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  • #16
    Originally posted by heks12 View Post
    Well for now I seem to have fixed the problem by just making less hot coffees than I usually do..so luke warm .
    Seems whatever causes this reaction problem is catalysed by hi temp milk..
    So for now its fixed, even tho i hate luke warm coffee.. might wait a few weeks and see if the milk season changes
    Bloody hell, spoke too soon. This mornings luke warm coffee separated, but just very slowly (10min). The process is obviously sped up depending on the heat of the milk. Very hot milk it is almost instantaneous. I watched the process slowly occur, I realised what is happening is that the actual foam goes hard and then starts to coagulate and sink into the coffee. So I don't think its the actual milk liquid that is curdling, it's the foam.

    Gonna experiment with the rinse aid idea now.
    For the person that asked, yes this was happening before the descale.

    Geeeeze.. I'd love a coffee right now..

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    • #17
      Originally posted by heks12 View Post
      Bloody hell, spoke too soon. This mornings luke warm coffee separated, but just very slowly (10min). The process is obviously sped up depending on the heat of the milk. Very hot milk it is almost instantaneous. I watched the process slowly occur, I realised what is happening is that the actual foam goes hard and then starts to coagulate and sink into the coffee. So I don't think its the actual milk liquid that is curdling, it's the foam.
      I think the clue is in that it suddenly started happening but does not all the time (80% of the time).

      Made one coffee yesterday which wad fine, made another with all the same ingredients amd it went bad. Mind boggling.
      Can you think of anything that might have changed when this started happening? Of the ones that don't curdle, is it always the first one? If so, it might suggest the thermoblock of the Gaggia Baby is overheating (faulty thermostat??).

      1. Does the milk separate if you make the coffee in a ceramic cup?
      If not, this would suggest the rinse aid problem that Okitoiki mentioned

      2. Does the milk separate if you just pour into a glass without any coffee in it? (similar to what Dragunov asked in post 4 but you didn't answer)

      If you are using a stainless jug for steaming, the milk is usually hot enough if you can hold the palm of your hand against the bottom of the jug for 3 seconds before it feels too hot.

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      • #18
        Originally posted by heks12 View Post
        Bloody hell, spoke too soon. This mornings luke warm coffee separated, but just very slowly (10min). The process is obviously sped up depending on the heat of the milk. Very hot milk it is almost instantaneous. I watched the process slowly occur, I realised what is happening is that the actual foam goes hard and then starts to coagulate and sink into the coffee. So I don't think its the actual milk liquid that is curdling, it's the foam.

        Gonna experiment with the rinse aid idea now.
        For the person that asked, yes this was happening before the descale.

        Geeeeze.. I'd love a coffee right now..
        Hi Heks

        I think posting a video will help all us "other CS'rs" to work it out.

        FWIW, I now think something is amiss with your machine, so I strongly recommend you try a different one. Even a $150 Breville can do a better job that you are currently managing, so I am sure you must be able to access something somewhere at or above that level.

        "Geeeeze.. I'd love a coffee right now..": I feel your pain, like probably every other CS: been there, done that, never want to do it again.

        Hope it sorts soon.


        TampIt

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        • #19
          Originally posted by TampIt View Post
          Hi Heks

          It is probably the change of season thing. Affects all milks for three weeks at the "cow end". The supply chain often takes longer. It usually only breaks down like that if it is hit with overly hot steam, only it always has a delayed reaction. The acid in the coffee tips it over the edge.
          Might be onto something there.
          I have noticed that the milk I have bought in the past few weeks has been noticeably less sweet (almost bordering on sour to my tastes). I have noticed it in bought coffees in years gone by also. Most noticable in milkier coffees. Luckily I have had no problems with curdling recently; although on the one occasion I did, the dairy put it down to possible problems in the cold supply chain. So that could be another contributing factor?

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          • #20
            Originally posted by Journeyman View Post
            Good thought okitoki. It can affect things particularly with glass. Glass isn't a solid and is one of the strongest known substances... except for the micro-cracks that happen the instant it's exposed to air as it cools. Those cracks are the reason why you should never wash a beer glass in detergent and why pubs have special cleaner for their glass washers. The detergent gets into the cracks and then kills the head on the beer.

            Maybe see if the milk thing happens in glazed china? (i.e. quality cups)
            One of my organic chemistry lecturers once explained that rinse aid alters the surface charge of some materials (to repel water if memory serves). That is why your glassware feels squeaky clean and why plastics sometimes feel greasy - also causes problems with the head on your beer. He also suggested that washing them in fabric softener (unscented) has the opposite effect.

            I don't think it will have the same effect on a metallic surface though.

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            • #21
              Just a thought.... are you purchasing your milk from the same shop?
              I have bought milk at my local IGA that still had 3 days until expiry and no sign of being off when cold but it curdled in the jug on steaming (still didn't smell when hot).
              I also know that a few years ago another IGA near to us used to turn off their fridges at night to save power!!! If you are getting it at the same shop then perhaps their fridges aren't doing their job or it's sitting out on delivery?

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              • #22
                Rinse-aid goes into the water, it doesn't coat the dishes - it encourages the rinsing water to form sheets rather than droplets and come off the dishes. Something would be wrong if residue was remaining on the dishes (you're right about certain plastics, they don't like it at all, or the harsh dishwasher detergents). It's a shame you don't have a second machine to try to nail down whether it's being caused by a contaminant in the coffee or in the milk/steam wand.

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                • #23
                  Hi Heks,
                  Certainly looks and sounds like curdling. As far as I know milk will curdle when acid levels are high and the rate of change will increase with increasing temperature. Most milk is standardised, which means the milk is filtered and or separated and put back together to obtain a standard ratio of fat and protein etc so you might not see much change across brands unless you pickup milk from one of the smaller suppliers that do not standardise (Gippy milk is one I can think of). This time of year in Australia we are just coming off the traditional Melbourne Cup day milk volume peak so milk is turning over very fast which I would think reduces the risk of off (high acid) milk getting through the supply chain but on the flip side a small disruption in the milk supply can cause a long backlog.

                  The fact that you get the problem across several milk brands including powder makes me think that the problem is elsewhere and you have also tried several types of beans. I am thinking the water (just to give you another tangent to explore).The pH levels also vary in the water supply but I can see that you have tried bottled water already. I can only think that you are getting increased acidity through your system or steam. Maybe try replacing all the water in your boiler with bottled water.

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                  • #24
                    Thx for the input everyone.
                    Today I tested the rinse aid option by using some brand new glasses which hadnt gone through the machine. Problem still happened. However only with the ordinary milk, the second coffee I made with longlife lactose free was ok, which suprised me because this has curdled before. Maybe just coincidence.

                    In answer to a previous question, no the milk doesnt curdle when left by itself. Only once it hits the coffee..and it seems to be the foam which hardens then starts coagulating.

                    Havnt tried powdered milk yet.

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                    • #25
                      I know it's been mentioned, but perhaps you've got some descaler in the boiler? What happens if you pour the milk into a shot of water from the group (instead of coffee)?

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                      • #26
                        Looks like curdling..

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                        • #27
                          As a matter of interest Heks, have you flushed the boiler with fresh water a couple of time, does fresh water run through the group and allowed to cool taste like clean fresh water?

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                          • #28
                            Originally posted by MrJack View Post
                            I know it's been mentioned, but perhaps you've got some descaler in the boiler? What happens if you pour the milk into a shot of water from the group (instead of coffee)?
                            Like MrJack, I'm suspecting it's the water from your machine's boiler. Alternatively if you don't want to waste any more milk for the milk in water test, find a pH test strip and test the pH of the water from the grouphead.

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                            • #29
                              [QUit TE=oble89;514850]Like MrJack, I'm suspecting it's the water from your machine's boiler. Alternatively if you don't want to waste any more milk for the milk in water test, find a pH test strip and test the pH of the water from the grouphead.[/QUOTE]

                              Yeh ive ordered some litmus paper. But the milk doesnt seperate if I steam it and then put it in a shot of water. Only if its in a shot of coffee. And ive tried qbout 4 different coffees now, both fresh grinds and supermarket.
                              Flushed the machine again thoroughly with bottled water, still no dice..
                              Tho I made 2 coffees yesterday which were fine, then today they were bad again..what a tease.

                              Is it possible this kind of problem be caused by some "tuning" problem with the machine? I feel like ive explored all possible chemical variables.

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                              • #30
                                I still think it is likely acid in your boiler water. Did a quick google, and would like to present my hypothesis

                                According to http://www.itisacqui.it/sitob/formagette/curdling.htm the micelles (small droplets of oil/fat with an outer layer of protein, suspended in water) become unstable at a pH around 4.6. When this happens, the protein molecules are attracted to, and get entangled in, each other (i.e.becoming curd).

                                I suspect your have water with a low pH, but not quite as low as 4.6. The addition of coffee, tips the pH over the edge, and curdling results. Its also possible that other molecules also play a part. Micelle stability is also related to concentration and temperature, so its possible that these factors come into play also.

                                You could probably investigate by performing a 'titration' with steamed milk and slowly adding (dropwise) some espresso.

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