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ORIGINAL ARTICLE
Year : 2012  |  Volume : 56  |  Issue : 1  |  Page : 82-87  

Impact of household practices on the nutritional profile of milk


1 Project Associate, Punjab Biotechnology Incubator, Mohali, Punjab, India
2 Scientist Chemical, Punjab Biotechnology Incubator, Mohali, Punjab, India
3 Head, Medical and Scientific Affairs, Nestlé India Limited, Mohali, Punjab, India
4 Manager Medico Marketing, Nestlé India Ltd., Mohali, Punjab, India
5 Chief Executive Officer, Punjab Biotechnology Incubator, Mohali, Punjab, India

Date of Web Publication6-Jun-2012

Correspondence Address:
Satwinder S Marwaha
Chief Executive Officer, Punjab Biotechnology Incubator, SCO: 7 & 8 (Top Floor), Phase-V SAS Nagar (Mohali) 160059, Punjab
India
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Source of Support: The study was conducted with fi nancial support from Nestlé India Ltd., Conflict of Interest: Sanjeev Ganguly and Vivek Garg are employees of Nestlé India Ltd. There are no other confl icts of interest.

DOI: 10.4103/0019-557X.96983

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DOI: 10.4103/0019-557X.96983

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   Abstract 

Background: It is a common practice to process milk before consumption. Processing generally involves boiling, addition of sugar and/or condiments, dilution with water, etc. The boiled milk is stored for subsequent use either at room temperature or under refrigerated conditions. Objective: The purpose of this study was to see the effect of household practices on the nutritional profile of milk. Materials and Methods: Different types of pasteurized milk samples: standardized, double toned, full cream, and unpasteurized milk were analyzed. The effect of household practices on the nutritional profile of all these milk samples was studied using National/International methods. Results: Boiling of milk increased the concentration of most of the components and minerals except for vitamins A, B 3 , B 5 , and B 12 where the decrease observed was 21%, 13%, 3%, and 21%, respectively. Addition of water decreased the concentration of minerals and vitamins. Addition of sugar increased the energy and condiments increased total solids, carbohydrate and minerals content but led to a decrease in the vitamin content. Storage of milk led to a decrease in total solids by 19% and vitamins A, B 3 , B 5 , and B 12 by 26%, 17-19%, 23%, and 18-26%, respectively. The pH was not influenced by any of the household practices. Conclusion: Every step during household practices in the handling of milk reduces its nutritional profile and significantly affects the quality. Vitamins play a very important role in health and loss during household processing becomes an interesting attribute that requires further research in detail.

Keywords: Heat treatment, Milk analysis, Minerals, Physico-chemical characteristics, Storage, Vitamins


How to cite this article:
Bahman S, Yadav N, Kumar A, Ganguly S, Garg V, Marwaha SS. Impact of household practices on the nutritional profile of milk. Indian J Public Health 2012;56:82-7

How to cite this URL:
Bahman S, Yadav N, Kumar A, Ganguly S, Garg V, Marwaha SS. Impact of household practices on the nutritional profile of milk. Indian J Public Health [serial online] 2012 [cited 2014 Oct 30];56:82-7. Available from: http://www.ijph.in/text.asp?2012/56/1/82/96983


   Introduction Top


Milk is known to contain over a hundred biochemical compounds of which the majority have substantial nutritional values namely, calcium is required to build and maintain bone mass, vitamin D is necessary to promote absorption of calcium and other minerals, vitamin B 2 (riboflavin) converts food into energy, phosphorus generates energy in body cells and strengthens bones, vitamin B 12 (cyanocobalamine) is vital for nervous system functioning and builds red blood cells, and vitamin A is important for normal vision and skin. Potassium plays an important role in normal blood pressure, and B 3 (niacin) helps in normal functioning of enzymes and metabolism of fatty acids and sugars. [1]

Considering the nutritional importance of milk especially for infants and young children, general household practices used to modify milk before consumption are very important. In a daily routine, milk (whether unpasteurized or pasteurized) is boiled before its consumption. It is a common practice of processing milk to prevent spoilage and enhance the keeping quality by reducing the levels of microflora including microbial pathogens. In some cases, sugar and/or condiments are added to improve the flavor and digestibility of milk. Dilution of milk is also a common practice in many households. Boiled milk is stored under room temperature or refrigerated conditions for variable time intervals for subsequent use.

Nutrient profiling is the science of ranking foods based on the nutrient composition. It helps the individuals to understand, identify and select certain foods to make healthier choices based on a preselected set of criteria. [2] Nutritional profiling of raw milk has been studied by many researchers [3],[4] but the impact of simulated household practices on the nutritional components is still being researched. Therefore, this study was undertaken to investigate the effect of simulated household practices on the nutritional profile of milk before its consumption.


   Materials and Methods Top


The study was carried out during the period September 2010 to November 2010, at Punjab Biotechnology Incubator, Mohali (Punjab). In view of the processing conditions/modifications carried out at user's end on milk after procurement and before actual consumption, the study was divided into three broad sections. Branded pasteurized milk with different fat content namely, seven samples of standardized milk (SM) (4.5% fat), four samples of double toned milk (DTM) (1.5% fat), two samples of full cream milk (FCM) (6.0% fat), and unpasteurized vendor's milk (VM) (variable fat compositions, i.e., 4.1-6.7% fat) were procured from the local market. As the majority of the consumers use the standardized milk, the effect of different treatments on its nutritional profiling was carried out using the customized conditions. The pouches of standardized milk procured from the local market were opened, homogenized in a stainless steel container and divided into two parts: one part of the milk was analyzed as such without any treatment (control), whereas the other part was subjected to different treatments namely, boiling, storage (under different conditions), addition of supplements and water and analyzed.

To study the effect of boiling, storage milk was boiled at medium heat by setting the knob of the gas burner at a medium indicator under uncovered conditions, and cooled. The fat layer formed after cooling on the top of milk was removed and samples were analyzed. The boiling condition was kept constant for different treatments. The boiled milk was then divided into two parts. One part of boiled milk was stored at room temperature (25-28 °C) with intermittent boiling at 12 h, and the other part was stored under refrigerated conditions (2-8°C). Both samples were analyzed after 24 h. On the other hand, a pouch of standardized milk was kept as such without boiling under refrigerated conditions (2-8 °C), and the sample was analyzed after 24 h.

To study the effect of dilution and addition of sugar, the milk samples were divided in two groups. In first group 50 and 150 ml/l of water was added to the milk and boiled at medium heat under uncovered conditions and then analyzed. In the second group, 50 ml/l of water was added to the milk, boiled at medium heat under uncovered condition and further divided into two parts. To one part, 2 tsp/200 ml (2 tsp sugar ~10 g) of sugar was added, then warmed to 40 °C, cooled to room temperature, sieved, and analyzed. To another part (also containing 2 tsp/200 ml of sugar) 50% of tap water was added, boiled at medium heat under uncovered conditions, cooled at room temperature, sieved, and analyzed.

To study the effect of supplementation of condiments, cardamom and fennel seeds in equal amounts were grounded to the powder form which was then added to the milk @1/6 tsp/200 ml (1 tsp condiment powder ? 1.8 g), boiled at medium heat under uncovered conditions for 5 min, allowed to cool, sieved through mesh, and analyzed.

The reference materials used for the analysis of different parameters were procured from M/s Supelco Sigma, USA. The proximate parameters (energy, water, total solids (TS), solid not fat (SNF), fat, protein, lactose, carbohydrates and ash) and pH were analyzed by using Indian Standard method IS: 1479 (Part II). [5] Minerals (sodium, potassium, calcium, magnesium, iron, copper, zinc, molybdenum, selenium, manganese, and fluoride) were analyzed using AAS (Perkin Model: Analyst 800) and fat-soluble vitamins (A, D, E, and K) using HPLC-DAD (Agilent Technologies, 1200 Series) following the AOAC method. [6] Water-soluble vitamins (B 1 , B 2 , B 3 , B 5 , B 6 , B 7 , B 12 , and folic acid) were analyzed using the Vita Fast Microbiological Microtiter Plate Test Kit method of r-Biopharma. [7] Vitamin C was analyzed using the titrimetric method as per the Indian Standard method IS: 5838-1970. [8] Phosphorus was analyzed by the iCAP-AES system (Thermo electron, 6300).


   Results Top


In this study, the composition of analyzed samples varied for different components of milk: water (83.2-90.3%), total solids (9.97-16.8%), fat (1.31-6.08%), crude protein (2.3-3.4%), and lactose (3.5-6.1%). The impact of different treatments including boiling, storage conditions, and supplementations on the nutritional profiling of standardized milk was studied and results obtained are:

  1. Effect of Boiling: The effect of boiling on the nutrient composition of milk is shown in [Figure 1] and [Figure 2]. Boiling of milk resulted in an increase in the concentration of all proximate components and minerals, but a 21% decrease in concentration of fat-soluble vitamin A (as retinol palmitate). In the case of water-soluble vitamins, 13%, 3%, and 21% losses have been observed in vitamins B 3 , B 5 and B 12 , respectively [Table 1]. No change in pH of the milk samples was recorded after boiling.
  2. Figure 1: Effect of boiling on nutritional quality (proximate) of standardized milk

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    Figure 2: Effect of boiling on nutritional quality (minerals) of standardized milk

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    Table 1: Effect of boiling on the nutritional quality (vitamins) of standardized milk

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  3. Effect of Storage Conditions: When the boiled milk was stored at different conditions namely, room temperature and refrigerated conditions, and unboiled milk under refrigerated conditions, the level of total solids decreased up to 19%. After storage for 24 h, when the deposited the fat layer at the top was removed, 71-76% loss of fat was observed [Table 2]. Storage of milk samples was associated with decrease in vitamin levels when analyzed after 24 h [Table 3]. The losses of 17-19%, 23% and 18-26% of vitamins B 3 , B 5 and B 12 , respectively, were observed. In the case of vitamin A, 26% losses were observed after 24 h storage.
  4. Table 2: Effect of storage conditions on proximate parameters of standardized milk

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    Table 3: Effect of storage conditions on vitamins of standardized milk

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  5. Supplementation(s)/Addition(s):
    • Addition of Water Before First Boiling : It was found that addition of 150 ml of water per liter of milk decreased the concentration of all the proximate components as well as minerals. In addition to the effect of dilution, the vitamin levels also decreased due to heating and their photosensitive nature. No change in pH in milk samples was observed indicating that this factor may not be influenced by routine household practices.
    • Addition of Sugar and Condiments : The supplementation of milk samples with sugar alone had no effect on the proximate and mineral profile, while addition of sugar and water resulted in an increase in energy, total solids, SNF, and carbohydrates. In contrast, protein, lactose, ash contents, and pH remained unaltered. Addition of condiments in the milk samples increased the contents of total solids, solid not fat (SNF), carbohydrate, and minerals (calcium and magnesium). In contrast, a considerable decrease in all the vitamins was observed.

      Boiling, storage and supplementation(s)/addition(s) to milk had no qualitative and quantitative effect on the fatty acid or amino acid profile of the milk samples tested.



   Discussion Top


The nutritional composition of milk reported in this study is similar to the profile reported earlier. [9] Various processing treatments may result in loss of nutritional quality of milk. During boiling, water evaporates as a result of which the milk components primarily proximate parameters and minerals are concentrated, resulting in a relative increase of their values. However, the boiling process had a deleterious effect on the heat sensitive vitamins. Similar effects in pasteurized milk have been reported earlier also. [10],[11],[12] While investigating the effect of boiling on bovine milk, a significant reduction in vitamins B 2 , B 3 , B 12 , and folic acid has been reported. [13],[14],[15] Fifteen minutes heating of milk has been reported to result in 24% losses of vitamin B 12 . [16] Similarly, microwave heating of milk has been reported to cause 30-40% losses in vitamin content of the bovine milk. [17] Impact of boiling on pH was also studied and found that boiling results in no change in pH. [18]

No impact of the storage condition on pH even after 24 h is contrary to the earlier finding which has reported the effect of storage on pH in bovine milk. [19] A decrease in total solids and fat content could be attributed to the decomposition of milk fat into fatty acids as a result of the lipolysis process which have a pronounced effect on sedimentation and fat separation. The results of the present investigation are in line with the studies conducted by different researchers. [18],[20] While in another study, a decrease in the calcium content during storage of pasteurized milk was reported. [21] Due to the intermittent boiling and storage, accumulation of the fat layer resulting in the loss of fat-soluble vitamin D. The appreciable loss of vitamin D in buffalo's milk during different storage conditions has also been reported. [22] The increase in the degradation of vitamins B 2 , B 3 , and B 12 observed with the increase in storage duration, boiling, and light intensity due to their photosensitive nature is in line with the earlier report. [23]

Storage of milk at low temperature resulting in the deposition of the fat layer on the wall of the storage utensil/pouch carrying away fat-soluble vitamins resulting in their substantial quantitative loss. On the other hand, exposure to light during storage has a deleterious effect on water-soluble vitamins. An appreciable loss in their contents during storage at lower temperature has been reported. [23] The addition of water decreases the contents of nutritional components due to the dilution of milk. Similarly, quantity of vitamins also decreased due to their photosensitive nature and heat effect during boiling as reported in different studies. [24]

When sugar was added to the milk, concentration of calcium and magnesium reduced which is supported by the earlier reports of data from different countries. [25],[26],[27] However, an appreciable increase in total solids, SNF and carbohydrate contents was found.


   Conclusion Top


Milk offers an optimal array of nutrients and protective factors which are essential to achieve various health benefits. This study concludes that each step adopted during household practices plays a significant role in varying the concentration of nutritional components which affects the quality of milk. Although boiling of milk is associated with some loss of water-soluble vitamins, it is an important practice which helps in improving the safety and in keeping the quality of milk. We recommend that boiling of milk before consumption should be practiced as prevention of foodborne illnesses remains a priority in the Indian context. The removal of the fat layer after subsequent storage of milk should be discouraged as it results in loss of important fat-soluble vitamins. Dilution of milk also significantly affects the nutritional profile which might lead to insufficient nutrient deliveries especially in infants and young children. Therefore, it is advised that milk should not be diluted before consumption and the practice of storage and intermittent heating of milk should be avoided to prevent the vitamin loss. Vitamins in milk play a very important role in our health; loss during household practices becomes an interesting attribute which requires further investigation in detail.

 
   References Top

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    Figures

  [Figure 1], [Figure 2]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]


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