[MUSIC] Welcome back. So, we're going to continue our conversation here about milk composition. We look at many of the milk components. What I want to do is to kind of step back a little bit and say what is all, how does this go through? What process does this go through? Going from the cow till ends up in the store where you might purchase the milk. So we'll start off with the cow, so here's cow. What's the body temperature of a cow temperature of a cow? The answer is, it's about 38 degrees centigrade or that's about 101 degrees Fahrenheit. Pretty warm, pretty warm. So right after it comes out of the cow, it goes into usually some sort of a holding tank or a refrigerated truck. So it's very quickly cooled to, basically 4 degrees C, which is about 39 degrees Fahrenheit, something like that. Shipped to the plant, the processing plant. And we'll call that raw milk. because it is raw milk at that point. It's not been processed in any way. Again, it's held at about 4 degrees C in that particular case. So, once it gets to the plant, one of the very first they will do is they are going to centrifuge it. And they're going to heat it up at this particular point to 60 degrees C, and that's about 140 degrees Fahrenheit, just to give you an idea. The reason they do that is because they want to separate the cream, and so what we have coming off here is of course the cream. And we have the skim. And, again, these are both very quickly refrigerated again back down to 4 degrees C. This is about 40% milk fat. So, pretty concentrated milk fat. This would then go to heavy whipping cream. So, if you whip cream, again, buy heavy whipping cream, that's basically what this is. And again, the skim is down here. Now, here's a kind of interesting part. What they do then is they take this, dilute it with some of the skim milk to about 12% fat. So again they take the heavy whipping cream, 40% fat dilute it with skim milk to get it down to 12% fat. And then this is what they use then to blend this back together to where they want to end up with the final product [COUGH]. This is the stuff that's homogenized. So, let's take a look at our first slide and see what homogenization is. So homogenization, again if you just have raw milk and you don't stir it, the cream will rise to the top. And you really don't want this. So what they do is they homogenize this 12% milk fat cream to prevent that cream from rising. And then they'll force that through a very narrow opening tubes, very high pressures, and that breaks up those milk fat globules into much smaller ones. Then you need the proper ratio of the milk protein, that's part of why they dilute it down to 12% with the skim milk. Milk protein fat ratio so that there's protein covering these smaller droplets so they do not then re-form into larger droplets. And so there basically becomes a stable emulsion at that point, in these smaller droplets. So let's go to the next slide. And so again, this is diluted whole milk, we've seen this before when we looked at the milk fat video, and each one of these dots is a milk fat globule. This is two percent milk and it's just loaded with these smaller, this has been homogenized. So this is much, much smaller droplets. Again that they've been broken down or made into these smaller droplets, coated with the milk protein. And so it's a much more stable emulsion. So let's get rid of that slide and see where we go next. Yeah, this is homogenized. So now at this point what they're going to do is, again we've got 12% fat and you've got fat free milk. So if you want whole milk, 3.25, 3.5% milk, 2% milk, milk fat, 1% milk fat, what you're going to do is blend those back together. So we call those kind of standardized milk, milk. So again, these things go in together. So you're going to blend those together to get whatever percentage you want. 2% milk, the one I just showed you a moment ago. And so on and so forth. This is the stuff that's then pasteurized. So let's go to our next slide and kind of take a quick look at pasteurization. What does that mean? Pasteurization is a time temperature relationship in terms of how we think about this. There you can see there are actually three, there's actually several different types of time temperature combinations that people have used. Low temperature 15 seconds at 72 degrees C, that's about 162 degrees Farenheit. There's another similar one, a low temperature 15 seconds at 75 degrees C. For homogenized milk, high temperature, 15 seconds at 85 degree C. That's 185 degrees Fahrenheit. And then something called UHT or Ultra High Temperature pasteurization, 2 seconds, one, two in 140 degrees centigrade or three seconds. One, one thousand, two, one thousand, three, one thousand and that's as fast as it goes at about 135 degrees centigrade. And again, it gives you an idea that 140 degrees centigrade is about 284 degrees Fahrenheit. Organic milk that you might buy in the store has been UHT pasteurized. And that's why the shelf life is a little bit longer for organic milk, that's just part of the process of making the organic milk. Next slide gives us an idea why, why we would do this. First of all pasteurization kills most of the bacteria, now the key is it doesn't kill all the bacteria, but it certainly kills the pathogenic bacteria that might harm us. There are still some bacteria that are left in there and those are the ones that ultimately down the road even if it's refrigerated will ultimately spoil milk that's why milk doesn't last forever. Certainly the UHT milk actually last for quite a long time if it's not opened. Could be packaged and stored at room temperature for a very, very long time. Again as long as its not exposed to the environment. Pasteurization also inactivates some enzymes. Enzymes that might be generated from bacteria that are in the milk, also enzymes that are already in the milk. So as soon as that milk is being produced in the cow, it's already starting to break down. Their enzyme, enzymes already in the milk. They are starting to break down some of the proteins, some of the fats, and so on and so forth. And so pasteurization helps to minimize the activity of those enzymes in activating. Those enzymes that are end up that milk. Pasteurization also normally ensures the safety and enhances the shelf life of the milk so this is really an important process in terms of shelf life of milk. You might recall in one of the earlier videos, we talked about how perishable milk is and so pasteurization's are really key component to why it is we can store milk as long as we can. This then, is then packaged and of course then shipped to the store. The total process from the time it leaves the cow until it ends up in the store is often times only about two days. Very, very fast. Might be sometimes a third day but usually it's only two days going through this whole process. So let's take a look at this packaged milk here for a moment, because there's some many times if you go to the store to buy milk you're going to find a date on the milk. So let's take a look at some dates. Take a look at the slide here that kind of summarizes. This is how USDA defines these dates. So the sell-by date which is usually what you find on milk, tells the store, not you but the store, how long to display that product for sale. So if it gets up to the sell by date, and it's rare that milk in a store is going to get to that point, then they have to remove that milk and it's no longer for sale. Best if used by or before date is recommended for best quality or best flavor. It's not a purchase or a safety date, it's just this is the best quality. And so again, some products you might find will have a best by or a best if used by date, or a best if used before date. And then the Use-By date is the last date recommended for the product while at peak quality. So it doesn't mean it's necessarily bad afterwards, but peak quality, this is usually determined by the manufacturer of the product. Now the sell by date here at the top, typically even if you buy milk, if it's refrigerated and you keep it sealed, it's probably still good for another five to seven days beyond that sell by date. And usually the sell by date is a couple weeks. In fact typically, when milk leaves the plant, processing plant, if everything's working correctly and it's refrigerated and stored correctly, a good 17 days it'll usually still be very, very high quality at that point. So you can get a lot of shelf life out of even fluid milk. If it's stored properly and handled properly. And so what I want to do is very quickly review what we've talked about here. Again we've kind of gone from the cow down to where it's going to end up in the store. Coming out of the cow, it has to be cooled very rapidly and except for this particular step here, most of these other steps, it's continued to be kept at a fairly cool temperature. Four degree C. Again we have homogenization where we're separating the creams from the skim. We've seen that in some of the other videos. We've talked about milk fractions, heavy whipping cream would be coming off this line right here. It's again at 33 to 40% milk fat, something like that. And then we again have the skim milk. But then, what they do is actually dilute this. This, having whipping cream with the skim milk to get down to 12% fat. That's what you actually homogenize. And then those are put back together, blended back together to give you your 1% milk fat, 2% milk fat and whole milk. And then that's the material that's actually pasteurized. And then packaged, and then that gets to the store. So hopefully this gives you a quick overview of kind of, how it goes from the cow to you purchase in the store. What happens, the very general steps that are happening in between and gives you a little bit of a timeline on how that process occurs.
