WHEAT GERM OIL AS AN ANTIOXIDANT IN DAIRY PRODUCTS

P. It. TRACY AND W. A. HOSKISSON Department of Dairy Husbandry, University of Illinois, Urbana, Illinois

J. M. TRIMBLE Indiana Condensed Milk Company, Indianapolis, Indiana

The use of antioxidants in the manufacture of food stuffs containing oils and fats has been studied by a number of investigators. Greenbank and ttolm (13) found maleic acid, hydroquinone, and certain other phenolic compounds to have antioxidant properties. Chilson (3), Dahle and Palmer (10), and Greenbank (12) reported that the addition of 20 to 100 milligrams of pure vitamin C per liter of milk retarded or entirely prevented the de- velopment of an oxidized flavor in susceptible milk to which no copper had been added. Barnicoat and Palmer (2) studied the antioxidant properties of vitamins A, B, C, D, E, F, and nicotinic acid and found that only vitamins C and E were effective.

G~orgy and Tomarelli (14) found corn, oats, wheat, rice, bran extract and Avenex to have high antioxidant properties. Of the known B vita- mins, p-aminobenzoic acid was the only one they found to be significantly antioxygenic.

Tracy and Corbett (24) have shown that the addition of 0.1 to 0.25 per cent sodium citrate retarded the development of oxidized flavor in milk. Anderson (1) found that a pancreatic extract when added to milk protected' it from developing an oxidized flavor.

The work of Dahle and Josephson (6, 7, 8), Corbett and Tracy (4), Koenig (17), Maack and Tracy (18), Muel~er and Mack (20), and Peters and Musher (23) has shown that the use of oat flour or a water extract from the oat flour prevented or retarded the oxidized flavor development in milk, ice cream, frozen cream, and butter. Mueller and Mack (21) in studying the antioxidative properties of several cereal flours found that whole oat flour, finely milled oat flour, and corn flour were of equal value but that wheat, barley, rye, and rice flours had but little antioxidative effect.

Corbett and Tracy (5) repor ted the effectiveness of tyrosine, tyrosine esters and the water extract of certain cereal flours as antioxidants in dairy products. Hollender and Tracy (15) experimented with the use of certain antioxidants in powdered whole milk. Among the antioxidants they found most effective were gum guaiac, hydroquinone, ascorbic acid and sodium citrate.

The studies of McFarlane of MacDonald College, Quebec, as reported by correspondence with the. author, have shown wheat germ oil to have antioxi-

Received for publication September 13, 1943. 311

312 P. YI. TRACY, W. A. HOSKISSON AND G. M. TRIMBLE

dant properties when added to certain animal and vegetable fats and oils used in the manufacture of shortening. The results were measured by means of the Swift 's stability test. This investigator also found wheat germ oil par t icular ly when fortified with citric acid retarded oxidative changes in powdered whole milk as measured by the peroxide value. Mc- Far lane finds wheat germ oil to be more effective than either hydroquinone or gum guaiac.

Realizing the importance of copper contamination in the development of the oxidized flavor, modern dairies use stainless steel in the construction of their equipment wherever possible. In spite of this and other precau- tions that are taken to retain a normal flavor in the stored products, the indust ry still recognizes oxidized flavor development in dairy products as a serious problem. This is par t icular ly true in the case of powdered whole milk, much of which is likely to be stored for some time at high temperatures (70 ° - 1 2 5 ° F.) before consumption. Because of the important par t tha t powdered whole milk plays in the dietary of our armed forces as well as that of the civilian population of our allies, it seems that serious considera- tion should be given to the application of all known methods that will lengthen the shelf life of the product. Since any oxidation process to which the fa t is subjected is likely to result in the destruction of certain of the vitamins contained in milk (Pavcek and Shull (22)) , it would also seem de- sirable f rom a nutr i t ional point of view to add harmless antioxidants to those dairy products that are to be stored for some time before consumption.

EXPERIMENTAL DATA

The use of solvent extracted wheat germ oil as an antioxidant in milk, frozen cream, and powdered whole milk made by both the spray and roller methods has been studied. Representat ive results are given.

Use of wheat germ oil in pasteurized milk. An at tempt was first made to determine to what extent wheat germ oil would re tard the development of an oxidized flavor in unhomogenized whole milk. The wheat germ oil was added at three levels, 0.1, 0.2, and 0.3 per cent of the weight of the fat. The oil was mixed with the cold milk before pasteurization (143.5 ° F., 30 rain.). The milk used was produced in late spring (May). To a port ion of the milk, copper was added at the rate of 1 ppm. and 2 ppm. Af te r 24 hours storage at 40 ° F. the samples were judged for flavor. The results are given in table 1.

A definite re tardat ion of oxidation was evident in those samples contain- ing the wheat germ oil and to which copper had been added. No par t icular benefits were obtained at levels higher than 0.2 per cent of the wheat germ oil. The best flavor was in the "samples containing no added copper to which 0.1 per cent of wheat germ oil was added. At the 0.2 and 0.3 per cent level enough of the wheat germ oil flavor was notfceable to cause the milk to score less than the control.

W H E A T GERM OIL 313

TABLE 1 Wheat germ oil (A ) as an antioxidant in whole milk

Sample

Control ..................................................................................... Control + 0.1% W.G.O ........................................... Control + 0.2% W.G.O ........................................... Control+ 0.3% W.G.O ............................................ Control + 1 ppm. Cu ................................................ Control + 1 ppm. Cu + .1% W.G.O ............. Control + 1 ppm. Cu + .2% W.G.O ............. Con t ro l+ l ppm. Cu+.3% W.G.O ............. Control + 2 ppm. Cu ................................................ Control + 2 ppm. Cu + .2% W.@.O ............. Control + 2 ppm. Cu + .3% W.G.O .............

Flavor score r af ter 3 days ~ storage at 40 ° F.

Score

36 37 35 34 29 31 32 32 28 31 31

Criticism

S1. bitter S1. oil flavor S1. oil flavor S1. oil flavor Oxidized Oxidized Oxidized Oxidized Oxidized Oxidized Oxidized

r Basis of 45 as perfect score.

I n o t h e r e x p e r i m e n t s i t w a s f o u n d t h a t a t l eve l s h i g h e r t h a n 0.3 p e r c e n t o f t h e w e i g h t o f t h e f a t t h e w h e a t g e r m oil f l av o r w a s s u f f i c i e n t l y d e t e c t a b l e i n t h e m i l k to be o b j e c t i o n a b l e e v e n w h e n c o p p e r w a s p r e s e n t .

U s e o f w h e a t g e r m oi l i n f r o z e n c r e a m . To s t u d y t h e e f f ec t o f w h e a t g e r m oil i n - r e t a r d i n g t h e d e v e l o p m e n t of o x i d i z e d f l av o r i n f r o z e n c r e a m , c r e a m c o n t a i n i n g 50 p e r c e n t f a t w a s m i x e d w i t h su f f i c i en t s u c r o s e to p r o d u c e a s u g a r c o n t e n t o f 12 p e r cen t . H a l f o f t h i s s w e e t e n e d c r e a m w a s p a s t e u r - . i z e d a t 160 ° F . f o r 30 m i n u t e s a n d t h e o t h e r h a l f a t 170 ° F . f o r 15 m i n u t e s . To h a l f o f e a c h o f t h e t w o lo t s 0.5 p p m . o f c o p p e r w a s a d d e d . To a p o r t i o n

TABLE 2 Wheat germ oil (A ) as an antioxidant in frozen cream

Sample ~ Degree of oxidized flavor af ter

4 too. ] 6 too. ] 9 mo. I 13 too.

A--Cream pasteurized at 160 ° F. for 30 minutes

1A - Control ........................... 1B - Control .......................... 2A + 0.2% W.G.O ............. 2B + 0.2% W.G.O ............. 3A + 0.3 % W.G.O ............. 3B + 0.3% W.G.O .............

m

+ 6+

2+

½+

2½+ 7+

4+

3+

B--Cream pasteurized at 170 ° F. for 15 minutes

1 A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2A + 0.2% W.G.O ............. 2B + 0.2% W.G.O .............. 3A + 0.3% W.G.O ............. 3B + 0.3 % W.G.O .............

w

-4-

½-

5+

2½+

2

* A = no copper added. B = ½ ppm. Cu added.

314 P. H. TRACY, W. A. HOSKI~SON AND G. M. TRINIBLE

of each of the four lots wheat germ oil at two levels (0.2 and 0.3 per cent of the weight of the fa t ) was added. The samples were stored in quar t Seal- r igh t containers in an ice cream hardening room and were judged every 3 to 4 months over a period of about 13 months. The results given in table 2 show that wheat germ oil caused a definite re tardat ion of the oxidation of b u t t e r f a t when copper was present. I t is also evident that heating cream above 160 ° F. (170 ° F.) dur ing pasteurizat ion also aided in re ta rd ing oxi- dation. This confirms the results of Trou t and Scheid (25) as well as Dahle, Lawhorn, and B a rnha r t (9), and MeFar land and Burgwald (19). The beneficial effect of the higher heat t rea tment has been found by Gould and Sommer (11) and Josephson and Doan (16) to be due to the p~'oduction of su l fhydry l s which are reducing substances. Best results were obtained when both the wheat germ oil and the high heat t rea tment were used. The super ior effect of the combination was noticeable, however, only a f te r nine months of storage.

Wheat germ oil as an antioxidant in powdered whole milk. Pre l iminary 'studies having established the ant ioxidant propert ies of wheat germ oil in milk and cream it was desired to determine to what extent the substance would funct ion in powdered whole milk. A complete unders tanding of the na ture of the ingredient contained in wheat germ oil tha t is res~)onsible for the ant ioxidant propert ies is lacking. I t is thought, however, that the tocopherols and phosphatides that are present are contr ibuting agents. Since the s tar t of this s tudy it has been found that the potency of wheat ge rm oil can be increased by the addit ion of citric acid. The use of sodium citrate as an ant ioxidant in milk has been previously studied by Tracy and Corbet t (24). Three different oils 1 were used, fo rmula A - - r e g u l a r wheat g e r m oil, formula C - - r e g u l a r wheat germ oil plus 2 per cent citric acid, and fo rmula D---regular wheat germ oil plus 5 per cent citric acid and 30 per (cent soybean lecithin.

Procedure followed in preparing milk powder samples. Powdered whole mi lk p repared by both the vacuum roll and spray processes was used to test the ant ioxidant propert ies of the wheat germ oil. The milk used for the rol ler d ry ing was produced by the Univers i ty herd, while tha t sp ray dried was received at a commercial condensery. An a t tempt was made to handle the milk in such a manner as to minimize copper contamination.

The powder was packed in number 2 cans in the case of the roller process a n d number 1 cans in the case of the sp ray drier. P a p e r containers were .used in one of the experiments with spray powder (samples 5019 and 5020-- .~able 4). One set of the spray powders was packed plain and one set was packed in nitrogen.

The milk used to make the powder manufac tu red by the roller method ( table 3) was preheated at 170 ° F. for 30 minutes and concentrated to ap-

1 The wheat germ oil used in this s tudy was solvent extracted and was supplied by the "VioBin Corporation, Monticello, Illinois.

WHEAT GERM OIL 315

p r o x i m a t e l y 38 p e r cent t o t a l solids. W h e a t ge rm o i l - - f o r m u l a s A, C, a n d D, were a d d e d to the condensed mi lk a t the r a t e of 0.2 p e r cent of the we igh t of the f a t in t r i a l 1 a n d 0.1 p e r cent in t r i a l 2.

I n the case of the s p r a y d r i e d samples 4924-31 a n d 4952-59 ( tab le 4) the whea t g e r m oil was a d d e d to sk im mi lk t h a t h a d been hea ted to 170 ° F . a n d homogen ized a t 2,500 p o u n d s p ressure . This emuls ion was t hen a d d e d to the r a w mi lk a n d he ld over n ight . The mi lk was p r e h e a t e d a t 180 ° F . fo r 7 minutes , cooled to 145 ° F . a n d then condensed. I t was homogenized a t 3,000 p o u n d s at 130 ° F . The d r y i n g was t hen done 24 hour s l a t e r . The n i t r o g e n - p a c k e d p o w d e r was f irst sub j ec t ed to a v a c u u m of 2 mm. Then C02 was i n t r o d u c e d to 10 p o u n d s p r e s s u r e fo r 10 minutes , t hen a v a c u u m of 2 ram. was d r awn , then n i t r o g e n was i n t r o d u c e d to a p r e s s u r e of 5 p o u n d s fo r I 0 minu tes .

TABLE 3 Use of Wheat germ oil in roller (vacuum) process powdered whole milk

Sample

Control ............................................................... Control+0.2% W.G.O. A ........... Control+ 0.2% W.G.O. C ........... Control+ 0.2% W.G.O. D .......... Control .............................................................. Control+0.1% W.G.O. A ............ Control+ 0.1% W.G.O. C ............ Control+0.1% W.G.O. D ...........

Trial

1 1 1 2~ 2 2 2

Fresh

38 38 38 38 38 38 38 38

Flavor score

3 /nO.

29 33 34 34 37 36 37 37

6 too.

29 32 32 33 33 35 35 36

Prepared Nov., 1942. f Prepared Feb., 1943.

S a m p l e s 4887-90 a n d 5017-22 were p r e p a r e d in the same m a n n e r as those above excep t t ha t n i t r o g e n on ly was used in the case of the g a s - t r e a t e d lot.

The on ly v a r i a t i o n in the p r o c e d u r e fo l lowed in the p r e p a r a t i o n of samples 4985-88 f r o m t h a t fo l lowed in the p r e p a r a t i o n of s amp le 4887-90 was t h e m e t h o d of a d d i n g the whea t g e r m oil. F o r m u l a D was used in a l l samples . I n the case of samples 4985 a n d 4986 the oil was homogen ized in sk im mi lk a n d a d d e d to the whole mi lk be fore condens ing as o u t l i n e d above. I n the ease of s amples 4987 a n d 4988 the oil was m i x e d w i th the condensed mi lk j u s t be fo re s p r a y i n g .

The d r i e d mi lk s amples were j u d g e d when f resh a n d eve ry 2 to 3 m o n t h s d u r i n g s to rage a t room t e m p e r a t u r e . I n t ab le 4 on ly the f inal f lavor scores a r e r e p o r t e d . The f lavor of the r e c o n s t i t u t e d samples was 38-39 a t the b e g i n n i n g of the e x p e r i m e n t a n d was c r i t i c i zed as be ing cooked. Subse- quen t scor ings were m a d e on the bas is of the degree of ox id ized f lavor de- veloped. The samples were r e c o n s t i t u t e d b y m i x i n g 30 g r a m s of the p o w d e r wi th 200 ml. of t a p w a t e r us ing an e lec t r ic m a l t e d mi lk machine . The sample cans were opened i m m e d i a t e l y before the mi lk was r econs t i t u t ed .

TABLE 4 Use Of wheat germ oil in spray dried whole milk powder

Sample

l Date No. made

4924 11/24/42 4925 11/24/42 4926 11/24/42 4927 11/24/42 4928 11/24/42 4929 11/24/42 4930 11/24/42 4931 11/24/42 4952 12/ 2/43 4953 12/ 2/43 4954 12/ 2/43 4955 12/ 2/43 4956 12/ 2/43 4957 12/ 2/43 4958 12/ 2/43 4959 ] 2 / 2/43 4887 11/10/42 4888 11/10/42 4889 11/10/42 4890 11/10/42 4985 12/12/42 4986 12/12/42 4987 12/12/42 4988 12/12/42 5017 1/13/43 5018 1/13/43 5019 1/13/43 5020 1/13/43 5021 1/13/43 5022 1/13/43

Preheat temp. before condensing

180 ° )~. 7 min., cooled to 145 ° F.

180 ° F. 5 min.

170 ° F. 30 rain.

Cone. of solids

180 ° 5 min., cooled to 145

170 ° F. 30 min.

Spray temp.

Type of

pack*

Sol. in- dex

H~O Wheat germ

oil used

% 11.42 F. 38.26 T.S. 11.19 F. 37.94 T.S. ]0.91 F. 36.82 T.S. 11.01 F. 37.41 T.S. 11.44 F. 38.64 T.S. 11.28 F. 36.93 T.S. 11.05 F. 37.47 T.S. 10.98 F. 36.50 T.S. 11.59 F. 37.60 T.S. 11.47 F. 37.53 T.S. 10.90 F. 38.56 T.S. 10.87 F. 38.35 T.S. 10.06 F. 36.14 T.S.

10.40 Y. 37.65 T.S.

130 ] 30 330 130 130 130 130

65 65 65 65 65 65

Spray pres- sure

Spray cham-

ber temp.

Temp. of

powder when

packed

P N P N P N P N P N P N P N P N P N P N P N P N P- t in N P-paper P - t l n N P-paper

0.1 0.1 0.1 0.1 0.15 0.15 0.20 0.20 0.10 0.10 0.10 0.10 0.10 0.10

2.1 2.1 2.3 2.3 2.0 2.0 2.0 2.0 1.9 1.9 1.95 1.95 1.60 1.6 1.4 1.4 2.0 2.0 2.0 2.0 2.1 2.1 2.8 2.8 1.8 1.8 1.8 2.0 2.0 2.0

None None 0.1% A 0.1% A 0.1% C 0.1% C 0.1% D 0.1% D None None 0.05% A 0.05% A O.O5% C 0.05% C 0.05% D 0.05% D None None 0.1% A 0.1% A 0.1% O 0.1% D 0.1% D 0.1% D None None None o.1% o.1% o.1%

Gas con- tent t

C0: [ 0~

3.64 4.24

Flavor s c o r e

Aug. 7, 1943

30 32 31 33 31 33 31½ 34 29 31 30 31½ 30 31½ 30 32 23 30 25 3O 33 35 34 36 32 35 33 34 36 36

* P = plain. N = gas.

t~ Lots 5018 and 5021 were packed with water pffmped nitrogen, while the other lots were packed with oil pumped nitrogen.

TABLE 4

Use of wheat germ oit in spray dried whole milTe powder

Sample Spray Temp. Wheat Gas con- FlavorPreheat temp. Cone. of Spray Spray cham- of Type Sol. germ tentt score

Ibefore condensing solids temp. pres- bel' powder of in- H2O oil Aug. 7,

No. Date sure temp. when pack* dex used CO2 I 1943made packed O2

% OF. lbs. of. of. ee.

I4924 11/24/42 180 0 P. 7 min., 11.42 F. 115 2,000 170 106 P 0.1 2.1 None 304925 11/24/42 cooled to 145° E. 38.26 T.S. 115 2,000 170 106 N 0.1 2.1 None 3.64 I 4.24 324926 11/24/42 11.19 F. 115 2,100 170 106 P 0.1 2.3 0.1% A 314927 11/24/42 37.94 T.S. 115 2,100 170 106 N 0.1 2.3 0.1% A 3.81 3.5 334928 11/24/42 ]0.91 P. 115 2,300 170 102 P 0.1 2.0 0.1% C 314929 11/24/42 36.82 T.S. 115 2,300 170 102 N 0.1 2.0 0.1% C 4.17 3.15 334930 11/24/42 I 11.01 F. 115 2,400 170 102 P 0.1 2.0 0.1% D 3]f4931 11/24/42 37.41 T.S. 115 2,400 170 102 N 0.1 2.0 0.1% D 3.21 3.75 34

4952 12/ 2/43 180° P. 5 min. 11.44 F. 115 , 1,800 170 ]04 P 0.1 1.9 None 294953 12/ 2/43 38.64 T.S. 115. 1,800 170 104 N 0.1 1.9 None 3.]6 3.99 314954 12/ 2/43 11.28 F. 115 1,800 170 106 P 0.2 1.95 0.05% A 304955 12/ 2/43 36.93 T.S. 115 ],800 170 106 N 0.2 1.9fi 0.05% A 4.09 3.68 3li4956 12/ 2/43 11.05 P. 115 1,800 170 106 P 0.1 1.6(1 0.05% C 304957 12/ 2/43 37.47 T.S. 115 1,800 170 106 N 0.1 1.6 0.05% C 3.25 3.65 3li4958 12/ 2/43 10.98 P. 115 2,400 170 107 P 0.1 1.4 0.05% D 304959 12/ 2/43 36.50 T.S. 115 2,400 170 ]07 N 0.1 1.4 0.05% D 2.76 3.54 32

4887 11/10/42 30I

170° P. min. I 11.59 P. ]30 2,500 ]65 ]22 P 0.1 2.0 None 234888 11/10/42 37.60 T.S. 130 2,500 165 ]22 N 0.1 2.0 None 0.25 3.54 304889 11/10/42 11.47 }<'. ]30 2,400 170 130 P 0.1 2.0 0.1% A 254890 11/10/42 37.53 T.S. 130 2,400 170 130 N 0.1 2.0 . 0.1% A 0.20 3.20 30

4985 12/12/42 180° 5 lnin., 10.90 F. 130 2,500 170 90 P 0.15 2.1 0.1% D 334986 12/12/42 cooled to 145 38.56 T.S. 130 2,500 170 90 N 0.15 2.1 0.1% D 3.09 4.05 354987 12/12/42 10.87 F. 130 2,500 170 90 P 0.20 2.8 0.1% D 344988 12/12/42 38.35 T.S. 130 2,500 170 90 N 0.20 2.8 0.1% D 3.66 4.42 36

5017 1/13/43 170° F. 30 min. 10.06 F. 65 800 180 M P-tin 0.10 1.8 None 325018 1/13/43 36.14 'l'.R. 65 800 180 64 N 0.10 1.8 None 0.28 1.45 355019 1/13/43 65 800 180 64 P-paper 0.10 1.8 None 33[i020 1/13/43 10.40 F. 65 800 180 63 P-tin 0.10 2.0 0.1% 345021 1/13/43 37.65 T.S. 65 800 180 63 N 0.10 2.0 0.1% 0.22 1.75 365022 1/13/43 65 800 180 63 P-paper 0.10 2.0 0.1% 36

* P = plain.N=gas.

t· Lots 5018 and 5021 were packed with water pumped nitrogen, while the other lots were packed with oil pumped nitrogen.

WHEAT GERM OIL 317

Other details regarding the procedure followed in making the spray powders are given in table 4.

Milk powder data. The data obtained on the effect of wheat germ oil upon the keeping quality of powdered whole milk are given in tables 3 and 4. It is evident that wheat germ oil retarded the oxidation of butter fat but did not prevent its occurrence. The oil,treated with citric acid was slightly superior to the untreated oil. Formula D gave results somewhat better than those obtained with Formula C in most cases. The method of adding the oil was of no particular importance. The oil functioned in both plain and nitrogen-packed powder: I t should be pointed out that neither the use of wheat germ oil or gas packing prevented oxidation from taking place though packing in the presence of an inert gas proved to be somewhat more bene- ficial than the use of the wheat germ oil without gassing. Best results were obtained with a combination of the two, however.

SUMI~ARY AND CONCLUSIONS

The ability of wheat germ oil to prevent oxidation has been determined in fluid milk, frozen cream and powdered whole milk made by both the vacuum roll and spray processes. The amount of wheat germ oil needed for best results is approximately 0.2 per cent of the weight of the fat. At higher levels (0.3 per cent) the flavor of the oil is sometimes detectable. Wheat germ oil reinforced with citric acid was found to be more effective in retarding oxidation in milk powder than regular oil. While wheat germ oil is not as effective as gas packing with nitrogen in preventing the develop- ment of the oxidized flavor in powdered milk, a combination of the two will prolong the shelf life of the powder more than either one alone will accomplish.

REFERENCES

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(3) CHILSON, W. H. Wha t Causes Most Common Off-flavors of Market Milk? Milk P lan t Monthly, 24: 24-28, 30-33. 1935.

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318 P. H. TRACY~ W. A. HOSKISSON AND G. 1~. TRIMBLE

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