Quality of milk in Imphal : A preliminary survey

Akoijam Meerabai / Dayanidhi Huidrom *

Quality of milk in Imphal : A preliminary survey :: Pix - TSE

Introduction

The current situation with milk in Manipur shows a significant difference between production and demand. In 2022-2023, the estimated milk production in the State was around 81.77 million litres. However, the per capita availability remains low at approximately 33 grams per day, which is far below the recommended 250 grams.

The demand for milk is expected to increase significantly in the coming years. In 2019, household consumption was at 1.65 lakh litres per day, and it was projected to reach 3.52 lakh litres by 2023. It’s very likely that malpractices may have crept in.

Common adulterants found in milk pose significant health risks. These include substances such as urea, formalin, detergents, ammonium sulfate, boric acid, caustic soda, benzoic acid, salicylic acid, hydrogen peroxide, sugar, and melamine. These adulterants can lead to serious health issues, ranging from minor digestive problems to more severe conditions such as kidney damage or cancer.

For example, urea is added to artificially increase the protein content, while detergents are used to give a frothy, rich appearance, misleading consumers about the milk's quality. Formalin, a preservative, prevents spoilage but is toxic to humans, and hydrogen peroxide is used for the same purpose despite its harmful effects. Melamine, infamously involved in a major food safety incident, is used to mimic a higher protein content but can cause kidney failure.

Consumers can use several simple methods to detect adulteration in milk at home. Tests can be broadly divided into two groups viz. qualitative and quantitative test. Qualitative tests are generally cheap and fast though not necessarily precise. It however gives an important hint of the presence of components of interest. Therefore, they are precursors to quantitative estimation of the chemicals/ molecules.

Quantitative tests often require an elaborate process and standards (sample containing known amount of chemical/ molecule). Some of the new and sophisticated quantitative techniques such as Gas/Liquid Chromatography, Enzyme Linked Immu- nosorbent Assay (ELISA), Polymerase Chain Reaction (PCR), and Polyacrylamide Gel Electrophoresis (PAGE). They are employed to estimate a wide range of adulterants with high precision.

Milk adulteration is a significant concern in the food safety domain. Given the importance of safe food in one’s health and society, at large, we, Intellisome Food Testing and Research Centre (a food testing arm of Intellisome Consulting Pvt. Ltd.), conducted a quick preliminary survey to understand the food safety situation wrt milk.

This survey aims to investigate the prevalence of adulteration practices, analyse few common adulterants and inform citizens. The findings are expected to inform regulatory bodies and safeguard the health of the population while ensuring the authenticity of milk as a widely consumed food product.

It is also our intention to make the sampling and testing methodology as scientific and impartial as possible. Consumers must be aware of these potential adulterants and support efforts to improve food safety standards.

Scope of the survey

The goal of the survey was to give the consumers birds’ eye view of the quality of milk available in the Imphal area. It will also lay the foundation for faster surveillance and deeper study of the quality of milk and other foods. The scope of the present study includes i) detection of presence detergent and starch as possible adulterants in milk ii) to determine the density of milk which in turn determines the degree of water added to pure milk.

Sampling and data

Samples were collected from different spots within Imphal during the period of September, 2024. Every possible measure was adopted to ensure the integrity of sampling. All records are maintained. Sl. No. 4 and 5 are not brand names but their original source as told by retailers.

To detect detergent in milk, start by adding 7.5 ml of methanol to 2.5 ml of milk. Methanol is used to help dissolve potential detergent residues in the milk. After adding the methanol, thoroughly mix the samples and then filter to remove any solid particles. Take 2 ml of the filtered liquid for further testing.

Next, add 2 ml of methylene blue solution to the filtrate and shake vigorously. Methylene blue is a dye that binds to certain chemical compounds, making them easier to identify. Then, add 4 ml of chloroform to the solution and shake well again. Chloroform helps to extract the methylene blue-detergent complex into a distinct layer.

The presence of detergent in milk is indicated by the formation of a darker blue color. The deeper the blue shade, the higher the concentration of detergent in the sample. If no significant color change is observed, the milk sample is unlikely to be adulterated/ contaminated with detergent. This simple yet effective test offers a way to quickly determine the presence of harmful detergents, ensuring that the milk is safe for consumption.

Starch

To detect starch in milk, a specific chemical reaction involving iodine is required. This reaction interacts with starch molecules.

To carry out the test, 4 ml of each milk sample is placed in test tubes and heated in a boiling water bath until they reach boiling point. This ensures that any starch present will interact with the chemicals added later. After boiling, the samples are cooled under running tap water to bring them back to room temperature.

Once cooled, 10% acetic acid is added to each sample. Acetic acid helps to break down any complex molecules that may interfere with the test. Following this, 0.2 ml of iodine solution is added to the milk samples. Iodine reacts with starch, forming a blue or grey-colored compound.

The results are visible almost immediately. If the milk sample turns yellow, it indicates the absence of starch, meaning the milk is pure. However, if the sample turns grey, it suggests the presence of starch, confirming adulteration.

This method is both simple and reliable, providing a quick way to assess whether milk has been tampered with. By using iodine’s interaction with starch, this test can help ensure that milk being consumed is free of additives that alter its nutritional properties.

Milk density

The density or specific gravity of milk is a crucial indicator of its quality. Pure milk has a specific density that can change if adulterants, such as water, are added. The density can be determined using a lactometer, a specialized device designed for this purpose. The lactometer reading provides insights into whether the milk has been diluted or contains additional substances.

To determine the milk's density, a 50 ml measuring cylinder is filled with the milk sample. A calibrated thermometer is inserted into the milk to measure its temperature, as the temperature can affect the lactometer reading.

Validation

All tests are validated to ensure the methods elicit the desired response. For example, detergent is inten- tionally added to the sample and checked for response.

The survey results indicate that starch and detergent, two common milk adulterants, were absent in any of the tested samples. This suggests that, at least for the tested samples, these harmful substances are not being used in Imphal region, ensuring a level of safety for consumers.

The absence of starch and detergent is a positive indicator of the general quality of milk, but vigilance is still necessary for other adulterants.

However, the milk density test revealed a varying degree of density across the different samples. Kongpal Dairy, with a density of 1.020g/ml, exhibited the lowest density, which is an indicator of possible highest water dilution. The other samples, though not as diluted as Kongpal Dairy, still showed variation in density, which may impact the nutritional quality of the milk.

The significant variation in milk density calls for more stringent monitoring of milk quality, as dilution practices can affect both nutritional values and consumer trust.

This preliminary survey lays the foundation for ongoing, broader studies and more robust milk safety regulations in the region, aimed at protecting public health.

Further studies should explore other possible adulterants and involve a larger sample size to comprehensively assess the milk quality across more diverse sources within Imphal. Establishing a regular surveillance program is essential to ensure consistent quality standards and to safeguard consumer health.