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Iron Fortification of Process Cheddar Cheese1
DAIRY FOODS Iron Fortification of Process Cheddar Cheese' DEJlA ZHANG and ARTHUR W. MAHONEY Department of Nutrition and Food Sciences Utah State University
Logan 8 4 3 2 2 4 m ABSTRACT
countries (10). The Second National Health and Nutrition Examination S w e y estimated that the prevalence of iron deficiency anemia in the US is at 5.7% for 1- to 2 yr-old infants, 5.9% for 15- to 17-yr-old girls, 4.5% for young women, and 4.8% for elderly men (4). Although dairy products are the richest and primary sources of dietary Ca, the mineral needed to prevent osteoporosis and high blood pressure, they contribute little dietary Fe (7). Fortifying dairy products with Fe would enhance their nutritional value. Cheddar cheese has been successfully fortified with Fe in previous studies (13, 14, 15). The objective of this study was to determine the effect of Fe fortification on the quality of process Cheddar cheese.
Dairy products Contribute high quality protein, calcium, and other nutrients but no Fe to human diets. In this study, we determined whether Fe fortification affected the quality of process Chedda~ cheese fortified with Fecasein, Fe-whey protein, or FeCl3. An unfortified process cheese served as a control. Iron concentrations in the fortified cheeses were about 40 m a g , an Fe density of 10 mg/ loo0 kcal; and unfortified cheese contained 1 to 2 mg h a g . The quality of the pracess cheese was determined by thiobarbituric acid assay and taste panel evaluation. Thiobarbituric acid numbers were slightly lower in the unfortified cheese (P = .049). A taste panel of experts did not detect any differences in oxidized off-flavor or cheese flavor among the cheeses that have been stored as long as 3 mo (B.05).A panel of 94 lay subjects gave similar hedonic scores to the flavor, texture, and overall quality of the Fe-fortified and unfortified cheeses (B.05).Results indicate that it is possible to produce good quality, Fe-foltified process Cheddar cheese. (Key words: iron fortification, iron-& protein complexes, process Cheddar cheese)
MATERIALS AND METHODS Experlrnental Design
A batch of four process Chedda~cheeses, no Fe added (control), fortified with Fe-casein, Fewhey protein or FeCl3 were made in four trials (4 x 4). Cheese quality was determined chemically by thiobarbituric acid W A ) assay and organoleptically by food scientists 10 d to 3 mo after the cheeses were manufactured. Using a hedonic rating scale, an open taste panel of 94 lay people evaluated the flavor and texture of the cheese of the fourth trial at 15 d after cheese making.
w),
Abbreviation key: TBA = thiobarbituric acid, WP = whey protein.
iron Sources INTRODUCTION
Femc chloride (Catalog Number F-2877) was purchased from Sigma ChCmiCal corndeficiency is the most common nutritional deficiency in developing and developed pany* % Louis- Mo* Iron-casein and Fe-WP were prepared by precipitating casein or WP from skim milk or cottage cheese whey by adding an appropriate 7kceived July 2, 1990. amount of FeCl3 and adjusting the pH to its Accepted Sqtembea 7, 1990. 4019 of the u a A ~ E~ ~ W ~isoelectric ~ ~ point as described previously (13, tion 14). 1991 J Dairy Sci 74353-358
353
354
ZHANG
AND MAHONEY
TABLE 1. Formulation of process cheddar cheese (g). Batch 1
Inmedients ~~
~
Cheddar Young Medium Aged 80% cream Water Whey powder Sodium citrate DSP' NaCl Sorbate Taco sauce Total
~
I273 508 508 257 218 164 73 36 18 18 2.3 18 1820.3
Batches 2 and 3 ~
1273 508 508 257 218 175 73 36 18 12 2.3
Batch 4
_____
1272 424 424 424 200 200 140 36 18 10 2.3
...
...
1807.3
1878.3
'DSP = Disodium phosphate.
oven at llo'C. The loss in weight was used to calculate percentage of moisture. Oxidized materials were determined from the distillates of 10-g cheese samples. Five milliliters of .02 M TBA were mixed with 5 ml of sample distillate to form a pink complex in a boiling water bath for 45 min, and then the optical density was determiued with a Bausch & Lomb (Rochester, NY) Spectronic 20 spectrophotometer at 532 nm (12, 13). Taste Panel Evaluation
The procedure for expert and open taste panel evaluation of cheese quality was described previously (15). Statistical Analysis
Process Cheddar Cheese Making
Mild, medium, and aged Cheddar cheeses and other ingredients were formulated to make process cheese (Table 1). Any loose wax, mold, or surface encrustations were removed with a sharp stainless-steel knife after the cheese was warmed to room temperature, about 21°C (70'F). Cheeses were hand chopped to fine pieces with a stainless-steel knife. Then cheeses, other ingredients, and Fe sources were poured into a steam-jacketed kettle of 2.77-kg (5-lb) capacity. The Fe sources were added to give about 40 mg Fe/kg cheese. The cheese mixtures were heated by steam in the jacket with slow agitation, 50 to 80 rpm. After 2 min, the agitation speed was increased to about 200 rpm. When the inside temperature reached 8o'C ( 1 7 0 , the contents of the cooker was immediately emptied into four plastic .454-kg (1-lb) containers. The containers were covered, inverted, and held at room temperature for 16 h. Then, they were stored in a cool room at 4.4"C (WF) until analysis of cheese quality.
Taste panel data were analyzed by analysis of variance (5). A randomized block design was used with each taste panelist being a block Thiobarbituric assay values of different batches and time periods were pooled to compute the significance of differences among the treatments (Fe-fortified and control cheeses). When F was significant (P<.05), group means were compared by least significant difference (5). RESULTS
All process Cheddar cheeses fortified with Fe in this study had their Fe levels increased to about 40 m a g (Tables 2 to 5). One hundred percent of fortified Fe was retained in the cheese, which is an advantage compared with fortification of milk for making natural Cheddar cheese (13, 15). Moisture and fat contents in all cheeses were within the standards for process cheese, except the cheeses in batch 4, which had slightly lower fat contents (Tables 2 to 5) (7). Oxidized off-flavor was not increased in the fortified process cheeses as compared with the control unfortified cheese (F5.05)(Tables 2 to Chemical Analysis 5). Also, cheese flavor of the fortified process Iron in process cheese was determined cheese was similar (F5.05) to the control colorimetrically in nitric acid wet-ashed sam- cheese. The TBA scores of all cheeses were ples with ferrozine (11, 13). Fat content was low during all time periods (10 to 90 d) deterdetermined by the Mojonnier method. Cheese mined. When the values of the batches were moisture was determined by drying to constant pooled together, average TBA scores were .07, weight about 1 g of cheese spread on the .l 1, .l1, and .10 for control, Fe-casein-fortified, bottom of a 4 c m diameter glass beaker in an Fe-WP-fortified, and FeCl3-fortified cheeses, Journal of Dairy Science Vol. 74, No. 2, 1991
355
QUALITY OF IRON-FORTIFIED PROCESS CHEESE
TABLE 2. Iron content and quality of Fe-fortified process Cheddar cheese, batch 1. LSD
Rocess cheese
control
Fe-Casein
Fe-WP1
Fa3
a = .05
Iron content, mgkg Moisture, % Fat, % TBA Number 10 d 30 d 90d Taste panel score2 Oxidized off-flavor 10 d (7)3 30 d (8) 90 d (10) Cheese flavor 10 d (7) 30 d (8) 90 d (10)
5 38.4 34.2
45 38.5 34.3
47 39.0 32.7
50 39.2 32.7
... ... ...
.05 .06 .05
.14 .12 .12
.09 .20 .09
.07 .18 .I 1
... ... ...
2.3 2.4 2.9
2.1 2.0 3.3
2.2 2.1 2.8
2.4 2.6 3.4
NS
7.0 5.6 5.7
6.6 5.8 5.8
6.1 5.9 6.0
6.7 55 5.6
NS NS
NS NS
NS
'WP = Whey protein, LSD = least si@icant difference, TBA = thiobarbituric acid. %aste panel scores were set from 1to 10. For oxidized flavor, the higher score indicated a stronger flavor. For cheese flavor, the higher score indicated a better quahty. 3 ~ ~ inu the u parentheses are the numbers of the panelists.
respectively. The differences in average TBA of the cheeses did not increase with the time of scores among the groups were marginally sig- storage. The open taste panel of 94 volunteer nificant ( P = .049) with the control cheese lay subjects did not detect significant M e r having a slightly lower TBA score than Fe- ences in texture and flavor among the Fecasein and Fe-WP cheeses (least significant fortified and control cheeses (B.05)(Table 6). difference = .032). Thiobarbituric assay scores This is consistent with the evaluations of expert TABLE 3. Iron content and quality of Fe-fortifed process Cheddar cheese, batch 2. LSD
Process cheese
Control
Fe-Casein
Fe-WP'
FeCli
Iron content, mgkg Moisture, % Fat, 9% TBA Number 10 d 30 d 90d Taste panel score* Oxidized off-flavor 10 d (8)3 30 d (8) 90 d (8) Cheese flavor 10 d (8) 30 d (8) 90 d (8)
4 38.1 34.4
35 36.5 34.6
40
44 38.0 33.8
.07 .14
.16 .14
.06
.08
38.6 34.3 .12 .16 .09
.12 .12
.06
a = .05
... ... ...
... ...
...
2.0 2.4 1.6
2.4 2.2 1.8
2.4 2.3 1.8
2.1 25 1.8
NS NS NS
6.4 6.6 5.8
6.0 6.7 6.1
6.2 6.7 6.6
6.4 7.0 6.2
NS NS NS
IWF' = Whey protein, LSD = least significant difference, TBA = thiobarbituric acid. %ate panel scores were set from 1 to 10. For oxidized flavor, the higher score indicated a stronger flavor. For cheese flavor, the higher score indicated a better quality. 3va1uw in the parenttwe are the n u m b of the panelists. Journal of Dairy Science Vol. 74. No. 2, 1991
356
M A N G AND MAHOIWY
TABLE 4. Iron content and quality of Fe-fortified process Cheddar cheese, batch 3.
Process cheese
Control
Fecasein
PSwPl
Fa?
Iron content, mgkg Moisture, 96 Fat, 96 TBA Number 10 d 30d 90d Taste panel score' Oxidized off-flavor 10 d (8Q 30 d (9) 90 d (8) Cheese flavor 10 d (8) 30 d (9) 90 d (8)
2 37.3 32.2
41 37.2 33.6
39 37.2 33.6
39 37.3 34.6
.05
.w
.06
.09
.10 .10
.09
.ll .09
.12
.08
.08
LSD a = .05
... ...
...
... ... ...
2.8 2.3 2.1
2.4 2.1 2.6
3.0 1.9 2.2
3.1 1.9 1.9
NS NS NS
7.2 6.4 6.5
7.1 7.0 5.9
6.6 6.1 5.5
6.4 6.8 6.6
NS NS NS
'WP = Whey protein, LSD = least signithnt difference, TBA = thiobarbituric acid. 2Taste panel sco~ts were set from 1 to IO. For oxidized flavor, the hi&r score indicated a stronger flavor. F O cheese ~ flavor. the higher score indicated a bequality.
'va~ues in parentheses are the numtxm of the panelists.
taste panelists (T.able
5 ) for this batch of
cheeses. DISCUSSION
fied versus unfortified control cheese. First, the source of cheese and the proportion of aged cheese in the formulations were varied. The cheeses used in batch 4 were from a different
source than the other three batches, and the In this study, several factors were varied proportion of young, medium, and aged cheese among the different batches of process cheese, in batch 4 also differed. Second, 10% less but none of them affected the quality of forti- cream and about twice as much whey powder
TABLE 5 . Iron content and @ty
of Fe-fortSed process cheddar cheese, batch 4.
LSD
Proms cheese
Control
FeCasein
FSwPl
Fa?
a = .05
Iron content, Moisture, 96
2 38.5 29.5
43 38.6 29.6
45 39.3 30.0
42 39.6 29.4
... ... ...
Fat, %
TBA Number 15 d 90d Taste panel score2 Oxidized off-flavor 15 d (9p 90 d (8) cbeese flavor 15 d (9) 90 d (8)
.08 .05
.09 .08
.os
.w
.06 .06
... ...
2.4 3.2
2.5 3.3
2.5 2.9
1.8 3.4
NS NS
6.4 5.8
5.6 6.1
6.0 62
5.9 6.7
NS NS
'WP = Whey protein, LSD = least significant difference. TBA = thiobarbituric acid. %'ask panel scores were set frcrm 1 to 10.Por oxidized flavor,the higher score indicated a stronger flavor. For cheese. flavor, the h i g h score indicated a better quality. 'values in the parentheses are the numbers of the panelists.
J o d of Dairy Science Vol. 74, No. 2, 1991
357
QUALITY OF IRON-FORTIPIEDPROCJSS CHEESE TABLE 6. Open taste panel scores for iron-fortifkd cheese,’ batch 4. control
Fecasein
F e - e
FeCl3
LSD
Textnre
6.3
6.0 6.0 6.0
NS
6.2 6.1
6.1 6.0 5.9
5.9
Flavor o v d
5.6
5.7
NS NS
lTaste panel scores were hedonic scores set from 1 to 10 for which 1 was “dislike extremely” and 10 was “like extremely.” Each value is a mean of 94 volunteex lay subjects. 2WF’ = Whey protein, LSD = least significant difference calculated when F was larger than .05 (PC.05).
was used in batch 4 as in the other three batches. Third, salt was reduced to two-thirds in batches 2 and 3, and to about one-half in batch 4 as compared with batch 1. Fourth, taco sauce was not included in the batches 2, 3, and 4. All these changes were based upon the flavor preference, the standards for process cheese, and consideration of determining more variables such as the cheese source, proportion of various aged cheese. and addition of taco sauce. However, by analysis of variance. the effect of Fe fortification on the cheese quality was not statistically significant among these batches of process cheese. Therefore, it appears that Fe fortification of process cheese permits substantial variations in formulation and cheese sources. The TBA and taste panel scores of the process cheese fortified with FeC13 were similar to those of the cheese fortified with Fe-casein or F e w , indicating that prebinding of Fe to proteins is not necessary. Iron from femc salts and small molecular complexes, such as FeC13 and Fe3+-fructose, readily binds to proteins forming Feprotein complexes (6, 13, 14, 15). Iron fortification did not affect the quality of Cheddar cheese in our previous study (13, 15) or quality of process cheese in this study, although some differences exist between these two cheeses. For Cheddar cheese, milk coagulation is involved, heating is at low temperature, pH is low, and microbial organisms from the starter culture are still growing during the aging period. In contrast, for process cheese, a relatively high temperature is applied, pH is high, and other ingredients are added to the cheese. However, they both have high protein contents, which may act as a chelator of Fe. This may be the main reason that low lipid peroxidation was observed in both kinds of Fefortified cheeses. Another reason for low lipid
peroxidation may be the saturation of the fat.
Milk fat contains mostly saturated fatty acids; 30% of the fatty acids are unsaturated, of which about 3% are polyunsaturated (2). Also, for lipid peroxidation to occur, both F$+ and Fe3+ are required with maximal rates of lipid peroxidation at the ratio of F$+ to Fe3+ being approximately 1 (3, 8, 9). However, it is unlikely that Fe bound to milk protein is Gree to change its oxidation state at the pH of cheese. Therefore, the conditions are favorable for Fe fortification of cheese products. About 2 billion lb of process cheese and cheese foods are produced each year in the US (1). Young children and teenagers enjoy process cheese, making Fe-fortified process cheese more meaningful to target this population in prevention of Fe deficiency. Using the Fe fortification level of 40 m a g cheese, if all process cheese and cheese foods were fortified with Fe, 36 billion mg more dietary Fe would be provided to US consumers each year. Overall, an average of .5 mg extra dietary Fe/d, per person would be provided from process cheese. Fortified process cheese would be expected to contribute relatively more benefit to children and teenagers at risk of Fe deficiency, because they eat more process cheese than other segments of the population. Iron fortification of process cheese improves this product nutritionally from almost no Fe to an Fe-rich food, 11 mg/1000 kcal. ACKNOWLEDGMENTS
This research was supported by the Western Dairy Foods Research Center, National Dairy Promotion and Research Board, and Utah Agricultural Experiment Station Project 253. The authors thank Randall Bagley for his instruction in process cheese making. Journal of Dairy Science Vol. 74, No. 2, 1991
358
ZHANG AND MAHONEY REFERENCES
1Agricultural Statistics Board, National Agricultural Statistics Service, May 1989. Page 27 in Dairy products 1988 Summary.US Dep. Agric.. Washington,
Dc. 2BIanc, B. 1981. Biochemical aspects of human milkcomparison with bovine milk. World Rev. Nu@. Diet. 361. 3Bucher. J. R, M. Tien, and S. D. Aust. 1983. The requiremat for ferric in the initiation of lipid peroxidation by chelated ferrous iron. Biochem. Biophys. Res. Commun. 111:777. 4Dallman, P. R..R. Yip, and C. Johnson. 1984. Prevalence and causes of anemia in the United States, 1976 to 1980. Am. J. Clin. Nutr. 39437. 5Dowdy, S., and S. Wearden. 1983. Statistics for research. John Wiley and Sons, Inc., New York, NY. 6Hegenauer. J., P. Saltman, D. Ludwig, L. Ripley, and A. Ley. 1979. Iron-supplemented cow milk. Identification and speceal properties of iron bound to casein micelles. J. Agric. Food Chem 27:1294. 7Kosikowski, P. 1982. Cheese and fermented milk foods. 2nd ed. 3rd Printing. F. V. K o s i k o d and
Journal of Dairy Science Vol. 74, No. 2, 1991
Associates, Brooktondale, NY. 8 Miller,M D., and S. D. Aust. 1989. Studies of ascorbatedependent, iron-catalyzed lipid peroxidation. Arch. Biochem Biophys. 271:113. 9 Minotti, G..and S. D. Aust. 1987. The requirement for iron in the initiation of lipid peroxidation by iron (II and ) hydrogen peroxide. J. Biol. Chem. 2621098. 10 Skilme, B. S. 1988. Current concepts in iron deficiency anemia. Food Rev. Int. 4:137. 11 Stookey, L. L. 1970. Ferrozinba new spectrophob metric reagent for iron. Anal. Chem. 42779. 12Tarladgis, B. G., B. M. Watts, and M.T.Younathan. 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods. J. Am. Oil chem. Soc. 37:44. 13 zhang, D., and A. W. Mahoney. 1989. Effect of iron fortification on quality of cheddar cheese. J. Dairy Sci. 72:322. 14zhang, D., and A. W. Mahoney. 1989. Bioavailability of iron-milk-protein complexes and fortified Cheddar cheese. J. Dairy Sci. 722845. 15 Zhaug, D., and A. W.Mahoney. 1990. Effect of iron fortification on quality of Cheddar cheese. 2. meets of aging and fluorescent light on pilot scale cheeses. J. Dairy Sci. 73:2252.
Logan 8 4 3 2 2 4 m ABSTRACT
countries (10). The Second National Health and Nutrition Examination S w e y estimated that the prevalence of iron deficiency anemia in the US is at 5.7% for 1- to 2 yr-old infants, 5.9% for 15- to 17-yr-old girls, 4.5% for young women, and 4.8% for elderly men (4). Although dairy products are the richest and primary sources of dietary Ca, the mineral needed to prevent osteoporosis and high blood pressure, they contribute little dietary Fe (7). Fortifying dairy products with Fe would enhance their nutritional value. Cheddar cheese has been successfully fortified with Fe in previous studies (13, 14, 15). The objective of this study was to determine the effect of Fe fortification on the quality of process Cheddar cheese.
Dairy products Contribute high quality protein, calcium, and other nutrients but no Fe to human diets. In this study, we determined whether Fe fortification affected the quality of process Chedda~ cheese fortified with Fecasein, Fe-whey protein, or FeCl3. An unfortified process cheese served as a control. Iron concentrations in the fortified cheeses were about 40 m a g , an Fe density of 10 mg/ loo0 kcal; and unfortified cheese contained 1 to 2 mg h a g . The quality of the pracess cheese was determined by thiobarbituric acid assay and taste panel evaluation. Thiobarbituric acid numbers were slightly lower in the unfortified cheese (P = .049). A taste panel of experts did not detect any differences in oxidized off-flavor or cheese flavor among the cheeses that have been stored as long as 3 mo (B.05).A panel of 94 lay subjects gave similar hedonic scores to the flavor, texture, and overall quality of the Fe-fortified and unfortified cheeses (B.05).Results indicate that it is possible to produce good quality, Fe-foltified process Cheddar cheese. (Key words: iron fortification, iron-& protein complexes, process Cheddar cheese)
MATERIALS AND METHODS Experlrnental Design
A batch of four process Chedda~cheeses, no Fe added (control), fortified with Fe-casein, Fewhey protein or FeCl3 were made in four trials (4 x 4). Cheese quality was determined chemically by thiobarbituric acid W A ) assay and organoleptically by food scientists 10 d to 3 mo after the cheeses were manufactured. Using a hedonic rating scale, an open taste panel of 94 lay people evaluated the flavor and texture of the cheese of the fourth trial at 15 d after cheese making.
w),
Abbreviation key: TBA = thiobarbituric acid, WP = whey protein.
iron Sources INTRODUCTION
Femc chloride (Catalog Number F-2877) was purchased from Sigma ChCmiCal corndeficiency is the most common nutritional deficiency in developing and developed pany* % Louis- Mo* Iron-casein and Fe-WP were prepared by precipitating casein or WP from skim milk or cottage cheese whey by adding an appropriate 7kceived July 2, 1990. amount of FeCl3 and adjusting the pH to its Accepted Sqtembea 7, 1990. 4019 of the u a A ~ E~ ~ W ~isoelectric ~ ~ point as described previously (13, tion 14). 1991 J Dairy Sci 74353-358
353
354
ZHANG
AND MAHONEY
TABLE 1. Formulation of process cheddar cheese (g). Batch 1
Inmedients ~~
~
Cheddar Young Medium Aged 80% cream Water Whey powder Sodium citrate DSP' NaCl Sorbate Taco sauce Total
~
I273 508 508 257 218 164 73 36 18 18 2.3 18 1820.3
Batches 2 and 3 ~
1273 508 508 257 218 175 73 36 18 12 2.3
Batch 4
_____
1272 424 424 424 200 200 140 36 18 10 2.3
...
...
1807.3
1878.3
'DSP = Disodium phosphate.
oven at llo'C. The loss in weight was used to calculate percentage of moisture. Oxidized materials were determined from the distillates of 10-g cheese samples. Five milliliters of .02 M TBA were mixed with 5 ml of sample distillate to form a pink complex in a boiling water bath for 45 min, and then the optical density was determiued with a Bausch & Lomb (Rochester, NY) Spectronic 20 spectrophotometer at 532 nm (12, 13). Taste Panel Evaluation
The procedure for expert and open taste panel evaluation of cheese quality was described previously (15). Statistical Analysis
Process Cheddar Cheese Making
Mild, medium, and aged Cheddar cheeses and other ingredients were formulated to make process cheese (Table 1). Any loose wax, mold, or surface encrustations were removed with a sharp stainless-steel knife after the cheese was warmed to room temperature, about 21°C (70'F). Cheeses were hand chopped to fine pieces with a stainless-steel knife. Then cheeses, other ingredients, and Fe sources were poured into a steam-jacketed kettle of 2.77-kg (5-lb) capacity. The Fe sources were added to give about 40 mg Fe/kg cheese. The cheese mixtures were heated by steam in the jacket with slow agitation, 50 to 80 rpm. After 2 min, the agitation speed was increased to about 200 rpm. When the inside temperature reached 8o'C ( 1 7 0 , the contents of the cooker was immediately emptied into four plastic .454-kg (1-lb) containers. The containers were covered, inverted, and held at room temperature for 16 h. Then, they were stored in a cool room at 4.4"C (WF) until analysis of cheese quality.
Taste panel data were analyzed by analysis of variance (5). A randomized block design was used with each taste panelist being a block Thiobarbituric assay values of different batches and time periods were pooled to compute the significance of differences among the treatments (Fe-fortified and control cheeses). When F was significant (P<.05), group means were compared by least significant difference (5). RESULTS
All process Cheddar cheeses fortified with Fe in this study had their Fe levels increased to about 40 m a g (Tables 2 to 5). One hundred percent of fortified Fe was retained in the cheese, which is an advantage compared with fortification of milk for making natural Cheddar cheese (13, 15). Moisture and fat contents in all cheeses were within the standards for process cheese, except the cheeses in batch 4, which had slightly lower fat contents (Tables 2 to 5) (7). Oxidized off-flavor was not increased in the fortified process cheeses as compared with the control unfortified cheese (F5.05)(Tables 2 to Chemical Analysis 5). Also, cheese flavor of the fortified process Iron in process cheese was determined cheese was similar (F5.05) to the control colorimetrically in nitric acid wet-ashed sam- cheese. The TBA scores of all cheeses were ples with ferrozine (11, 13). Fat content was low during all time periods (10 to 90 d) deterdetermined by the Mojonnier method. Cheese mined. When the values of the batches were moisture was determined by drying to constant pooled together, average TBA scores were .07, weight about 1 g of cheese spread on the .l 1, .l1, and .10 for control, Fe-casein-fortified, bottom of a 4 c m diameter glass beaker in an Fe-WP-fortified, and FeCl3-fortified cheeses, Journal of Dairy Science Vol. 74, No. 2, 1991
355
QUALITY OF IRON-FORTIFIED PROCESS CHEESE
TABLE 2. Iron content and quality of Fe-fortified process Cheddar cheese, batch 1. LSD
Rocess cheese
control
Fe-Casein
Fe-WP1
Fa3
a = .05
Iron content, mgkg Moisture, % Fat, % TBA Number 10 d 30 d 90d Taste panel score2 Oxidized off-flavor 10 d (7)3 30 d (8) 90 d (10) Cheese flavor 10 d (7) 30 d (8) 90 d (10)
5 38.4 34.2
45 38.5 34.3
47 39.0 32.7
50 39.2 32.7
... ... ...
.05 .06 .05
.14 .12 .12
.09 .20 .09
.07 .18 .I 1
... ... ...
2.3 2.4 2.9
2.1 2.0 3.3
2.2 2.1 2.8
2.4 2.6 3.4
NS
7.0 5.6 5.7
6.6 5.8 5.8
6.1 5.9 6.0
6.7 55 5.6
NS NS
NS NS
NS
'WP = Whey protein, LSD = least si@icant difference, TBA = thiobarbituric acid. %aste panel scores were set from 1to 10. For oxidized flavor, the higher score indicated a stronger flavor. For cheese flavor, the higher score indicated a better quahty. 3 ~ ~ inu the u parentheses are the numbers of the panelists.
respectively. The differences in average TBA of the cheeses did not increase with the time of scores among the groups were marginally sig- storage. The open taste panel of 94 volunteer nificant ( P = .049) with the control cheese lay subjects did not detect significant M e r having a slightly lower TBA score than Fe- ences in texture and flavor among the Fecasein and Fe-WP cheeses (least significant fortified and control cheeses (B.05)(Table 6). difference = .032). Thiobarbituric assay scores This is consistent with the evaluations of expert TABLE 3. Iron content and quality of Fe-fortifed process Cheddar cheese, batch 2. LSD
Process cheese
Control
Fe-Casein
Fe-WP'
FeCli
Iron content, mgkg Moisture, % Fat, 9% TBA Number 10 d 30 d 90d Taste panel score* Oxidized off-flavor 10 d (8)3 30 d (8) 90 d (8) Cheese flavor 10 d (8) 30 d (8) 90 d (8)
4 38.1 34.4
35 36.5 34.6
40
44 38.0 33.8
.07 .14
.16 .14
.06
.08
38.6 34.3 .12 .16 .09
.12 .12
.06
a = .05
... ... ...
... ...
...
2.0 2.4 1.6
2.4 2.2 1.8
2.4 2.3 1.8
2.1 25 1.8
NS NS NS
6.4 6.6 5.8
6.0 6.7 6.1
6.2 6.7 6.6
6.4 7.0 6.2
NS NS NS
IWF' = Whey protein, LSD = least significant difference, TBA = thiobarbituric acid. %ate panel scores were set from 1 to 10. For oxidized flavor, the higher score indicated a stronger flavor. For cheese flavor, the higher score indicated a better quality. 3va1uw in the parenttwe are the n u m b of the panelists. Journal of Dairy Science Vol. 74. No. 2, 1991
356
M A N G AND MAHOIWY
TABLE 4. Iron content and quality of Fe-fortified process Cheddar cheese, batch 3.
Process cheese
Control
Fecasein
PSwPl
Fa?
Iron content, mgkg Moisture, 96 Fat, 96 TBA Number 10 d 30d 90d Taste panel score' Oxidized off-flavor 10 d (8Q 30 d (9) 90 d (8) Cheese flavor 10 d (8) 30 d (9) 90 d (8)
2 37.3 32.2
41 37.2 33.6
39 37.2 33.6
39 37.3 34.6
.05
.w
.06
.09
.10 .10
.09
.ll .09
.12
.08
.08
LSD a = .05
... ...
...
... ... ...
2.8 2.3 2.1
2.4 2.1 2.6
3.0 1.9 2.2
3.1 1.9 1.9
NS NS NS
7.2 6.4 6.5
7.1 7.0 5.9
6.6 6.1 5.5
6.4 6.8 6.6
NS NS NS
'WP = Whey protein, LSD = least signithnt difference, TBA = thiobarbituric acid. 2Taste panel sco~ts were set from 1 to IO. For oxidized flavor, the hi&r score indicated a stronger flavor. F O cheese ~ flavor. the higher score indicated a bequality.
'va~ues in parentheses are the numtxm of the panelists.
taste panelists (T.able
5 ) for this batch of
cheeses. DISCUSSION
fied versus unfortified control cheese. First, the source of cheese and the proportion of aged cheese in the formulations were varied. The cheeses used in batch 4 were from a different
source than the other three batches, and the In this study, several factors were varied proportion of young, medium, and aged cheese among the different batches of process cheese, in batch 4 also differed. Second, 10% less but none of them affected the quality of forti- cream and about twice as much whey powder
TABLE 5 . Iron content and @ty
of Fe-fortSed process cheddar cheese, batch 4.
LSD
Proms cheese
Control
FeCasein
FSwPl
Fa?
a = .05
Iron content, Moisture, 96
2 38.5 29.5
43 38.6 29.6
45 39.3 30.0
42 39.6 29.4
... ... ...
Fat, %
TBA Number 15 d 90d Taste panel score2 Oxidized off-flavor 15 d (9p 90 d (8) cbeese flavor 15 d (9) 90 d (8)
.08 .05
.09 .08
.os
.w
.06 .06
... ...
2.4 3.2
2.5 3.3
2.5 2.9
1.8 3.4
NS NS
6.4 5.8
5.6 6.1
6.0 62
5.9 6.7
NS NS
'WP = Whey protein, LSD = least significant difference. TBA = thiobarbituric acid. %'ask panel scores were set frcrm 1 to 10.Por oxidized flavor,the higher score indicated a stronger flavor. For cheese. flavor, the h i g h score indicated a better quality. 'values in the parentheses are the numbers of the panelists.
J o d of Dairy Science Vol. 74, No. 2, 1991
357
QUALITY OF IRON-FORTIPIEDPROCJSS CHEESE TABLE 6. Open taste panel scores for iron-fortifkd cheese,’ batch 4. control
Fecasein
F e - e
FeCl3
LSD
Textnre
6.3
6.0 6.0 6.0
NS
6.2 6.1
6.1 6.0 5.9
5.9
Flavor o v d
5.6
5.7
NS NS
lTaste panel scores were hedonic scores set from 1 to 10 for which 1 was “dislike extremely” and 10 was “like extremely.” Each value is a mean of 94 volunteex lay subjects. 2WF’ = Whey protein, LSD = least significant difference calculated when F was larger than .05 (PC.05).
was used in batch 4 as in the other three batches. Third, salt was reduced to two-thirds in batches 2 and 3, and to about one-half in batch 4 as compared with batch 1. Fourth, taco sauce was not included in the batches 2, 3, and 4. All these changes were based upon the flavor preference, the standards for process cheese, and consideration of determining more variables such as the cheese source, proportion of various aged cheese. and addition of taco sauce. However, by analysis of variance. the effect of Fe fortification on the cheese quality was not statistically significant among these batches of process cheese. Therefore, it appears that Fe fortification of process cheese permits substantial variations in formulation and cheese sources. The TBA and taste panel scores of the process cheese fortified with FeC13 were similar to those of the cheese fortified with Fe-casein or F e w , indicating that prebinding of Fe to proteins is not necessary. Iron from femc salts and small molecular complexes, such as FeC13 and Fe3+-fructose, readily binds to proteins forming Feprotein complexes (6, 13, 14, 15). Iron fortification did not affect the quality of Cheddar cheese in our previous study (13, 15) or quality of process cheese in this study, although some differences exist between these two cheeses. For Cheddar cheese, milk coagulation is involved, heating is at low temperature, pH is low, and microbial organisms from the starter culture are still growing during the aging period. In contrast, for process cheese, a relatively high temperature is applied, pH is high, and other ingredients are added to the cheese. However, they both have high protein contents, which may act as a chelator of Fe. This may be the main reason that low lipid peroxidation was observed in both kinds of Fefortified cheeses. Another reason for low lipid
peroxidation may be the saturation of the fat.
Milk fat contains mostly saturated fatty acids; 30% of the fatty acids are unsaturated, of which about 3% are polyunsaturated (2). Also, for lipid peroxidation to occur, both F$+ and Fe3+ are required with maximal rates of lipid peroxidation at the ratio of F$+ to Fe3+ being approximately 1 (3, 8, 9). However, it is unlikely that Fe bound to milk protein is Gree to change its oxidation state at the pH of cheese. Therefore, the conditions are favorable for Fe fortification of cheese products. About 2 billion lb of process cheese and cheese foods are produced each year in the US (1). Young children and teenagers enjoy process cheese, making Fe-fortified process cheese more meaningful to target this population in prevention of Fe deficiency. Using the Fe fortification level of 40 m a g cheese, if all process cheese and cheese foods were fortified with Fe, 36 billion mg more dietary Fe would be provided to US consumers each year. Overall, an average of .5 mg extra dietary Fe/d, per person would be provided from process cheese. Fortified process cheese would be expected to contribute relatively more benefit to children and teenagers at risk of Fe deficiency, because they eat more process cheese than other segments of the population. Iron fortification of process cheese improves this product nutritionally from almost no Fe to an Fe-rich food, 11 mg/1000 kcal. ACKNOWLEDGMENTS
This research was supported by the Western Dairy Foods Research Center, National Dairy Promotion and Research Board, and Utah Agricultural Experiment Station Project 253. The authors thank Randall Bagley for his instruction in process cheese making. Journal of Dairy Science Vol. 74, No. 2, 1991
358
ZHANG AND MAHONEY REFERENCES
1Agricultural Statistics Board, National Agricultural Statistics Service, May 1989. Page 27 in Dairy products 1988 Summary.US Dep. Agric.. Washington,
Dc. 2BIanc, B. 1981. Biochemical aspects of human milkcomparison with bovine milk. World Rev. Nu@. Diet. 361. 3Bucher. J. R, M. Tien, and S. D. Aust. 1983. The requiremat for ferric in the initiation of lipid peroxidation by chelated ferrous iron. Biochem. Biophys. Res. Commun. 111:777. 4Dallman, P. R..R. Yip, and C. Johnson. 1984. Prevalence and causes of anemia in the United States, 1976 to 1980. Am. J. Clin. Nutr. 39437. 5Dowdy, S., and S. Wearden. 1983. Statistics for research. John Wiley and Sons, Inc., New York, NY. 6Hegenauer. J., P. Saltman, D. Ludwig, L. Ripley, and A. Ley. 1979. Iron-supplemented cow milk. Identification and speceal properties of iron bound to casein micelles. J. Agric. Food Chem 27:1294. 7Kosikowski, P. 1982. Cheese and fermented milk foods. 2nd ed. 3rd Printing. F. V. K o s i k o d and
Journal of Dairy Science Vol. 74, No. 2, 1991
Associates, Brooktondale, NY. 8 Miller,M D., and S. D. Aust. 1989. Studies of ascorbatedependent, iron-catalyzed lipid peroxidation. Arch. Biochem Biophys. 271:113. 9 Minotti, G..and S. D. Aust. 1987. The requirement for iron in the initiation of lipid peroxidation by iron (II and ) hydrogen peroxide. J. Biol. Chem. 2621098. 10 Skilme, B. S. 1988. Current concepts in iron deficiency anemia. Food Rev. Int. 4:137. 11 Stookey, L. L. 1970. Ferrozinba new spectrophob metric reagent for iron. Anal. Chem. 42779. 12Tarladgis, B. G., B. M. Watts, and M.T.Younathan. 1960. A distillation method for the quantitative determination of malonaldehyde in rancid foods. J. Am. Oil chem. Soc. 37:44. 13 zhang, D., and A. W. Mahoney. 1989. Effect of iron fortification on quality of cheddar cheese. J. Dairy Sci. 72:322. 14zhang, D., and A. W. Mahoney. 1989. Bioavailability of iron-milk-protein complexes and fortified Cheddar cheese. J. Dairy Sci. 722845. 15 Zhaug, D., and A. W.Mahoney. 1990. Effect of iron fortification on quality of Cheddar cheese. 2. meets of aging and fluorescent light on pilot scale cheeses. J. Dairy Sci. 73:2252.