FIELD OF THE INVENTION
The present invention relates to a method for detection of sorbitol in milk and a system for detecting
the same thereof. The method is economical, easy to use, requires significantly less infrastructure,
quick, and effective.
BACKGROUND OF THE INVENTION
Milk has long been known as a source of various nutrients essential for a proper growth in human
beings. It is a great source of energy, protein, carbohydrate, fat, vitamins, etc. The absence of these
nutrients might hinder the growth of a person and be potentially threatening in the long term. Apart
from being used as it is, milk is also the raw material for various dairy products, which form an
essential part of our daily routine.
The importance of milk and milk derived product or dairy product for a developing country is much
more than that for a developed country. The developing and under-developed countries are more
concerned towards providing quality milk to their population. Thus, it becomes a primary concern
for all the nations to maintain a check on the purity of milk. Although, the governments are trying
their best to maintain a check on the quality of milk, yet there are many chemicals and artificial
substances being used to adulterate milk, which deteriorate the quality and cause harmful effects.
In order to fulfil the ever-growing demand of milk, the suppliers have found it profitable to
adulterate milk with chemicals having harmful effects. There is no specific time of the year when
adulteration is high or less. Logically being demand based, the adulteration is on its peak during
summer and festive seasons. Milk, being a white liquid, is easily adulterated with chemicals which
do not alter its appearance. Such chemicals include urea, cane sugar, starch, saccharin, polyol (such
as sorbitol), gelatin, foreign fat, etc. These chemicals are used for artificial sweetening, as a source
of primary milk solid not fat (SNF) and milk fat, etc. These chemicals might cause gastrointestinal
complications, food poisoning, impairment, cardiac issues, cancer, etc.
Of the above-mentioned chemicals, polyol, especially sorbitol, is recent and now extensively being
used as milk adulterant. Sorbitol is a sugar alcohol and its addition in milk is merely a compromise
with the nutrients. Hence, it is important to avoid its consumption.
3
Moreover, existing methods for detection of sorbitol such as HPLC-ELSD, biosensors and NIR
technology require huge investment, need infrastructure and expertise to operate.
Thus, there is an existing need of a method which can detect sorbitol in milk in simple, quick and
economical manner. Also, an efficient method is required which is easy to operate without requiring
much expertise and easy to train people. Keeping in mind, the existing problems associated with
the known methods of detecting sorbitol in milk, the present inventors have developed an improved
method of detecting sorbitol in milk which is simple, quick, economical and requires significantly
less infrastructure.
Hence, the aim of the present invention is to provide a quick, effective and economical method for
detection of sorbitol in milk, at field level of procurement. This method is easy to use, requires
significantly less infrastructure, easy to operate without requiring much expertise, easy to train
people and quick in result.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide an improved method of detection of sorbitol
in milk and a system for detecting the same.
Yet another object of the present invention is to provide a method that detect sorbitol in milk at field
level of procurement.
Yet another objection of the present invention is to provide a method which is simple, quick, and
economical.
Yet another objection of the present invention is to provide a method which requires significantly
less infrastructure and easy to operate.
SUMMARY OF THE INVENTION
The present invention provides a method for detection of sorbitol in milk and a system for detecting
the same thereof. The method is economical, easy to use, effective, requires significantly less
infrastructure, quick, effective and detect sorbitol in milk at field level of procurement. The method
is carried out in the system which comprises a milk sample collector (100), first boiler (101), acid
4
storer (102), coagulator (103), filter (104), second boiler (105), buffer solution vessel (106),
complexing agent vessel (107), filtrate mixture vessel (108) and vortex mixer (109).
BRIEF DESCRIPTION OF FIGURES
Further aspects and advantages of the present invention will be readily understood from the
following detailed description with reference to the accompanying figures. The figures together
with a detailed description below, are incorporated in and form part of the specification, and serve
to further illustrate the embodiments and explain various principles and advantages, in accordance
with the present invention wherein:
Figure 1 represents a flow diagram of the method for detection of sorbitol in milk.
Figure 2 represents a system for detection of sorbitol as per the method depicted in Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
While the invention is subject to various modifications and alternative forms, specific embodiment
thereof has been shown by way of example in the figures and will be described below. It should be
understood, however that it is not intended to limit the invention to the particular forms disclosed,
but on the contrary, the invention is to cover all modifications, equivalents, and alternative falling
within the scope of the invention.
It is to be noted that a person skilled in the art can be motivated from the present invention and
modify the various constructions of assembly, which are varying from method to method and
system to system. However, such modifications should be construed within the scope and spirit of
the invention. Accordingly, the drawings are showing only those specific details that are pertinent
to understanding the embodiments of the present invention so as not to obscure the invention with
details that will be readily apparent to those of ordinary skill in the art having benefit of the
description herein.
The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a nonexclusive
inclusion, such that a method, system that comprises a list of components does not
include only those components but may include other components not expressly listed or inherent
to such method or system. In other words, one or more elements in a method or system proceeded
5
by “comprises… a” does not, without more constraints, preclude the existence of other elements or
additional elements in the method or system.
Accordingly, the present invention relates to a method for detection of sorbitol in milk. Sorbitol
(C6H14O6), also known as glucitol, is a white crystalline solid or liquid having a sweet taste. It is
basically a sugar alcohol, which metabolizes slowly in the human body. Sorbitol finds its application
as a sweetener, laxative, for medical purpose, healthcare, food and cosmetics. It is also used as a
bulking agent, humectant, texturizing agent, stabilizer, etc.
Sorbitol is half as sweet as sucrose. Thus, it is used as an artificial sweetening agent in milk. Apart
from this, sorbitol is also used, in combination or alone, to increase the SNF content in the milk.
Easy availability and cheap cost of sorbitol are other factors which render it to be used as an additive
in milk. Recent studies conducted by various government and non-government organisations
confirm the presence of sorbitol in milk for the reasons mentioned hereinabove.
The amount of sorbitol added in the milk generally ranges from 0.06% to 1.3% by volume of milk.
It is difficult to detect such low concentrations of adulterants in milk. Nevertheless, they can be
detected using expensive techniques available in the market, as already discussed hereinabove.
Thus, the present invention hereinbelow discusses an economic, quick and effective method for
detection of sorbitol in milk.
As shown in Figures 1 and 2, the method for the detection of sorbitol requires the collection of 20-
40mL of milk sample in a milk sample container (100). The milk sample can be collected from any
source such as but not limited to point of supply, distribution centres and collection centres. The
milk sample is then boiled in a first boiler (101) at a temperature range of 100˚C-110˚C until the
level of milk starts rising. An acid or inorganic acid solution is added to the boiled milk sample in
a coagulator (103). The organic or inorganic acids can be chosen from a group comprising of
sulphuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid and lactic acid.
An acid solution is prepared by adding 1-10% by volume of acid in distilled water in an acid storer
(102), thereby resulting in a dilute acid solution. The dilute acid solution is now added in an amount
ranging from 0.5-5.0mL in the boiled milk sample. The addition of acid results in coagulation of
the boiled milk sample to produce a coagulated sample of milk in the coagulator (103).
6
The coagulated sample obtained hereinabove is now passed through a filter (104) comprising
Whatman filter paper of grade 1. Now, 1-5mL of the filtrate obtained is taken in a second boiler
(105) and boiled for 1-3minutes at a temperature range of 98˚C-102˚C.
A buffer solution comprising 1-10% by volume of at least one of ammonia, sodium carbonate, boric
acid, potassium chloride and sodium hydroxide is prepared in distilled water in a buffer solution
vessel (106). The buffer solution is added to the boiled filtrate in the range of 0.5-1.0mL in a filtrate
mixture vessel (108). A complexing solution having 1-2% by volume of at least one of the salts
selected from the group comprising of copper sulphate, zinc chloride, ferrous sulphate, ferric
chloride, chromium nitrate, stannous chloride, cobalt chloride, cobalt sulphate, nickel (III) chloride
and nickel sulphate is prepared in distilled water in a complexing solution vessel (107). Sorbitol
reacts with the metal ions of these salts and results in formation of their complexes in alkaline and
acidic aqueous solution, thereby forming mononuclear and oligonuclear complexes. The
complexing solution is added immediately after the addition of buffer solution and in concentration
ranging from 1-10wt% to obtain the filtrate mixture in the filtrate mixture vessel (108). The filtrate
mixture comprises of the boiled filtrate, buffer solution and complexing solution.
The filtrate mixture obtained hereinabove is now mixed in a vortex mixer (109). The filtrate mixture
is kept in the vortex mixer (109) for a period of 30-40 seconds and thereafter in water-bath
maintained in a temperature range of 25˚-35˚C for 10-15minutes. The colour of the gel depends
upon the concentration of sorbitol in the milk sample and it varies from straw yellow depicting high
concentration of sorbitol in milk to light brown depicting low concentration of sorbitol in milk. In
addition to this, the viscosity of gel also increases with concentration of sorbitol. The higher the
content of sorbitol in milk, solid is the gel formed.
The method of the present invention, as described hereinabove, detects the presence of sorbitol in a
very quick, effective and economic manner. The parameters of the method are easily maintainable
and do not require any expertise in performing the same. The present method can detect the presence
of sorbitol in the range of 0.2-1.5wt% in milk. However, the detection of sorbitol beyond 1.5wt%
is difficult to estimate.
As shown in Figure 2, the system of the present invention comprises a milk sample collector (100),
first boiler (101), acid storer (102), coagulator (103), filter (104), second boiler (105), buffer
solution vessel (106), complexing agent vessel (107), filtrate mixture vessel (108) and vortex mixer
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(109). Milk sample is collected in the milk sample collector (100) and boiled in the first boiler (101).
The acid storer (102) supplies the acid for coagulation of the milk sample in the coagulator (103).
The coagulated milk from the coagulator (103) is now passed through the filter (104) comprising
Whatman filter paper of grade 1. The filtrate obtained is sent to the second boiler (105), where it is
boiled in presence of water. Buffer solution and complexing agent solution are added from the
buffer solution vessel (106) and complexing solution vessel (107) to the filtrate in the filtrate
mixture vessel (108) to obtain a filtrate mixture. The filtrate mixture is now sent to the vortex mixer
(109) where a solid gel is formed, which confirms the presence of sorbitol in the milk sample. The
system disclosed hereinabove is easy to use, requires very less space and can be easily operated
without requiring much expertise.
Accordingly, the main embodiment of the present invention is to provide a method of detection of
sorbitol in milk, comprising the steps of:
a. collecting 10 mL to 60 mL milk in a sample container (100);
b. boiling the milk in the first boiler (101) at a suitable temperature until the level of
milk starts rising to obtain boiled milk;
c. adding an acid or inorganic acid solution to the boiled milk of step (b) in a coagulator
(103) to produce a coagulated milk;
d. passing the coagulated milk of step (c) through a filter (104) to form a filtrate;
e. taking the filtrate of step (d) in a second boiler (105) and boiling the filtrate for 1 to
3 minutes at a temperature range from 90 oC to 120 oC to form a boiled filtrate;
f. adding the buffer solution in the range of 0.1 to 5.0 mL to the boiled filtrate of step
(e) followed by addition of complexing solution in the concentration range of 1 to
10 wt% to obtain the filtrate mixture in a filtrate mixture vessel (108);
g. mixing the filtrate mixture of step (f) in a vortex mixer (109) for a time period of 20
to 80 seconds and in water bath maintained in a temperature range of 15oC to 50oC
for 10 to 15 minutes to form a gel.
In another embodiment of the present invention, the amount of milk in step (a) is in the range of 20
mL to 40 mL.
8
In another embodiment of the present invention, the temperature of step (b) is in the range of 90oC
to 140oC, preferably in range of 100oC to 110oC.
In another embodiment of the present invention, the organic or inorganic acid can be selected from
a group comprising sulphuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid and lactic
acid.
In another embodiment of the present invention, the acid is citric acid.
In another embodiment of the present invention, the acid solution of step (c) is prepared by adding
1 to 10% by volume of acid in distilled water in an acid storer (102) resulting in a diluted acid
solution.
In another embodiment of the present invention, the filter of step (d) is Whatman filter paper of
Grade 1.
In another embodiment of the present invention, the temperature of step (e) is in the range of 98 oC
to 102 oC.
In another embodiment of the present invention, the amount of buffer of step (f) is in the range of
0.5 to 1.0 mL.
In another embodiment of the present invention, the complexing solution of step (f) comprising 1-
2% of atleast one salt prepared in distilled water in a complexing solution vessel (107).
In another embodiment of the present invention, the salt is selected from the group comprising of
copper sulphate, zinc chloride, ferrous sulphate, ferric chloride, chromium nitrate, stannous
chloride, cobalt chloride, cobalt sulphate, nickel (III) chloride and nickel sulphate.
In another embodiment of the present invention, the salt is ferrous sulphate.
In another embodiment of the present invention, the time period of step (g) is in the range of 30 to
60 seconds.
In another embodiment of the present invention, the temperature of step (g) is in the range of 25oC
to 35oC.
In another embodiment of the present invention, the gel viscosity increases with concentration of
the sorbitol in milk.
9
In another embodiment of the present invention, the method can detect the presence of sorbitol in
the range of 0.2 - 1.5wt% in milk.
In another embodiment of the present invention, the method is carried out in the system comprises
a milk sample collector (100), first boiler (101), acid storer (102), coagulator (103), filter (104),
second boiler (105), buffer solution vessel (106), complexing agent vessel (107), filtrate mixture
vessel (108) and vortex mixer (109).
In nutshell, the present invention has various advantages such as but not limited to ease in operation,
low cost, quick detection of sorbitol, requirement of low maintenance and installation area.
EXAMPLES
The invention is illustrated by the following example(s) which are only meant to illustrate the
invention and not act as limitation. All embodiments apparent to a process there in the art are
deemed to fall within the scope of the present invention.
EXAMPLE 1
Table 1. Different samples tested.
Sample no. Test Sample Sorbitol content (%
by volume)
A Adulterant free milk --
B Spike 1 0.1%
C Spike 2 0.2%
D Spike 3 0.3%
E Spike 4 0.4%
F Spike 5 0.5%
G Spike 6 0.8%
20mL of each sample of milk is pipetted out in a beaker and boiled. 0.6mL of 10 % citric acid is
used for coagulating the boiled milk. The boiled milk is then filtered through the Whatman filter
paper of grade 1 and the filtrate is collected. 1mL of filtrate is taken in a test tube and boiled in
water-bath for 1minute. Now, 0.8mL of 10% alkaline buffer solution and 0.2mL of 2.5% ferrous
sulphate (FeSO4) are added. The obtained filtrate mixture is now mixed in a vortex mixer for
10
30seconds and thereafter kept in water-bath maintained at 30°C for 10 minutes. Gel-like formation
occurs, which is removed and observed after 5 minutes for best results.
All the sample and spiked samples were treated in the same manner and tested for the presence of
Sorbitol in milk.
Table 2. Results
Sample
No.
Test Sample Sorbitol
content (% by
volume)
Observation
A Adulterant free milk -- No Change
B Spike 1 0.1% Slight adherence of gel on the test tube wall
C Spike 2 0.2% Adherence of gel on the test tube wall
D Spike 3 0.3% Formation of gel
E Spike 4 0.4% Formation of gel
F Spike 5 0.5% Formation of solid gel
G Spike 6 0.8% Formation of solid gel
As evident from the above table, an increase in sorbitol content results in an increase in the gel
viscosity. This can be observed from the fact that sample D having only 0.3% of sorbitol results in
gel-like product, while sample G with 0.8% sorbitol gives a solid gel.
The present invention can detect the presence of sorbitol irrespective of the fact that other chemical
additives are present in the sample. The results were checked and compared for presence of sorbitol
with HPLC. HPLC with ELSD was optimised for simultaneous determination of Glucose, lactose,
lactulose, fructose, sorbitol, maltodextrin and sucrose in milk. The analysis was carried out on a
Waters 5μ NH2 100A column (250 mm × 4.60 mm, 5 micron) with gradient elution of acetonitrile:
water. Drift tube temperature of the ELSD system was set to 60°C and nitrogen flow rate was 45
psi. The regression equation revealed good linear relationship 0.99 within test ranges. The limits of
detection (LOD) and quantification (LOQ) were in the range of 20 ppm and 100 ppm respectively.
The proposed HPLC–ELSD method was validated for quantification of sugars in milk and results
were satisfactory.
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The inventors have been working to develop the method and system of the present invention, so
that the advantage can be achieved in an economical, practical, and facile manner. While preferred
aspects and example configurations have been shown and described, it is to be understood that
various further modifications and additional configurations will be apparent to those skilled in the
art. It is intended that the specific embodiments and configurations herein disclosed are illustrative
of the preferred nature of the invention, and should not be interpreted as limitations on the scope of
the present invention.
LIST OF NUMERALS
100 Milk sample collector
101 First boiler
102 Acid storer
103 Coagulator
104 Filter
105 Second boiler
106 Buffer solution vessel
107 Complexing solution vessel
108 Filtrate mixture vessel
109 Vortex mixer
UTILITY OF THE INVENTION
The present invention provides a method for detection of sorbitol in milk and a system for detecting
the same thereof. The method is economical, easy to use, cost effective, and industrially applicable.

WE CLAIM:
1. A method of detection of sorbitol in milk comprising the steps of:
a. collecting 10 mL to 60 mL milk in a sample container (100);
b. boiling the milk in the first boiler (101) at a suitable temperature until the level of
milk starts rising to obtain boiled milk;
c. adding an acid or inorganic acid solution to the boiled milk of step (b) in a coagulator
(103) to produce a coagulated milk;
d. passing the coagulated milk of step (c) through a filter (104) to form a filtrate;
e. taking the filtrate of step (d) in a second boiler (105) and boiling the filtrate for 1 to
3 minutes at a temperature range from 90 oC to 120 oC to form a boiled filtrate;
f. adding the buffer solution in the range of 0.1 to 5.0 mL to the boiled filtrate of step
(e) followed by addition of complexing solution in the concentration range of 1 to
10 wt% to obtain the filtrate mixture in a filtrate mixture vessel (108);
g. mixing the filtrate mixture of step (f) in a vortex mixer (109) for a time period of 20
to 80 seconds and in water bath maintained in a temperature range of 15oC to 50oC
for 10 to 15 minutes to form a gel.
2. The method as claimed in claim 1, wherein the amount of milk in step (a) is in the range of
20 mL to 40 mL.
3. The method as claimed in claim 1, wherein the temperature of step (b) is in the range of
90oC to 140oC, preferably in range of 100oC to 110oC.
4. The method as claimed in claim 1, wherein the organic or inorganic acid can be selected
from a group comprising sulphuric acid, nitric acid, hydrochloric acid, acetic acid, citric acid
and lactic acid.
5. The method as claimed in claim 4, wherein the acid is citric acid.
6. The method as claimed in claim 1, wherein the acid solution of step (c) is prepared by adding
1 to 10% by volume of acid in distilled water in an acid storer (102) resulting in a diluted
acid solution.
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7. The method as claimed in claim 1, wherein the filter of step (d) is Whatman filter paper of
Grade 1.
8. The method as claimed in claim 1, wherein the temperature of step (e) is in the range of 98
oC to 102 oC.
9. The method as claimed in claim 1, wherein the amount of buffer of step (f) is in the range
of 0.5 to 1.0 mL.
10. The method as claimed in claim 1, wherein complexing solution of step (f) comprising 1-
2% of atleast one salt prepared in distilled water in a complexing solution vessel (107).
11. The method as claimed in claim 10, wherein the salt is selected from the group comprising
of copper sulphate, zinc chloride, ferrous sulphate, ferric chloride, chromium nitrate,
stannous chloride, cobalt chloride, cobalt sulphate, nickel (III) chloride and nickel sulphate.
12. The method as claimed in claim 11, wherein the salt is ferrous sulphate.
13. The method as claimed in claim 1, where time period of step (g) is in the range of 30 to 60
seconds.
14. The method as claimed in claim 1, wherein the temperature of step (g) is in the range of
25oC to 35oC.
15. The method as claimed in claim 1, wherein the gel viscosity increases with concentration of
the sorbitol in milk.
16. The method as claimed in claim 1, wherein the method can detect the presence of sorbitol
in the range of 0.2 - 1.5wt% in milk.
17. The method as claimed in claim 1, wherein the method is carried out in the system comprises
a milk sample collector (100), first boiler (101), acid storer (102), coagulator (103), filter
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(104), second boiler (105), buffer solution vessel (106), complexing agent vessel (107),
filtrate mixture vessel (108) and vortex mixer (109).