Mutagens in Cooked Food - ACS Symposium Series (ACS Publications)

9 Mutagens in Cooked Food L. F. BJELDANES Department of Nutritional Sciences, University of California, Berkeley, CA 94720 J. S. FELTON and F. T. HATCH

Downloaded by TUFTS UNIV on July 15, 2016 | http://pubs.acs.org Publication Date: October 25, 1983 | doi: 10.1021/bk-1983-0234.ch009

Biomedical and Environmental Research Program, Lawrence Livermore Laboratory, University of California, Livermore, CA 94550 With the development of simple and rapid methods for detecting agents which modify genetic material of cells (i.e., Ames bacterial assay) has come the realization that mutagens are widespread in our environment (1). The attention of several research groups has turned toward examining mutagenic activity of foods. As a result of this extensive research effort the occurrence of mutagenic substances in certain heated foods and food components is now well documented. Proteins and several amino acids yield highly mutagenic substances when pyrolyzed at temperatures above 300ºC (2-4). Similar temperatures were reported to be necessary to generate appreciable mutagenicity in pyrolyzed food samples (5). Under pyrolytic conditions, carbohydrate and lipid components and foods rich in them tend to exhibit less mutagenic activity than samples rich in proteins or amino acids. Evidence compiled by several research groups indicates that mutagenic activity is also induced in certain foods cooked under conditions less severe than required for pyrolysis (6-9). In these studies mutagenic activity is detected in fried and broiled protein-rich food (beef), and at a higher level than in cooked carbohydrate-rich food (10). Broiled fish samples also contain mutagens(11). In addition, extended boiling of beef stock results in mutagen formation (6,8). Reviewed herein are the results of our work to determine the effects of food type and cooking conditions on mutagenicity of cooked protein-rich foods. Results of our efforts to isolate and identify mutagens from fried beef are also described. Mutagenicity of cooked protein-rich foods Published information on dietary practices in the U.S. was examined in order to establish priorities for mutagenicity testing of cooked foods. Analysis of diet surveys conducted by the U.S.D.A. (1964-66) and U.S. Department of H.R.W. (1971-75) 0097 -6156/83/0234-0149$06.00/0 © 1983 American Chemical Society

Finley and Schwass; Xenobiotics in Foods and Feeds ACS Symposium Series; American Chemical Society: Washington, DC, 1983.


150

XENOBIOTICS

IN F O O D S A N D F E E D S

provided a l i s t i n g of the major sources of dietary protein i n the U.S. (Table 1) based on per capita consumption (12). Milk was clearly the most significant dietary source of protein and beef was the most significant meat source. A l l of the foods tested were submitted to various heat treatments (13,14). The i n i t i a l survey included two sets of cooking times and temperatures for each food. One set approximated common practice i n the United States, and the other u t i l i z e d more severe conditions that generally resulted i n a very well done, though not burned, sample. In seme cases, when significant mutagenic a c t i v i t y was detected i n the i n i t i a l screening, a more detailed investigation of the dependence of mutagenicity on cooking time and temperature was carried out. Except i n cases i n which mixtures of food were examined, no seasonings or other additives were used. When normal procedures required cooking o i l , corn o i l was used. For the i n i t i a l surveys most samples were cooked i n stainless steel pans. Broiled samples were prepared i n ceramic cooking dishes. The more detailed investigations of frying œnditions were conducted en an e l e c t r i c a l l y heated stainless steel griddle. Temperatures given i n the tables were measured i n each experiment with the empty utensil, on top of a household e l e c t r i c range or e l e c t r i c griddle, at the heat control setting that was used i n cooking the food sample. Special heating conditions were used for certain foods. Eggs were f r i e d i n the form of patties i n addition to the more conventional forms. Egg patties were prepared by heating egg mixture or egg fraction for 1 hour at 95°C i n a p e t r i plate, a procedure that by i t s e l f causes no mutagen to form. Milk samples were heated to vigorous reflux for periods up to 240 min. or were reduced i n volume by 50% and 25% by vigorous boiling. Cooked samples were deboned i f necessary and when an obviously browned outer portion or crust was present on the cooked food, this material was separated from the inner portion and extracted for bioassay. Results of bioassays of the inner portions of foods were uniformly negative except for small amounts of mutagenic a c t i v i t y that appeared when samples were fried at the highest temperatures. Cooked foods were homogenized and extracted with acetone as previously described (9). The organic base fraction, which contained a l l of the detectable mutagens, was dissolved i n DMSO and assayed with Salmonella tester strains TA 1538 or TA 98 (15). Aroclor-induced rat l i v e r S-9 fraction was used for metabolic activation of mutagens. The number of revertants induced per 100 gram wet weight equivalents (100 gE), i . e . , per 100 grams of uncooked food, was extrapolated from the linear portions of doseresponse curves. In this i n i t i a l survey, mutagenicity i n cooked protein-rich foods was found to be dependent on the type of food and the



11.7 4.5 4.5 4.1 3.7 *1.7 2.5 *0.7 2.5 1.8

8.9 4.2 4.0 3.3 3.1 1.6 1.4 1.3 1.0 0.9

Whole milk

Ground beef

Beef steak

White bread

Pork chops

Fried chicken

Beef, braised or pot roasted

Ham

Roast beef

* Rank order for USDA and HANES data are i d e n t i c a l except for these 2 food items.

Eggs

USDA

from food item

per capita mean d a i l y protein intake (g)

Ten highest ranking food items from the two data sets

HANES

Table 1.



152

X E N O B I O T I C S IN F O O D S A N D

FEEDS

degree of heating. Whereas a l l of the foods tested developed mutagenic a c t i v i t y under some cooking conditions, only the most severe conditions consistently produced activity i n milk, cheese, tofu,beans, and organ meats (Table 2). Extensive discoloration or charring was generally obvious i n the mutagenic milk, cheese and tofu samples. Nonmutagenic samples of these later foods were not markedly discolored. Data presented i n Tables 2-4 shew results of more severe heat treatments. Mutagenic activity was generally reduced i n samples treated under milder conditions than indicated i n the tables. bione of the bean samples was burned or considered inedible. Several samples were weakly mutagenic and one sample (baked pinto beans) contained moderate mutagenic a c t i v i t y (3,650 revertants/100 gE). Many of the organ meat samples shewed weak activity, with sauteed kidney and brain samples being the most active ( 900 revertants/100 gE ). None of the organ meat preparations was charred. The griddle-fried and the oven-broiled samples of rock cod showed moderate mutagenic activity (1,300-2,000 revertants/100 gE) (Table 3). The more extensively fried trout, salmon, and red snapper yielded 2,500-3,100 revertants/100 gE, while halibut yielded about 1,100 revertants/100 gE. The remainder of the rock cod samples, and the sole, shrimp, and batter-fried seafood from a commercial galley exhibited negligible or small amounts of mutagenic activity. These results are comparable to results of Krone and Iwaoka (16). Preparation of chicken under several relatively moderate conditions produced lew or moderate levels of mutagenic a c t i v i t y (Figure 1). Moderate mutagenic a c t i v i t y (1,000-4,000 revertants/100 gE) was detected i n very well done to p a r t i a l l y charred chicken samples. Undetectable or weak (10,000 revertants/lOOgE) were


Finley and Schwass; Xenobiotics in Foods and Feeds ACS Symposium Series; American Chemical Society: Washington, DC, 1983. Boiling 25% boildown Baked Fried Baked Fried Boiling Boiling B o i l i n g then B o i l i n g then B o i l i n g then B o i l i n g then

Whole milk Whole milk Sharp cheddar cheese Sharp cheddar cheese American cheese American cheese Pinto bean Kidney bean Pinto bean Kidney bean Pinto bean Pinto bean f r y i n g (no o i l ) f r y i n g (no o i l ) baking baking

Cooking method

60 65 305 20 5 78 90 4 10 60 120

Time (min)

Mutagenic a c t i v i t y i n food samples under d i f f e r e n t

Sample

Table 2.

NSt 440 63 NS 360 94 75 140 NS 380 3650 460

TA1538 revertants per lOOgE*

Continued on next page

100 100 232 375 232 375 100 100 450 450 176 176

Temperature (°C)

cooking c o n d i t i o n s


X E N O B I O T I C S IN F O O D S A N D F E E D S

154

I

Ο O CO Ο Ο Ο

^ m ο Η Tt

^· Η

Η

η (Ν

O LO CM 00

Ο Ο Ο CM tO C»

ι-Η

to «-π tO

oc

cd ·4-> ι—I 4-> ·Η Cd 0 0 > X > 0 0 4-> 0

g

S

Ρ 0

cd

Χ


vOvOOOCMOtOOLOCJïOOOO r^r^LOLOvOrHvOLOr^^l-LOLOOvO

o

rH

·-

PS O

0

«4-!

• υ

Ρ

tO LO CM

CM CM «P cd

cd

ν—ι

X

X 0 o o

LO

OOOOOOLO^tLOCMLOOt^CMLOCM VÛCM r H \Q tO vD f-H t—l

σ>

. to

vO.X + l-M

0 t/> 0

υ ps 0 Ό ·Η

MH

o

ρ

Ό PS o o 0 (Λ

4->

ri

ΙΛ

μ •H O +•> PS

O X PS ç l , cd cd 0

CO

o o CH

bû bû Dû bû

0

ρ ρ ρ ρ

•3 3

o o υ

£££

ΜΗ ΜΗ Ρ 0 C C (D 0 +J +J bû bû Ρ +-> Ρ 3

ο

co co

OQ

cd cd

PS 0

r—I

cd

>

•H

or 0

S

X

& to

CM Q)

H

EH

MH MH

C Pj cd p! cd D d d)

MH CH 4-J D 0 μ μ ρ Ό rt rt ·Η ·Η Ο ·Η 0 0

4->

c

ex m

«H

0 0 0 0 0 0 X X X

cd •H 4-> £ cd o §X * H X (Λ (Λ Ph 3 cd O +J 0 cd

+->

χ

bû 0

0

(D Ό •H

Mutagens in Cooked Food - ACS Symposium Series (ACS Publications)

Recommend Documents