Communication International Journal of Food Nutrition and Safety, 2013, 4(2): 55-61 International Journal of Food Nutrition and Safety Journal homepage: www.modernscientificpress.com/journals/ijfns.aspx ISSN: 2165-896X Florida, USA Nutritional Values of Powdered Milk Commercially Consumed in West Africa A. Olagunju *, A. Muhammad, S. Aliyu, S. B. Mada, R. Isah, S. A. Abdullahi, Z. O. Audu Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria * Author to whom correspondence should be addressed; E-Mail: amachida31@gmail.com; Tel.: +234703816143. Article history: Received 11 June 2013, Received in revised form 8 August 2013, Accepted 12 August 2013, Published 20 August 2013. Abstract: Milk is one of the most nutritionally complete foods available on the food markets to date. In the present study, Cowbell, Dano and Nunu milk were obtained from different markets around Kaduna state, Nigeria. The proximate analysis, vitamins and mineral composition studied revealed that the moisture and carbohydrate contents were statistically (p > 0.05) the same while the lipid, crude protein and ash content significantly (p < 0.05) varied. Dano milk has the highest ash content of 5.43±0.29% when compared with cowbell 5.27±0.15% and Nunu 4.39± 0.36%. The result of mineral analysis showed no statistical difference (p > 0.05) in the potassium, calcium, copper and cobalt concentrations among the three brands of milk. While statistical differences were observed in manganese, zinc, sodium, and iron concentrations. The result of vitamin analysis also showed minor detectible amounts of vitamin A in Dano milk, while no statistical difference was observed for vitamin B 2 and vitamin B 9. Vitamin C and vitamin E contents of the three brands of milk analyzed differ significantly (p > 0.05). Cowbell, Nunu and Dano milk have similar nutrient composition with slight degree of variability in some components. A further comparison between the analyzed result from market samples and reported amount of nutrient on the milk labels did not follow a specific pattern, as some parameters were slightly lower or slightly higher than reported. The findings from the present study may go a long way in contributing to the existing knowledge in the area of nutrition and functional foods research. Keywords: milk; proximate composition; mineral content; vitamin; lipid; protein.
56 1. Introduction Due to increasing population and economic crises in most developing nations especially in Nigeria, food insecurity has posed a serious threat to growth, development and survival of the people (Hassan et al., 2007). Milk is one of the most nutritionally complete foods available on the food markets to date. It is naturally a good provider of a whole range of nutrients essential to growth, developments and maintenance of the human body (Cannon, 1992). Powdered milk is a manufactured diary product made by evaporating milk to dryness which helps to preserve it. Powdered milk is made by either spray drying, drum drying or freeze drying. Most milk powders contain the major standard amino acids and building blocks of proteins, and are high in soluble vitamins and minerals. Powdered milk is used for food and health (nutrition) and typically also in biotechnology (saturating agent). Powdered milk is frequently used in the manufacture of infant formula, confectionery such as chocolates and caramel candy and in recipe for baked food. Milk powder is generally considered a product of good microbiological quality. However, several factors may contribute to change, its physical and chemical properties which reduce its shelf life and thus its commercial value (Cousins, 1987). The aim of this research work therefore is to compare and analyze the nutritional value of sachets powdered milk sold in open markets around Nigeria. In many food laboratories bulk of the routine analysis comprise the method of proximate analysis which involves the determination of the moisture, lipid, ash, protein, carbohydrate and fiber in addition to mineral and vitamins contents. 2. Materials and Methods 2.1. Sample Collection One cup of Cowbell, Dano and Nunu sachets powdered milk were bought from Sabo, Samaru and Tudun-wada markets in Zaria, Kaduna State, Nigeria, and kept in clean polythene bags before the analysis. 2.2. Nutrient Analysis The nutrient analysis of the samples was done using the standard methods of Association of Analytical Chemists (AOAC, 1997), for the determination of moisture content, ash content, crude protein and lipid as described below. Carbohydrate content was estimated based on the net difference between the other nutrients and the total percentage composition. 2.2.1. Moisture content analysis
57 obtained. The milk samples were dried in moisture dish in an oven at 105 o C until constant weight was 2.2.2. Ash content analysis The samples obtained from moisture content analysis were ashed in furnace at 550 o C overnight to determine the ash content. 2.2.3. Crude protein analysis Crude protein content of the milk samples was determined by weighting one gram of sample into digestion tubes. Two Kjeltabs Cu 3.5Fg (catalyst salts) were added into each tube. About 20 ml of concentrated sulphuric acid (H 2 SO 4 ) was carefully added into the tube and then shaken gently. Digestion procedure was carried out. Digested samples were cooled for 10-20 min. Distillation procedure was then performed using distillation unit and the distillate was titrated with 0.025 N sulphuric acid (H 2 SO 4 ) until the end point changes from green to pink. Volume of acid required in the titration was recorded. Blank was prepared with the exclusion of sample. The percentage of protein content was calculated according to the equation below. 0.014 VD N 100 TV % Nitrogen = % Protein =% N F Weight of sample AD Where, VD = Volume of digest, N = Normality of acid, TV = Titre value, AD = Aliquot of digest, F = Conversion factor for nitrogen to protein (6.25). 2.2.4. Fat content analysis Crude fat was obtained by exhaustively extracting 2.0 g of each sample in a Soxhlet apparatus using petroleum ether (b.p. 40-60 ºC) as the extractant. 2.2.5. Carbohydrate content Carbohydrate content was calculated based on difference calculation: Carbohydrate =100% - (% moisture + % ash + % crude protein + % fat). 2.2.6. Vitamin analysis Vitamins were determined in the samples after adopting the methods of Maciej and Krzysztof (2007), and Dahot et al. (1990) at National Research Institute for Chemical Technology (NARICT), Zaria, Nigeria, using ultraviolet-visible 2550 spectrophotometer.
58 2.2.7. Mineral analysis Exactly 0.5 g of each sample was measured and transferred to 50 ml beaker, 7.5 ml of nitric oxide HNO 3 plus 2.5 ml of hydrochloric acid were added (Hack, 2000). The sample was digested by heating on a hot plate, about 20 ml of sterile distilled water was added and allowed to cool. The sample was filtered using Whatman No.1 filter paper and the filtrate was made up to 100 ml with distilled water. The absorbance of the sample was taken using an atomic absorbance spectrum and compared with prepared standard for each sample. 2.3. Statistical Analysis Data was subjected to one-way analysis of variance (ANOVA) and least of significant difference (LSD) at 0.05 probability level. All statistical analyses of data were performed using SPSS 17.0 software and the data were reported as mean values ± standard deviation (SD). 3. Results and Discussion The result of proximate analysis from Table 1 showed no statistical difference (p > 0.05) in carbohydrate and moisture contents among the three brands of milk. While statistical differences (p < 0.05), were observed in the lipid content, protein content and ash content. Cowbell was found with the lowest protein content (8.58±0.83%), while Dano had the highest protein content (11.7±1.77%). In the ash content, while Dano was found with the highest ash (5.45±0.29%), Nunu had the lowest (4.39±0.36%). Ash content is a measure of the total amount of minerals present. Results of lipid analysis also showed Nunu with lower (27.6±5.62%) content as compared with Cowbell and Dano both with 29.8±2.74%. While some of the parameters studies in the three brands of milk did not differ (carbohydrate, moisture, and ash), differences as seen above were observed in some (protein and lipid) with no particular pattern. Comparison of the proximate composition with the reported labels did not show remarkable differences, however the moisture was found to be consistently higher in the three brands. Moisture content determines the way most foods taste, feel and look, it also is one of the important ways to measure food quality. The protein content was however found to be significantly lower than what was reported on the sachets. The recommended daily dietary allowance (RDA) for children, adult males, adult female pregnant women and lactating mothers are 28, 63, 50, 60, and 65 g of protein respectively (Ganong, 2003). The low protein contents of all the three brands compared to their sachet labeling may be due to inappropriate conditions such as high relative humidity and high ambient temperature which can significantly degrade the nutritive values (Okamoto and Hayashi, 1985).
59 Table 1. Proximate compositions of milk samples Sample Cowbell Dano Nunu Moisture (%) 3.93±0.29 a 3.75±0.37 a 4.19±0.25 a Ash (%) 5.27±0.15 a 5.43±0.29 a 4.39±0.36 b Lipid content (%) 29.1±0.47 a 29.2±2.74 a 27.6±5.62 b Protein (%) 8.58±0.83 a 10.0±1.94 b 11.7±1.77 c Carbohydrate (%) 53.2±0.36 a 51.6±0.68 a 51.9±6.49 a Note: Values are means of triplicate determinations expressed as mean ± standard deviation (SD); Values with different alphabet on the same row are significantly different (p < 0.05). The result of mineral analysis from Table 2 showed no statistical differences (p > 0.05) in potassium (17.99-15.29 mg/g), calcium (9.5036±0.33), copper (0.0130±0.00 mg/kg) and cobalt (0.07-0.05 mg/kg) concentrations among the three brands of milk analyzed. While statistical differences (p < 0.05) were observed in manganese, zinc, sodium, and iron concentrations. Thus there was no unified pattern in the differences observed among the three brands of the milk. The mineral content of the three brands of powdered milk analyzed was also found not to be consistent when compared with the reported labels on each brand. This may be due to deterioration in the composition upon prolonging storage (Fox et al., 2006). Table 2. Mineral analysis of milk sample Sample Cowbell (mg/kg) Dano (mg/kg) Nunu (mg/kg) Sodium 2.680±0.85 a 3.0081±0.70 b 3.4146±0.03 c Calcium 9.2908±0.33 a 9.5036±0.33 a 9.551±0.33 a Potassium 15.287±5.54 a 17.988±4.08 a 16.551±2.10 a Zinc 2.3170±3.96 a 2.8883±4.96 a 0.0143±0.01 b Iron 0.0501±0.02 a 0.0775±0.02 b 0.0575±0.04 a Manganese 0.0080±0.01 a 0.0032±0.00 b 0.0144±0.00 c Cupper 0.0146±0.01 a 0.0130±0.00 a 0.0130±0.00 a Cobalt 0.0488±0.01 a 0.0650±0.02 a 0.0540±0.01 a Note: Values are means of triplicate determinations expressed as mean ± standard deviation (SD); Values with different alphabet on the same row are significantly different (p < 0.05). The result of vitamin analysis from Table 3 shows minor detectible amounts of vitamin A (0.006 IU/L) in Dano milk, while no statistical difference (p > 0.05) was observed for vitamin B 2 and vitamin B 9. Vitamin C and vitamin E contents of the three brands of milk analyzed differ significantly
60 at p > 0.05. Dano milk also has the highest contents of vitamin C (9.297 mg/ml) and vitamin E (93.838 IU/L). The detectible amounts of vitamin A in Dano milk was found to be significantly lower than those reported on the various sachets label. Further comparison between the analyzed result and the sachet labels did not show remarkable difference in the other vitamins analyzed. The deficiency of vitamin A can lead to night blindness, visual impairment and growth disturbances (Insel et al., 2002). Vitamin C is an excellent antioxidant and free radical scavenging nutrient. It protects cells from damage by antioxidant action, and the RDA of vitamin C is 60 mg/day for a male adult (Ganong, 2003). Vitamin E helps in the body by acting as antioxidant and help in the prevention of propagation of free radicals. It is highly susceptible to destruction by oxygen, metals and light. As a result, prolong milk storage lowers the vitamin E content and might have contributed in the current result observed. Table 3. Vitamin content of milk samples Sample Cowbell Dano Nunu Vitamin A (IU/mL) - 0.006 - Vitamin B 2 (mg/ml) 0.030 a 0.029 a 0.033 a Vitamin B 9 (mg/l) 0.965 a 0.909 a 1.007 a Vitamin C (mg/ml) 8.045 a 9.297 b 7.090 c Vitamin E (IU/L) 84.291 a 93.838 b 72.295 c Note: Values are means of triplicate determinations expressed as mean ± standard deviation (SD); Values with different alphabet on the same row are significantly different (p < 0.05). 4. Conclusions The result of this work revealed that Cowbell, Dano and Nunu brands of milk had similar nutrient composition in terms of the moisture and carbohydrate content, while the lipid, protein and ash content showed statistical difference. The result of vitamin analysis showed minor detectible amounts of vitamin A in Dano milk, while no statistical difference was observed for vitamin B 2 and vitamin B 9. Vitamin C and vitamin E contents of the three brands of milk analyzed differ significantly. The result of mineral analysis also showed no statistical differences in potassium, calcium, copper and cobalt concentrations among the three brands of milk analyzed. While statistical differences were observed in manganese, zinc, sodium, and iron concentrations. A further comparison between the analyzed result from market samples and reported amount of nutrient on the milk labels did not follow a specific pattern, as some parameters were slightly lower or slightly higher than those reported. The findings from the present study may go a long way in contributing to the existing knowledge in the area of nutrition and functional foods research.
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