Detection of adulteration, physico – chemical properties, chemical composition and hygienic status of milk in Shillong, India.

· Articles
Authors

k.H.M. PALA*, S. NONGBRI, P. LAW, S. DOHLING & K. MAKDOH

Department of Botany, LadyKeane College, Shillong 793001, Meghalaya, India

*Corresponding author: K.H.M. Pala; email:khmpala@gmail.com

Abstract

Milk suppliers normally dilute, extract valuable components and add cheap and sometimes potentially harmful bulking additives for financial gains. Survey of literature reveals that no initiative has been taken to study the extent of adulteration, composition and hygienic status of milk from Shillong study. The present study was taken to address this problem. Milk samples from the unorganized (open) and organized (packaged) sectors were analyzed using standard milk adulteration kit and Food Safety and Standards Authority of India (FSSAI) approved methods. The results indicated that milk samples were adulterated, fat was skimmed and nutritional values were lower than the National standard . The extent of adulteration was highest for sucrose and maltose/maltodextrin (100%) lowest for sodium chloride (12.5%) The extraneous water added to boost production is prevalent as indicated by the low specific gravity of samples. A high percentage of packaged milk was found to be inadequately sterilized. With regard to the hygienic status, packed samples were found to be relatively better than open samples.

Keywords Milk, adulterants, Physico-chemical properties, Hygienic status, Shillong city

Introduction

Milk is an ideal form of nutrition for all ages especially for children and infants. It is readily digested and is a source for an appreciable amount of fats, proteins and also provides body building vitamins along with furnishing energy giving lactose and many other nutrients. Milk has no pronounced taste. Any pronounced taste is abnormal. Freshly drawn milk has a characteristic, but not very pronounced, odor which is quite volatile and which practically disappears when the milk is exposed to the air (Eckels et al.,1951). Although milk slightly varies in composition and properties, the milk of different species contain the same constituents in general. On average, milk is made up of 87.4% water, 12.6% milk solids (3.7% fat and 8.9% milk solids-non-fat ). The milk solids-non-fat contain protein (3.4%), lactose (4.8%), and minerals (0.7%) (Chandan, 1997). Milk suppliers normally dilute, extract valuable components and add cheap and sometimes potentially harmful bulking additives for financial gains. Some of the chemicals, adulterants and malpractices results in public health concern and malnutrition. The lack of proper hygienic conditions of processing, storing, transportation and marketing is another cause of concern. The adulteration of milk is banned due to the ill effects. Carbonate in milk causes gastro-intestinal problems including gastric ulcer, diarrhea, colon ulcer and electrolytes disturbance (Beall and Scofield, 1995). Hydrogen peroxide disturbs the antioxidants in the body disturbing the natural immunity hence increasing aging (Clare et al., 2003). Chloride in the milk disturbs the acid base balance in the body and also blood pH (Hu and Murphy, 2004). Ammonia in milk develops regression, loss of acquired speech and sensory disturbances. The presence of urea in milk overburdens the kidneys as they have to filter out more urea content from the body (Kandpal et al., 2012). In the year 2013- 2014, India was ranked among the top 5 countries in the world producing 140 million tonnes of milk (Department of Animal Husbandry, Dairying & Fisheries, Ministry of Agriculture, Government of India, New Delhi). Thus the study was carried out as a means of ensuring that the milk produced is of good quality, keeping in view the recently emerging concern of adulteration of natural milk with various illegal substances.

Materials and Methods

Milk samples were collected in the morning in and around the city of Shillong, India, in 250ml screw capped sterilized bottles, for analysis and reference. All possible precautions were taken to avoid external contamination at the time of collection and during analyzing of samples. A total of 42 milk samples of the un-organised sectors, were tested in duplicates during the monsoon (September 2014) and pre-monsoon seasons (February 2015). Testing of packaged milk was done separately.

Milk Adulterants:The milk sample were tested for the adulterants- such as formalin, urea, starch, neutralizers (NaHCO3, Na2CO3, NaOH, Ca(OH)2etc.), detergents, sodium chloride, skim milk powder, sucrose, glucose/ dextrose, maltose/maltodextrin, hydrogen peroxide, cellulose, ammonium sulphates, boric acid, pond water (Nitrate/Nitrogen) using a standard milk adulteration kit manufactured by Himedia laboratories, Mumbai, India and FSSAI approved methods (FSSAI, 2015; FSSAI, 2012).

Physio-chemical Properties: Acidity using a standard milk adulteration kit manufactured by Himedia laboratories, turbidity (IS: 1479, 1961), and average specific gravity of milk (AOAC, 2000).

Chemical composition: Parameter like percent protein, fat, total solids, SNF of milk was determined by using standard procedures. Determination of total solids by gravimetric method (IS: 12333: 1997/ISO 6731: 1989), protein % by formal titration method (Pyne, 1932), fat % in milk by Rose-Gottlieb method (AOAC, 2000).

Hygienic Status: Hygienic status of milk was measured by using Methylene Blue Reduction Test (AOAC, 1997).

Results and Discussion:

A total of 42 milk samples of the un-organised sector (open), were tested in duplicates during the monsoon (September 2014) and pre-monsoon season (February 2015). Packaged milk of the organized sector was also tested in duplicates. A summarized comparative study of the three categories i.e. local milk (pre-monsoon, monsoon) and packaged milk  were tabulated.

Physico-Chemical Properties: All three categories of the samples  were found to be alkaline as per Alzarine Test performed. The average specific gravity as observed in the present study ranges from 1.014 to 1.030. The mean specific gravity of the  milk samples, i.e. pre-monsoon, monsoon and packaged milk were 1.021, 1.021 and 1.024 (Table 1).

Adulteration: The extent of adulterants present is summarized in Table 2. All the samples tested negative for starch, cellulose, urea, formalin, hydrogen peroxide, neutralizer, pond water nitrate and boric acid.  Glucose/ Dextrose was detected only from the open samples during the monsoon period with the extent of adulteration being 65.38 %. Glucose was added to either increase the consistency which in turn will increase the lactometer reading or to improve the taste of milk. Minute traces of detergents were detected from open source and packaged milk samples. Percentages of samples with traces of detergents are 62.5% and 66.67% for monsoon and packaged milk samples respectively. The presence of detergents may be due to low maintenance of milk tanks during preparation or it may be used to emulsify and dissolve the oil in water giving a frothy solution. 53.85%, 43.75% and 100 % of the samples from the three categories, i.e. pre-monsoon, monsoon and packaged milk respectively, tested positive for Sucrose, which may indicate that it was used to mimic the natural sweetness of milk (Faraz et al., 2013). Similarly, the extent of adulteration with Skim Milk powder was 56.25%, 42.31% and 60 % from pre-monsoon, monsoon and packaged milk samples respectively. Skim milk powder was generally used to increase the thickness or relative mass of natural milk. Sodium chloride test was performed on pre-monsoon and monsoon samples, with 12.5 % and 34.62 % of the samples testing positive, but was absent from packaged milk. Sodium chloride is particularly used to interfere with lactometer reading. Similarly, the presence of Ammonium Sulphate, as an adulterant may be due to intentional addition in order to increase lactometer readings or can be from the water source. The percentages of Ammonium Sulphate were  60.25 % and 100 % for pre-monsoon and monsoon samples respectively, but reported negative from packaged milk.

Chemical Composition: Table 3, shows the chemical composition of milk, i.e. Protein, Casein, Whey Protein, Fat, Solid non Fat content and Weight of Total Solids. The average Protein content was reportedly highest (2.30%) in pre-monsoon samples followed by monsoon (2.09%), with packaged milk showing the least amount of Protein i.e. 1.91%. Protein content of samples ranges from 0.77% to 4.59%.  Casein content showed similar results. It was highest for pre-monsoon samples (1.86%), followed by monsoon (1.7%), and the least was for packaged milk which was (1.55%), ranging from 0.62% to 3.73%.  Similar results were also detected for Whey Protein, pre-monsoon samples (0.43%), monsoon (0.39%) and packaged milk (0.34 %).The minimum percentage of Whey Protein was 0.14% and maximum percentage was 0.86%.  Packaged milk showed the highest average fat content which was (2.63%), followed by Monsoon milk (2.35%) and the least was pre-monsoon samples (2.34%). The range of fat content was 1.48% to 3.32%. The average percentages of Solid Non Fat (SNF) arranged in descending order were 7.3%, 6.59% and 6.57% for packaged milk, monsoon and pre-monsoon samples respectively. The minimum percentage of SNF detected were 4.42% and maximum 9.03%.  The weight of average percentage for Total Solids were reportedly highest for packaged samples (8.71%), followed by monsoon samples (8.29%) and the least was pre-monsoon samples (8.25%) ranging from 5.23% to 11.73%. The average amount of Protein, Fat, Solid- Non-Fat and Total Solids were found to be lower than the suggested standards of FSSAI.

Hygienic Status: The hygienic status of the samples is summarized in Table 4. The general hygienic status of the samples as evident from the table showed that 76.92% and 72.22% were poor, 23.08% and 22.22% were fair for monsoon and pre-monsoon samples respectively. The hygienic status of packaged milk was 20%, 60% and 20% fair, good and excellent respectively. As per the Turbidity Test for Sterilized Milk conducted for packaged milk, only 16.67% of the samples were found to be sterilized.

 

Table 1: Specific gravity of the three categories

Pre Monsoon

Monsoon

Packaged Milk

Mean±SD

Range

Mean±SD

Range

Mean±SD

Range

Specific Gravity

1.021 + 0.004

1.018 – 1.030

1.021 + 0.004

1.014 – 1.029

1.024 + 0.001

1.023 – 1.026

 

Table 2: Adulteration of Milk samples

Adulterants

Pre Monsoon

Monsoon

Packaged Milk

Sample Positives

(%)

Sample Positives

(%)

Sample Positives

(%)

Sucrose *(0.5%)

53.85

43.75

100

Glucose/Dextrose *(1.0%)

-

65.38

-

Maltose/Maltodextrin *(0.2%)

100

100

100

Starch *(0.1%)

-

-

-

Cellulose *(2.0%)

-

-

-

Skim Milk Powder *(2.0%)

56.3

42.23

60

Urea *(0.5%)

-

-

-

Sodium Chloride *(0.1%)

12.5

34.62

-

Ammonium Sulphate *(0.25%)

60.25

100

-

Formalin *(0.5%)

-

-

-

Hydrogen peroxide *(0.05%)

-

-

-

Neutralizers *(0.05%)

-

-

-

Detergent

-

62.5

66.67

Boric acid *(0.1%)

-

-

-

 

Table 3: Chemical Composition of Milk samples

Chemical Composition

Pre Monsoon

Monsoon

Packaged Milk

Average±SD

(%)

Range

(%)

Average±SD

(%)

Range

(%)

Average±SD

(%)

Range

(%)

Protein

2.30 ± 1.06

1.11 – 4.59

2.09 ± 0.74

0.77 – 3.91

1.91 ± 0.26

1.7 – 2.21

Casein

1.86 ± 0.86

0.9 – 3.73

1.7 ± 0.60

0.62 – 3.17

1.55 ± 0.21

1.38 – 1.79

Whey Protein

0.43 ± 0.20

0.21 – 0.86

0.39 ± 0.14

0.14 – 0.74

0.36 ± 0.45

0.32 – 0.42

Fat (w/w)

2.34 ± 0.44

1.76 – 3.32

2.35 ± 0.44

1.48 – 3.14

2.63 ± 0.15

2.47 – 2.85

Solid Non Fat (SNF)

6.57 ± 1.09

5.13 – 9.03

6.59 ± 1.11

4.42 – 8.59

7.3 ± 0.38

6.89 – 7.85

Weight Total Solids

8.25 ± 1.54

6.23 –11.73

8.29 ± 1.56

5.23 – 11.11

9.29 ± 0.53

8.71 – 10.06

 

Table 4: Methylene Blue Reduction Test

Poor

Fair

Good

Excellent

Monsoon

76.92 %

23.08 %

-

-

Pre Monsoon

72.22 %

22.22 %

5.56 %

-

Packaged Milk

-

20 %

60 %

20 %

Conclusion

It is apparent from the study that a large number of samples of open and packaged milk, did not conform to the legal standards prescribed by the Food Safety and Standards Authority of India (FSSAI). The results clearly indicated that most of the milk samples were adulterated; fat was skimmed and the nutritional value of the milk samples was lower than the specified legal standard. The extent of adulteration was the highest for Sucrose and Maltose/Maltodextrin (100%) and least for Sodium Chloride (12.5%). However, adulterants such as Starch, Cellulose, Urea, Formalin, Hydrogen Peroxide, Neutralizers and Boric acid were not detected from the samples tested. The extraneous water added to boost production is very prevalent as indicated by the low Specific Gravity of samples recorded. A comparative analysis of milk during pre-monsoon and monsoon season indicates that there is not much difference in the quality of milk produced in these two seasons except for Glucose which was detected only from the monsoon samples. A very low percentage of packaged milk was found to be adequately sterilized. The average hygienic status of open samples was found to be mostly poor and packaged milk was found to be good. The study should bring about more awareness to the general public about the malpractices or negligence in milk production, depriving the people of its nutrition. The presence of adulterants detected in the study and their apparent harmful effects on the health of consumers should draw the attention of concerned authorities to the need for regular inspection.

Acknowledgement

The authors are thankful to Dr. (Mrs) C. Massar, Principal, Lady Keane College, our colleagues, students and office staff of Lady Keane College. The financial support received from the Governing Body, Lady Keane College is gratefully acknowledged.

References

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