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Spoiled Milk Detector

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Postby aarthidhar » Fri May 21, 2004 12:07 pm

Have a look at this article
Source: http://www.science.edu.sg/ssc/events.js ... 68&cat=330
Article:
[Project ID: BC 03]
Bad Milk Indicators

Chong Mui Fong, Sim Wen Hui (Victoria Junior College
When milk turns bad, the consumer wants the carton to inform them so, even before the primitive smelling and tasting. Also, wastage can be reduced if the consumer knows when the milk exactly spoils instead of following the designated expiry date. Hence, this leads us to a search for a natural pH indicator for milk spoilage. pH of fresh milk decreases from approximately pH 6.8 to pH 6.2 before it curds. The curdling stage deemed the milk unfit for consumption. Next, it involves finding a source of a suitable natural indicator that can be safely incorporated into the milk carton during the manufacturing process. Anthocyanins, pigments that are found in many vegetables and fruits and changes colours with pH, are favourable choices.
Through a series of experiments, we are able to isolate the anthocyanins from red radish skins and the red capsicum. Mixing the two extracts gives an indicator solution which shows two apparent colours in fresh milk and spoilt milk. Next, we came up with a product design that enables the consumer to track freshness of milk. This involves incorporation of a dropper-like instrument containing the indicator solution, which is able to suck in milk in a single direction from the carton with a squeeze and a colour chart printed on the carton for comparison. Simple to operate, low-cost, and totally safe from contamination, its popularity will be witnessed in due time
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Re: Spoilt milk detector

Postby Steve » Fri May 21, 2004 3:19 pm

Rishi wrote:That is quite acceptable.

In all this one point not seriously looked at is that whatever the sensing mechanism it has to be in continuous contact with the milk. The sensor should not leach anything toxic into the milk and it has to be stable in continuous contact with an essentially water based medium. SInce it goes on a commodity like milk it should be low cost..

Rishi

If I'm not mistaken, for something to smell there need to be small particles in the air. So as sour milk smells, maybe it would be possible to come up with something sensitive enough to change color even if it's not covered with milk (but just "breathing" the same air)? :-?
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Soured milk

Postby Rishi » Fri May 21, 2004 6:51 pm

Dear Noel,
Have not seen it better expressed. That is exactly my feelings too, with bells on.

Putting all ideas together, the best solution seems to be to find a non-toxic pH sensitive colourant that can be added to the milk itself. This will be one hue in sweet milk and another in sour milk. We should check out phenalphthalein. It is used in pharmaceutical preparations. It does change colour with pH.

It should be a simple matter to check it out if the pH range is what we want.

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Spoiled milk detector

Postby MissPlayful » Sun May 23, 2004 12:28 pm

Steve says "If I'm not mistaken, for something to smell there need to be small particles in the air. So as sour milk smells, maybe it would be possible to come up with something sensitive enough to change color even if it's not covered with milk (but just "breathing" the same air)?"

Near the top of the carton where the airspace is, we could have a small "window" in the carton, composed of two layers: the inside layer of this window is made of a substance that lets gas molecules through it but does not let any liquid molecules through it. The outside layer of this window is made of a substance that changes colour when it detects gas molecules given off by milk that is starting to sour. This would keep the colour-changing chemicals completely separate from the milk.
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Postby Rishi » Sun May 23, 2004 5:17 pm

MissPlayful,
A neat trick that! A semi-permeable membrane would be a way around the problem. There is a catch though. The human nose can detect just 300 molecules. A dog can sense much less. There are very few chemicals that work at anywhere near that level. There are very expensive equipment that can do the job.

However, since we only need an OK or NOK your idea may work once a sensor chemical is located. Something else can be done though. Have a bacteria filter(This is also a semipermeable membrane, which lets a gas or liquid to seep through but stops bacteria) at the top of the carton. Tip over the carton, while keeping a test strip in contact with the filter. A drop or two of the milk will seep through and show by the colour of the strip in contact what the scene inside is.

These test strips cost next to nothing and can be made available as a 'Book'. (Glaxo/Boots sell such pH sensing strips)

Thanks for a real lateral thinking idea.

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Spoiled milk detector

Postby MissPlayful » Tue May 25, 2004 10:45 am

I wonder if the electrical properties of milk change as it begins to go sour (eg its resistance to the flow of an electric current). It would probably be quite easy to incorporate two small electrode - tiny plates made out of some reasonably inert metal such as stainless steel - into the carton when it is manufactured. To test the milk, two terminals on a small electric measuring device could be touched to the outside surfaces of the two metal plates and the resistance of the milk measured. Alternatively, if you don’t mind a bit of dissolved metal in your milk, you could perhaps use the increasing acidity in the milk as it sours to generate a tiny electric current between two little plates of different metals, and that tiny electric current could be measured by a meter, or used to change the colour of a patch of chemical. Or how about this failsafe method. Build a small plug into the bottom of the carton, of a substance that is insoluble in fresh milk but dissolves in milk when it begins to go sour. When your milk starts to go off, the plug dissolves, all the milk drains out of the carton, and you are saved the embarrassment and discomfort of drinking sour milk! Simple really - I can't understand why this dissolving plug idea hasn't already been marketed. Finally, I do like the idea of a dye in the milk which turns green when the milk goes sour. Just make sure you turn the light on before you pour yourself a glass of milk. It's bad finding lumps in a glass of milk you've already half drunk, it would be a lot worse to discover the milk was a billious green!
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Re: Spoiled milk detector

Postby Steve » Tue May 25, 2004 11:25 am

MissPlayful wrote:It would probably be quite easy to incorporate two small electrode - tiny plates made out of some reasonably inert metal such as stainless steel - into the carton when it is manufactured.

As a European recycling fanatic I believe that a different approach would be preferrable - there are quite a number of countries where these cartons are collected and recycled - the metal plates would put an end to that. :-/
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Spoiled milk detector

Postby MissPlayful » Wed May 26, 2004 11:00 pm

Steve wrote "there are quite a number of countries where these cartons are collected and recycled - the metal plates would put an end to that." Good point, and I think this is easily solved. Firstly, I would be surprised if the carton recycling process doesn't include a range of steps to remove impurities eg the removal of ferrous objects using magnets. But in the unlikely event that metal objects are not removed in the recycling process, the electrodes could be made out of a material that dissolves during the process. I reckon if you used electrodes of two different substances that generated a tiny electric current when the milk started to acidify, you could use that current to turn on a tiny LED type light printed onto the outside surface of the carton, similar to the numbers on digital watches. (In fact you could have a scale of numbers one to ten - one is "beautiful", three is "may taste slightly off", ten is "it is strongly advised that you make out a will before drinking this!"). The detection unit would only cost a few cents perhaps. I wonder how much extra consumers would be prepared to pay to be able to see at a glance whether their milk was going sour. No more than a couple or a few of whatever are the smallest units in your currency I would say. Whatever system is used it will need to be very cheap.
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Postby Rishi » Thu May 27, 2004 2:24 am

Any method that uses metallic electrodes automatically means that the negative electrode dissolves. The milk will be contaminated with that metal, which could be toxic. In any case many may not be willing to take in this exttra metal unless this can be a metal like iron in which case one can say that the milk is enriched!

The cheapest and the most sensitive method will still probably be a colour change using a pH sensitive FDA permitted chemical, because of the very small doses needed.

However, all ideas must be discussed as they may be of use elsewhere.

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Postby mtd28student » Thu Jul 15, 2004 4:14 am

why not add an indicator to the milk (non toxic dye that changes colour with changing pH). It would go green when the milk changes it's pH level. All would be needed then would be a small clear window in the milk container. when the milk is green don't use it.
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Green milk

Postby MissPlayful » Fri Jul 16, 2004 10:53 pm

I like the idea in principle of putting a harmless dye in milk that turns green when the milk goes off, but I doubt if the public would accept the idea of putting dye into milk, I think they would rather take their chances. There is also the psychological effect to consider of pouring out a glass of milk and discovering it is green. Might put you off milk for life.
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Postby Rishi » Wed Jul 21, 2004 5:16 pm

Human beings are equipped with a perfectly sensitive nose that can detect 300 molecules, as well as a tongue with taste buds that can detect minuscule taste differences.

I do not want to be a spoilsport but sour milk is not a poison. Why not just sniff it first. If all seem well swirl a few drops around the tongue(Sort of tea tasting) and then drink it if it is not gone. If not alright what is in the mouth can be spat out.

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Postby sneezyalex » Sat Apr 02, 2005 3:56 am

How bout a chunk o meter! :-D :-B
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lol

Postby Fishy Bizniss » Sun Apr 10, 2005 8:03 am

sucks for you guys cuz if its past the exp. date ... you know what i do? ...haha throw it away!!! good solution wouldnt you agree?
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Postby sneezyalex » Mon Apr 11, 2005 2:17 am

No one sees the date. Put it in big bold letters on the sides! ;-D
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