 8s the dosage l e increased t o 2, 4 , 6 and 10 million reps, the quantity
produced is increased which you can see by the numbers on the previous
slide, and there are some indications here, which we won't go i n t o tb.ough,
that there is more than one canpound produced, and perhap6 the nature is
influenced somwhat by the i r r a d i a t i o n dosage, since the peak of the maximum absorption tends t o s h i f t .
(Slide) From the f a t we have a very complex picture i l l u s t r a t e d
here where the meat f a t i s irradiated. No. 1 is the control fat, and 2, 3 ,
220,
4, 5 and 6 refer t o 2, 4, 6 and 8 million rep treatments r e s p c t i v e l y . You
w i l l see that we have a rather complex absorption curve indicating several
peaks and not c o m i s t e n t l y related t o the irradiation dosage i n some i n stances which tells us that we have a complex mixture of carbonyl compound
which is going t o be a real t e s t t o s e p r a t e and identify. Nevertheless
t h e carbonyl compound produced is a characteristic chemical change occuring
i n mats during irradiation. When m e n is present the oxidative changes
that occur i n meat fats are i d e n t i c a l toauto-axidation, as we know it, but,
of course, a t a much accelerated rate because of free radical formation.
(Slide) The l a e t two years I have had an opportunity t o discuss
some of our meat pigment research with you. I w i l l not dwell on t h a t
phase here
I believe t h a t Dr. Schultz summarized It very w e l l , but I
w i l l state again that if oxygen i s kept away from *,be meat pigments the meat
color i s quite acceptable. However, if cxygen is present with an accelerated production of me tmyoglobin, the undesirable brown color occurs.
Here we took some ground beef, irradiated i n oxygen-permeable
membrane, and attempted t o characterize the features of heme piguents by
reflectance measurements. The upper curve is f o r the irradiated meat
outer core and shows a peak a t something arouncl 615 millimicrons which
characterizes the irradiated meat as well as decreased axymyoglobin and
some increasedmetqpglobin formation. We could bring these changes out
a l i t t l e by extracting the Na. t o t a l from a piece of meat which minimized
the effect seen on t h e outside of the piece caused by radiation because,
of course, there is less change i n the inner core of the sample.
e are interested i n t h i s , however, bec&use of t h i s
(Slide) W
pigment t h a t occurs a t 614 millimicrons which is green when one gets a
system f o r preparing s u f f i c i e n t quantities of it. This is of i n t e r e s t
because of the greenish discoloration of other meats and perhaps the Sam
type of chemical change occurs. W
e were a010 by electrophoretic technics
t o separate the green pigment produced from the qwglobin and t o show that
the chemical a l t e r a t i o n occurs in the hem nlyoglobin 8 8 indicated here.
When acetone cleavage of the heme was carried aut, the isolated hemin derivative after appropriate phamtography shows d i f f e r e n t absorption peaks
which you can see from t h i s slide which we have characterized mtmyoglobin
and hemin and irradiated extract. The cleft irradiated e x t r a c t shows the
altered heme p i p n t . This appears t o be an oxidation of the porgkyrfn
e have not been able t o
ring;, but it i s quite an unstable quantity. W
build up a sufficient quantity t o unequivocally characterize it. But we
are s t i l l accepting the challenge and hoping that we can achieve it.
It i s of i n t e r e s t that when uxygen is kept away it has a very
bright color and I believe t h a t Mr. Schultz said that it looks even more
red than the non-irradiated. A l l of our chemical data t o date suggests
that it is s t i l l i n the presence ofoxyrrglbglobin, although we have had some
preliminary ideas in the last few weeks t h a t perhaps it i s a ferrylmyoglobin with a valence of 4, W
e w i l l have t o check t h i s further. A t any
rate froman aver-all gross standpoint, the color, if the oxygen is kept
away, i s quite satisfactory.
(Slide) Also so= e a r l i e r work i n Dr. Doty's division showed
there was a change i n the proteolytic enzyme a c t i v i t y of irradiated meat
221.
in i r r a d i a t i o n dosage weighing on the order of 1.5 mfllion rep as indicated
by samples 2 and 3 on t h i s elicle in which casein was used as a substrate
and tyrosine iiberaticm WBB measured. With .S million rep there was relat i v e l y less change.
I should restate Lhst. There was r e l a t i v e l y l i t t l e change in
a c t l y i t y . This, of course, i s of significance i n
terms of w h a t might happen i n storage of radiated mat, for instance, e t
room temperature
We have had ground beef etored for a year and opened it
up and its texture was grossly unchanged from that eeen inrmediately after
i r r a d i a t i o n . There was a small amount of white c r y s t a l s on top which other
laboratories have shown t o be tyrosine which presumably have been s p l i t off
by proCeolytic enzyme a c t i v i t y but it certainly does not liquefy. The
proteolytic e n z p e a c t i v i t y , i f s t i l l remaiaiag a t i r r a d i a t i o n doses, does
not bring about gross changes i n texture.
the proteolytic en-
(Slide)
I wanted t o go over SORE of the overall chemical changes
that have been documented in our laboratory as well as i n others, irrespective of whether they are d i r e c t l y aseociated with specific acceptability
attributes
.
D r . Morgan referred t o the B vitamin destruction. Certainly
t h i s i s significant chemically, and i n meats, being one of the r i c h e s t
source6 of thiamine, t h i s is quite important.
Pigment a l t e r a t i o n s , 88 I referred to, can be detected and cert a i n l y are i l l u s t r a t i v e of the oxidative changes that can occur where
axygen p a r t i c u l a r l y is available either during or subsequent t o irradiation.
I touched on the production of peroxide in the fat.
it is minimal if oxygen is kept away.
There again
These carbonyl compounds are produced even in the sealed can
that I referred to. Some of them appear t o be primarily derived from the
fat. Others from the lean portion of the tissue6 of unknown precursors.
We think they may be i n d i r e c t l y very important. It i a possible that these
carbonyl compounds can complex with the sulf'hydril compound produced and
may indirectly have a g r e a t modification on the extent of the odor produced
and may be of some significance during some of these changes that occur
during storage. Whether the destruction of glutathione is a muse and
e f f e c t relationship with hydrcgen sulfide and raethyl mercaptan production
we do not how. W
e are hoping t o do some studies with radio-active sulfur
with glutathfone and methione t o check t h i s point.
O u t at Oregon State College, Dr. Bubl has shown that he has been
able t o detect a fluorescent cornpound produced during irracliation, the
amount of which seem t o increase with i r r a d i a t i o n dosage. W
e don't know
of its significance as y e t but I think it f a of i n t e r e s t t o add here.
Looking back over the last few years of work in t h i s f i e l d we
f e e l that we now have several good chemical e y s i n which quantitative
mthcds f o r measuring these chemical changes can be made. It is now we
believe about t i m e we apply t h e m systematically to a set of technol-o$ical
variables such as characterizing the extent of these changes i n beef as
222
0
compared t o pork, f o r instance o r t o pre- and postirradiation t r e a t r e n t t o
see which, if any, bear a d i r e c t relationship t o the acceptability a t t r i butes that Dr. Schultz mentioned. If' we can get sorue chemical handles that
relate d i r e c t l y t o the taste panel results, it w i l l certainly be of great
i n t e r e s t s c i e n t i f i c a l l y as well as t o the irradiation project,
On an over-all basis, in summary we believe that we are learning
a l o t about the chemical constitution of meat and factors influencing the
extent of these chemical changes. Certainly one of the m$or areas has
been the devising of adequate and senstive raethods t o wasure the extent
of these chemical ch~ngesd u r i q irradiation, and we now are in a position
we believe t o carry these studies on i n a systematic way w i t h the technological variables referred to.
Thank you very much.
Paper
CHAIRMAN PEARSON:
I want t o thank D r . Schweigert f o r h i s
We w i l l now have discussion on the microbiological aspects
and discussion on the previous paper which w i l l be handled by Dr. C.
F. Niven of the American k a t I n s t i t u t e Foundation.
DR. C F, N m : W. Chairman and Gentlemen: The only
purpose of irradiation is t o preserve the meats, t o k i l l the microorganisms, and the toughest of a l l microorgans t o irradiate are the
spores of microorganisms j u s t a6 they are with therxnal processing.
One microbiological aspect touched upon by a l l three of
these speakers was the use of low leveas of irradiations for the
purpose of extending the shelf l i f e of f r e s h meats without s t e r i l i zation. John Ayres t h i s morning mentioned t o you that t h e pseudomonas
a r e the most common spoilage microorgans f o r fresh meats. They are
gram negative mows microorganfsm, psychrophilic, They grow quite
rapidly even a t freezing temperatures. It just so happens t h a t these
microorganisms, theee pseudomonas, are among the most radiationsensitive of a l l microorganisms.
W
e have repeatedly observed i n our laboratory that a dosage
i n the neighborhood of 75000 rep subjected t o meat w i l l completely
kill a11 of these pseudomonae from t h e meat and thereby an extension
o f f o u r t o f i v e times i n shelf l i f e i s achieved a8 mentioned by Bruce
Morgan. I am referring t o the bacteriological shelf l i f e of meat,
However, there are other problems t o consider i n the so-called extension of the shelf l i f e of meat, t h a t are not bacteriological, and
they are the color retention of the meat as it is being stored, and I
a m not referring t o the color variation, the color e f f e c t s due t o
irradiation, but t o the color as influenced by dehydration.
223.
h e r e may be other ojridative changes that we are not completely mare of'. The problem of d r i p l o s s and the generally lower
appearance of the meat due t o a nwiber of factors that we don't know
about and, of course, it is very d i f f i c u l t t o Judge when the meat is
acceptable with respect t o appbarance and when it is not. So the
endpoint in its effective dispby l i f e i s dif'f'icult t o determine.
In general, the gram positive microorganisms are more
ratHatIan-resistant than are tb gram negative, and I am referring t o
42.x ncln-spore forming microorganisms now. b o n g t h e cured meat spoilege deroorganlma are predominantly gram positive; therefore, we 6hould
not expect the dramatic increase in shelf' l i f e with cured m a t e irrattiaf;ed a t low dose levels and that happens t o be the case when we
-8% erperimntally in the laboratory employing in t h e neighborhood
of 100,000 rep. However, one should relrvelnber t h a t the inheren% shelf
lift?of care& meats i s stgnificantly longer than one expects with
fresh meats.
We have been toying with the uae of' other preservatives
than irradiation and combinations of' these preservatives along with
ionizing radiation f o r the preservation of fresh meats. In brief
sumnisry,by using appropriate combinations of ionizing radiations,
tetracycline antlbiotic, and ascorbic acid, we can effectively extend the l i f e of meats t o the point where the microbial spoilage is
of l i t t l e consequence in determiniag the l i f e of the meat. Other
factora enter in, as w have already mentioned.
Here again, however, we nust consider these other factors
as being very important a why are we doing t h i s ? Again a s John
A y r w mentioned t h i s morning, the primary purpose is t o achieve something that is impossible t o b y ; t h a t is, prepackaging of f r e s h meats
perhaps a t the wholeeale level. Most of' the foode have l e n t themWlVeS t o t h i s procedure and have been quite well accepted by the con'Burner.
Fresh mats thus far cannot be handled because of their high
perishability,
Same of the important spoilage microorganisms that m ~ 6 be
t
consPdered in irradiated *ate as well as those treated with ionizing
radiation i n combination with antibiotics are the yeasts and molds
and especially the yeasts. There are a ma;il5erof different types of
yeasts that are so-called psychrophilic being able t o grog a t freezing
temperatures 033 the surface of meats. They occur there a s surface
contaminants. Tbey are perhaps the most important group staring us
in the face when we use these new processing and preservation technics.
I mentioned before that bacterial endospores are the most irradiationreeistant of a l l microorganisms. However, there is one star exception
dust touched upon by one of our spahers, Eamld Schultz, and I should
like to open the question period by asking him i f he would care t o
expand a l i t t l e on t h i s irradiation-reaist& microorganien discovered
by them and also as t o i t s possible significance.
DR. SCHuflllz: I t h i n k that Dr. Nfven can answer it better
because he Just did a good deal of confirmatory work after we first
found the organism. W
e f i r e t noted it in so= cans that had been held
224.
under storage f o r a period of time, The cans began t o swell and there
was putrefactive spoilage, The Bacteriology Departmnt was able t o
i s o l a t e the Micrococcus, non-spore former, and have since that time
demonstrated that it w i l l withstand irradldtion dosages of 6 million
rep, and t h a t i s well beyond w h a t we want t o use if we a r e going t o
have an acceptable product flavor-wise.
The organism is sensitive t o heat. Usual pasteurization
temperatures will destory it. It w i l l not grow in solutions or mdia
containing 1 per cent o r more of salt, and there are s o w other t e s t s
which would indicate i t s s e n s i t i v i t y t o a l o t of things but not t o
irradiation. W
e have found it in one plant. Bruce said in my e a r
that everybody i s in l i n e but won't stay. I will refute that because
we found the organism in one plant in Oregon. But they found a plant
in Iowa t h a t has it, too, So on t h a t basis we w i l l say that the
organism my be universally found.
It has not been identified w i t h any known micrococcus. I
think a t first glance it looked t o the bacteriologist l i k e something
very common, but apparently it i s actually a newly discovered organismr
DR, NXVEN: We have had some experience with t h a t microorganism. The only place we have found it so f a r is i n the mails from
Oregon. However, we have not made an extensive search for it. Perhaps
here i n Chicago we are a l i t t l e t o o slow because we don't want t o admit
that it might be around here.
But here is t h a t star exception then t o the general rule, a
non-spore forming microorganism t h a t i s extremely sensitive t o ionizing
radiations, and we have confirred that a t least 2 million reps are
required f o r 99 per cent destruction of t h i s microorganism. W
e have
been playing around with it f o r quite some time. It i s a beautifully
red pigmnted microorganism and f o r a while we thought t h a t the red
pigment had something t o do with i t s radiation-resistance although
that i s not borne out on more extended research.
I might add, though, that another red pigmented micrococcus
t h a t we tested that we j u s t happned t o have i n the laboratory in our
stock culture checksalsoexhibited very high resistance t o ionizing
radiations but not t o such a great extent.
DR. SCEULTZ:
apparent non-toxicity.
You might mention the non-toxicity o r the
DR, NIVEN: Oh, well, that i s assumed. It goes without
saying that t h i s microorganism would not present any public health
hazard a t a l l ; so that that low temperature growing organism prefers
very much t o grow aerobically and i s very heat labile as Harold told
you. Morphologically it is a very unique microorganism, but we won't
bother t o go i n t o that.
Now I should l i k e t o c a l l f o r questions from the floor
directed t o these three speakers before you.
225.
MR. FEXNSPEIN: Mr. F’einstein from the USDA, but speaking as
an individual, not as a representative. Going back t o the first
speaker, you explained why the food would not be dangerous t o eat.
Unfortunately the humsn is injured by x-ray.
DR. MORGAN:
simile was based on residual a c t i v i t y , What
you have reference t o I think is the reason physicians stand by a lead
quard when they run x-ray machines. This I grant but t h i s is i n regard to i r r a d i a t i o n of the reproduction c e l l s and when yuu are doing
i r r a d i a t i o n of‘ meat, f o r instance, it is not a living tissue i n that
sense, So my simile was based on the f a c t that no radiation a c t i v i t y
was Induced I n t o the individual o r into the meat center. Does that
c l a r i f y it?
MR, F’EllUSTEIN: Vell, you say t h a t no radiation-activity is
induced i n t o the individual?
DR. MORGIW: That i s correct, but there is damage done t o
the human being and there I s damage done t o the acceptability of the
mat, if you want t o carry the simile f’urther.
MR. FEINSTEIN: I Just want t o bring out t h a t t h e r e is a
c e r t a i n amount of radiation that each one can take i n a lifetime.
That is not i n the sa- classification.
DR. NIVEN: W
e are ready f o r another question.
DR. D O m : I should l i k e t o say t o D r . Schultz that i n his
discussion r e l a t i v e t o the effect8 of i r r a d i a t i o n on c e r t a i n mat
products, som of the f i r s t material that m a presented indicated that
bacon, f o r example, i s not acceptable and yet on the acceptability
chart which you showed the reduction i n acceptability was about the
sa=
DR. SCHULTZ: W
e run i n t o those inconsistencies and it i e
impossible t o explain them. We examine our technics and a l l of t h a t
but we cannot explain them. I guess that is the best answer I can give.
.
DR NNEN : Vhile y m are on your f e e t , D r . Schultz, may I
ssk you a question? You presented some beautiful charts up here showing the comparative acceptability of irradiated versus non-irradiated
mats and Were was a s l i g h t reduction. W
e would a l s o get t h a t reduction with the conventional thermally processed canned meats, l e t ’ s
say. Would it be poselble w i t h a taste panel t o compare the three?
DR. SCHULZ: Yes, and I think we would be afraid t o put the
results on the ocreen because I have had experience w i t h canned m a t
flavors, too, if they were not very good. V we had had the finger
prt on us a t the time that canned meats first came i n t o the picture
that is being put on i r r a d i a t i o n I don’t think we would have canned
meata today. But we have no direct comparison, W
e have done it w i t h
some other products but I cannot report those to you.
DR. NIVEN:
or questions ?
Surely, you have some other points t o bring up
226.
DR. KRAYBIU: IIave any comparisons been made with stored
products after i r r a d i a t i o n with frozen meats, say, after a similar
period of storage on acceptability?
DR, S C W Z :
I should l i k e t o pass that along t o D r . Morgan.
e are currently doing some. I think I know
DR. MORGAN: W
w h a t you are driving at, D r . Kraybill, in trying t o compare the two.
Over a long period of storage, six months o r more, we have not been
too successful in keeping a frozen steak and ending up with sowthing
we can say is a control. Some times we have had t o go back t o f r e s h
cuts after that. I know of no work i n answer t o your question.
DR. KRAYBIU: It seems t o me that there might be a comparison with freezing f a c i l i t i e s . It i s about the best method we
have t o r e t a i n f r e s h characteristics of' f l a v o r and t h i s method would
have t o compte w i t h frozen storage.
DR, HENRICKSON: 1 am just going t o throw the question out.
Any one of t h e m can answer, Not much has been said about enzymatic
a c t i v i t i e s and the size dose t o destroy the enzymes. I wonder i f anyone would care t o comment on that. Are we completely disregarding it
now?
DR. SCHWEIGERT: The only thing that was indicated was the
one piece of work from D r , Doty's laboratory showing t h a t some 50 p r
cent of the proteolytic e n z p t i c a c t i v i t y as measured under the cond i t i o n s indicated was l o s t a t about 1.5 million rep. We have not done
a 8 y S t e 1 ~ a t i Cstudy of higher levels. Other enzyme systems, oxidative
i n nature, are being studied by D r . Green a t the University of Wisconsin
of which D r . Morgan may know the details.
From a practical standpoint, it would a p a r that the prot e o l y t i c enzyme already low i n meat i s not a major f a c t o r i n the
texture of the meat, as we indicated. There is some increased d r i p
loss, d r i p which would p s u m b l y be related somewhat t o the question.
And I also referred to the tyrosine crystals being fornred which presumably are the r e s u l t of proteolytic enzymatic a c t i v i t y on tyrosine
terminal substrates i n the mat. But other than that, I don't have
any further information t o add unless D r . Morgan would care t o comnent.
DR. NIVEN: I n general thoee enzymes which are of t h e active
sulfhydril group when irradiated i n pure form are r e l a t i v e l y sensitive
t o high energy irradiation, although they can be e f f e c t i v e l y protected with reducing agents, t h i s having been done, I believe, by Dr.
Barone and others.
:
'
' DR, E
Should you ever like t o try, j u s t f o r the fun
of it, t o develop a s t r a i n of microorganisms that would be r e s i s t a n t
t o radiation a t a high l e v e l ? Do you think there would be any possib i l i t y of it? To project it a l i t t l e further, if it should become
commercially feasible, can you foresee by any s t r e t c h of the imagina t i o n that there might be certain s t r a i n s that would develop a high
resistance t o high l e v e l i r r a d i a t i o n ?
227.
DR. NNEIP: We might have the Oregon micrococcus all over
the world then instead of Juat in Oregon and Iowa.
Yes, there is a p o s s l b i l i t y of perhaps selecting naturally
resistant m i c r o o ~ l s m e . I shall t r y t o anawer your question in part
and then ask anyone else t o add conmrents.
W
e have deliberately gone out t o attempt t o increase the
radiation resistance of microorganisms by repeatedly exposing them t o
sublethal doses. We do g e t within a short while a very modest incream i n radiation reeistance, mainly noted by an increase Fn la&
before we g e t the usual lcgrithmic order of death. However, t h i s can
be carried j u s t so far and no farther among the attempts we have made.
Of' course, we h a v e n l t t r l e d every microorganism in the world
remain p o s s i b i l i t i e s that that could be the case. However,
it is our opinion that that would not be a serious thing a t a l l ; that
is, the developmnt of radio-reelatant microorganisms that don't alreaay naturally occur.
and there
D r . Morgan, would you like t o add any more t o tbat?
DR. bDRGAN: I concur i n that. T h e e are in t h e open
l i t e r a t u r e four referecnes t o t h i s , one of which s t a t e s that they
were able t o induce resistance by p a s i n g it serially through radiations. There were three attempts t o reproduce t h i s and they were
unsuccessful
1 personally would concur w i t h Dr. Niven's feeling t h a t t h i s
is not a major i t e m , and if I m y s l i p in a question t o either you,
Charley, o r Dr. Schultz, what would be the r e l a t i v e re8i6tance or the
cromparison of resistance between t h i s organism and the organism
clostridium botulinum, a spore-forming organism?
DR. "EN: I don't recall precisely the radiation resistance
of clostridlumbotulinum. I am a f r a i d t h a t Bruce knows the answer t o
this and he is j u s t checking up. I am certain, however, t h a t it would
not be any mom radiation-resistant a t all. I am s p a k i n g of spores
of clostridum botulinum. They would not be any more r a d i a t i o n res i s t a n t and perhaps would not be as radiation-resistant as t h i s
micrococcus. W
e might t u r n a bad thing i n t o a good thing then and
use this organism as a s o r t of index microorganism f o r appropriate
l e v e l s of radiations subjected t o foods.
DR, SOULE: Does the i r r a d i a t i o n of f r e s h e a t s p o i l the
trichina larvae in the cysts cercoids found in meats from a public
health standpoint?
DR. RIVEN: Would you l i k e t o anmrer t h a t one? I don't
know anything about cyata cercoids, so you be prepared t o answer that
one. But with regard t o t r i c h i n a , very low l e v e l s of radiation in
the order of 15,000 rep, will s t e r i l i z e the female, not k i l l her but
s t e r i l i z e her BO that she is unable t o reproduce; t'nerefore, it
eliminates t h e danger of the raising of a new crop inside the body and
then migration of the smll w o r n out t o the muscle tissue. Now i s
t h i s an effective means of eliminating trichinosis i n our American
public? Some individuals state positively yes, However, i f you look
a t the outbreaks the important outbreaks, of trichinosis i n t h i s
country, they arise from individual family-fed hogs, primarily from
European inrmigrants that k i l l their family-garbage fed hogs and feed
t h e m t o neighbors and t h a t s o r t of thing, and then we have a localized
serious outbreak of trichinosis.
,
1 don*t foresee a family hog ever being irradiated t o prevent trichinosis. However, l e t ' s turn t h a t around. To pass inspection
by the MI, to make unheated pork safe, the mat industry does have t o
go through certain procedures that are not r e a l l y economical t o do;
that is, freezing schedules o r related procedures. This my be a more
convenient procedure t o s a t i s f y the M I regulatiom.
Now that cysta cercoid.
DR. WRGAN: T h a t will be along t h e
because it is not a true parasitic larva.
6-
IAne of thought,
DR. BRATZLER: D i d I hear wrongly t h a t with additive oxygen
you w i l l g e t no color degradation?
DR. SCHWEICERT: The question related t o t h e e f f e c t of
radiation on mat color, the color of lean. I stated t h a t when oxygen
impermeable casing o r sealed can8 are used there i s no grossly s i g n i f i e can detect, however, spectraphotometricant change i n the color. W
c a l l y that there is some of t h i s oxidation t o the green pigment.
Practically it is not important, but technically we can detect it.
When oxygen is present, such as with a regenerative celluloee casing, you get rapid oxidation, a metmyoglobin type of oxidation
which is, of course, undesirable practically as well as being able
readily t o d e t e c t it chemically. There is 6otne acidation even though
the gross color look6 good. I merely suggested that it i s possible
that a ferrylmyoglobin m y b e f o m d even when axygen is not present.
DR. BRATZLER:
To w h a t degree do you have t o remove oxygen?
DR. SCFIWEIGERT: I n our experience it is s u f f i c i e n t t o pack
t i g h t l y the mat i n an impermeable casing and seal it. The same
thing with a sealed can. That i s , f i l l a minirmun of head space and
seal. There w i l l be a sllght change at t h e surface of the head space
b u t no significant change anywhere e l s e . It is quite l i k e l y , of
cour~e,that the meat consunm the traces of oxygen l e f t in, i n either
case, so it may be quite an ineffectively low cxygen content even.
though no special precautions beyond those indicated were used.
DR. NIVEN: We are ready f o r another question t o be shot
a t these three experts.
CHAIRElAN P E E N : I have a question I should l i k e t o ask.
I would l i k e t o ask about the so-called t o x i c i t y work t h a t has been
229.
done a t Fitzsitnmons Hospital priolarily on thiamine and vitamin E and
the report on this work with relat on t o wats. I know it has been
mentioned briefly. I think I migh @fer it t o Dr. Schweigert.
t
DR. SCHMEIGERT: Tbat is Dr. Mrgm's k i t t y , A l .
DR. M O W : Quite a nut cam here. The work that was d m
kruman belngs waa not crf a c r i t i c a l enough mture t o determine
vita.mln deficiencies. F i r s t at a l l , a vitamin supplement was fed.
Secondly, the tests ran f o r a series o r 12 weeks for any given t e s t in
which the participants were on an irradiated d i e t for three weeks,
off f o r three weeke, on f o r three weeM end off. For a three-week
perfad I dcmrtbelieve you would presume t o 8ee a vitamin deficiency
in hwran beings and t o prevent t h i s possibility the supplement was
used.
using
In animals that a deficiency in vitamin E remlted in lack
of reproduction has been shown chemicaLly. Chemically vitamin C has
been shown t o be destroyed, but theae are eifher chemical or microbio. b & C & l tests,
DR. NI": I shauld l i k e to change the subJect a l i t t l e and
t o come back t o the microbiological aspects. A number of' years ago
B i l l Sulzbacher and one of' his associates plblished a paper describing a new species, microbacterium thermos factum that commonly occurs
in park sausage. I hope I am quoting you r i g h t , B i l l . Brhaps contributing t o the off-flavor d e v e l o p n t In aged pork sausage. When
we went into th5a radiation of pork we never encountered t h a t organism,
although we had not been looking f o r it. However, in fresh meats t h a t
have been Irradiated at low dose13 t o kill out all the pseudomonas,
the most common mlcroorganiam that survives and grows a t these holding
temperature8 of about 2 degree8 centigrade hapgens t o be the microbacterium thermos factum, It is j u s t moderately radiation-resiatant
compared t o other gram positive microorganisms. However, it is considerably more resistant than is pseudomonas t o spoilage microorganism.
Then turning t o cured meats we find that it is also one of
the more common surf'ace contaminants associated with general bacterial
growth on the surface of frankf'urtera and other cured meats.
Are there any other questions?
CHAIRMAN PEARSOH: I have one more I should l i k e t o address
t o you. I ahould like t o ask you to elucidate a l i t t l e more upon
your conbination treatment of radiation, tetracycline compound and
ascorbic acid.
DR. "EN: Our genera idea in getting into t h i s work was
that the tetracycline would complemen+J radiation treatment. The gram
negative organism are generally radistion-sensitive and the gram
positive organisms are relatively sensitive to tetracycline. So we
tested this out and they do seem t o complexmt one another. However,
immediately we began t o run Into yeasts a8 spoilage microorganisms
because of yeast berelatively resistant t o ionizing radiations
230.
and completely uneffected by the tetracycline; therefore, we turned t o
ascorbic acid as a mans of controlling the yeast and w i t h l e v e l s of
.1 per cent ascorbic acid up t o 10 parts per million of either one of
the two tetracyclines and a radiation dose of 100,000 rep. That combination, whether you conslder it ridiculous or not, w i l l e f f e c t i v e l y
from zero t o 2 degrees
preserve the mat a t 2 degree8 centigrade
centigrade f o r almost any period of time that you would want t o keep
it up t o 25 days l e t ' s say.
--
I should also l i k e t o repeat here, of a l l the preservative
methods that we know of, temperature control, SanAtation, ionizing
radiation, a n t i b i o t i c s , ascorbic acid, and the like, the two top ones
should be and are temperature control and good sanitation. All of'
these others ehould be cansidered supplementary t o those two.
\le w i l l turn the meeting back t o the Chairman.
reports.
CHAIRMAN PEARSON: Gentlemen, before we have any f u r t h e r
I think it i s time that we adjourned f o r a short recess.
(Recess. )
CHAIRMAN p F 3 s O M : Gentlemen, w i l l you please take your seats?
W
e wish t o get under way 60 that t h i s session can corn t o a n end.
There are perhaps som other people who have come i n since the
o r i g i n a l introductions. I know that Dr. Krayblll was here a few minutes
ago. Is D r . Kraybill present now? Dr. Kraybill, who i s i n the back there,
is a d i r e c t o r of the Ametican W a t I n s t i t u t e Foundation.
Is there anyone else who has not been introduced? If you have
not been introduced, if' you will stand up and introduce yourself we w i l l
appreciate it.
--
W
e have had B i l l Brown
is he in the r o o m a t t h e present time?
B i l l Brown, I don't believe you have been formally introduced. Will you
stand up and Introduce yourself'?
CHAIRMAN PEARSON: Thank you.
I have one announcement a t t h i s t i m e . Zane PaliEr has asked me
t o announce that abstract forma w i l l be available by contacting him immedia t e l y following t h i s meeting. So those of you who need abstract forms
please contact Zane following this meeting.
The first thing on the program is the short course angouncements
which w i l l be given by Dr. V e r n C a h i l l of Ohio State University.