Comparison of mineral and cholesterol composition of different
commercial goat milk products manufactured in USA
Y.W. Park
*Georgia Small Ruminant Research and Extension Center, College of Agriculture, Home Economics and Allied Programs, Fort Valley State University, Fort Valley, GA 31030-4313, USA
Accepted 11 November 1999
Abstract
Concentrations of 12 major and trace minerals and cholesterol in commercial goat ¯uid milk, evaporated, powdered, yogurt, and cheese products manufactured in the US were evaluated for compositional differences. Minerals were determined by an Inductively Coupled Argon Plasma Emission Spectroscopy (ICAP), while cholesterol was analyzed using colorimetric and gas chromatographic (GC) methods. Mean total solids content (%) of ¯uid milk, evaporated milk, powdered milk, yogurt, plain soft and Monterey Jack cheeses were: 11.3, 20.9, 94.1, 11.5, 32.5, and 57.7, respectively. Mean calcium and phosphorus contents (ppm, dry basis) of the corresponding products were: 103, 125; 440, 393; 7715, 7471; 161, 144; 691, 1105; 3492, 3067, respectively. The respective iron and zinc contents (ppm) of the corresponding products were: 0.062, 0.349; 1.518, 1.635; 3.33, 30.21, 0.117, 0.338; 7.16, 3.64; 8.86, 3.81. The levels of potassium (K) in cheeses were lowest among all the products including ¯uid goat milk, suggesting that a signi®cant amount of K was lost during cheese manufacturing processes. Levels of all trace minerals were higher in yogurt and cheeses than in ¯uid milk. The levels of trace minerals in cheeses were greater than those in yogurt products. Iron and aluminum contents of certain goat milk products were considerably higher than normal, possibly due to contamination of minerals from manufacturing utensils and product metal cans. Sulphur contents of fermented products were signi®cantly greater than those of ¯uid milk, which may be accountable for the microbial synthesis of sulfur containing proteins during the manufacturing processes of the products. Cholesterol contents (mg/100 g, wet basis) of ¯uid, evaporated, powdered goat milk and Monterey Jack cheese determined by GC method were: 11.0, 24.9, 119.5 and 91.7, respectively. Cholesterol contents of the goat milk products analyzed by colorimetric method were substantially greater than those by GC method.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Commercial goat milk products; Minerals; Trace elements; Cholesterol
1. Introduction
Goats produce only approximately 2% of the world's total annual milk supply (FAO, 1997).
How-ever, their contribution to nutritional and economic wellbeing of mankind is tremendous in many parts of the world including developing and tropical countries. Goat milk differs from cow or human milk in higher digestibility, distinct alkalinity, higher buffering capa-city, and certain therapeutic values in medicine and human nutrition (Gamble et al., 1939; Devendra and
*Tel.:1-912-827-3089; fax.:1-912-825-6376. E-mail address: [email protected] (Y.W. Park)
Burns, 1970; Haenlein and Caccese, 1984; Park and Chukwu, 1988; Park, 1994). Due to the unavailability of cow milk products, goat milk and its products are important daily food sources of protein, phosphate and calcium in under-developed countries (Haenlein and Caccese, 1984; Park, 1991).
The basic nutrient composition of goat milk resem-bles cow milk, where both milks contain substantially higher protein and ash, but lower lactose content than human milk (Jenness, 1980; Haenlein and Caccese, 1984; Park, 1991). Goat milk reportedly has higher fat and ash contents in the tropics than cow counterparts (Jenness, 1980; Park, 1991), although Holstein cow milk fat is similar to that in milk of Swiss goats. On the other hand, literature on basic nutrient compositions of different types of manufactured goat milk products has been extremely limited.
Mineral contents of goat milk from French-Alpine and Anglo-Nubian breeds showed higher Ca, P, K, Mg, and Cl, and lower Na and S levels than bovine milk (Park and Chukwu, 1988). Mineral contents of commercial US goat milk yogurt have been shown to have signi®cant differences in the levels of Ca, Mg, P, Fe, Zn, and Al between different yogurt varieties (Park, 1994). Mineral concentrations of 30 varieties of commercial goat milk cheeses produced in the US revealed that there were wide variations in concentra-tions of P, K, Ca, Na, Cl, Fe, Al, and Zn among and within varieties of the cheeses (Park, 1990).
The cholesterol content of goat milk was reportedly in the range 10±20 mg/100 ml (Steger, 1960). Cho-lesterol contents of goat, cow and human milks are reported as 11, 14 and 14 mg/100 g, respectively (USDA, Handbook No. 8±1, Posati and Orr, 1976). Mean cholesterol contents of cow milk Cheddar cheese were 105 mg/100 g (Posati and Orr, 1976) and 100 mg/100 g (Holland et al., 1989), while the range of cholesterol for the Cheddar cheese was 95.6± 100.8 mg/100 g (Lacroix et al., 1973). The range of cholesterol concentrations (wet basis) of 15 varieties of US and imported commercial goat milk cheeses was 80±147 mg/100 g (Park, 1999).
There has been a variety of scattered reports avail-able on nutritional values of goat milk products, mainly in ¯uid milk and cheese products. However, few comprehensive research data have been documen-ted on mineral and cholesterol concentrations of dif-ferent types of commercially manufactured goat milk
products, including condensed and powdered milk products. The objectives of this study were to: (1) determine the levels of basic nutrients, major and trace minerals, and cholesterol in commercial goat ¯uid, evaporated and powdered milk products manufactured in the US, and (2) compare differences in the nutrient contents between different types of commercial man-ufactured goat milk products.
2. Materials and methods
2.1. Preparation of goat milk products
The commercial ¯uid, condensed, and powdered goat milk products were purchased from several health and natural food stores located in the middle of Georgia (mainly in Macon and Warner Robins area) and the Houston metropolitan area in Texas.
Two or more different brands and several lots within a brand were purchased from several retail outlets in the two States. Since very few commercial manufac-turers for evaporated and powdered goat milk exist in the US, the numbers of individually packaged pro-ducts available at the time of the study from the stores for the ¯uid, evaporated, and powdered milk products were eight (two brands, four different lots), 12 (two brands, six different lots), and 10 (two brands, ®ve different lots), respectively.
For other manufactured products, such as goat milk yogurt and cheeses, the previously reported data from our laboratory were used for the comparison of com-positional differences in mineral and basic nutrient contents. Commercially marketed eight different vari-eties of goat milk yogurt, and 30 varivari-eties of goat milk cheeses were evaluated in two separate previous stu-dies (Park, 1990, 1994). Several batches of Monterey Jack goat milk cheeses were manufactured at Fort Valley State University, and evaluated for basic nutri-ents and cholesterol contnutri-ents for comparison purpose.
2.2. Chemical analysis
2.2.1. Total solids
were analyzed in triplicate, and the analysis was repeated if necessary.
2.2.2. Protein
Total nitrogen was assayed by micro-Kjeldahl pro-cedure (Richardson, 1985), using micro-Kjeldahl ana-lyzer (Kjeltec Auto 1030, Tecator, Hoganas, Sweden). Total protein was calculated by % total Nfactor of 6.38.
2.2.3. Fat
Percent fat in ¯uid and condensed milk samples were determined by Babcock method as described by Richardson (1985). Fat content of the powdered milk was assayed by ether extraction method. After extrac-tion, 10 ml-aliquots of the lipid extract in triplicate were volatilized under the exhaust hood, dried in a laboratory oven at 1058C for 2 h, and fat contents of the powdered milk samples were quanti®ed by deter-mining percent dried weight relative to original milk weight.
2.2.4. Ash
Ash content was quantitated by dry ashing the samples in a muf¯e furnace at 5508C for 24 h. Sample amounts used for ash analysis for the ¯uid, evaporated, and powdered milk were 5 g, 2 g, and 1 g, respec-tively.
2.2.5. Mineral analysis
The dry ashed samples in porcelain crucibles were solubilized with 10 ml of 6N HCl, quantitatively transferred into 25 ml volumetric ¯asks, and diluted to volume with double-deionized water (AOAC, 1984). Concentrations of major and trace minerals were quanti®ed by Inductively Coupled Argon Plasma Emission Spectroscopy (Model Atom-Comp-1100, Jarrell-Ash, Franklin, MA) with an auto-sampling system. The sample ¯ow rate was 0.625 l/min, and the nebulizer pressure was set at 40 psi. Wavelengths used for the tested minerals were: S, 182.0; P, 214.9; K, 766.2; Mg, 279.0 or 279.5; Ca, 315.8 or 317.9; Na, 588.9 or 330.2; Fe, 271.4; Al, 308.2; Mn, 257.6; Cu, 324.7; Zn, 213.9 nm, respectively.
2.2.6. Cholesterol analysis
1. Lipid extraction: Lipids of samples were extracted from 2±5 g of experimental samples (5 g for ¯uid
milk and 2 g for solid products) in 100 ml chloro-form±methanol solvent (2:1, v/v) using Folch et al. (1957). Triplicate of 1 ml-aliquots of the extracts were dried under nitrogen in a 50±608C water bath (N-EVAP, Organomation, Model No. 112). 2. Cholesterol analysis: Cholesterol contents of the
experimental samples were determined by a modi®ed colorimetric method of Rudel and Morris (1973). The analytical procedure was described in our previous report (Park, 1999). Because con-siderable differences were found between colori-metric and gas chromatographic (GC) methods in cholesterol determination in the previous report (Lacroix et al., 1973), some samples were also analyzed by GC method using the AOAC procedures (AOAC, 1995; No. 45.4.10) for comparison purpose.
For the gas chromatographic (AOAC, 1995) method, lipid extract sample was saponi®ed with ethanolic KOH solution at high temperature (758C). Unsaponi®able fraction containing cholesterol and other sterols was extracted with toluene. Sterols were derivatized to trimethylsilyl (TMS) ethers and then quanti®ed by gas chromatography. 1ml of derivatized standards and samples were injected into the GC (Hewlett-Packard Model 5890A). The internal stan-dard, 5a-cholestane and cholesterol peaks were
deter-mined by height-width measurement with a digital integrator (Hewlett-Packard Model 3396A).
2.3. Statistical analysis
All data were statistically analyzed using General Linear Model of SAS program (SAS, 1990). Analysis of variance (ANOVA), Duncan's multiple mean com-parison among different goat milk products were performed as described by Steel and Torrie (1960).
3. Results and discussion
lower protein, fat, and ash contents in the ¯uid milk of this study compared to those data reported in the USDA Handbook No. 8-1 (Posati and Orr, 1976), apparently resulted in the lower total solids content of the commercial ¯uid milk product. These composi-tional differences might have been attributable to the differences in sources of original milk used for pro-cessing the products, because the nutrient composi-tions of goat milk can be greatly in¯uenced by several factors such as season, stages of lactation, breed, diet, individual animal, and environmental management conditions (Jenness, 1980; Haenlein and Caccese, 1984; Park and Chukwu, 1988; Park, 1990, 1991).
The evaporated (condensed) goat milk product had lower total solids and other basic nutrient contents compared to the evaporated cow milk products reported in the USDA Handbook No. 8-1 (Table 1).
This result suggests that the commercial evaporated goat milk product contained higher moisture than the corresponding cow milk product. The differences in moisture between the two products might be accoun-table for the differences in the extent of evaporation and/or possible laboratory errors resulted from poor sampling practices such as insuf®cient homogeniza-tion before analysis.
The protein, fat, and ash contents of the commercial powdered goat milk showed slightly higher than those of cow milk counterparts, while the total solids con-tents were slightly higher in cow product (Table 1). Goat milk has generally higher protein, fat and phos-phate than cow milk, although its composition can vary considerably with many factors such as diet, breeds, and environmental management conditions (Haenlein and Caccese, 1984; Park, 1991).
Table 1
Basic nutrient contents (%) of commercial US goat milk products (wet basis)
Goat milk product Total solids Protein Fat Carbohydrates Ash
X SD X SD X SD X SD X SD
Fluid milk
Present studya 11.3 0.05 2.92 0.09 3.40 0.10 4.15 0.13 0.79 0.01
USDAb 13.0 0.15 3.56 0.03 4.14 0.05 4.45 ± 0.82 0.01
Evaporated milk
Present studya 20.85 0.05 6.11 0.33 6.75 0.05 6.56 0.53 1.43 0.10
USDAc 25.86 0.08 6.81 0.03 7.56 0.01 10.04 ± 1.55 0.02
Powdered milk
Present studya 94.1 0.56 27.0 0.45 28.2 1.35 32.0 0.33 6.77 0.15
USDAd 97.5 0.13 26.3 0.18 26.9 0.25 38.4 ± 6.08 0.09
Yogurte
Plain 11.5 2.56 3.99 0.12 2.25 0.13 4.49 0.56 0.82 0.02
Blueberry 17.7 2.34 3.37 0.13 1.18 0.17 12.6 2.72 0.86 0.09
Cheesef Soft
Plain 40.2 6.81 18.9 5.26 22.5 4.37 ± ± 1.74 0.97
Herb 40.9 2.11 17.3 2.26 21.8 2.13 ± ± 1.60 0.61
Hard
Cheddar 58.3 1.76 30.3 0.56 26.6 1.13 1.40 ± 3.60 0.13
Blue 74.1 1.62 20.2 0.35 31.8 1.06 ± ± 3.32 0.36
aMeans of eight ¯uid milk (two brands, four different lots), 12 evaporated milk (two brands, six different lots), and 10 powdered milk (two brands, ®ve different lots) samples, respectively.
bData for ¯uid goat milk from USDA Handbook No. 8-1 (1976). cEvaporated canned cow milk from USDA Handbook No. 8-1. dPowdered whole canned milk from USDA Handbook No. 8-1. ePark (1994).
fPark (1990).
The commercial goat milk yogurt contained higher nutrients than the corresponding ¯uid milk of this study as expected (Table 1). The blueberry ¯avored goat milk yogurt showed greater total solids and carbohydrates, and lower fat than plain yogurt, due to the addition of the fruit to the product. The com-mercial goat milk cheeses (both soft and hard) had greater levels of basic nutrients than ¯uid milk, eva-porated milk and yogurt products mainly due to the higher solids contents in the former than the latter (Table 1).
Mineral concentrations of most of the major and trace minerals were proportionally higher in accor-dance with the total solids contents of each product with a few exceptions (Tables 2 and 3). For the ¯uid milk, Ca concentration was unusually low among the major minerals. The mean Ca and P content (ppm, wet basis) were 924 and 1113, while the dry basis of the corresponding minerals were 104 and 125, respec-tively. The normal ratio for the levels of Ca to P in milk has been considered as 1.2:1 (Jenness, 1980), whereas the ratio of the ¯uid goat milk in this study was 0.83:1. The reason for this signi®cantly lower Ca in the commercial ¯uid goat milk is not known. It appeared that there were no abnormalities in the relative con-centrations of Ca and P in the other commercial goat milk products (Tables 2 and 3).
Among the major minerals, potassium (K) concen-trations showed the most interesting and marked differences between the different goat milk products (Tables 2 and 3). The levels of K in plain goat milk yogurt and plain soft cheese were lower than in ¯uid milk. Furthermore, the level of K in goat milk Cheddar cheese was even signi®cantly lower than that of ¯uid milk. The other manufactured products having higher total solids contents explicitly displayed the higher levels of all other minerals tested in this study. These results imply that considerable amounts of K may be lost into whey during manufacturing processes of the products.
Sodium (Na) concentration revealed that both soft and hard cheeses had substantially higher levels of the mineral compared to the other products (Tables 2 and 3). This result suggests that signi®cant amounts of salt (NaCl) were added to the cheese products during the manufacturing processes as shown in the previous report (Park, 1990). Other manufactured products including the ¯uid milk appeared to contain normal
levels of Na, and their concentrations increased cor-respondingly with the increased levels of total solids in the products.
Sulfur (S) concentrations of yogurt products (either plain or fruit ¯avored) were signi®cantly greater than those of ¯uid milk (Tables 2 and 3), indicating that S levels had been increased during the yogurt making processes from the ¯uid milk. It has been observed that qualitative and quantitative changes occurred in vitamin, protein, carbohydrate, and bacterial contents in yogurt (Lacroix et al., 1973; Goodenough and Kleyn, 1976; Broussalian and Westhoff, 1983). With forti®cation and fermentation (i.e. evaporation, skim milk powder, and increased bacterial mass) in manufacturing, the percent protein in yogurt is increased, thus, it will almost invariably have a higher level of protein than milk (Deeth and Tamime, 1981). The bacterial cell mass constitutes about 1% of the dry matter in yogurt, which is a rich source of essen-tial amino acids (Erdman et al., 1977; Deeth and Tamime, 1981). The elevated S contents in goat milk yogurts may be attributed to the increased S-contain-ing proteins from the bacterial cell mass or addi-tional S-containing proteins in the products synthesized by the bacterial culture during the fer-mentation process.
The S contents of cheeses, especially hard cheeses such as Cheddar, were considerably greater than those of powdered products (Tables 2 and 3), suggesting that there were signi®cant increases in S contents in cheese products even if the cheeses contained signi®cantly less total solids than the powdered milk products. Previous reports indicated that fermented dairy pro-ducts are more nutritious than the original milk from which they are made (Ayebo and Shahani, 1980; Deeth and Tamime, 1981; Lee et al., 1988), implying that certain nutrients such as S-containing proteins may be synthesized by the bacteria during the fer-mentation processes of the product.
Table 2
Pro®les of mineral compositions among different commercial goat milk products (ppm, wet basis)
Goat milk product Major mineral Trace mineral
C a Mg P K Na S Fe Mn Cu Zn Al
X SD X SD X SD X SD X SD X SD X SD X SD X SD X SD X SD
Fluid milka 924 93 106 6.26 1113 72 1647 107 685 60.6 21.3 8.53 0.55 0.065 0.033 0.004 0.39 0.12 3.10 0.302 0.955 0.174 Condensed milka 2110 166 233 28.7 1887 117 2913 679 876 253 67.5 8.23 7.28 4.96 0.13 0.07 1.46 0.62 7.84 0.73 4.09 2.45 Powdered milka 8199 786 1087 104 7939 911 15378 1237 2890 224 147.4 64.5 3.54 0.93 0.43 0.11 1.55 0.54 32.1 3.95 6.92 3.27 Yogurtb
Plain 1405 149 1253 1417 736 240 1.02 0.345 0.303 3.37 3.54
Blueberry 1287 148 1164 1630 732 730 1.96 0.283 1.095 4.10 4.97
Cheesec Soft
Plain 1720 1790 146 42.2 2750 1070 258 276 4160 1870 354 289 17.8 17.5 0.955 0.106 7.40 3.09 9.05 5.75 14.8 14.7 Herb 1120 336 153 39.1 2250 312 350 293 3360 1370 299 102 17.7 10.3 1.056 0.327 6.68 1.86 7.75 2.33 17.7 10.3 Hard
Cheddar 5990 252 420 16.0 5260 1240 110 54 3610 245 780 339 7.68 1.66 0.929 0.041 4.93 0.33 6.53 5.72 14.9 3.02 Blue 8410 896 349 1.2 5750 1090 888 263 9240 684 805 324 15.2 8.18 0.933 0.023 5.60 0.83 6.89 3.79 15.2 8.18
aPresent study. See Table 1 for footnote.
bPark (1994); The original report does not have SD values. cPark (1990).
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studies on goat milk yogurt (Park, 1991) and goat milk cheeses (Park, 1990). Many goat cheese and yogurt products are produced under farmstead manufacturing processes, which can cause unintentional contamina-tion with these minerals from processing utensils and containers during manufacture of the products (Park, 1990, 1991). The metal containers of the evaporated and powdered milk products are also a probable source of the mineral contamination.
The mean Fe content (ppm, wet basis) of the ¯uid goat milk in this study was 0.55 mg/l. This result is comparable to the previous reports, where the levels of mature fresh goat milk were 0.56 mg/l (El-Alamy and Mohamed, 1978) and 0.64 mg/l (Kataoka et al., 1972), respectively. However, the average Fe content of Alpine and Nubian breeds during the 5-month experi-mental period was 1.7 ppm (mg/l) (Park and Chukwu, 1989). The mean Fe content of the condensed milk was 7.28 mg/l, which is signi®cantly higher than that of powdered milk (Tables 2 and 3). This outcome indicates that there might be a strong possibility of Fe contamination from the metal container of the condensed product as suggested in the previous report (Park, 1990). The mean Cu contents of cheeses were higher than those of ¯uid and evaporated milk, and even that of the powdered milk product (Tables 2 and 3).
The mean Zn concentration (wet basis) in the commercial ¯uid goat milk of the present study were 0.31 mg/100g (3.10 ppm; Table 2). This level is slightly lower than the report of Loennerdal et al.
(1981), where the average Zn concentrations in pas-teurized cow and goat milks were 0.4 and 0.55 mg/ 100 ml, respectively. Zinc contents of the commercial goat milk products in this study generally were higher than the other trace minerals.
With regard to mineral ratios (Ca:P, Ca:Mg, Fe:Zn, and Na:K) of the goat milk products, the ¯uid milk and plain soft cheese revealed unusually low Ca:P ratios (0.83 and 0.625) as compared with the other products, owing to the considerably lower Ca contents of the products (Tables 2 and 3). Other products showed the Ca:P ratios closer to 1.2:1, which is considered to be the normal ratio.
Among the four mineral ratios for the commercial goat milk products, Ca:Mg ratio was the highest except for the Na:K ratio in cheeses, which is in agreement with the previous report on commercial cheeses (Park, 1990). In contrast, the Na:K ratios were lower than Ca:Mg and Ca:P ratios except for the cheeses, which were substantially higher than the others (Table 4). As for Fe:Zn ratios, the values of the evaporated milk and cheeses were signi®cantly higher than those of the other tested goat products, which may be attributed to the possible contamination of Fe from the processing utensils as well as the metal container of the product, as suggested previously.
Cholesterol contents (mg/100 g, wet basis) of com-mercial ¯uid, evaporated, and powdered milk and Monterey Jack cheese determined by GC method in this study were: 11.0, 24.9, 119.5 and 91.7, res-pectively (Table 5). The respective cholesterol
con-Table 3
Pro®les of mean mineral concentrations of commercial goat milk products (ppm, dry basis)
Productsa Macro Trace
Ca Mg P K Na S Fe Mn Cu Zn Al
Fluid milk 103.9 11.93 125.2 185.3 77.06 2.40 0.062 0.004 0.044 0.349 0.107 Evaporated milk 439.9 48.50 393.4 607.4 182.6 14.07 1.518 0.027 0.304 1.635 0.853 Powdered milk 7715 1023 7471 14471 2719 138.7 3.33 0.405 1.458 30.21 6.512 Yogurt
Plain 161 17.7 144 163 84.6 27.6 0.117 0.040 0.035 0.388 0.407
Blueberry 227 26.2 206 289 130 129 0.347 0.050 0.494 0.726 0.880
Cheese
Plain Soft 691 58.7 1105 104 1672 142 7.16 0.384 2.97 3.64 5.95
Cheddar 3492 250 3067 64.1 2105 465 8.86 0.541 2.87 3.81 8.69
tents on dry basis for the corresponding goat milk products were: 1.25, 5.18, 112.4 and 38.7 mg/100 g, indicating that cholesterol levels of the goat products were proportionally higher to the dry matter
contents of the products. The cholesterol content of Monterey Jack goat milk cheese by GC method was comparable to that of cow milk Cheddar cheese (Table 5).
Table 4
Comparison of mineral ratios in different commercial goat milk products Goat milk products Mineral ratio
Ca:P Ca:Mg Fe:Zn Na:K
Fluid milk
Present studya 0.83 8.72 0.18 0.42
USDAb 1.21 9.57 0.17 0.26
Evaporated milk
Present studya 1.12 9.06 1.77 0.30
USDAc 1.29 10.87 0.25 0.35
Powdered milk
Present studya 1.03 7.54 0.11 0.19
USDAd 1.18 10.73 0.14 0.28
Yogurte
Plain 1.12 9.43 0.30 0.52
Blueberry 1.11 8.70 0.07 0.45
Cheesef
Plain soft 0.63 11.78 1.97 16.1
Cheddar 1.14 14.26 1.18 32.8
aSee the number samples used for the ratios in Table 1. bFluid goat milk from USDA Handbook No. 8-1. cEvaporated cow milk from USDA Handbook No. 8-1. dPowdered whole cow milk from USDA Handbook No. 8-1. ePark (1994).
fPark (1990).
Table 5
Comparison of fat and cholesterol contents (wet basis) in different manufactured goat milk products in the US Goat milk products Moisture (%) Fat (%) Cholesterol (mg/100 g)
Colorimetrica GCb
X SD X SD
X SD X SD
Fluid milkc 88.6 0.24 3.40 0.15 19.5 2.58 11.0 0.80
Evaporated milkc 79.2 0.68 6.75 0.25 43.9 6.20 24.9 0.75
Powdered milkc 5.93 0.26 27.9 0.19 236.5 21.0 119.5 7.50
Cheese
Plain softd 67.5 0.02 17.7 0.25 120.8 3.30 ± ±
Monterey Jackc 42.3 0.06 24.0 1.03 124.0 2.80 91.7 0.65
Cheddare 36.6 0.11 32.8 0.51 210.0 ± 99.4 5.74
aDetermined by colorimetric method (Rudel and Morris, 1973). bDetermined by gas chromatographic method (AOAC, 1995). cPresent study.
dPark (1999); Texas Chevre is one of the plain soft goat milk cheese variety. eLacroix et al. (1973); Cow milk Cheddar cheese.
When the two analytical methods were compared for precision of the determination of cholesterol in the commercial goat milk products, the colorimetric method resulted in substantially higher cholesterol levels, in most cases almost double amounts, than the GC method (Table 5). Lacroix et al. (1973) observed that cholesterol concentrations analyzed by colorimetric method in their cow milk products were considerably greater than those by GC method due to the turbidity of the sample medium which caused the scattering of the absorption measurements. Similarly high levels and variability of cholesterol by the colorimetric method were also observed in a recent study of goat milk cheeses (Park, 1999).
4. Conclusions
The lower total solids, protein, fat, and ash contents of the commercial ¯uid goat milk in this study, compared to those in the USDA Handbook No. 8-1, may suggest that different brands and lots of com-mercial goat milk and manufactured products mar-keted in retail outlets can have variations in basic nutrient contents depending upon the sources of ori-ginal milk used. Likewise, mineral and cholesterol concentrations of different commercial goat milk products may also vary due to the original milk used from different breeds of goat, individual animals, diet, stages of lactation, and environmental factors. Cho-lesterol contents of powdered goat milk and cheeses were higher than those of ¯uid and evaporated milk simply because of the higher total solids contents. Cholesterol contents of commercial goat milk pro-ducts determined by the colorimetric method were signi®cantly greater and more variable than those by the gas chromatographic method, indicating that the GC method was more precise in quanti®cation of cholesterol in dairy goat products compared to the colorimetric method.
Acknowledgements
The author appreciates Mr. Schauston Miller and Ms. Ruby Ragan for their assistance in processing goat milk in the Creamery at Fort Valley State University and Mr. C.I. Kim for his assistance in colorimetric analysis of cholesterol in the previous laboratories.
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