A Simple Kitchen Housewife Method to Determine the Amount of Sugars in a Drink

 

A friend of mine, Mr. Leo Nathan innocently sent me this video through a WhatsApp chat, and I am sure he does not know what this experiment was all about?  Neither could I.  

https://www.youtube.com/watch?v=M-KopIH3zAY

At first, I could not understand what the experiment was all about. She used two cans of gas to freeze a can of Coca-Cola. Then she allowed it to catch fire before adding an entire bag of baking powder onto it before putting a lot of new batteries onto the jar and so on. 

Finally, the experiment ended with some white dry powder without any water or liquid coming out from the can after she opened it. I was quite confused with her “experiment” as I did not know what the experiment was all about, her objective of doing the experiment, or what she was trying to prove?

Then another lady friend Ms Violet Ho, a former schoolmate of mine told me the lady in the video was trying to show there was a lot of sugar in a can of drink but was unable to figure out where the water in the can went after the can was opened?

I then thought of this, only to realize it was some trick. They may have opened the bottom of the can, drain out all the content there, add some white powder or sugar into the empty can, sealed the bottom before conducting the ‘magic show’

Obviously, it was a scam out to swindle viewers into believing that was the way to demonstrate the presence of high sugar content in that can of drink. Following that there were also doubts by others. Hence, I decided to write this article to explain to which I dedicate this article to Mr. Leo Nathan and Ms. Violet Ho.

Allow me to teach viewers and readers how to calculate the amount of sugars and other substances inside any drink that can be calculated without needing all those “magic show” shown by the lady, or needing an analytical chemical laboratory. Anyone can do this in his own kitchen if he has a small food weighing machine that gives measurements in grams and some kitchen measuring vessels that gives the volume in millilitres or ml.

First, take a bottle or can or bottle of any drink of a known volume, let’s say 250 ml. You need only take out a small amount of its volume, say one tenth of the amount (25 ml) or even less.

Next, take a cup and weigh it.  Then pour out 25 ml. of the drink into the cup. Weigh the cup together with the 25 ml of the drink inside.  Then subtract the weight of the cup. This should give the weight of the drink.

You may expect the drink to be 25 gm. since the density of water is 1 g / ml.  But no. There is sugar and other food additives inside.

 So, the weight of the drink should be more than 25 g even though the volume of the drink (water) is the same at 25 ml.  

Another way of putting this is, if we weigh out 25 ml of water, we expect the weight to be 25 gm. since the density of water is very nearly 1000 kg per cubic metre (1 gm per ml). The density of water varies only very slightly with temperature as water contracts when cooled. At 4 degrees Celsius it is almost 1 gm / ml. We can safely use the density of water as 1000 kg / cubic metre or 1 g per ml.

But if we now add, let us say 5 gm of sugar into the 25 ml of water, it will now weigh 5 + 25 = 30 gm. The volume of water is not affected by what is dissolved inside.

This is because the sugar that is dissolved into the water occupies the vast spaces between the water molecules. These intermolecular spaces of water increase with temperature allowing more sugar to be dissolved as the temperature increases until it reaches saturation point when no more sugar can be dissolved after all the intermolecular spaces between the water molecules have been occupied by molecules of sugar and other substances dissolved in the drink.   In other words, the solubility of sugar increases with temperature 

Hence if we take 25 ml. sample of the drink and found it weighs 30 g instead of 25 g, remembering that the density of water is 1 g / ml. then the extra 5 g. must be due to all dissolved substances, principally sugars inside the drink

We can now calculate how much sugar plus other food substances was in the original 250 ml drink. This works to be:

 5 gm ÷ 25 ml sample × 250 ml = 50 g

For 100 ml of the drink, it is 5 ÷ 25 x 100 ml = 20 g

Hence, all we need is to pour out a known volume of any drink and weigh it. Any extra weight (1 ml = 1 g) registered is just due to sugars and all other added soluble substances in it.

So simple as that! We can clearly see no freezing, no fire, no baking powder, no battery, no extra cans...nothing is needed here.

We did it by taking only a small sample of the drink of a known volume and just weighing it. We then merely subtract the weight from the volume, and that’s it, giving us the weight of the sugars plus other substances dissolved in it.  After measuring and weighing, we still get back the original volume of the drink.  Nothing is wasted or destroyed. There was no freezing or boiling even.

The only disadvantage we need to assume the extra weight was principally sugar. In many ways this is true with all sugary drinks

Of course, we can do it another way by taking a sample of the drink of known volume, then distilled or boil off all the water, and weigh the residue left, and from there we can calculate the concentration of sugar and other dissolved substance in it and express it in the same way as in a 100 ml. Using this second method we can look and examine the residue left to see if sugar is the major ingredient which is not possible with the first method by just looking at the weight difference. We can even taste the residue if it is sugar. But this method involves using heat, distillation or boiling which are all unnecessary. Then after boiling, we cannot get back what has already been boiled off and be content with what is left.

What we want to do, is to do it in the simplest and in the least destructive way possible so that we can get back the drink and everything.

This practice in chemistry is also the same as what we do in the practice of medicine. As doctors, we want to be as least destructive and invasive as possible to the patient.  We shall describe this practice in medicine shortly.

This method gives us a good estimate how much sugar was there in any drink without considering other food additives like colour and flavouring agent that were also present.  This method can be done by anyone at home in a kitchen.  No license for practicing chemistry is needed here. We shall talk about this later.

However, if we want analytical precision how much other substances were also present in a drink or any food sample, we need to send it to an analytical chemical laboratory or a food quality control laboratory where they have qualified experts in chemical analysis and sophisticated instruments there such as High-Performance Liquid Chromatography (HPLC), spectrophotometers of various kinds and types and even nuclear magnetic resonance spectroscopy.

Alternatively, sugars may also be determined by using a small hand-held refractometer, or by calorimetry. We can also use titration method as in the classical Lane-Eynon method with a burette containing the reducing sugars and titrating the amounts in a flask containing a known amount of boiling copper sulphate solution using methylene blue as an indicator for endpoint.

Sugars may also be determined by other chromatographic procedures besides HPLC, such as using gas chromatography- flame ionization detection (GC-FID), liquid chromatography-borate complexes (LC), high performance liquid chromatography-ethylenediamine derivatives (HPLC-EDA), high performance liquid chromatography-p- aminobenzoic acid derivatives (HPLC-p-AMBA), and high-performance anion, etc.

Perhaps we may also use column chromatography to separate the sugars from other undesirable substances we have no interest in measuring. But we need to find a suitable absorbing and separation medium for the chromatographic column for ion and resin exchange, or maybe we can use silica gel and water as an eluent. What we chose depends on what other substances are also present in the drink other than sucrose.  

It all depends on the skills of the chemical analysts, his training, qualifications and experience, his discretion, and the lab.  facilities available to him.

However, these days, analytical chemistry has become so advanced that a chemist analysing a substance can detect substances down to just ppm (parts per million) or even ppb (parts per billion.

They may need only a few drops or a tiny sample in micrograms or even in nanograms such as a fragment of DNA for sequencing. We can do that. That’s not a problem for us.  

But for ordinary people, we merely make it very simple, convenient, and easy for them using what is available in their kitchen as most people are not scientists or analytical chemists working in a sophisticated analytical laboratory.  We don't expect them to have these.

Using this kitchen method, we can only determine the total substances dissolved inside. But if we want only the sugar content then we need to send the sample to an analytical laboratory where they need to isolate the rest of other substances from the sucrose.

As scientists we try to be as less destructive as possible unlike that lady using all kinds of "magic" and tons of materials including several new batteries just to show some white substance inside that can.

Many people may be interested in finding out only the amounts of sugars in a drink or in the food they eat for various health reasons we shall not go into them.  An estimate using the kitchen method is more than good enough. Furthermore, they do not need a qualification in chemistry or a license to practise chemistry in this country.  They only need a kitchen with a small weighing scale and some measuring cups or jugs.

The practice of chemistry in Malaysia is a certified profession by law. Its practice is empowered by the Chemist Act 1975 and is controlled by the Malaysian Institute of Chemistry to regulate the practice of chemistry. Just like medicine, the practice of nutrition, dietetics are also regulated by law in this country like other professions such as pharmacy, optometry, law, engineering…etc

Title designations such as doctor, nutritionist, chemist are protected titles and are licensed. Not everyone can use these professional titles except those qualified, and their qualifications must be registrable with their various councils and regulatory bodies.

On the issue mentioned earlier, a medical doctor practices in the same way as an analytical chemist, both trying to be as little destructive and invasive as possible during an examination. This also applies to all professional scientists and researchers.

For instance, in the practice of medicine, we try to use as simple as possible an examination for the diagnosis of a disease. The simplest method is just to listen carefully to what the patient tells us. We then analyse what they tell us to try and come to a diagnosis if possible. If not certain, we just ask questions, take their medical history, and ask more questions, and just listen carefully to what they tell us, while analysing the information for tell-tale signs.

If a doctor is not sure, he may look at the presentations such as signs and symptoms to try to diagnose or differential diagnosis from the other diseases as sometimes diseases mimic each other in their presentations.  If a doctor is still unsure, he may do a clinical examination by palpating, percussing with the fingers, or auscultate (listen) for body sounds with a stethoscope such as listening to the various types of murmurs in the heart, their pitch, nature and loudness.

He may listen to breath sounds for crepitations, rales, bubbling, stridor, rhonchi, wheezes, vascular murmur or bruits in blood vessels that may be stenosed (narrowed), or bowel sounds for intestinal hurry or gasses, etc, etc.

By then, he would already be able to come up with a diagnosis with at least 70 % accuracy if the doctor is a good diagnostician.  But if he is still uncertain due to multiple complications with other disorders having the same features such as signs and symptoms, he may request for a laboratory support such as haematological, microbiological, serological, immunological, biochemical, urinary examinations or even requesting genetical and molecular cellular assays…etc.

 He may also decide on radiological examinations such as x-rays, ultrasonography, CT, MRI, PET or even nucleotides examinations to confirm a diagnosis. Some of these investigations can be invasive if not destructive. But we try as best as possible to be conservative, not invasive, least of all - destructive.

Hence, we can see a doctor is like an analytical chemist who initially uses as simple as possible a method to derive a finding or a diagnosis.

Like medicine, the practice of chemistry is a registered profession under the Chemist Act 1975. A chemical analyst needs to be qualified in chemistry and his degree must be registrable under the Act before he is allowed to practise, analyse, and sign an analytical report or give evidence before a court of law just like in medicine.

The same with the practice of nutrition or dietetics. Both are also registered professions that require a licence to practice, and they have their codes of professional ethics.

But what we describe here using the kitchen method does not require a practicing license in chemistry or any qualification except just follow the very simple procedure I gave above.

Hope this helps

jb lim